EFFECT OF STORAGE AND CULTIVAR ON THE DISTRIBUTION OF GLYCOALKALOIDS IN POTATO-TUBERS

Five table potato cultivars (Erna, Granola, Gusto, Ulse, Margit) from the same source were examined for their content of alpha-solanine and alpha-chaconine during a six-months storage period. For the testing and subsequent analysis the tubers were dissected into four kinds of tissues: eye-zone, peel, vascular bundle region, medulla. The total glycoalkaloid content (TGA) in the total tuber mass varied between 2.4 and 8 mg per 100 g fresh matter depending on cultivar (Fig. 1). Despite significant differences between cultivars (Table 1), all potato cultivars remained within the safe range during the entire storage period. Remarkable differences in TGA per 100 g dry matter could be noted in the tuber parts. For the eye-zones a TGA of 164 mg was found; the peel region showed 101 mg and the vascular bundle zone 8 mg. The medulla of the tubers contained only traces of TGA (0.164 mg/100 g dry matter, Fig. 2). The statistical analysis only revealed significant interactions between cultivars and tuber parts (Table 1), mainly caused by the cultivar Gusto which showed higher contents of alpha-solanine and alpha-chaconine In its vascular bundle regions (Figs 3 - 5). The ratio between amounts of alpha-solanine and alpha-chaconine was approximately 1:1.5, and after eliminating effects of cultivar, storage and tuber parts, the correlation coefficient between amounts was 0.865. This close correlation can be used for breeding. The non-significant, slightly negative effect of the six-months storage period on alkaloid content was noteworthy. It is assumed that only after long storage periods or through inappropriate storage (sprouting of tubers) a significantly higher glycoalkaloid content may be expected.