Effects of Refrigeration, Freezing and Blast Freezing on Quality of Raw Cow’s Milk

Abstract

In the Philippines, milk production is often inconsistent due to seasonality leading to either shortage or surplus of milk. Before processing, dairy farmers and cooperatives subject their collected raw milk to low temperatures to delay the deterioration of milk quality. This process is performed to prevent profit loss, reduce food waste and generate a sustainable supply chain. The study determined the effects of refrigeration, freezing and blast freezing on preserving the quality of raw cow’s milk before processing. Chemical, foaming, microbial and sensory characteristics were determined to compare the effect of each treatment. Milk samples were refrigerated at 4 °C for 12 h (RM), frozen at -18 °C for 16 h (FM), and blast frozen at -40 °C for 10 h (BFM). Before conducting the analyses, FM and BFM were thawed at 4 °C for 22 and 16 h, respectively. Fat (4.07%) and protein (2.97%) significantly decreased in FM while moisture, total solids, titratable acidity and pH did not significantly differ among treatments. The foam value and foam volume were significantly higher in RM (88.00% and 86.33 mL) and BFM (91.58% and 89.75 mL), respectively. BFM had the lowest counts of aerobic microorganisms (5.16 log10 CFU/mL), coliforms (1.38 log10 CFU/mL), and Escherichia coli (< 1.00 log10 CFU/mL). Milk samples were pasteurized at 63 °C for 30 min before the conduct of the sensory analysis. Sensory characteristics did not significantly differ among treatments. From the results, blast freezing can be generally considered the most viable solution for storing raw cow’s milk before processing.