| In order to understand interaction between starch and amino acids in food product,tapioca starch，maize starch, and three kinds of amino acids, lysine, glycine, glutamic acid,were selected/studied in this paper to investigate the effects of amino acids on the pasting andrheology characteristics of starches. Also the starch and amino acid mixtures were dry heatedto investigate its properties. Results of the experiment were as follows:The addition of lysine and glutamic acid increased breakdown and decreased the setbackof tapioca starch paste. Addition of Lys resulted in increases in peak viscosity and breakdown,decreases in total setback. Increases in breakdown and decreases in total setback and finalviscosity were observed when glutamic acid was added. However, Gly showed little effect onthe pasting property. Additions of amino acid resulted in no changes in solubility and swellingpower except for lysine addition in which the solubility and swelling power was increased.Amino acids had on effect on the birefringence〠granular shape and recrystallizationproperties of starch.With the addition of amino acid, the relative crystallinity of starch wasdecreased and the gelatinization temperatures (To and Tp) were increased; and enthalpy ofgelatinization(ΔH) were no changes in tapioca starch, but were decreased in maize starch.The starch gels were all weak gels with the additions of amino acids, except for additionof2%lysine the mechanical spectra of maize starch changed from weak gel to concentratedsolution. Except for glutamic acid/maize starch and glycine/tapioca starch gels, the tan ofstarch gels were increased with amino acids added, therefore starch/amino acid gels had moreliquid properties. power law model was observed for starch pastes of starch/amino acid, andeach paste was pseudoplastic fluid in the test range. Addition of amino acid, the behaviorindex m were increased and the pseudoplastic become weakened.After dry heating the birefringence decreased with maize starch/amino acid,birefringence in the center of the granules disappeared, whereas birefr ingence retained at theperiphery. In the starch/amino acid sample, some blister-like spots can be observed on thesurface of starch granules. These spots are more obvious on A-type starch granules. The FTIRspectra showed that there was an obvious peak appearance nearby the ester carbonyl C=Nstretching vibration peak on the spectra, that produced a new type of modified starch whichmaybe have an Maillard Reaction. The gelatinization temperatures were increased withaddition of lysine; glutamic acid had opposite effect on it. The enthalpy of gelatinization (ΔH)was decreased. After dry heating, the peak viscosity of maize starch significantly decreased,the peak viscosity of starch/lysine increased, and glycine had no obvious effect on it. Compared with the maize starch after drying, the peak and final viscosity of starch/lysine andstarch/glycine increased. These resulted indicated that lysine and glycine could protect thestarch, which made the viscosity of starch had little effects under dry heating. |
