Experimentation
The study aimed at collecting technical and scientific information in order to identify the most suitable bentonite among four types of bentonites, not commonly used in wine clarification – bentonites A and B (granular formulations) and bentonites C and D (powder formulations) – by studying the interaction between each bentonite and a common matrix, a young Valpolicella wine. Clays were used, after rehydration in a volume of water equal to twenty times their weight, as summarized in figure 1. Experimental tests were preceded by a preliminary evaluation, in order to determine the optimal amount of bentonite to be used by choosing it among the following levels: 15, 30 and 50 g/hL. The preliminary assessment has therefore provided the measurement of colloidal stability and phenolic compounds of the samples treated with bentonites at the indicated amounts. Once established the amount to be used in the experimental tests, the effects of bentonite have been measured again in terms of color index (color intensity and tonality), phenolic compounds (total polyphenols, anthocyanins and tannins), stability of the colloidal system (by tests at 30-40-50-60-70-80°C) and total protein concentration.
Results
The preliminary evaluation showed that the optimal amount to be used in testing was 50 g/hL. On the base of a rapid colloidal stability test results, at the amount level of 50 g/hL, the highest clarification occurs for all samples especially with powder bentonites. As for the removal of total phenols, the impact of bentonite does not appear to be quantitatively related to the amount. Thus, a 50 g/hL level enabled to reach the main objective, i.e. the stability of the colloidal system, without significantly affecting the content of total phenols. Experimental tests have shown that the treatment with bentonite results in a reduction in color intensity, even if the different types of bentonite have not been resulted in significant differences; on the contrary, as for tonality, the treatment has not caused any variation (table 1). Table 2 shows the results for the total polyphenols content: the bentonite treatment has not resulted in significant variations and bentonites, although different, have equivalent behaviors. As for the content of anthocyanins (table 3) and tannins (table 4), only bentonite D (powder) distinguished among the others, determining a significant removal of such compounds. On the contrary, the samples treated with the bentonites A, B, and C showed similar values which were overlapped to those of the untreated sample. To assess the stability of the colloidal system, different amounts of the same sample have been heated at 30, 40, 50, 60, 70 and 80°C. In figure 2, a comparison among the turbidity trend of the samples treated with bentonite and the turbidity of the untreated sample. At all temperatures, bentonite A ensures the maintenance of clarification, while D was the less efficient one. To assess the de-proteinization by clays, the percentage reduction has been calculated in comparison to the protein content of the control sample after the static sedimentation.
图3显示了所使用的每个Bentonite的减少百分比数据。膨润土的处理尚未导致蛋白质浓度的显着降低，该蛋白质浓度达到最大值A（9.5％）。总之，实验研究表明，与胶体系统的有效稳定相关的膨润土处理和蛋白质去除，在任何情况下均可，实验研究表明膨润土治疗的正初级效应。这种初步效应与二次效果相结合，导致四个膨润土与酚类基质的轻微相互作用，就花青素，单宁，总多酚和颜色指数而言。膨润土A和Bentonite D的不同行为都认为胶体系统的稳定性和胶体和蛋白质稳定性的其他基质因子。因此，在评估最佳量和型化稳定性和保持酒色和纹理之后，红葡萄酒似乎可以通过通过膨润土致澄清通过膨润土来改善其胶体型材。
参考
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By Roberta Dordoni，罗伯塔·加拉西，Milena Lambri - 酿酒学院和农业学院，农业学院，大学，大学，帕康琴
