Abstract
Improper cultivation can easily cause excessive nitrate accumulation in leafy vegetables, and the cooking processes used to prepare them can upset their nitrate/antioxidant balance, affecting their potential nitrite safety risk (PNSR). We investigated the impacts stir-frying, steaming, microwaving, and boiling on the nitrate, nitrite, and antioxidant capacity in water spinach and cabbage, and observed the impacts of storage duration on the PNSR. The antioxidant/in vivo nitrite ratio (A/N) was used to evaluate the nitrite risks in the cooked vegetables. Boiling achieved the highest A/N ratio (1.57) for water spinach, reducing the nitrate content by 25% without significantly affecting the antioxidant capacity. Stir-frying achieved the highest A/N ratio (6.55) for cabbage, increasing the antioxidant capacity by 140% without significantly affecting the nitrate content. Furthermore, it was found that the storage periods for boiled water spinach and stir-fried cabbage should not exceed 12 h and 24 h, respectively. Appropriate cooking methods and limited storage times are thus required for leafy vegetable to prevent adverse health effects.
Highlights
Leafy vegetables are an important part of the human diet due to their abundant vitamins and fibers
The potential nitrite safety risk of cooked vegetables was evaluated on the basis of the antioxidant/in vivo nitrite ratio (A/N) ratio reflecting the balance between antioxidant capacity and nitrate, which has not been reported in previous studies
The nitrate content water spinach significantly increased by 31% after stirstudy by Kmiecikfrying et al
Summary
Leafy vegetables are an important part of the human diet due to their abundant vitamins and fibers. Ascorbic acid is the main antioxidant in gastric juice, and it exerts a protective effect against gastric cancer It exhibits a strong nitrite-scavenging ability by directly reducing nitrite to nitric oxide. The potential nitrite safety risk (PNSR) in leafy vegetables depends on the balance between antioxidants and nitrate. We used two commercially available leafy vegetables (water spinach and cabbage) as samples to explore the effects of four common domestic cooking treatments (stirfrying, steaming, microwaving, and boiling) on nitrate, nitrite, and antioxidant capacity. The potential nitrite safety risk of cooked vegetables was evaluated on the basis of the A/N ratio reflecting the balance between antioxidant capacity and nitrate, which has not been reported in previous studies. We explored the actual nitrite safety risk following overnight storage of vegetables cooked by suitable methods
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