Fermentation Changes the Nutritive Value, Polyphenol Distribution, and Antioxidant Properties of Parkia biglobosa Seeds (African Locust Beans)

This present study was carried out to investigate the effect of natural fermentation on the nutritive value (proximate composition), polyphenolic distribution, and antioxidant properties of African locust beans (Parkia biglobosai). African locust bean (ALB) seeds were boiled for 12 h, dehulled and subjected to natural solid substrate fermentation without any inoculation for 4 days. The proximate composition of the fermented and unfermented locust bean seeds was subsequently determined. Thereafter, the polyphenol distribution, reducing power, DPPH free-radical scavenging antioxidant activity, and inhibition of lipid peroxidation were determined for soluble free and bound polyphenol extracts. The results of the study revealed that fermentation caused a significant increase (P < 0.05) in the ALB protein content with 18.3% in unfermented and 36% in fermented. The fat content in unfermented was 13.2% versus 26.8% in fermented, while there was no significant changes (P > 0.05) in ash, crude fiber, or moisture content. However, there was a significant decrease (P < 0.05) in the carbohydrate content. The total phenolic content, reducing ability and free-radical scavenging ability were high in both the fermented and unfermented ALB. Fermentation caused a significant increase (P < 0.05) in the free phenolic content of the ALB and a significant decrease (P < 0.05) in the bound phenolic content of ALB. The free-phenolic fraction from both fermented and unfermented ALB had high reducing power, free radical scavenging ability, and inhibition of lipid peroxidation using cow brain tissues. Free phenolic extract from the fermented ALB had a significantly higher (P < 0.05) antioxidant activity than that of unfermented ALB. Results suggest that fermentation will increase the nutritive values, free phenolic and antioxidant activity of the African locust bean, making it a potential functional food in addition to its traditional role of dietary protein source.