BY-PRODUCTS TECHNOLOGY

Module 2. Skim milk & its by-products

Lesson 5
CASEIN: CLASSIFICATION & SPECIFICATIONS

5.1 Introduction

Casein, the principal protein in milk, has been produced commercially for more than a century. Edible casein is a long established dairy by-product finding its use as an ingredient in many dairy and food products. The general development in technologies and the new uses in foods have ever increased the production and demand of this by-product. Its manufacture differs from that of non-edible casein (also called industrial casein) in that it is produced under sani-tary conditions. Further, during its manufacture, food grade chemicals are to be used and sufficiently heat treated to make it safe for human consumption. Appropriate National and International standards for this by-product call for rigorous control during its manufacture. The intensive investigation in manufacturing technologies over the years and the introduction of efficient plant designs, have immensely improved the technology of caseins.

5.2 Classification

5.2.1 Classification based on coagulant

5.2.1.1 Acid casein

Acid casein can be further classified as follows:

• Direct acidification with mineral acids: Hydrochloric acid casein, sulphuric acid casein etc.
• Lactic casein: Produced by growth of lactic starter culture.

5.2.1.2 Rennet casein

Rennet casein is obtained by using rennet as the coagulant.

5.2.2 Classification based on use

Based on use of casein, it can be classified as ‘edible casein’ or ‘industrial casein’.

5.3 Specifications

5.3.1 Standards for edible casein

There are a number of National and International standards for chemical and microbiological quality of edible casein.

5.3.1.1 National Standards

a) FSSAI (2011) Standards

According to Food Safety and Standards Authority of India (FSSAI - 2011) Standards, edible casein products mean the products obtained by separating, washing and drying the coagulum of skimmed milk. Edible acid casein means the product obtained by separating, washing and drying the acid precipitated coagulum of skimmed milk. Edible non-animal rennet casein means the product obtained after washing and drying the coagulum remaining after separating the whey from the skimmed milk which has been coagulated by non-animal rennet or by other coagulating enzymes. The products shall be white to pale cream or have greenish tinge; free from lumps and any unpleasant foreign flavour. They may contain food additives permitted in these regulations. They shall conform to the microbiological requirements prescribed in Annexure - I and shall conform to the requirements as given in Table 5.1.

Table 5.1 FSSAI (2011) compositional standards for edible casein

b) BIS Standards

According to BIS Standards, casein shall be prepared from skim milk of either cow or buffalo or a mixture of both. Casein shall be nearly white or pale cream in colour and shall have no undesirable odour or any foreign matter. It shall be free from any added colour or preservative. The size of the particles shall be such that 100 percent by weight of casein shall pass through 500-micron IS Sieve. The material shall also comply with the requirements given in Table 5.2.

5.3.1.2 International Standard (FIL-IDF 45, 1969)

The International Standard (FIL-IDF 45, 1969) defines the quality of edible acid casein (Table 5.2). Dry casein is usually in the form of a coarse powder of white to cream-yellow colour that has the odour and flavour of pure milk.

Table 5.2 National and International standards for edible acid casein

5.3.1.3 European Communities Standards

According to official standards of European countries, ‘edible rennet casein’ means edible casein obtained by precipitation using the technological adjuvants listed in Table 5.3 (d) which comply with the standards laid down in Table 5.3.

Table 5.3 European Communities Standards (237/30, 1983) for edible rennet casein

5.3.2 Standards for industrial casein

The International Standard (FIL-IDF 45, 1969) defines the quality of casein destined for industrial use (Table 5.4). The mineral content is substantially lower in acid casein than in casein coagulated with proteolytic enzymes.

Table 5.4 International Standards (FIL-IDF 45:1969) for quality of industrial casein

Selected reference

International Standards 1969. FIL-IDF 45, Brussels, Belgium.