Heat-induced damage in potato (Solanum tuberosum) tubers:: Membrane stability, tissue viability, and accumulation of glycoalkaloids

Effects of heat on cell membrane permeability, metabolic activity, and glycoalkaloid content were studied in stored potato tubers. Heat-induced alteration of cell membrane permeability was estimated by ion leakage and tissue viability by the (trichlorophenyl)tetrazolium chloride (TTC) reduction test. Solanidine, alpha-solanine, and alpha-chaconine contents were determined colorimetrically. Atlantic (a heat-susceptible cultivar) accumulated 74% more total glycoalkaloids (TGA) after 4 h at 35 degrees C than after 4 h at 22 degrees C. LT7 (a heat-resistant cultivar) showed a 50% reduction in TGA content after the same treatment. Ion leakage was similar for both cultivars after 90 min at 35 degrees C, but for the remainder of the incubation period (4 h), it was 15-20% greater in Atlantic than in LT7. At 35 degrees C, LT7 showed one-third the TTC reduction activity shown by Atlantic. Calcium treatment reduced ion leakage, while it resulted in higher TTC reduction activity in Atlantic than in LT7. Incubation in a solution of glycoalkaloids caused a 50% decrease in TTC reduction activity in Atlantic but did not affect LT7. Damage was aggravated at elevated temperatures, especially in Atlantic. Possible roles of calcium in protection against glycoalkaloid damage are discussed.