Study On Application Of Thymol/Polylactic Acid Antibacterial Packaging On Storage Life Of Blueberry

Thymol/polylactic acid antibacterial film is a new type of packaging material.The excellent antimicrobial property was obtained with the addition of thymol.Polylactic acid is a kind of biodegradable and environmental friendly material,which has high transparency,excellent permeability,gas selection and good mechanical properties.The use of this material greatly caters to green environmental protection idea of the public.Currently,the packaging of blueberries mostly uses traditional inert materials for maintaining moisture and reducing oxygen,without the effect on inhibiting microorganism.However,the decay of blueberry fruit is a major problem in storage.In this study,thymol/polylactic acid antibacterial film was made into bags and applied to blueberry storage under 0℃（low temperature）,10℃（supermarket temperature）,and 20℃（room temperature）.The effect and the safety of thymol/polylactic acid antimicrobial packaging on storage life and physiological metabolism of blueberries was studied.Through mice’s acute toxicity experiment,this study evaluated the toxicity of these packaging materials in the hope to eliminate people’s doubt about the safety of these materials.The main research conclusions are as follows:（1）The antimicrobial packaging decreased the decay incidence of blueberries and kept good quality under different storage temperatures.Antimicrobial packaging combined with low temperature storage had the best effect on quality maintenance.The results showed that,the antimicrobial packaging could maintain higher soluble solids content,titratable acid content and fruit firmness.Under the same condition,the treatment could keep a 100%rate of good fruit after 36 days of storage,while PE packaging could only keep 18 days.Judging from sensory evaluation results,antibacterial packaging was also more acceptable as it won’t smell bad under storage.However,the antimicrobial package was inferior to the traditional PE material in inhibiting fruit weight loss.,This was probably due to the high water vapor permeability of the polylactic acid packaging material..（2）Based on the research of the blueberry physiological metabolism,antimicrobial packaging could reduce the loss of contents of anthocyanins,total phenolics and Vc,and effectively induce the increases of activities of antioxidant enzymes such as CAT,POD and SOD,which maintained its high nutritional quality and also improved the antioxidant capacity of blueberries.Compared with PE packaging,antimicrobial packaging also could reduce the damage of reactive oxygen species（ROS）to the cell membrane and delay membrane lipid peroxidation,by decreasing the generation of MDA and inhibiting the accumulation of H₂O₂.The inhibition of PPO enzyme activity also indicated that the treatment could reduce the decrease of polyphenols oxidation and delay fruit senescence.Under different storage temperatures,the effect of antimicrobial packaging on improving blueberry anti-oxidation and anti-aging ability are different.Best results were obtained under the condition of low temperature（0℃）storage.（3）In the experiment of mice’s acute toxicity,after feeding 10 g/kg Bw dose blueberries stored at the end of antimicrobial packaging to mice,animal played well,weight growth was not affected and no death occurred during the 14-day observation period.According to the classification of the"health food inspection and evaluation of technical specifications"（2003 edition）standard,acute toxicity of samples through the mouth of the acute toxicity in mice doses greater than 10 g/kg Bw,acute oral toxicity can be considered as non-toxic level.