Effect of the low temperature steam-heating process on taste components, amino acids, cyanogenic glycosides, pectic substances and texture of ume fruit removed from liquor

摘要

To make greater use of me fruit (Japanese apricot, Prunus mune Sieb. et Zucc.) removed from the liquor, it was investigated whether the low temperature steam-heating process-in which the fruit is heated by steam controlled at temperature intervals between 65 and 80 deg C, at 90 percent humidity -is a useful way to prepare the fruit into various processed foods from the constitutional and textural aspect. The analysis of ingredients in fruit samples was carried out on taste components (organic acids and free sugars), amino acids, cyanogenic glycosides and pectic substances before and after the process. Furthermore, the adhesivness of the paste prepared from the samples was measured in order to examine the effect of the heating process on textural properties of the fruit. One kg 'Nanko' variety of ume fruit contained 1941mg organic acid, 21.8g sugar consisting mainly of glucose and fructose, and 125.7mg amino acid. In the same way, one kg of 'Ohshuku' contained 1730mg organic acid, 21.8g sugar and 234.2mg amino acid. These amounts scarcely changed during the low temperature steam-heating process. Water soluble pectin increased markedly along with the ascent of the steam temperature, but hydrochloric acid soluble pectin decreased reversely. One kg 'Nanko' fruit contained 3mg amygdalin and 9mg of prunasin. 'Ohshuku' fruit contained 10mg/kg of amygdalin and 12mg/kg of prunasin. These cyanogenic compounds exhibited little change throughout the process. The adhesivness of the flesh paste prepared from the fruit heated by steam showed a trend to increase in accompaniment with the rise of the steam temperature. From these results, it was recognized that the low temperature steam-heating process altered the textural characteristics of the fruit flesh accompanying changes in the solubility of pectic substances, but did not cause resolution or dissolution of taste elements and amino acids. Consequently, it was considered that ume fruit treated by steam can be used as a useful material for various processed foods such as ume caked, seasoned ume pickles and others since the treated fruit is softer than the untreated fruit and contains significant amounts of sugar and organic acids due to material fruit.