Survey of predictive model for microbial load in raw and pasteurized milk with measuring electrical resistance (Impedance-Splitting Method) and it's correlation with milk titrable acidity

Document Type : Research Paper



    Measuring total microbial count of milk with conventional standard pour plate method and comparing the results with standard limits is one of the routine tests in dairy factories. Achieving the results of total microbial count in minimum time is really important for confidence from the hygienic quality of products. Therefore, impedance splitting method as a new technique for this purpose was considered in order to receiving the results in less time and as soon as possible. The main purpose of this study, was to evaluate the correlation between impedance detection time (IDT in hrs), total microbial population (log10 N) and titrable acidity (0D) of raw and pasteurized milk. During 6 months, 100 samples (50 samples of raw and 50 samples of pasteurized milk) were collected from different areas of Ahvaz and examined under sterile conditions. The total microbial count by pour plate technique and impedance splitting method, also measuring milk titrable acidity were carried out based on the recommendations of Iran's Standard Institute and Industrial Investigation. Then, the calibration curves of 3 methods and their equations were obtained by using Excel software.  The calibration curves of methods were elaborated for total microbial count and impedance detection time, demonstrating a good correlation between the two methods (95.29% for raw and 95.09% for pasteurized milk samples). According to the calibration curves, the correlation between impedance detection time and  titrable acidity was 88.83% for raw and 85.4% for pasteurized milk samples, also the correlation between total microbial count and titrable acidity was 94.14% for raw and 93.27% for pasteurized milk samples. Therefore, impedance measurement which is a more rapid, automated and less laborious method than conventional total microbial count technique could be used like some developed countries as an alternative method for the rapid measuring the total microbial loads in foods instead of conventional methods.