Light-induced glycoalkaloid accumulation of potato tubers (Solanum tuberosum L)

The total glycoalkaloid concentration of non-sprouted potato tubers, cvs Ma rfona, Fianna, Maris Piper, Kestrel and Golden Wonder, was measured followi ng 15 days of continuous illumination (250 mu mol m(-2) s(-1) photosyntheti cally active radiation) using high-performance liquid chromatography. Compa risons were made of the influence of four sources of illumination: fluoresc ent tube-type warm white, high-pressure sodium, high-pressure mercury types MB/U and MBFR/U. Irrespective of cultivar, glycoalkaloid concentrations of tubers placed in the dark remained relatively constant from day 0 to day 1 5 and did not exceed food safety values of 200 mg kg(-1) FW. A highly signi ficant cultivar, light and cultivar x light (P < 0.01) interaction was reco rded. Cultivar Kestrel was shown to be light-sensitive with high rates of g lycoalkaloid accumulation irrespective of light source, and cv Maris Piper was demonstrated to be light-insensitive. In the majority of cultivars test ed, maximal rates of glycoalkaloid accumulation were recorded following exp osure of tubers to sodium or fluorescent light, and minimal rates of accumu lation were recorded following exposure of tubers to mercury (MB/U and MBFR /U) illumination. In virtually all cases glycoalkaloid concentrations stead ily increased with time during light exposure with no indication of cessati on. In some instances the alpha-chaconine/alpha-solanine ratio decreased ov er 15 days of illumination (P < 0.05), indicating enhanced alpha-solanine s ynthesis over that of alpha-chaconine. The implications of these results in terms of consumer safety are discussed. (C) 1999 Society of Chemical Indus try.