Preparation And Characterization Of Peanut Red Polyphenol-sodium Alginate Functional Composites

Because of its biodegradability,processability,composability,and lack of food pollution,biomass polymer materials have become a hotspot for study in food packaging,wound healing,and other sectors.Sodium alginate is a natural polysaccharide that has been widely used in the preparation of biodegradable composite films and hydrogels due to its excellent water solubility,gelability and biocompatibility.However,Polysaccharides,as natural polymeric materials,can directly or indirectly provide nutrient sources for a large number of microorganisms（bacteria,fungi,etc.）in the air,promoting bacterial and fungi reproduction and growth while causing irreversible damage to the performance and service life of natural polymeric materials.To improve food safety,lengthen food shelf life,and reduce the incidence of foodborne illnesses,this paper designed and prepared two compound antibacterial materials based on sodium alginate.The specific research contents are as follows:（1）Response surface methodology（RSM）was used to optimize the extraction conditions of polyphenols in peanut red extract（PSE）,the main chemical components of the extract were analyzed,and the minimum antibacterial concentration and antibacterial effect were determined.The results showed that the following were the PSE extraction’s best parameters:ethanol concentration of 80%,solid-liquid ratio of 1:20,ultrasonic time of 40 minutes,temperature of 60°C,and total phenol content of 137 mg/g.Thymol and catechin are the main polyphenol active components of PSE.Additionally,the bacteriostatic effects of PSE on 4 kinds of bacteria are as follows:Salmonella typhimurium（MIC,1.4 mg/m L）>Staphylococcus aureus（MIC,1.4mg/m L）>Escherichia coli（MIC,2.8 mg/m L）>Listeria monocytogenes（MIC,2.8 mg/m L）.（2）The SA/CNF/Ca²⁺composite film and the SA/CNFs/Ca²⁺/PSE（SCCP）antibacterial composite film were prepared by nanocellulose（CNFs）and sodium alginate（SA）.Compared with the SA/CNFs/Ca²⁺film,the SCCP composite film has higher strength,good water resistance,and excellent UV blocking properties.The Antibacterial and antioxidant tests showed that the ABTS free radical scavenging activity of the composite film was higher than that of DPPH radical scavenging activity,and the maximum ABTS scavenging activity was 99.28%;The antibacterial rate of SCCP composite film against Salmonella typhimurium was 94.48%,followed by Staphylococcus aureus（93.38%）,Escherichia coli（79.88%）and Listeria monocytogenes（71.50%）.The fruit preservation test revealed that fruits immersed in SCCP film solution had a lower rate of decay and weight loss than those of fruits in the control group.（3）In order to improve the stability and bioavailability of PSE,the inclusion complex（IC）was prepared by encapsulating PSE with hydroxypropyl-β-cyclodextrin（HP-β-CD）,and further the small particle size and well-dispersed inclusion-silver nanoparticles（IC-Ag NPs）composite nanomaterials were prepared by using IC as a reducing and stabilizing agent.The results showed that the encapsulation rate of IC was87.26%,and the storage rate of IC was higher than that of PSE in all three humidity environments compared with PSE;According to the sustained release test results that IC could rapidly release the active polyphenolic substances from PSE at a p H value of 7.2.The best process parameters for the preparation of IC-Ag NPs were obtained by RSM analysis,which were IC concentration of 10.4 mg/m L,Ag NO₃ concentration of 0.6 m M,reaction temperature of 90℃;the optimized IC-Ag NPs particle size distribution is uniform,with an average size of 16.17 nm and a silver ion reduction rate of 88.47%.The catalytic degradation efficiency of4-nitrophenol was 97.99%in 5 minutes due to IC-Ag NPs’s good quick catalytic performance.In comparison to PSE and HP-β-CD,the green synthesized IC-Ag NPs demonstrated outstanding antibacterial activity against Gram negative（positive）bacteria,with minimal inhibitory concentrations of 4.5μg/m L for Staphylococcus aureus and 9μg/m L for Escherichia coli,respectively.The lowest bactericidal concentration measured was 72μg/m L.（4）To expand the application range of IC-AGNPs,Sodium alginate/Gluconate-δ-lactone/Ca²⁺（SGCA）hydrogel was created for controlled transport of IC-AGNPs,and the binding mechanism of the hydrogel was studied using FT-IR,DSC,XPS,SEM,and XRD.The behavior of SGCA hydrogel under varied p H settings was also investigated.The results showed that when the concentration of IC-Ag NPs is larger than 0.8 mg/m L,the mechanical strength of the hydrogel decreased as the IC-Ag NPs concentration increased.The maximum cumulative release of IC-Ag NPs was 98.21%in the hydrogel’s p H 6.8 phosphoric acid buffer solution,which controlled the release by diffusion.The rheological characteristics of hydrogel revealed that when the concentration of IC-Ag NPs was larger than 0.4 mg/m L,the G’and G"values of SGCA hydrogel decreased.Antioxidant results showed that the scavenging rate of SGCA hydrogel to ABTS free radicals was 93.82%in the environment of p H 6.8.Bacteriostatic results revealed that hydrogels loaded with IC-Ag NPs had a stronger bacteriostatic effect on Gram-negative bacteria than on Gram-positive bacteria,which was due to differences in the content and structure of the bacterial cell wall.