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Changes in phytochemicals, anti-nutrients and antioxidant activity in leafy vegetables by microwave boiling with normal and 5% NaCl solution

Singh, Shrawan, Swain, S., Singh, D.R., Salim, K.M., Nayak, Dipak, Roy, S. Dam
Food chemistry 2015 v.176 pp. 244-253
anthocyanins, antinutritional factors, antioxidant activity, ascorbic acid, boiling, carotenoids, cooking, food security, green leafy vegetables, nitrates, oxalates, phytic acid, phytopharmaceuticals, polyphenols, saponins, sodium chloride
The present study investigated the changes in phytochemicals and antioxidant activities in 25 leafy vegetables with two common boiling practices viz., with 5% NaCl solution (BSW) and normal water (BNW) in a domestic microwave oven. Fresh samples (100g) were rich in polyphenols (58.8–296.9mg), tannin (402.0–519.4mg), flavonoids (148.9–614.4mg), carotenoids (69.0–786.3mg), anthocyanin (11.7–493.7mg) and ascorbic acid (245.0–314.2mg). Microwave boiling significantly (p<0.05) decreased/increased phytochemicals but none of the compounds followed same trend in all vegetables. Boiling process reduced anti-nutrients from fresh samples (FS) as observed for nitrate (4.5–73.6% by BSW and 22.5–98.8% by BNW); phytate (6.2–69.7% by BSW and 10.6–57.3% by BNW) and oxalate (14.7–88.9% by BSW and 14.5–87.3% by BNW) but saponin increased in 18 vegetables by BNW while 8 vegetables by BSW. The study revealed differential pattern of change in phytochemical matrix and anti-nutrients in vegetables by microwave boiling which will help in devising efficient cooking practices and contribute in health and nutritional security.