Performance Of Enzyme-hydrolyzed Maize Starch With Isoamylase And Study On Their Making Film Performance

In recent years, much research is devoted to improve the properties of edible starch based films (SF). However, up to now, the SF are not produced on a large scale and used for commodity, due to their poor mechanical properties and water resistance. Therefore, it is focused on the improvement of the properties.Isoamylase is an enzyme which specifically cleaves theα-1,6-glucosidic linking forming the branching point of starch type polysaccharides.It is used in our experiment to cleave the branching point of amylopectin for preparing starch film and raising its tensile strength. We study the functional properties and making film condition of enzyme-hydrolyzed maize starch with isoamylase at first. Method of orthogonal test is used to optimize functional properties of enzyme-hydrolyzed maize starch with isoamylase. Then we research properties of starch and various plasticizers films.We use FT-IR, XRD, SEM, RVA and WVP to validate properties of enzyme-hydrolyzed maize starch for 2h,4h,6h and 8h and films, The preparation conditions were shown as following: 5% aqueous enzyme-hydrolyzed maize starch suspension. The content of enzyme is 10U per gram starch, reaction time is 2h, reaction temperature is 45℃. Properties of starch film : TS =17.14MPa,E=8.15% and aldehyde group content =0.457mmol/g, Compare to native starch TS=15.37MPa, E=4.97% and group content =0.086mmol/g, TS increases11.52% E increases 63.98%, group content increases 0.371mmol/gAccording to the preparation conditions , edible starch films were produced from corn starch and various plasticizers(glycerol, sorbitol, mannitol, xylitol and glucose and fructose. when concentration is 20%, mechanical properties of films with glycerol and fructose are best; when concentration is 30%, mechanical properties of films with sorbitol, mannitol, xylitol and glucose are best. After film specimens were conditioned at 50% relative humidity for 3 days, 30 days, 60 days, mechanical properties (tensile strength, elongation and thickness of films) were determined as a function of plasticizer concentration. It shows the tensile strength of films significantly increases with an increase in storage time, but their elongation decreases. X-ray diffraction (XRD) shows crystalline peaks do not change with an increase in storage time. After film specimens were conditioned for 3 days and 30 days, they have the same as crystalline peaks, After film specimens were conditioned for 60 days, B-type crystalline peaks were observed. By scanning electron microscope (SEM), starch granules were disrupted. crystallization in the films plasticized with solid plasticizer were observed, when film specimens were conditioned for 60 days, but crystallization in the films plasticized with glycerol was not observed.Material with various plasticizers paste increases first, but it decreases as the concentration raises and this has influence on structure and properties of films. Water vapor permeability (WVP) increased as plasticizer concentration increases. WVP raises as concentration increases. WVP of the films plasticized by glycerol, sorbitol, mannitol and xylitol was significantly larger WVP values than those plasticized by the monosaccharides. monosaccharide-plastized starch films were changed less as concentration increases.