Objective: Evaluation of efficacy of alcohol test to differentiate between acceptable and unacceptable bulk milk.
Procedure: One hundred fourty bulk milk samples from milk
colixtion centers around Shiraz were examined for titrable acidity, aerobic plate count (APC), California Mastitis Test (CMT) and
alcohol test with single and double volumes of 68° ethanol.
Statistical analysis: Correlation coefficients between alcohol stability and acidity, microbial quality and mastitic milk were
measured and sensitivity and specifity of alcohol test for evaluation of acidity, microbial quality and mastitic milk were calculated.
Results: No significant correlation was observed between alcohol
test (single and double volumes), CMT and the APC. Correlation
coefficient between single volume alcohol test and acidity was 0.18 (p<0.05). No significant correlation was detected between double volume alcohol test and acidity. The sensitivity of single and double
volume alcohol tests for differentiation between high acid milk (more than 16° Dornic) and normal milk (less than 16° Dornic)
wero 45.7% and 55.5%, respectively: and their specificity were
62.7% and 49.2%. Regarding microbial quality, sensitivity of single and double volume alcohol tests for differentiation between acceptable (APC<106 CFU/ml) and unacceptable milk (APC>l06 CFU/ml) were 4l.3% and 53.3%, and their specifity were 62.5% and 48.5 /. The sensitivity of single and double volume alcohol
tests for differentiation between normal milk (CMT negative) and mastitic milk (CMT positive) were 52.6%. and 63.2%, and their specificity were 59.5% and 47.0%, respectively. Conclusion: It is concluded from the results that alcohol test is not a confidential test to evaluate the quality of bulk cow’s milk. It is suggested that this test to be removed from routine evaluation tests
in or ilk collection centers and industrial dairy plants. J. Fee. Vet. Med. Univ. Tehran. 58, 2: 169-175, 2003.