Effects of isochoric freezing on quality characteristics of raw bovine milk

Authors: MAIDA, ALAN - University Of California Berkeley; Bilbao-Sainz, Cristina; Karman, Andrew; Takeoka, Gary; POWELL-PALM, MATTHEW - Texas A&M University; RUBINSKY, BORIS - University Of California Berkeley

Submitted to: Foods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2023
Publication Date: 11/16/2023
Citation: Maida, A., Bilbao-Sainz, C., Karman, A.P., Takeoka, G.R., Powell-Palm, M., Rubinsky, B. 2023. Effects of isochoric freezing on quality characteristics of raw bovine milk. Foods. 12(22). Article 4150. https://doi.org/10.3390/foods12224150.
DOI: https://doi.org/10.3390/foods12224150

Interpretive Summary: In light of a growing global population and the challenges posed by climate change and increasingly extreme weather patterns, ensuring food security has become a concern for the global community. Milk, renowned as one of nature’s most complete foods in terms of nutritional value plays a pivotal role in addressing these insecurities. However, dairy farmers annually discard milk due to fluctuations in production and milk disposal due to spoilage. Milk, with its rich nutritional content and physicochemical properties, is an ideal breeding ground for bacteria, making milk one of the riskiest foods in terms of food safety. The cumulative effect of these issues has led to a staggering global estimate of approximately 128 million tons of milk being discarded each year. In this study, we explored the potential of isochoric freezing to extend raw bovine milk preservation. We found out that isochoric freezing can offer a promising solution to enhance food security, reduce food waste, and provide consumers with nutritious milk for longer times.

Technical Abstract: This study investigated the effects of isochoric freezing (IF) on the shelf-life and quality of raw cow milk over a 5-week period. The results were compared with conventional refrigeration (RF) and refrigeration after pasteurization (HTST). The IF treatment process entailed storing liquid raw milk in isochoric chambers in thermodynamic equilibrium at -5°C /77MPa and -10°C /96MPa. Several parameters were analyzed, including microbiology count, physicochemical properties, indigenous enzyme activity, and nutritional values. Both pasteurized and raw milk experienced microbial level increases past the acceptable threshold (=5.5 log CFU/mL) after 2 weeks and 5 weeks, respectively, leading to the deterioration of other parameters during storage. In comparison, microbiology count decreased significantly during storage for both IF treatment conditions, but was more pronounced for the higher pressure (96MPa) treatment, leading to undetectable levels of microorganism after 5 weeks. IF treatment maintained stable pH, titratable acidity, viscosity, lipid oxidation, volatile profiles, total protein content, and lactoperoxidase activity throughout the storage period. Color was preserved during IF treatment at -5°C/77MPa; however, color was impacted during IF treatment at -10°C/96MPa. Protein structures were also modified during pressurized storage in both IF treatments. Overall, the study demonstrated that isochoric freezing could significantly increase the shelf-life of milk by reducing microbiology activity, whilst maintaining its nutritional content. These results underscored the potential role of isochoric freezing as a valuable tool in eliminating pathogens while maintaining quality characteristics similar to raw milk over long storage periods.