Glycoalkaloid and Chlorophyll Changes in Eight Potato Varieties Exposed to Light

Abstract

Red and white skin potatoes (`Cal Red', `Cal White', `Durango', VC1015, `Yukon Gold', `Latona', A94381, and `Satina') were harvested from plots in commercial fields in Kern and San Joaquin Counties and at the Univ. California Research Center at Tulelake. After washing and sorting, potatoes were held in plastic trays in the dark (black plastic bags) or exposed to light (90 cm below cool-white fluorescent GE Watt-Miser 34W bulbs, ≈1300 lux) at 20 °C. After 0, 3, 6 and 9 days, potatoes were scored for appearance of greening (1 to 5 scale), evaluated for external color (L * a * b * color values), skin chlorophyll concentration, and glycoalkaloid concentrations. For the latter, freeze-dried slices of tuber were extracted and analyzed by colorimetry and HPLC for alpha-solanine and alpha-chaconine. Initial glycoalkaloid concentrations varied among cultivars, with `Cal Red' consistently having the highest concentrations. Tubers stored in the dark had no or a slight increase in glycoalkaloid concentrations. Light exposure resulted in increased glycoalkaloid concentrations in all cultivars, but to varying degrees. Some varieties had negligible changes while others increased as much as eightfold. The average increase was 300%. Generally, `Cal White' had the largest light-induced increases in glycoalkaloids.