Production of ascorbic acid enriched vegetables: Absorption of an L-ascorbic acid solution and the effect of storage temperature on the foliar exogenous ascorbic acid content

An economic assessment was made of whether leaf vegetables can absorb almost all of a given amount of an L-ascorbic acid solution applied by soaking the roots for 12 h. The effects of storage temperature on the foliar exogenous ascorbic acid content were also observed. It was found that the given amounts of L-ascorbic acid solution are entirely absorbed by lettuce plants (Lactuca sativa L., cv. Redfire) and are over 90% absorbed by spinach (Spinacia oleracea L., cv. Read) and bunching onion plants (Allium fistulosum L., cv. Hakata Kuronegi). Due to the soaking treatment, the sum of the L-ascorbic acid (AA) and dehydro-ascorbic acid (DHA) contents (mg per 100 g fresh weight) in the leaves of plants which showed no signs of wilting increased from 38.9 to 201-221 in lettuce, from 76.5 to 196-225 in spinach and from 46.7 to 134-144 in bunching onion. The foliar AA content in all the plants stayed at approximately the same value during a storage period of 7 d at 4 degrees C, but decreased significantly at 25 degrees C. The foliar DHA content in all of the plants stayed at approximately the same value during storage at both 4 and 25 degrees C. These results suggest that the ascorbic acid introduced into leaf vegetables can be used effectively by consumers when the vegetables are stored at low temperature.