Abstract:
Leafy green vegetables are highly demanded by Malaysian consumers due to their rich source of
essential nutrients needed for good health. The increase usage of nitrogen fertilizers and
livestock manure by growers to produce dark green leafy vegetables could lead to abundant
chlorophyll pigment and a higher content of nitrate. The conversion of nitrate to nitrite and
eventually to carcinogenic nitrosamines during storage could affect human health. Thus, a study
was conducted to determine the effects of organic and conventional cropping systems and
storage duration on the quality of leafy vegetables stored under refrigerated temperatures.
Lactuca sativa were obtained from organic and conventional farms. Damaged-free vegetables
were selected, cleaned, packed in perforated polyethylene bags and stored in a refrigerator at 6+_1
'C. Nitrate and nitrite contents, nitrate reductase (NR) activity, water loss, chlorophyll content,
total phenolic content (TPC), total flavonoid content (TFC), 2, 2-diphenyl-2-picrylhydrazyl
(DPPH), colour hue (h'), chromaticity (C*) and lightness (L*) were measured at 0, 3, 6 and nine
days of storage. The experiment was conducted using a randomized complete block design,
arranged in a factorial experiment, with five replications. The L. Sativa from the two cropping
systems showed 4.5 to 8% weight loss and decreased firmness by 33 to 46% during storage. Both
organic and conventional L. sativa showed a shift in colour from pale green to yellowish dull
green due to the degradation of chlorophyll content. The organic and conventional L. sativa were
78% reduced in nitrate contents and 99% increase in nitrite content as storage days increased.
The TPC and TFC both showed positive correlations with nitrate content while DPPH had the opposite. It can be suggested that L. sativa, should not be kept under refrigerated (6+_1 'C)
storage for more than 3 days. |
