The effects of different charge-carrying amino acids (lysine, aspartic acid, and tyrosine) on the long-term retrogradation properties of normal corn starch (NCS) gel were studied by differential scanning calorimetry, X-ray diffractometry, low-field nuclear magnetic resonance, and dynamic rheological tests. The results suggested that these amino acids could inhibit the long-term retrogradation of NCS gels, among which the positively charge-carrying amino acid (lysine) showed the most significant inhibitory effect and the zero net charged amino acid (tyrosine) exhibited the worst inhibitory effect. These amino acids significantly decreased the retrogradation enthalpy, hardness, and R1047/1022 value of NCS gels, as well as inhibited the recrystallization of NCS. The results of retrogradation kinetics suggested that the recrystallization of NCS with amino acids followed the instantaneous nucleation and the crystallization rate constant k of recrystallization was reduced by these amino acids. The amino acids could interact with starch molecules to form hydrogen bonds and steric hindrance during the recrystallization process, which prevented the formation of double helix structures, as well as reduced the water diffusion and exudation from NCS. Therefore, the lysine could be used as a good retrogradation inhibitor for starch in food industry.
Keywords: Amino acid; Corn starch; Lysine; Retrogradation.
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