Determination of some quality and safety parameters of black raisin juice

The aim of the present thesis study was to determine some quality and safety parameters of raisin juice, such as total soluble solids, pH, titratable acidity, kinds and quantity of sugars, phenolic acid compounds, polyphenol oxidase activity, water activity, total microbial counts and sensory evaluation. The total soluble solids and pH values were significantly decreased after two weeks of storage, while the titratable acidity in most samples were slightly changed. Glucose, fructose and sucrose as well as three kinds of phenolic acids such as gallic, chlorogenic and vanilic acids were determined in all samples. Total bacterial count of the freshly prepared raisin juice and of the raisin juice stored for one and two weeks not significantly changed. The water activity was slightly decreased, while the polyphenol oxidase activity was significantly decreased, after storage for two weeks. Consequently, it can be said that the freshly prepared raisin juice and the raisin juice stored for one week have higher quality and safety values than the raisin juice stored for two weeks.