The historical Tokaj region in northeast Hungary is a UNESCO World Heritage region since 2002 owning 5.500 ha vineyards. Produced from „noble rot” grapes, Tokaji Aszú is known as one of the oldest botrytized wines all over the world. Special microclimatic conditions (due to Bodrog and Tisza rivers, Indian summer), soil circumstances (clay, loess on volcanic bedrock) and grape-varieties (Furmint, Hárslevelű) of Tokaj-region offer favourable parameters to the formation of noble rot caused by Botrytis cinerea. The special metabolic activity of Botrytis results in noble rot grapes called “aszú” berries. The grapes undergo complex chemical modifications as the joint result of the enzymatic activity of Botrytis and the physical process of concentration.
The wine-making method of Tokaj wine specialities often gives a serious microbiological challenge to winemakers. Increasing the volatile acid content of wines is becoming more frequent, one of the technological ways to keep them lower is the use of special chitosan products, which have an inhibitory and cid effect on acetic and lactic acid bacteria.
The BactilessTM® preparation distributed by Kokoferm Ltd. and EnartisSTAB Micro by Esseco s.r.l (Divisione Enartis) are GMO and allergen-free biopolymer of Aspergillus niger, what can reduce the germ count of live acetic and lactic acid bacteria.
Phenolic compounds are responsible for the oxidation of wines, and their presence is essential for developing the character of the wine. During grape proccessing procedure, it is very important to pay particular attention to polyphenols releasing from the berry skin and seed coat because in contact with a small amount of oxygen, it can be formed with oxide compounds accompanied by masking fruitiness, hindering transformation of aroma-carrying precursors. In the case of working with noble rotted berries, an increased polyphenol content can be found endangering taste harmony, that is why every treatment with reducing polyphenols effect may be useful.
In this work, three Tokaj aszú wine types were tested with Bactiless and EnartisSTAB materials. The number of germs of lactic acid bacteria was significantly reduced by the treatments, it was no longer detectable at the higher application dose, it was also effective against acetic acid bacteria, and their amount decreased by an order of magnitude. During the treatment period, the level of volatile acid did not increase, and the amount of undesirable odor metabolites also decreased appreciably. Despite the fact, that the primary function of active chitosans is antimicrobial control, the polyphenol content has also been reduced by 5-8%.
Author: Bene Zsuzsanna1
1University of Tokaj, Lórántffy Institute, Department of Viticulture and Oenology
*corresponding author: bene.zsuzsa@unithe.hu
Keywords: acetic acid and lactic acid bacteria, chitosan, polyphenols, Tokaj
