By Products of Milk Processing

By products of milk processing: 1. T. Casein (Edible) 2. Buttermilk 3. Whey 4. Lassi 5. Ghee-Residue.

1. T. Casein (Edible):

Edible casein may be defined as casein which has been isolated from skim milk by taking special precautions to ensure its suitability for use in patented food and pharmaceuti­cal preparations.

These precautions are concerned chiefly with:

(i) Strict control of the quality of the raw material (skim milk);

(ii) Use of standard equipment and technique for production;

(iii) Maintenance of strict hygienic conditions of production, and

(iv) Packaging and storage under approved conditions.

Specifications:

The Indian Standard Specifications for cas­ein (edible quality) are given in Table 12.8.

Method of Preparation:

These include:

(i) Precipita­tion of the curd at pH 4.1-4.3;

(ii) At least 3 separate washings of the curd in waters of proper pH and with a contact time of 15-20 minutes each;

(iii) Last but one washing with hot water at 71-77°C (160-170°F), which effects pasteurization of curd for reducing bac­terial count;

(iv) Last washing with neutral water at 41°C (105°F); etc.

Uses:

In its original form or as sodium caseinate, edible casein is used in various food products such as:

(i) Ice cream;

(ii) Coffee whiteners;

(iii) Imitation milk;

(iv) Whipping powders;

(v) Instant breakfast;

(vi) Water binders in sausages, and

(vii) Pro­tein hydrolysates.

2. Buttermilk:

A. Condensed Buttermilk:

Also known as semi-solid buttermilk, this is usually sweet cream buttermilk which has been ripened and condensed (approx. 3:1) in much the same way as concentrated sour skim milk. Alternatively, sour-cream buttermilk may be used without ripening it, but the acidity (lactic) of the buttermilk prior to its being condensed should be greater than 1.6 per cent.

This will ensure in the finished product a 5-6 per cent acidity, which is neces­sary for long keeping quality. Either sour whey or an organic acid (such as lactic, acetic, citric or tartaric) may be used to increase the acidity of buttermilk.

While the older packages were air-tight wooden barrels, a modern package might consist of an acid-resis­tant, tight plastic film with a suitable fibre board container. Con­densed buttermilk is also used for feeding pigs and poultry.

B. Dried Buttermilk.

C. Soft Cheese from Buttermilk:

The production of soft cheese from creamery buttermilk may be outlined as follows- fresh buttermilk, obtained by churning sweet-cream butter, is admixed with fresh skim milk in the proportion of 1:1. The mixture is pasteurized at 65°C for 20 minutes, cooled to 35°C, inoculated with lactic starter @ 10 per cent and allowed to set for 3 hours.

The curd is cut with standard cheese knives and the curd cubes subjected to a cooking process during which a maximum of 40°C is reached in 15-20 minutes. The curd cubes are then collected in a muslin cloth and pressed overnight, preferably inside a cold store (5-10°C), to remove excess moisture.

The pressed curd, which has a rather low keeping quality, can be utilized either for direct consumption after the addition of sugar @ 15 per cent, or in the manufacture of processed cheese up to 10 per cent of raw cheese.

Note:

An Indian work on preservation of (creamery) buttermilk has been reported.

3. Whey:

Whey Beverages:

The whey obtained as a by-product of cheese industries has long since been employed in the production of fer­mented beverages, both alcoholic and non-alcoholic (acidic). The production technique of one such beverage of the acidic type is des­cribed below-

Whevit:

Utilization of whey in the production of a soft drink called whevit may be outlined as follows- fresh whey obtained from chhana (or paneer) making is passed through a cream sepa­rator and the separated whey then steamed for 30 minutes in a double-jacketed vat. It is cooled to room temperature and kept overnight to allow the precipitated proteins to settle down, and then filtered through a muslin cloth.

Now 50 per cent sugar syrup @ 22-23 per cent of whey, 10 per cent citric acid @ 2-2.1 per cent of whey and sugar mixture, and selected colour and flavours in requi­site amounts are added. The above mixture is inoculated with a culture of Saccharomyces Cerevisae @ 1 per cent of yeast whey broth.

(Whey broth is prepared by adding 1 per cent sugar in filtered whey and sterilizing it at 15 lb. pressure for 15 minutes; the inoculum is prepared by inoculating it with the yeast culture and incubating it for 48 hours at 25°C.) After mixing the inoculum in the whey, it is incubated at 22°C for 14-16 hours. The bottles with their contents are then crown-corked to retain the carbon dioxide and pasteurized at 75°C for 30 minutes in hot water, cooled and stored at a low temperature (5-10°C).

Alternatively, ‘carbonated’ whevit may be prepared. As in the above, the manufacturing process consists of receiving the whey, separating and steaming it, cooling and precipitating proteins, fil­tering, adding sugar syrup, citric acid, colour and flavour.

The mixture is then filled at 5-10°C into the carbonation-cum-bottling plant for carbonation and crown-corking. The bottles and their contents are subjected to pasteurization at 75°C for 10 minutes in hot water, then slowly cooled and stored at a low temperature (5-10°C) till marketed. Whevit bottles should be gently inverted 2 to 3 times, if required, to make the product homogeneous.

Yeast-Whey:

This is a newly developed product. A world-wide protein deficiency makes the production of yeast from whey parti­cularly attractive, as a much needed food supplement rich in pro­teins and vitamins can be made from a substrate which is often used inefficiently or wasted.

The factors involved in its production are:

(i) Type of whey- a selec­tion is made from wheys resulting from cottage, cheddar or simi­larly made cheese, or casein whey; the whey is separated if neces­sary, to remove the fat which makes drying of the finished product difficult;

(ii) Supplementation of whey- this is done by adding nutrients such as phosphorus, ammonium sulphate, etc., which help to maxi­mize yields;

(iii) Type of yeast- yeast extract or brewer’s yeast (preferably containing Saecharomyces Fragilis) is a necessary additive;

(iv) pH- the optimum is 5.0 to 5.7 for maximum yeast production;

(v) Temperature- the optimum for the growth of yeast-whey is 31 — 32°C (89-91°F);

(vi) Size of inoculum- this is determined by the time required to obtain maximum yield, and

(vii) Oxygen- there should be sufficient oxygen to allow for the growth of yeast.

The yeast suspension is concentrated with a centrifuge so that a slurry of 15-18 per cent solids is produced. It may be washed at this point so that the final product is more bland in flavour. The yeast- slurry can be roller or spray-dried. The dried product can be used as a food supplement for proteins and vitamins.

Plain Condensed Whey:

This is made by pasteurizing the separated whey and draining the hot liquid into the vacuum pan. The whey may be condensed to any degree up to 70 per cent total solids. Condensed whey is highly supersaturated with lactose, which may crystallize in the pan itself and prevent the viscous product from flowing.

If crystallization in the pan can be avoided, a smooth- bodied paste will flow from the pan as a clear syrup. This must then be rapidly cooled to about 32°C (90°F), seeded with lactose and run into containers. It may be used in human and animal food products; it is valuable in confectionary, baked foods and cheese foods and makes excellent chicken feed.

Sweetened Condensed Whey:

Separated, pasteurized, sweet, cheese whey (Cheddar or Swiss) with a quantity of sugar equal to the weight of the solids in the whey, is drawn into a vacuum pan and condensed to at least 75 per cent total solids. The concentrate is cooled to 35°C (95°F), seeded and stirred slowly for 1 to 3 hours to crystallize the lactose.

It may be packed in barrels or cans. It has a salty taste and a characteristic whey flavour. It has good whip­ping properties (provided well-skimmed whey is used as the raw material); the whipped, sweetened, condensed whey may be used in fruit whips, certain candies and frozen dessert preparations.

Whey Protein Concentrates:

These include soluble and coagu­lated whey proteins. Earlier soluble whey proteins were recovered from separated sweet cheese whey by partially neutralizing it, con­densing it to 62 per cent total solids, holding it at 3°C (38°F) for 18 hours with occasional stirring, and then centrifuging the mother liquor.

More recently, using the modern tools of electro dialysis, gel filtration, and reverse osmosis, commercial processes for concentra­ting undenatured whey proteins have been developed. Coagulated whey proteins may be recovered by their heat-denaturation and acid precipitation, followed by filtration or centrifuging. The whey proteins separated by any of the above processes may be used in baking, baby foods, ice cream mixes, whipping agents, emulsifying agents, etc.

Whey Paste:

This is manufactured in Russia by pre-concentrating a mixture of whey and skim milk in a vacuum evaporator, and adding sufficient sugar syrup, butter and cream so as to obtain 15 per cent sugar, 15 per cent fat and 65 per cent total solids in the finished product. After slowly cooling it to 48°C, vanillin is added and the product cooled rapidly to 18-20°C before packaging.

Ricotta Cheese:

This is a product of Italian origin. It is made from cheese whey. Skim milk, buttermilk or whole milk are added to raise the milk-solids level and improve precipitation and flavour. The whey protein is coagulated by heating it to 85°C (185°F) or above, and adding sour whey, citric acid, or white vinegar. The precipitate, which rises to the surface, is dipped and drained, and after being cooled, is salted and packaged. It is sometimes pressed into forms, surface-salted and cured, and used for grating.

Mysost, Gjetost and Primost Cheese:

These are of Scandinavian origin. Mysost is made from cow-milk whey, Gjetost from goat- milk whey, and Primost from whey containing additional milk fat. All the whey-solids are utilized. Primost is light tan in colour with a sweet caramelized flavour and a smooth creamy body. Mysost and Gjetost are darker brown and have a coarser texture.

Sweet whey is condensed in a double effect evaporating pan to 60 per cent total solids and further concentrated in an open drying kettle to 84 per cent total solids. It is heated and constantly agita­ted, until it reaches a plastic condition with a definite brown colour.

The plastic mass is transferred to a kneading box and stirred while it cools to prevent the formation of large lactose crystals. While still warm, it is packed in cubical boxes and cooled until it can be cut and packaged. If no evaporating equipment is available, the whey can be condensed by boiling it in open kettles.

The coagulated pro­tein is skimmed off during the operation, and later re-mixed into the concentrate when it reaches one-fourth of its original consistency. It is vigorously stirred until it attains the consistency of mortar and is transferred to a kneading box and handled as above.

4. Lassi:

Also known as desi (indigenous) buttermilk, this is largely consumed by the producer’s household after seasoning it with salt or sugar, or fed to his cattle. In view of its very small-scale and scattered production, it would be a highly uneconomical pro­position to attempt to collect and utilize it.

5. Ghee-Residue:

This is a nutritious food containing fat, denatured protein, burnt lactose and minerals. Although usually consumed with sugar in the producer’s household, it is generally wasted in the large ghee manufacturing/blending concerns. Indian research so far has shown that it can be utilized in the preparation of candy and chocolate; and can be used as a paste as sandwich- spread and with Indian foods such as idli, dosa and samosa.

Before its utilization, it is desirable to remove the excess fat from the ghee-residue. This can be done by enclosing the material in a piece of muslin cloth and keeping the bundle suspended in a boiling water bath for 30-40 minutes.

The bundle is then taken out and the water allowed to drain out first by itself, and then gently squeezed when partially cool. After this, the residue is given a pre-treatment by boiling it in a similar manner in 10 per cent sodium bicarbo­nate solution, which should be constantly stirred during cooking.

The processed cooked ghee-residue can be made into candy and chocolate as follows:

(i) Candy:

A 50 per cent sugar syrup is first prepared. The cooked residue is thoroughly mixed into the syrup in a karahi by means of a khunti. The mixture is heated on a low fire until a good deal of water has evaporated. To this sticky mass, powdered dry coconut may be added and the candy evenly spread on a plate (5-10°C) for an hour or so to allow it to cool.

It is then cut into small cubes and wrapped in parchment paper for storage at room temperature till marketed. (Note- For every 1 kg. of cooked residue, the sugar required is 500 to 625 g. and dry coconut powder 125 to 250 g.).

(ii) Chocolate:

The cooked residue is mixed with 50 per cent sugar syrup as above. To the sticky mass, cocoa powder and skim milk powder are added and stirred vigorously till a pat is formed. The finished product is spread on a plate and allowed to cool (5-10°C) overnight.

It is then cut into slabs or cubes and wrapped in parchment paper for storage at room temperature before being marketed as above. (Note – For every 1 kg. of cooked residue, the sugar required is 500 to 625 g., cocoa powder 60 to 90 g. and skim milk powder 250 g.)

For making the paste, the procedure is as follows: the cooked residue is first mixed with salt @ 2.5-3 per cent, then with marmite (a yeast product) @ 0.1-0.5 per cent, and heated on a low fire for about 5 minutes till a paste is formed. This can be used in sand­wiches. Alternatively, the salted residue is mixed with chutney powder @ 2-4 per cent, ground thoroughly and then heated as above to yield a paste for use with idli, dosa and samosa.

For making a burfi-type sweet, the recently-developed method is as follows: the processed (sweet) ghee-residue is mixed with stan­dard-quality khoa (prepared from 5 per cent standardized buffalo milk with a moisture content of 30 per cent in khoa) in the propor­tion of 1: 1 of total solids content.

This mixture is heated in a steam-jacketed kettle, and thoroughly agitated with a khunti to ensure proper mixing. All the crystal sugar to be used (calculated @ 45 per cent of total solids in the khoa and 75 per cent of total solids in the processed residue) is now added to the mixture, which is then worked rigorously for 10-15 minutes, so as to dissolve the sugar completely.

Approximately one-third of the sweetened mass is separated and chocolate (@ 8 per cent of the total solids content of the processed residue khoa) well-mixed into it. This portion, con­taining the dissolved chocolate, is applied as a thin layer over the remaining two-thirds of the mixture, which has already been spread out as a thick layer on a well-greased tray. This combined mass is allowed to cool and set and then cut into pieces of a uniform size and shape for packaging and sale. The product has been called ‘chocsidu’ burfi.