| Starch is natural polymer composed of amylose and amylopectin, and under certain conditions it forms a helical inclusion complex with ligands such as fatty acid and glyceride. Inclusion complexes can modify the properties and functionality of starch, such as improving retrogradation, changing in-vitro digestibility and rheological properties and improving the antioxidant capacity of lipid. The starch-lipid complexes could be used for embedding lipid, and also used as thickening agent, stabilizer in numerous food applications, components of cosmetics and excipient in pharmaceuticals. In this thesis, the stearic acid was used as the ligand to produce corn starch-stearic acid complex with high pressure homogenization method. Different starch-lipid complexes were produced to investigate the influence of different ligands on properties and structure of complexes. Then slow releasing of corn starch-linolenic acid complexes were investigated through in vivo and in vitro experiments.In this study corn starches with different amylose content were physically modified by high pressure homogenization. High pressure homogenization led to starch granules breakage and particle size decrease. The strong mechanical force induced a decrease of the molecular weight and an increase of amylose content through breaking α-1,6-glucosidic bond. With the increase of amylose, the resistant ability of high pressure homogenization for starch was enhanced. Waxy corn starch particles completely collapsed when homogeneous pressure was 60 MPa, and amylose content was increased to 6.19% under the pressure of 120 MPa. Normal corn starch particles were completely broken and parts of starch particles collapsed when homogeneous pressure was 80 MPa, and amylose content was increased to 31.57% under the pressure of 120 MPa. There were still some complete high amylose corn starch particles when homogeneous pressure was 120 MPa, and amylose content was increased to 61.95%. High pressure homogenization could change the rheological properties of corn starch paste, and corn starch pastes were pseudoplastic fluid with shear-thinning property. Furthermore, high pressure homogenization could improve the solubility and swelling of corn starch, and improve retrogradation of normal corn starch and high amylose corn starch.The stearic acid was used as the ligand to produce corn starch-stearic acid complexes with high pressure homogenization method. The complex-forming ability of corn starch increased with the rising amylose content. The optimal process of waxy corn starch-stearic acid complexes was with 10% of starch, 1% of stearic acid(based on starch), 95 oC of pre-gelatinization temperature, 30 min of pre-gelatinization time, 100 MPa of pressure and 3 times of homogenization. The optimal process of normal corn starch-stearic acid complexes was with 8% of starch, 3% of stearic acid(based on starch), 95 oC of pre-gelatinization temperature, 30 min of pre-gelatinization time, 100 MPa of pressure and 3 times of homogenization. The optimal process of high amylose corn starch-stearic acid complexes was with 6% of starch, 4% of stearic acid(based on starch), 105 oC of pre-gelatinization temperature, 30 min of pre-gelatinization time, 100 MPa of pressure and 3 times of homogenization. Corn starch-stearic acid complex particles were compact, irregular flake or blocky structure with mattedly wrinkles surface. X-ray spectrum of waxy corn starch complexes was dispersive, while X-ray and 13 C nuclear magnetic resonance of normal corn starch complexes and high amylose corn starch complexes showed the formation of V-type helix complex. High amylose corn starch was most likely to form the complex, and enthalpy of complexes was up to 10.87 J/g. High amylose corn starch complexes with the lowest in vitro digestion was slowly digestible starch.Carbon chain length and unsaturation degree influenced the formation and characteristics of complexes. For medium chain fatty acids, the complex index and the fatty acid content increased with the increase of carbon chain length. For long chain fatty acids, the complex index and fatty acid content decreased with the increasing carbon chain length. Fatty acids with 12~20 carbon were more likely to form complexes. Complexes were all 61-V crystal. With the increase of carbon chain length, thermal stability and peak temperature of complexes were increased, while enzymolysis rate decreased. With the increasing unsaturated degree of fatty acids with 18 carbon, the complex index and the fatty acid content were increased slightly, while thermal stability and peak temperature of complex were decreased. The corn starch complexes were slowly digestible starch. Corn starch-linolenic acid complexes could improve the anti-oxidation property of linolenic acid through inhibiting the oxidation reaction. For corn starch-glyceride complexes, monostearin tended to form compelx with stronger hydrophilicity, but tristearin and soybean oil could hardly enter into helix hydrophobic cavity to form complex due to their structure and steric hindrance.In vitro experiments showed the corn starch-linolenic acid complex could slowly release linolenic acid during digestion. It could decrease LDL-C, TG and TC level of serum and liver, and inhibited liver damage for rats with high-fat diets. In other words, this kind of complex had a positive regulation for lipid metabolism of rats with high-fat diets. The slow releasing effect of corn starch-linolenic acid complexes was superior to linolenic acid with the same dosage. The corn starch-linolenic acid complexes could also improve antioxidant capacity of rats with high fat diets through improving enzymatic activity of CAT, SOD as well as GSH-Px, and consequently reducing MDA value. The antioxidant effect of the complex was superior to linolenic acid with the same dosage. |
PDF Full Text Request