Volatile component change in whey protein concentrate during storage investigated by headspace solid-phase microextraction gas chromatography

Whey protein concentrate (WPC) is a nutritious ingredient and has gained popularity to be used in many traditional and novel food products. It typically has a shelf-life of 9 to 18 months when stored at room temperature. Fresh manufactured WPC could have a bland or slightly dairy, whey flavor. However, recognizable off-flavor can be developed during storage and this off-flavor becomes one of the major factors limiting its application in delicate formula. To understand the off-flavor development during the storage, WPC 80 and Instantized WPC 80 samples were stored at 35, 40 and 45 degrees C for a period of 15 weeks. Selected volatile compounds including dimethyl disulfide, pentanal, hexanal, heptanal, 2-heptanol, 2-octanone, octanol, 1-octen-3-ol, 1-nonanol and 2-nonanol were analyzed using headspace solid-phase microextraction gas chromatography. The results showed that the concentrations of most of these compounds considerably increased during storage, especially when stored at 45 degrees C. Instantized WPC showed higher lipid oxidation compounds than regular WPC while removal of oxygen reduced their formation.