Effects of Cultivars and Cultivation Conditions on the Preservation of Leaf Color after Boiling in Spinach (Spinacia oleracea L.)

Abstract

Boiled green spinach leaves become bleached when exposed to light. To increase knowledge about such color change by photobleaching, the appearance and chemical components of 48 spinach cultivars were examined under different cultivation conditions. Although marked varietal differences in the growth rates and Brix and ascorbic acid contents were observed among the cultivars used, these factors were not related to the depth of leaf color. The chlorophyll content was significantly correlated with the depth of leaf color under some cultivation conditions. Varietal differences in the sensory evaluation of leaf color were stable under some cultivation conditions. The leaf color was deeper and more desirable following wintersweet treatment, although the chlorophyll content did not change. Such a deeper color of wintersweet-treated spinach could be due to its thicker leaves, which increased the chlorophyll content per unit area. The color of boiled leaves exposed to light was significantly correlated with that of raw leaves. The cultivars with higher h and lower C* and L* values were evaluated as having a desirable deep green color when both raw and boiled. The cultivars with a deep color when raw retained their color after boiling and photobleaching. Therefore, the color of raw spinach leaves is the most important factor in determining color after boiling and photobleaching. Brix and ascorbic acid contents increased following wintersweet treatment. This treatment is important to obtain spinach with desirable color and chemical components.