Abstract
A total of 450 Gram-negative psychrotrophs were isolated from raw milk, cream and yoghurt samples in Egypt. They were identified and used to investigate the effect of temperature and time on their lipolytic and proteplytic activities on Spirit Blue Agar and Standard Caseinate Agar media, respectively. Under 6, 17 and 30 ℃ the lipolytic and proteplytic isolates have almost equal percentages in the total number of isolates. Under low temperature the isolates that can show their proteolytic activities are very few. It is suggested that the efficient control of low storage temperature could control the proteolytic activities. Lipolytic activities seemed to be produced earlier and considerably higher percentage of the isolates can begin their activities under low temperature after short time. Therefore, special attention should be given to lipolytic Gram-negative psychrotrophs.
