Corn Straw Cellulose And Corn Distarch Phosphate Based Edible Films

This study was supported by the National Science & Technology Support Program of China(2015BAD16B05)“Development of New Logistics Packaging Materials for Anti-corrosion and Preservation”,and the Scientific and Technological Research Project of Jilin Education Department(JJKH20170435KJ)“Preparation of Antimicrobial and Biodegradable Packaging Material of Corn Straw Micro-nano Cellulose and Its Application in the Wild Vegetables Preservation of Changbai Mountain”.In this paper,corn straw were using as raw materials,the preparation process of corn stalk cellulose(CSC)and corn stalk nanocellulose(NCSC)were optimized,CSC and NCSC were applied to corn distarch phosphate(CDP)based edible films,the effect of ultrasonic/microwave-assisted treatment on the properties of edible films were studied.On this basis,the preparation process of corn distarch phosphate based and zein based double layer composite edible films(C/Z composite films)by dry lamination method was optimized,and the structure and properties of the edible films were characterized and analyzed.The antimicrobial effects of the corn distarch phosphate based edible films were studied,and the edible films were applied to the preservation of Ji'an white peach.The results were as follows:(1)Using corn straw as raw materials,the optimum process conditions for the preparation of CSC and NCSC were determined by single factor test and response surface test.The optimum conditions for preparation of CSC by ultrasound-assisted alkali method were as follows: Na OH concentration 8.7 g/100 m L,liquid-solid ratio 16: 1(m L/g),ultrasonic power 180 W,ultrasonic time 96 min,and the yield of CSC was 35.19%.The optimum conditions for preparation of NCSC by ultrasound-assisted sulfuric acid hydrolysis were as follows: H2SO4 volume fraction 64%,ultrasonic power 160 W,acid hydrolysis temperature 48 ?,acid hydrolysis time 78 min,and the yield of NCSC was 38.29%.Compared with CSC,the particle size of NCSC was reduced to nanoscale,the L value and a value of NCSC was significantly increased(p<0.05),b value decreased significantly(p<0.05),the NCSC were more white,more delicate,and the reflection of light was enhanced,the water swelling force was significantly increased(p<0.05),the water holding capacity was significantly reduced(p<0.05).Fourier transform infrared spectroscopy(FTIR)showed that hemicellulose and lignin were removed by sulfuric acid hydrolysis,and the NCSC still maintain the basic chemical structure of CSC.X-ray diffraction(XRD)analysis showed that the crystallographic types of CSC and NCSC were basically the same,the diffraction peak of NCSC were sharper and narrower,and the intensity were increased,the crystallinity were significantly increased(p<0.05).Thermogravimetric(TGA)analysis showed that thermal decomposition temperature of NCSC were slightly lower than the CSC,and the thermal decomposition temperature of CSC and NCSC were exceeded 200 ?,they all have good thermal stability.(2)Using CDP and CSC as the film forming substrate,the edible films were prepared by blending casting method.The optimum preparation process of edible films were optimized by principal component analysis and response surface test: CDP-CSC ratio 8.5: 1.5,CMC concentration 0.8 g / 100 m L,Gly concentration 1.0 g / 100 m L,the physical properties comprehensive score of edible films was 0.737.The tensile strength(TS),elongation at break(EAB),water vapor permeability(WVP),oxygen permeability(OP)and light transmittance(LT)of the edible films were 19.75 MPa?46.89%?1.167×10-12 g/(cm·s·Pa)?2.78×10-2 g/(m2·d·Pa)and 41.86%,respectively.The mechanical properties,barrier properties and LT were improved by adding CSC and by using ultrasonic/microwave-assisted treatment.FTIR and XRD analysis showed that the intermolecular interaction between the components of the CDP/CSC edible films were strong by ultrasonic/microwave-assisted treatment,and the properties of the edible films were improved.SEM analysis showed that the surface of CDP/CSC edible films were more smooth,the section of CDP/CSC edible films were dense and orderly,and the compatibility of the blend system was improved.(3)CDP/NCSC/polyethylene glycol(PEG)edible films(P-CDP/NCSC)were prepared by ultrasonic/microwave-assisted treatment.The results showed that TS and EAB of the edible films were increased by adding NCSC and PEG,and the TS and EAB of the P-CDP/NCSC edible films reached maximum values of 39.47 MPa and 135.75%.The barrier properties of CDP edible films were improved effectively by adding CSC,NCSC and PEG,WVP and OP were decreased significantly(p<0.05).FTIR and XRD analysis showed that hydrogen bonding between the molecules of edible films were enhanced by adding CSC,NCSC and PEG,CDP/NCSC edible films have higher crystallinity,and the toughness and compatibility of the edible films were improved by adding PEG.TGA analysis showed that the thermal stability of edible films were enhanced by adding CSC and NCSC.SEM analysis showed that uniform,continuous,dense structure of the edible films were formed by adding NCSC.(4)The optimum preparation process of C/Z composite films by dry lamination method were optimized by principal component analysis and response surface test: C and Z ratio 6:4,lamination temperature 135?,lamination times 3,the properties comprehensive score of C/Z composite films was 0.729.The TS?EAB?WVP?OP and LT of the C/Z composite films were 39.96 MPa?61.35%?0.4526×10-12 g/(cm·s·Pa)?0.8649×10-2 g/(m2·d·Pa)and 43.63%,respectively.Compared with CDP/NCSC edible films and P-CDP/NCSC edible films,TS were improved slightly,EAB and LT were decreased,and the properties of moisture and oxygen barrier were improved.FTIR analysis showed that strong hydrogen bonding association were generated between hydroxy,carbonyl,amino of Z films and hydroxy,carbonyl,double bond of C films,and the C/Z composite films still retained the basic structure of C films.XRD analysis showed that the diffraction peak intensity of C/Z composite films were higher than the C films obviously,and the crystallinity was improved.TGA analysis showed that the maximum degradation temperature of C/Z composite films was 305.57 ?,the maximum degradation temperature of C films was 294.18?,and thermal stability of C/Z composite films was improved.Macroscopic morphology and SEM analysis showed that the surface of C films,Z films and C/Z composite films were smooth,had no obvious particles,folds and holes,had good transparency and toughness.The section structure of C/Z composite films was double layer and compact,had no obvious phase separation phenomenon.(5)Antimicrobial effects of CDP based edible films studies showed that the growth and reproduction of gram-positive bacteria(S.aureus,B.subtilis)were inhibited effectively by adding Nisin.With the increase of Nisin,the inhibitory effect on E.coli and Aspergillus niger were obviously improved.Synergistic antimicrobial effects were produced by the combination of Nisin and ?-polylysine(?-PL).The combination of Nisin and ?-PL had good antimicrobial effects on gram-negative bacteria,and the antimicrobial effects on gram-positive bacteria were increased.Furthermore,the growth inhibition rate of Aspergillus niger mycelium was improved obviously.(6)CDP based edible films were applied to the preservation of Ji'an white peach,the results showed that the sensory quality,weight loss,browning index,hardness,soluble solids content,titratable acid content,vitamin C content,malondialdehyde content,peroxidase activity and polyphenol oxidase activity of coating treatment samples were better than the control samples.The protective layer on the white peach surface was formed by coating treatment,and the nutrient loss was reduced,the white peach ripening was delayed.Furthermore,the infection of microorganisms to fruit was inhibited,white peach rot was prevented,and storage time was extended.