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It is clear from several food safety studies that there are three main types of hazards in food microbiological hazards, chemical hazards and physical hazards (De Boer et al. 2005; McCarthy et al. 2006; Spais and Vasileiou 2011; Yeung and Morris 2001). Milk hazards are also divided in the same categories and these may remain in milk through various processes which carried out for milk processing. Sources of initial milk hazards may come at primary stage of milk secretion/ milking process from milk giving animal, through interior of udder, udder and teat surfaces. Second source of hazard could be from process of milking, reception, storage etc., through milking equipment, milk transport line and storage tank. Other source of hazard could be milking environment, air and water and personal hygiene. In addition to these, chemical hazards might be come through cleaning and sanitising stages (Braunig and Hall 2005). Presence of any of these food hazards shows poor results of milk processing and hygienic practices.
2.1.1 Biological Hazards
Group of pathogenic microorganism might be predominant and responsible for food poisoning issues. Human body is much more sensitive with higher microbial cell count and result in connection of food disease (National Mastitis Council 2001). Higher numbers of microbial cell count have major impacts on human health risk, and it simultaneously associated with either poor food hygienic practices, residue of antibiotic, pathogenic microorganism or levels of toxic constituents in milk. And it studied that some toxins which have higher stability to heat treatments e.g. enterotoxins, produced by food pathogens and it results in food poisoning due to infected milk cattle (National Mastitis Council 2005). The major risk of higher somatic cell count of milk to human is because of consumption of raw milk or milk which is gone under partially pasteurization (Oliver 2005). In tropical milk farming environment, chances of contamination and growth of microorganism in milk are much higher and cannot be eliminated from milk until any suitable heat treatment.
Microbiological counts were found higher in majority of urban dairies compared to organized dairy. In urban areas from which milk has been collected, came from farmers having single to number of combine breed of animals. Higher numbers of microbial counts convey poor hygienic condition and much chances of spoilage causing microbes or pathogens which represent as biological hazards for consumers who involved in purchasing of raw milk directly from farmers. Higher number of bacterial counts results due to poor dairy setup process and systems (Iyer et al. 2010). Microbial counts can be minimized or reduced by preventing initial milk contamination and succeeding good hygienic condition at milk farm level (Anand et al. 2006).
Bacteria may be classified by the formation of clusters:
Diplococcic - two cocci shaped cells in paired.
Staphylococci - cocci shaped bacterial cell in clustered form.
Streptococci -cocci shaped bacterial cells arranged in chain formation.
Raw milk and pasteurized milk has been serving as major source as transfer medium for these bacteria to human than powder milk. Mostly common food poisoning causes were bacterial. It has been found that Salmonella, Campylobacter coli, Listeria monocytogenes and Escherichia coli are major cause of food poisoning which been identified by Food Safety Advisory Centre, London (FSAC 1993), because they grow faster in condition where milk been handled in tropical environment for long period of time without refrigeration and cooling. Chances of growth and survival of these pathogens are mostly temperature and time dependent for which milk and food product been handled as unprocessed during supply chain.
Bacterial growth can be explained by an increase in total number of cells rather than an increase in all cell size. Out of all different the main process by which bacterial cells divides in two cells to reproduce them is known as binary bacterial fission. The total time taken by bacteria from complete cell formation to its starting of cell division is known as bacterial generation time (Ray 2004). The following phases can be identified; lag phase, log phase, stationary phase, and death phase. Bacterial growth mostly depend on different growth factors which includes, temperature, nutrient in medium, amount of water present, level of oxygen, acidity of medium etc., and have tendency to remain in active in raw milk and milk which contaminated (Boor 1997; Johnson et al. 1990). Bacterial types commonly associated with milk (Hayes and Boor 2001) are;
Bacillus spp. (anthracis & cereus)
Campylobacter (coli & jejuni)
Clostridium (botulinum & perfringens)
E. coli (EPEC, ETEC, VTEC)
Enterococcus (faecalis & faecium)
Mycobacterium (bovis, tuberculosis & paratub)
Streptococcus spp. (pyogenes, agalactiae, etc)
Vibrio spp. (cholera, parahaem. & vulnificus)
Yersinia spp. (enterocolitica & pseudotuber.)
2.1.2 Chemical Hazards
Milk safety is not limited to only microbial hazards, but use of chemicals in milk farms and milk plants also leads to chemical hazards. Chemical were found in dairy milk samples as a result of poor milk handling practices and fraudulent practices done on the farm. Majority of milk found as adulterated with chemicals (BBC News Asia 10 January 2012) and found as substandard in areas where people does not aware with all such practices, throughout India. Chemicals have been added severely to deteriorate milk quality; this results in many of samples being found with chemical substances like added detergents, urea, skim milk powder, starch, sugars, vegetable fats, neutralizer etc, which has strong harmful effect to all living group in society and on children. Long-term consumption of milk with trace amount of urea and detergent might be serving as chronic disorder of the liver, kidney and intestinal track (Lab Saints 12 January 2012). These varieties of chemicals in milk may harm to consumers and especially to the children and infants babies for their brain developments, their growth and adverse effect on working of body organs (TOI 21 January 2012).These kinds of chemicals can be measured in tolerable daily intake (TDI) or acceptable daily intake (ADI), for doing comparison with level of these chemicals in food products (Leblanc et al., 2000).
Chemical hazards are not limited to added substances but also include water contaminated by heavy metals, drugs, antibiotic residue or hormones. It is not possible to inactivate this type of chemicals in milk by filtration or thermal processing in the same way as physical and biological hazards. Long term consumption of this chemicals hazards result in failures of some of body parts, kidney problems, inhibition of immune system, sickness of endocrine, neurological disorder or disease like cancer (Mansour 2011). Chemical content can be measured with new technologies like Temperature Program Micro Sensors (Meier et al. 2009), use of Nano-sensors (Sozer and Kokini, 2009) etc. which available to determine various chemical impurities in food and helps to take necessary action in its prevention in food and ultimately strengthening HACCP to make standard operating procedure.
ICMR reported that these chemicals cause a range of effects to human e.g. detergents in milk cause food poisoning and other gastrointestinal problems; high level of alkali destroy protein and damage body tissues; types of synthetic chemicals cause heart problem, cancer or even death and in long term consumption of even small quantity of adulterated milk or chemicals results in serious issues (CSE2012).
2.1.3 Physical hazards
In milk production system, chances of contamination of milk with various types of foreign material or other particle could be hazardous and result as physical hazard to milk consumers. Some foreign particles, such as broken pieces of glass or tiny metals, suppose positive risk of cutting the consumer's mouth, teeth or sometimes more damage to inner body parts if swallowed. Because of these reasons, manufacturers have to take care of risk reduction by these physical impurities and its chances of reduction in food. In addition to that glass has been used as packaging material of milk and proper care must be taken to avoid this type of damage and breakage of milk containers. In addition to other physical hazards, pieces of sharp metal, wood or stone can result in similar effect to human body (Adams and Motarjemi 1999).
These types of hard object have potential to damage teeth and human internal body organs; sometimes it result in choking mostly to the children when it swallowed. These types of impurities have greater chance for milk which is nor processed and passed through screening and micro filtration process. Severity of these particles noted greater in raw and unprocessed milk. Milk which processed and packed in organized or processed dairy pant passed through these types of screening and shorting devices such as metal detectors. X-ray machines have also been installed at processing line to detect physical foreign objects in milk pack. These types of measures are not able to use in loose milk production and selling channels or at village levels in which farmers follow milk selling in rural and in urban areas (Adams and Motarjemi 1999).
2.2 Factors influencing milk hazards
Production of safe and quality milk is a primary requirement for consumers. Milk safety must be controlled at each step from beginning of production to final consumption. Once it is found that any milk is unfit or unsafe for consumption, whether from chemical or physical contamination or microbiological testing, it should be removed from the market. Removal of chemical hazards and impurity is impossible or very difficult through processing and at the ambient temperature pathogens and spoilage organism can grow faster and affect the consumers, once it consumed. Among all the microbes, some of them are mesophilic and some of them are thermophilic (Walstra et al 2006).
Milk is an excellent growth medium for some of the microorganism especially the mesophilic bacteria that has multiple growth range base on surrounding temperature. Many types of bacteria able to survive in milk because of its good nutritional quality and it may result in higher number of bacterial counts and amount of toxins which produced by pathogenic organism, making it unsafe for consumptions.
2.2.1 Sanitary and hygiene factors
Contaminated raw milk is much more capable to transmit pathogens to consumers than processed milk. Bacteria which are responsible for this kind of illness can be destroyed by thermal processing by pasteurization, pre-pasteurization, heating of milk at such higher temperature or sterilization (Lore 2006). However, processing may increase food cost to consumers. In case where consumers preferred cheaper raw or unprocessed milk from local farmers, they have higher chance of bacteriological hazards because it sold without initial thermal processing that could reduce biological hazard at primary stage before the production of toxic substances.
Once milk is secreted from animal it must be kept in hygienic and safe condition until final consumption. It is necessary to prevent it from source of contamination and from biological hazards by applying suitable standards of hygiene and disinfection to the area where animals have been kept. The main factor to maintain quality and safety of milk is to avoid direct and indirect contamination. It also depends on how consumers handles milk before the consumption once it has been purchased - how is it taken home, how is it stored, heat treatment before and after storage and many more (Valeeva et al. 2005). It also necessary to follow process of safe and clean milk production in which care should be taken for milk containers which used for milk transportation from one to another place and make sure it followed by proper cleaning and sanitizing procedure. In rural areas, farmers who are involved in individual milk farming suffer from lack knowledge and availability of sanitizing and cleaning agents for milk collecting and transporting containers. Furthermore, they do not have knowledge of milk food safety and hazards. Most of milk has been collected in India from these rural farmers via milk collecting centres and co-operative societies.
It has been reported that poor animal housing and feeding operation of cattle may affect the good microbial quality of finished milk (Torkar and Teger 2008). Pre-rinsing and washing of equipment involve in milking process such as automated milking machine and other accessories with unclear water adds the major causes of microbial count along with food pathogen in unprocessed milk (Bramley and McKinnon 1990). These pathogenic bacteria in unprocessed milk became major problem for people who drink unprocessed milk and ultimately result in public health issues. If fresh milk has been kept at warm temperature without proper hygienic and refrigerated condition, then it results in higher microbial count and poorer quality. There are many factors which can affect hygienic quality of milk like,
Hygiene of the milk producing animals.
Personal hygiene in the dairy.
Hygiene of tools.
184.108.40.206 Hygiene in the dairy
To get clean and safe milk production in dairy farm, the condition of milking animal should be properly maintained but in rural areas, it found very hard to maintain for those farmers which has only 1-3 or few cows. Because o poor economic circumstances they are not in position to afford suitable sanitizing, cleaning chemical and machinery for safe milk production. They do follow cleaning and washing of animal body parts like udder, nipples, flank, belly, particle of the dry guano, ground etc., with water. In same case, dripping may be fall down inside the milk buckets during process of milking, which might transport considerable bacteria which responsible for spoilage of raw milk (Food and Agricultural Organization 1989).
220.127.116.11 Personal hygiene in the dairy
Physical health and hygienic condition of the milker or person involve in milking process, has a relationship with hygienic condition of fresh milk directly and indirectly. To avoid such thing people who work in milking operation must be fit to work and free from disease to avoid contamination of milk with harmful microbes (Food and Agricultural Organization 1989). Personnel must be aware of all hygiene rules and regulation and standard operating procedure for working on milk farm. People who worked in milking environment were considered as one of the sources of microorganism and they might be responsible for spreading bacteriological hazards (Lelieveld 2003).
Hygiene of the tools
It is necessary for tools being used for milk handling must be sanitized and clean properly to avoid biological, chemical and physical hazards. All different king of equipment which used in milking operation must be sanitized before re using. Mainly small scale farmers collect milk in small kettle and only use milk can as mode of transport with larger quantities. In case where automated milking process used on farm, before milking all automated machinery must be sanitized or properly disinfected (Food and Agricultural Organization 1989).