Study On The Preparation And Preservation Effect Of Navel Orange Pomace Active Film

Navel oranges are concentrated at the ripening stage and prone to decay,thus leading to large losses.Most of the navel orange processing is at the primary stage of commercialization and processing,which easily produces a large amount of peel residue.The commonly used inappropriate treatment methods such as incineration and landfill will lead to serious environmental pollution and resource wastage,thus restricting the development of the navel orange processing industry.In view of the significant issues of resource wastage resulting from the irrational utilization of citrus peels and the environmental contamination caused by non-degradable plastics.In this study,navel orange pomace was used as the research object to prepare bio-based composite films with chitosan and glycerol as the main additives.The navel orange pomace film was optimized by response surface test.On this basis,in order to improve the performance of navel orange pomace film,chestnut shell brown pigment,and citric acid were added to prepare navel orange pomace active film.The properties of the active films were tested and the microstructures were analyzed by using scanning electron microscopy,X-ray diffraction and Fourier transform infrared spectroscopy.Finally,the active film was applied to the preservation of fresh-cut apples and its preservation effect was evaluated by principal component analysis.The specific conclusions of the study are as follows:(1)The optimized conditions were determined to be 1.10% chitosan,4.10% navel orange pomace,and 0.90% glycerol.After optimization,the tensile strength of the film was 15.76 MPa and the elongation at break was 19.23%.The ANOVA showed that glycerol content had the most significant effect on tensile strength and elongation at break,and the interaction of navel orange pomace content and chitosan content significantly affected the tensile strength of the films.In addition,this study also verified the applicability of the optimized formulation on Nanfeng mandarin and Majia pomelo peel residue.The results showed that although Majia pomelo peel residue films exhibited the best tensile strength,the mechanical properties of Nanfeng mandarin and Majia pomelo peel residue films were insufficient compared to navel orange pomace film.Overall,this study demonstrated that citrus peel residue and chitosan can be processed into bio-based composite films with certain mechanical properties.(2)The addition of brown pigment not only improved the active film’s tensile strength and surface hydrophobicity,but also reduced water vapor permeability,increased the release of phenolic substances in simulated environments,and improved its antioxidant capacity.The addition of citric acid increased the elongation at break of the film,providing the ability to inhibit Escherichia coli and Staphylococcus aureus for the active film.Citric acid also protected the color brightness of the film,promoted the release of phenolic substances in the film,and accelerated the degradation of the film in the soil.The combination of brown pigment and citric acid increased the elongation at break and contact angle of the film based on a certain tensile strength and significantly reduced its water vapor permeability.Citric acid acted as a synergist of brown pigment to improve the free radical scavenging ability and iron ion reduction ability of the film,while brown pigment was able to increase the antibacterial ability of the films under the action of citric acid.In addition,it was found that a small amount of citric acid and brown pigment could be well mixed with navel orange peel film.No additional absorption peaks and significant wavenumber shifts were observed in the infrared spectrum,indicating that no new covalent bonds were generated between them.(3)The active film was used to preserve fresh-cut apples for a short time(24 h)at room temperature,the active film could reduce the evaporation of water on the surface of the sample,inhibit the activity of polyphenol oxidase,and reduce the occurrence of apple browning,so as to maintain the appearance quality of the samples.Through PCA comprehensive analysis,the shortterm preservation effect of the active film was better than that of the traditional plastic film,and it had the potential to replace the traditional plastic film.In summary,this study used navel orange peel to prepare bio-based films and applied them to actual preservation.The results of the study provided a reference for the development and in-depth study of navel orange peel resources,as well as ideas for the sustainability of the whole industry chain of navel oranges.