Potential Associations among Bioactive Molecules, Antioxidant Activity and Resveratrol Production in Vitis vinifera Fruits of North America

Grapes (Vitis vinifera L.) are rich in bioactive molecules contributing to health benefits. Consumption of grapes is linked to reduced incidence of cardiovascular diseases. Studies on table grape cultivars are limited although much attention in research was focused on the wine industry. Bioactive effects of grapes as anti-inflammatory, anticarcinogenic, cardioprotective, vasorelaxant, phytoestrogenic and neuroprotective have also been reported. For example, resveratrol is a natural food ingredient present in grapes, with high antioxidant potential. Here we conducted an exploratory study to investigate bioactive molecules, antioxidant activity and the association between constitutive stilbene synthase (STS) gene expression and the resveratrol biosynthesis in selected table grape varieties in North America. The phenolic compounds, fatty acid composition and antioxidant activity of four grape varieties were compared. Red Globe variety was rich in unsaturated fatty acids as well as phenolic compounds such as caffeic acid, quercetin and resveratrol. Meanwhile, the constitutive expression of grape stilbene synthase gene was higher in Flame and Autumn Royal where resveratrol content of these cultivars was relatively low compared to the Red Globe variety. This study shows the potential links in grape antioxidant activity and resveratrol production, but more studies are necessary to show the association.

Determining the pectinesterase enzyme activity when storing table grape varieties depending on the degree of ripening

Grapes are rich in easily digestible carbohydrates, mineral compounds, vitamins, phenolic compounds. and other vital components. It is known that fresh grapes can be used from September to December. To prolong the terms of consumption of this valuable raw material, the most appropriate varieties and conditions for storing grapes have been determined. White, pink, and red grape varieties were taken as the object of research. The changes in the activity of the pectinesterase enzyme were determined depending on the degree of ripening of table grape varieties, the change in the pectinesterase enzyme during storage of table grape varieties in various variants was investigated. Statistical processing and calculation of variations in the indicators of changes in the activity of the enzyme pectinesterase were performed, depending on the degree of ripening of grapes of the Shamakhi Marandi variety. During the study, the pectinesterase enzyme remained more stable in mature varieties. This means that in ripe table grape varieties, the absorption of nutrients in the respiratory process is significantly slowed down. However, as they mature, the activity of the pectinesterase enzyme gradually increases. Therefore, for long-term storage in refrigerated chambers, fully ripe varieties of table grapes were used; to this end, grapes of the white Ganja table variety, the pink Shamakhi Marandi variety, and the red Black Asma variety are more suitable. The comparison of the investigated variants showed that table grape varieties, when stored in a refrigerated chamber in a controlled atmosphere, at 3–4 % CO2 and 2–3 % O2, retain better quality than other variants. When storing table grape varieties of various variants in the refrigerator, the enzyme activity decreases but is not completely suppressed.

The Biases in Flavonoids and Anthocyanin Biosynthesis of a Red Flesh Table Grape Revealed by Metabolome and Transcriptome Co-analysis

Red flesh is a welcomed fruit trait, yet the regulation of red flesh formation in grape is not well understood. ‘Mio Red’ is a seedless table grape variety with light red flesh and blue-purple skin, the flesh color developed in the late stage of berry ripening, remarkably later than the skin coloring at veraison. The flesh and skin flavonoids metabolome and the transcriptome were analyzed. A total of 173 flavonoids including 17 anthocyanins were identified, 68 were found significantly different (Fold change ≥ 2 or ≤ 0. 5, VIP ≥ 1). Quercetin 3-O-glucoside, epicatechin-epiafzelechin, apigenin 6,8-C-diglucoside and hesperetin 5-O-glucoside were of higher content in the flesh, while the rest flavonoids were of higher content in the skin. The main anthocyanin in the flesh was pelargonidin derivatives in contrast to peonidin derivatives in the skin. Transcriptome comparison recruited 3970 differentially expressed genes (DEGs, log2Fold change > = 1, FDR < 0.05, FPKM ≥ 1), among them 57 were structural genes of flavonoid metabolism pathway. Two anthocyanin synthase (ANS) DEGs were annotated, ANS1 (Vitvi11g00565) and ANS2 (Vitvi02g00435) led the expression in the flesh and skin respectively. In the flesh, anthocyanin biosynthesis structural gene UFGT, positive regulators MYBA1/2/3, and anthocyanin transporters GST14 and MATE5 were of significantly lower expression, while negative regulators MYBC2-L1 and MYB3 were of higher transcription. The results of this study provide new information in the coloring mechanism of red flesh grape and assisting breeding of future table grapes having higher content of phytonutrient providing the health benefit as red wines.

Pre-Anthesis Cytokinin Applications Increase Table Grape Berry Firmness by Modulating Cell Wall Polysaccharides

The use of plant growth regulators (PGRs) is widespread in commercial table grape vineyards. The synthetic cytokinin CPPU is a PGR that is extensively used to obtain higher quality grapes. However, the effect of CPPU on berry firmness is not clear. The current study investigated the effects of pre-anthesis applications (BBCH15 and BBCH55 stages) of CPPU on ‘Thompson Seedless’ berry firmness at harvest through a combination of cytological, morphological, and biochemical analyses. Ovaries in CPPU-treated plants presented morphological changes related to cell division and cell wall modification at the anthesis stage (BBCH65). Moreover, immunofluorescence analysis with monoclonal antibodies 2F4 and LM15 against pectin and xyloglucan demonstrated that CPPU treatment resulted in cell wall modifications at anthesis. These early changes have major repercussions regarding the hemicellulose and pectin cell wall composition of mature fruits, and are associated with increased calcium content and a higher berry firmness at harvest.

Classification of Browning on Intact Table Grape Bunches Using Near-Infrared Spectroscopy Coupled With Partial Least Squares-Discriminant Analysis and Artificial Neural Networks

Table grape browning is a complex physiological disorder that occurs during cold storage. There is a need to investigate novel and innovative ways to manage the problem that hampers the progressive and sustainable growth of table grape industries. Given the complex nature of the browning phenomenon, techniques such as near-infrared (NIR) spectroscopy can be utilized for the non-destructive classification of different browning phenotypes. In this study, NIR coupled with partial least squares discriminant analysis (PLS-DA) and artificial neural networks (ANN) were used to classify bunches as either clear or as having chocolate browning and friction browning based on the spectra obtained from intact ‘Regal Seedless’ table grape bunches that were cold-stored over different periods. Friction browning appears as circular spots close to the pedicel area that are formed when table grape berries move against each other, and chocolate browning appears as discoloration, which originates mostly from the stylar-end of the berry, although the whole berry may appear brown in severe instances. The evaluation of the models constructed using PLS-DA was done using the classification error rate (CER), specificity, and sensitivity and for the models constructed using ANN, the kappa score was used. The CER for chocolate browning (25%) was better than that of friction browning (46%) for weeks 3 and 4 for both class 0 (absence of browning) and class 1 (presence of browning). Both the specificity and sensitivity of class 0 and class 1 for friction browning were not as good as that of chocolate browning. With ANN, the kappa score was tested to classify table grape bunches as clear or having chocolate browning or friction browning and showed that chocolate browning could be classified with a strong agreement during weeks 3 and 4 and weeks 5 and 6 and that friction browning could be classified with a moderate agreement during weeks 3 and 4. These results open up new possibilities for the development of quality checks of packed table grape bunches before export. This has a significant impact on the table grape industry for it will now be possible to evaluate bunches non-destructively during packaging to determine the possibility of these browning types being present when reaching the export market.

Chemical, Microbiological and Volatile Composition of Kefir-like Beverages Produced from Red Table Grape Juice in Repeated 24-h Fed-batch Subcultures

The aim of this work was to study the production of kefir-like beverage by fed-batch fermentation of red table grape juice at initial pHs of 3.99 (fermentation A) and 5.99 (fermentation B) with kefir grains during four repeated 24-h fed-batch subcultures. However, all kefir-like beverages (KLB) were characterized by low alcoholic grade (&le; 3.6%, v/v) and lactic and acetic acid concentrations. The beverages obtained from fermentation B had lower concentrations of sugars and higher microbial counts than the KLB obtained in fermentation A. In addition, the KLB from fermentation B were the most aromatic and had the highest contents in alcohols, esters, aldehydes and organic acids compared to the non-fermented juice and KLB from fermentation A. These results indicate the possibility of obtaining red table grapes KLB with their own distinctive aromatic characteristics and a high content in probiotic viable cells, contributing to the valorization of this fruit.