Calcium, Zinc and Phytate Interrelationships in Four Lesser-Known African Seeds Processed into Food Condiments

The calcium (Ca), zinc (Zn) and phytate contents of raw, boiled, and boiled plus 72 h fermented samples of four lesser-known African seeds – Citrullus colocynthis, Cucumeropsis edulis, Ricinus communis and Prosopis africana – locally used for production of condiments in Nigeria were evaluated. Zinc bioavailability of the samples were also estimated using molar ratios per kg dry weight of [phytate]:[Zn], [Ca]:[phytate] and [phytate][Ca]:[Zn]. The levels of phytate, Zn and Ca of the raw seed samples varied from 150.01 ± 11.00 mg/100g (C. colocynthis) to 170.10 ± 10.01 mg/100g (C. edulis), 1.22 ± 0.10 mg/100g (C. colocynthis) to 4.79 ± 0.14 mg/100g (R. communis), and 28.33 ± 2.58 mg/100g (C. colocynthis) to 98.24 ± 15.19 mg/100g (R. communis) respectively. The calculated values of [phytate]:[Zn], [Ca]:[phytate] and [phytate][Ca]:[Zn] molar ratios for the raw seeds indicated that the samples have low Zn bioavailability. However, a combined processing technique of boiling and fermentation together, unlike boiling alone, significantly (p<0.05) improved these molar ratio markers, indicating high Zn bioavailability in condiments produced from these seeds. The implications of these findings with regards to management of Zn deficiency and the superabundance of these seeds are enormous.