Journal of Food Processing & Technology

Abstract

Effect of Processing on Nutritional Quality and Antioxidant Potentials of Leafy Vegetables

Saranya R, Devanesan G, Ramesh S and Gopi R

Blanching is a primary step in processing of Green Leafy Vegetables. Despite of its preserving advantage, it leads to partial destruction of some nutrients like vitamin C which is heat liable and sensitive to light, oxygen and oxidizing agents. The study was carried out to identify a suitable blanching temperature, time and chemical media for the green leafy vegetables namely, Alternanthera sessilis, Cardiospermum helicacabum and Celosia argentea that ensures enzyme inactivation and maximum nutrient retention. The leaves were processed by the following methods (i) Blanched at 80°C, 90°C and 100°C for 5 min in distilled water (ii) Blanched in water containing chemical media (potassium metabisulphite (KMS), sodium bicarbonate and sodium chloride) at 80°C for the 1 min, 2 min and 4 min respectively. Blanching time and temperature increased, there is a reduction in the retention of Vitamin C in all the greens. The statistical analysis (P≤0.05) showed significant retention of vitamin C on blanching the leaves at 80°C for 1 min in potassium metabisulphite. Reduction in the moisture content, fiber, Iron was also found to be statistically significant. Blanching at 80°C for 1 min in potassium metabisulphite was sufficient to inactivate peroxidase in leafy vegetables. The antioxidant properties of the fresh and blanched green leafy vegetables were subsequently determined. The study revealed the presence of phenolics (gallic acid equivalents 3.89-8.55 mg/g), flavonoids (quercetin equivalents 9.47-37.66 mg/g) and tannins (tannic acid equivalents 10.47-13.58 mg/g). Three of the samples were exhibited remarkable DPPH radical scavenging activities (>70%) with significant IC50 values of 653.10 and 760.34 μg/ml respectively. The result showed that blanching at 80°C for 1 min with potassium metabisulphite as a chemical media had a good retention of Vitamin C and least effect on other nutritional content. Hence it is found that blanching is the best method of preserving GLV without compromising its nutritional quality and antioxidant potentials.