L. Dao et M. Friedman, CHLOROPHYLL, CHLOROGENIC ACID, GLYCOALKALOID, AND PROTEASE INHIBITOR CONTENT OF FRESH AND GREEN POTATOES, Journal of agricultural and food chemistry, 42(3), 1994, pp. 633-639
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.