Impact of ripening stages on the physicochemical and antioxidant properties of Monkey orange (Strychnos spinosa) fruit

Abstract

The Monkey orange (Strychnos spinosa) fruit is a tropical and subtropical African indigenous tree and its name is derived from the fact that monkeys eat the fruits. This study investigated the physicochemical and antioxidant properties of Monkey orange fruit (MOF) at different ripening stages (unripe – green colour, semi-ripe - light yellow colour and fully ripe – yellow colour). Physicochemical properties, bioactive compounds and antioxidant activity of MOF were determined. The results showed that the physical characteristics of MOF such as fruit weight and size, seed weight and pulp weight significantly decreased (p<0.05) with the ripening stages. However, the ripening stages did not affect the seed diameter of the MOF. A significant difference was observed in the L*, a*, b* and Chroma colour properties of MOF at different ripening stages. The Hue angle of semi and fully ripe MOF was not significantly different (p>0.05). Chemical characteristics of MOF such as moisture content, pH, total soluble solids and sugar to acid ratio significantly increased with the ripening stages. However, extractable solids and total titratable acid decreased. Total phenolic and flavonoid contents significantly decreased with the ripening stages varying from 0.844 to 0.356 mg GAE/g and 0.714 to 0.031 mg/g, respectively. Moreover, ascorbic acid content decreased ranging from 128.67 to 73.01 mg/100 g. The antioxidant activity of MOF significantly decreased (p<0.05) during the ripening stages.