Molecular Structure And Functional Properties Of Coix Seed And Its Starch And Protein

The composition and distribution of nutritional components in three different adlay seeds(Qian No.2,Pu No.6,Dabaike)were investigated.The molecular structural and thermodynamic properties of starches,proteins and coix seeds powders of different varieties of coix seeds were studied by scanning electronmicroscope(SEM),wide X-ray diffraction(XRD),small angel X-ray scattering(SAXS),solid state nuclear magnetic resonance(SSNMR),polyacrylamide gel electrophoresis(SDS-PAGE),circular dichroism(CD),rapid viscosity tester(RVA),differential scanning calorimeter(DSC)and rheometer.The main objective of this study is to provide fundamental data and theoretical guidance for the rational utilization of adlay seeds for food and non-food products.It also makes theoretical reference for the application of new starches and proteins in modern industry,and supplementing the existing research data of starches and proteins.The main conclusions are as follows:(1)Nutritional properties of adlay seedsThe adlay seeds had excellent nutritional quality and health benefits.The half-polished adlay seeds contained 37%-43% of starch,20%-24% of fat,14%-18%of fiber and 16%-18% of protein.There were 43%-55% of starch and 17%-21% of protein in the polished adlay seeds.While the main components of the adlay shells were fiber(65～72%)and ash(16～21%),the main ingredients of the adlay brans included fiber(41～48%),protein(12～21%)and fat(19～22%).The half-polished and polished adlay seeds and the adlay brans contained B-type vitamins and VE,and mineral elements such as P,K,Mg and Ca.The content of unsaturated fatty acids in the edible parts of adlay seeds was ca.85%,with main fatty acids being oleic acid,linoleic acid and palmitic acid.The fatty acid composition and protein quality in the edible parts of Qian No.2 adlay were the best,accompanied by a high content of polyphenols in its bran.Dabaike adlay had highest contents of vitamin and minerals in its edible parts,with a highest content of flavonoids in the bran.Pu No.6 adlay showed the highest contents of essential amino acids and eoixol.(2)Molecular structure and functional properties of coix seed starchesCoix seeds showed the high contents of amylopectin,the granular appearance of starches was mainly oval or truncated oval with the regular shape.The size of starches granules was big(19.17～22.24μm),which belongs to large granular starches.The integrity of the semi-crystalline lamellae of three varieties of coix seeds starches was consistent.Qian No.2 starches had the thinnest semi-crystalline lamellae(9.2021nm)and the highest degree of ordering in double helix structure and semi-crystalline lamellae.Dabaike starches had the lowest degree of ordering in double helix structure and the lower degree of ordering in semi-crystalline lamellae.The crystal structure of coix seeds starches was A type crystal,and the crystallinity was 35.08% ～ 39.36%.The content of double helix in coix seeds starches wass ca.38% ～ 47%.The initial gelatinization temperature of coix seeds starches was higher(65.80～68.35 ℃),and the enthalpy was higher(12.43～14.36J/g).This shows that coix seeds starches was not easy to gel.Pu No.6 starches had the highest peak viscosity and the best stability of hot paste of.Qian No.2 had the best anti-aging properties.The rheological properties of coix seeds starches shows no significant differences,and the viscoelasticity of the system increased at first and then decreased with the increase of temperature,besides,the elasticity was always larger than viscosity during the heating process.(3)Molecular structure and functional properties of coix seed proteinsThere was no significant differences in the structure of the same component protein of different varieties of coix seeds.There were some differences in the structure of different components of the same kind of coix seeds.There were 5 protein bands in coix seeds albumin,the molecular weight was ca.24 k D,33 k D,60 k D,74 k D and 144 k D,and the secondary structure was higher in β-sheet(33.87% ～ 45.07%).Globulin contains 7 protein bands,which was ca.13 k D,20 k D,23 k D,30 k D,36 k D,67 k D and 75 k D,and the secondary structure was higher in β-turn and random coil.Prolamin contains only 4 protein bands,mainly distributed at 14 k D,18 k D,25 k D and40 k D,and the secondary structure was higher in α-helix structure(59.70% ～ 79.53%).Glutelin contains 10 protein bands,the molecular weight was ca.13 k D,15 k D,25 k D,30 k D,35 k D,55 k D,70 k D,81 k D,90 k D and 100 k D,and the secondary structure was were higher in β-sheet(41.23% ～ 61.40%).The wide X-ray diffraction of glutelin showed a diffraction peak near 10° and 20°,and glutelin had higher crystal quality with higher crystallinity(45%～54%).With the increase of temperature,the elasticity of glutelin decreased rapidly at first,then increased slowly and decreased slowly at last,and the viscosity decreased gradually.Glutelin did not detect the denaturation temperature in the thermal properties test,possibly due to the destruction of the structure of glutelin under alkaline conditions during the preparation process.(4)Interaction between starch and protein of coix seeds and its effects on functional propertiesCoix seeds powder particles mixed with many small particles and large pieces of debris with rough surface.The volume average particle size was 82.38～102.28μm.The crystal structure of coix seeds powders was A type crystal,and the crystallinity was 24.45%～33.48%.The initial gelatinization temperature of coix seeds powders was 65.80～68.35 ℃,and the enthalpy was 12.43～14.36J/g.The peak viscosity of coix seeds powders(1956.00～2873.00 c P)was higher than that of indica rice powders,and the anti-aging properties was also.The viscoelasticity of the system increased at first and then decreased with the increase of temperature,besides,the elasticity was always larger than viscosity during the heating process.The crystal structure of coix seeds powders and starches were both A type crystal.The particle size distribution coix seeds powderes was double peak while starches was single peak.In addition,the size of coix seeds powders was several times larger than starches,the crystallinity was smaller than starches,the initial gelatinization temperature was slightly higher than starches,the enthalpy was smaller than starches.It was because that there was a mixed system with coix seeds powders starches and proteins,in which the interaction between several macromolecules lead the structural and functional properties between coix seed powders and starches similar but different.