DISTRIBUTION OF GLYCOALKALOIDS IN POTATO PLANTS AND COMMERCIAL POTATO PRODUCTS

As part of a program to control the biosynthesis of Solanum glycoalkaloids in potatoes, we used a modified extraction-HPLC assay to measure the alpha-chaconine and alpha-solanine content of commercial and new potato varieties, different parts of the potato plant, and commercial potato products. The improved assay was accomplished by extracting, precipitating, and filtering the hot methanol extract through a 0.45-mu-m membrane before HPLC analysis. Recoveries of spiked samples ranged from 89 to 95%. The combined alpha-chaconine and alpha-solanine contents of different parts of the new NDA 1725 potato cultivar (in milligrams per 100 g of fresh weight) were as follows: tubers, 14.7; main stems, 32.0; small stems, 45.6; roots, 86; leaves, 145; and sprouts, 997. The alpha-chaconine content of several other potato cultivars ranged from 1.17 to 13.5 mg/100 g of fresh weight and the corresponding alpha-solanine content from 0.58 to 5.9 mg/100 g of fresh weight. The corresponding values for potato berries were 22.1 and 15.9 mg/100 g of fresh weight, respectively. The total glycoalkaloid content determined by titration with bromophenol blue was 12-30% greater than the sum of alpha-chaconine and alpha-solanine determined by HPLC. The extraction-HPLC method was adapted to measure the glycoalkaloids in freeze-dried french fries (0.08-0.84 mg/ 100 g of product), skins (3.1-20.3 mg/ 100 g of product), potato chips (2.4-10.9 mg/100 g of product), and potato pancake powders (4.5-6.5 mg/100 g of product). The presence of the two glycoalkaloids in commercial foods was also confirmed by thin-layer chromatography. The possible significance of these findings to food safety and plant physiology is discussed.