Abstract
This study investigates the effects of four enzymatic treatments on the yield, physicochemical properties, and bioactive compounds of grape juices from two red (Golubok, Regent) and two white (Muscaris, Aurora) hybrid grape varieties. A total of 20 samples were prepared using four commercial enzyme formulations (Pectinex Ultra, Safizym Clear Plus, Safizym Press, and Rapidase color) applied at a concentration of 0.02% (w/w). The juices were evaluated for yield, total phenolic content, antioxidant capacities (ABTS, DPPH, FRAP), titratable acidity, turbidity, total soluble solids, and phenolic profile. The addition of enzymes significantly improved juice yield by 10% to 20%, with the effect varying depending on the type of enzyme and the variety of grapes. Pectinex Ultra was the most effective enzyme in reducing turbidity, while enzyme treatments had minimal impact on Brix levels and sugar concentration, which were primarily determined by the characteristics of each grape variety. The enzyme addition showed a minor influence on the titratable acidity of the juices, with slight increases observed in Muscaris, but the grape variety played a major role in determining the titratable acidity levels. Color parameters revealed that white grape juices (Muscaris and Aurora) were brighter than red varieties (Golubok and Regent). Additionally, enzyme treatments influenced the color, enhancing the red hues in red grape juices. Enzyme treatments also improved the antioxidant capacity of grape juices, especially in Aurora and Muscaris, although the effect on polyphenol content was more dependent on the variety of grapes, with red varieties showing higher levels of polyphenols than white varieties. These findings highlight the significant role of both enzyme treatments and grape variety in determining the quality and health-promoting properties of grape juice.