Study On The Physicochemical Structure And Functional Properties Of The Starchy Feed

Our objectives were:（1） to assess the variability of basic physicochemical properties and in vitro starch digestibility of starchy feedstuffs,（2） to investigate relationship between physicochemical properties and starch digestibility and（3） to explore the effects of different sources of starchy feeds on corn starch digestibility and glucose release. For this purpose,commonly utilized starchy feeds（barely, wheat, corn, sorghum, broken rice, brown rice and cassava） were selected. The study included the following two parts:Experiment one: Physicochemical properties and starch digestibility of starchy energy feedFourier transform infrared spectroscopy and scanning electron microscopy were used to detect and compare the differences on starch structural characteristics, starch granule morphology and other physicochemical properties of the main starchy feeds. Differences on starch digestibility were evaluated by in vitro method. The principal component analysis revealed significant relationships between physicochemical properties and starch digestibility and its glucose release. The results are as follows:（1） The infrared absorbance intensities of A₈60（1.712 vs. 1.720）, A₉28（1.390 vs. 1.402）and A₁022（1.884 vs. 1.842） were greater for broken rice and brown rice starch, which were similar to each other. Sorghum starch had higher intensities of A₉95 and A₁047, 1.941and1.872; respectively. The infrared absorbance intensity of A₁022 were decreased in the order of broken rice, brown rice, cassava, barely, wheat, sorghum and corn, 1.884, 1.842, 1.706, 1.643,1.579, 1.464 and 1.358, respectively. The ratio of the infrared absorbance intensities of A₁047and A₁022, i.e. R（1047/1022）, were increased in the order of broken rice, brown rice, cassava,barely, wheat, corn and sorghum, 0.762, 0.786, 0.905, 0.969, 0.990, 1.232 and 1.280,respectively.（2） Brown rice and broken rice starch particles were sharp and protruding polyhedron, and the particle size was small. Sorghum and corn starch granule had smooth edges and corners with uniform size. Barley, wheat and tapioca starch granules are spherical and the starch granule morphology for barley was similar to wheat.（3） Focussing on the first 90 min of incubation, the cumulative in vitro starch of all feeds showed a rapid upward trend and release glucose faster, which pretend more slowly with a slower release of glucose after 90 min. Sorghum was digested slowly and had the lowest digestion curve at all time intervals, whereas broken rice and brown rice starch were digested faster and to a higher extent for almost the entire incubation period. In our study, broken rice and brown rice were high- pGI feed; barely, wheat and cassava were medium- pGI feed, while cornand sorghum were low- pGI feed.（4） The relationship between starch basic physicochemical properties and its glucose release showed that pGI was positively related to intensity of A₁022（R2=0.74; P<0.01） and negatively related to the infrared absorbance intensities of A₉95, A₁047 and R（1047/1022）（R2=0.91, R2=0.86 and R2=0.89, respectively; P < 0.01）. The smaller starch granules are, the higher will its pGI has. Meanwhile, pGI was also positive relationship with glucose,amylopectin and RDS content（R2=0.64, R2=0.83 and R2=0.85, respectively; P < 0.01） and negative relationship with amylose, prolamin and RS content（R2=0.82, R2=0.68 and R2=0.83,respectively; P<0.01）.Experiment two: The effect of starchy energy feed in different proportions combined with corn on starch digestibility and the release of glucoseOn the basis of Experiment One, without the addition of any enzyme preparations, to detect the effect of barley, wheat, sorghum, broken rice, brown rice and cassava combined with corn with different proportions（1: 3, 1: 3,1: 4, 3: 7,3: 7,1: 4, respectively） on starch digestibility and the release of glucose by the in vitro method. The results are as follows:There are interacted effect of different sources of starch combined with corn on the digestibility of starch and the release of glucose. When barley, wheat, broken rice, brown rice and cassava combined with corn in dirrerent proportions（1: 3, 1: 3, 3: 7, 3: 7, 1: 4, respectively）showed a positive interaction effect on the starch digestibility and glucose release. On the contrast, sorghum in proportion of 1:4 combined with corn showed a negative effect on the starch digestibility and glucose release.To sum up, different sources of starch had differences on basic physicochemical properties,which will influent the digestibility of starch and the release of glucose. There are interacted effect of different sources of starch combined with corn on the digestibility of starch and the release of glucose.