Effect Of Clarifying Agents On The Quality Of Wines

Three kinds of common clarifying agents (bentonite, gelatine and egg white powder) in wine production were used as test material, on the basis of optimal amount of these three clarifying agents, basic physical and chemical indicators, tannin and total phenolic content of Cabernet Sauvignon dry red wine (fresh fruit flavor) and Shiraz dry red wine (aged) were analyzed separately, in addition, the heavy metal content and the volatile aroma substances were investigated separately by atomic fluorescence spectrometry (or atomic absorption spectrometry) and gas chromatography-mass spectrometry, all for revealing the effects of three clarifying agents on the quality, heavy metal content and aroma substances of wines. The results showed that:1. The optimal amount of three clarifying agents used in Cabernet Sauvignon wine (fresh fruit flavor) was slightly higher than in Shiraz wine (aged), and after treatment, the turbidity of Cabernet Sauvignon dry red wine was significantly higher than Shiraz dry red wine. Among them, the optimal amount of bentonite was obviously higher than the other two clarifying agents, while gelatin and egg white powder have a similar optimal amount; the same kind of red wines had similar turbidity after different clarifying treatments. For Cabernet Sauvignon wine (fresh fruit flavor), the optimal, amount of bentonite, gelatin and egg white powder were 0.4 g/L,0.04 g/L and 0.03 g/L, the turbidity (NTU) of wine were 22,25 and 28 respectively. For Shiraz wine (aged), the optimal amount of bentonite, gelatin and egg white powder were 0.3 g/L,0.03 g/L and 0.02 g/L, the turbidity (NTU) of wine were respectively 12,12 and 13.2. Bentonite and gelatin have little influence on pH, dry extract content, color and tone of two dry red wines, while egg white powder might slightly lower the dry extract content of fresh type Cabernet Sauvignon wine, and had an obvious adsorption of aged Shiraz wine’s color. For fresh type Cabernet Sauvignon wine, the total phenolic content in bentonite-treated wine sample (6.88 g/L) decreased slightly when comparing to the control (7.04 g/L), while gelatin and egg white powder might higher the total phenolic content (7.07 g/L and 7.12 g/L respectively); the tannin content of wine increased after egg white powder and gelatin treatments (7.58 g/L and 7.33 g/L respectively) when comparing to the control (7.28 g/L), and bentonite-treated sample had less tannin content (7.19 g/L). For aged Shiraz wine, the samples treated by bentonite and egg white powder had similar total phenolic content, respectively 5.86 g/L and 5.84 g/L, all higher than control (5.61 g/L), while gelatin treated sample had a lower total phenolic content, only 5.54 g/L; the tannin content increased obviously after bentonite treatment (6.88 g/L), when comparing to the control (5.95 g/L), while gelatin and egg white powder had insignificant impact on tannin content (6.05 g/L and 6.01 g/L).3. Inorganic arsenic was not detected in all the wine samples, and there was no significant effect of three clarifying agents on the copper content of two wines. In addition, three clarifying agents can significantly reduce the iron content of two red wines, and after treatment, the same kind of wines had similar iron content; for the same clarifying agents, the iron content of Cabernet Sauvignon wines was much decreased than Shiraz wine. For fresh type Cabernet Sauvignon wine, different clarifying agents can all significantly increase the amount of lead content, particularly bentonite, which increase the lead content from 6.97 μg/L (control) to 8.95 μg/L, while gelatin and egg white powder had insignificant effect on lead content, respectively 7.17 μg/L and 7.36 μg/L; for aged Shiraz wine, bentonite and gelatin could significantly increase the amount of lead content from 2.78μg/L (control) to 5.29 μg/L and 4.98 μg/L respectively; and egg white powder was able to significantly reduce the amount of lead content to 2.53 μg/L.4. The main volatile esters detected in wine samples were ethyl octanoate, ethyl acetate, ethyl caproate and isoamyl acetate, their contents could be significantly reduced by all clarifying agents, which bentonite can significantly reduce the content of these four main acetates of wines. For terpenes, egg white powder had an obvious influence on fresh type Cabernet Sauvignon wines, among them, the content of linalool was decreased from 0.3379 μg/L (control) to 0.2717 μg/L, while P-citronellol was no longer detected; gelatin might significantly increase the amount of linalool and limonene of aged Shiraz wines, which from 0.1572 μg/L and 0.8670 μg/L to 0.2216 μg/L and 1.3726 μg/L respectively, but bentonite could obviously reduce the amount of linalool and limonene of aged Shiraz wines, respectively 0.1080 μg/L and 0.2982 μg/L.The test results also showed that, all the wine samples had better overall sensory evaluation after the treatment of different clarifications, but the use of clarifying agents could weaken the aroma of wines, especially the esters. Bentonite had strongest adsorption effect on aroma substances because of its biggest dosage, while gelatin and egg white powder had relatively small effect. On account of the complexity of the gelatin component, it could increase the amount of isoamyl acetate, that may bring some other flavor to wines.