Microenvironmental Regulation Packaging To Extend The Antioxidant Mechanism Of Shelf Life In Red Grapes

With the increasing global awareness of potential food shortages and therefore the importance of reducing food waste,it is highly desirable to develop new strategies and methods to extend the shelf life of food products.Red grapevine fruit contains a large number of vitamins,fruit acids,proteins,and minerals,among many other nutrients,and is also popular among domestic and international consumers because of its suitable sweetness.Fresh red grape berries have dark green stalks,large grains,crisp flesh,thin and juicy skin,and bright color.Because of these qualities,it is easy to transport and shelf life due to external mechanical collision,microbial infestation,and internal respiratory metabolism lead to red grapes easily moldy grain,fruit stalks,moldy peel,and softening and drying of the fruit,seriously affecting the economic value of the fruit.Therefore,there is a need to develop suitable preservation technologies to extend the shelf life of red grapes,maintain their storage quality and increase their economic value.The gas-regulated active film is a type of packaging film capable of autonomously regulating the internal atmosphere with appropriate gas permeability to maintain coordinated aerobic respiration of fruits and vegetables in the system,which has a positive impact on delaying microbial growth,maintaining the quality of fruits and vegetables,and regulating the metabolism of reactive oxygen species（ROS）within fruits and vegetables.By regulating the gas and water vapor transmission rates of the film,a suitable gas atmosphere is established in the packaging microenvironment,thus effectively avoiding the accumulation of high concentrations of harmful gases.Therefore,we propose a continuous dynamic microenvironmental regulation packaging,which is a promising approach of studying the mechanisms of fruit respiratory metabolism and extending the shelf life of food products.For materials,two biodegradable materials were selected:（1）[Poly（lactic）acid]（PLA）,and（2）[Poly（butylene succinate）]（PBS）for the preparation of Microenvironmental regulation packaging.The present paper is based on PLA and PBS as the main substrates.Chapter1 obtains PLA/PBS air-regulated films by melt blending and extrusion calendaring to provide conditions for the preparation of an effective microenvironment.Chapter 2investigates the effect of the microenvironmental regulation packaging on the storage quality of red grapes,while Chapter 3 focuses on the effect of microenvironmental regulation packaging the metabolism of reactive oxygen species（ROS）in red grapes.The main research and results of this article are as follows.（1）PLA was modified,and the selected modified material was PBS.the PLA/PBS gas-activated films were obtained by melt blending and extrusion calendaring.In the PLA/PBS system,a fixed ratio of chain extender and plasticizer was added,and then the ratio between PLA and PBS was adjusted to regulate the transmission rate of O₂,CO_2,and H₂O so that the atmospheric concentration in the system was suitable.Finally,the Microenvironmental regulation packaging suitable for fruit and vegetable preservation is obtained.The mechanical,barrier,optical,thermal,and micromorphological properties of the films were characterized.The results showed that the addition of PBS improved the permeability of the films,especially the O₂ and CO₂ transmission rates,with PLA/PBS 80/20 and PLA/PBS 70/30 having good results and good applicability.The surface and cross-section of the films were observed by scanning electron microscopy,which showed good compatibility between the components of the films and the microstructure did not change;the incorporation of PBS did not change the thermal and mechanical properties of the films much,and the chemical structure of the films did not change.（2）The prepared microenvironmental regulation packaging was applied to the preservation of red grapes,and the preservation effect of the system was dynamically monitored.Gas headspace analysis,hardness,weight loss,browning,and soluble solids content in the package were used as physicochemical evaluation indicators.The results showed that PLA/PBS 70/30 and PLA/PBS 80/20 could effectively control the gas entry and exit in the microenvironment,avoiding the accumulation of harmful gases and maintaining a suitable gas environment for the storage of red grapes in the microenvironment created by different ratios of PLA/PBS films.After 12 days of storage,the O₂ and CO₂ contents of PLA/PBS 80/20 were 9.99%and 4.27%,respectively,and PLA/PBS 70/30 were 19.45%and 4.25%,respectively.This indicates that the gas content in the microenvironment was kept in dynamic equilibrium.In addition,the grapes packed in PLA/PBS 80/20 and PLA/PBS 70/30 films remained full and brightly colored at the end of storage.Their weight loss,hardness,and soluble solids content were maintained at less fluctuating levels compared to the control group,which proves that a proper gas microenvironment can effectively inhibit the respiration of red grapes,regulate the storage quality and prolong the shelf life of the fruit.（3）For the prepared microenvironmental control packaging,the reactive oxygen metabolism of red grapes was dynamically monitored during the preservation of red grapes in the system.The rate of superoxide anion production and the content of hydrogen peroxide was used as the physicochemical evaluation indexes for the accumulation of reactive oxygen species,while the POD,CAT,APX activity,and GSH content were used as the physicochemical evaluation indexes for the removal of reactive oxygen species.The results showed that the PLA/PBS 80/20 film treatment effectively reduced the O₂^-production rate and H₂O₂ content of red grapevine fruits,which proved that the appropriate microenvironment could effectively inhibit the production of ROS.In addition,PLA/PBS 80/20 film treatment effectively increased the activity of POD,CAT,and APX,and the GSH content in the ASA-GSH cycle in red grapevine fruits,which proved that a suitable microenvironment can effectively scavenge ROS.storage atmosphere of fruits and vegetables,effectively regulating ROS metabolism within plant tissues and delaying fruit and vegetable aging.（4）Pearson’s index correlation analysis was performed on the indicators dynamically monitored in the microenvironmental system,aiming at verifying the mechanism of influence between the changes of the atmospheric concentration in the system and the storage quality as well as the metabolism of reactive oxygen species.The results showed that O₂ and CO₂ concentrations in the storage environment were related to ROS metabolism and physiological quality.