Flexible Plla Film And Its Application In Modified Atmosphere Preservation Of Cherry Tomato

After harvest,cherry tomato has strong respiratory metabolism,but it is prone to water loss and wilting,so it will lose its edible and sales value.In order to maintain its quality and prolong its shelf life,we prepare PBI copolymer and PLBI copolymer by one-step melt polycondensation,then prepare modified atmosphere films by blending PBI and PLBI with PLLA respectively in different proportions,and we test the mechanical properties and gas permeability of the films.The results show that compared with PLLA film,the compliance of PLLA/PBI and PLLA/PLBI films are greatly improved.The maximum elongation at break of the PLLA/PBI film reaches 371.8%,which is 66 times that of PLLA,but the gas permeability of the film is significantly reduced.Compared with PLLA film,the O₂ and CO₂permeability of PLLA/PBI5 films are reduced by 6.4 times and 6.2 times respectively.Compared with PLLA film,the CO₂ and O₂ permeability of PLLA/PLBI films decreased slightly,but the CO₂ and O₂ selective permeances of films are increased.Of which,the CDP/OP of PLLA/40PLBI films increased to 3.8;At the same time,the water vapor transmittance of PLLA/PIBI film is 1.4 times that of PLLA.Finally,we prepare PLLA/PIBI films in the form of modified atmosphere window,and we apply two thicknesses（15μm and 30μm）to the controlled atmosphere storage test of cherry tomato.By measuring the gas components in the fresh-keeping packaging box during storage,the quality indexes and physical and chemical indexes of cherry tomato to evaluate the storage effect of PLLA/PIBI film with different thickness on cherry tomato.The results of cherry tomato fresh-keeping test shows that 15μm packaging group was better than 30μm packaging group on preservation effect;PLLA/20PIBI-15,PLLA/20PIBI-30,PLLA/40PIBI-15 and PLLA/40PIBI-30 maintain good sensory quality during storage;On the 28th day of storage,the sensory score of PLLA/40PIBI-15 packaging group is still more than 6.The CO₂ concentration in the fresh-keeping box is 4.3%,and the O₂ concentration is 3.7%,which is in line with the best gas proportion of cherry tomato storage;The soluble solid content of cherry tomato fruit,the titratable acid content,the content of vitamin C,the total phenol content respectively,5%,0.38g（malic acid）/100g,is 43.09 mg/100 g,0.19 mg/g,which is significantly higher than that of other packaging groups;In addition,the content of malondialdehyde only 4.12 nmol/g,which is significantly lower than that of other packaging groups（P<0.05）.The correlation analysis showed that the O₂ concentration in the packaging group is significantly correlated with the content of soluble solids,total phenol and malondialdehyde,and significantly correlated with the content of vitamin C;while there is a very significant correlation between CO₂ concentration and titratable acid content.In conclusion,in this test,we successfully prepare PLLA/PIBI spontaneous modified atmosphere films with good mechanical properties and gas permeability and the thickness was 15μm.On the basis of reducing the cost of modified atmosphere films by half,and the fresh-keeping period on cherry tomato can be extended to 28 days.