Total viable, psychrotrophic and thermoduric population of market samples of pasteurized milk


  • Vishnu Suresh
  • Ligimol James Kerala Veterinary and Animal Sciences University
  • Beena A.K. Department of Dairy Microbiology, College of Dairy Science and Technology, Mannuthy, Kerala Veterinary and Animal Sciences University
  • Aparna Sudhakaran V. Department of Dairy Microbiology, College of Dairy Science and Technology, Mannuthy, Kerala Veterinary and Animal Sciences University
  • Divya M.P. Department of Dairy Chemistry, College of Dairy Science and Technology, Mannuthy, Kerala Veterinary and Animal Sciences University


Pasteurized milk, Thermoduric count, Psychrotrophic count


Pasteurization, the process of heating every particle of milk to at least 63oC for 30 min or 72oC for 15 sec or to any temperature-time combination which is equally efficient is one of the major thermal preservation processes adopted by the dairy industry. The microbial groups of high relevance in terms of quality and safety aspects of pasteurized milk are the pasteurization surviving thermodurics and the low temperature growing psychrotrophic bacteria. So a study was conducted to determine the standard plate, psychrotrophic and thermoduric bacterial counts of market samples of pasteurized milk available in the local market and to derive correlations in between them. A total of forty market samples of pasteurized milk belonging to five different brands were assessed for their standard plate (SPC), psychrotrophic (PC) and thermoduric (TC) counts. The mean (±standard error) SPC, TC and PC of the pasteurized milk samples were 4.64±1.04, 2.9±0.64 and 2.63±1.3 log CFU/ml respectively. All the samples contained thermoduric organisms whereas psychrotrophic organisms were present in 87.5 % of them only. Standard plate count was found to be significantly (p≤0.05) positively correlated with TC and PC. Statistically significant (p ≤0.05) positive correlation was observed between PC and TC also. Among the different correlation coefficients obtained the highest was observed between SPC and PC (r=0.824). Significant differences (p≤0.01) were observed in between the mean values of SPC, TC and PC of the different brands of pasteurized milk samples tested.


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