Antioxidant, Nutritional Properties, Microbiological, and Health Safety of Juice from Organic and Conventional 'Solaris' Wine (Vitis vinifera L.) Farming

Abstract

This study investigated the technological parameters, microbiological, and functional properties of juice from Solaris grapes grown under conventional and organic farming systems to assess how these cultivation methods influence juice quality. The one-year study focused on key aspects such as the levels of health-promoting polyphenols, the presence of mycotoxins, and pesticide residues. Organic grapes showed greater bacterial and fungal diversity, with significant differences in dominant genera. Sphingomonas and Massilia were the predominant bacteria across both systems, while Erysiphe was more common in conventional grapes, and Aureobasidium was abundant in both. Despite the presence of genes for mycotoxin production, no mycotoxins were detected in the juice or pomace. Organic juice exhibited significantly higher levels of polyphenols, leading to enhanced antioxidant properties and improved technological characteristics, including lower acidity and higher nitrogen content. However, residues of sulfur and copper, used in organic farming, were detected in the juice, while conventional juice contained synthetic pesticide residues like cyprodinil and fludioxonil. These findings highlight that while organic juice offers better quality and safety in terms of polyphenol content and antioxidant activity, it also carries risks related to residues from organic treatments, and conventional juice poses risks due to synthetic pesticide contamination.

Keywords: antioxidant activity; grapes; microbiome; mycotoxins; organic farming; plant protection; polyphenols.

Figure 1

Fruit of the Solaris cultivar on an organic plantation (Fot. I. Ochmian).

Figure 2

Organic vineyard plantation (Fot. I. Ochmian).

Figure 3

Network co-occurrence analysis between bacteria and fungi OTUs. Nodes (circles) describe bacterial (blue) or fungal (brown) OTUs. The size of nodes symbolizes the feature importance (normalized mean) for the entire sample. Edges (lines) between circles describe the correlation between them. The correlation increases with the intensity of the green color. The correlation increases with the intensity of the green color. Group I and Group II indicate OTUs with a strong intra-group correlation.

Figure 4

Copies of aflatoxins genes (A) and ochratoxin (B) (genes g dry weight) in organic and conventional juices. In the boxplot, from the first quartile to the third quartile, mean value, median, maximum, and minimum are marked.

Figure 5

Antioxidant activity in grape juice. * Mean values denoted by the same letter do not differ statistically significantly at 0.05, according to the t-test.

Figure 6

Agglomerative clustering analysis (Ward’s method based on Bray-Curtis dissimilarity matrix) of the distance between differences tested parameters representing organic and conventional juice. Samples were taken from 3 different places in each field (1, 2, 3).

Figure 7

PCA biplot shows the relation between the most abundant orders of bacteria, fungi, and tested parameters and their influence on ecological (EV 1, 2, 3) and conventional samples (CV 1, 2, 3). Blue points show variables (treatments), red lines with dots show vectors of observations (principal components).

Figure 8

Sulfur and copper solution on grape leaves in an organic plantation (Fot. I. Ochmian).