Raw Milk Quality

“ The FSSAI have not so far set any standard for raw milk quality in terms of microbiological properties. The good animal husbandry practices used for dairy animals will ensure low bacterial counts and reduce the risk of pathogens in raw milk. Another dimension to quality of raw milk is related with the feeding practices for dairy animals. It is often, observed that feed and fodders carry heavy amounts of pesticide residues and contaminants from moulds which impact the safety of milk. Use of all chemicals and veterinary medicines should be made according to technical directions and as prescribed by the veterinarians. This will prevent the occurrence of chemical and veterinary drug residues in raw milk. Sediment in milk is indicative of poor hygienic milking procedures allowing soil and other extraneous matter to enter the milk.

Good quality of raw milk is required to ensure food safety for the consumers, maintain animal health and the environment to manufacture high quality dairy products for distribution.

Fresh milk from healthy animal contains relatively low number of bacterial counts (1000 cfu/ml) which may increase up to 100 fold in three hours of storage at ambient temperature depending upon the initial microbial load and the temperature of storage. High microbial population in milk would lower the methylene blue reduction time up to 30 min. Storage of raw milk at low temperature is a pre-requisite practice to control the growth of spoilage bacteria.

Pseudomonas sp constitutes less than 10% of the total viable flora but with its short lag phase, it emerges as the most significant psychrotrophs in both raw and pasteurized milk. Milk samples collected from milk vendors indicated abnormally very high microbial load. Emphasis should be given not only to hygienic milk production but also to the minimisation of retention period of raw milk at refrigerated temperature and to process the milk at the earliest to ensure safe milk supply with good flavour and extended shelf life. Once raw milk becomes defective it can not be improved during processing. Low quality raw milk is often offered very low price. It may be noted that most of milk coming to dairies has a bacterial population of a few million per ml. Microbiological analysis of raw milk examined under Indian conditions indicated the presence of several kinds of pathogens like Coliform, Str. Aureus, E-coli, Salmonella typhi and many others.

Although bulk milk coolers have been installed at some milk collection and chilling centres by many dairy plants in India but they have not brought much change in raw milk quality because of lack of potable water and workers not adhering to standard operating procedure for maintenance and operation of the cooling plants. Hot water is not available in adequate quantities for cleaning and sanitization. Cleaning agent like caustic soda is circulated with cold water or with luke warm water. It is important that raw milk is produced and handled under clean conditions that do not deteriorate its quality. There are many factors that can influence the quality of raw milk. Unhealthy dairy animals have the potential to produce milk of low quality. Mastitis, for example, is an infection of udder which is most common animal health problem caused by bacterial infection. Mastitis causes an increase in milk somatic cells counts. The Food Safety and Standards Authority of India have not so far set any standard for raw milk quality in terms of microbiological properties. Quality defects are caused by the enzymes associated with the growth of microorganisms and by the presence of somatic cells. The enzymes break down proteins, fats and other milk components leading to flavour defects such as bitterness and rancidity in milk and other milk products made therefrom.

Milk secreted from the udder of a healthy animal is always low in bacterial counts. However, bacteria can grow at logarithmic rate due to insanitary milking methods, inadequate cleaning of milking utensils and cans, and poor cooling facilities.

Milk and milk products, because of their chemical constituents, form a good medium for growth of micro-organisms. They can support multiplication of health threatening microorganisms, such as Salmonella, E-coli, Listeria, Campylobacter, Staph aureus, Bacillus cereus, Yersinia and Tuberculosis, etc. Not only the presence of pathogenic organisms and their toxic metabolites but also the other spoilage microbial species and non-microbial substances may cause adverse effect on food quality and safety during primary production, collection, chilling, transportation, processing packaging and distribution. Dairy products are frequently involved in a number of food borne illnesses all over the world. More than 200 food-borne illnesses have been recognised, and most of them for diagnosis require very specific laboratory facilities and standard laboratory practice.

Food borne illnesses are a major cause of gastrointestinal troubles world over. The reported cases of such illnesses are believed to represent only a small fraction of the people who actually fall ill after eating contaminated food. It may, however, be stated that the impact of morbidity and mortality from food-borne illnesses is quite substantial. Expressed in monetary terms, the costs of human illness, value of lives shortened through death, lost productivity, pressure and constraints on medical care and public health systems, recalls and destruction of food, loss of sales and legal settlement will cost many billion dollars.

The good animal husbandry practices used for dairy animals will ensure low bacterial counts and reduce the risk of pathogens in raw milk. In India, animals do not have discrete housing or dairy premises with concrete dairy floors which are easy to clean before after milking. Barns are also laden with excreta (like dung, urine and crop residues) but they also harbour flies, insects and pests. They all lead to some kind of chemical, physical and bacterial contaminations.

Another dimension to quality of raw milk is related with the feeding practices for dairy animals. It is often, observed that feed and fodders carry heavy amounts of pesticide residues and contaminants from moulds which impact the safety of milk. Feeds contaminated with moulds carry significant amount of aflatoxins which are secreted into milk. The traceability of pesticides and contaminants found in feeds and fodders is a very problematic issue. Wherever possible, milk producers must be trained in good agricultural and animal husbandry practices to manage physical facilities for cultivation and storage of green as well as dry roughages. The quality of concentrate feeds must be regularized by the cattle feed manufacturing companies. Manufacturers of concentrate mixtures should be advised to ensure that the safety and quality of feeds is assured and no contaminants are present in the feed mixes.

Use of all chemicals and veterinary medicines should be made according to technical directions and as prescribed by the veterinarians. This will prevent the occurrence of chemical and veterinary drug residues in raw milk. Animals that produce milk need to be healthy and covered under effective health care programme. All animals must be vaccinated as recommended by the veterinary practitioners to build resistance against known diseases. Wherever possible, access should be limited to people, domestic and wild pet animals to prevent entry of diseases. Sick animals should be isolated and milk from such animals should be segregated. The cleaning and sanitization of milking utensils should be done in such a manner that contamination does not come from the utensils.

Milk production should be managed in an environmentally sustainable manner. Buildings and surroundings should be made to minimize the production of pollutants and by implementing practices to reduce, re-use or recycling the farm wastes which would cause minimum environmental impact. We must ensure that dairy operations are appropriate to present a positive image of dairy farming among the countrymen. Care should be taken to ensure that dairy operations do not impact their neighbours by controlling dust, smell, lights, noise, flies or other known nuisances.

Good dairy farming practices will help to manage the social and economical risks as the business provides lot of socio-economic benefits to farming families.

Sediment in milk is indicative of poor hygienic milking procedures allowing soil and other extraneous matter to enter the milk. To reduce the sediment in milk, the cleanliness of the hind quarters of animal before milking is important. There should be no scope for added water in milk whether intentionally or unintentionally. Added water can be detected in milk by measuring the freezing point. Added water in milk will not only reduce the percent values for fat and SNF but also reduce the sweetness and normal taste of milk besides, influencing the product yield. Selective plating or bacteriological culturing may be useful in identifying the source of high bacterial counts in milk. In any case, consumption of raw milk should be prohibited as numerous epidemiological outbreaks and even deaths have been reported. Total control of various factors affecting the microbiological quality of raw milk and hygienic milking practices for quality improvement will be necessary.