61A-36 |
In vitro starch digestibility of cooked sorghum flours and effect of protease pretreatment |
B. A. BUGUSU, Food Science, Purdue University, 1160 New FS Bldg, West Lafayette, IN 47907 and B. R. Hamaker. Sorghum starch has lower overall digestibility in a flour model system than other cereals, but when isolated, it shows similar digestibility as maize. This implies that the low digestibility in flour may be due to other flour components, which include protein, anti-nutritional factors, dietary fiber, resistant starch, and lipid; or complexation of starch and some of these components. Cooking has been shown to decrease protein digestibility in sorghum due to disulfide bond formation. Since starch granules are found embedded in the protein matrix, we hypothesized that the low starch digestibility in sorghum is partly due to the low protein digestibility. The objectives of this study were to determine the effect of protease pretreatment on the digestibility of cooked sorghum starch and to establish whether high cooked protein digestible cultivars have corresponding high starch digestibility. Starch digestibility was conducted on defatted cooked flours before and after protease pretreatment. Protease pretreatment was done for 1 hour using pepsin enzyme while starch digestibility was measured based on the a-amylase hydrolysis method. Normal sorghum cultivars and high protein digestibility mutants were used with maize as the control. No significant differences in starch digestibility were observed among all sorghum cultivars before pepsin pretreatment. The maize control exhibited higher starch digestibility than sorghum. There was a significant (p<0.001) increase in starch digestibility after pepsin pretreatment in high protein digestible mutants (24-31%) followed by the maize control (21%). The normal sorghum cultivars showed an increase of 7-8%. These results show that the low rate of protein digestibility plays a major role in the observed low starch digestibility, particularly in sorghum flours.
Session 61A, Carbohydrate
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