Selected Anti-nutritional Factors and In-vitro Protein Digestibility of Some Sorghum Types as Influenced by Germination Time During Malting

Abstract

The effect of germination time, during malting, on phytate and tannin concentration as well as on the in-vitro protein digestibility of some sorghum types was investigated. The increase in the germination time led to a decrease in the phytate content from the initial range of 1004.6-1097.4 mg/100g, at zero-hour germination, to a range of 457.2-626.3 mg/100g at 48-hour germination time. A further decrease in the phytate content was obtained at 96-hour germination time with a range of 215.4 -298.3 mg/100g. A maximum of 71.5-79.2% phytate reduction capacity at 96-hour germination time was attainable with the sorghum types. The increase in germination time also caused the tannin concentration to decrease. The initial tannin concentration (0.23-4.47 mg/g), at zero-hour germination time, decreased to 0.15-3.35 mg/g at 48-hour germination time while a range of 0.13-3.07 mg/g was obtained at 96-hour germination time. A maximum of 25.9-45.8% tannin reduction capacity at 96-hour germination time was attainable with the sorghum types. The in-vitro protein digestibility of the sorghum types increased from the initial level (32.1-45.1%), at zero-hour germination time, to 42.8-61.3% at 48-hour germination time while that of 96-hour germination time was 46.7-64.8%. It may be concluded that the decrease in the anti-nutritional factors and improvement in the protein digestibility of sorghum types during the malting process was essentially a function of germination time and sorghum grain variability.