Effect of lactic acid fermentation on the physico-chemical, functional, and antioxidant properties, and in vitro protein digestibility of malted ragi (Eleusine coracana L.)

Abstract

Ragi is a widely recognized “Shree Anna” that should be included in diets to augment food diversity and security amid climate change challenges. The aim of the study was to evaluate the effect of lactic acid fermentation on the physico-chemical, functional, antinutritional, and antioxidant properties, and in vitro protein digestibility of raw and malted ragi flour at intervals of 24 and 48 h. RRF and MRF were inoculated with Lactiplantibacillus plantarum, oven-dried and milled into flour samples at each fermentation time. The process of optimizing malted ragi involves germinating soaked grains at 28 °C for 24 h, followed by open-pan roasting at 70 °C. The results showed a significant increase (p < 0.05) in carbohydrate content, water absorption index, and in vitro protein digestibility (63.66 to 79.98% and 85.77 to 90.27%) with increased fermentation time. However, the antinutrient content of phytic acid was significantly reduced with increasing fermentation time. During the 48 hour fermentation period, the crude protein content of both raw ragi flour and malted ragi flour varies from 7.01% to 7.75% and 8.18% to 8.64%, respectively. The 48 h fermented malted flour contains a significant amount of bioactive compounds, including catechin and protocatechuic acid. There was a significant increase (p < 0.05) in the total phenolic content and total flavonoid content. Thus, fermenting malted ragi flour for 48 h is an effective approach for enhancing protein digestibility and bioactive components, with a significant reduction in antinutrient content.