Preparation Of Composite Card Containing CO₂ And Lemongrass Essential Oil And Its Application In Strawberry Preservation

Strawberry is a kind of fruit with unique flavor and bright appearance.However,postharvest strawberry is prone to decay at room temperature,which is caused by its high respiratory and metabolic rate and pathogen infection.The combination of inhibiting the growth of pathogenic bacteria and regulating the gas composition of the storage environment is an effective means to extend the shelf life of strawberry,but few existing studies can meet this requirement.Therefore,this study aims to prepare a fruit preservation composite card that can be used in a high humidity environment by 3D printing,and explore its influence on the preservation effect of strawberry.The composite card was divided into three layers:upper layer,middle layer and lower layer.The upper and lower layers were sodium alginate（SA）membranes containingβ-cyclodextrin（β-CD）inclusion complexes of vanilla essential oil（LEO）,and the intermediate layer was sugar granules containing CO₂（SGR）.Water acts as an external trigger to melt SGR,stimulate the release of CO₂ from SGR,reduce O₂components in the packaging environment,and combine with LEO,which has a wide antibacterial spectrum,to achieve the dual preservation purpose of antibacterial and respiratory intensity reduction.The main research results are as follows:（1）The mass ratio of sucrose to corn syrup（w/w）was 9:1,8:2,7:3,6:4,5:5,and the influence of sucrose to SGR agglomeration and melting rate was explored.The results showed that the aggregation degree and melting rate were optimal when the mass ratio was7:3,and the CO₂ loading rate in SGR was 27.47±1.09%.（2）The mass ratio of LEO andβ-CD 1:1,1:3,1:6,1:9 and 1:12（w/w）were selected to prepare the inclusion complexes,and their effects on the properties of the inclusion complexes were investigated.The results showed that the embedding rate was the highest（76.20±2.46%）when the mass ratio was 1:6.At this time,the particle size is the smallest（1075.33±26.89 nm）,indicating that the aggregation degree of inclusion complexes is the smallest at this time.At the same time,Zeta potential（absolute value）was the highest（30.60±0.35 m V）,and the system was the most stable.Therefore,the mass ratio of 1:6 was selected to prepare the inclusion complex.（3）In exploring the influence of different printing speeds on SA film（15%,35%,50%,75%,100%mm/s）,the printing speed of 50 mm/s SA film texture contour is the most clear and complete,so choose 50 mm/s speed printing composite card.（4）When exploring the influence of different contents of inclusion complex on the performance of SA film（1%,2%,3%,4%,5%）,it was found that the addition of clathrates increased the thickness of SA film,and decreased the mechanical properties,water vapor permeability and water solubility of SA film.SEM showed that when the amount of LEO/β-CD inclusion complex was too much,the film would crack more,and 3D printing or drying would cause the fracture of the composite film.Therefore,composite film with 5%inclusion complex content was selected to prepare composite cards.When 5%inclusion compound was added,the antibacterial and antioxidant capacity was the strongest,the growth diameter of ash mold was 9.4±0.57 mm,and that of Aspergillus Niger was 7.6±0.23 mm.Therefore,the SA film containing 5%inclusion compound was selected to prepare the composite card.（5）Combining the above optimized SA film with SGR for strawberry preservation,we found that only SA-LEO/β-CD composite card delayed the decline of strawberry hardness and soluble solids,reduced the weight loss rate and inhibited the growth of spoilage bacteria.SA-LEO/β-CD-SGR₃composite card has the best effect on strawberry preservation,which can effectively delay the change of strawberry color,maintain the hardness and soluble solid of strawberry,reduce the weight loss rate,inhibit respiratory intensity and prevent the growth of mold so as to extend the shelf life of strawberry.However,when the amount of SGR was too high,the firmness of strawberry was decreased,and the anaerobic respiration of strawberry was induced,and the spoilage of strawberry was accelerated.