Tatjana Košmerl

Contribution of SO2 to antioxidant potential of white wine

The reactivity of SO2 with the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and in Folin Ciocalteu (FC) assays was analysed under different experimental conditions. There was significantly higher reactivity between SO2 and DPPH in buffered methanol than in methanol alone. When DPPH and FC assays were performed in a mixture of caftaric acid and SO2, there were synergistic effects that were more pronounced with the FC assay. Phenolics are an important parameter of wine quality, and their accurate characterisation in wine is essential. Analysis of white wines with DPPH and FC assays overestimates the contribution of phenolics to the antioxidant potential (AOP). SO2 contributes (from 20% to 45%) to the AOP of the white wines analysed. As SO2 reactivity depends highly on buffer composition, pH, time of incubation and other compounds, e.g. phenolics and aldehydes, different experimental protocols can produce large variations in AOPs, and therefore control of experimental conditions is extremely important.

Influence of Solvent Composition on Antioxidant Potential of Model Polyphenols and Red Wines Determined with 2,2-Diphenyl-1-picrylhydrazyl

Solvent composition has a large influence on measured antioxidant potential (AOP) of model polyphenols and red wines with 2,2-diphenyl-1-picrylhydrazyl (DPPH). We have shown that incorporation of aqueous buffer in the assay medium results in higher reactivity of catechin and caftaric acid, which are among major polyphenolic constituents of wines. Consequently, AOPs of red wines determined after 60 min of incubation at 25 °C in buffered methanol are 1.5-1.6-fold of values determined in methanol. Even in buffered methanol, wine polyphenols are not fully oxidized after 60 min. Only about half of Trolox equivalents were determined in comparison to the Folin-Ciocalteu assay. Buffer composition, pH, time of incubation, temperature, and concentration of antioxidants and DPPH all contribute to the resulting value of the AOP being standardized or at least strictly reported because minor differences in experimental procedures can account for large variations in determined AOP with DPPH for the same samples.

Impact of Alternative Skin Contact Procedures on the Aroma Composition of White Wine

Zelen, Ribolla Gialla and Malvasia Istriana, grapes from the Vitis vinifera (L.) varieties, were subjected to four processes involving grape skin contact. Fresh and fruity young wines were produced by adding 6% or 12% grape berries, respectively, during alcoholic fermentation, freezing the pomace (Fp) and the freezing whole grapes (Fg). Wine-free volatile aromatic compounds were determined using two extraction techniques coupled to gas chromatography (GC). These aromatic compounds and wine standard chemical parameters were compared to control wines produced without skin contact. Esters, higher alcohols, terpenes, volatile phenols and C6 alcohols proved to be the most important sensorial odorants in wines. Both the content of aromatic compounds and the odour activity values showed some positive effects from skin contact. The freezing of the grapes and addition of 12% grape berries proved most effective for Zelen and Malvasia Istriana, producing a more intensive fruity and floral odour, a less intensive solvent odour and additional freshness. The same processes resulted only in additional fruitiness or a less intensive solvent odour in Ribolla Gialla while the lowest concentrations of grape derived terpenes were achieved for this variety. The three varieties were most affected by freezing processes. During the sensorial evaluation, the wines that had been subjected to skin contact were generally preferred to the control wines.

The response of Monoterpenes to Different Enzyme Preparations in Gewürztraminer (Vitis vinifera L.) Wines

The α-terpineol, linalool, nerol and geraniol, which are the main aromatic monoterpenes in the grapevine variety Gewurztraminer, were determined in the grapes, must and wine after treatment with six different pectolytic enzymes [Lallzyme-β (‘Lall’); Rohavin VR-C (‘VRX’), Rohapect D5L (‘D5L’), Rohavin MX (‘MX’), Rohapect VRC (‘VRC’), Endozym cultivar A (‘Cult. A’)], and after treatment with β-glucosidase (βG, EC 3.2.1.21). The concentrations of monoterpenic compounds were determined by solid-phase microextraction (SPME) and GC-MS. The most abundant monoterpene in the grapes of Gewurztraminer was geraniol (66.7 μg/L), followed by nerol (13.3 μg/L), α-terpineol (7.8 μg/L) and finally linalool (3.3 μg/L). Gewurztraminer wine from must treated with the Lall enzyme preparation was the most aromatic, which was also confirmed by chemical and sensory analysis in which the concentrations of nerol (45.9 μg/L), geraniol (31.8 μg/L), α-terpineol (10.5 μg/L) and linalool (6.1 μg/L) were determined. The wines produced from must treated chemically with enzymes showed higher concentrations of many of the monoterpene compounds compared to the control, although the sensorial analysis did not affirm this convincingly.

Influence of consumer regiocentrism on perceived value of wine

Purpose The purpose of this paper is to identify which dimensions of perceived value of wine dominate in the perception of wine consumers from two distinctive wine producing regions and to examine how their respective regional identity, consumer regiocentrism (CR) and perceived value of wine are inter-related in determining consumers’ preference of wine. Design/methodology/approach A sample of 221 wine consumers from two Slovenian wine regions with contrasting wine-related and social specificities responded to an online questionnaire. Besides the wine-related consumer behaviour variables, the questionnaire contained CR, regional identity and consumer perceived value measurements, based on adapted CETSCALE, regional identity and PERVAL scales. The scales were validated, and structural equation modelling was used to evaluate the relationships between the constructs. Findings Perceived value of wine was found to consist of three dimensions: emotional-social, quality-price and terroir, which differ from those previously observed among wine consumers from the USA. Regional identity was found to be a direct antecedent of CR, and CR directly affects all three dimensions of perceived value of wine; these findings were evident in the original model and in both studied wine regions. Research limitations/implications Future research should extend the model to include other possible antecedents of CR and study its effects on different consequences, especially purchasing intent. Future studies would benefit by adding more indicators into scales to measure CR and regional identity to improve the model fit. Originality/value This study contributes to a better understanding of perceived value of wine and extends the current knowledge of how social and psychological phenomena interact when evaluating wine. The results herein should enable marketers to develop more sophisticated positioning strategies and support their decision making for an appropriate market approach.

The impact of different commercial yeasts on quality parameters of Montenegrin red wine – Vranac and Kratošija

The influence of three different commercial yeasts (BDX, BM4X4 and ICV D21), on quality parameters of wines from varieties Vranac and Kratošija were studied during two consecutive vintage years. The basic quality parameters of grape must (sugar content, total acidity, pH, tartaric and malic acid) and the wine quality parameters (alcohol content, total dry extract, glycerol, pH, total polyphenols and total anthocyanins) were determined after each phase of vinifications: after alcoholic and malolactic fermentation as well as after three months of wine maturation. There are significant differences in quality parameters of grapes and wines between vintages 2012 and 2013. Higher content of total dry extract and glycerol in wines after completion of alcoholic fermentation was achieved in vintage 2013. In vintage 2013, the highest content of total polyphenols (3.75 and 2.98 g L-1) and anthocyanins (1247 and 713 mg L-1) in Vranac wine after malolactic fermentation and after three months of maturation, were achieved by yeast BM4X4, while the highest total polyphenols (2.14 and 1.92 g L-1) and anthocyanins content (527 and 262 mg L-1, respectively) was achieved by BDX strain in Kratošija wine. The results of sensory analysis showed no significant differences between the used yeast strains and studied. Surprisingly, the wines of vintage 2012 are even slightly better sensory evaluated. Correspondence to: Sanja ŠUĆUR, “13. Jul Plantaže”, Sector for Development, Put Radomira Ivanovića 2, 81000 Podgorica, Montenegro; E-mail: sucursanja@yahoo.com