Effect of non-starch components in liangpi slurry on thermal and rheological properties of concentrated wheat starch gels

Liangpi, a traditional Chinese cold skin noodle, primarily consists of wheat starch in a concentrated gel system. However, high-quality liangpi cannot be solely produced with pure wheat starch. The effects of endogenous non-starch components in liangpi slurry (LPS) on wheat starch properties were investigated by mixing LPS with wheat starch slurry (WSS) in various LPS/WSS ratios. Results showed that increasing LPS/WSS ratios significantly enhanced the swelling power and water-holding capacity at 70 °C and 90 °C. The gelatinization onset temperature of LPS/WSS samples rose from 80.5 °C for pure WSS to 83.3 °C for LPS. The peak viscosity of LPS was more than three times higher than that of WSS, and the breakdown viscosity also increased with the incorporation of non-starch components. In concentrated systems, the storage modulus (G') and loss modulus (G") of the resultant gels gradually increased with higher LPS/WSS ratios. However, gel fluidity, frequency dependence of G', and gel hardness do not exhibit a linear relationship with LPS/WSS ratios, reaching their maximum values at LPS/WSS ratios of 6:4 or 4:6. Their trends were also similar to gel cohesiveness and the critical strain under large amplitude oscillatory shear. This suggested that non-starch components improved small deformation properties but compromised gel stability under large deformations. This was further evidenced by Lissajous curves evolution of LPS gels, with LPS gels showing higher strain hardening coefficient, shear thinning coefficient, and harmonic ratio compared to WSS gels. This study points the way for future research to identify the specific non-starch component that matters.