A study of volatile “trapping” in spray dried whey protein concentrate by “crushing” and/or vacuuming, and detection by solid-phase microextraction/gas chromatography/mass spectrometry

Abstract

Flavour is an important quality aspect of spray dried whey protein concentrate (WPC). A blander flavour of WPC would find greater acceptance in a wide range of other combined foods. The objective of this study was to investigate the extent of physical “trapping” or “binding” of volatiles during powder formation in spray drying. Two simple procedures were used: (1) “crushing” and (2) subjecting WPC powder to vacuuming. Scanning electron microscopy images were used to observe the structure of the “original” WPC and treated WPC particles. Solid-phase microextraction followed by gas chromatography/mass spectrometry, and sensory evaluations of both powder and liquid samples of WPC, were used to demonstrate that although vacuuming and/or “crushing” WPC powder certainly liberate some aroma/odour-impact constituents, indicating a certain degree of volatile trapping by the physical structure, others may require the powder to be “crushed” more effectively, or dissolved in water, before a large percentage of volatiles are liberated. Thus, it appears that flavour volatiles are entrapped (thus supporting the selective diffusion theory) or bound in different ways to WPC, and that some of them are weakly bound, possibly hydrophobically.