Comparison of Contents of Sugars, Organic Acids and Free Amino Acids in Raisins Obtained From Gok Uzum (Vitis Vinifera L.)

Abstract

Raisins are known as an important source of many bioactive compounds such as organic acids, free amino acids, and sugars. In this study, oak ash and potassium carbonate solutions applied before drying were compared for their effects on the Gok Uzum raisin, more specifically, its contents of organic acids, free amino acids, and sugar profile. The total acidity quantified in the samples of raisin, ranged from 20.30 to 117.08 ng/mu L DW for the potassium dipping solution, while values ranged from 17.98 to 164.72 ng/mu L DW for the oak ash dipping solution. In samples from either dip solution, serine was predominant, followed by alanine, asparagine, glutamine, aspartate, sarcosine, glutamate, and leucine, whereas glycine, arginine, proline, histidine, and valine were found to be the lowest amino acids. In the samples examined, fructose was the most abundant sugar, whereas the lowest sugars in raisins were xylose for oak ash application and galactose for potassium carbonate application. There was wide variation in the sugar profiles for both variants, with values ranging from 3043.48 to 0.71 g/100 g DW. Drying Gok Uzum grapes after the treatment of oak ash dipping solution promotes a higher content of organic acids, amino acids and sugars as compared to drying after potassium carbonate solution treatments. These results could be used for the development of an attractive pre-drying solution in further studies for the production of both, raisins and perhaps other dried fruits.