Real-time determination of microbial activity of pasteurized fluid milk using a novel microrespirometer method.
The effectiveness of the rapid CO2 evolution rate (CER) method was evaluated by using a novel noninstrumental microrespirometer to determine the microbial activity of pasteurized milk and comparing it with traditional culturing methods in homogeneous milk samples. Three different kinds of milk (skim, 1% fat, and whole) stored at 2 temperatures (4 degrees and 7 degrees C) were measured daily for CER, aerobic plate count (APC), and psychrotrophic bacterial count. The mean initial rates of CO2 evolution for all 3 samples stored at the 2 temperatures ranged from 3.42 to 3.71 microL/h/mL and increased to 29 microL/h/mL and above on the final day of the experiment. Regression analysis showed a high correlation (R = 0.98-0.99) between the APC and CER results in combined milk samples. A cut-off value of CER (25 microL/h/mL) for milk spoilage at refrigeration temperatures was identified. The real-time CER method shows promise as a potential alternative to the traditional culture method.
Ren
Zhao
Z
Florida State University, Department of Nutrition, Food and Exercise Sciences, Tallahassee, FL 32306-1493, USA.
Hsiehi
Yun-Hwa P
YH
D000818:Animals; D001431:Bacteriological Techniques; D002245:Carbon Dioxide / Q000737:chemistry; D015169:Colony Count, Microbial; D005223:Fats; D005504:Food Analysis; D005506:Food Contamination; D005511:Food Handling; D005516:Food Microbiology; D005519:Food Preservation; D008892:Milk / Q000378:metabolism*; D015233:Models, Statistical; D008962:Models, Theoretical; D015203:Reproducibility of Results; D013696:Temperature; D013997:Time Factors
D005223:Fats; D002245:Carbon Dioxide