Module 7. Processed milk varieties

Lesson 35

35.1 Standardized Milk

In this variety, milk fat and SNF content has to be adjusted to a certain predetermined level. Standardization can be done by partially skimming the fat in the milk with a cream separator or by admixing with fresh or reconstituted skim milk in proper proportions. Under the FSS Rules-2011, standardized milk for liquid consumption should contain a minimum of 4.5% fat and 8.5% SNF throughout the country. Standardized milk may be marketed as such or used for making certain milk products.

35.1.1 Advantages

1. Ensures milk of practically uniform and constant composition and with good nutritive value to the consumers.

2. The surplus fat can be converted into butter and ghee.

3. Possible to reduce the cost of milk

4. More easily digestible because of reduced fat content.

35.1.2 Disadvantages

The initial reaction of the consumer may be that standardized milk is ‘thinner’ than the whole milk.

35.1.3 Method of preparation

The preparation is shown in the form of a flow chart below (Fig. 35.1).

Fig. 35.1

Fig. 35.1 Flow diagram for preparation of standardized milk

35.2 Flavoured Milk

Adding delectable flavour and befitting colour to milk makes it highly palatable and increases the sale of milk. When the term ‘milk’ is used, the product should contain a milk fat content at least equal to the minimum legal requirement for specific type of market milk. But, when the fat level is lower (i.e. 1-2%), the term ‘dairy drink’ may be used. The purpose is:

Tto make milk more palatable to those who do not relish it as such

• To stimulate the sale of milk and

• To put skim milk to profitable use

The main types of flavoured milk are

Chocolate milk/drink

• Fruit flavoured milk/drink

• Sterilized flavoured milk/drink

35.2.1 Chocolate milk/drink

In chocolate milk/drink, the following formula may be used:

1. Cocoa powder - 1 to 1.5%

2. Sugar - 7 to 9%

3. Stabilizer - 0.2% (Sodium alginate can be used)

4. Fat level: Milk – legal standards of milk

Dairy drink - minimum 2% fat Method of manufacture

The milk on receipt is standardized, preheated to 35¬-40°C and filtered/clarified followed by preheating to 60°C and homogenization at 175 bar (2500 psi). To the warm milk, the desired amounts of cocoa powder, sugar and stabilizer are slowly added and stirred so as to dissolve them properly. The cocoa powder may also be added in the form of syrup, and the stabilizer in the form of solution. Homogenization can also be done after addition of cocoa and sugar. But, this has the effect of increasing sedimentation. Stabilizer is usually added to delay or prevent setting of cocoa particles; it also helps in the prevention of cream rise. The mixture is then pasteurized at 71°C/30 min, cooled rapidly to 5°C, bottled and kept under refrigeration (5°C) until used. The bottles are invariably inverted up and down a few times before consumption.

35.2.2 Fruit flavoured milk/drink

Permitted fruit flavours/essences together with permitted (matching) colours and sugar are used. The method of preparation is similar to that used for chocolate milk/drink. The common flavours used are strawberry, orange, lemon, pineapple, banana, vanilla etc. Pure fruit juices or syrups can be satisfactorily combined with milk to form milk shakes. However, in order to obtain good results, the following precautions should be taken:

1. No acid (citric or tartaric) should be added to the fruit syrup, as this may cause curdling. The pH of the milk-syrup mixture should be about 5, which is safe from the curdling point of view.

2. Excessively sweet syrups should be avoided. The best sugar content of syrup is 45-55%.

3. Add 1 part of fruit syrup to 5 parts of milk. The fruits, which give good results, are strawberries, orange, lemon, pineapple, blackberry, raspberry and black currant.

4. Care should be taken to see that there is a pleasant blend of sweet fruits and milk flavours.

35.2.3 Sterilized flavoured milk

This combines the advantages of both sterilized and flavoured milk/drinks. The method consists of all the steps indicated in the chapter on ‘sterilization’. In addition, in between clarification and filling, flavour or essence, permitted (matching) colour and sugar (syrup) are added and mixed into the milk (Fig. 35.2).

Fig. 35.2

Fig. 35.2 Manufacture of sterilized flavoured milk

35.3 Reconstituted Milk

Reconstituted milk may be prepared either from skim milk powder (SMP) or whole milk powder by the addition of water. The composition especially fat:solids not fat ratio is adjusted equal to that of fresh skim milk or fresh whole milk. Whole milk powder possesses problems in reconstitution because of poor wettability. Therefore, reconstitution should be done with care. The temperature of water should be between 40-45°C. After reconstitution, it should be held for sufficient time, preferably for one hour, for proper hydration of powder particles. For greater convenience, instant powder in which wettablity is increased by agglomeration, may be used. When skim milk powder is to be used after reconstitution for extending the fluid milk supply, e.g. in preparing recombined or toned milk, low heat SMP should be the choice. Reconstitution equipments involve the use of high speed agitators creating a vortex or a ventury type mixer and pump to speed up dispersion and solution of powder. Preparation of whole milk from whole milk powder after reconstitution is not as common as reconstituted skim milk because of certain special problems. Whole milk powder has poor wettability due to presence of fat, which is hygroscopic to water. The shelf life of whole milk powder is also limited.

35.3.1 Advantages

1. It helps in making up the shortage of fresh milk supplies in developing countries.

2. It is useful for the armed forces posted at far-off places that are difficult to reach.

35.3.2 Method of manufacture

A calculated amount of potable water is received in the pasteurizing vat/tank equipped with an agitator. The water is heated to 38-43°C, while the agitator is kept in motion. A calculated amount of skim milk powder (for reconstituted skim milk) or whole milk powder (for reconstituted whole milk) is slowly added at the time of agitation and the mixture is thoroughly agitated till it dissolves completely. Special powder mixture equipment may be used for this purpose. The mixture is, pumped through a filter, homogenized (in case of reconstituted whole milk), pasteurized at 63°C for 30 min and promptly cooled to 5°C or below until distribution (Fig. 35.3).

Fig. 35.3

Fig. 35.3 Manufacture of reconstituted milk

Reconstitution is usually done by:

• Funnel or ventury system.

• Tri-blender or dry material-liquid blender system. Funnel or ventury systems

In this system, the water flows through a pipe to a jet which increases the velocity of the water flow. At the time of outlet from the jet, the powder flows from the hopper which is connected with the pipe into the high velocity stream of water. The jet acts as a ventury and creates a little vacuum to suck the powder from the hopper. The pipeline then returns to the holding tank so that the liquid circulates in the system until all the powder has been satisfactorily dissolved. A high speed centrifugal pump is used for re- circulation. Tri-blender or dry material-liquid blending system

In this system, thorough mixing of powder with water takes place in a centrifugal pump as the powder directly falls on to the pump impeller. This system is found to be most effective. The reconstituted skim milk is immediately chilled and stored.

35.4 Recombined Milk

This refers to the product obtained when butter oil (also called anhydrous milk fat), skim milk powder and water are combined in the correct proportions to yield fluid milk. Fat may also be obtained from other sources, such as unsalted butter or plastic cream. The acceptability of recombined milk is influenced by the quality of anhydrous milk fat. Recombined milk serves as a mean of supplying fluid milk in non-dairy areas. The recombining process offers several advantages. It reduces transport cost, eliminates refrigeration, and lowers packaging cost besides helping in the development of local industries. The main market for recombined milk and milk products is in developing countries, where they make up for the milk shortages and also find increasing utilization in emerging situations.

35.4.1 Legal definition

Under the FSS Rules (2011), recombined milk shall contain a minimum of 3.0% fat and 8.5% SNF throughout the country.

35.4.2 Advantages

• Help in making up for the shortage of fresh milk supplies in developing countries, especially in the lean seasons.

• Help to prevent the rise of the price of liquid milk in cities.

35.4.3 Recombination process

The process for preparing recombined milk is given in Fig. 35.4.

Fig. 35.4

Fig. 35.4 Recombination process Mixing of butter fat

The source of butterfat is usually butter-oil or unsalted white butter. The steps involved are:

1. Butter-oil tins are heated to above 50 to 55°C in a tank containing hot water with steam to liquefy the butter-oil.

2. The tins are opened or a few big holes are made on the lids.

3. The liquefied butter-oil is emptied out in the butter vat thoroughly.

4. Butter-oil is pumped to the butter-oil storage tank and heated to about 60 to 65°C.

The butter-oil is then injected into the milk stream at a speed set by a variable speed positive pump immediately prior to the homogenizer, which is connected to the pasteurizer. The milk-butter-oil mixture is homogenized by a two-stage homogenizer at 140 and 35 kg/cm2. It is then pasteurized and stored. Blending with reconstituted milk

Pasteurized reconstituted skim milk in predetermined quantity enters the storage tank containing the previously processed milk batch (with butter-oil) and are blended. Final standardization is done so as to obtain the desired level of fat and SNF contents.
Last modified: Wednesday, 10 October 2012, 5:18 AM