Study On The Preparation And The Characteristics Of Antimicrobial Film Of Starch Acetate

Packing material of antimicrobial activity is a new pattern activity material which is developing in recent twenty years. If the packing material of antimicrobiol activity which is made by base material of environmental friendly with antibacterialagent is used in Food Packing, it would substitute some use of preservatives in food. Because the packing material of antimicrobiol activity is could not only avoid microbe disturbing food, but also improve the safety of food and prolong its shelf life. So it has been considered as a development potential activity packing material. As people's life become better and better, the quantity demand of delicious sausages become more and more. While the sterilizing effection is not very satisfied and the additive of preservatives for sausages are always get out of line. Both of the problems are the hot spots recently and should be solved as soon as possible.In the thesis, firstly prepared the starch acetate by modifing starch with hydrophobicity acetyls. Secondly, according to characters of sausages as Water activity, pH value, and so on, built the imitating medium model of suasage. Thirdly, screened out antibacterialagents with strong ability of antibiotic. Then maked out antibiosis material of starch acetate for sausage packaging. As analyzing dissolving out rule for antibacterialagents coming out from film, and the relation with film's antibiosis capacity, conclude that the base material could control and slow release of antibacterialagent coming out from film. What's more, the aspects of thermal behavior, crystallize character, and other aspects have been researched in system, which provide theory basis for starch base film applied to sausage packaging.As natural starch molecules own lots of hydrophily hydroxies, so that the waterproofness and moisture-proof of starch material cann't satisfy application requirements for sausage packaging. What's else, natural starch's melting temperature nears to its decomposition temperature, so it also doesn't have plasticity. In the thesis, the natural starch molecules have been modified by lipophilicity acetyl groups, and composed several acetate starches with different degrees. Results of Contact Angle Test show that hydrophobicity of starch acetate with high degree is strong. When the degree of starch acetate reaches to 2.9, the largest contact angle of it would be 82.54. While the material also apparents weak hygroscopic. Which could provide judging for dissolving out rule of antibacterialagents from antibiosis film by regulating and controlling. XRD result manifests that natural starch's crystal structure has been changed to V. So hydrogen bonds of starch molecules have been weakened, and the structure's ordering tends to disorder. Thermal and mechanical properties analysis show that starch acetate is good at becoming film and plasticity. In the research, three antimicrobials including non water-soluble chitosan A, water-soluble chitosan C, and oligochitosan E have been selected out, which not only are good at antibacterial activity and thermostability, but also their antibacterial activity doesn't effect greatly by high degree of temperature. All of them have been mixed to modified starch with degree of 2.5, and maked antimicrobial film of acetate starch out. After that, compared their dissolving out regularity to their antibacterial ability. The conclusion of accelerate dissolution test by temperature of 30℃and rate of 30rpm showed that non water-soluble chitosan A basically couldn't dissolve out. While water-soluble chitosan C and oligochitosan E could dissolve out better. Both of them could dissolve out from base material nearly 40% in 24 hours, and then dissolve out slowly that dissolving rate respectively are 45% and 60% for film C and E in 144 hours. The three kinds of film's antimicrobial ability agree with their dissolving regularity. Film A is bad at antimicrobial effection, while film C and E are good at it, especially film E. So acetate starch antimicrobial film's dissolving energy is corresponding to its antimicrobial ability. If antimicrobialagents came out easier from film, the film's antimicrobial energy would be stronger. If the film was more hydrophily, the film's antimicrobialagents would dissolve out easier. But if the rate of antimicrobialagents dissolved out was too fast, the film wouldn't maintain its long-term antibacterial properties. So the rate of control and release dissolving is the key for deciding antibacterial film material's antibacterial timeliness and long-lasting.DMA and Instron Tensile Tester were used to analysis the influence factors of acetate starch antimicrobial film's thermal and mechanical properties. The results show that plasticizers'quantity influence glass transition temperature Tg of film greatly. The more quantity of plasticizers, the lower of film's Tg. When the quantity reaches to 40%, Tg nears to room temperature. Mechanical property result showes that chitosan could increase mechanical properties of starch film.From the above, the thesis modifies natural starch with acetyl and makes out acetate starch with different degree and characters of hydrophibic and hydrophobic. Then screening out several antimicrobialagents which could reach antibacterial rates of Escherichia coli and Staphylococcus aureus above 90%. Using the method of Tape Casting maked out the high antibacterial activity film of acetate starch. The mainly factors which could effect antibacterialagents' dissolution and antibiosis energy have been investigated. Via accommodating film's thickness, quantity of plasticizers, degree of modified starch, and other conditions, could gain antibacterial activity packaging film which own strong antibacterial activity at the condition of imitating sausage environment. So that could provide the conditions of processing technology and theoretical basis for antimicrobial activity material of control and release character which would apply in the food field.