Youming Liu

Effects of salts on the gelatinization and retrogradation properties of maize starch and waxy maize starch

The objective of this study was to evaluate the effects of salts on the gelatinization and retrogradation of maize and waxy maize starch. Experimental results showed that the salting-out or structure-making ions, such as F(-) and SO4(2-), decreased the swelling power, solubility and transparency of both starches, but increased the gelatinization temperature, enthalpy, and syneresis, due to the tendency of these ions to protect the hydrogen bond links among starch molecules. On the other hand, the salting-in or structure-breaking ions, such as I(-) and SCN(-), exhibited the opposite effects. Microscopic observations confirmed such effects of salts on both starches. Furthermore, the effects of salts were more significant on waxy maize and on normal maize starch. Generally, salts could significantly influence on the gelatinization and retrogradation of maize and waxy maize starch, following the order of the Hofmeister series.

Effects of the Acid- and Alkali-Aided Processes on Bighead Carp (Aristichthys nobilis) Muscle Proteins

The objective of this study was to investigate the effects of the acid- and alkali-aided processes on bighead carp (Aristichthys nobilis) muscle protein as compared with the conventional washing method. Acid- and alkali-aided processes resulted in higher protein recoveries than conventional washing method. In textural profile analyses, the highest hardness and cohesiveness were observed in the gels prepared by conventional washing and alkali-aided processing (p < 0.05). No endothermic peak was found in the differential scanning calorimetry thermogram of protein isolates after acid- and alkali-aided processes. The hydrophobic interactions and disulfide bonds were the main chemical bonds to maintain the stability of the gel matrix, while the sulfhydryl group in bighead carp muscle was apt to be activated during alkali-aided processing. The α-helical content of actomyosin decreased remarkably after the acid- and alkali-aided processes (p < 0.05). Overall, there is a potential to apply the alkali-aided processing to extract proteins from bighead carp muscle for the production of surimi-based seafoods.

Comparison of Conventional Washing Processing and pH Shift Processing on Gelation Characteristics of Bighead Carp (Aristichthys nobilis) Muscle Proteins

ABSTRACT In this study, gelation characteristics of bighead carp (Aristichthys nobilis) protein isolates prepared by pH shift processing were investigated as compared with those of surimi prepared by conventional wash processing. Results showed that the gel from alkali-aided protein isolate exhibited a higher breaking force than that from conventional washed surimi (p < 0.05). However, the gel from conventional washed surimi had higher whiteness (p < 0.05) and lower expressible moisture (p < 0.05). The rheological study showed that protein isolates exhibited different storage modulus and loss tangent patterns from conventional washed surimi during heating. Acid-aided processing could lead to higher denaturation and dissociation for fish muscle myosin and a coarser gel network from the sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) pattern and the scanning electron microscopy (SEM). Overall, there is a potential to apply pH shift processing, especially alkali-aided processing, to extract more proteins from bighead carp muscle for the production of surimi-based food.