Freezing Quality of High Moisture Dairy Products and Dairy Waste Utilization

Freezing food products is a common method used to extend shelf life but products with high-moisture content, such as sour cream and yogurt, or even low-moisture mozzarella are unable to be frozen due to a decrease in textural quality. The research objective of the first chapter of the thesis is to create a food grade antifreeze agent and evaluate its effect against freeze induced damage in sour cream and yogurt. Whey protein isolate and soy protein isolate were complexed with locust bean gum and lambda carrageenan and their hydrolysates. The complexes were tested for ice recrystallization inhibition (IRI) activity at pH 7.0 and 4.5 in 20 mM NaCl using splat assay. The freezing induced damage was evaluated through texture analysis and microscopic imaging. The complexes showed increased IRI activity at both pHs compared to the controls. However, once added to the sour cream and yogurt they were shown to be ineffective at protecting against freeze induced damage. The unhydrolyzed and hydrolyzed products resulted in decreased texture, cohesiveness, and consistency in both the sour cream and yogurt. This demonstrated that IRI active complexes in a model system does not always translate to similar effectiveness in the food matrix.

The second chapter of the thesis focuses on industrial cheese whey having the potential to be utilized as a source of health beneficial phospholipids, particularly sphingomyelin and phosphatidylserine. Phospholipids are located in the milk fat globule membrane (MFGM) and this component in whey can be precipitated out using thermocalcic aggregation. The objective was to optimize the extraction conditions of phospholipids from cheese whey by manipulating pH, calcium acetate concentration, and temperature. The optimum conditions of 50 mM, pH of 6.5, and a temperature of 60 ºC were chosen by evaluating total lipid yield, phospholipid yield, and protein and salt distributions. The results showed that an optimum phospholipid yield of 92% and distribution, 96% of proteins retained in the supernatant, and a salt recovery of 53% was achieved under these conditions. This project demonstrated a simple and cost-effective method to optimize the extraction of phospholipids from industrial cheese whey.