Types of Milk (skimmed, toned and homogenized)

Milk:

•  Milk may be defined as the normal secretion of the mammary glands of mammals. OR
•  Milk may be defined as the whole, fresh, clean, lacteal secreation obtained by the complete milking of one or more healthy milch animals, excluding that obtained within 15 days before or 5 days after calving or such periods as may be necessary to render the milk practically colustrum-free, and containing the minimum prescribed percentages of milk fat and milk-solids-not-fat.
• In India, the term ‘milk’, when unqualified, refers to cow or buffalo milk, or combination of the two.

Types of Milk:

1.Skimmed milk:

• Skimmed milk is also know as  skim milk
• Skimmed milk or skim milk  is made when all the milk fat is removed from whole  milk.
• It tends to contain around 0.1% fat. 

      Advantage:

•        The most beneficial factor of skimmed milk powder is that it is fat free.
•        Skimmed milk contains very low portion of fat or no fat at all and is very good for maintaining a healthy heart and slim body. Fat occupies large space in your body and hinders the functioning of other nutrients. Using of skimmed milk powder leaves more space for other nutrients in your body and keeps your body healthy.
•       Skimmed milk powder is suitable for lowering your blood cholesterol level thereby protecting your body from cholesterol problems.
•       Moreover, usage of skimmed milk powder may protect your body from diseases as compared to raw milk which may carry some bacteria causing illness along with it.

Disadvantage

•      The most disadvantageous factor of skimmed milk powder is that it contains oxidized cholesterol which is not good for health. This oxidized cholesterol is generated during the heating process of raw milk while producing the skimmed milk powder.
•      Another minus point is that skimmed milk powder is deficient in vitamins A and D that are needed for absorbing protein and calcium. So the body needs to take these vitamins from its reserves to make use of the skimmed milk thereby depleting its reserves and weakening your body.
•     The pasteurization and powder making processes of milk destroy all nutrient values of the natural milk thereby making the skimmed milk powder very deficient in its nutritional values as compared to original raw milk or semi skimmed milk.

Process of Manufacture Skimmed Milk Powder:

•The fat free (skim) milk obtained from cream separator is collected in storage tanks.

•It is heated to a temperature of about 85 degree C to 90 degree C and is pumped on the surface of the steam heated revolving metallic drum.

•The steam pressure in the drier should be about 69 lb/sq. inch (12 degree C temp.).

•The milk is dried into a thin film on the surface of roller drum.

•It is removed by means of stationery steel scrapper, which is attached from the roller and collected through screw type burrer.

• It is then pulverized to desired mesh and packed.

Generalized scheme for production of milk powder:

Raw milk

Receiving, selection and clarification

Storage of chilled milk

Standardized milk

Heat treatment

Concentrate milk by evaporation

Homogenization

Drying

Packaging of milk powder

Storage

2)Toned Milk (also called Single Toned milk):

Definition

•       Toned milk refers to milk obtained by the addition of water and skim powder  to whole milk
• .        (Skim Milk Powder is obtained by removing water from pasteurized skim milk. It contains 5% or less moisture (by weight) and 1.5% or less milkfat (by weight) and a minimum milk protein content of 34%. Skim Milk Powder is classified for use as an ingredient according to the heat treatment used in their manufacture.
•       In practice, whole buffalo milk is admixed with reconstituted spray dried skim milk for its production .
•       Under the PFA  (Prevention of Food Adulteration Act) Rule of 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 (an idea or invention which is considered to be a particular person's creation.) 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 sice of the market milk industry in India.
—  In the words of Mrs. Khurody:”By merely adding water to whole buffalo milk, both the fat and solid-not-fat ( the substances in milk other than butterfat and water; abbreviated SNF. They include casein, lactose, vitamins and minerals which contribute significantly to the nutritive value of milk)  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 powder was earlier imported.)

Merits
—  Increase the supply of milk.The buffalo milk initially used is increased by 100-150 per cent.
—  Reduces the price of milk, sa as to reach lower-income groups of the population.
 

Method of Manufacture:

—  Flow diagram of manufacture:

 Receiving milk in pasterizing vat ( pasterizing vat, It is a gentle process where the milk is introduced in a heated vat at 145°F (63°C) for half an hour followed by rapid cooling to 39°F (4°C). It is also known as holding method as the milk gets heated for 30 minutes in special equipment.)

                             
           Pre-heating (28-43⁰C)

                            
   Addition of skim milk powder and mixing , and addition of whole buffalo milk and mixing

                            
                Filtration

                            
      Pasteurization (63⁰C/30min.)

                           
              Cooling (5⁰C)

                         
      Packaging and storage (5⁰

                          

              Pre-heating (35-40 ⁰C)

(3) Homogenized Milk:

Definition

Ø  According to the United states Public Health Service, Homogenized milk is milk which has been treated in such a manner as to insure breakup of the fat globules to such extent that after 48 hour’s quiescent storage no visible cream separation occurs on the milk and the fat percentage of the milk in the top 100ml.of milk in a quart bottle.or of proportionate volumes in containers of other sizes, does not differ by more than 10 per cent of itself from the fat percentage of the remaining milk as determined after thorough mixing.(In efficiently homogenized milk , the fat globules are subdivided to 2 microns or less in diameter.)

Ø  Note. ( Homogenization refers to the process of forcing the milk through a homogenizer with the objects of sub-dividing the fat globules.)

Merits and Demerits:

—  Merits

1. No formation of cream layer/plug
2. Fat in milk does not churn (to form form) due to rough handeling or excessive agitation.
3. Better adapted for bulk dispensing, mixing not necessary.
4. More palatable (pleasant to taste )due perhaps to brighter appearance, heavier body and richer flavour.
5. Produces soft curd and its better digested, hence recommended for infant feedings
6. Less suspectible to oxidized flavour development

• Demerits

1. Increased cost of production
2. Returned homogenized milk difficult to salvage(rescue,save,Recover,get back) , fat recovery is a problem
3. Sediment appears to a greater degree
4. Curdling (separate or cause to separate into curds or lumps. )in cookery.
5. More susceptible to production of activated or sunshine flavours defect
6. Greater tendency for milk ‘seepage’(the slow escape of a liquid or gas through porous material or small holes)through bottle cap.

Factors influencing homogenization:

(A) Temperature of homogenization :

—  The milk should, at the time of homogenization, be at  a temperature above the melting point of fats ,viz, above 33⁰C(91 ⁰F).This is because fat should be in the liquid state for proper sub-division

—  The enzyme lipase should be inactivated, preferably prior to homogenization or immediately afterwards . This can be achieved  by heating the milk to a temperature of 55 ⁰ C (131 ⁰F) or above.

—  In routine practice, the milk is heated to 65-70 ⁰C ( 149-158 ⁰F) for homogenization.(The  danger zone for lipase activity ,viz. temperature 38-49 ⁰C (100-120 ⁰F),should be avoided during or after homogenization.)

(B) Pressure of homogenization

—  In a single stage, up to 6 per cent fat milk , usually 2000-2500 psi pressure is sufficient.

—  Higher pressure may increase the tendency for the milk to curdle when cooked, due to increased destabilizing effect on milk-proteins.

—  For liquid products with more than 6 per cent fat, two-stage homogenization is needed to prevent fat clumping: 2000psi at the first stage and 500 psi at the second.

Sequence of various processes involved in production of homogenized milk:

The possible sequence are:

1.  Clarification, Pre-heating, homogenization, pasteurization, cooling.

2.   Clarification, Pre-heating, pasteurization, homogenization, cooling.

3.   Pre-heating, homogenization, Clarification, cooling.( Recommended under Indian conditions).

4.   Pre-heating, Clarification, homogenization, pasteurization, cooling.

5.  Pre-heating, Clarification , pasteurization, homogenization, cooling.

Note.

 The main consideration are :

1. All homogenized milk must be pasteurized either prior to homogenization or immediately after .

2.  The homogenized milk should preferably be clarified after homogenization.

3.  Under Indian conditions, the sequence underline above is desirable , so as to avoid post-pasteurization contamination.

Method of Manufacture: (Flow diagram of manufacture)

                                            Receiving milk

                                                  
                                    Cooling to 5⁰C and bulk storage

                                                 
                              Filteration/Clarification

                                                
                                   Cooling to 5 ⁰C

                                                
                                       Standardizing and storage (5 ⁰C)

                                                    
                                Pre-heating (60 ⁰C)

                                                                                 

                              Homogenization (2500 psi) ( 60 ⁰C)

                                               

                               Pasteurization ( Holder or HTST)

                                                   

                                      Cooling (5 ⁰c)
                                                  

                                             

                                            Storage (5 ⁰C
                                

References:

1. Clarence Henry Eckles, Willes Barnes Combs, Harold Macy (1943). Milk and milk products, 4th Ed. McGraw-Hill book Company, Incorporated.

2. Sukumar. De (2001). Outlines of Dairy Technology. 1st Ed. Oxford University Press Delhi.

Whole Milk

This is also known as ‘regular’ milk that consists of about 3.5% of fat content. 

The fat percentage typically ranges somewhere between 3.25% and 3.5%.

 The primary reason why it is called ‘whole’ milk is it is comparatively purer than most other types of milk, and also because of its fat content.

Whole milk is considered to be very thick, creamy, and rich, and pairs perfectly with a bowl of oatmeal for breakfast in the morning. 

In the words of the Dairy Council of California, the whole is milk is basically “the way it comes from the cow before processing.”

Although it is pasteurized and probably even homogenized, the ratio of fat to milk in whole milk is the same as raw milk.

Double toned milk

Double toned milk is made by mixing whole milk with skimmed milk or skimmed milk powder. The whole buffalo milk is combined with skimmed milk to get double toned milk. 

The milk is low in fat and calories and ideal for people trying to lose weight.

Double toned milk has around 1.5 per cent fat. It is a great option for people suffering from heart disease.

The milk is easily digestible, is rich in vitamin D and has fewer calories as compared to toned milk. 

One cup double toned milk has 114 cal, while one cup toned milk has 150 cal.

Dehydrated Milk:

milk dehydrated to about 5 percent of moisture by evaporation. — called also milk powder, powdered milk.

Powdered milk, also called milk powder or historically dried milk, is a manufactured dairy product  made by evaporating  milk to dryness. 

One purpose of drying milk is to preserve it; milk powder has a far longer   shelf life  than liquid milk and does not need to be  refrigerated ,due to its low moisture content. 

Another purpose is to reduce its bulk for the economy of transportation.

  dry  buttermilk, dry whey products and dry dairy blends. Many exported dairy products conform to standards laid out in Codex Alimentarius. Many forms of milk powder are traded on exchanges.

milk dehydrated to about 5 percent of moisture by evaporation. — called also milk powder, powdered milk. — compare evaporated milk.

Dehydrated Milk:

The milk  from which about 95 percent of the moisture   has been evaporated is called dehydrated milk.

Also called: dried milk, milk powder, powdered milk

Powdered milk, also called milk powder or dried milk, is a manufactured  dairy product made by evaporating milk to dryness  .

 One purpose of drying milk is to preserve it; milk powder has a far longer shelf life  than liquid milk and does not need to be  refrigerated  due to its low moisture content. 

Another purpose is to reduce its bulk for the economy of transportation. 

Reference:

https://www.homestratosphere.com/types-of-milk/#Whole_Milk

https://timesofindia.indiatimes.com/life-style/health-fitness/diet/skimmed-milk-vs-double-toned-milk-which-is-better-for-weight-loss/photostory/81335155.cms?picid=81335164

https://en.wikipedia.org/wiki/Powdered_milk

https://en.wikipedia.org/wiki/Powdered_milk