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Weinsberg, Germany

Tschiersch C.,State Institute for Viticulture | Nikfardjam M.P.,State Institute for Viticulture | Schmidt O.,State Institute for Viticulture | Schwack W.,University of Hohenheim
European Food Research and Technology

The increasing demand for economic and efficient wine fining leads to the search for alternatives to traditionally used proteins, preferably new products with the side effect of non-allergenicity. A comparative fining trial on laboratory scale with equal quantities of vegetable proteins, partly used for the first time as fining agents for wine in Germany, was accomplished. Spectrum of wheat, rice, maize and potato proteins was expanded by enzymatic hydrolysis, additionally to evaluate influence of protein structure on fining effects. Proteins were modified by two different enzymes, proline-specific endopeptidase (PeP) and alcalase. Molecular weight distributions and degree of hydrolysis (DH) were compared to color intensity and HPLC data of phenolic marker substances primarily responsible for bitterness and astringency. With a total of 20 different varieties of fining agents, statistical evaluation was performed for a rapid exploratory analysis of taste improvement without the need for sensorial tests. Overall, influence on phenol composition and color intensity decreased with the degree of proteolysis. The effect of maize proteins and corresponding hydrolyzates was rather low, whereas maize proteins were nearly not influenced by the use of 2 different peptidases. Wheat proteins with highest proline content (about 9-10%) and molecular weight fractions of 14 and 30-45 kDa had a pronounced effect on color intensity. Rice and potato proteins with only half of proline content and molecular weight fractions mainly ranging between 10 and 32 kDa showed less effect on wine color, but preferably on phenolic marker compounds mainly responsible for bitter and astringent taste sensations. © Springer-Verlag 2010. Source

Kast W.K.,State Institute for Viticulture | Bleyer K.,State Institute for Viticulture
Journal of Plant Pathology

Erisyphe necator is one of the most destructive pathogens of grapevines and is normally controlled by seven and more fungicide treatments until veraison of grapes. Two fungicide regimes comprising either 3 or 7 sprays per season were compared in a German vineyard between 1999 and 2010. The trials always included: (i) 3 fungicide sprays, one before flowering, the second during blossoming and the third at berries diameter 2 mm [so called "Open Window Period" (OWP) sprays]; (ii) 7 sprays which included OWP sprays of (i) plus one spray before and three afterwards. The trials were carried out with a single line tunnel-sprayer in 4 replicates, each comprising 12 vines of highly susceptible varieties. Experimental rows were separated by untreated rows on both sides. Although in most years, natural initial inoculum was present, in 2008-2010, the initial inoculum was supplemented with artificial infections on the separating untreated spacer lines. Even under extreme disease pressure, 3 sprays in OWP had nearly the same and always more than 90% of the preventive effect of seven sprays. Source

Sack M.,Karlsruhe Institute of Technology | Sigler J.,State Viticulture Institute Freiburg | Schmidt O.,State Institute for Viticulture | Stukenbrock L.,State Viticulture Institute Freiburg | And 2 more authors.
Proceedings of the International Conference on Optimisation of Electrical and Electronic Equipment, OPTIM

The application of pulsed electric fields (PEF) to plant cells enables energy efficient and gentle disintegration in the course of food processing. The on-line measurement of the degree of disintegration of the tissue based on the measurement of the complex impedance enables a control of the applied energy according to specific requirements of the plant material. As the degree of disintegration governs a subsequent extraction process, the extraction result can be controlled by the energy applied during PEF-treatment. Experiments on the extraction of pigments and tannins from grape mash into the must showed a clear dependence of the complex impedance measured after treatment and the chemical analysis after the extraction process. An on-line measurement system tailored to the needs of the online impedance measurements of gape mash has been designed. The measurement system needs to operate reliably in an industrial environment next to a pulse generator. Hence, some measures against interference, like shielding of the measurement chamber or filtering of measurement signals have been implemented. The paper describes the design concept and presents a first measurement result. © 2012 IEEE. Source

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