Highlights► Glycosidases of Oenococcus oeni are able to release terpenes from natural substrates. ► Bacterial glycosidases have a high capacity to release both primary and tertiary terpene alcohols. ► Both glucosidase and arabinosidase from O. oeni are more active in grape juice than glycosidases from Aspergillus niger. ► Riesling mash was treated with O. oeni glycosidases before alcoholic fermentation. ► Wines produced with the glycosidases from O. oeni received positive ratings by a professional panel.

The aim of this work was to study the combined application of a pulsed electric field (PEF) and an enzymatic treatment to white wine mash. The resulting impact of membrane permeabilisation by electroporation and pectin degradation by enzymes on fermentation behaviour and quality of white wine was assessed. The mash of two varieties, Traminer and Grüner Veltliner, was PEF treated (3 and 10 kJ/kg) using a continuous co-linear treatment chamber. Pectinases were added immediately afterwards and maceration was performed for 4 and 24 h. Various physico-chemical parameters were analysed at different stages of the production process and the impact of the combined treatment on volatile compounds such as esters and terpenes was analysed by gas chromatography-mass spectrometry and a sensory panel in the final white wine after bottling and storage. Regardless of the PEF treatment intensity, the variety and the maceration time, the release of juice was not significantly influenced. For Traminer, the fermentation time was reduced through the enhanced extraction of nitrogen from 322 to 359 mg/L due to PEF treatment (10 kJ/kg). The release of phenols which were localized in the pulp, were significantly more affected than phenols from the skin. Although the concentration of selective esters especially of the variety Traminer significantly increased, the sensory evaluation indicated no positive effect on the olfactory properties. Overall, the combination of PEF and enzyme pretreatment showed benefits in reducing the fermentation time and increasing the content of selective esters for Traminer.

In the course of the present study, filter layers with embedded zeolites (patented layer of the company Filtrox (Zwingen, Switzerland) with the brand name Fibrafix® TX) were tested for the elimination of the wine defects, cork taint (2,4,6-trichloroanisole), mouldy aroma (geosmin), and strong “animal” phenolic aromas (4-ethylphenol, 4-ethylguaiacol, 4-ethylcatechol). The test design allowed a comparison with conventional filter layers (sterile filter layers) in a small-scale trial (25 L) as well as in a large-scale trial (125 L). By means of gas chromatography-mass spectroscopy, not only the impact compounds of the wine faults were analysed, but also the loss of volatile substances such as 15 free monoterpenes, 34 ester compounds, and 24 wood flavours. Sensory analyses were carried out by means of expert panels. The Fibrafix® TX layers were satisfactory with regard to the reduction in 2,4,6-trichloroanisole (the lead substance of cork flavour; reduction > 90%) and geosmin (the lead substance of mould flavour; reduction > 75%), but not with regard to the reduction in 4-ethylphenol, 4-ethylguaicol, and 4-ethylcatechol. However, the reduction in these off-flavours was generally not specific enough to prevent a loss of volatile compounds, especially various ester compounds and free monoterpenes. The wines obtained after filtration (in case of contamination with geosmin or TCA) were sensory faultless, but for some of the tasters, the overall quality of these wines did not correspond to the quality wine clasification.

Abstract. Traditional cultivar Grüner Veltliner is the most appreciated vine in Austrian viticulture. Due to organic growing the demand for mildew resistance within the same wine profile has increased. Cross breeding can provide such new genotypes which combine traits from different sources by parenthood. Linkage of traits with chromosomes or markers allows to predict some aspects of the phenotype. Equipped with chromosomal assisted selection the development of new varieties could be much easier and faster. On the base of two segregating populations derived from crosses of Grüner Veltliner with Malverina and Seyval blanc we could define correlation of chromosomes with some traits. Mainly ampelographic descriptors and resistance against mildew could be aligned. As a quality parameter of the wine Rotundone analyses were performed and could be attributed to chromosome 5 and 9. Selection supported by the composition of the parental chromosomes enables breeding with some arguments of design. The limits for free choice were the availability of sufficient different genotypes with a broad spectrum of chromosomal combinations. Recently released descendent cultivar Donauveltliner was selected due to the high rate of Traminer alleles.

Abstract. The most important mould associated substances like geosmine, 2-methylisoborneol, 1-octen-3-ol in wines of different grape varieties from Austria and also from other foreign countries were analysed by a HS-SPME GC-MS method. These substances were also determined in healthy and rotten grapes. All together, 391 wine-samples and 69 grape samples were examined. The study of rotten and healthy grapes found out a level of geosmin up to 20 ng/L, 1-octene-3-ol concentration up to 700 µg/L and 2-heptanol level up to 9 µg/L. The geosmin concentration of the 391 analyzed wines extended from 1-44 ng/L. The detected level of 1-octene-3-ol ranged from 1 µg/L to 23 µg/L. The determined concentration of 2-heptanol ranged from 1 µg/L up to 38 µg/L. The test with the filter layer Fibrafix TX-R was performed with nine layersá 20 × 20 cm (3.6 m 2 ) and a quantity of 625 liters wine. The filtering achieved a significant reduction of the start concentration of 60 ng/L geosmin down to only 6 ng/L (average value of 600l).

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