Effect of curd-cooking temperatures on the microbiological quality ofayib, a traditional Ethiopian cottage cheese.

Ayib was made following traditional methods of curd cooking at 40°, 50°, 60° and 70°C requiring 10 h, 7 h, 145 min and 55 min, respectively. During the natural fermentation of raw milk into sour milk (curd), the count of all groups of microorganisms increased by at least a 100-fold. When the curd was subsequently cooked at 40°C, counts of enterococci and members of Enterobacteriaceae decreased by a 100-fold and lactic acid bacteria and staphylococci by a 100-fold. At 50°C, the count of enterococci, members of Enterobacterlaceae and staphylococci was lower than could be detected (<10(2) c.f.u./g). Yeasts, moulds and lactic acid bacteria still had counts of about 10(5) c.f.u./g. The total aerobic count decreased by a 100-fold but was still high (>10(7) c.f.u./g). At 60°C, yeasts and moulds decreased by 1000-fold and at 70°C they decreased below detectable levels (<10(2) c.f.u./g). This latter temperature is thus recommended as it results in a less contaminated and saferayib.