Characterization of Pasteurized Milk Spoilage by Electronic Nose in Relation to its Selected Quality Parameters

Abstract

Pasteurized fresh milk requires an accurate estimation of shelf life under various conditions to minimize the risk of spoilage and product losses. Milk samples were stored for 56 h in an oven at 25 o C and for 15 days in a refrigerator at 4 o C. Samples were analyzed using an electronic nose (e-nose), total bacterial count, titratable acidity and pH to determine the quality of milk. Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were used to analyze e-nose data of milk stored at 25 o C, and 4 o C. A clear shift in quality was identified by the e-nose, which also appeared in the total bacterial count after 24 h and 12 days for storage at 25 and 4 o C, respectively. On the other hand, titratable acidity exceeded the normal limits of 0.14 % - 0.21 % after 24 h for storage at 25 o C (0.247 ± 0.006 %) and after 15 days for storage at 4 o C (0.25 ± 0.01 %). If pH was a good indicator of quality for samples stored at 25 o C, it showed no clear trends for samples stored at 4 o C. Based on the microbial count data and e-nose output, the milk had a shelf life of 0.3 day (i.e. 8 h) when stored at 25 o C. Shelf life was extended to 9 days when stored at 4 o C.