Modeling keeping quality of pasteurized milk

The quality attributes of pasteurized milk such as total viable count (TVC), pH, conductivity and titratable acidity (TA) were determined during storage at 6, 15 and 25°C. The quality deterioration was indicated by an increase in initial TVC, conductivity and TA, and decrease in pH. The TVC increased from initial 10^3.6 CFU/ml to about 10⁶-10⁷ CFU/ml indicating spoilage of milk. The milk could be kept without spoilage for about 4, 1 and 0.35 day during storage at 6, 15 and 25°C, respectively. Changes in pH and TA could only be detected after TVC reached a level of about 10⁶ CFU/ml.). Results showed that both multiple regression and Gompertz models could be used for shelf-life prediction of pasteurized milk. However, the Gompertz model resulted in superior fitting to experimental data (r² = 0.98) compared to the multiple regression model (r² = 0.76).