Quality Control of Milk Refers to Characteristics that Enhance its Acceptability

Sub :  Quality Control of Milk

Milk ranks high among other foods and is considered as the most perfect food for human from birth to senility as it is not only has good sensory properties and all nutrients required for the body for rapid growth but also could prevent or reduce risks of many nutritional deficiency diseases. It contains all the essential nutrients such as protein, carbohydrate, fat, minerals and vitamins which are required for human health. Moreover dairying has become an important secondary source of income for millions of rural households engaged in agriculture. The success of the dairy industry has resulted from the integrated co-operative system of milk collection, transportation, processing and distribution maintaining the quality.

Quality control: Quality refers to a combination of characteristics that enhance the acceptability of a product. As Milk is nutritious and wholesome food for a large section of society, ensuring quality of milk is an important aspect to safeguard public health. Quality control of milk is a broad term, which relates to the chemical, physical, technological, and bacteriological and aesthetic characteristic of milk. Quality control concerns the activity of procedure that ensure the maintenance and continuity of the specifications and standard of the products within the prescribed tolerance limits during all stages of handling, processing, preparation, packing presentation storage and distribution. It also further ensures that all the original and desirable characteristics are retained during these operations and remained unaltered until the product reaches the consumer.

Compositional quality

The composition of milk varies with breed of the milch animal, species, stage of lactation, feed season, disease conditions of udder and variation in milking.

Bacteriological quality

Milk is a nutritious food for human beings. It also serves as an ideal medium for the growth of microorganism particularly bacteria. The growth of the microbes in milk is dependent upon both intrinsic as well as extrinsic factors. The basic object of microbiological quality control is to provide fluid milk from disease free udders to milk processing plant to manufacture wholesome milk and milk products. Microbiological quality assumes significance because the method of mass collection and distribution of milk provides ample opportunities for the contamination and transmission of pathogens over a wide area. Micro organisms are found everywhere on animal and people, in the air, in the soil, in water and in milk. Good sanitary practices throughout the entire milk chain from milking through processing to packaging result in safe milk of a good quality.

Contamination and control measures at

• Animal shed and environment: the milking area of the shed needs special hygienic attention. The floor of the milking place should be made of concrete so that mud, urine, faeces and feed residues can be removed. It should be swept with clean water before and after each milking. Facilities should be created for an adequate and sufficient supply of safe and potable water proper drainage.

• The animal: The animal itself is an important source of contamination. Care and management of the animal and its health is the starting point for clean milk production. The skin of the animal provides a large surface for possible contamination. Dung, urine, uterine discharge, dirt, dust and hairs can pass millions of bacteria, when it drops from the skin and udder into the milk. Long hairs on the flanks, hind legs, tail and udder should be clipped at frequent intervals. Grooming the animals regularly can help to keep hair and dust away from milk.       The udder will be grossly contaminated with bacteria, even when it appears visibly clean.  If the is suffering from infections such as mastitis, the milk will contain harmful pathogenic micro-organisms. Milk from diseased animals should be kept separate and disposed of safely. It is advisable to test the foremilk at each milking with a strip cup.

• Milker and milking routine: In case of hand milking, the danger of contamination coming from the milker is higher as compared to machine milking. As the milker moves from one animal to the next, he/she can transfer pathogenic micro-organism to all the animals in the herd. Therefore the have trimmed and clean nails. He/she should wash hands with soap and water before milking and dry them with a clean towel. The milker should always cough or sneeze away from the milking pail. A good milking routine prevents contamination of the milk. Consistent milking at regular intervals using a fast but gentle technique, which empties the udder completely, are important aspects. Feeding roughage at the time of milking should be avoided, as dust and/or smell easily contaminates the milk. If calves are suckling, the calf should be allowed to suckle at the beginning of the milking.The udder and teats should be washed and massaged for at least 30 seconds using clean water and a cloth of individual paper towels. It is advisable to add disinfectant to a bucket of water. If udder cloths are used, rinse them regularly in between milking different cows. After each milking wash and disinfect the cloth and hang it to dry.Foremilk should be examined and abnormal milk should be discarded. The foremilk should not be allowed to run on the floor as this increase the danger of contamination. During milking all milk should be drawn directly into the pail as fast as possible. The milker should not wipe his/her hands on the body of the animals or on his own body. After milking, the teats can be dipped or sprayed with a gentle antiseptic solution. Filtering or straining the milk removes visible dirt but not the bacteria from the milk. Bacteria will pass through the filter. Cloth filters must be properly washed and dried in the sun after each use.

• Milking equipment: All dairy utensils such as buckets, milking cans and filters should be thoroughly cleaned immediately after use. Any milk residues on the equipment will allow microorganisms to grow rapidly. Also ancillary equipment, including foremilk cups and udder cloths, must be cleaned and disinfected effectively.

• Cleaning and disinfection: First wash the utensils with hot water and a detergent. A clean brush with good bristles should be used, then rinse with clean water. After that the equipment has to be disinfected with either hot water or with a disinfectant, do not try the utensils with a piece of cloth, but drain them immediately after washing. Bacteria will not multiply in dry conditions but water lodged in milking equipment will, in the prevailing temperatures, provide conditions for massive bacterial growth. To facilitate drainage of wash water put the utensils in an inverted position on a drying rack, preferably in the sun.

• Storage and transport: Milk should be stored in clean containers with a lid and kept in a cool and shady place where the danger of contamination is minimal. Transport should take place in clean containers as well. It is important to keep the transport time to a minimum and avoid violent movement of the milk. Milk must reach the milk Collection Centre quickly, ideally within 2-3 hours after milking. Preferably, the milk is cooled to 4 ⁰C and kept at that temperature until it is processed.