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This work is designed to reveal the varietal characteristics of terpene glycosides (TGs) in ripe Meili grapes. TGs in grape skins were extracted using three ethanol/water solvents, purified and enriched using XAD-2 resin, and collected using ethyl acetate/methanol (9:1, v/v). The aglycones released from TGs were analyzed by headspace solid-phase microextraction–gas chromatography–mass spectrometry (HS-SPME–GC–MS). TGs were detected by ultra-high-performance liquid chromatography–quadrupole time-of-flight mass spectrometry (UPLC–Q-TOF-MS), the identification was conducted by both mass fragmentation and TGs database, and the quantitation was realized by octyl-β-d-glucopyranoside. Results showed that 19 aglycones for TGs were found in grape skins by GC–MS, which was mainly monoterpenol with molecular formula C10H18O (linalool, l-α-terpineol, geraniol, nerol, etc.), C10H20O (citronellol), and C10H18O2 (pyranoid/furanoid linalool oxide, etc.). C10H18O aglycones may be the most stable ones, and linalool was the most abundant, occupying 44.88–47.99% of the total content. Forty-nine TGs were detected by UPLC–Q-TOF-MS. Monoterpenol pentosyl-glucosides were the main TGs, especially C10H18O2 pentosyl-glucoside, which constituted 51.94–52.72% of the total concentration. [ABSTRACT FROM AUTHOR]

The diffusion of valuable components, from the grape skin into the must is limited by a barrier formed by the cell walls. The deconstruction of the cell wall matrix during fruit ripening probably involves the synergistic action of different enzymatic activities. A degradation of cell wall from grape skin during winemaking by addition of several different enzymatic activities could be deduced. However, the action of the maceration enzymes seems contradictory. This work studies the effectiveness of the addition of three purified enzymatic activities on skin cell wall degradation from Monastrell grapes, considering the possible influence of the cell wall composition and morphology, as well as the potential enzymatic synergy. A synthetic solution (5 g/L tartaric acid; pH value 3.6) with Monastrell grape skins was supplemented with polygalacturonase, cellulase and pectin methylesterase enzymatic activities, together with its paired combinations, and compared to a control sample. Oligouronides, color intensity and total phenolic index (TPI) from the synthetic solution were measured at 12, 24, 36, 60, 84 and 120 h for all the experiences. Cellulase activity acts sooner in Monastrell grapes skin, compared to polygalacturonase enzymatic activity. Concerning combined treatments, all enzymatic combinations show more or less a synergy. This synergistic effect is higher when polygalacturonase + cellulase enzymatic combination is added, increasing oligouronides amount, color intensity and TPI between 12 and 84 h. The other two combinations show an increase for TPI and color intensity only at 24 h. Polygalacturonase + pectin methylesterase combination presents higher oligouronides content only at 36 h. [ABSTRACT FROM AUTHOR]

This paper studies the influence of different maceration times (5, 10 and 20 days) during the elaboration of Monastrell, Syrah and Cabernet Sauvignon wines on the proanthocyanidin composition and sensory characteristics of the resulting wines. Significant differences were found between wines elaborated with different maceration times. The different maceration times affected the qualitative and quantitative proanthocyanidin composition of the resulting wines, the total proanthocyanidin content increasing with the maceration time. The percentage of skin-derived proanthocyanidins was always higher than that of seed-derived proanthocyanidins for all the maceration time assayed, although the contribution of seed proanthocyanidins to wine composition increased for the longest maceration time. However, the study also shows that differences exist between wines elaborated with the same maceration time but with different varieties, indicating the importance of two factors, the initial concentration of grape phenolic compounds and their extractability, on the final concentration of wine proanthocyanidins. In this way, the wines obtained from Syrah had the highest proanthocyanidin content compared with the corresponding wines from Cabernet Sauvignon or Monastrell, even though Syrah grapes presented the lowest proanthocyanidin content in skins and similar seed proanthocyanidin content to Cabernet and Monastrell grapes. [ABSTRACT FROM AUTHOR]