Industrial yoghurt is maufactured from fresh cow milk in dairy industries but traditional yoghurt is made from goat and sheep milk. Level of microbial contamination by coliform in traditionally processed products is higher than that in industrially processed products. E.coli may not be present in industrially processed samples but contamination by E.coli in all stages of industrial production may be found in traditionally prepared yoghurts.
Post-procesing contamination could happen in both types of maufacturing processes in spite of chemical specification and low pH of yoghurt. Yeast is most imporatnt contaminant of starter cultures. Processing stage of yoghurt in incubation room could be the major point of contamination. As a result, it can be concluded that the higher level of contamination intraditional processing of yoghurt shows insufficient and low hygienic conditions of this technique in manufacturing palnts.
Some of the yoghurts on sale shelves may not have acceptable microbial quality in developing countries. Hence, it is essential to apply strict hygienic actions during production and delivery of yoghurts to avoid contamination with unwanted resources & microorganisms. The first step in this regard is to encourage consumers to consume industry-produced yoghurts instead of traditional ones. Systematically, inspection should be undertaken by manufacturers in yoghurt industry to control the lowly hygiene conditions and to apply sanctions where necessary. It is manufacturer's responsibility to teach their staff about sanitary and hygienic practices considering the high level of coliform contamination and factors controlling the shelf-life of yoghurt. Shelf-life of raw milk depends on quality of raw milk and on subsequent transportation and storage conditions. Shelf-life may be improved by deep cooling of milk immediately after milking and by applying thermalization when milk arrives into the factory. Post-contamination by gram-negative psychotrophic bacteria is major cause of limited shelf-life of pasteurized yoghurt.
In yoghurt, yeast and mould contamination is the primary cause of decay which must be avoided. Thus, it is recommended to pay attention to implementing actions and to apply new techniques to overcome cross- condition in ready-to-eat yoghurt by improving the fermentation technology as well as having good probiotic bacteria in the yoghurt.
Escherichis coli has been isolated from raw milk and unpackaged bulk milk samples. It is transmitted to humans by un-pasteurized milk. Fermentation temperature and subsequent packing temperature are serious factors for development and survival of E-coli in traditionally fermented yoghurt. Escherichia coli is able to live and grow during fermentation of traditional yoghurt with low lactose, reducing yoghurt Lactobacillus acidophillus counts but E.coli growth can be supressed by indutrial yoghurt manufacturing conditions. Yeasts and moulds may be present in traditional yoghurts due to poor sanitary conditions of milking and storage, improper heat treatment and secondary contamination. Milk is a good media for transmission of a broad range of pathogens. High yeast and mould counts in some samples revealed unsatisfactory sanitary during fermentation and post-production stages. Individuals or authorities must pay more attention in supervision on improving production quality of such yoghurts.
When dairy products are manufactured from AFM1-contaminated milk, the toxin could be detected in samples. Unfortunately, presence of AFM1 remains stable during processing & storage of several dairy products like yoghurt. This toxin cannot be inactivated via current processing used in dairy industry, for instance, pasteurization and sanitization treatments. It is necessary to determine the critical control points with automated control systems in order to eliminate and minimize threat of contamination. Probiotic yoghurt can decrease AFM1
content of initial milk during stoarge and production. High amounts of rpobiotic count in culture results in lowering AFM1 level in the final product. So, it is recomemnded for dairy industry and food safety agencies to have screening programs programs for initial milk, in prodcution of yoghurt.
Milk products are major components of human diet. Thus, AFM1 in milk and dairy products should be controlled systematically. Also, for producing good quality milk, it is vital to keep feeds free from contamination of AFM1. Moreover, it is important to notify producers and consumers about possible toxicity of aflatoxins, in order to reduce their potential health hazard in addition to economic losses. Organization of training programmes should also be considered by the government.