Preparation,Characterization And Application Of Starch-Fatty Acid Nanocomposites

Starch nanoparticles（SNPs）can be used to prepare edible film for food preservation due to their characteristics like non-toxic,high degradability,good film forming property and good biocompatibility.However,the poor hydrophobicity,vulnerability to water erosion and poor mechanical properties of SNPs limit their application in food preservation.To improve the performance of SNPs,hydrophobic modification is needed.Fatty acid（FA）is a common component in food,and it can be combined with starch to form V-type complex,which can improve the anti-digestibility,film forming property and hydrophobicity of SNPs.In this study,starch-FA nanocomplex was prepared by using ultrasonic technology combined with alcohol precipitation.The effects of fatty acid chain’s length and unsaturation,and starch’s amylopectin content and crystal type on the structure and digestibility of starch-FA nanocomplex were explored.To study the microstructure and anti-digestion properties of starch-FA nanocomplex,Nano-size analyzer,X-ray diffraction（XRD）,Fourier infrared chromatography（FT-IR）,differential calorimetry（DSC）and other instruments,and in-vitro digestion was conducted.Moreover,the prepared starch-FA nanocomplex was used to prepare degradable films to explore the functional properties of starch-FA nanocomplex film and application in chicken preservation.（1）Using high amylost corn starch（HAS）as raw material to study the effects of FA chain length and unsaturation on the structure and digestibility of HAS FA nanocomplex（HASNP-FA complex）.The results showed that,with the increase of FA chain length and unsaturation,the apparent amylose content in HASNP-FA complex firstly decreased and then increased,while the contents of complex index（CI）,R_1047/1022,relative crystallinity and enthalpy（ΔH）,slow digestion starch（SDS）and resistant starch（RS）were firstly increased and then decreased.Concerning their apparent amylose contents,the HASNP-LA composite formed by lauric acid（LA）with 12 carbons and HAS had the lowest,while CI,R_1047/1022,relative crystallinity,ΔH,SDS and RS had the highest.These results suggested that the structure and digestibility of HASNP-FA complex could be regulated by adjusting the chain length and unsaturation of FA.Compared with other FAs,the HASNP-LA complex made by FAs that had 12 carbons had more stable structure and better anti-digestive properties.（2）Utilizing LA with the length of 12 carbons as ligand,to study the effects of amylopectin content and crystal type of starch on the structure and in-vitro anti-digestibility of starch-LA nanocomplex.The results showed that with the increase of amylopectin content,the apparent amylose content of starch-FA nanocomplex decreased,and the contents of CI,R_1047/1022,relative crystallinity,ΔH,SDS and RS increased.Concerning their apparent amylose contents,HASNP-LA complex formed by HAS with the highest amylopectin content and LA had the lowest,while CI,R_1047/1022,relative crystallinity,ΔH,SDS and RS had the highest.In order of increasing apparent amylose content,the starch-FA nanocomplexes,namely common corn starch-LA nanocomplex（NCSNP-LA complex）formed by LA and common corn starch（NCS,type A）,Potato starch-LA nanocomplex（PtSNP-LA complex）formed by LA and potato starch（PtS,type B）,and pea starch-LA nanocomplex（PtSNP-LA complex）formed by LA and pea starch（PS,type C）,would be listed as follows:PtSNP-LA complex<NCSNP-LA complex<PtSNP-LA complex,while the starch-FA nanocomplexes formed by the combination of LA with CI,R_1047/1022,relative crystallinity,ΔH,SDS and RS,would be listed as:PtSNP-LA complex>NCSNP-LA complex>PtSNP-LA complex.These results indicated that the structure and digestibility of starch-FA nanocomplex could be regulated by changing the content and crystal type of amylopectin.Moreover,HASNP-LA complex and PtSNP-LA complex prepared by HAS with high amylopectin content and B-type PtS were more stable in structure and better in anti-digestion performance.（3）Employing PtS as raw materials,to study the effects of the chain length and unsaturation of FA on the properties of the potato starch-FA composite film（PtSNP-FA composite film）,which would be applied in chicken preservation.The results showed that with the increase of FA chain length and unsaturation,the water content,water solubility,water vapor permeability,light transmittance and Vc release value of the PtSNP-FA composite film all decreased firstly and then increased,and the contents of R_1047/1022,SDS and RS of the PtSNP-FA composite film firstly increased and then decreased.Compared with other PtSNP-FA composite films,the potato starch-LA nano-composite film（PtSNP-LA composite film）had the lowest water content,water solubility,water vapor permeability,light transmittance and Vc release value,and the highest contents of R_1047/1022,SDS and RS.In addition,with the increase of chain length and unsaturation of FA,the juice loss,total number of colonies,pH value and volatile base nitrogen（TVB-N）of chicken packaged with the PtSNP-FA composite film firstly decreased and then increased during the storage time of 9 days.What is more,the chicken packaged with PtSNP-LA composite film had the lowest juice loss,total number of colonies,pH value and TVB-N during storage time.These results indicated that the functional properties of the PtSNP-FA composite film could be improved by adjusting the chain length and unsaturation of FA,so that it could be used in the preservation of chicken and prolong the shelf life of chicken.