Study On The Effect To The Quality Of Dry Red Wine By Freezing Treatment

Dry red wine was made by wine-grape Meili strain with different frozen treatments and the effect of the treatments on wine quality was studied, with the traditional brewing for check. The treatments are: frozen temperature, -10℃and -35℃; freezing time, 4 h and 6 h; the raw material status, grape fruit peel and grape fruit granule; unfreeze mode, natural and microwave .Freezing can damage the structure of plant cell and change the cell membrane transparence. So, grape was frozen before fermentation to destroying the cell structure and accelerating the immersion of chemicals in skins during the fermentation, with the purpose of improving wine quality. The alcoholic fermentation was same with the traditional way of dry red wine.Wine quality was evaluated by physical and chemical indicators and sensory analysis. The main results are as follows:1. Through the physical and chemical analysis, the content of total phenols and color density in wine by -35℃treatment are higher than -10℃, even with shorter freezing time. It indicates the freezing temperature is mainly in destroying the material. The content of total phenols and tannin and color density with 6h are lower than that with 4h. The effect of unfreeze code on cell damage is minor. Grape fruit is better compared with the skin. Comparing the freezing treatment and the traditional, the total phenols and color density are lower.2. The content of mono phenol and anthocyanin was determined by HPLC.14 mono phenols in wine were detected in the test wines with 13 in the comparisons, without caffeic acid. The content of mono phenols was higher in the test wines. The ratio of flavonoid and non-flavonoid was different, mainly related to the freezing time.The typical anthocyanin in the test wines were Pt-3-O-Glu and Cy-3-O-Glu, above 90% of the total anthocyanin in wine. The test wine has higher color density, Pt-3-O-Glu and Cy-3-O-Glu, indicating freezing can damage the grape skin and accelerate the transaction of anthocyanin from skin to must. The content of anthocyanin was different by different freezing treatments; however, the total content was increased, compared with the comparisons, indicating freezing treatment can improve the wine quality.3. The sensory analysis showed two test wines with grape frozen for 4h at -35℃and frozen for 6h at -10℃, both unfrozen naturally got better appearance quality than the comparison, indicating freezing treatment on material can improve the wine appearance quality. The flavor and taste of test wine had little difference. Grape skin frozen for 4h at -35℃and grape fruit frozen for 6h at -10℃, both unfrozen naturally had better flavor and taste than the comparison.4. Wine quality was improved to some extent made by frozen grape. The effect of frozen treatment to the berry skin was better than grape at the same conditions, but the energy consumption of frozen grape was 12.5 times of grape skin, and it would lead to higher costs of wine for the large capacity. Thus, it was the best frozen treatment condition that the grape skin freezing at -35℃for 4h, and it was beneficial to improve the quality of wine and save energy, and could be used in production.