Effect of Sun Exposure on the Red Color of Salted Ume Fruit After Coloring.

Abstract

Ume fruit brined with 2.5 kg of brine solution mixed with calcium hydroxide (3 g Ca(OH)2/1 kg of fruit) was either non-exposed or sun-exposed and subsequently colored with new coccine (0.004-0.1%), acid red (0.0008-0.04%), red cabbage color (0.1-10%) or perilla color (0.1-10%) colorant. A comparison was made between the sun-exposed and non-exposed samples using Hunter L-, a- and b-values as optical measurements and by sensory evaluation as an organoleptic measurement. It was confirmed that the color change with each colorant had almost reached equilibrium after 7 days. It was also noticed that the dye effect of red cabbage color and perilla color was weaker than that of new coccine and acid red. The L- and a-values of the sun-exposed samples were higher than those of the non-exposed samples, although the b-values indicated no clear difference between the sun-exposed and non-exposed samples with any colorant. The sun-exposed samples were evaluated as being lighter, redder and more preferred than the non-exposed samples with all colorants by the visual-sensory test. The degree of difference in ‘redness’ was numerically evaluated, and the ‘redness’ effect ratio on the sun-exposed samples to the non-exposed samples with the same colorant concentration was 1.1 for new coccine, 1.7 for acid red, 2.1 for red cabbage color and 1.5 for perilla color. This study clarifies that even if the colorant concentration is reduced, the same level of redness for ume fruit could be obtained with sun exposure before coloring. It is proposed that sun exposure will contribute to the coloring of salted ume fruit.