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

Abstract

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.

Chemical Composition and Bioavailability of Zinc and Iron in Kunu-Zaki, a Nigerian Traditional Beverage

“…Our results proved that the combined processes of germination and fermentation of sorghum into kunu-zaki significantly (p<0.05) reduced the phytate/Fe and phytate/Zn molar ratios of sorghum to values (9.35 ± 0.05 and 6.45 ± 0.05, respectively) within the acceptable limit. The above observations re-enforce previous results that showed that the bioavailability of Zn and Fe in cereals and legumes are low but are generally improved by various processing techniques [7,8,23]. Meanwhile, [24] suggested that the solubility of phytate and the proportion of Zn bound in a mineral complex with phytate in the intestine depend on the levels of Ca.…”

“…3 The computed mineral ratio of the samples are shown in Table 4. The Ca/P ratio was generally lower than 0.5 which was reported to be the minimum ratio required for favourable absorption of Ca in the intestine [8]. Calcium is an important constituent of body fluids and is required along with phosphorus for bone formation.…”

“…Furthermore, a combination of the two processing techniques of germination and fermentation in kunu-zaki production, unlike in the germinated sample only, may have aided in the significantly (p<0.05) high increase in the mineral content of kunu-zaki than in germinated sorghum. Germination and fermentation are traditional methods used in the processing of cereals and legumes, which have recently been found and documented to increase their palatability and nutritional value via increased activity of endogenous enzymes which breakdown large macromolecules to smaller units such as starch to sugars, and also degrade anti-nutrients, thereby liberating chelated minerals and increasing their availability [7,8]. 14 Volume 3…”

“…Others like alkaloids and saponins are major sources of plant-based drugs, while oxalates and phytates are majorly described as anti-nutrients. The contents of these anti-nutrients in particular, and phytochemicals in general, have been reported to be significantly reduced by traditional methods of food processing such as soaking, boiling, fermentation, germination, dehydration, and cooking [7,8]. Table 3: Phytochemical composition (%) of raw sorghum, raw potato, germinated sorghum and kunu-zaki.…”

“…These deficiencies may be caused by the presence of certain anti-nutrients, especially the ability of phytate to reduce dietary Zn and Fe bioavailability by formation of insoluble mineral chelates at physiological pH. The formation and stability of these chelates depend on the relative concentrations of Zn, Fe and phytate as well as on the levels of dietary Ca present [7,8]. However, certain traditional food processing techniques, either individually or in combination, such as germination, steeping, fermentation, and boiling of grains for a limited period have been reported to cause increased activities of hydrolytic enzymes, improvement in the contents of certain essential amino acids, total sugars, B-group vitamins, and a decrease in dry matter, starch and anti-nutrients [9].…”