The Studies On The Size Effect Of Sweet Potato Starch On The Physicochemical Properties And Starch Films

The physical and chemical characters of natural starch will change after physical orchemical treatment. The microscopic structure of starch also change to a certain degreecompared to the starch, such as the particle diameters, crystal properties, the relativemolecular mass and molecular chain behavior, which will cause the macro effect: the reactionactive strengthening, the solubility, dispersion and pasting behavior of starch changing.In this article, we get a series of size-decreasing sweet potato starch samples through thelaboratory jet milling, is SPS, MSPS-1, MSPS-2, MSPS-3, MSPS-4, MSPS-5, respectively.The median size D50is19.708μm,15.611μm,11.442μm,8.727μm,6.611μm,5.450μm,respectively. The specific surface area of the starch granule increases gradually from0.347m~2/cm~3to1.224m~2/cm~3.Through the analysis of the physical and chemical properties of micronized sweet potatostarch samples, we found that milling process can reduce the crystallinity of the sweet potatostarch particles, without a significant break of the starch crystal structure. The crystallinitychanges within5%. The surface of starch granule became rough after the mechanical force.The combining ability of starch and iodine strengthened after the micronization, while thecontent of amylose increased about1.5%. With the decreasing of the starch granule size, thetransparency of the starch paste decreased, but the freeze-thaw and the retrogradation stabilityimproved. The viscosity curve indicates that the starch pasting temperature could reducethrough micronization and the stability of hot paste increases.We prepared the starch film with the starch micronized samples, using glycerol as theplasticizer, fixed other factors, discussed the influence of granule size on the film only. Wefound the starch film prepared by the small particles, the permeable-oil coefficient decreased,the gas barrier property increased, the water absorption increased, the transparency increased,the hardness decreased, and the toughness increased.This paper studied on agglomerate structure changes during starch intermediategelatinization-retrogradation by small angle X-ray scattering. The Radius of gyration (Rg), thescattering integral invariants (Q), and scattering intensity I(0)change irregularly. The solidparticles present surface fractal (Ds), while the liquid quality present mass fractal (Dm). Theinterface layer thickness T reduced with the decrease of the sweet potato starch granular size,while the interface layer thickness T of the liquid sample increased as particles decreasing. The Radius of gyration of sweet potato starch film reduced with the granules reduced, but thechange is a little. The mss fractal increased. There is no obvious interface structure.