The Effect of Native Phospholipids on the Flavor and Flavor Stability of Bleached Cheddar Whey
Off-flavors due to processing of whey protein ingredients negatively influence consumer acceptance of ingredient applications. Previous research has demonstrated that bleaching of Cheddar whey increases lipid oxidation and off-flavors in liquid whey and resulting whey protein ingredients. Due to the high content of unsaturated fatty acids, native phospholipids have a high potential for lipid oxidation. The phospholipid to neutral lipid content ratio in fat free milk is reported to be significantly higher than in whole milk. The objective of this study was to determine the impact that native phospholipids in Cheddar whey have on the flavor and flavor stability of liquid whey. Liquid Cheddar whey was produced from whole milk, reduced fat milk, and fat free milk. The wheys were then fat separated to the same total fat content, pasteurized, bleached (250 ppm hydrogen peroxide) and stored at 4°C for up to 48 h. The wheys were sampled at 0 h, 24 h, and 48 h. The entire experiment was replicated 3 times. Flavor was analyzed by sensory and instrumental analyses. Phospholipids were quantified by UHPLC with an evaporative light scattering detector using hydrophilic interaction chromatography. Fatty acid profiles of the neutral and polar lipids were analyzed by FAME using GC-FID. All wheys increased in the lipid oxidation compounds pentanal, hexanal, heptanal, and nonanal and cardboard flavor from 0 h to 48 h (p<0.05). Liquid whey produced from fat free milk had higher concentrations of hexanal, pentanal, heptanal, and DMTS as well as increased cardboard flavor intensity after 24 or 48 h compared to other wheys (p<0.05). Phospholipids were significantly higher in the whey made from fat free milk compared to wheys made from whole or reduced fat milk (p<0.05). The polar lipid fraction contained higher concentrations of the unsaturated fatty acids 18:1, 18:2, 18:3, and 20:4 and lower concentrations of saturated fatty acids compared to the neutral lipid fraction. These results identify native phospholipids as a major source of off-flavors in liquid whey due to their unsaturated fatty acid profile and susceptibility to lipid oxidation.
Keywords: whey, phospholipids, flavor