Effect of germination on mineral bioavailability of sorghum-based complementary foods

Abstract

Many people living in developing countries depend on diets based on cereal staples. Such diets lack diversity, which may result in micronutrient deficiencies. A complementary food made from cereals is often low in mineral content and contains ignificant quantities of mineral absorption inhibitors like phytic acid and condensed tannins. Anti-nutritional factors are plant constituents, which play an important role in humans, reducing the digestibility of nutrients and the absorption of minerals.Infant malnutrition due to nutritionally inadequate diets is one of the major concerns in Ethiopia. Children in rural Ethiopia are especially prone to micronutrient deficiencies as they eat from the family dish, which is predominantly plant-based. The main objective of this study is, therefore, to investigate the effect of germination on bioavailability of minerals of sorghum-based complementary foods. Two varieties of sorghum (Sorghum bicolor (L.) Moench) grains (varieties 76T1#23 and Meko) were collected, cleaned, soaked for 22 hours at room temperature (22±20C) and germinated for 36 and 48 hours at the soaking temperature. The germinated seeds were dried at 550C for 24 hours and the ungerminated sorghum seeds were also dried at 550C for 2 hours to facilitate milling. Both ungerminated and germinated sorghum grains weremilled into a homogeneous fine powder.Germination of sorghum grainsfor 36 and 48 hours decreased phytic acid levels (mg/100g) significantly (p<0.05) for variety 76T1#23 from 399.12 to 255.66 and 190.11, and from 464.94 to 293.18 and 203.76for variety Meko, respectively. During germination of sorghum grains for 36 and 48 hours, molar ratio of phytate: iron was decreased significantly (p<0.05) from 4.12 to 2.06 and 1.35 for variety 76T1#23, and from 5.49 to 2.35 and 1.58 for variety Meko, respectively. Similarly, germination of sorghum grains for 36 and 48 hours decreased significantly (p<0.05) phytate:zinc molar ratio of sorghum flour from 21.18 to 12.76 and 9.31 for variety 76T1#23; and from 25.72 to 15.54 and 10.64 for variety Meko, respectively. In contrast, germination of sorghum grains for 36 and 48 hours increased significantly (p<0.05) the contents of total phosphorus, non-phytate phosphorous, iron, zinc and calcium.Hence, germination appeared to be a promising food processing method to improve bioavailabilityof mineralsand to decrease phytate levels, and therefore to decrease deficiencies of minerals in infants.

Key words: Germination, anti-nutritional factors, mineralbio-availability