Effect of Calcium-Compound Addition on the Physical Properties and Tissue Structure of Seasoned 'Umeboshi': Investigation of Actual Conditions of Commercially Prepared Products and Verification of Products Prepared in a Laboratory.

Abstract

Physical properties which influence the quality of seasoned umeboshi were examined and microscopic observations and sensory evaluations were undertaken on 13 commercially prepared products and 4 laboratory-prepared samples pickled with calcium hydroxide. The physical properties of alcohol insoluble solid (AIS) content, pectin composition, calcium content bound to AIS and adhesiveness varied in the commercially prepared samples, and the differences were believed to be due to the condition of the materials and methods used. A high correlation was observed between adhesiveness-AIS and adhesiveness-water soluble pectin. Among the commercially prepared products, some were assumed to have had calcium compounds added during the process because of the high values of calcium in AIS, and microscopic observations revealed that cell walls had been strengthened by calcium just beneath the skin of these products. Laboratory-prepared samples pickled with 0, 0.05, 0.10 and 0.15% calcium hydroxide showed that the addition of calcium had the effect of reducing damage to the skin and flesh of umeboshi during the rest of the process, and there were no differences in the physical properties except for the calcium content bound to AIS even with differences in the calcium concentrations. The areas just beneath the skin which were affected by the added calcium deepened progressively depending on the calcium concentration, and the sample pickled with a concentration of 0.1% had a skin strong enough to prevent damage and yet thin enough to be sensory-evaluated appropriately.