Milk Production & Food Safety

Mahendra Pal & Mridula Devrani
Mahendra Pal & Mridula Devrani

Globally, there are over 264million dairy cows, which produce around 600 million tons of milk each year. The total milk production from cows, buffaloes, goats, sheep, and camels is estimated around 703,996,079 tons annually.

As the health of dairy animals is of paramount importance for producing safe milk, it is highly imperative to appoint qualified and experienced veterinarian, the main custodian of animal health, for the de-worming, vaccination and treatment of animal diseases.

Hygienic milk handling includes using clean equipment, maintaining a sanitary milking environment, observing good personal hygiene, preserving the quality of milk during storage and transportation to the Since ancient times, milk is considered as a versatile commodity, which is consumed by all age groups, both sexes, every religion, in all seasons, and rural and urban inhabitants of the world. Milk is flooded with several nutrients such as proteins, fats, carbohydrates, vitamins and minerals, which are imperative to sustain life, generate energy, promote growth and maintain health. Globally, there are over 264 million dairy cows, which produce around 600 million of milk each year.

The total milk production from cows, buffaloes, goats, sheep and camels is estimated around 703,996,079 liters annually. The economy of many nations including India is mainly based on agriculture and animal husbandry wherein milk production plays a very important role. India is ranked first in production of milk in the world followed by the United States, and China. The total milk production in India has increased from55.6 million tonnes in 1991-1992 to 165.4 million tonnes during 2016-2017.

In the recent years, the dairy industry has acquired very good growth in India and elsewhere. In India, per capita availability of milk has improved from178 grams in 1991-1992 to 355 grams in 2016-17. Furthermore, the income of Indian dairy farmers is augmented by 23.77percent in 2014-17 compared to 2011-14. It is estimated that around 85 percent of milk in world is produced from cows. However, the contribution from other dairy animals, such as buffalo, goat, sheep and camel is 11%, 2%, 1.4% and 0.2% respectively. The dairy industry is fundamental to the wellbeing of billions of people throughout the world. Moreover, milk is used to prepare many valuable dairy products including cheese, butter, cream, yoghurt, butter oil, ice cream etc, which are widely consumed by people of developed as well as developing nations. Production of safe food including milk is a global health concern. Food safety is making a food safe to eat and free from disease producing agent, where as milk quality makes its products desirable to eat with regards to good taste. Milk can be contaminated by physical (hair, dirt, plastic, stone, dung, broken glass, wooden splinter), chemical (cleansing agents, insecticides, antibiotics, radio nuclides, fungicides) and biological agents (bacteria, viruses, protozoa). The contamination can occur at any stage of milk chain during production, processing, packaging, and distribution.

Cross contamination is the transfer of harmful organisms to food which can occur from hands to food, equipment to food and food (raw) to food (processed). Biological hazards are caused by a variety of microbes, which are ubiquitous in distribution and are isolated from air, water, soil, etc. Some microbes such as Alcaligenes, As per gillus, Bacillus, Cladosporium, Flavobacterium, Fusarium, Micrococcus, Mucor, Penicillium, Pseudomonas, Rhizopus, Serratia, etc. can result in spoilage of milk(Pal and Jadhav,2013) whereas pathogenic organisms cause many milk-borne diseases such as brucellois, campylobacteriasis, corynebactriosis, listeriosis,salmonellosis, streptococcosis, tuberculosis, yersiniosis and others (Pal,2012). These diseases occur in sporadic and epidemic form resulting in significant morbidity and mortality among the consumers. Milk borne pathogens produce life-threatening infections,particularly in infants, elderly, pregnant women and immune-compromised persons. Hence, clean milk production is highly significant from public health and economic point of view.

It is believed that history of domestication of cattle and ingestion of milk and milk products goes back to 6000 BC. Milk is defined as whole, fresh, clean, lacteal secretions obtained by the complete milking of healthy dairy animals, such as cow, buffalo, goat, sheep, and camel. It is a good source of many vitamins and minerals which are essential for the maintenance of good health. The composition of milk is influenced by several factors such as species, breed, genetics, age, nutrition, season, lactation stage, completeness of milking, diseases and environmental conditions. In many tropical countries including India, there is a lack of cold chain infrastructure that renders the raw milk of poor quality. There is much scope for the improvement in the quality of milk produced by making quality strategies for the post-production handling of milk. Clean milk means that it comes from the udder of healthy animals and has good flavor, pleasant smell, free from dust, dirt, drug residues and does not contain harmful microbe, which can affect human health. The milk can be contaminated with microbes during or after milking. High-quality milk should have longer keeping quality, proper nutritive value, normal taste, color, odor and be free from extraneous matter.

Clean milk protects the health of the consumer and also can be used to prepare high quality dairy products.

It fetches high price in the market and boosts the financial condition of the dairy farmer. According to the World Health Organization (WHO), the food safety can be defined as the assurance that food will not cause any harm to the consumer when it is eaten according to its intended use. Therefore, it is imperative that good hygienic practices should be meticulously be applied on every food including milk during production, processing, handling, distribution, storage, sale and use so that consumer gets clean, safe, and wholesome product which will not cause any food borne infection or intoxication.

The milk secreted from an uninfected animal’s udder is considered sterile, but later it becomes contaminated during milking, cooling and storage. It is an excellent medium for the growth of bacteria, yeasts and moulds that are the common contaminants of any food material including milk. Rapid growth of microbes, particularly at high ambient temperatures,-can spoil the milk. Contamination can be avoided toa greater extent by adopting the basic rules of clean milk production. Microbial contamination may be from external or internal sources. During the progress of milking, bacteria are present in the largest numbers at the beginning and then gradually decrease. This is primarily due to the mechanical dislodging of bacteria, particularly in teat canal, where the numbers are probably highest. Due to this, discarding of the first few streams of milk helps in lowering the counts of microbes in milk.

Most common bacteria causing mastitis in dairy animals are Staphylococcus aureus, Streptococcusagalactiae, Streptococcus dysgalactiae, Streptococcusuberis, Escherichia coli and Corynebacteriupyogenes. The infections of mammary gland, unclean udder and teats of animal also lead to increase in bacterial count of milk. It is frequently observed in several small dairies that udder and teat become soiled with dung, mud and bedding material such as sawdust, straw, rice husk, sand etc. As udder micro flora are not affected much by simple washing, therefore, economy washing with sodium hypochloriteac companied by drying help in reducing the number of microbes. The coat of dairy cow may carry bacteria from the stagnant water pools, especially the microbes causing ropiness in milk. Further, the risksof contamination from milkers are definitely higher, when cows are hand-milked in comparison to when they are machine-milked. Soiled clothes and hands of handler also increase the risk of contamination of milk and milking equipment many folds.

The milkers with infected wounds on hands contribute pathogenic Streptococcus spp., Staphylococcusspp. and micrococci. Improperly cleaned milk cans and lids if left moist will result in multiplication of thermophilic bacteria. Water used in productions hould be of good bacteriological quality. Inadequately cleaned storage tanks, untreated water supplies from natural sources like bore wells, tanks and rivers may also be contaminated with the faecal microbes,such as Coliforms, Streptococci and Clostridia.

Air contains dust, moisture and microbes, henceits entry should be minimized in milk parlour. Some of the practices that increase aerial counts in milk are sweeping of floors just before milking process, brushing of animals prior to milking process, having the dusty bedding materials for animals and allowing dust and dirt to accumulate on the walls or ceiling of sheds.

Clean milk production, which includes good animal husbandry practices, use of potable water, proper handling, storage and transportation of milk, is an importantelement to produce excellent quality of milk.

The lids of the milk cans should fit tightly to prevent entry of dust particles. The cans should be stored in an inverted condition on stand. It is pertinent to avoid unwarranted agitation during transportation of raw milk. When milk is agitated, the milk fat is destabilized and becomes easily oxidized. The milk tanker should have proper insulation. During transportation of milk to the dairies, the cold chain should be maintained for preventing deterioration. It is emphasized that milk must be cooled to a temperature below 50oCby using refrigerators or water coolers preferably within two hours after milking. The milk cans should be cooled by immersing them in clean, running water.

High storage temperatures result in rapid microbial growth and hence causes faster milk spoilage. The personal hygiene of the milker and milking process is fundamental to get clean milk that is safe, and wholesome to the consumer. It is recommended that educational programs should be organized for the farmers for making them aware of the importance of clean milk production. Milking should be done using the full hand. It is best to milk rear quarters first as they contain the higher proportion of milk. Pressing the teats using the thumb is not a good practice. It should be avoided otherwise the teats get damaged and mastitis may develop. The milking should be completed as quickly as possible in about 5-8 minutes.

Milking should be done completely and if milk is left in the udder, it will become a source of infection and causes mastitis to develop. The first milk should be examined by California Mastitis test for the

presence of mastitis every time prior to milking. If the dairy animal is suspected for mastitis, the particular quarter should not be milked and treated. It is important that milkers should be made aware of the correct handling of the milk from udder to reception dock, maintenance of hygienic environment, thorough cleaning of milk utensils and proper cooling of milk.

The animals, maintained in hygienic environment for production of quality milk, should be in perfect health. The animal should be fed with nutritious and complete feed, which consist of roughages and concentrate mixtures. The feed, fodder and silage should be procured from a reliable source and should bestored properly. Ample supply of clean water should be made available at dairy farms for various activities.

Hygienic measures, which include excellent cleaning of animal shed, proper ventilation, sufficient lighting for building and shed, satisfactory drainage system and adequate disinfection are necessary to maintain animal health. The cleaning of bedding material like sawdust, paddy, straw etc. should be done once daily. High quality of raw milk can be produced from healthy animals, which are kept under good hygienic conditions.

The milking utensils and containers should be made of stainless steel and must have smooth milk contact surfaces with minimal joints and crevices. The rubber components of the milking machines should be renewed at regular intervals. It should be cleaned before and after milking with hot water and certified detergents or chemicals. It is advised that only potable water should be used on dairy farms. Shaving the hair of the hind legs and tail of animal should be carried out routinely. The foremilk should be discarded in a proper place. It is necessary to drain all the milking equipment in a clean place before storage.

Microbes can adversely affect the safety and quality of milk and milk products. Cleaning is the process of removing the soil from the surfaces of equipment and utensils used in the dairy industry. A number of detergents or sanitizers such as chlorine, idophore, benzalconium chloride, sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium phosphate, sodium meta silicate, citric acid, phosphoric acid, tartaricacid, nitric acid etc. are used for cleaning dairy equipment. Chlorine is the most commonly used sanitizing agent in the food industry including dairy plant.

The milking equipment and cooler should be cleaned by rinsing in clean water, scrubbing in hot (≥45°C) detergent or disinfectant solution and finally rinsing in chlorinated (50 ppm) water. It is advised that no residue of chemical used in dairy equipment should be carried into the product after cleaning operation. The milkers are advised to wear clean protective clothes (apron, mask, and cape) and maintain high level of personal hygiene by washing of hands before milking and ensure that they should not eat, drink, sneeze, spit, insert finger in nose, or smoke near milkor milk container. If milk handler is suffering from communicable disease such as a sore throat, bacillarydysentery, tuberculosis, typhoid, diphtheria or having open wounds and pustules, they should not be allowed to work in the dairy plant. It is recommended that persons working in the dairy industry should undergo a periodical medical examination to rule out any infectious disease.

Milk is a raw material that is processed to manufacture many dairy products worldwide. Hence, good quality of milk should be made available to get excellent milk products (cream, cheese, ice cream, yoghurt etc.) with long shelf life and safety to consumers.

Strategies, such as cleanliness of milch animals, personal hygiene of milking person, sanitation of milking place and animal shed, cleanliness of milking vessel and utensils of milk collection should be meticulously followed for clean milk production.

The attainment of proper hygiene in dairy farm improves economic benefit of the producer and health safety perspectives in the consumer. It is, there fore ,very important to ensure high-quality raw milk produced from healthy animals under hygienic conditions.

It is recommended that training and guidance to dairy farmers on the need for hygienic practices at the farms should be given. Moreover, information on health hazards associated with ingestion of contaminated raw milk should be imparted to the public, so that consumption of un-hygienically produced raw milk could be avoided.

Milk has the potential to cause several food borne infections of multiple etiologies. Raw milk is also known to be associated with pathogenic bacteria, which cause milk-borne diseases such as tuberculosis, brucellosis or typhoid fever, etc. Hygienic milk production, proper handling and storage of milk and appropriate heat treatment can reduce or eliminate pathogens in milk. In many countries, milk processing factories are required a law to ensure pasteurized milk before selling it to the public. Many consumers also routinely boil milk before drinking it to protect themselves from milk-borne diseases. Processed milk must be handled hygienically to avoid post-processing contamination.

Hygienic milk handling includes using clean equipment, maintaining a sanitary milking environment, observing good personal hygiene, preserving the quality of milk during storage and transportation to the consumer or processing plant. As the health of dairy animals is of paramount importance for producing safe milk, it is highly imperative to appoint qualified and experienced veterinarian, the main custodian of animal health, for the de-worming, vaccination and treatment of animal diseases. Further attempts should be made to develop rapid, sensitive, easy, and low-cost kit, which can be routinely used in dairy farms to detect microbial spoilage of milk. It is emphasized that food safety measures such as good hygienic practice (GHP), good manufacturing practice (GMP),hazard analysis and critical control practice (HACCP),quality management, microbial risk assessment should be implemented in all food industries, including dairy sector.

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