ارزیابی اثر سردخانه‌گذاری بر تغییرات کیفیت شیمیایی و میکروبی قالب‌های کره بسته‌بندی شده

Freezing causes changes on chemical and microbial quality of butter. In this research, effects of two different temperatures -9 and -18^oC on changes of moisture, fat, acidity and peroxide value and also Coliform and Psychrotrophic microorganisms in frozen butter were studied. Results showed that values of moisture and fat during 7 months of frozen storage at two temperatures decreased 1.8% and increased 1.78%, respectively. Acidity and peroxide value during 7 months of storage at two temperatures had no significant difference changes (P<0.05). Coliform microorganisms were destroyed after 2 months of freezing and the numbers of cells became zero. The numbers of Physchrotrophic microorganisms did not out of the range of standard in all and at -18^oC in compare to -9 ^oC was decreased more. Effects of storage temperatures and different weights on the chemical and microbial quality of butter were not significant (P<0.05).