Dairy supply chain typically involves a huge number of actors from spatially dispersed places, where raw food materials will flow from farm-household producers in rural areas into large-modern food processors, retailers, and markets in urban area. Risks exist in every stage of production carried out by each of the actors along the production chain. This implies that the success of improving the performance of the dairy industry will mostly rely on the actors ability to manage risks. These actors include farm input suppliers, milk producers, milk processors, retailers and consumers. Most of the outbreaks are known to occurs as risks associated with processing sections are given primary importance over the one associated with non- manufacturing section of the production chain. Milk and its associated products are particularly rich in nutrients which provides an ideal environment for growth of many microorganisms. Due to perishable nature of milk and its associated products, equal attention is required at all stages of milk production cycle.
Components of Non- Manufacturing Segment of Dairy Industry
- Farm input suppliers: They are the first part of the dairy supply management cycle which provides feed for livestock (cow, sheep, buffalo, yak, goat, camel etc.)
- Milk Producers: Milk Producers are responsible for managing the herd and producing milk.
- Milk Processers: These include dairies and co-operatives, where raw milk is collected and converted into a wide range of shelf stable products.
- Retailers: Retailers distributes the final stable products to the customers.
- Customers: The final part of the chain is the consumption of the dairy product and are the end users.
Risks in Non-Manufacturing Section
Animal feed plays an essential role on the health of food-producing animals and the safety of products derived from them, namely milk and dairy products.
Biological Hazards: Animal feed can be a source of infections in food animals, with various pathogens, e.g., viruses, bacteria, and parasites, which subsequently may lead to the contamination of milk. For instance, improperly fermented silage (pH>4.5) can transmit Listeria monocytogenes to ruminants. Infected or healthy asymptomatic carriers can excrete high numbers of monocytogenes in their feces and contaminate the environment and ultimately the milk.
Naturally Occurring Toxins: Aflatoxin B is a known human carcinogen present in maize, peanuts and other crops and their fodders. It is metabolized and transferred to milk in the form of aflatoxin M1. Proper drying and storage of the feed are important measures for preventing growth of the toxigenic molds such as Aspergillus flavus, which is mainly responsible for aflatoxin formation. Other mycotoxins such as ochratoxin, T-2 toxins, deoxynivalenol and zearalenone may also be carried over into milk. However, they are more of concern for animal health rather than milk safety.
Industrial Origin Toxins: Animal feed is also a potential source of exposure of farm animals to environmental contaminants such radionuclides, polychlorinated biphenyls (PCBs) and dioxins.
- Animal Health:
Biological Hazard: Milk can harbor a wide range of microorganisms; therefore, raw milk can be a direct source of many types of foodborne infections. The contamination of milk may follow many different pathways. Some organisms are directly shed into the milk, particularly if the dairy herd suffers from mastitis or other infections, such as bovine tuberculosis, brucellosis and Q fever. Several bacteria can cause mastitis, including Staphylococcus aureus, Streptococcus spp. and Corynebacterium bovis. Other bacteria may contaminate the milk during the milking process through contact of the milk with the hide, udder or milking equipment. Animal feces and the environment are important sources of microorganisms, particularly when hygiene is poor. Farm workers can also be a source of contamination if personal hygiene is not respected. Therefore, contamination of milk goes beyond pathogens which are typically transmitted from the animal reservoir and can include any fecally transmitted pathogen of human origin, including viruses, parasites (e.g. Cryptosporidium) and bacteria such as Shigella and Salmonella typhi.
Veterinary Drugs and Hormones: The most used veterinary drugs associated with milk are antibiotics, employed to combat mastitis-causing pathogens in the dairy cow. National surveys in developed countries show that between 0.1 and 0.5% of tanker milk samples test positive for antibiotic residues. The occurrence of antibiotic residues in milk may have economic, technological, and even human health implications.
Several hormones are often used in relation to dairy animals, such as oxytocin and prostaglandins. However, one of the more controversial is bovine somatotropin (BST) (sometimes referred to as bovine growth hormone) and its genetically engineered counterpart recombinant BST (rBST).
Naturally Occurring Toxins: When dairy cattle and animals are exposed to mycotoxins through feed ingredients such as maize and peanuts. Mycotoxins pose risks to both animal and human health and, depending on the mycotoxin, may have carcinogenic, estrogenic, neurotoxic, dermonecrotic or immunosuppressive effects. Fungal species of greatest concern in the dairy industry are Aspergillus flavus, parasiticus and A. nomius. These species produce aflatoxin B1 and related toxins under favorable conditions of temperature, water activity and nutrient availability, which are common in subtropical climates. In recent years concern has been expressed about the presence of aflatoxin M1 in milk and milk products, which is an animal metabolite of aflatoxin B1. The exposure of humans to aflatoxins has resulted in liver damage and cancer. Codex has adopted a maximum limit (ML) of 0.5µg/kg of liquid milk but has not set an ML for its precursor aflatoxin B1 in animal feed. The EU has established MLs for feed commodities that vary between 0.05 and 0.005mg/kg. Provided that these MLs for aflatoxin B1 (and other mycotoxins) in feeds are observed, there should be no health problem from residues in milk.
Pesticides: It include insecticides, herbicides and fungicides. The most common concern is insecticides including organochlorines, the organophosphates and carbamates. Organochlorine pesticides enter the food chain as a result of their lipophilic properties, in this way biomagnifying in the food chain and bioaccumulating in individuals. Milk is considered as one of the more convenient indicators for measuring the extent of these persistent residues that originate in contaminated animal feed. The main route of human exposure to many organochlorine pesticides is through foods of animal origin. Typical contaminants of milk are the persistent fat-soluble organochlorine pesticides such as DDT (dichlorodiphenyltrichloroethane) and other organochlorine pesticides.
Adulterants: The addition of water to milk is probably one of the oldest forms of economic adulteration of food. However, other materials, such as chalk, were often added to mask this fraud. The most recent variation of this practice was the addition of melamine to milk. This was done to avoid detection by the standard analysis of crude protein in milk, sometimes called total protein, which is used to monitor and control milk quality in the dairy industry.
Physical hazards: These are generally foreign bodies, include glass, metal, stones, wood, plastic, dust, dirt, hair, and insect fragments. Although some technologies are available for the verification of any incidental contamination, effective removal of physical hazards at later stages of the processing and manufacturing is difficult.
Collection and transportation of milk is a point in the food chain where recontamination of milk with chemical or microbial hazards and/or growth of microorganisms can occur. Therefore, the bulk tanks and vessels used for milk transportation need to be cleaned and disinfected. Care should be taken that these are not used for any other purpose, especially the transport of potentially toxic materials. To minimize growth of microorganisms, milk should be chilled to a temperature of 6°C or below and processed as soon as possible. Transportation is also a point of vulnerability in the food chain where actions of sabotage or tampering may occur. Addition of Cl. botulinum toxin or other chemical hazards in milk have been considered as potential risks for bioterrorism or sabotage.
A potential source of contamination of dairy products in warehouses is pests such as birds, rodents, cockroaches, flies, and other insects. Pests are the reservoir for many pathogens; hence, through their droppings and urine, they are direct and dangerous sources of contamination of food. Contamination of products can also occur indirectly through the environment. Pest management is thus important both from a general hygiene perspective as well as for control of specific pathogens. Good warehouse management is also important to prevent any accidental contamination of the products or raw material with industrial chemicals.
5. Control Measures:
- Adherence to good agricultural practices (GAP) is encouraged in the management of natural, improved and cultivated pastures, and in the production of forage and cereal grain crops used as feed or feed ingredients for food-producing animals. Proper drying and storage of the feed are important measures for preventing growth of the toxigenic molds.
- Good farm management should in the first place be directed toward the prevention of infectious diseases, such as clinical and subclinical mastitis, to limit the use of veterinary drugs
- In the process, the farmer must keep his animals in sound physical condition by ensuring proper hygiene and good housekeeping practices and implementing sound farm management.
- Good transportation practices, maintaining the cold chain, need to be observed, for sensitive products.
- Efficient Pest Management activities must be executed inside the warehouse for preventing harborage of insects and rodents inside warehouse.
Most sources of risks for the entire chain arise from the upstream segment, mostly smallholder farmers. Under the presence of these risks, these actors tend to pose risk-minimizing behavior in producing their products. This situation, in turn, is manifested itself in the sub-optimal level of upstream production which is reflected in the condition of the quantity and quality of raw milk produced.