The objective of this study was to identify aroma volatiles in sweet whey powder. Volatiles were isolated by solvent extraction and solvent assisted flavor evaporation. Fractionation was followed to separate acidic volatiles from nonacidic volatiles. Gas chromatography/olfactometry and gas chromatography-mass spectrometry were used for the identification ofaroma compounds. Osme methodology was applied to assess the relative importance of each aroma compound. Major free fatty acids detected were acetic, propanoic, butanoic, hexanoic, heptanoic, octanoic, decanoic, dodecanoic and 9-decenoic acids. Major non-acidic compounds detected were hexanal, heptanal, nonanal, phenylacetaldehyde, l-octen-3-one, methional, 2,6-dimethylpyrazine, 2,5- dimethylpyrazine, 2,3-dimethylpyrazine, 2,3,5-trimethylpyrazine, fiirfuryl alcohol, p-cresol, 2-acetyl pyrrole, maltol, furaneol and several lactones. The aroma of whey powder comprises mainly of curd fermentation products and compounds formed during further chemical processes such as lipid oxidation and Maillard reaction. / Graduation date: 2005

Sweet whey powder is mainly used as an ingredient in foods and has a potential for increased use with the development of new foods. In view of the many whey powder producers, there is need to establish the quality of the whey powders currently on the market in terms of conformance to specifications, consistency over different seasons, and keeping quality. Selected sweet whey powder from different processors was analysed for microbiological, physicochemical and sensory quality. The whey powder was in most the cases within specifications. There was suggestive evidence of seasonal variability in the cooked flavor and sweet taste. In regard to storage, there was no significant difference in the flavor and aroma of the whey powder with storage except for the oxidized flavor which was marginally significantly different in at least one product. Most of the variation was in the microbiological and physicochemical properties. Of three products considered, rate of deterioration by the Maillard reaction, one was significantly different from the other two, having lower activation energy. Accelerated shelf-life testing deterioration rates compared well with those at ambient conditions for two products, implying that ASLT can be used for shelf-life determinations only if Maillard reaction inhibitors are absent. The flavor and aroma of sweet Cheddar cheese whey powder from one processor over 12 months, was consistent. However, the physicochemical, and microbiological properties were variable mainly between the fall and summer production with the fall production being higher in L* (lightness) and pH, but low in solubility index, and conversely, the summer production being high in solubility index and titratable acidity but low in L*. / Graduation date: 2005