精准反馈微波加热对金线鱼肌原纤维蛋白理化特性的影响

    Effects of precision feedback microwave heating on the physicochemical properties of myofibrillar proteins in Nemipterus virgatus

    • 摘要: 为探究精准反馈微波加热(precision feedback microwave heating,PFMH)对金线鱼肌原纤维蛋白理化特性的影响,该研究以金线鱼肌原纤维蛋白为研究对象,并以传统水浴加热作为对照,测定PFMH不同温度和加热时间下肌原纤维蛋白的浊度、表面疏水性、荧光强度、紫外吸收度、热稳定性、凝胶电泳图谱、表面形貌和鱼糜凝胶化学作用力的变化。结果表明,与对照组相比,PFMH在85 ℃加热1 min后肌原纤维蛋白浊度和表面疏水性分别提高了129.41%和52.51%,荧光光谱呈下降趋势,紫外光谱呈现上升趋势,表明其三级结构发生了改变;差示扫描量热仪结果显示,PFMH处理的肌原纤维蛋白的降解温度(Td)提高了13.65%,焓变值(ΔH)降低了93.02%,提高了肌原纤维蛋白的热稳定性,防止肌原纤维蛋白的热变性和降解。同时,凝胶电泳图谱和原子力图像表明,85 ℃加热1 min有利于肌原纤维蛋白展开,形成致密的凝胶网络结构。化学作用力结果表明,在85 ℃加热1 min后,鱼糜凝胶的疏水相互作用和二硫键含量显著增加(P < 0.05),促进了肌原纤维蛋白的交联和聚集。综上所述,该研究可为PFMH技术在鱼糜制品加工中的应用提供理论参考。

       

      Abstract: This study aims to explore the effects of precision feedback microwave heating (PFMH) on the physicochemical properties of myofibrillar proteins (MPs) of Nemipterus virgatus. The MPs were collected from the Nemipterus virgatus as the research subject. Traditional water bath heating (40 ℃ for 30 min, and 90 ℃ for 20 min) was taken as the control. A systematic investigation was also made on the impacts of PFMH on the protein's turbidity, surface hydrophobicity, fluorescence intensity, ultraviolet (UV) absorbance thermal stability, gel electrophoresis patterns, surface morphology, and surimi gel chemical interactions under various temperatures and heating durations. Results showed that the turbidity and surface hydrophobicity of MPs significantly increased after PFMH treatment, compared with the control group. Both increases also indicated protein aggregation and denaturation, which were critical to understanding the variations in the internal structure of the protein. Specifically, the turbidity of MPs reached 0.78 when heated under S85A conditions, which was an increase of 129.41%, compared with the control group (0.34). Meanwhile, the surface hydrophobicity increased to 177.45 μg, representing a 52.51% increase, compared with the control group (116.35 μg). As such, the PFMH treatment altered the tertiary structure of the protein. The lowest intensity of fluorescence was at S85A, indicating that the PFMH treatment enhanced intermolecular interactions within the protein. Specifically, the PFMH treatment led to the dynamic fluorescence quenching of protein oxidative aggregates in the excited state, resulting in reduced fluorescence intensity. There was a higher fluorescence intensity of myofibrillar protein treated with PFMH at low temperatures (80 °C for 2 and 3 min), compared with the control. The reason was possibly that the rapid PFMH treatment caused some tryptophan residues to be buried within the MPs molecules. Conversely, the UV absorbance exhibited an upward trend, indicating that the PFMH heating induced the conformational changes in the protein structure. The exposure of more aromatic residues led to more effective UV light. Thermal stability was assessed using differential scanning calorimetry (DSC). The results showed that the PFMH treatment significantly enhanced the thermal stability of MPs. Furthermore, the degradation temperature (Td) of the MPs under S85A conditions reached the maximum of 62.20 ℃, an increase of 13.65%, compared with the control group (54.73 ℃). The enthalpy change (ΔH) decreased from 0.43 J/g in the control group to 0.03 J/g, representing a 93.02% reduction. As such, the PFMH treatment effectively prevented the thermal denaturation and degradation of MPs at elevated temperatures. Gel electrophoresis patterns and atomic force microscopy (AFM) images further revealed the structural changes induced by PFMH treatment. The MPs also unfolded to form a dense gel network structure under the S85A condition. Additionally, the AFM images indicated that the size of MPs aggregates increased, while the quantities decreased after PFMH treatment at 90 °C. Chemical interactions revealed that the maximum content of hydrogen bond was 3.06 g/L after heating at S85A conditions, which was 14.61% higher than that of the control group (2.67 g/L). Meanwhile, the hydrophobic interactions and disulfide bonds increased by 105.60% and 97.80%, respectively. However, the ionic bonds decreased after PFMH treatment, compared with the control group. The cross-linking and aggregation of MPs were promoted to form a more stable and compact protein structure. In conclusion, these findings demonstrated that the PFMH treatment significantly affected the physicochemical properties of MPs in Nemipterus virgatus. The protein denaturation and aggregation also induced the structural changes to enhance the thermal stability and the formation of dense gel networks. The heating processing of surimi products can also offer potential reference data for the future application of PFMH technology.

       

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