Fermentation and sauteing enhances the physicochemical properties, carotenoids and the antioxidant activity of some food vegetables

Vegetables are important sources of protective foods for maintenance of health and prevention of diseases. However, the nutrients and bioactive potentials of some processed ethnic vegetables have not been fully exploited. The present work evaluates the proximate content, minerals, vitamins, functional, carotenoids, antioxidant activity and retention percentage of nutrient in raw and processed fluted pumpkin (FPL) and garden egg (GEL) leaves consumed in Nigeria. The results showed that moisture (13.67 %), ash (20.10 %) and Fe (18.82 mg/100 g) were significantly (p < 0.05) higher in GEL, while fat (16.31 %), protein (8.92 %), fibre (16.02 %) and Zn (9.76 mg/100 g) were significantly (p < 0.05) higher in FPL. Shade-dried FPL and GEL showed abundance of protein, Fe and Zn content, whereas ash and Mg were abundant in fermented vegetables, and fat and fibre were abundant in sauteed vegetables. Fermentation revealed the highest vitamins C and B₉ content whereas sauteing obtained greater vitamins A and E content. Total flavonoids, total phenolic, DPPH and FRAP content were increased as a result of fermentation and sauteing in both vegetables. Results revealed that total carotene, 9-cis-β-carotene and 13-cis-β-carotene were increased by fermentation, whereas trans-β-carotene and α-carotene showed losses due to fermentation and sauteing. Furthermore, fermentation retained greater percentage of total carotenoids, vitamin C and total flavonoids, whereas sauteing retained greater percentage of Fe, Zn and total phenolic in both vegetables. Overall, fermentation and sauteing highlights the use of these vegetables to improve nutrition, sustain health and evaluates the effect of processing methods on nutrient quality.