CHLOROPHYLL AND SOLANINE IN POTATO TUBERS: FORMATION AND CONTROL

Potato tubers turn green on a cumulative exposure to light as a result of the formation of chlorophyll. Such tubers develop a bitter taste, off-flavor, and cause health hazards and, in some instances, death because of high solanine content. These components affect the quality of potatoes and potato products, especially in respect to appearance, texture, and nutritive value. Although chlorophyll and solanine develop in a peripheral zone of the tuber in addition to the cortex as a site for solanine, the biosynthetic processes are independent of each other.

Several factors influence the rate of greening and solanine formation. Greening potential is an inherent genetical characteristic. Abnormal growing and environmental conditions and improper handling lead to the differences in solanine concentrations. Immature, small, and low dry weight potatoes show more tendency of greening as compared to mature, large, and high dry weight ones. In general, intense light, high temperatures during light exposure, and low storage temperatures enhance the rate of greening. The longer the duration of light exposure, the greater is the accumulation of chlorophyll and solanine. The problem of greening could be approached by at least five routes: (1) breeding of resistant cultivars, (2) protection from light, (3) special storage conditions, (4) application of nonresidual chemicals such