TRADITIONAL DAIRY PRODUCTS

Lesson 5. CHEMICAL COMPOSITION; FACTORS AFFECTING QUALITY AND YIELD OF KHOA

Module 2. Khoa

Lesson 5
CHEMICAL COMPOSITION; FACTORS AFFECTING QUALITY AND YIELD OF KHOA

5.1 Introduction

Khoa contains fairly large quantities of muscle building proteins, bone forming minerals and energy giving fat and lactose. It has got, in concentrated form, most of the fat soluble vitamins and many water soluble vitamins contained in the original milk.

5.2 Chemical Composition of Three Varieties of Khoa

Table 5.1 Average chemical composition of three varieties of khoa (on product basis)

The fat content in all the three varieties shall not be less than 30 percent on dry matter basis as per FSSA rules.

Table 5.2 Physical quality of cow and buffalo khoa

5.3 Yield of Khoa

Generally 4 kg of buffalo milk or 5 kg of cow milk yield one kg of khoa. The yield of khoa depends on the following factors:

5.3.1 Type and quality of milk

Buffalo milk gives more yield than cow milk because of its higher fat and solids. Adulterated milk and low solids milk give lower yields.

5.3.2 Moisture content in khoa

Higher the moisture content in khoa, higher the yield and vice – versa. The yield of dhap variety of khoa is more than Pindi variety of khoa because of higher moisture content.

5.3.3 Losses during handling

Higher losses due to stickage of product and milk spillage losses during processing which will result in lower yields.

5.4 Factors Affecting Quality of Khoa

Higher amount of free fat (>60%) gets released in buffalo milk khoa than cow milk khoa. Higher free fat content contributes to soft body and oily or greasy appearance to buffalo milk khoa. Fresh milk is usually preferred for production of good quality khoa suitable for making sweets. Good quality khoa should have either a light yellow (if made from cow milk) or a dull white colour if made from buffalo milk), slightly heated flavour, but free from oiliness and acidic taste, smooth body and a compact mass of very small uniformly sized grains. It should not have visible water droplets or show sign of oozing of fat. When fresh should be able to produce a smooth homogenous paste on working, which indicates that it is suitable for sweet making.

5.4.1 Quality of milk

In India both cow and buffalo milks are used for manufacture of traditional dairy products depending on the availability and suitability of milk for a particular product. However, the quality of the products greatly depends on the type of milk used for their preparation. Yield of Danedar is and Dhap type of Khoa from buffalo milk is 24% and 25%.

a) Species of Animal: Buffalo milk is preferred over cow milk for khoa making because it yields a product with soft, loose body and smooth granular texture which is highly suitable for the preparation of sweets. The buffalo milk gives a greater out burn than that from cow milk. The average yield from buffalo milk is 21.6-23% and from cow milk it is 18.3-18.5% due to the higher T.S. Content in buffalo milk moisture content in khoa. Khoa from cow milk is of inferior quality due to its dry surface, sticky and sandy texture and salty taste (due to higher chloride and citrate content (Citrate buffalo milk 0.18%, cow milk 0.18% and chloride: buffalo milk 0.07% and cow milk 0.10%)) which is not considered suitable for manufacturing of best quality khoa based sweets.

b) Fat content in milk: A minimum fat level of 4% in cow milk and 5.5% in buffalo milk is essential for production of khoa with desirable body and texture and to meet the FFA requirements also. A lower fat content results in undesirable hard body and coarse texture in the finished product which is not suitable for good quality sweets preparation. The fat level higher than the minimum improves the quality of the final product. (The higher emulsifying capacity of buffalo milk fat due to the presence of higher proportion of butyric acid containing triglycerides (50%) than only 35% in cow milk fat and higher fat content in buffalo milk is responsible for smooth and mellowy texture of buffalo milk khoa)

c) Acidity of milk: Fresh sweet milk yields the best quality khoa, while developed acidity in milk produces an undesirable, coarse texture sour smell and bitter taste in to the khoa which is unsuitable for sweet preparation.

d) Presence of additives and adulterants: Neutralization of high acidic milk improves the texture, but does not improve the flavour of khoa. Further it gives saltish taste in the final product.

• Presence of colostrum in milk has a marked effect on the colour of khoa, which is deep yellow with cow colostrums. It also gives pasty texture in the final product making it not suitable for sweet making.

Adulteration of milk with water produces a brown khoa and a proportionate reduction in the yield. Texture and flavour of khoa are not affected much when adulterated with starch the physical quality of khoa is considerably affected. It develops a harder body and a pasty sticky texture not suitable for the preparation of confections.

• Speed of Stirring: The speed of stirring should be optimum. It depends on the type of machine/ method. In case of traditional method the optimum speed is about 100 rpm where as in continuous systems it depends upon the type of machine used (it is slightly more). The optimum speed of stirring prevents burning of milk solids and helps in developing desirable body and texture in khoa. Low speed results in to the burning of khoa. Higher speed makes the product pasty and sticky.

• Temperature of desiccation: To obtain good quality khoa, milk should be maintained at the boiling temperature till it reaches a paste consistency and then temperature is lowered to 88°C till the pat formation stage. The dehydration should be stopped when the pan contents starts leaving the pan surface and shows a tendency to stick together. Continued heating at higher temperature at advanced stage of khoa making results into undesirable flavour (cooked) and texture (hands dry). The colour of such product is also brown. Slow heating is not only more time consuming but also produces sandy texture and brown colour.

5.4.2 Homogenization of milk

Homogenization of cow/ buffalo milk produces a softer body in khoa, as against an homogenized milk. The khoa from homogenized milk also shows lower fat leakage, less browning, and a reduced patting tendency as compared to that obtained from unhomogenized milk.

5.5 Physico-Chemical Changes in milk during Khoa making

The changes in physico-chemical characteristics of milk during khoa making take place due to three actions. 1) concentration 2) heating and 3) Stirring and scraping

1) Change of state

The removal of moisture from milk results into concentration of milk solids. This eventually changes the state of milk from liquid to solid/ semisolid. All the constituents including lactic acidity increase in proportion to the degree of concentration. pH decreases.

2) Development of cooled flavour

Heating of milk causes changes in proteins resulting in the production of sulphydryl compounds by denaturation of whey protein particularly β-Lactoglobulin.

3) Coagulation of casein

Due to the combined action of heat and concentration coagulation of casein tends to increase logarithmically with milk solids concentration and forms a complex with denatured whey protein.

Convention of soluble calcium and phosphate to colloidal form and interaction between protein compounds.

Super-saturated solution of lactose: From a dilute solution in milk, lactose is present in khoa as a super-saturated solution. Most of the lactose is present as α-hydrate in khoa.

Free fat formation: (Free fat in khoa is 60% of the total fat in khoa, Cow khoa = 50% of the total fat). By vigorous stirring and scraping, the fat globule membrane ruptures, thereby releasing considerable amount of free fat in khoa.

The water dispenses as fine droplets in mass of the khoa.

Change in colour intensity: The colour of khoa becomes intense with brownish tinge due to formation of melanoiodins pigment. The browning reaction is maillard type reaction due to interaction between aldose group of lactose and free amino group of casein.

Increase in iron content: From 2 to 4 ppm iron content in milk, the iron content of khoa increases more than 100 ppm due to the incorporation of additional quantities of iron from the karahi and the khunti by vigorous scraping.