Abstract
Ume fruit was salted with calcium hydroxide (0, 0.15, 0.3, 0.45 and 0.6 % of the fruit weight), this being the most commonly used hardener. After salting for a month, the concentration of calcium hydroxide at which bitterness occurred was investigated by a sensory evaluation.
The bitterness of the salted ume was evaluated according to a 5-level numerical scale by three groups comprising salted-ume makers, researchers on food and students, and was then investigated by analyses of variance. The discrimination ability for the bitterness of salted ume was the same among these three groups, and ume fruit salted with 0.6 % calcium hydroxide was evaluated as being significantly bitter at a level of 5% in comparison with no calcium hydroxide. Using Scheffé's paired test performed with the students' group, ume fruit salted with 0-0.45 %, 0-0.6 %, 0.15-0.45 % and 0.15-0.6 % calcium hydroxide were evaluated as being significantly bitter at a level of 5 % for the higher concentration of calcium hydroxide.
The points of subjective equality for seasoning (corresponding to the perceived concentration) during mastication of all salted ume fruit samples was about 20 % of the undiluted seasoning concentration, and a high correlation (r=-0.9995) between this concentration for subjective equality and the hardness of the ume fruit samples was recognized. The most effective concentration of calcium hydroxide in ume flesh salted with 0.6% calcium hydroxide was higher than detection threshold for calcium hydroxide in the seasoning solution.
From these results, in order to prevent bitterness from occurring in salted ume fruit, it is proposed that the most desirable concentration of calcium hydroxide added during salting must be less than 0.6%.
