Effectiveness of combining starter fermentation and refractance window drying for enhancing the safety, nutritional quality and sensory acceptability of Amaranth leaf products (Amaranthus cruentus L.)

• Refractance window drying and fermentation yielded safe and stable products • Starter assisted fermentation met safety criteria regarding pH • Health promoting compounds higher in leaves with refractance window drying • Mineral bioaccessibility higher in fermented and refractance window dried leaves • Both processing methods yielded sensory acceptable products Underdeveloped processing and other value addition activities in African indigenous vegetable (AIV) value chains result in significant quantitative and qualitative losses. Fermentation and refractance window drying could improve the nutritional composition and quality, safety, and sensory acceptability of products from the leaves of Amaranthus cruentus L. Leaves harvested 9 and 12 weeks after sowing were subjected to spontaneous and starter ( Leuconostoc carnosum and Lactiplantibacillus plantarum ) fermentation. Then, both fermented and non-fermented leaves underwent refractance window drying at 80 and 90°C for 20-120 min. The changes in pH, final moisture content, microbial composition, nutritional and health-promoting compounds, and sensory quality of the products were then evaluated. Fermentation with the starters at 25°C for 72 h and subsequent drying at 90°C for 40 min yielded safe and shelf-stable products. Both fermented and non-fermented leaves dried at 90°C for 40 min met national food safety standards in terms of moisture content (2.14 - 2.70 %), total plate counts (30 - 240 CFU g −1 ), coliforms, yeasts and molds (not detected). The fermented and dried leaves had significantly higher in vitro protein digestibility, and higher iron and zinc bioaccessibility. In contrast, those that had only been dried had significantly higher ß-carotene, total polyphenols, and total flavonoids content and higher sensory acceptability, particularly from the 9-week-old dried leaves (p ≤ 0.05). Fermentation and refractance window drying are recommended as suitable technologies to improve the quality of AIV products, particularly for small and medium-scale processors. Opportunities to commercialize these products should be explored.