Effects of Thermal Pre-Treatments and Drying Processes on the Retention of Phytonutrients, Vitamins, and Antioxidant Activity in Dried Okra (Abelmoschus esculentus L.)

TL;DR

This study finds that steam-blanched freeze-drying best preserves the nutrients and antioxidants in dried okra.

Contribution

The novel contribution is identifying the most effective drying and pre-treatment method for preserving okra's nutritional quality.

Findings

Steam-blanched freeze-drying preserved the highest levels of phytonutrients and antioxidants.

Hot water-blanching and hot air-drying were least effective for nutrient retention.

Significant differences in β-carotene and antioxidant activity were observed across treatments.

Abstract

Opportunities to capture anticipated niche markets for diverse populations continue to rise. Okra (Abelmoschus esculentus L.), considered a high-value crop, is rich in nutritional and medicinal properties; however, fresh okra is highly perishable. This study examined the effects of thermal pre-treatments and drying processes in combination on the nutritional quality of dried okra. The experiment consisted of two thermal treatments (steam-blanched and hot water-blanched, and the control) and three drying treatments (freeze-dried, hot air-dried, and infrared-dried). Okra was grown in black plastic mulch, harvested twice per week, and processed three times throughout the growing season. The study analyzed moisture content, water activity, phytonutrients, ascorbic acid, β-carotene, and antioxidant activities. No significant differences were observed in moisture content and water activity among the treatments. Significant differences were observed among treatments and harvest time for total phenolic and flavonoid contents and antioxidant activity. Notable differences in β-carotene content were observed across all treatments. Based on the findings, the steam-blanched freeze-dried treatment was the most effective preservation technique for maintaining the nutritional and functional quality of dried okra. Hot water-blanching, hot air-drying, and infrared-drying were the least effective for the development of a high-value, nutrient-dense dried okra value-added product.