Effects of oat antifreeze protein on quick-frozen dumpling wrapper during freezing and storage

Abstract: This study aims to investigate the effect of oat antifreeze protein on the non-fermented dough during freezing, together with the quality changes during the processing of the dumpling wrapper. The 0.5% oat antifreeze proteins were added to the dumpling wrapper. A systematic evaluation was then made on the oat (Avena sativa L.) Antifreeze Proteins (AsAFPs) in the frozen dumpling wrapper during freezing and storage. Some parameters were also measured to clarify the regulatory mechanism, including the moisture content, freezable water content, color, texture, rheological properties, the free sulfhydryl group, disulfide bond content, and secondary structure of hydrated gluten at different freezing periods. The results showed that the moisture content of the dumpling wrapper significantly decreased from 33.22% to 29.34% (from 34.98% to 26.57% in the control group) after 28 d freezing and storage, indicating that the addition of AsAFPs could greatly contribute to slowing down the moisture loss. The freezable water content of the dumpling wrapper after AsAFPs addition was lower than that in the control group (P<0.05). As such, much fewer ice crystals were beneficial to alleviate the mechanical damage to the network structure during freezing. The brightness of the dumpling wrapper was only slightly reduced after AsAFPs addition, which was related to the color of AsAFPs. More importantly, the dumpling wrapper in the AsAFPs group shared the better textural properties, lower hardness, gumminess and higher springing, cohesiveness, chewiness, and resilience (P<0.05). The elastic and viscous modulus of dumpling wrapper in the AsAFPs group was much higher than that of the control group (P<0.05). The change was attributed to the weak gluten cross-linking effect after AsAFPs addition. The sulfhydryl content of the AsAFPs group was lower than that of the control group (P<0.05), while the disulfide bond content was higher than that of the control group (P<0.05). It infers that the addition of AsAFPs could greatly contribute to inhibiting the breakage of the disulfide bond. There was a slightly decreasing trend in the α-helix and random-coil of hydrated gluten of dumpling wrapper, whereas, an overall increasing trend in the β-sheets and β-turns. Nevertheless, the AsAFPs was used to inhibit the breakage of hydrogen bonds and other stable groups, leading to the smaller decrease of random-coil and α-helix (P<0.05). The finding can provide a strong reference for the application and quality improvement of antifreeze proteins in non-fermented doughs.