Preparation And Properties Of LDH-ZnO Antibacterial Composite Material Based On Sodium Alginate

At present,in the face of environmental problems brought by plastic packaging materials,green active packaging materials have great development prospects.The research and development of such materials at home and abroad has become a hot spot.This topic focuses on the problems of bio-based composite materials with film-forming properties.Good sodium alginate and gelatin are used as film-forming substrates.By adding a new inorganic functional material hydrotalcite with a special layered structure and nano-zinc oxide with good antibacterial properties,the expected antibacterial properties of the composite material are achieved.After the optimal ratio,the antibacterial composite film is prepared by the casting process.The prepared antibacterial composite film is applied to the cold meat preservation test,and the effect of the antibacterial composite film on the shelf life of the chilled meat is evaluated by measuring different indexes.The main research contents and results are as follows:(1)Using sodium alginate and gelatin as the film-forming substrate,adding plasticizer glycerin and crosslinking agent anhydrous calcium chloride,casting on acrylic glass plate to prepare sodium alginate-gelatin-based composite film.Use single factor tests to explore the effects of sodium alginate content,gelatin content,glycerin content,anhydrous calcium chloride content,drying temperature and other factors on the tensile strength,elongation at break,water vapor transmission rate(WVP),and water solubility of the composite film And the influence of light transmittance.Through the orthogonal test of four factors and three levels,combined with range and variance analysis,the optimal preparation process of the composite membrane was obtained,that is,the ratio of sodium alginate to gelatin is 3:1,and the glycerol content is 25%(relative to sodium alginate).-The mass fraction of gelatin),the anhydrous calcium chloride content is 2%(relative to the mass fraction of sodium alginate-gelatin),and the drying temperature is 60°C.At this time,the performance of the composite membrane is good.(2)The inorganic antibacterial agent nano-zinc oxide and sodium alginate-gelatin are blended to prepare sodium alginate-based nano-zinc oxide antibacterial composite film.The properties of the composite film are measured,and the antibacterial effect of the composite film is explored through the antibacterial rate test.The composite film was characterized by FT-IR and SEM,and the thermal stability of the composite film was analyzed by DSC.After analysis,it can be known that when the content of nano-zinc oxide is 4%,the composite film has good mechanical properties and antibacterial properties,and the internal components of the composite film are tightly combined and have good thermal stability.(3)Combine hydrotalcite and nano-zinc oxide to form an enhanced antibacterial structure and sodium alginate-gelatin blend to prepare sodium alginate-based LDH-Zn O antibacterial composite film.The composite film is characterized by FT-IR,SEM,and DSC.The antibacterial rate test is to study the antibacterial effect of the composite film on Escherichia coli and Staphylococcus aureus,and the contact angle test is used to explore the surface properties of the composite film.After analysis,it can be seen that when the content of nano-zinc oxide is 4% and the content of hydrotalcite is 10%,the antibacterial rate of the composite film against E.coli and Staphylococcus aureus both exceeds 99%,showing strong antibacterial properties;A cross-linked network structure is formed between the molecules inside the membrane,and the thermal stability is high;the surface performance of the composite membrane is improved,and the hydrophilicity is reduced.(4)SA composite film without added antibacterial agent,antibacterial composite film added with 10% hydrotalcite-4% nano-zinc oxide and PE cling film were used in the fresh-keeping test of chilled meat,and passed the sensory evaluation and color difference of chilled meat,Weight loss rate,PH value,total number of colonies,TVB-N content and other indicators,in the test period(about 14 days)to evaluate the preservation effect of each composite film.The test results show that the antibacterial composite film can last for 12 to14 days for chilled meat,the SA film for 6 to 8 days for chilled meat,and the PE film for only4 to 6 days for chilled meat.Antibacterial film has the best fresh-keeping effect,followed by SA film,and PE film is the worst.Compared with PE film,antibacterial film can extend the shelf life of chilled meat by about 6 days.