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Bednarova A.,University of Trnava | Kranvogl R.,University of Maribor | Voncina D.B.,University of Maribor | Jug T.,Institute for Agriculture and Forestry | Beinrohr E.,University of Trnava
Acta Chimica Slovenica | Year: 2013

Determination of the product's origin is one of the primary requirements when certifying a wine's authenticity. Significant research has described the possibilities of predicting a wine's origin using efficient methods of wine components' analyses connected with multivariate data analysis. The main goal of this study was to examine the discrimination ability of simple enological descriptors for the classification of Slovenian red and white wine samples according to their varieties and geographical origins. Another task was to investigate the inter-relations available among descriptors such as relative density, content of total acids, non-volatile acids and volatile acids, ash, reducing sugars, sugar-free extract, SO2, ethanol, pH, and an important additional variable - the sensorial quality of the wine, using correlation analysis, principal component analysis (PCA), and cluster analysis (CLU). 739 red and white wine samples were scanned on a Wine Scan FT 120, from wave numbers 926 cm-1 to 5012 cm-1. The applied methods of linear discriminant analysis (LDA), general discriminant analysis (GDA), and artificial neural networks (ANN), demonstrated their power for authentication purposes. Source

Mujic I.,Colegium Fluminense Polytechnic of Rijeka | Bavcon Kralj M.,Institute for Agriculture and Forestry | Jokic S.,F. Kuhaca 20 | Jug T.,Institute for Agriculture and Forestry | And 3 more authors.
Journal of Food Science and Technology | Year: 2012

The aromatic profile of volatiles in dried figs varieties Bružetka Bijela and Zimnica were characterised by headspace solid-phase (HS-SPME) procedure with gas chromatography–mass spectrometry analysis (GC-MS). The volatile compounds were distributed by distinct chemical classes, including alcohols, aldehydes, esters, terpenic compounds, and other compounds. The figs were dried in a pilot plant cabinet dryer. Prior to drying process, figs were pre-treated by sulphur dioxide, immersed in solution of citric acid and ascorbic acid, respectively. Several mathematical thin-layer drying models, available in the literature, were fitted to experimental data of figs, implementing non-linear regression analysis techniques. The results showed that pre-treatments of figs decrease significantly the drying time. The best thin-layer drying model in terms of fitting performance was Wang and Singh model. The major volatile compound in dried figs was benzaldehyde. After benzaldehyde, the most abundant aldehyde in dried figs was hexanal. The comparison among dried figs showed the highest abundance of aldehydes, in general, in non-treated (control) dried figs compared to pre-treated samples. Furthermore, ascorbic acid was the most efficient in preserving esters and alcohols in case of Bružetka Bijela, whereas in case of Zimnica, sulphur dioxide was in advance compared to ascorbic acid. Ethyl acetate was the most abundant ester found in dried figs. Among other compounds, 2-butanone,3-hydroxy was the most abundant identified volatiles. Linalool, as the only identified terpen, was in case of both dried fig varieties, preserved by immersion into ascorbic acid. The immersion into citric acid has not been so successful in volatiles conservation. © 2012, Association of Food Scientists & Technologists (India). Source

Bednarova A.,University of Trnava | Kranvogl R.,University of Maribor | Brodnjak-voncina D.,University of Maribor | Jug T.,Institute for Agriculture and Forestry
Nova Biotechnologica et Chimica | Year: 2014

The determination of the sensorial quality of wines is of great interest for wine consumers and producers since it declares the quality in most of the cases. The sensorial assays carried out by a group of experts are time-consuming and expensive especially when dealing with large batches of wines. Therefore, an attempt was made to assess the possibility of estimating the wine sensorial quality with using routinely measured chemical descriptors as predictors. For this purpose, 131 Slovenian red wine samples of different varieties and years of production were analysed and correlation and principal component analysis were applied to find inter-relations between the studied oenological descriptors. The method of artificial neural networks (ANNs) was utilised as the prediction tool for estimating overall sensorial quality of red wines. Each model was rigorously validated and sensitivity analysis was applied as a method for selecting the most important predictors. Consequently, acceptable results were obtained, when data representing only one year of production were included in the analysis. In this case, the coefficient of determination (R2) associated with training data was 0.95 and that for validation data was 0.90. When estimating sensorial quality in categorical form, 94% and 85% of correctly classified samples were achieved for training and validation subset, respectively. © University of SS. Cyril and Methodius. Source

Jug T.,Institute for Agriculture and Forestry | Rusjan D.,University of Ljubljana
Emirates Journal of Food and Agriculture | Year: 2012

UV radiation, as a natural component of sunlight and frequently mentioned in relation with climatic changes, has numerous regulatory effects on grapevine physiology and biochemistry. In last decades many studies gave significant advances in the understanding of the effects of UV radiation on compounds of the primary and secondary metabolism, especially those which impact grape and wine quality. Mechanisms of plant responses to solar UV-B radiation are therefore disadvantageous: such as inhibition effect on plant growth, but also advantageous such as accumulation of phenolic compounds and improved resistance to pathogenes. UV-B affects the secondary metabolism of plants and thus indicating that solar UV-B is to be regarded as an environmental challenge rather than a damage-inducing source of stress in vitiviniculture. UV irradiation might have a positive influence on grape "healthiness" or composition and consequently a positive impact on wine quality. This review provides a synopsis of the effect of UV radiation associated variables on grapevine physiology and biochemistry as potential key factor in the future of global grape production. Source

Mujic I.,Colegium Fluminense Polytechnic of Rijeka | Bavcon Kralj M.,Institute for Agriculture and Forestry | Jarni K.,University of Ljubljana | Jug T.,Institute for Agriculture and Forestry | Prgomet Z.,Colegium Fluminense Polytechnic of Rijeka
International Journal of Food Science and Technology | Year: 2012

The aromatic profile of volatiles in fresh figs (FF), fresh figs frozen in liquid nitrogen (NF) and dried figs (DF) (dark variety Petrovača Crna) was characterised by HS-SPME followed by GC-MS. Figs were dried in a pilot plant cabinet dryer using different pre-treatments to preserve the dried fruit: sulphuring and immersion in a solution of citric acid and ascorbic acid (separately). The adaptability of thin-layer drying models to whole figs was investigated. Fresh figs and fresh figs frozen in liquid nitrogen differed mainly in the amount of aldehydes. The highest abundance of volatile compounds in dried figs was found in figs pre-treated with sulphur dioxide and the control, compared to samples immersed in the acid solutions. Preservation was the most successful for the group of terpenes and terpenic compounds, quite good for some esters and ketones, whereas aldehydes were not affected by the used pre-treatment. © 2012 The Authors. International Journal of Food Science and Technology © 2012 Institute of Food Science and Technology. Source

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