Effect of particle size on kinetics of starch digestion in milled barley and sorghum grains by porcine alpha-amylase

The influence of milled grain particle size on the kinetics of enzymatic starch digestion was examined. Two types of cereals (barley and sorghum) were ground, and the resulting grounds separated by size using sieving, with sizes ranging from similar to 0.1 to similar to 3 mm. In vitro enzymatic digestion was performed, using pancreatic alpha-amylase, amyloglucosidase and protease, to determine fractional-digestion rates over 24 h. The resulting glucose production rate data were well fitted by simple first-order kinetics. For each sieve screen size, the digestion rate of barley was always higher than that of sorghum. The rate coefficients for digestion showed a decrease with increasing size, and could be well fitted by an inverse square relationship. This is consistent with the supposition that starch digestion in these systems is controlled by diffusion of enzyme through the grain fragment. Apparent diffusion coefficients of alpha-amylase obtained by fitting the size dependence were 0.76 (sorghum) and 1.7 (barley) x 10(-7) cm(2) s(-1), 9 (sorghum) and 4 (barley) times slower than predicted for a molecule of the size of alpha-amylase in water. (C) 2009 Elsevier Ltd. All rights reserved

Effect of extrusion temperature and pre-extrusion particle size on starch digestion kinetics in barley and sorghum grain extrudates

Barley and sorghum milled grains were separated into three size fractions (fine, 1.0. mm) and extruded at two temperature levels (maximum of 100 °C or 140 °C), to determine the effect of pre-extrusion fraction size on starch digestibility. Following extrusion, in vitro enzymatic starch digestibility was markedly enhanced with a first order rate, typically ten times greater than before extrusion, but following the same trend i.e. faster digestion for finer pre-extrusion grain sizes. For sorghum, the projected maximum digestibility was also reduced with pre-extrusion grain size. There were only minor differences in digestibility following extrusion at 100 °C compared with 140 °C. Grains were not pre-conditioned, so moisture uptake during extrusion may have been limited, resulting in extrudates containing residual ungelatinized starch granules. It is proposed that the main effect of extrusion processing was to open up the grain endosperm structure, thereby reducing the diffusion path lengths for amylase to digest starch. The results indicate that an efficient use of extrusion processing could be to target separated larger particles from milled grains for re-combination with finer ground grains for improved energy utilization in monogastric feeds

Effects of Sucrose-based High-lysine Diet on Blood Chemistry, Growth Performance, and Gastrointestinal Morphology of Broiler Chickens During the Growing Stage

This study aimed to investigate the effect of replacing fat in broiler grower diet with sucrose combined with supplementation of the synthetic amino acid lysine on growth performance, gastrointestinal morphology, and blood biochemical parameters in broiler chickens. Broilers were raised for 21 days and then divided into two treatment groups (n=24 in each group). Two dietary treatments were used: corn-soy–based diet with oil (control) and corn-soy–based diet formulated with sucrose (3.30%) and lysine hydrochloride (3.36%). The experimental period was 21 days (from 21 to 42 days of age). At the end of week 6, all the birds in each treatment were slaughtered via neck slit, defeathered, and eviscerated for carcass and intestinal morphological characterization. Blood samples were collected to measure blood lipoprotein, triglyceride, and cholesterol levels. The results showed that supplementation of sucrose and lysine hydrochloride to broiler ration significantly (P<0.05) decreased feed intake by half and reduced average daily gain during the study period compared to those observed in broilers fed control diet. Further, this supplementation significantly altered gastrointestinal morphology and blood lipoprotein (HDL and LDL) and total cholesterol levels. In conclusion, corn-soy–based diet fortified with sucrose (3.30%) and lysine hydrochloride (3.36%) within current nutrient specifications has a negative effect on broiler growth performance