SPME-GC method as a tool to differentiate VOC profiles in Saccharomyces cerevisiae wine yeasts

The aim of this work was to study the variability of 36 Saccharomyces cerevisiae wild strains isolated from different grape varieties and from two very distant zones, located in Northern and Southern Italy. The strains were differentiated on the basis of parameters of technological interest, such as resistance to antimicrobial compounds frequently present in wine, and the production of volatile aromatic compounds (VOC), determined by SPME procedure in the experimental wines obtained by inoculated fermentations. The VOC profile allowed to differentiate the yeasts in function of isolation area: S. cerevisiae isolated from Southern Italy grapes were able to produce more volatile compounds than those from Northern Italy. The compounds synthesized by all the yeasts, besides the ethanol, were 3-methyl-1-butanol and ethyl acetate. The production of acids during the alcoholic fermentation was a characteristic of Southern yeast strains. The screening of S. cerevisiae strains for technological parameters, such as sulphur dioxide, copper and ethanol resistance or hydrogen sulphide production, revealed similar behaviour for sulphur dioxide resistance among Northern and Southern S. cerevisiae strains. Copper resistance and sulphur dioxide production were correlated to isolation area: S. cerevisiae ‘‘Northern’’ strains showed higher copper resistance and lowest hydrogen sulphide production than that exhibited from ‘‘Southern’’ strains

Pulsed electric field treatment enhanced stilbene content in Graciano, Tempranillo and Grenache grape varieties

The purpose of this paper was to study the effect of pulsed electric fields (PEF) on the stilbene content of three grape varieties. For this purpose, four different PEF treatments were applied using a continuous system over three varieties, Graciano, Tempranillo and Grenache, destemmed and crushed. In addition, the influence of PEF on their physicochemical composition was studied. PEF treatments did not affect the pH or total acidity of Graciano, however, musts from Tempranillo and Grenache had higher pH values and lower total acidity. In the three varieties, all treatments resulted in an increase of potassium content, deeper colour intensity and total polyphenol index and lower tonality, more pronounced in the treatments with higher time and energy. The stilbene content of the must significantly increased with respect to the control. This increase depended on the variety and the treatment applied. Tempranillo increased up 200% the total stilbene concentration, Grenache 60% and Graciano 50%. For the three varieties, the treatment with the highest time and energy was the most effective on the total stilbene extraction. These results indicate that PEF could be a suitable technology for obtaining musts with deeper colour and higher phenolic content, including resveratrol and piceid. © 2013 Elsevier Ltd. All rights reserved

The impact of different barrel sanitation approaches on the spoilage microflora and phenols composition of wine

Careful control of spoilage microflora inside wine containers is a key issue during winemaking. To date, attention has been paid to the development of an effective protocol for the eradication of spoilage agents, especially Brettanomyces, from barrels. Few studies have taken into account the modifications caused by sanitation treatments in wine and wood barrels. In the present study the effects of two sanitation treatments (ozone and sodium hydroxide) on barrel spoilage microflora and the composition of the wine stored inside them were evaluated. The phenols of wine (38 compounds) were characterised using a UHPLC–MS during the first 3 months of wine ageing, to see possible alterations in composition due to the chemical exchange from wood to wine in presence of sanitising agents. With the same scope, a panel of 13 judges carried out sensorial analysis of wines. The results showed that the tested treatments had little effect on the organoleptic characteristics of wines, but underline the different performance of the sanitation treatments in terms of eradicating microorganisms

Chemical and physical methodologies for the replacement/reduction of sulfur dioxide use during winemaking: review of their potentialities and limitations

Sulfur dioxide (SO 2 ) is probably one of the most versatile and efficient additives used in winemaking due to its antiseptic and antioxidant properties. This compound is also important for minimizing phenolic polymerization rate and color loss during wine aging. However, allergies caused by SO 2 -derived compounds, namely the sulfites, are becoming more frequent, causing symptoms such as headaches, nausea, gastric irritation, and breathing difficulties in asthma patients. Consequently, the legislated maximum concentration of SO 2 allowed in wines has been gradually reduced. For this reason, it is crucial in a competitive global winemaking market strategy, to reduce or even eliminate the use of SO 2 as a preservative and to search for new healthier and safe strategies. This work gives an overview of the main methodologies that have been proposed so far and that have potential to be used in winemaking as an alternative to SO 2 . The addition of compounds such as dimethyl dicarbonate, bacteriocins, phenolic compounds, and lysozyme, and the use of physical methods, namely pulsed electric fields, ultrasound, ultraviolet radiation, and high pressure are discussed and critically evaluated