梅子苦味物質之萃取、分離與鑑定

Extraction, Fractionation and Identification of Bitter Substances in Mei Fruit (Prunus mume Sieb. et Zucc.)

梅子經催熟後質軟色黃且香氣濃郁，是製造果汁和果醬的好材料，唯一的缺點是仍含有苦味物質，影響製品品質，除了含有杏仁苷（amygdalin）外，尚無其他苦味物質存在的報告，本研究則從苦味的胺基酸和寡數胜肽存在情形加以調查。新鮮梅子經破碎、冷凍脫水，再以三氯甲烷和甲醇（CHCl3:CH3OH=2:1 v/v）萃取，所得萃取液經蒸發濃縮，再以膠體過濾法分離出胜肽，由官能品評試驗，再由膠體過濾所得之光學濃度曲線得知梅子中含有五種苦味的寡數胜肽，檢出第五種胜肽液中含有纈胺酸、白胺酸和苯丙胺酸，由定序結果證明梅子中確含有呈苦味的寡數目胜肽，可修正過去只認為主要苦味物質為杏仁苷一種的觀念。

Mei or Japanese apricot fruit contains soft, yellow flesh with good aroma after ripening. It is an excellent raw material for production of fruit juice drink, jam and jelly. However, its bitter taste affects the quality. The objective of this study is to find bitter substances besides amygdalin. The ripened mei fruit were shredded, freeze-dried, and extracted with a mixture of chloroform and methanol (CHCl3:CH3OH=2:1, v/v). The extract was then concentrated by evaporation under vacuum. The oligopeptides were separated by gel filtration method. The F threshold value for bitter taste of each oligopeptide was determined organoleptically. The results indicate that mei fruit contained five fractions with different optical density (O.D.) after being separated by Sephadex G-25 gel filtration method. The amino acid sequence of the compounds in each fraction was determined by an automatic amino acid analyzer. For example, valine, leucine and phenylalanine were presented and the oligopeptide sequence with H-Val-Leu-Phe-OH in structure was found in fraction V. The results of this experiment indicates that other bitter taste materials, bitter amino acids and oligopeptides, than amygdalin are contained in Japanese apricot fruit.