Evolution of Physicochemical Properties and Phenolic Maturity of Vilana, Vidiano, Kotsifali and Mandilari Wine Grape Cultivars (Vitis vinifera L.) during Ripening.

Determining the optimum harvest time is a significant factor affecting the quality of the grapes and the wine. Monitoring the evolution of grapes' physicochemical properties and phenolic maturity during ripening could be a valuable tool for determining the optimum harvest time. In this study, the total phenolic content, antioxidant activity, flavonols, flavanols, anthocyanins and resveratrol content were determined during the last weeks of ripening for the white cultivars Vilana and Vidiano, as well as for the red cultivars Kotsifali and Mandilari (Vitis vinifera L.). According to the results, an early harvest for the white cultivars and a late harvest for the red cultivars may increase the total phenolics and trans-resveratrol content in grapes and wine. An early harvest would be desirable to maintain high flavanols content and high levels of antioxidant activity in the grapes' skin and seeds. Conversely, a late harvest for the red cultivars may be desirable to increase the total flavonols and anthocyanin content in grapes and wines.

Farming System Effect on the Incidence of Aspergillus carbonarius on Kotsifali Grapes and Ochratoxin A Occurrence in Wines of Crete.

ABSTRACT: During grape cultivation and wine production, the most effective way to prevent ochratoxin A (OTA) contamination of grapes and wine is to control ochratoxigenic fungal species, especially Aspergillus carbonarius, using appropriate cultivation techniques. In this study, the influence of an organic farming system (OFS) and an integrated farming system (IFS) on the incidence of A. carbonarius on grapes, and OTA contamination of wine, were examined. Mycological analysis of grapes collected from Kotsifali cultivar (Vitis vinifera L.) vineyards and grown under two farming systems (OFS and IFS) was performed over two growing seasons. For the same two growing seasons, OTA levels of representative wine samples from wineries located in the same area, made from the same cultivar (single varietal or covinificated with Mandilari), and grown under the two farming systems were determined. The results showed that the farming system had a significant influence on the incidence of A. carbonarius, with IFS being the most effective in the control of the fungus and the prevention of OTA occurrence in wine. This knowledge could offer viticulturists a useful tool to produce safer grapes, giving winemakers an incentive to make low-OTA wine.

Resveratrol: A Fair Race Towards Replacing Sulfites in Wines.

In recent years, significant efforts to produce healthier wines has led to the replacement or reduction of the addition of sulfites, using alternative substances or techniques. Resveratrol and related biophenols seem to be of great interest, since beyond their protective nature and contrary to sulfites they can positively affect consumer health. These bioactive phytochemicals are naturally produced in grapes as evolutionary acquired mechanisms against pathogens and UV irradiation. However, despite the efforts made so far attempting to develop economic and industrially adopted isolation techniques, available quantities of these biophenols for commercial use are still quite limited. Therefore, such molecules are still not able to meet the needs of industrial use due to their prohibitive marketable cost. In this review we summarize the efforts that have been made to biosynthesize these molecules through alternative, innovative ways. Increasing interest in modern biotechnological approaches has shed light on the exploitation of metabolically engineered microbial factories, instead of plants, to produce molecules of industrial interest. Such approaches, also reviewed here, are expected to lower the cost and appear promising to produce enough surplus to attract further oenological experimentation upon yielding functional wines. This development is expected to attract further industrial attention, continuing the race to partially or totally replace the external addition of sulfites. We also review important physicochemical properties of resveratrol in relation to enriching wines.

Evaluation of Eight Essential Oils for Postharvest Control of Aspergillus carbonarius in Grapes.

ABSTRACT: A range of fungal species are associated with postharvest spoilage of grapes. However, Aspergillus carbonarius is the primary fungus responsible for the contamination of grapes with ochratoxin A, a mycotoxin causing several confirmed negative health effects in humans and animals. Aiming to find a method, safe for consumers, to prevent postharvest decay and ochratoxin A contamination of grapes, the potential use of essential oils as preservatives was investigated. Essential oils of Origanum dictamnus (dittany), Origanum onites (oregano), Origanum microphyllum (marjoram), Thymbra capitata (thyme), Satureja thymbra (savory), Rosmarinus officinalis (rosemary), Laurus nobilis (laurel), and Salvia officinalis (sage) were tested. The essential oil components were identified by gas chromatography-mass spectrometry analysis. A first evaluation of the effectiveness of essential oils was performed in vitro at a range of concentrations up to 300 µL L-1. Based on the results of the in vitro tests, the four most effective essential oils (O. dictamnus, O. onites, T. capitata, and S. thymbra) were tested on Sultana grapes during postharvest storage. The four essential oils tested, which had carvacrol and/or thymol as a common component, at a high concentration significantly reduced or even inhibited growth of the fungus in all treatments. As revealed from the results, the essential oils of O. dictamnus, O. onites, and S. thymbra were the most effective, causing total inhibition of the growth of the fungus with a minimum concentration of 100 µL L-1, followed by the essential oil of T. capitata, which showed total effectiveness with a minimum concentration of 200 µL L-1. Although essential oils of O. microphyllum, L. nobilis, S. officinalis, and R. officinalis had a significant effect on the growth of A. carbonarius, they failed to inhibit its growth at any of the concentrations tested.