Low α‐Amylase Starch Digestibility of Cooked Sorghum Flours and the Effect of Protein

Abstract

The comparably low starch digestibility of cooked sorghum flours was studied with reference to normal maize. Four sorghum cultivars that represent different types of endosperm were used. Starch digestibilities of 4% cooked sorghum flour suspensions, measured as reducing sugars liberated following α‐amylase digestion, were 15–25% lower than for cooked maize flour, but there were no differences among the cooked pure starches. After the flours were predigested with pepsin to remove some proteins, the starch digestibility of cooked sorghum flours increased 7–14%, while there was only 2% increase in normal maize; however, there was no effect of pepsin treatment on starch digestibility if the flours were first cooked and then digested. After cooking with reducing agent, 100 mM sodium metabisulfite, starch digestibility of sorghum flours increased significantly while no significant effect was observed for maize. Also, starch solubility of sorghum flours at 85 and 100°C was lower than in maize, and sodium metabisulfite increased solubility much more in sorghum than in maize. Differential scanning calorimetry results of the flour residue after α‐amylase digestion did not show any peaks over a temperature range of 20–120°C, indicating that sorghum starches had all undergone gelatinization. These findings indicate that the protein in cooked sorghum flour pastes plays an important role in making a slowly digesting starch.

Effect of fermentation on the starch digestibility, resistant starch and some physicochemical properties of sorghum flour

“…Water retention and starch solubility were determined according to the method reported by Zhang and Hamaker [16]. Water was added to flour slurries and incubated at 85 8C and 100 8C for 30 min with shaking every 5 min.…”

Effect of Germination Moisture and Time on Pearl Millet Malt Quality - With Respect to Its Opaque and Lager Beer Brewing Potential

“…This is believed to be primarily due to prolamin proteins in the endosperm being cross linked by the application of wet heat 7 . This in turn appears to adversely affect sorghum starch gelatinisation 4 and hydrolysis 33 . In contrast, it does not appear that protein cross-linking happens to the same extent in pearl millet, as the protein digestibility of pearl millet is not greatly affected by wet cooking 14 .…”

Grain sorghum is a viable feedstock for ethanol production

“…Zhan et al studied the eVect of genotype and location on ethanol and lactic acid production of a limited number of sorghum genotypes [5]. Several researchers have investigated the digestibility of sorghum starch [6][7][8] and sorghum protein [7,[9][10][11] as related to its use in feed or food. Others have investigated the isolation of sorghum starch [12][13][14][15][16] and its properties [17][18][19].…”