毛豆貯藏期間品質變化之研究

Studies on the Quality Changes of Green Soybean during Storage

毛豆為營養價值甚高之蔬菜，本省之主要產地為高、屏兩縣，絕大部分供外銷日本之用。毛豆一般採用冷凍外銷之方式。但運至日本厚與新鮮毛豆比較，其維生素C降低甚多，品質及風味均有變劣之現象等問題尚待解決。本研究探討冷藏之技術，期以改變運銷方式能保存更佳之品質。本研究以採收後帶莢之毛豆用打孔塑膠袋包裝，於1°C、4°C及20°C貯藏，比較其品質之變化。另外亦用全株貯藏（包括根、莖、葉）之方式於1°C、4°C及20°C之溫度條件下比較其品質之變化。結果顯示毛豆若貯藏於20°C，經9天則表皮均變黃，維生素C降低約33%，重量減輕12.5%，而豆仁經煮熟後食用發現變得乾硬，缺乏甜味。若於4°C貯藏9天後莢略變黃，維生素C之減少約20%，但豆仁仍嫩，也有甜味。若於1°C 貯藏，同樣期間內維生素C僅減少9%，表皮仍可維持綠色，煮食時味道仍鮮美。全株貯藏與帶莢貯藏之結果相似，另外測定葡萄糖、果糖及蔗糖等糖分之變化，發覺貯藏期間葡萄糖及果糖有增加之趨勢，而蔗糖則趨減低，此二者之間是負相關性。又與維生素C之降低亦是負相關性。由上述可知毛豆應於1°C左右冷藏，可減少蒸散避免重量損失，也使維生素C等營養成分之維持較佳，色澤的維持也較好。

The green soybean is considered a highly nutritious vegetable, and is one of the most important crops on southern Taiwan. Almost all of the produce are exported to Japan, they are firstly frozen then prepared for export. On arrival to Japan the vitamin C content decreased drastically as compared with fresh ones, and the flavor and quality deteriorated. This is a problem remained to be solved. In this study, we tried to find out the best condition for cold storage of soybean to solve the bottle-neck problem. In first set of experiment, the pods were picked and packed in perforated PE bags, and stored at 1°C, 4°C and 20°C to compare the quality maintaining effects. In another set of tests, the whole plant including the leaves, stems and roots were used. As to the results, the green soybean when stored at 20°C for 9 days turned to yellowish color and lost 33% of L-ascorbic acid and 12.5% of fresh weight. The cooked beans remained quite tough and hard and greatly reduced the sweetness as compared with that of other treatments. When stored at 4°C for the same period the pods turned a little yellowish, lost 20% of L-ascorbic acid but still remained soft and sweet. And when stored at 1°C, the loss of L-ascorbic acid only 9%, and the greenness and fresh taste remained as the original. The results of whole plants storage were similar to that of the pods storage. The glucose and fructose contents increased and the sucrose contents decreased during storage. The increases of reducing sugar (glucose+fructose) had a good relationship with the decrease of sucrose and also that of L-ascorbic acid. Judging the results, the best temperature condition for storage of green soybean is 1°C.