CHLOROPHYLL, CHLOROGENIC ACID, GLYCOALKALOID, AND PROTEASE INHIBITOR CONTENT OF FRESH AND GREEN POTATOES

Exposure of commercial White Rose potatoes to fluorescent light for 20 days induced a time-dependent greening of potato surfaces; an increas e in chlorophyll, chlorogenic acid, and glycoalkaloid content (alpha-c haconine and alpha-solanine); and no changes in the content of inhibit ors of the digestive enzymes trypsin, chymotrypsin, and carboxypeptida se A. The maximum chlorophyll level of the light-stored potatoes was 0 .5 mg/100 g of fresh potato weight. Unstored potatoes contained no chl orophyll. Storing potatoes in the dark did not result in greening or c hlorophyll formation. Chlorogenic acid and glycoalkaloid levels of dar k-stored potatoes did increase but less than in the light-stored potat oes. In the light, chlorogenic acid concentration increased from 7.1 m g/100 g of fresh potato weight to a maximum of 15.8 mg after greening. The corresponding values for alpha-chaconine are 0.66 and 2.03 mg and for alpha-solanine 0.58 and 1.71, respectively, or an approximately 3 00% increase for each glycoalkaloid. The trypsin, chymotrypsin, and ca rboxypeptidase A concentrations, respectively, of about 1000, 375, and 100 units/g of dehydrated potato powder were not changed. Experiments on delay of greening by immersion in water suggest that (a) chlorophy ll formation and glycoalkaloid synthesis are unrelated physiological p rocesses and (b) the concentration of chlorophyll is 26 times greater, of chlorogenic acid and glycoalkaloids 7-8 times greater, and of prot ease inhibitors about 2-3 times lower in the peel of the green potatoe s than in the whole tuber. The described compositional changes should help define consequences of potato greening for plant physiology, food quality, and food safety.