Studies On The Preparation Of Multi-modified Acetate Starch And It's Application To Extend Food Shelf-life

The purpose of the paper is to improve the application of starch in food film protection, and expand the application of starch. Two kinds of multi-modified starch (acid-hydrolysis esterifying multi-modified starch, enzymatic hydrolysis esterifying multi-modified starch) and their films were prepared. Besides, the performance of the films and their application in food coating preservation were researched.Firstly, amylose and amylopectin of cassava starch had been successively extracted and purified by dissolving cassava starch with thin alkaline solution, precipitating amylose with 1- butnol and amylopectin with saline. Their purities had been confirmed by UV-Vis scans of their complex formed with iodine, Gel Permeation Chromatograpy (GPC) and High Performance Liquid Chromatography (HPLC). With Scan-electron Microscope (SEM), it was showed that the configuration of amylose was dispersed, so the amylose was more available to make the film that was smoother and more intensive.The technics of preparing multi-modified starch were investigated systemically by determining the transparence of starch paste, the content of amylose and the tensile strength of starch film respectively. The optimum technological conditions were obtained. The ethylene ester of acetic acid was chose as esterifying material. The cassava starch was hydrolyzed with the hydrochloric acid of 0.15mol/L at 45℃for 2h. On the other hand, the amount of the enzyme was 0.03mL/g, and the pH of the system was 4.5. The cassava starch was hydrolyzed at 55℃for 6h, and the gelatinization time was 15min.The operating parameters of preparing starch film were studied by investigating the transparence of film, the tensile strength, elongation, and wetting infiltrating level respectively. The results indicated that the optimum parameters of forming film as follows: cold gelatinization and 0.045g/mL acid-hydrolysis esterifying starch were chose to prepare acid-hydrolysis esterifying starch film; The content of enzymatic-hydrolysis esterifying starch was 0.035g/mL, and the concentration of glycerol was 0.2mL/g. Multi-modification of starch improved many properties of starch film, and the enzymatic hydrolysis esterifying multi-modified starch film was the better, especially.Finally, the application of starch coatings in food preservation was concerned. Coating with multi-modified starch on the surface of cherry tomatoes showed obviously fresh-keeping effect. The existence of starch film reduced the fruit rot ratio from 80% (with control fruits) to 25% after 20 days, reducing the change of water, vitamin c (VC), solubility solid content and total acid. The freshening period of fish treated with multi-modified starch film was longer than the control. The freshness of treated fish was 1nd level after 60 days, while the control fish was about 30 days.