Process optimization of fresh noodle compound anti-aging additives and Avrami retrogradation kinetic

Abstract: Fresh noodles are enjoyed by the majority of consumers in recent years, because they maintain the conventional sense such as freshness and chewiness and are easier to store. But fresh noodle starch may form ordered or disordered colloidal net structure because of intermolecular hydrogen bonds during gelatinization. With the prolongation of cooling time, the distance between the colloidal net structure continues to narrow, which leads to 3 results: the colloidal structure of starch gel is getting more closely; the space between the colloidal structure of starch gel reduces; the phenomenon of dehydration occurs in starch gel molecules. When the recrystallization appears, the hardness of starch gel increases, which is the reason why starch is easy to aging during the shelves and seriously affects the quality of fresh noodle. In order to restrain the retrogradation of fresh noodle's starch, this paper investigated the effects of guar gum, sodium stearyl lactate (SSL), soluble soybean polysaccharide (SSPS) and β-cyclodextrin (β-CD) on the inhibition of retrogradation for starch of fresh noodle during storage period. Based on a large number of preliminary experiments and single factor experiments, the inhibitory effects of compound anti-aging additives on fresh noodle were studied. Through the experiment design of response surface methodology with 4 factors and 3 levels based on the principle of Box-Behnken design, using the software Design-Expert 8.0, this paper made a significance test for the model and discussed the interactions among factors. Ultimately, through differential scanning calorimeter (DSC), the thermodynamics parameter and the ageing dynamic equation under the optimum condition of fresh noodle starch were studied. The result showed that quadratic model was the best model to describe the interaction between the factors (P<0.0001). The correlation coefficient and adjusted determination coefficient were 0.9389 and 0.8598, respectively. Interactions of inhibition between guar gum and SSL, SSPS and β-CD were significant (P<0.01), and interactions between guar gum and SSL, SSPS and β-CD (P<0.01) were the same. When guar gum, SSL, SSPS and β-CD were 0.4%, 0.22%, 0.18% and 0.15%, the hardness of the fresh noodle was 48.01 N by the software prediction. Under these conditions, the hardness of fresh noodle during the storage (on the 7th day) reached 41.01 N by verifying test. The DSC study showed fresh noodle prepared under the optimal conditions had denser and more orderly structure than the control group; the enthalpy required by the recrystallization of melting amylopectin gradually reduced compared to the control group. By establishing the Avrami equation of aging kinetics, it was found that the growth rate of recrystallization for fresh noodle under optimal conditions was also less than the control group. And compared to the control group, the nucleation mechanism was close to the spontaneous nucleation for the preparation of fresh noodles under the optimal conditions. So the optimal anti-aging compound additives can well retard the starch retrogradation of fresh noodle, which can maintain the fresh noodle quality and delay the fresh noodle's shelf life.