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Effect of heat treatment conditions and pH on physicochemical properties and protein denaturation of liquid milk protein concentrate.

N. Rafiee Tari

Events

06-22-2020

Abstract:

96
Effect of heat treatment conditions and pH on physicochemical properties and protein denaturation of liquid milk protein concentrate.
N. Rafiee Tari*1, A. Guri2, Z. Gaygadzhiev3, A. Wright1. 1Department of Human Health and Nutritional Sciences, University of Guelph Guelph, ON, Canada, 2Gay Lea Co-operative Foods Ltd Hamilton, ON, Canada, 3Reckitt Benckiser Evansville, IN.

Milk protein concentrates (MPC) are high-protein ingredients with unique functional and nutritional properties that can be tailored through modifying processing conditions, including temperature, pH, filtration conditions, and drying. MPC is typically dried to produce powdered ingredients. However, the effect of the processing conditions on structural and functional properties of liquid MPC remains to be thoroughly understood. In this study, the pH of liquid MPC (13% protein and 18.5% total solids) was adjusted to either 6.5, 6,7 or 6.9, followed by heat treatment at 85�C/5min or 125�C/15s. The extent of whey protein denaturation was analyzed by HPLC. Heat treatment at all studied pHs resulted in substantial denaturation of whey proteins, with β-lactoglobulin denatured more extensively than α-lactalbumin. More extensive whey protein denaturation was also observed for MPC heated at 125�C/15s compared with 85�C/5 min, irrespective of pH. Changes in liquid MPC structural properties were monitored over time; 1, 4 and 8 d after the process. Viscosity increased over time, regardless of temperature/time and pH, suggesting the role of whey proteins denaturation and aggregation, and their interaction with casein micelles. MPC at pH 6.9 had a significantly higher viscosity than MPC at pH 6.5 or 6.7, at both temperature/time conditions. Mean particle size of the MPC samples did not change significantly over time. However, the particle size distribution showed the formation of larger particles after 4 and 8 d of cold storage in samples heat treated at pH 6.9. This study showed that the degree of whey protein denaturation and inter- and intramolecular interactions of milk proteins are affected by pH and heat treatment conditions of liquid MPC. The findings provide a better understanding of the processing factors contributing to physicochemical properties of liquid MPC, which can be employed to develop milk protein ingredients with tailored structural and functional properties.

Keywords: liquid MPC, heat treatment conditions, pH.