Microbiological, Antioxidant, Nutritional Properties, and Health Safety of Juice from Organic and Conventional Vitis vinifera L. Farming

The study involved a comparison of the chemical, physical, microbiological, and functional attributes of must extracted from Solaris cultivar grapes cultivated under both conventional and organic farming systems. This study aimed to determine the influence of cultivation methods on various must properties, including the levels of health-promoting polyphenols and health-threatening mycotoxins and pesticide residues. It was observed that the organic grapes hosted a greater diversity and quantity (OTUs) of bacteria and fungi. The predominant bacteria were Sphingomonas (with similar numbers in both crops) and Massilia (more abundant in grapes from the conventional crop). These two bacterial groups collectively accounted, on average, for about 40% of all OTU sequences detected. Lower levels of bacteria of the genera Hymenobacter and Pseudomonas and others colonized the grapes. Among the fungi, Erysiphe and Aureobasidium were dominant, comprising about 50–70% of all detected taxa. Notably, Erysiphe was predominantly found in conventionally grown grapes, while Aureobasidium, Mycosphaerella, and Botryotinia were present in comparable quantities in fruit from both types of crops. No mycotoxins were detected in the must or marc, despite the presence of genes responsible for aflatoxin and ochratoxin biosynthesis in both types of grape juice. The organic must exhibited significantly higher levels of polyphenols and displayed improved antioxidant properties and technological characteristics. Moreover, sulfur and copper used in the protection of the organic plantation passed from the fruit surface into the must. Also, pesticide residues, namely cyprodinil and fludioxonil from conventional cultivation, were detected in the must.