Effects of Low Pressure Storage on Various Taste Components, Pectic Substances and Hardness of Ume Fruit.

Abstract

After treatment with about 200 ppm hypochlorite solution, ume fruit (Japanese apricot, Prunus mume Sieb. et Zucc.) was soaked in water, 5% NaCl or 10% NaCl with Ca lactate or ashed kelp as a hardener. The fruit was stored at a pressure of 1.2XI03 Pa. After 6 months, we analyzed the organic acids, free sugars (sugars), free amino acids (amino acids), inorganic cations and pectic substances in the ume fruit. We also measured the hardness, and the yeasts and lactic acid bacteria were examined. The following results were obtained: (1) Yeasts and lactic acid bacteria were not detected. (2) Ume fruit without a hardener obviously softened. Though ume fruit with a hardener generally maintained hardness, the fruit stored in water decreased slightly more than that stored in 5% and 10% NaCl. (3) Ume fruit with Ca lactate contained lactic acid produced by dissociation of the lactate to Ca ion and lactic acid. However, organic acids in ume fruit were not decomposed during storage. (4) Though sucrose was resolved to glucose and fructose, no sugars in ume fruit decomposed to any compound except the sugars. (5) The major amino acid in fresh ume fruit was asparagine which represented 933% of the total amino acids. The ratio of asparagine in stored ume fruit was almost the same as that in the fresh fruit. In addition, amino acids in ume fruit were considered not to decompose during storage. (6) Because the Ca content in the alcohol-insoluble substances prepared from ume fruit with Ca lactate or ashed kelp increased, Ca in both hardeners was thought to bind to some components such as pectic substances. (7) With storage, ume fruit decreased in the ratio of 0.05 N hydrochloric acid-soluble pectin (HSP) to total pectin and increased in the water soluble-pectin (WSP) ratio. Though the HSP in ume fruit with Ca lactate also decreased, the degree of decrease was less than that of the fruit without a hardener. In addition, the WSP ratio did not increase. Furthermore, ume fruit with ashed kelp was remarkably larger in HSP ratio than the fruit with Ca lactate, and the WSP was less than that in the fresh fruit. From these results, it was found that under low pressure storage, though sucrose was resolved to glucose and fructose, the taste components in ume fruit were maintained. Furthermore, it was found that ashed kelp has an ability about equal to that of Ca lactate to maintain the hardness of unre fruit during storage. However, it was considered that the mechanism for maintaining hardness might differ each case.