food production notes
COCOA..
The cocoa tree (Theobroma cacao) is a native of the dense tropical forests of the Amazon. The term “Theobroma” means “food of the Gods”. The word cocoa has originated from the Aztec word “Cacahuati”. Cocoadescribes the bulk commercially dried, fermented beans, as well as powder from cocoa beans. The main procedures and exporters of the cocoa bean are West Africa (74% of the world production), North, Central and South Africa (21%) and Asia and Australia (3%). However the processing of the bean into chocolate is done in several other countries and some of the best chocolate is produced in Belgium,Switzerland and France.
The Cocoa Plant
The cocoa plant is a small tropical tree, originally grown in South and Central America; but now commercially grown in West Africa. The cocoa tree requires a good soil, a huge rainfall and a low altitude. The part of the plant that is processed and used for the making of cocoa and chocolate is the fruit that grows on the main trunk of the tree, as well as on the branches. The fruit is a large pod 4“ to 12“ in length and about 4“in diameter and has a hard leathery rind containing 25-75 seeds in distinct rows, embedded in a soft pulp.
Classification
Cocoa may be classified under the following headings:
1. By the country of origin (Zambia/Mozambique).
2. By the species of the bean (Criollo/Forastero).
3. By the method of manufacture (For drinking chocolate/for milk chocolate).
4. By their particular use (Vending machines/Icings/Chocolate moulding).
Processing of Cocoa
The processing of cocoa bean into cocoa powder is done in seven stages, as mentioned under:
1. Fermentation of the Beans
The ripe cocoa pods are collected and split open and the beans and the pulp surrounding them are scooped out and put into a fermentation chamber, also called the sweat boxes, where the temperature is allowed to rise to 40 to 50°C (104 to 122°F). Fermentation will kill the germs and prevent germination and decomposition of the bean. It will also encourage enzyme reaction reducing the bitterness and developing flavour. The beans absorb the liquid from the fermenting sugary pulp which will then turn into alcohol and finally into acetic acid. As soon as the mass turns into the acid state, the fermentation is stopped. Otherwise unpleasant flavours and odours will develop.
The ripe cocoa pods are collected and split open and the beans and the pulp surrounding them are scooped out and put into a fermentation chamber, also called the sweat boxes, where the temperature is allowed to rise to 40 to 50°C (104 to 122°F). Fermentation will kill the germs and prevent germination and decomposition of the bean. It will also encourage enzyme reaction reducing the bitterness and developing flavour. The beans absorb the liquid from the fermenting sugary pulp which will then turn into alcohol and finally into acetic acid. As soon as the mass turns into the acid state, the fermentation is stopped. Otherwise unpleasant flavours and odours will develop.
2. Drying of the Beans
This is done by laying the beans thinly out in the Sun to dry and occasionally turning them over, or by passing them through a mechanical drying chamber. When completely dried, there will not be more than 4% moisture in the bean. At this stage, beans are exported, unless they are to be processed into cocoa chocolate.
This is done by laying the beans thinly out in the Sun to dry and occasionally turning them over, or by passing them through a mechanical drying chamber. When completely dried, there will not be more than 4% moisture in the bean. At this stage, beans are exported, unless they are to be processed into cocoa chocolate.
3. Roasting the Beans
This stage is essential to develop the flavour and the aroma of the bean and to give colour. Moisture is lost at the stage, which assists in the removal of the shell from the beans.
This stage is essential to develop the flavour and the aroma of the bean and to give colour. Moisture is lost at the stage, which assists in the removal of the shell from the beans.
4. Removing the Shell
This stage is also called “Winnowing”. The shell is removed from the bean by passing them through a series of rollers and sieves. The de-shelled beans, now mostly broken bits and pieces, are referred to as “Nibs”.
This stage is also called “Winnowing”. The shell is removed from the bean by passing them through a series of rollers and sieves. The de-shelled beans, now mostly broken bits and pieces, are referred to as “Nibs”.
5. Alkalization of the Nibs (Dutch Processing)
This stage, that further develops the flavour and colour, is usually done by tumbling the nibs in an alkali solution. After drying, the nibs may be roasted to correct the moisture content.
This stage, that further develops the flavour and colour, is usually done by tumbling the nibs in an alkali solution. After drying, the nibs may be roasted to correct the moisture content.
6. Grinding the nibs
The nibs are now ground into very small particles, a process which releases a large amount of fat and results in the mass becoming a thick syrup. This fat is known as “Cocoa Butter”, usually 50% of the nibs.
The nibs are now ground into very small particles, a process which releases a large amount of fat and results in the mass becoming a thick syrup. This fat is known as “Cocoa Butter”, usually 50% of the nibs.
7. Extraction of the Cocoa Butter
The cocoa fluid/mass is then fed into large felt lined steel pans fitted with a movable perforated lid. When subjected to hydraulic pressure, some of the fat is forced through the filter cloths, leaving behind a solid residue, known as the “Press Cake”. This is removed from the pan, allowed to cool, then pulverized and sieved. TO this fine powder, a small amount of salt and vanilla is usually added before it is marketed as the popular cocoa powder.
The cocoa fluid/mass is then fed into large felt lined steel pans fitted with a movable perforated lid. When subjected to hydraulic pressure, some of the fat is forced through the filter cloths, leaving behind a solid residue, known as the “Press Cake”. This is removed from the pan, allowed to cool, then pulverized and sieved. TO this fine powder, a small amount of salt and vanilla is usually added before it is marketed as the popular cocoa powder.
Plain Chocolate
The processing of chocolate involves the first six stages as for the processing of cocoa and then a further three stages:
1. Mixing the Cocoa mass with sugar
The cocoa mass is thoroughly mixed with powdered sugar in large blending kettles. The fat content is strictly controlled to obtain a standard product. Additional cocoa butter may be added to adjust the consistency.
The cocoa mass is thoroughly mixed with powdered sugar in large blending kettles. The fat content is strictly controlled to obtain a standard product. Additional cocoa butter may be added to adjust the consistency.
2. Refining the mixture
This is done by passing the mixture through a series of five heavy rollers to reduce the size of the non-fat particles, so that the chocolate will be smooth to the palate. This stage exposes the particles to the air, reducing the moisture content, partially evaporating volatile substances, and lightening the colour of the mixture.
This is done by passing the mixture through a series of five heavy rollers to reduce the size of the non-fat particles, so that the chocolate will be smooth to the palate. This stage exposes the particles to the air, reducing the moisture content, partially evaporating volatile substances, and lightening the colour of the mixture.
3. Conching
The final stage is concerned with producing a standard quality of chocolate. Conching is the mechanical agitation of the chocolate mass with additional cocoa butter at a temperature of 60-70°C (140-158°F). This will further evaporate volatile substances and also develop the flavour. Additional flavourings may also be added at this stage and the mixture is standardized. The chocolate is then set in moulds such as bars, slabs and is also known as courverture.
The final stage is concerned with producing a standard quality of chocolate. Conching is the mechanical agitation of the chocolate mass with additional cocoa butter at a temperature of 60-70°C (140-158°F). This will further evaporate volatile substances and also develop the flavour. Additional flavourings may also be added at this stage and the mixture is standardized. The chocolate is then set in moulds such as bars, slabs and is also known as courverture.
A chocolate in block has a tendency to collect moisture from the air and this can be seen in the form of beads of perspiration. This could be wiped carefully and well scraped before being used for dipping.
Milk Chocolate
The processing of milk chocolate is the same as Plain Chocolate(courverture), except that milk crumb is added at the refining stage and the conching is done at a lower temperature, but for a longer time. Milk crumb is a mixture of condensed milk and chocolate mass, reduced to a powder form.
Cocoa Powder
It is a product obtained by grinding roasted cocoa beans to an oily liquid, pressing this in a cocoa-butter press, to remove about half cocoa butter and then grinding the residual press cake to a powder. Chocolate powderis a blend of true cocoa powder, sugar and starch.
Drinking Chocolate
It is a modern beverage drink, prepared from the chocolate powder or chocolate flakes and made in similar manner to the cocoa drink, by adding hot water or milk.
White Chocolate
It is a product composed of pure cocoa butter, full of cream milk powder and sugar, milled together and passed through refining rolls. As pure cocoa butter has a strong taste and odour of chocolate, the product is similar in flavour to chocolate. It can be tempered and molded. Provided fat-soluble edible colours are used, white chocolate can be coloured pink, orange, yellow or green.
Chocolate Spread
It is permanently soft, pasty or semi-liquid product, which can be used in bakery as flavouring and colouring material for fillings, butter creams and fondants. To make it, add warmed golden syrup to melted chocolate courverture in the proportion of two parts of syrup to one part of courverture, mixing them thoroughly and adding the warm syrup into glass or glazed earthen ware jars and kept for use as needed.
Panache
It is the name given to a blend of chocolate and cream. Boiling fresh cream is mixed with grated or melted courverture and stirred occasionally till cooled.
Composition of Cocoa and Chocolate
Theobromine is the stimulant in cocoa and chocolate, along with somecaffeine. The other major constituents of cocoa and chocolate include colour and flavour compounds, lipids and carbohydrate. The purple colour is due to the presence of anthocyanins. The chocolate flavour is contributed by the phenolic compounds.
Starch is the chief carbohydrate in cocoa and chocolate and functions as a thickening agent. Cocoa contains 11% starch while chocolate contains 8%. Cocoa has more thickening power than chocolate because of its high starch content. For this very reason, cocoa is not substituted on a direct weight basis for chocolate. Usually 3-3.5 tablespoon of cocoa powder plus ½ table spoon of fat are considered equivalent to 30 Gms of chocolate.
Fat constituent of cocoa and chocolate is cocoa butter. Cocoa varies in fat content from 10-22%. Chocolate contains 50% fat. The low melting temperature of chocolate (near 32°C) imparts a smooth texture and readily releases flavour components.
Uses of Chocolate
Cocoa powder and Chocolate powder are used:
1. As a hot beverage.
2. AS a flavouring agent.
3. As a colouring agent.
4. For hot and cold sauces.
Courverture is used:
1. As a coating.
2. As a decoration (Piping).
3. Formoulding into Easter eggs etc.
4. For sauces.
5. For ice-creams.
Storage
Cocoa and chocolate deteriorate quickly in the presence of moisture and heat. Cocoa becomes grayish in colour and lumpy when stored at temperature above 16-21°C and in high humidity.
A mottled or grey surface known as bloom may develop on the chocolate when it is exposed to high heat and moisture. The melting fat and re-crystallizing in a different pattern on the surface contribute to the formation of bloom.
Appropriate tempering procedures during processing and the use of stabilizers retards the development of bloom. Sugar bloom, a rough greyish layer, may develop on sweet chocolate due to moisture; the dissolved sugar re-crystallizes on the surface.
The chocolate flavour appears not to be altered by the development of bloom or lumping of cocoa products, but the texture may be grainy. Milk chocolates also absorb flavours and odours when stored improperly. The quality of cocoa and chocolate is best when high temperature and humidity is avoided. The best protection is tightly sealed containers kept in a cool, dry place.
Nutritional Aspect
Cocoa powder and milk chocolate are rich in fats and carbohydrates. Being a highly palatable and energy concentrated food, it was used extensively in emergency situations such as wars and during rescue and evacuation situations.
Chocolate Tempering
Chocolate tempering is a process used to prepare pure chocolate liquor for cooking purposes. During tempering, it is essential that not one drop of water should come into contact with the chocolate
Procedure
Break chocolate into small pieces and place it in a bowl over hot water. Stir occasionally until it is melted and the temperature is 46-48°C If this temperature is exceeded, the chocolate is ruined.
Remove the bowl from saucepan and set in iced water, stirring carefully until the chocolate begins to set on the bottom. Then warm the chocolate carefully over hot water until the temperature is dark chocolate to 31°C, in milk chocolate to 29°C and in white chocolate to 29°C. If the temperatures are exceeded, the tempering process should begin again.
It is only necessary to temper chocolate when using it for moulding or dipping. For any fillings, pure chocolate or cooking chocolate can be used without tempering.
Butter is the fat of cream that is separated – more or less – completely from the other milk constituents by agitation or churning. The mechanical rupture of the protein film around the fat globules allows the fat globules to clump together. Butter formation is an example of breaking of an oil-in-water emulsion by agitation. The resulting emulsion that forms in butter itself is a water-in-oil emulsion, with about 18% water being dispersed in 80% fat and a small amount of protein acting as an emulsifier.
Butter is made from either sweet or sour cream. Butter from sour cream has a more pronounced flavour. The cream may be allowed to sour naturally or may be acidified by the addition of pure culture of lactic acid bacteria to sweet cream, which produces a butter of better flavour and keeping quality.
It consists of more than 80% butterfat and small amounts of protein, vitamin A and D, minerals, lactose and water. Butter must have a minimum of 80% fat content, a non-fat solid content of 2% and a maximum of 16% moisture (water).
Composition
Average composition of Butter
| |
Fat
|
82.5%
|
Protein (Casein)
|
1.5%
|
Lactose
|
2%
|
Salt
|
2%
|
Water
|
12%
|
Factors that affect quality of Butter
1. The breed of animal (cow or buffalo) from which the milk was obtained.
2. The type of feed that was available for the animal.
3. The method of manufacture (fresh or ripened cream).
4. The efficiency of manufacture (wrong temperature may affect the colour and flavour of butter).
5. Whether or not the butter was blended.
6. The addition of salt and colour.
7. The method of packing and storing.
Classification of Butter
There are four main types of butter:
1. Fresh or Sweet cream Butter,
2. Ripened cream or Lactic Butter,
3. Blended or Milled Butter and
4. Special Butter
(Fresh and ripened cream Butters are known as “Creamery Butters”).
Manufacture of Creamery Butter
The manufacture of creamery butter takes place in four main stages, as mentioned:
1. Holding
The cream (35%) is pasteurized at 95°C (203°F) and held for 2 to 4 seconds. It is then cooled to 4.5°C (40°F) and held there for several hours to ensure the uniform hardening of the fat globules.
The cream (35%) is pasteurized at 95°C (203°F) and held for 2 to 4 seconds. It is then cooled to 4.5°C (40°F) and held there for several hours to ensure the uniform hardening of the fat globules.
2. Ripening
When the end product is going to be a ripened butter or lactic butter, a “starter” (which is a laboratory culture of acid-producing bacteria) will be added during the Holding stage, in which the holding temperature will be 15.5-18.5°C (60-65°F) for 3 to 4 hours before being cooled to 4.5°C (40°F). This gives the butter a much fuller flavour. However, the flavour tends to fade and therefore the ripened cream butter has a shorter life than the sweet cream butters. This stage will be omitted when making the sweet cream butter.
When the end product is going to be a ripened butter or lactic butter, a “starter” (which is a laboratory culture of acid-producing bacteria) will be added during the Holding stage, in which the holding temperature will be 15.5-18.5°C (60-65°F) for 3 to 4 hours before being cooled to 4.5°C (40°F). This gives the butter a much fuller flavour. However, the flavour tends to fade and therefore the ripened cream butter has a shorter life than the sweet cream butters. This stage will be omitted when making the sweet cream butter.
3. Churning
The churning of cream is done in large stainless steel churns that hold about 1000 gallons of cream. The temperature must not exceed more than 4°C. The churns are rotated while internal rollers pass through the cream. This breaks the envelope of non-fat particles/solids that surround the small fat globules and coalesce to form larger groups of butter fat. The envelope is dispersed in the thin liquid part of the cream to form buttermilk. After about 30 minutes of churning, the butter separates out in the form of grains and floats in the buttermilk. The buttermilk is carefully drained away and used for other purposes.
The churning of cream is done in large stainless steel churns that hold about 1000 gallons of cream. The temperature must not exceed more than 4°C. The churns are rotated while internal rollers pass through the cream. This breaks the envelope of non-fat particles/solids that surround the small fat globules and coalesce to form larger groups of butter fat. The envelope is dispersed in the thin liquid part of the cream to form buttermilk. After about 30 minutes of churning, the butter separates out in the form of grains and floats in the buttermilk. The buttermilk is carefully drained away and used for other purposes.
4. Washing and Salting
The butter grains are now washed with ice water to remove any traces of buttermilk left on the surface of each grain, in order to maximize the keeping quality. Ice water also helps to harden butter grains. Salting can be done in two ways:
The butter grains are now washed with ice water to remove any traces of buttermilk left on the surface of each grain, in order to maximize the keeping quality. Ice water also helps to harden butter grains. Salting can be done in two ways:
a. By adding fine grains of dairy salt, and
b. By soaking in a brine solution for 10-15 minutes and allowing the butter to absorb it.
The quantity of salt added usually average 1% for ripened cream butter and 1.5% for fresh cream butter. Salt contributes to flavour and improves the keeping quality.
The butter grains are then worked into a smooth solid mass by rotating the churns slowly for 10-15 minutes, then weighed and packed. Colouring (annatto) may also be added at this stage. If unsalted butter is required, the salting stage is omitted.
Blended Butter
Blended butter is a blend of butters from different regions or countries. These are mixed together to produce a product of standard quality at a competitive price, under a brand name.
Special Butters
This group includes some butter that are not commonly available and those which are not true butters. These include:
1. Whey Butter
Whey is the liquid which separates from the curd while making cheese. The butterfat obtained from the whey may be used to produce butter, or it may be added to fresh cream/milk prior to it being processed into butter. Due to its origin, this butter has a faint cheesy flavour.
Whey is the liquid which separates from the curd while making cheese. The butterfat obtained from the whey may be used to produce butter, or it may be added to fresh cream/milk prior to it being processed into butter. Due to its origin, this butter has a faint cheesy flavour.
2. Milk blended Butter
Quantities of milk are blended into butter, thereby increasing the moisture content to 24% (max.).
Quantities of milk are blended into butter, thereby increasing the moisture content to 24% (max.).
3. Powdered Butter
This is spray-dried butter containing 80% milk fat and non-fatty solids. It is produced on a large scale in Australia and is used mainly in the Bakery trade.
This is spray-dried butter containing 80% milk fat and non-fatty solids. It is produced on a large scale in Australia and is used mainly in the Bakery trade.
4. Compound Butters
These are made by adding a particular natural flavour or colour to butter, depending on the type of food with which it is served. It is generally used as an accompaniment e.g. Lobster Butter, Parsley Butter etc.
These are made by adding a particular natural flavour or colour to butter, depending on the type of food with which it is served. It is generally used as an accompaniment e.g. Lobster Butter, Parsley Butter etc.
5. Cocoa Butter
This is not a true butter, rather obtained by crushing the cocoa beans. It is the most expensive ingredient used in chocolate making. Cocoa butter substitutes, using palm oil, are also available.
This is not a true butter, rather obtained by crushing the cocoa beans. It is the most expensive ingredient used in chocolate making. Cocoa butter substitutes, using palm oil, are also available.
6. Peanut Butter
It is a paste-like substance obtained by grinding roasted peanuts that may be further emulsified and flavoured.
It is a paste-like substance obtained by grinding roasted peanuts that may be further emulsified and flavoured.
Uses of Butter
1. As a spread for bread, toast and scones.
2. As a basic ingredient in pastry-making and cake-making.
3. Used as an accompaniment (compound butter).
4. To enhance the taste and flavour of soups and sauces.
5. As a cooking medium (The smoke point of butter fat is only 127-130°C; so a vegetable oil should be used when high cooking temperatures are required).
6. For butter sculptures.
Butter is available in 10 Gms, 100 Gms and 500 Gms packs in the market.
Storage
Butter is a perishable product and tends to loose flavour and go rancid on prolonged storage. Exposure to sunlight can make it go rancid faster.
It must be stored at refrigerated temperatures (2°C), well wrapped and away from strong flavoured foods, for it absorbs odours and flavours easily. If purchased in bulk, it can be frozen at -25 to -35°C.
A good quality butter should have a clean flavour and aroma characteristic of the type of butter, have a close body, a waxy texture, be of uniform colour, have a uniform distribution of salt (if added), be clean in appearance and have an absence of any free moisture.
Ghee is obtained by clarifying butter. Butter is heated to evaporate water. Pure ghee has a higher keeping quality and is a good cooking medium and a shortening agent used in Indian Cuisine.
Cream is the fat separated from milk. It is the lighter portion of milk containing all the main constituents of milk, but in which fat content is high and the solid (non fat) content is lower.
Cream is commercially separated from milk in a creamery, by means of a mechanical separator. The milk is first heated to between 32-49°C (90-120°F) before being run into the separator which operates like centrifugal machine, rotating at very high speed and forcing the milk, which is heavier, to the outside; while the cream, which is lighter, remains at the centre. The cream and the skimmed milk are drained out through separate outlets and by means of a control valve, the fat content is adjusted. The skimmed milk is then heated to 79.5°C (175°F) to kill off any harmful bacteria before being further processed into dried milk etc.
Types of Cream
There are a variety of creams available in the market, each having a different fat content:
Type of Cream
|
Fat Content
|
Single Cream
|
18%
|
Whipping Cream
|
35%
|
Double Cream
|
48%
|
Double Thick Cream
|
50%
|
Sterilized Half Cream
|
12%
|
Sterilized Cream
|
23%
|
Clotted Cream
|
55%
|
For general purposes, cream may be classified into:
1. Whipping Cream (>30% fat).
2. Light or Coffee Cream (18% fat).
3. Half-and-half (10.5% fat).
4. Non-dairy or Manufactured Cream.
Half-and-half is a mixture of milk and light cream and it may be used in place of coffee cream. Cream containing sugar, stabilizers and flavouring is sold in pressurized containers. Non-dairy products containing water, vegetable fat, sugar, sodium caseinate, emulsifiers and vegetable gums are also available in pressurized cans. Nondairy products for whipped toppings, coffee, whiteners and snack dip bases are also available in the market.
Manufactured Cream
1. Reconstituted Cream
It is made by emulsifying butter with skimmed milk or skimmed milk powder. This is not true cream, but a substance which resembles it in appearance.
It is made by emulsifying butter with skimmed milk or skimmed milk powder. This is not true cream, but a substance which resembles it in appearance.
2. Imitation or Synthetic Cream
It is made by the emulsification of vegetable fats with dried egg and gelatin, and then sugar and flavourings are added. It is a product which is frequently used in catering and baking trade, but which is very easily contaminated and liable to cause food-poisoning.
It is made by the emulsification of vegetable fats with dried egg and gelatin, and then sugar and flavourings are added. It is a product which is frequently used in catering and baking trade, but which is very easily contaminated and liable to cause food-poisoning.
Uses of Cream
1. To serve with hot or cold coffee and chocolate.
2. To serve as an accompaniment (fruit based salad).
3. To be used fro decorative purposes in cakes and gateaux and for garnishes in soups and desserts.
4. As a main ingredient in certain desserts such as ice-cream and custards.
Storage of Cream
Fresh cream must be treated in the same way as fresh milk, as far as storage is concerned. Whipped cream must be covered and stored in sterilized containers in the refrigerator and used in the same day. Reconstituted and intimation cream must be refrigerated and only small quantities be whipped, when required for immediate use.
The whipping of Cream
Whipping cream is a product that results from the agitation of cream. During whipping, air is incorporated, thus forming foam, and fat particles are clumped together, producing the characteristic stiffness or rigidity of whipped cream. If whipping is continued too long, the emulsion breaks and butter gets separated. The air bubbles formed in whipped cream are surrounded by protein films in which clumps of fat globules offer structural support, which increases the rigidity of the foam and permits the formation of more air bubbles and the extension of the protein film to surround them. Homogenized cream is not suitable for whipping.
Points to be considered while whipping Cream
1. Use cream with minimum 30% fat for ease in whipping and for a stiff product. Increased fat upto 38% improves the whipping quality of cream.
2. Hold cream at low temperature (7°C) whips well. Lower temperature increases viscosity, which increases the whipping property. The beater and the bowl used should be cold.
3. Whipping property improves with the aging of cream, as viscosity increases.
4. Homogenized cream will not whip satisfactorily. When whipping cream, tiny air bubbles are trapped and surrounded by the fat globules in the cream. Homogenized cream will have had the majority of the fat globules broken down and they will not be sufficient and strong enough to trap and hold the air cells.
5. The utensils must be sterilized. Glass or stainless steel containers are ideal for whipping cream. Avoid using aluminum as it tends to discolour the cream, turning it a dull grey.
6. Increased acidity upto the concentration required to give a sour taste (0.3%) has no effect on whipping quality.
7. Addition of sugar decreases both volume and stiffness and increases time required to whip cream if it is added before whipping. If sugar is to be added, it is best added after the cream is stiff or just before service.
We consume the eggs of birds like consume the eggs of birds like hen, goose, turkey, fowls etc. The eggs of only those birds whose meat is eaten are used for cooking purposes. But in India, eggs of hen and ducks are used. Eggs serve a versatile and basic function in diet and in food preparation. They are a pre-packaged container of nutrients in their own disposable shell.
Grading of eggs
(U.S. weight classes for eggs, minimum weight per dozen for each size)
Jumbo
|
Extra large
|
Large
|
Medium
|
Small
|
Peewee
|
30 oz/
|
75 Gms/egg
(900 Gms per dozen)27oz/
68.5 Gms/egg
(810 Gms per dozen)24oz/
60 Gms/egg
(720 Gms per dozen)21oz/
52.5 Gms/egg
(630 Gms per dozen)18oz/
45 Gms/egg
(540 Gms per dozen)15oz/
37.5 Gms/egg
(450 Gms per dozen)
N.B.:1 oz=30 Gms approx.
Structure of eggs
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Structure of an Egg
The egg is composed of shell, white and yolk. The egg white forms 2/3rdof the whole egg and the yolk forms 1/3rd.
1. Shell
It is the outer hard covering of the egg and is made up of Calcium,Magnesium carbonate and Calcium phosphate. The shell gives shape to the egg and holds the inner contents. The shell contains thousands of pores that allow CO2 and moisture to escape, as well as air to enter. The shell is covered by a cuticle membrane or Bloom and should not be washed. The bloom acts as protective covering blocking the pores, and prevents moisture loss and bacterial contamination. When eggs are washed before going to the market, the cuticle is removed. To protect the egg, the washed eggs are coated with a thin film of edible oil.
It is the outer hard covering of the egg and is made up of Calcium,Magnesium carbonate and Calcium phosphate. The shell gives shape to the egg and holds the inner contents. The shell contains thousands of pores that allow CO2 and moisture to escape, as well as air to enter. The shell is covered by a cuticle membrane or Bloom and should not be washed. The bloom acts as protective covering blocking the pores, and prevents moisture loss and bacterial contamination. When eggs are washed before going to the market, the cuticle is removed. To protect the egg, the washed eggs are coated with a thin film of edible oil.
2. Membrane
Beneath the shell, there are two semi permeable membranes – the outer and the inner. These membranes act as a protective layer in case the shell cracks.
Beneath the shell, there are two semi permeable membranes – the outer and the inner. These membranes act as a protective layer in case the shell cracks.
3. Air cell
On one side of the egg (broader), both these membranes separate to form an air cell. This is formed by contraction of the contents as soon as the egg is laid, due to the difference in the outside temperature.
On one side of the egg (broader), both these membranes separate to form an air cell. This is formed by contraction of the contents as soon as the egg is laid, due to the difference in the outside temperature.
4. Egg white
It has 1/8th part of the protein, which is called albumin; the remaining being water. The egg white consists of three parts – the outer thin albumen, the middle thick albumin and the inner thin albumin.
It has 1/8th part of the protein, which is called albumin; the remaining being water. The egg white consists of three parts – the outer thin albumen, the middle thick albumin and the inner thin albumin.
5. Egg yolk
The yolk is separated from the white by a membrane called vitelline membrane. This membrane prevents the mix of both yolk and white. 1/6th parts of the egg yolk contains proteins, 1/3rd fat and the rest water, Vitamins and minerals like Calcium, Phosphorus, Iron etc.
The yolk is separated from the white by a membrane called vitelline membrane. This membrane prevents the mix of both yolk and white. 1/6th parts of the egg yolk contains proteins, 1/3rd fat and the rest water, Vitamins and minerals like Calcium, Phosphorus, Iron etc.
6. Chalaza
The egg is kept in position at the centre of the egg with the help of the chalaza. It has a thick-cord like appearance and is composed of proteins. This chord-like structure may have to be strained while making custards.
The egg is kept in position at the centre of the egg with the help of the chalaza. It has a thick-cord like appearance and is composed of proteins. This chord-like structure may have to be strained while making custards.
Composition of an Egg
Parts
|
Number
|
Weight
|
H2O
|
Proteins
|
Fats
|
Whole egg
|
1
|
50 Gms
|
74%
|
13%
|
12%
|
Egg white
|
1
|
33 Gms
|
88%
|
11%
|
Traces
|
Egg yolk
|
1
|
17 Gms
|
51%
|
16%
|
31%
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Selection of Eggs+
Colour
The Colour has no direct effect on the quality of the egg. It depends on the breed, the type of bird and the food consumed. However avoid any eggs with patches formed on the surface as they indicate deterioration of eggs.
Size and Weight
It again depends on the type of bird. An average hen’s egg weighs around 50 gms. The weight should be proportional to the size of the egg. If the size is big and the weight is less, the air cell is big, which indicates that the egg is old.
Egg white
It should not be watery but firm. Firm albumen is a sign of freshness.
Egg yolk
Its colour again depends on the type & feed of the bird. The pigment contained is different feeds are different. Birds that feed on green grass or yellow corn will have a dark yellow colour because of the carotinoidspresent in the grass. However, avoid eggs which have blood spots (meat spots). The blood spot means that the egg is fertilized and nearing hatching (the blood spots caused by the rupture of a blood vessel during egg formation).
Approximately 1% of all eggs will have these spots which are detected and removed during grading. Electronic blood detectors are sometimes used for grading. Although the blood spot may be objectionable to the consumer, the eggs are chemically and nutritionally fit to eat. In fact, the blood spot is an indicator that the egg is fresh. As the egg ages, the yolk removes H2O from the albumen and dilutes the blood spot.
Free from cracks
The egg must be free from cracks. If the egg is cracked, there are chances that the egg is spoilt, since the micro-organisms have an easy access into the egg.
Flavour and Odour
Generally the eggs don’t have any odour from the outside, except that of the packing material, which must not be strong smelling. Sometimes the smell may penetrate into the egg. Hence, eggs are usually stored away from strong flavoured foods like fish, onions, garlic etc.
In order to maintain the standard, size, quality, colour and weight, the distributors buy eggs, usually from on-farm only, where the diet is kept constant.
If the birds are of the same breed and feed, the standard can be maintained.
Test for freshness
There are two basic tests for judging the freshness of an egg externally i.e. without breaking, as stated under:
1. Water treatment
When egg is placed in water and if it floats, then it is stale. If it sinks completely, it is good. If it floats half-way, then the egg is neither too fresh, nor stale. The air cell increases in size as the eggs get older, which results in floating of eggs.
When egg is placed in water and if it floats, then it is stale. If it sinks completely, it is good. If it floats half-way, then the egg is neither too fresh, nor stale. The air cell increases in size as the eggs get older, which results in floating of eggs.
2. Candling
Egg is placed in a dark room before a candle to see the yolk, white and the presence of blood spots, etc. Now a day, most eggs are graded by passing down on roller over high intensity lights. The eggs are rotated as they move on rollers, so that all parts are visible.
Egg is placed in a dark room before a candle to see the yolk, white and the presence of blood spots, etc. Now a day, most eggs are graded by passing down on roller over high intensity lights. The eggs are rotated as they move on rollers, so that all parts are visible.
Reasons for storage of eggs
1. As soon as the eggs are laid, they start deteriorating as they come in contact with the atmosphere.
2. The dense albumen becomes thin and watery.
3. Water from the white passes through the yolk; thus lowering its solids as the vitelline membrane is weakened. Chalaza starts to disintegrate and no longer holds the yolk in the centre.
4. If exposed to air, the moisture evaporates and the air cell increases in size.
5. The egg may absorb off-odours, shell being porous.
6. Fresh yolk is slightly acidic, whereas white is alkaline. Loss of carbon dioxide from the egg results in deterioration.
Storage of eggs
Care must be taken in handling and storage of the eggs. They should be stored in their packing trays with the blunt end upwards and the temperature of 7-13°C, at a relative humidity of 70-80%. This way, it can be kept for a month. It should be kept away from onions, garlic, fish etc. Frozen eggs are stored at -18°C. When defrosted, it should be used in the same day.
Dried eggs stay upto one year, if kept unopened in the original container in a cold dry store room. Once opened, it should be used as quickly as possible.
Treating the eggs with oil or wax before refrigeration also extends its shelf life for several months. An odourless, colourless, tasteless mineral oil is used and the process is done under controlled conditions.
Recently, it has been found that small amount of CO2 passed into the storage rooms prevents the loss of CO2 from the eggs, thus enhances the shelf life.
Shelf life of the eggs can be increased by pasteurization at a temperature of 52-55°C for 3 minutes. Thermostabilization is the process in which the eggs are heated in oil or water at about 54-58°C for about 16 minutes to preserve quality during storage. The whites of thermostabilized eggs are more viscous. It is more difficult to separate the white and yolk. More time is required for whipping. It has low foam volume, which leads to decreased volume of the egg products. Other functional properties are not affected.
Cooking of Eggs
The most important rule of egg cookery is “avoid high temperature and long cooking time”. In other words, don’t overcook eggs. Overcooking produces tough eggs, discolouration and it flavour too. Egg white coagulates at 60-65°C, yolk at 65-70°C, whole beaten egg at 69°C and custard at 79-85°C, depending on the amount of milk used. White coagulates before yolk and hence it is possible to boil eggs with firm white and soft yolk. Coagulation depends on length of heating and the presence of added materials like vinegar and salt, which will speed up the coagulation.
Overcooked eggs are tough and rubbery. When eggs are over-cooked, as in case of scrambled eggs and custards, the egg solids separate from liquids or appear curdled. This is known as weeping of eggs.
Blue ring formation on hard-boiled eggs is caused by cooking too long at high temperatures. This is also seen in scrambled eggs, which are cooked on high temperatures. The iron from the yolk combines with the sulphur from the white to form ferrous sulphide, which has blue colour and strong flavour. To avoid blue ring formation, cook at low temperature and arrest the cooking by plunging in cold water or cracking the shell.
Egg white has the ability to trap or hold air – foaming – which helps to increase to seven times its original volume, when beaten. Beaten egg whites give lightness or raising power to fluffy omelets, pudding and soufflés.
Methods of Cooking
Cooking of Egg
In the Shell
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Out of the Shell
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Soft cooked
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Medium cooked
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Hard cooked
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Unmixed
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Mixed
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Coddled Egg
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1. Poached
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2. Fried (Single or Double)
3. Shirred eggs (Baked in individual dishes and served garnished in the same)
4. Cocottes (Eggs steamed in cocotte dishes on a water bath )1. Scrambled eggs
2. Omelets (Plain and foamy)
Poaching
The aim is to keep eggs in compact form, rather than spread out over the pan. This is done on a shallow pan because the water is simmering and not boiling, as boiling disintegrates the egg. 5 gms of salt and 10 ml of vinegar for 1 l of water is advisable. Vinegar helps to increase the coagulation, while salt increases the coagulation temperature. Ideal time for poaching is 3-5 minutes.
Frittata
Frittata is a flat omelet that originated in Italy. Flat omelets are made by mixing beaten eggs with a variety of ingredients such as vegetables, meat or cheese and cooking the mixture over low heat without stirring. To finish, it is either flipped over or flashed under the broiler until the top is set.
Soufflés
Soufflés are similar to foamy omelets except that they have a white sauce basis and have some foods such as grated cheese, vegetable pulp or ground meats used for flavour. The heat coagulated protein of both yolk and white give structure to soufflés. The expansion of air in the egg foam as these products bake causes them to rise and appear puffed. Soufflés are baked in special oven-proof moulds at 117°C and served immediately in the moulds in which they are baked. All soufflés – regardless of flavour – should be light, tender, well blended, of good volume, slightly moist and delicately browned.
Factors affecting the whipping quality of eggs
Ø Season of egg production (Mid-summer eggs beat to lesser volume).
Ø Quality of egg white (Thick whites give more stable foam).
Ø Temperature (Eggs at room temperature whip more quickly and to large volume).
Ø Type of beater (Fine wires divided egg whites easily and air cells remain smaller).
Ø Container (Bowls with small rounded bottoms and sloping sides are preferable as the beater can more easily be pick up the egg mixture. The size of the bowl depends on the quantity of whites to be whipped).
Effect of added substances
Ø Milk prevents foam formation due to the presence of fat. Skimmed milk may be used.
Ø Presence of fat from the yolk, container or beaters may affect the whipping quality.
Ø Salt decreases the volume and stability of the foam and increases the whipping time.
Ø Acids decrease the alkalinity and increase the stability of the foam. Acid may be added after the white has started to get stiff foam of good volume.
Ø Sugar retards denaturation of egg proteins. Add sugar only after the whites are beaten to peaks. Egg white is denatured by beating and heat.
Uses of eggs
Ø Raising agents as in cakes.
Ø Binding agents as in koftas and cutlets.
Ø Flavouring agent (improves taste) as in cakes.
Ø Emulsifying agent helps in mixing of emulsions.
Ø Enrichment in child’s feed.
Ø Rich in nutrients.
Ø First semi-solid food for infants – as easily digestible.
Ø Clarifying agent as in consommé.
Ø Garnishing.
The word “Farinaceous” is derived from the Latin word “Farina” meaning flour and the French word “Farineux” and “Farinages”. The English term “Farinaceous” indicate a wide range of dishes made with different flours, usually as a main ingredient. These include the vast range of Indian pastas in their many different forms, shapes and sizes and a range of similar uses and value for the menu.
In the traditional menu, these three types of dish are normally served as a subsidiary item for lunch, coming up after the soup or frequently acting as a hors d’oeuvre. When garnished and with a suitable sauce, they can serve as a substantial main dishes any time of the day. When plainly prepared and not over garnished, they make suitable garnishes for a number of fish, meat and poultry dishes. It is usual to serve gratedParmesan cheese or similar, as an accompaniment for most farinaceous dishes and rice dishes.
Gnocchi
There are three main types of small dumplings or Gnocchi:
1. Gnocchi Parisienne (Made from flour, egg and butter, which in effect is a basic choux paste).
2. Romaine (Made from milk, semolina and egg).
3. Gnocchi Italienne (Made from potato, flour and egg).
Basically these are all gratinated with butter and cheese, but can all be lightly garnished or mixed with mushrooms, cooked sausages, poultry or meat. Tomato sauce, jus-lie, Béchamel and cream are used as variations.
Pastas
The name “Pasta” is the Italian word for “paste”; so called because pasta is made from a mixture of durum wheat flour and water and sometimes eggs. Durum wheat (High gluten quality and content) is milled and mixed with water, salt, eggs, oil and at times, vegetable colouring. Semolina or rawa is preferred to flour because less water is required to make the pasta dough, which greatly helps in the drying stage.
Types of Pasta
1. Commercial Pastas
It is made from dough that has been shaped and dried (Pasta second-dry pasta).
It is made from dough that has been shaped and dried (Pasta second-dry pasta).
a. Macaroni (Refers to pastas made from flour and water. These include spaghetti, lasagna, elbow macaroni etc.).
b. Egg pastas (Contain at least 5.5% egg solids, in addition to the flour and water. They are sold as flat noodles of various widths).
2. Fresh Egg Pasta
Fresh egg pasta or pasta all’uovo are made from flour and eggs and sometimes, a small quantity of water and/or oil. Soft egg noodle products are also available in fresh and frozen form from the manufacturer. They take less time to cook than dried macaroni products.
Fresh egg pasta or pasta all’uovo are made from flour and eggs and sometimes, a small quantity of water and/or oil. Soft egg noodle products are also available in fresh and frozen form from the manufacturer. They take less time to cook than dried macaroni products.
3. Fancy Pastas
This group contains cut macaroni, which may be straight or slant out and a large variety of fancy shaped pastas.
This group contains cut macaroni, which may be straight or slant out and a large variety of fancy shaped pastas.
Pastas may be classified according to their size and shapes as:
1. Long Pasta
This group includes smooth, solid rod forms e.g. spaghetti, vermicelli, tubular forms of which the outer surface may be smooth or corrugated like macaroni and flat from inside.
This group includes smooth, solid rod forms e.g. spaghetti, vermicelli, tubular forms of which the outer surface may be smooth or corrugated like macaroni and flat from inside.
2. Short pieces of Pasta
e.g. Farafallette (Butterfly shaped Pasta).
e.g. Farafallette (Butterfly shaped Pasta).
3. Pasta suitable for stuffing
These are of two types:
These are of two types:
a. Those that are stuffed, while the pasta is in raw stage and then cooked e.g. ravioli, tortellini.
b. Those that are partially cooked before being stuffed and then cooking is completed e.g. cannelloni.
4. Small Fancy Pastas
This group consists of a large variety of small pastas which are used almost exclusively for garnishing. E.g. Capellini (Fine hair-like vermicelli), Alfabeto (Letters and numbers), Stellette (Small stars).
This group consists of a large variety of small pastas which are used almost exclusively for garnishing. E.g. Capellini (Fine hair-like vermicelli), Alfabeto (Letters and numbers), Stellette (Small stars).
Cooking of Pastas
All pastas should be cooked in boiling salted water, allowing at least 1 liter of water and 10 Gms of salt per 100 Gms of raw pasta. They should be gently stirred with a wooden spoon to prevent sticking together and allowed to simmer gently.
Stuffed pastas like ravioli require very gentle simmering only to prevent breaking. The actual cooking time is determined by the size or thickness of the pasta, but in all cases, it should not be overcooked. Cook all pastas to “al-dente” stage, drain well and use immediately.
If not served immediately, the cooked pasta can be refreshed and kept in a basin of cold water or tossed with oil and kept in the refrigerator. Where possible, pasts should always be freshly cooked and used immediately.
In addition to the standard finishing of butter, cream and grated Parmesan cheese, there are a number of sauces like Béchamel sauce, Crème, Jus-lie, Demi-glace, Sauce Italienne, Sauce Champignon, Sauce Tomate, Pesto and Provenoale. Besides these, there are a few sauces which are special to pasta dishes, as well as some of which become an integral part of the dish e.g. Bolognaise, Sauce Nicoise or Tomato and Basil Sauce.
Noodles
The word “Noodle” is derived from the German word for dumplings “Nudeln”. Dumplings seem to have originated from the practice of putting uncooked dough or bread pieces into soups or stews. Noodles are defined as “food paste made of flour, water and eggs, which may be either dried or fresh. Noodles are also referred to as “vermicelli”, regardless of whether they come from Italy or Hong Kong. The main areas of production are Central Europe, America and the Far East.
The Germans are the first to make noodle dough with eggs. Egg noodles are also popular with the Italians and the Chinese. Asian noodles may be based on a number of different flour pastes, with or without eggs, including the flour of mung, soy beans, sea weed, corn, chick peas, rice and durum wheat. The Japanese have an impressive range of noodle made of golden buckwheat. Japan shares China for a fondness for cellophane noodles called in Japan as “Harusame”.
Dumplings
Dumplings are starch products made from soft dough or batter and are cooked by simmering or steaming. They are served as side dishes and in soups and stews. Different National cuisines have their own kind of dumplings e.g. Potato dumplings and Caraway dumplings.
Spaetzle
Spaetzle are small dumplings or noodles made from a thin egg and flour batter.
Yield
450 Gms of uncooked pasta yields about 1.4 kg of cooked pasta. This is enough for 4-5 portions of main course or 8-10 side dish or first course portions.
Milk is the natural food for mammals in the first stages of life. It is thenear-perfect single food containing protein, carbohydrate, fat, minerals and vitamins. However, it is lacking in iron, vitamin C and D. It is one of the most complete foods, because it contains the nutrients required for growth and development. Milk obtained from several species of animals is used for human consumption, but the most popular are cows, buffaloes and goats’ milk.
Composition
Components
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Cow’s milk
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Buffalo’s milk
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Water
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85-87%
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80%
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Carbohydrate
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5%
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5%
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Protein
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3%
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4.5%
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Fat
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4%
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9%
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Vitamins and Minerals
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1%
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1.5%
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However, the composition doesn’t always remain the same. This will vary slightly, depending upon the species, the age and the feed of the animal. It will also depend upon the lactation period and as animal advances in age, the fat content will also increase. Animals who feed on grass pastures produce a high yield of milk, richer in Vitamin A.
Nutritive Value
Protein
Some of the most complete forms of protein are found in milk. Casein is the main milk protein. It is insoluble in water and is very easily precipitated by acids. This results in the curdling of milk. Lactoglobulinand Lactalbumin are the other two proteins that are found in milk. They coagulate easily on heating and are responsible for the precipitate found at the bottom and the sides of the pan used for the heating of milk. They are not easily precipitated by acid.
Carbohydrates
The main carbohydrate found in milk is Lactose or milk sugar. Lactose is not very soluble in water and it is responsible for the sweet taste in milk. Lactose also tends to crystallize in milk powder during storage and results in lump formation and caking. It isn’t water soluble and is responsible for the sandy or gritty texture in condensed milk and ice-cream. In the souring of milk, lactic acid bacteria converts lactose into lactic acid, giving sour milk its characteristic flavour.
Fat
The fat constituent of milk is present in the form of cream. It is dispersed as fine globules. When heated, it rises to the surface, where it forms a layer. It contains fat-soluble vitamin A and D. Together with lactose, fat provides the energy in the diet.
Minerals and Vitamins
Milk is rich in calcium, phosphorus, sodium, potassium and all the vitamins known to be essential for human nutrition are present in milk. Milk is rich in Vitamin A, S, E and K.
Since milk contains a great deal of water, it is a very dilute food. Because of this, it is easy to consume and digest. Milk is an ideal food for all, especially infants and young children. There is no evidence that it is an indispensable constituent of the adult diet.
Processing
From the time it is milked from the animal to the time of sale, milk has to undergo processing to improve the keeping quality and to make it fit for consumption. The various stages are:
1. Collection
Milk is brought to the dairy in clean sterilized vessels, preferably stainless steel.
Milk is brought to the dairy in clean sterilized vessels, preferably stainless steel.
2. Holding tanks
The milk is immediately transferred to holding tanks and is held at 10°C to keep it safe. Cooling is done either in a tank, jacketed with pipes in which runs a brine solution. Else the milk is run over very cold water pipes.
The milk is immediately transferred to holding tanks and is held at 10°C to keep it safe. Cooling is done either in a tank, jacketed with pipes in which runs a brine solution. Else the milk is run over very cold water pipes.
3. Filtration
The milk is passed through a series screens and filters to remove sediment and floating particles.
The milk is passed through a series screens and filters to remove sediment and floating particles.
4. Pasteurization
It is the process of heating milk to 63.7°C and holding it at that temperature for 30 minutes. This is known as the “Holder Process of Pasteurization”. Nowadays, the Flash Pasteurization is more commonly used. It is also called the HTST or High Temperature Short Time method, where the milk is heated to 71.6°C for only 15 seconds. Pasteurization makes milk safe for human consumption by destroying pathogenic germs (pathogens). It also helps to increase the shelf life. Flavour of the milk remains unaffected at pasteurization temperature.
It is the process of heating milk to 63.7°C and holding it at that temperature for 30 minutes. This is known as the “Holder Process of Pasteurization”. Nowadays, the Flash Pasteurization is more commonly used. It is also called the HTST or High Temperature Short Time method, where the milk is heated to 71.6°C for only 15 seconds. Pasteurization makes milk safe for human consumption by destroying pathogenic germs (pathogens). It also helps to increase the shelf life. Flavour of the milk remains unaffected at pasteurization temperature.
5. Homogenization
At temperature of 60°C, milk is passed under high pressure through small opening of a machine called homogenizer. The main purpose is to subdivide the fat globules in milk and disperse them evenly in the entire mass. Fat has a low density and tends to rise to the surface during heating. Homogenization prevents this by first breaking up the fat into tiny particles and then dispersing them throughout the milk. This adds to the flavour and results in a better body.
At temperature of 60°C, milk is passed under high pressure through small opening of a machine called homogenizer. The main purpose is to subdivide the fat globules in milk and disperse them evenly in the entire mass. Fat has a low density and tends to rise to the surface during heating. Homogenization prevents this by first breaking up the fat into tiny particles and then dispersing them throughout the milk. This adds to the flavour and results in a better body.
6. Bottling
The bottles of selected and uniform size have to be sterilized by steam and hot water and then they are filled with milk, which are capped automatically. Nowadays milk is filled in plastic pouches and these are more economical, easily transported and save storage space. Plastic pouches are easily disposed and are safe to handle.
The bottles of selected and uniform size have to be sterilized by steam and hot water and then they are filled with milk, which are capped automatically. Nowadays milk is filled in plastic pouches and these are more economical, easily transported and save storage space. Plastic pouches are easily disposed and are safe to handle.
7. Sterilization
The sealed bottles are now heated for 30 to 40 minutes at temperatures ranging from 104-110°C in steam chambers calledautoclaves and then allowed to cool. Milk can also be sterilized before bottling. It is subjected to temperatures of 135-150°C for just 1 second. This is called the UHT or Ultra Heat Treatment. This process kills off all microorganisms and the very short holding temperature reduces the changes in colour and lined with aluminum foil. Milk is then distributed through various outlets.
The sealed bottles are now heated for 30 to 40 minutes at temperatures ranging from 104-110°C in steam chambers calledautoclaves and then allowed to cool. Milk can also be sterilized before bottling. It is subjected to temperatures of 135-150°C for just 1 second. This is called the UHT or Ultra Heat Treatment. This process kills off all microorganisms and the very short holding temperature reduces the changes in colour and lined with aluminum foil. Milk is then distributed through various outlets.
Effect of heat on Milk
Digestibility is slightly improved in the heated milk as it tends to form smaller, tenderer curds in the stomach than are formed from raw milk. Heating to higher temperatures than those used in pasteurization effects a greater variety of changes in milk. The tendency of milk to curdle is diminished by the use of low or moderate temperatures. Casein is not coagulated at the usual temperatures. It coagulates when heated at too high temperatures or for long period of time at boiling temperature.
The coagulation of milk protein by heat is accelerated by an increase in acidity. Heating milk brings about an increase in acidity. The addition of acid foods to milk may also result in coagulation.
The browning reaction, non-enzymatic browning or Millard reaction occurs when sugars and proteins are heated together. The prolonged heating of condensed milk in the can results in a product of brown colour, caramel flavour and thickened consistency.
Minerals like calcium phosphate is precipitated by heat and sometimes gets collected at the bottom of the pan with coagulated albumin and some of it gets entangled in the scum on the top surface of the milk.
Skin formation is one of the most troublesome of reactions that occurs during the heating of milk. It may be prevented by covering the pan, by diluting the milk, or by presence of fat floating on the surface. As the temperature is increased, a tough scum forms, which is insoluble and can be removed from the surface. The scum is composed of coagulated albumin with some precipitated salts and fat globules. Scum formation can be prevented by beating the cooked milk with a beater. The formation of scum on boiled milk is the principal reason for the behaviour of milk in boiling over. A certain amount of pressure develops under the scum, which later forces the scum upward and the milk flow over the sides of the pan i.e. spill.
The flavour of milk that has been heated to boiling temperatures or above is described as Flat. It is due to the loss of dissolved gases, carbon dioxide and oxygen. Some change that occurs in the protein also influences the flavour of the cooked milk.
The layer of fat that may form on milk that is boiled is the result of the breaking of the films of protein that surround the fat globules in unheated milk. The breaking of the films of emulsifying agent permits the firm coalescence of fat globules.
The scorching of milk placed over direct heat is due in part to the film of coagulated albumin that collects on the bottom and sides of the pan. Stirring the milk while heating lessens the thickness of the film, but may not prevent scorching, particularly if large quantity of milk is heated. Millard reaction is responsible for the brown colour of the scorched milk. Heating milk over hot water will retard or completely prevent scorching.
Acid coagulation of milk
Acid – either that which is formed by bacterial action in milk, or by added acid – precipitates casein as curd. The acid curdling the milk is a desired reaction in the making of some cheese and curd, but is undesirable in food products such as curdling of tomato soup, fruit cream and causes the casein to precipitate.
Rennin is an enzyme present in the stomach of man and animals which helps to clot milk during digestion. Commercially the enzyme is available in the form of rennet tablets or extract, which are prepared from the inner lining of the stomach of calves and lambs.
The action of vegetable enzyme – bromelin – from pineapple also clots milk, but later digests the clot. Other enzymes in fruits are responsible for some of the curdling action that occurs when milk or cream and certain fruits are combined. All fruits and vegetables contain some organic acids but not always in sufficient concentration to cause the curdling of milk. Destroying the enzymes before combining the fruit with the milk will prevent curdling caused by enzyme action. Curdling of milk may occur if tannin containing foods, such as potatoes are cooked in milk. Tannins are also present in brown sugar and in cocoa product.
Besides enzymes, acids and tannins, salts present in the milk, in the food combined with the milk, or added sodium chloride may also influence coagulation of the casein. Of the meats commonly cooked in milk, ham usually causes more coagulation than chicken, veal or pork. The high sodium content of ham may be responsible for the excessive curdling that occurs when cooked with milk.
Type of Milk
A. Fluid Milk
1. Whole milk
Milk that has none of its fat removed. It generally contains 3.25% fat. This fat is not homogenized so that the milk will have cream line.
Milk that has none of its fat removed. It generally contains 3.25% fat. This fat is not homogenized so that the milk will have cream line.
2. Skimmed Milk
This type of milk became popular because of the emphasis on low-fat diet. Cream is separated by machine. Skimmed milk resembles fresh whole milk, except that the fat content is less than 0.5%, but rest of the nutrients remains the same, except for fat soluble vitamins. It is often fortified with vitamin D and minerals. Skimmed milk is usually pasteurized and may also be homogenized.
This type of milk became popular because of the emphasis on low-fat diet. Cream is separated by machine. Skimmed milk resembles fresh whole milk, except that the fat content is less than 0.5%, but rest of the nutrients remains the same, except for fat soluble vitamins. It is often fortified with vitamin D and minerals. Skimmed milk is usually pasteurized and may also be homogenized.
3. Homogenized Milk
It has the same composition as the whole fluid milk, but the fat content is dispersed throughout the mass through the process of halogenations. There won’t be any cream line when the milk is heated.
It has the same composition as the whole fluid milk, but the fat content is dispersed throughout the mass through the process of halogenations. There won’t be any cream line when the milk is heated.
4. Toned Milk
Toning is done to make buffalo milk resemble in appearance and flavour to cow’s milk. It is done by dilution and addition of skimmed milk powder. 40 % of skimmed milk is added to 60% of buffalo milk. The addition of skimmed milk powder makes up for the dilution of the nutrients, the fat content remains diluted and equal to that of cow’s milk.
Toning is done to make buffalo milk resemble in appearance and flavour to cow’s milk. It is done by dilution and addition of skimmed milk powder. 40 % of skimmed milk is added to 60% of buffalo milk. The addition of skimmed milk powder makes up for the dilution of the nutrients, the fat content remains diluted and equal to that of cow’s milk.
5. Fortified Milk
Additional nutrients such as Vitamin D may be added to milk to improve the quality.
Additional nutrients such as Vitamin D may be added to milk to improve the quality.
6. Flavoured Milk
Addition of flavouring agents such as essences like vanilla, strawberry and masalas to improve the flavour, appearance and to add more variety.
Addition of flavouring agents such as essences like vanilla, strawberry and masalas to improve the flavour, appearance and to add more variety.
B. Concentrated Milk
1. Evaporated Milk
This is unsweetened concentrated milk. After pasteurization. The milk is evaporated under reduced pressure in steam heated vacuum pans, till the volume has been reduced to 60%. It is then homogenized, cooled and canned.
This is unsweetened concentrated milk. After pasteurization. The milk is evaporated under reduced pressure in steam heated vacuum pans, till the volume has been reduced to 60%. It is then homogenized, cooled and canned.
2. Condensed Milk
The term usually implies whole milk, which has been partially evaporated and to which sugar has been added. This is sweetened concentrated milk. 27% moisture remains out of 80%. It has a 62% sugar concentration. The milk is cooled very carefully, so that the crystallization of the lactose is in very fine crystals before being canned.
The term usually implies whole milk, which has been partially evaporated and to which sugar has been added. This is sweetened concentrated milk. 27% moisture remains out of 80%. It has a 62% sugar concentration. The milk is cooled very carefully, so that the crystallization of the lactose is in very fine crystals before being canned.
3. Dried Milk or Milk Powder
In this case, the water content is removed completely and thereby the bulk is reduced. It requires no special storage facilities and is an outlet for the skimmed milk from cream and butter production. There are two processes for drying milk:
In this case, the water content is removed completely and thereby the bulk is reduced. It requires no special storage facilities and is an outlet for the skimmed milk from cream and butter production. There are two processes for drying milk:
a. Roller Drying
The milk is usually concentrated in an evaporator until it has 97% total solids as against 11.5% in normal fluid milk. The milk is then fed into the very smooth surface of single or twin heated drums, operating at temperatures of 150°C (303°F). The water content of the milk evaporates very quickly, leaving behind a thin film of dried milk, which is then scraped off by a blade that is attached to the drums. This is then cooled before being ground into a very fine powder. It is then sieved and packed into airtight containers. Milk powder is hydroscopic and will quickly absorb moisture from the air and the powder will deteriorate, becoming stale in flavour and less soluble in reconstitution. Although roller drying is cheaper and produces a product that is practically free from bacteria owing to the severe heat treatment it receives, it does develop a cooked flavour and will not reconstitute easily. The structure of the fat globules in milk is destroyed, causing an oily layer on the surface when reconstituted in warm water.
The milk is usually concentrated in an evaporator until it has 97% total solids as against 11.5% in normal fluid milk. The milk is then fed into the very smooth surface of single or twin heated drums, operating at temperatures of 150°C (303°F). The water content of the milk evaporates very quickly, leaving behind a thin film of dried milk, which is then scraped off by a blade that is attached to the drums. This is then cooled before being ground into a very fine powder. It is then sieved and packed into airtight containers. Milk powder is hydroscopic and will quickly absorb moisture from the air and the powder will deteriorate, becoming stale in flavour and less soluble in reconstitution. Although roller drying is cheaper and produces a product that is practically free from bacteria owing to the severe heat treatment it receives, it does develop a cooked flavour and will not reconstitute easily. The structure of the fat globules in milk is destroyed, causing an oily layer on the surface when reconstituted in warm water.
b. Spray Drying
The milk is pre-heated to 80-90°C for 10 seconds. It is homogenized and concentrated at 43°C to about 40% total solids. The milk is then atomized to a fine mist in a drying chamber containing hot air at 165°C (330°F). The very minute milk particles give off their moisture content almost instantaneously and drop to the bottom of the drying chamber as tiny grains of dried milk. The powder is removed to cool as quickly as possible, before being packed into airtight containers. This method is more expensive than Roller drying, but has 98% solubility with less pronounced flavour changes than Roller dried milk.
The milk is pre-heated to 80-90°C for 10 seconds. It is homogenized and concentrated at 43°C to about 40% total solids. The milk is then atomized to a fine mist in a drying chamber containing hot air at 165°C (330°F). The very minute milk particles give off their moisture content almost instantaneously and drop to the bottom of the drying chamber as tiny grains of dried milk. The powder is removed to cool as quickly as possible, before being packed into airtight containers. This method is more expensive than Roller drying, but has 98% solubility with less pronounced flavour changes than Roller dried milk.
c. Instant Milk Powder
This type of powder will dissolve easily and completely when added to water, tea or coffee. The process is a modified spray-drying method in which the dried milk powder is moistened with steam to give a lumpy porous structure; the lumps of powder are being dried, cooled and then reduced to a more standard size. When added to a liquid, they quickly absorb it and dissolve completely. The cost of this type of milk powder is high and it is mainly used in hot beverages
This type of powder will dissolve easily and completely when added to water, tea or coffee. The process is a modified spray-drying method in which the dried milk powder is moistened with steam to give a lumpy porous structure; the lumps of powder are being dried, cooled and then reduced to a more standard size. When added to a liquid, they quickly absorb it and dissolve completely. The cost of this type of milk powder is high and it is mainly used in hot beverages
The concentration of milk serves three main purposes:
1. It reduces bulk by the reduction of the water content.
2. The heat treatment and high sugar content in condensed milk gives the product a good shelf life.
3. It is convenient outlet for skimmed milk from the production of butter and cream.
Substitute milk powder
It doesn’t contain any milk constituent at all, but are especially processed from products such as dried glucose, syrup and vegetable fat.
Imitation milk
Also known as Substitute milk, it is a recent development. The products don’t contain any milk constituent, but contain glucose syrup and vegetable fat. It has a very low calorific value. Another substitute being promoted as a healthier alternative to milk is Soya milk. Soya milk is much cheaper, but leaves an unpleasant after-taste and flavour. Imitation and substitute milk are ideal for those who are lactose intolerant i.e. allergic to milk.
C. Cultured Milk
The process consists of deliberately souring the milk by adding specific harmless bacteria, which will then produce an acid and so control the growth of possible harmful bacteria. The process originated by man’s attempts to prevent milk from being totally unusable and develops into a variety of products, which are nutritious and easily digestible. Cultured milk can be classified into three groups, as listed:
1. Butter Culture
These include butter-milk and cultured cream.
Butter-milk is a byproduct from the manufacture of butter. It is made from pasteurized skimmed milk, which is incubated with an acid producing butter culture.
Cultured cream is prepared from pasteurized single cream, which is incubated with an acid producing butter culture. It is often marketed as “fresh soured cream” to distinguish it clearly from cream, which has soured by accident or carelessness. It may be used in recipes instead of sour cream.
These include butter-milk and cultured cream.
Butter-milk is a byproduct from the manufacture of butter. It is made from pasteurized skimmed milk, which is incubated with an acid producing butter culture.
Cultured cream is prepared from pasteurized single cream, which is incubated with an acid producing butter culture. It is often marketed as “fresh soured cream” to distinguish it clearly from cream, which has soured by accident or carelessness. It may be used in recipes instead of sour cream.
2. Yogurt Culture
These include yogurt (in many forms and flavours), curdled milk and soured milk drinks. Yogurt can be made from whole, skimmed, evaporated or dried milk or a mixture of these. Various types of yogurt are available – natural yogurt made from milk products, natural yogurt sweetened with sugar, fruit yogurt, which may be flavoured with pieces of fruits or just fruit juice or a flavouring essence.
These include yogurt (in many forms and flavours), curdled milk and soured milk drinks. Yogurt can be made from whole, skimmed, evaporated or dried milk or a mixture of these. Various types of yogurt are available – natural yogurt made from milk products, natural yogurt sweetened with sugar, fruit yogurt, which may be flavoured with pieces of fruits or just fruit juice or a flavouring essence.
3. Weak alcoholic beverages
This group differs from the previous groups in that yeast cultures, which produce alcohol, are added, in addition to bacterial cultures. This group includes:
This group differs from the previous groups in that yeast cultures, which produce alcohol, are added, in addition to bacterial cultures. This group includes:
a. Kefir (Poland)
It is made from whole or skimmed cow’s milk to which the kefir grain is added. The milk is incubated for three days, during which the alcohol and acid percentage increases. The finished product resembles single cream in appearance and has a lactic acid flavour.
It is made from whole or skimmed cow’s milk to which the kefir grain is added. The milk is incubated for three days, during which the alcohol and acid percentage increases. The finished product resembles single cream in appearance and has a lactic acid flavour.
b. Koumiss/Kumis (Russia)
It was originally made from mare’s milk and is now produced from cow’s milk. Two cultures are added to milk and is incubated at 37°C for about 4-6 hours and cooled to 30°C and yeast added and incubated for 4 hours at 25°C. Matured for 3 days during which the alcoholic and acid percentage increases. The product resembles single cream in appearance, but is slightly grey in colour and has smell gas bubbles throughout, sour in taste and has a faint alcoholic smell.
It was originally made from mare’s milk and is now produced from cow’s milk. Two cultures are added to milk and is incubated at 37°C for about 4-6 hours and cooled to 30°C and yeast added and incubated for 4 hours at 25°C. Matured for 3 days during which the alcoholic and acid percentage increases. The product resembles single cream in appearance, but is slightly grey in colour and has smell gas bubbles throughout, sour in taste and has a faint alcoholic smell.
c. Whey Champagne (Poland)
This is made from clarified way with the addition of yeast and caramel. The product is of a clear, light amber colour with a slight sparkle to it and a faint caramel flavour.
This is made from clarified way with the addition of yeast and caramel. The product is of a clear, light amber colour with a slight sparkle to it and a faint caramel flavour.
d. Feliwsoka (Poland)
It is made from buttermilk, which is fermented at 15-18°C for 8-10 hours, until the required acidity is reached. The liquid that has separated to the top is removed and sugar and yeast are added. The buttermilk is then bottled, sealed and kept at 18-20°C for 4 hours, cooled below 8°C and stored. The final product appears foamy due to carbon dioxide production and has a sweet, yeasty and refreshing taste.
It is made from buttermilk, which is fermented at 15-18°C for 8-10 hours, until the required acidity is reached. The liquid that has separated to the top is removed and sugar and yeast are added. The buttermilk is then bottled, sealed and kept at 18-20°C for 4 hours, cooled below 8°C and stored. The final product appears foamy due to carbon dioxide production and has a sweet, yeasty and refreshing taste.
Uses of Milk
1. Served as a refreshing drink – both hot and cold.
2. Served as a beverage with tea and coffee.
3. The main ingredient in some sauces like Béchamel.
4. Used to enrich dishes like soups and to give a smooth texture.
5. The main ingredient in several desserts like ice-cream, puddings and custards.
6. The first food for new born infants.
7. Acts as a cooking medium for Indian sweets like Kheer or Payasams.
Storage of Milk
The rich nutritional composition of milk makes it readily infected with micro-organisms, which may be derived from the animal, the equipment or the people handling the milk. Fresh milk should be purchased daily. Old and new milk should never be mixed. Leftover milk can be easily converted into curds. Fresh milk should be stored at refrigerated temperatures of 2°C after boiling and cooling. Milk should never be stored near strong smelling foods such as cut onions and peeled garlic as milk readily absorbs flavours and odour. Milk must never be exposed to direct sunlight as riboflavin is very easily lost. UTH and canned (evaporated and condensed) milk must be stored at slightly lower than room temperatures. When opened, they must be refrigerated immediately and used within two days. Dried milk must be stored in airtight containers in a cool and dry area of the storeroom.
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