Issue link: http://winesandvines.uberflip.com/i/754815
58 WINES&VINES December 2016 WINEMAKING PRACTICAL WINERY & VINEYARD (W1 medium and W2 medium ) and Select 700 (W1 high and W2 high ). The values of total oxygen exposure (TOE) in the bottle for each wine are the sum of closure contribution and TPO. Closure contribution is intended as the combination of oxygen in- gress through the closure (OTR) and the amount of oxygen released from the closure following insertion into the bottleneck. These values were provided by the manufacturer and were calculated using the pro- cedure described by J.B. Dieval et al. 39 A slightly lower free SO 2 level was detected in W1 high and W2 high 10 months after bottling. Standard chemical analyses and spectrophotometric measurements Standard chemical analyses (alco- holic strength by volume, titratable acidity, pH, volatile acidity, free and total SO 2 and total polyphe- nols (Folin-Ciocalteu) were mea- sured according to the OIV Compendium of International Meth- ods of Wine and Must Analysis. 40 Condensed tannins (proantho- cyanidins, or PAs) were evalu- ated, 41 and total anthocyanins and SO 2 bleaching anthocyanins were d e t e r m i n e d a c c o r d i n g t o P. Ribéreau-Gayon and E. Stone- street. 42 Vanillin reactive flavans (VRF) were determined according to R. Di Stefano and S. Guidoni. 43 Color intensity and hue were evaluated according to Y. Glories methods. 44 All analyses were per- formed in triplicate. HPLC analysis of anthocyanins HPLC separation of monomeric anthocyanins also was performed according to the OIV Compendium of International Methods of Wine and Must Analysis. 40 Twenty µL of wine or calibration standards were injected into the column. All samples were filtered through 0.45 µm membrane filters into glass vials and immediately in- jected into the HPLC system. Human saliva Whole saliva was obtained by mix- ing saliva samples collected from six non-smoking volunteers (three males and three females). Electro- phoresis analyses were performed on the resulting supernatant. Saliva precipitation index determination The SPI was determined as re- ported by A. Rinaldi et al. 38 The calibration curve was obtained by the density reduction of two pro- tein bands selected from the pool of salivary proteins that were bet- ter correlated with sensory analy- sis. The densitometric analysis of proteins was performed before and after the interaction of saliva with five standard solutions containing tannic acid (2 to 10 g/L in water). Sensory analysis Selection and training ses- sions: Twenty-four subjects were recruited from a viticulture and enology class at the University of Naples to participate in the sen- sory sessions. All had experience as wine tasters, but with different backgrounds: six aroma research- ers, seven winemakers and 11 enology students. Panelists were trained to differentiate astrin- gency from bitterness and sour- ness using 3.0 g/L tannic acid, 0.25 g/L caffeine-monohydrate and 4.0 g/L tartaric acid as ex- amples of astringency, bitterness and sourness, respectively. Eighteen panelists indicated an ability to discriminate among these taste stimuli. Selected pan- elists trained with astringency rating evaluated overall astrin- gency of different concentrations (from 0.1 to 5.0 g/L) of commer- cial tannin on a nine-point scale (absent, very weak, weak, weak- moderate, moderate, moderate- strong, strong, very strong or extremely strong) first in water and then in wine solution. In each session five unknown samples (10 ml were presented in balanced random order at room temperature [18° ± 2° C] in black tulip-shaped glasses). The panel- ists were instructed to pour the whole sample in their mouth, hold it for eight seconds, expectorate and rate the perceived overall as- tringency using the nine-point scale. Panelists waited four minutes before rinsing with de-ionized water for 10 seconds twice and then waited at least 30 seconds before the next sample. Each sample was evaluated within five minutes. Astringency was expressed as the maximum intensity perceived. The data obtained were used for assessing the reliability and consis- tency of the panelists, which were considered acceptable (P < 0.05 for reproducibility of scores of rep- licate samples). The accuracy of rating was monitored with use of standards during each tasting ses- sion, consisting of three commer- cial tannin wine solutions (very weak astringency = 0.1 g/L; mod- erate astringency = 2.5 g/L; and extremely strong astringency = 5.0 g/L) to provide reference for three points on the nine-point scale. Evaluations of panel perfor- mance were based on a one-way random model under the assump- tion that panelists are homogeneous. The tendency toward consistency in the repeated measurements of the sample was referred to as the reli- ability. The reliability coefficient was used for assessing performance of the panel. 45 Sensory evaluation ses- sions: At the beginning of each session, panelists tasted three so- lutions for astringency. The same procedure and conditions were applied for red wine evaluation. During the eight tasting sessions, three experimental wines were evaluated in duplicate. Statistical analysis All of the data are expressed as the arithmetic average ± standard deviation of three replicates. Anal- ysis of variance was performed on phenolic compound and sensory data. Fisher's Least Significant Differences procedure was used to discriminate among the means of the variables. Effect of MOx on phenolics and astringency of bottle-aged red wines What is the effect of micro-oxy- genation on changes in phenolic composition, color, SPI and astrin- gency during aging? An increase of color intensity and total antho- cyanin content was observed in both wines three months after the MO1 treatment. A significant increase previ- ously has been reported in the color intensity just after the mi- cro-oxygenation treatment, 18,46,47 which was due to the formation of new pigments such as those derived from the combination of anthocyanins and flavanols via the formation of ethyl bridges. 48 The higher values of total antho- cyanins in MOx wines confirmed this hypothesis. Increased levels of micro-oxy- genation to treatment MO2 re- sulted in a significant decrease of SO 2 decolorable anthocyanins. Therefore, the higher levels of oxygen, the higher the formation of new anthocyanin-derived pig- ments stable to pH changes and bisulfite bleaching. 14 After 42 months, all wines showed an increase of hue and a decrease of total and SO 2 decolor- able anthocyanins. However, the effect of micro-oxygenation on color intensity and hue for both wines and for total and SO 2 decol- orable anthocyanins for Wine A was no longer detected. Several authors have observed that, during aging in barrel and/ or bottle for several months, the differences between MOx wines and respective control wines were NOMINAL OTR VALUES FOR THE CLOSURES Nominal OTR values measured in 100% oxygen Select 300 0.011 ml per day Select 500 0.017 ml per day Select 700 0.021 ml per day FREE SO 2 VALUES OF WINES W1 AND W2 10 MONTHS AFTER BOTTLING Wine Wine 1 Wine 1 Wine 1 Wine 2 Wine 2 Wine 2 Closure Select 300 Select 500 Select 700 Select 300 Select 500 Select 700 Free SO 2 22 mg/L 22 mg/L 20 mg/L 19 mg/L 17 mg/L 15 mg/L Closures were designed to allow oxygen transmission to match wine style. Wine 2 showed greater responsiveness to the various closures used.