| In this research, two negatively charge-carrying amino acids (Asp and Glu) and two positively charge-carrying amino acids (Lys and Arg) were selected to understand interaction between charge-carrying amino acids and potato starch. The differential scanning calorimetry (DSC), laser particle size analyzer, FTIR and X-ray diffraction were used to investigate the effects of charge-carrying amino acids on the gelatinization, retrogradation and rheology characteristics of potato starch. Results of this study were as follows:The transparency and swelling power of potato starch were reduced by aspartic acid, glutamic acid and lysine, but increased by arginine. The result of DSC showed that, with the addition of aspartic acid, glutamic acid and lysine, the onset and peak temperature of potato starch were increased. The addition of arginine decreased the onset and peak temperature of potato starch. Enthalpy of gelatinization was decreased by those four charge-carrying amino acids in potato starch. The FTIR spectrogram indicated that the peak width of hydrogen bond of starch paste with charge-carrying amino acids increased, while others had no markedly charge, it demonstrated that no new groups generated between potato starch and charge carrying amino acids.There were no changes in retrogradation property of potato starch with lysine and arginine, while aspartic and glutamic acid addition in which the retrogradation were increased. The freezing-thawing stability of potato starch was reduced by aspartic acid, glutamic acid and lysine, but increased by arginine. The gel strength was increased when lysine and arginine added in potato starch. Aspartic acid and glutamic acid in low concentration might increase the gel strength of potato starch. L*, b*and a*value of potato starch were increased by arginine. Aspartic acid, glutamic acid and lysine decreased L*value of potato starch, but increased the b*and a*value.. The result of X-ray diffraction showed that charge-carrying amino acids had no charges in potato starch in X-ray diffraction pattern, but decreased the relative crystallinity.The storage modulus (G’) and loss modulus (G") decreased with adding aspartic acid and glutamic acid in potato starch. With the concentration of lysine increased, G’ and G" of potato starch also increased, but were inferior to control. The storage modulus (G’) and loss modulus (G") increased with the concentration of arginine. The starch gels were all weak gels with the additions of charge-carrying amino acids. Except for glutamic acid/potato starch gels, the tanδ of potato starch gels were increased with amino acids added, therefore starch/amino acid gels had more liquid properties. In the test range, power law model was observed for starch pastes of potato starch/charge-carrying amino acid, and each paste was pseudoplastic fluid. The k values of potato starch with charge-carrying amino acids paste were lower than starch without amino acids. Addition of acidic amino acids, the consistency coefficient index k decreased, but higher than control, while the behavior index n decreased. Addition of basic amino acids, the behavior index n decreased, the consistency coefficient index k increased. The k value of potato starch added with0.lmol/kg Lys and Arg was larger than the addition of0.05mol/kg and0.2mol/kg, respectively. The pseudoplastic of all starch paste sample were become strengthen. |
