engleski

Effect of bentonite in fermentation on phenols, aromas, and sensory quality of Malvazija istarska (Vitis vinifera L.) wine

Excessive use of bentonite for clarification and fining may cause wine quantity losses, and have negative effects on wine quality, so the reduction of its dose is of great interest for producers. This is particularly important for Malvazija istarska (Vitis vinifera L.), the most prevalent native white grape variety in Croatia, whose wines often require very high doses of bentonite (150 - 300 g/hL) for achieving protein stability. To test if the addition of bentonite at various stages of fermentation of Malvazija istarska must may reduce the total dose required, vinification treatments were performed with the addition of 100 g/hL in must after settling, at the beginning, in the middle, and at the end of fermentation, while control was fermented without bentonite. In the produced wines, protein stability was evaluated by heating and heating/tannin tests, additional bentonite doses required were determined and applied, and protein-stable wines were obtained. Phenols and volatiles were determined by HPLC-DAD and GC-MS analyses after extraction. Wines were evaluated by quantitative descriptive sensory analysis and by the 100-point OIV method. The most effective treatments were those applied in the middle and at the end of fermentation, which reduced total bentonite amount for 19 % and 21 %, respectively. All wines fermented with bentonite contained higher amounts of the major hydroxycinnamoyltartaric acids, while control wine had higher amounts of the free forms. Significant changes in volatile aroma profiles were also determined. Sensorially, wines fermented with bentonite, especially those obtained after addition in the middle and at the end of fermentation, were characterised by higher intensities of the majority of positive attributes, as well as higher hedonic scores in relation to control.

bentonite ; fermentation ; protein stability ; phenols ; aromas ; sensory properties

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