Short communication: Flavor and flavor stability of cheese, rennet, and acid wheys.

Dried whey ingredients are valuable food ingredients but potential whey sources are underutilized. Previous work has established flavor and flavor stability differences in Cheddar and Mozzarella wheys, but little work has compared these whey sources to acid or rennet wheys. The objective of this study was to characterize and compare flavor and flavor stability among cheese, rennet, and acid wheys. Full-fat and fat-free Cheddar, rennet and acid casein, cottage cheese, and Greek yogurt fluid wheys were manufactured in triplicate. Wheys were fat separated and pasteurized followed by compositional analyses and storage at 4°C for 48 h. Volatile compound analysis and descriptive sensory analysis were evaluated on all liquid wheys initially and after 24 and 48 h. Greek yogurt whey contained almost no true protein nitrogen (0.02% wt/vol) whereas other wheys contained 0.58%±0.4% (wt/vol) true protein nitrogen. Solids and fat content were not different between wheys, with the exception of Greek yogurt whey, which was also lower in solids content than the other wheys (5.6 vs. 6.5% wt/vol, respectively). Fresh wheys displayed sweet aromatic and cooked milk flavors. Cheddar wheys were distinguished by diacetyl/buttery flavors, and acid wheys (acid casein, cottage cheese, and Greek yogurt) by sour aromatic flavor. Acid casein whey had a distinct soapy flavor, and acid and Greek yogurt wheys had distinct potato flavor. Both cultured acid wheys contained acetaldehyde flavor. Cardboard flavor increased and sweet aromatic and buttery flavors decreased with storage in all wheys. Volatile compound profiles were also distinct among wheys and changed with storage, consistent with sensory results. Lipid oxidation aldehydes increased in all wheys with storage time. Fat-free Cheddar was more stable than full-fat Cheddar over 48h of storage. Uncultured rennet casein whey was the most stable whey, as exhibited by the lowest increase in lipid oxidation products over time. These results provide baseline information for the viability of processing underutilized wheys into value-added ingredients.