The effects of electrostatic repulsion (pH6.5) and attraction (pH4.6) between biopolymers on the physicochemical and foam properties of ovalbumin (OVA)/carboxymethylcellulose (CMC) mixtures subjected to mild heat treatment (60–75 °C) were comparatively investigated. It was found that electrostatic binding between OVA and CMC at pH 4.6 resulted in an increase in the peak temperature of thermal denaturation (T) of OVA from 71.3 °C to 74.4 °C, while no significant effect was observed at pH 6.5. Thus, 60 and 65 °C below T were chosen to further investigate the effects of heating on the degree of thermal aggregation, protein conformation and foam properties of OVA/CMC mixtures. Confocal laser scanning microscopy observations and rheological results indicated that electrostatic binding between OVA and CMC at pH 4.6 significantly reduced the degree of protein thermal aggregation, while on the contrary, electrostatic repulsion between proteins and polysaccharides at pH 6.5 promoted OVA thermal aggregation. Raman spectroscopic characterisation indicated that mild heat treatment mainly led to a change in the microenvironment polarity of OVA tyrosine and tryptophan residues, as well as an increase in the content of random coil in the amide III band irrespective of pH. Moreover, after heating at 65 °C for 20 min, The foaming ability of the OVA/CMC mixtures at pH 6.5 and 4.6 increased by approximately 32% and 36% respectively compared to pure OVA. These findings have a positive value for enhancing the heat sterilisation strength of egg white proteins.

中文翻译：

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温和热处理后卵清蛋白-羧甲基纤维素混合物的物理化学和泡沫特性：静电斥力和吸引力的比较

生物聚合物之间的静电斥力（pH6.5）和吸引力（pH4.6）对经过温和热处理（60-75℃）的卵清蛋白（OVA）/羧甲基纤维素（CMC）混合物的物理化学和泡沫性能的影响相对较小调查了。结果发现，在pH 4.6时OVA和CMC之间的静电结合导致OVA的热变性峰值温度(T)从71.3℃升高至74.4℃，而在pH 6.5时没有观察到显着影响。因此，选择低于 T 60 和 65 °C 来进一步研究加热对 OVA/CMC 混合物的热聚集程度、蛋白质构象和泡沫特性的影响。共焦激光扫描显微镜观察和流变结果表明，pH 4.6时OVA和CMC之间的静电结合显着降低了蛋白质热聚集程度，而相反，pH 6.5时蛋白质和多糖之间的静电排斥促进了OVA热聚集。拉曼光谱表征表明，温和热处理主要导致OVA酪氨酸和色氨酸残基的微环境极性发生变化，以及酰胺III带中无规卷曲含量的增加，与pH无关。此外，在65℃加热20分钟后，OVA/CMC混合物在pH 6.5和4.6下的发泡能力与纯OVA相比分别增加了约32%和36%。这些发现对于增强蛋清蛋白的热灭菌强度具有积极的价值。