Flavor deterioration in yogurt.

Volatile components of flavored yogurt preserved at 5 degrees C in the dark for 0 day, 3 days and 10 days were recovered by simultaneous distillation extraction (SDE) and headspace (HS) procedures. Gas chromatography (GC) and GC-mass spectrometry (GC-MS) analyses of those samples showed remarkable changes in some compounds. Aldehydes which contribute to expressing citrusy notes were reduced to alcohols during fermentation process and storage. As a result, the strength of flavors which expressed well-balanced citrusy notes in yogurt were weakened, and fatty or oily notes mainly caused from alcohols were strengthened reversely. Hydrocarbons were also digested by bacteria during a fermentation process. A small amount of other compounds, such as esters and terpene alcohols changed. Fewer effects of sorption into a package material and chemical reactions, such as hydrolysis esters, hydration or oxidation of hydrocarbons, were observed.