| Summary: | 碩士 === 國立中興大學 === 食品暨應用生物科技學系所 === 106 === The plum is one of the plums grown in Taiwan, the juiciness and bright red color of its flesh make it very suitable for making fruit wine. The brewing process for most fruit wines involves first extraction of the juice from the fruit through pressing, followed by the fermentation process. As the red plum contains large quantities of pectin, it often becomes difficult to juicing. Usually, pectolytic enzymes are added in order to increase the juice extraction ratio. But as a result of the pectolytic enzymes breakdown of the pectin, methanol is produced, causing the problem of excessive methanol being present in the juice. Therefore, the aim of this research was to use the evaporation method to concentrate the pectolytic enzyme-treated juice and investigate different methods for decreasing the methanol content while preserving the plum''s rich wine body, unique flavor, and vinosity. The results from a small sample of pectolytic enzyme-treated red plum juice (1 L) contained a methanol content up to 375 ppm, significantly higher than the untreated juice, which had no traces of methanol. Using the evaporation method, the concentration reached 90%, 80%, and 70%, with a methanol content of 142, 115, and 77 ppm respectively. The medium-size juice sample (10 L) at 85% concentration after evaporation had a methanol content of 97ppm. During the small-scale fermentation, the juice with pectolytic enzymes had a pH increase from 3.08 to 3.36, and the juice without pectolytic enzymes had a pH increase from 3.10 to 3.38. There was a decrease in the soluble solids of the fermented mash and after the completion of the sugar consumption, the total soluble solids were noticeably stabilized. Without the pectolytic enzymes, the change of the soluble solids slowed down in the fermented mash. The brewing of plum wine is mostly comprised of alcohol fermentation and malolactic fermentation. Malolactic fermentation results in a higher pH and lowered acidity. In conclusion, small-scale testing was gradually increased to production-scale in order to understand the different parameters of each stage and to set up a complete brewing system. 85% concentrated red plum wine (alcohol 5.9%, w/v) made according to production regulation contained a methanol content of 162.5 ppm, which is equivalent to 2753.7 ppm calculated with pure ethanol basis, lower than the legal maximum limit of 4000 ppm. Therefore, to Concentration with Evaporator can indeed reduce methanol content in plum wine.
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