臺灣葡萄果汁加工問題之探討（二）：果汁澄清方法之研究

Investigation on the Preparation and Clarification of Grape Fruit Juice 2. Studies on the Juice Clarification Method

本試驗以康歌葡萄為主要材料，配合黑后及巨峰等葡萄，分別製成果汁，參考一般果汁之澄清方法以除去果汁沈澱物。葡萄加工過程中，碎果的加熱萃取及添加果膠分解處理，皆可顯著提高果汁中可溶性因形物的含量外，添加澄清劑則可增加果汁的澄清度，同時可消除單寧及蛋白質等對果汁外觀不良之物質。由本試驗桔果得知，添加10% bentonite, 0.01% gelatin，及調整pH值到3.0，再於-10℃下行冷安定二星期，可得到果汁中最高的沈澱量。經過濾後，就得到澄清果汁。而-10℃冷安定處理的效果，顯然要比0℃效果大。經上述處理後之葡萄澄清果汁，由理化等的分析結果發現，不但酒石酸、單寧及蛋白質含量大為減少，同時可溶性固形物及可滴定酸度亦相對地減少。以位相差顯微鏡及掃描式電子顯微鏡觀察，初步認定可能是酒石酸鹽類及蛋白質膠體等所組成。經上述處理之葡萄果汁，若在-10℃經三星期冷安定者，即使貯存於室溫下二個月，亦未再發現有任何沈澱物了。

The grape juice was made mainly of Concord and Black Queen varieties, then general clarification was studied to avoid the precipitate deposit in grape juice in this experiment. Heating and pectic enzyme treating on grape must during processing may remarkably increase the total soluble solid in juice. Addition of fining agent may increase the clearness of juice and remove tannin, protein and other materials, which are unfavorable to juice outlook. From the result of this experiment, it indicates that adding 0.1% bentonite and 0.01% gelatin, adjusting pH to 3.0, then detartrate at -10℃ for 2 weeks is the best way to precipitate in all treatments. After filtration, the clarified juice was obtained. Obviously, juice detartrated at -10℃ is better than detartrated at 0℃. From the result of analysis of clarified grape juice, there are tremendous tartaric acid, tannin and protein reduction as well as total soluble solid and titratable acidity. Through phase contrast microscope and scanning electron microscope (SEM), it can be assumed that the precipitate are mainly crystal of tartrate with protein-like colloid and so on. If the grape juice was detartrated at -10℃ for 3 weeks, nothing noticeable precipitate in clarified juice was found after being stored for 2 months.