The Occurrence and Distribution of Free Alkaloid Solanidine in Netted Gem Potatoes

Abstract

Free alkaloid solanidine was detected in concentrations up to 200 p.p.m. or 337, of the total glycoalkaloid level in bitter Netted Gem potatoes. Dormant tubers of this variety are readily induced to a rapid glycoalkaloid synthesis by exposure to intense solar radiation and near-freezing temperatures, conditions frequently encountered during the potato harvest in northern areas. Under such conditions solanidine is rapidly produced in excess of amounts that could be bound as solanine, the formation of which would likely be limited by the availability of the glycosidic sugar components. The glycosidic binding of the initially synthesized solanidine proceeds a t a very slow rate during the subsequent tuber rest period. Distribution studies revealed that the potato peels, representing about one seventh of the whole tuber weight, contained solanine and solanidine, respectively, a t concentrations 2.5 and 6.2 times higher than the remaining tuber tissue, or approximately 30% of the total glycoalkaloid amount.The occurrence of the free alkaloid solanidine a t certain times in potato tubers of the Netted Gem variety demands a serious reconsideration of any toxicity studies which have been based on the sole use of crystalline solanine, and which have disregarded the possible existence of the free alkaloid in tuber tissues.'Manuscript

Glycoalkaloid levels in New Zealand potatoes

“…The slowest moving component corresponded to the pure solanine preparation, the second moved only slightly faster and is possibly chaconine, and the third may be the free alkaloid solanidine or another glycoalkaloid (Shih & Kuc 1974). The presence of three alkaloids in the tuber extracts supports the suggestion by Zitnak (1961) that further work on the toxicities of the glycoalkaloids and free alkaloids is required. He considers that solanidine is considerably more toxic than the glycoalkaloids and that its possible presence in tubers should be investigated.…”

Glycoalkaloid concentration of potato tubers following continuous illumination

“…This could be linked to curing delaying reducing sugar accumulation which occurs when tubers are chilled at harvest (Burton 1989). Support for this suggestion follows the detection of high concentrations of solanidine in tubers of cv Netted Gem after exposure to intense solar radiation and near zero temperatures (Zitnak, 1961). Under these conditions Zitnak (1 961) suggested solanidine is produced rapidly in excessive quantities that could be bound as solanine, the formation of which could be limited by the availability of glycosidic sugar components.…”

Relationships between volatile and non-volatile metabolites and attributes of processed potato flavour

“…Additionally it was suggested that the presence of salt, sugars or glycoalkaloids do not enhance potato flavour although their presence at high levels may decrease palatability. For example, several studies suggested high levels of glycoalkaloids are responsible for off-flavours in potato tubers (Zitnak, 1961;Sinden et al, 1976;Ross et al, 1978).…”