The following points highlight the nine main types of special milk. The types are: 1. Vitaminized/Irradiated Milk 2. Frozen Concentrated Milk 3. Standardized Milk 4. Reconstituted/Rehydrated Milk 5. Recombined Milk 6. Toned Milk 7. Double Toned Milk 8. Humanized Milk 9. Miscellaneous Milks.
Type # 1. Vitaminized/Irradiated Milk:
(a) Vitaminized milk is milk to which one or more vitamins are added. Irradiated milk is milk in which the vitamin D content has been increased by exposure to ultra-violet rays. (Mineralized milk is milk to which minerals have been added.)
(b) It is well known that lack of vitamins in the diet causes specific deficiency diseases which, in turn, can be cured by the intake of those particular vitamins. Addition of vitamins (and minerals) to milk is called fortification, and such milk is called fortified milk. The vitamins (and minerals) may be added singly or, more commonly, as multi-vitamin preparations.
(c) Some common vitamin deficiency diseases have been listed in Table 2.3.
Commercial Vitamin D milks can be prepared by any of the following methods:
(i) Metabolized:
By feeding irradiated yeast to milch animals, whereby the vitamin D content of milk can be increased.
(ii) Irradiated:
By exposing a thin, rapidly flowing film of milk to an intensive source of ultra-violet radiation, such as a carbon arc lamp or a quartz mercury vapour lamp, the milk develops an increased vitamin D potency (as a result of conversion of milk cholesterol to vitamin D by rays of wavelength 2700-2900 A).
(iii) Fortified:
By adding a definite amount of standardized vitamin D concentrate.
Type # 2. Frozen Concentrated Milk:
This refers to milk which has been partially concentrated and then solidified by freezing.
(a) Advantages:
(i) Long keeping quality;
(ii) Easy transportation.
(b) Disadvantage:
Destabilization of fat and casein, resulting in oiling-off and sediment formation.
Note:
Un-concentrated frozen cow milk has been regularly supplied from Rajasthan to the Delhi Milk Scheme for the past several years. The raw milk is filled in metallic cylinders which are covered and then lowered in refrigerated brine. After 10 to 12 hours, they are frozen. These cylinders containing frozen milk are transported overnight in insulated railway wagons.
Type # 3. Standardized Milk:
This is milk whose fat and/or solids-not-fat content have been adjusted to a certain pre-determined level. The standardization can be done by partially skimming the fat in the milk with a cream separator, or by admixture with fresh or reconstituted skim milk in proper proportions.
Under the PFA Rules (1976), the Standardized Milk for liquid consumption should contain a minimum of 4.5 per cent fat and 8.5 per cent Solids-not-fat throughout the country.
Note:
Standardized milk may be marketed as such or used for making certain products; in the latter case, the fat and solids-not-fat contents may be varied according to the product requirement.
Merits:
(i) Ensures a milk of practically uniform and constant composition and nutritive value to the consumer;
(ii) The surplus fat can be converted into butter and ghee;
(iii) Possible to supply cheaper milk;
(iv) More easily digestible (because of reduced fat content).
Note:
The initial reaction of the consumer may be that standardized milk is ‘thinner’ than whole milk.
Type # 4. Reconstituted/Rehydrated Milk:
This refers to milk prepared by dispersing whole milk powder (also called dried whole milk) in water approximately in the proportion of 1 part powder to 7-8 parts water. (Usually spray-dried powder is used, since it is more soluble and produces less sediment.)
Merits:
(i) Helps in making up the shortage of fresh milk supplies in developing countries;
(ii) Used by the Armed Forces in other countries.
Method of Manufacture:
Flow Diagram of Manufacture:
Details of Manufacture:
The calculated amount of potable water is received in the pasteurizing vat/tank equipped with an agitator. The water is heated, while the agitator is kept in motion, to 38-43°C. Then the calculated amount of spray dried whole milk is slowly added at the point of agitation, and the mixture thoroughly agitated till it dissolves completely.
Special Powder Mixer equipment may be used for this purpose. The mixture is then pumped through a filter, pasteurized at 63°C for 30 minutes, and promptly cooled to 5°C or below until distribution.
Type # 5. Recombined Milk:
This refers to the product obtained when butter oil (also called dry/anhydrous milk fat), skim milk powder and water are combined in the correct proportions to yield fluid milk. The milk fat may also be obtained from other sources, such as unsalted butter or plastic cream.
Under the PFA Rules (1976), Recombined Milk should contain a minimum of 3.0 per cent fat and 8.5 per cent solids-not-fat throughout the country.
Merits:
(i) Helps in making up the shortage of fresh milk supplies in developing countries;
(ii) Helps prevent price rise of liquid milk in cities.
Method of Manufacture:
Flow Diagram of Manufacture:
Details of Manufacture:
A calculated amount of potable water is received in the pasteurizing vat/tank equipped with an agitator. The water is heated, while the agitator is kept in motion, to a temperature of 38-43°C. A proportionate amount of spray dried skim milk is slowly added at the point of agitation. When the water reaches a temperature of 43-49°C, another proportionate amount of butter-oil is added.
These constituents are thoroughly agitated till a homogeneous mixture is obtained. The mixture is then pumped through a filter and later pasteurized at 63°C for 30 minutes. It is then homogenized at the pasteurization temperature at 2500 psi single stage to ensure proper emulsification of the milk fat. The product is quickly cooled to 5°C, packaged and stored at 5°C or below until distribution.
Note:
Recombined milk was extensively produced under the ‘Operation Flood’ scheme in the four major cities of India, viz. Bombay, Calcutta, Delhi and Madras, during 1970-5, from the butter-oil and skim milk powder donated under the World Food Programme Project by the Food and Agriculture Organisation of the United Nations.
Type # 6. Toned Milk:
Toned Milk (also called Single Toned Milk) refers to milk obtained by the addition of water and skim milk powder to whole milk. In practice, whole buffalo milk is admixed with reconstituted spray dried skim milk for its production.
Under the PFA Rules (1976), toned milk should contain a minimum of 3.0 per cent fat and 8.5 per cent solids-not-fat throughout the country.
History:
Toned Milk is the brainchild of D. N. Khurody (India), who is also credited with coining its name. Under his auspices, it was first produced in 1946 in the Central Dairy of the Aarey Milk Colony and marketed in Bombay City. Soon other cities, notably Calcutta, Madras and Delhi started producing and marketing Toned Milk, which has become a permanent feature ever since of the market milk industry in India.
In the words of Mr Khurody- ‘By merely adding water to whole buffalo milk, both the fat and solids-not-fat content are reduced. But by adding skim milk powder to the mixture, solids-not-fat is ‘toned up’ or increased to the original level. As the product was neither whole milk nor standardized, a new name Toned Milk was given to it.’ (All skim milk powder was earlier imported.)
Merits:
(i) Increases the supply of milk. The buffalo milk initially used is increased by 100-150 per cent;
(ii) Reduces the price of milk, so as to reach lower-income groups of the population.
Method of Manufacture:
Flow Diagram of Manufacture:
Calculation:
Problem:
Given- 1,000 kg of whole buffalo milk testing 7.5% fat and 9.8% SNF; SMP testing 0.5% fat and 96.5% SNF; Toned Milk to contain 3.0% fat and 8.5% SNF.
Solution:
Let the amount of water required be W kg and SMP be S kg.
Amount of Toned Milk = (1000 + W + S) kg.
The following equations can be formed:
Details of Manufacture:
The calculated amount of potable water is received in the pasteurizing vat/tank equipped with an agitator. The water is heated while the agitator is kept in motion to 38-43°C. Then a proportionate amount of spray dried skim milk is slowly added at the point of agitation and the mixture thoroughly agitated till it dissolves completely.
A calculated amount of whole buffalo milk is now added and the mixture again agitated thoroughly till a homogeneous mixture is obtained. The mixture is then pumped through a filter, pasteurized at 63° for 30 minutes, rapidly cooled to 5°C, packaged and kept at 5°C or below until distribution.
Type # 7. Double Toned Milk:
Same as Toned Milk, except that under the PFA Rules (1976), Double Toned Milk should contain a minimum of 1.5 per cent fat and 9.0 per cent solids-not-fat throughout India.
Type # 8. Humanized Milk:
When whole cow or buffalo milk is so modified in its chemical composition that it resembles human milk, it is called Humanized Milk.
Type # 9. Miscellaneous Milks:
i. Filled Milk:
Same as Recombined Milk, except that the fat is derived from a vegetable source.
ii. Imitation Milk:
A product resembling milk but of non-dairy origin.
iii. Vegetable Toned Milk:
The milk protein of skim milk powder is substituted by vegetable protein isolated from groundnut. (Example- MILTONE of the Central Food Technological Research Institute, Mysore.)
iii. Soya Milk:
Made from soya bean by special patented processes.