Physicochemical Properties and Volatile Flavor Compounds of Unripe Peach Sugaring Solutions with Pectinase

This study investigated the effects of pectinase treatment on the physicochemical properties, antioxidant capacities, and volatile flavor compounds of unripe peach sugaring solutions. Three different unripe peaches including white peach, nectarine, and yellow peach were mixed with fructooligosaccharide, and treated with or without pectinase, and stored for 5 weeks. The pectinase treatment in unripe peach sugaring solutions increased the content of soluble solids and titratable acidity while it decreased pH when compared to the non-treated sample. The content of free sugars such as fructose and glucose increased with the pectinase treatment, but maltose was not detected in all varieties. Organic acid content, citric acid, malic acid, and succinic acid were diminished, whereas tartaric acid, lactic acid, and acetic acid increased after pectinase treatment. Among the unripe peach varieties, white peach showed the highest radical scavenging activity, regardless of the pectinase treatment, in both 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azinobis- 3-ethylbenzothiazoline-6-sulfonic acid assays. On the other hand, pectinase treatment caused an increase in antioxidant activity in all peach varieties. The content of phenolic compounds and flavonoids increased in all varieties following pectinase treatment. The total content of phenolic compounds was the highest in white peach, and the total flavonoid content was the highest in nectarine. In gas chromatography/mass spectrometry (GC/MS) analysis, 15 volatile flavor compounds were identified including 9 aldehydes, 2 esters, 1 acid, 1 alcohol, and 2 other types. In all varieties, volatile flavor compounds increased with pectinase treatment. Taken together, it can be concluded that pectinase treatment improved overall quality characteristics of unripe peach sugaring solution.