Dairy starter cultures, inhibition

Apart from public health impacts, residual antimicrobials in animal products can bring about technoeconomic losses in the food processing industry. It has long been known that the presence of some antimicrobial compounds in milk can dramatically affect the production of fermented dairy products such as yogurt, cheese, buttermilk and sour cream (72, 73). As shown in Table 10.2, even minute concentrations of antibiotics in milk can cause inhibition of the growth of commonly used dairy starter cultures (74). 

The major problem has been the partial or complete inhibition of acid production by dairy starter cultures used in the manufacture of cheese, buttermilk, sour cream or yogurt... 

Greene, V. A. and Jezeski, J. J. 1957B. Studies on starter metabolism. III. Studies on cysteine-induced stimulation and inhibition of starter cultures in milk. J. Dairy Sci. 40, 1062-1070. 

Inhibition of Starter Cultures. The primary cause of antibiotic residues in milk and milk products is the failure of producers to withhold milk from the market for a sufficient time period following veterinary therapy for mastitis or other diseases in dairy cattle. Consumption of antibiotic-supplemented feed may also lead to residues in the milk. These antibiotics are quite stable and remain in the milk even after manufacturing pro-cessses including pasteurization, drying or freezing. Marth and Ellickson (22), Marth (23) and Mol (17) have reviewed extensively problems in the dairy industry associated with antibiotic residues in the fluid milk supply. 

Shortly after their development in the 1940s, antibiotics were used in veterinary medicine, first to prevent or treat mastitis in cows and later for the treatment of other diseases. Initial concern about antibiotic residues in milk was not a public health issue but came from dairy processors who noticed inhibition of starter cultures used in the production of cheese and yogurt, thus generating a need for screening tests to examine milk for antibiotic residues. " Since inhibition of starter cultures by penicillin in milk was the main problem, the earliest microbial inhibition assays were based on growth inhibition of lactic acid bacteria. Spores of Bacillus species were also utilized spores are easier to handle and far more stable than the vegetative cells. 

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