Heat accelerates degradation of β-lactoglobulin fibrils at neutral pH
Heat accelerates degradation of β-lactoglobulin fibrils at neutral pH
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DOI：
10.1016/j.foodhyd.2021.107291
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发表时间：
2021-11-16
影响因子：
10.7
通讯作者：
Campanella, Osvaldo
中科院分区：
文献类型：
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作者：
Chen, Da;Pinho, Lorena Silva;Campanella, Osvaldo
与天然蛋白质相比，β-乳球蛋白的纤维状聚集体显示出上级的机械和界面性质。这些性质直接关系到蛋白质的形态和结构。当掺入食品基质中时，在加工过程中，蛋白质原纤维暴露于pH变化和高温条件下，这加速了它们的降解。在本研究中，将中和的β-乳球蛋白原纤维在100摄氏度和121摄氏度下加热不同时间以评估其降解。通过显微镜、散射、光谱学和流变学检查原纤形态、结构和溶液粘度。原子力显微镜显示，蛋白质原纤维的轮廓长度随着100 ℃和121 ℃的加热而逐渐减少，在121 ℃时减少幅度更大。在121 ° C加热5-15分钟观察到增加的原纤维直径（类似于15-25 nm），并且在进一步加热时被破坏。小角X-射线散射表明，在pH值为7的加热，然后在长时间加热减少原纤半径的增加，而原纤长度随加热连续下降。硫磺素T荧光，圆二色性和傅里叶变换红外光谱证实了β-折叠的无规线圈的原纤维在pH 7的热处理过程中降解的转换。纤维的表面疏水性随着加热温度和时间的增加而降低，与非聚集蛋白质含量的增加相一致。当原纤维在100 ℃加热时，原纤维溶液的粘度增加，而在121 ℃时，它们的粘度首先增加然后降低。这些发现意味着在100摄氏度和121摄氏度下加热促进β-乳球蛋白原纤维的降解和解聚，其中聚集作为中间步骤。
Fibrous aggregates of beta-lactoglobulin display superior mechanical and interfacial properties compared to the native protein. These properties directly link to the protein morphology and structure. When incorporated into food matrices, during processing protein fibrils are exposed to pH shifts and high temperature conditions, which accelerate their degradation. In the present study, neutralized beta-lactoglobulin fibrils were heated at 100 degrees C and 121 degrees C for various times to assess their degradation. Fibril morphology, structure, and viscosity in solution were examined by microscopy, scattering, spectroscopy, and rheology. Atomic force microscopy showed the contour length of the protein fibrils decreased gradually with heating at 100 degrees C and 121 degrees C, with greater decreases at 121 degrees C. Increased fibril diameters (similar to 15-25 nm) were observed at 121 degrees C for 5-15 min heating and were disrupted upon further heating. Small-angle x-ray scattering indicated an increase in fibril radius with heating at pH 7 followed by a decrease at prolonged heating, whereas fibril length decreased continuously with heating. Thioflavin T fluorescence, circular dichroism and Fourier transform infrared spectroscopy confirmed the conversion of beta-sheet to random coils as fibrils were degraded during thermal treatment at pH 7. Surface hydrophobicity of fibrils decreased with increase in heating temperature and time, coinciding with an increase in the content of non-aggregated proteins. Viscosity of fibril solutions increased when fibrils were heated at 100 degrees C, whereas at 121 degrees C their viscosity first increased and then decreased. These findings imply heating at 100 degrees C and 121 degrees C facilitates degradation and depolymerisation of beta-lactoglobulin fibrils with aggregation as an intermediate step.