engleski

Influence of the addition of tannins of different origin on protein stability and aromatic profile of Malvazija istarska wine

Malvazija istarska is an autochthonous and the most important wine grape variety in Istria (Croatia), and is cultivated on more then 60% of total vineyards in the region. Due to specific composition of must with high levels of protein and pectin substances, the addition of considerable amounts of bentonite (normally cca 150 g/hL, and in particular years over 200 g/hL) is often required to achieve protein stability. Besides desired stability, high dosages of bentonite often have negative influence on the quality of a final product, especially on aromatic profile and wine body. The aim of this investigation was to verify an innovative vinification procedure by determining if it is possible to achieve partial protein stability during winemaking with the addition of different tannin preparations, in order to reduce final bentonite amounts required for stabilization of produced Malvazija istarska wine. Four tannins of different origin were applied directly on the grapes of Malvazija istarska to maximally preserve aromatic potential due to tannin antioxidant activity. After completion of the controlled alcoholic fermentation, wines were left on fine lees for three months (batonage once a week). Evaluation of bentonite doses required for achieving protein stability was performed by three methods: proteotest, bentotest, and heating with tannin. Produced wines were then subjected to the analysis of standard physico-chemical parameters (OIV methods), and concentrations of fermentation aroma compounds (GC-MS analysis). Sensory evaluation of wines was performed using the 100-point OIV method. Evident differences in investigated parameters were determined between wines produced by the addition of different tannins and control wine obtained from untreated Malvazija istarska grapes.

Malvazija istarska; tannins; bentonite; protein stability; fermentation aroma

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