The Effect of Extruded Orange Pulp on Enzymatic Hydrolysis of Starch and Glucose Retardation Index.

Orange pulp was extruded using a Brabender laboratory single screw extruder (20:1 L/D). The independent variables evaluated were barrel temperature (83, 100, 125, 150, and 167 °C), feed moisture content (22, 25, 30, 35, and 38/100 g), and screw speed (126, 140, 160, 180, and 194 rpm). The apparent density and apparent viscosity values of the extruded orange pulp increased during extrusion, while the oil absorption index decreased, in comparison with the values for raw orange pulp. In vitro studies showed that at the end of the incubation time, 90.68% of the starch was hydrolyzed in the control sample, while only 77.82% and 69.40% pulp of the starch experienced hydrolysis in the presence of raw fiber and extruded orange pulp, respectively. Extruded orange pulp showed a higher glucose retradation index (16.04–25.92%) after 30 min of dialysis and after 60 min (11.66% and 18.33%) than raw orange pulp (8.33%). These results indicated that glucose could be bound with compacted fiber matrices and inhibit alpha-amylase activity. These mechanisms may create a definite benefit by decreasing the rate of glucose absorption and eventually lowering the concentration of postprandial serum glucose. The potential hypoglycemic effects of extruded orange pulp suggest that orange pulp is a good and abundant dietary fiber resource that could be of great benefit in controlling glucose levels in the blood. It could also be added to high-fiber foods as a low-calorie bulk ingredient to reduce the calorie level. [ABSTRACT FROM AUTHOR]