Preparation Of Degradable Polylactic Acid Film And Its Application In Storage Of White Mullet Fish(Opniocepnalus Argus Var Kimnra)

To develop the polylactide degradable plastics for food packaging,the effects of different food grade solvents on the film-forming properties of polylactide(PLA)particles were studied,and the surface morphology,thermal properties,light transmittance,infrared spectrum,contact angle and internal structure of the preprared polylactide film were evaluated.The main obtained results are as follows:(1)The effect of different food grade solvents on the film formation of PLA.Taking the polylactide film prepared by chloroform as a reference,the effects of food grade esters and glacial acetic acid on the film-forming properties of polylactide particles were compared.It was found that the polylactide film could be prepared by the three kinds of solvents,and the prepared film had similar transmittance and mechanical properties.Therefore,it is feasible to use food grade esters(methyl acetate,ethyl formate,butyl acetate and ethyl acetate)and edible glacial acetic acid instead of chloroform to prepare degradable PLA membrane.(2)Properties of PLA membrane prepared by food grade solvent dissolution method.Taking the polylactide membrane prepared by chloroform as reference,the performance of the membrane prepared by glacial acetic acid and methyl acetate as solvent was characterized.It was found that the thermal stability and crystallinity of the polylactide membrane prepared by different solvents were not significantly different.Considering the cost of film production,it is better to choose food grade glacial acetic acid to prepare PLA membrane.(3)The formation mechanism of PLA film prepared by food grade solvent.Polylactide was added into the solvent,and the polylactide molecules were cross-linked due to strong molecular cohesion.The polylactide membrane was obtained by rotating coating method.It was found that the surface morphology of PLA film prepared by glacial acetic acid,methyl acetate and chloroform was different,while the shape and position of the IR spectrum were almost the same.The results show that no new group or substance is formed in this process,but the surface morphology is different due to the different volatilization rate of solvent.(4)Study on the effect of polylactide film on the cold storage of white mullet fish.With PE film as the control group,the effect of polylactic acid template on the cold preservation effect of white mullet fish was studied.It was found that with the increase of storage days,the change trend of each index in PLA treatment group was significantly lower than that in PE treatment group,and the change range was the smallest when the film thickness was 20 μm.The results showed that food grade polylactic acid film could slow down the biochemical reaction speed of fish tissue and prolong the cold storage period of white mullet fish.When the thickness was 20 μm,the fresh-keeping effect was the best.(5)Study on the effect of polylactide film on the preservation of frozen white mullet fish.PE film was used as the control group,the effect of PLA film on the preservation of frozen white mullet fish was investigated.It was found that the change range of each index of PLA group was the smallest,the polylactic acid film could delay the spoilage of fish meat and was an ideal packaging material for frozen white mullet fish.In a word,edible glacial acetic acid can replace chloroform in the preparation of food grade polylactic acid film,and the polylactic acid film can delay the deterioration of white mullet fish meat and prolong the cold storage and frozen storage period of white mullet fish meat.