Abd Elmoneim O. Elkhalifa

Effect of cysteine on bakery products from wheat–sorghum blends

Abstract Sorghum flour was added to wheat flour with or without cysteine for preparation of breads and biscuits having 5, 10 and 15% and 10, 20 and 30% addition of sorghum, respectively. Breads were prepared by two different methods. Results showed that 5% sorghum with 30 ppm cysteine gave acceptable bread using a straight-dough method. Using a chemical-dough development method for bread preparation, 10% sorghum, along with 60 ppm cysteine, may be added to wheat flour to give a bread of high quality. A high quality biscuit can be prepared by addition of 20% sorghum flour and cysteine (60 ppm/100 g flour) to wheat flour.

Effect of reducing agents on the in vitro protein and starch digestibilities of cooked sorghum

Abstract A low-tannin sorghum cultivar M-35-1 was used in this study. Investigation showed that the in vitro protein digestibility (IVPD) decreased considerably when sorghum flour was cooked in water, while it increased when cysteine, sodium metabisulphite, or ascorbic acid were added to the cooking medium. The increase in the IVPD was significantly higher with increasing concentrations of cysteine up to 0.25 M and it continued to increase to 0.5 M for sodium metabisulphite; with ascorbic acid it increased up to 0.1 M then decreased. The in vitro starch digestibility (IVSD) of the treated gruel initially increased in the presence of either cysteine, sodium metabisulphite or ascorbic acid. The increase was parallel to that shown by IVPD; however, at high levels of cysteine or sodium metabisulphite the IVSD was low. Removal of cysteine from the gruel by alcohol gave higher IVSD. Altered viscosity patterns for all the treatments led to increase in the gelatinization temperature, peak viscosity and breakdown. However, the setback decreased in all treatments. Cysteine and ascorbic acid gave a negative setback but when the pH was adjusted to 4.5 or 7.0 a normal setback was obtained. ©

Effect of preincubation of sorghum flour with enzymes on the digestibility of sorghum gruel

Abstract A low-tannin sorghum cultivar M-35-1 was used in this study. Sorghum was germinated for 6 days and protease and amylase activities were measured every 24 h. Results showed that the 5th day germinated sorghum had a higher protease activity and a lower amylase activity. Sorghum flour was incubated for 30 min with the extract from germinated sorghum or with 0.01, 0.05 or 0.1 mg ml −1 papain or trypsin prior to cooking in water. Results showed increase in in vitro protein digestibility (IVPD) with the 5th day germination extract. Pretreatment of sorghum flour with small amounts of papain or trypsin (0.01 mg ml −1 ) improved the IVPD without affecting the paste viscosity, whereas the germinated sorghum extract led to very low paste viscosity. ©