Abstract Dairy fouling is a ubiquitous problem in food processing, however, the fouling mechanism is not fully understood and investigations arose mainly from experiments with model systems that contained only whey proteins, typically reconstituted from whey protein isolate powder (WPI). The effect of casein on fouling has been rarely considered despite it is the major component of milk proteins. To fill this gap, whey protein-based model fluids containing different casein concentrations and fixed content of added calcium were prepared, leading to various Casein/WPI mass ratios. The effect of Casein/WPI on β-lactoglobulin (BLG) denaturation at molecular level and subsequent fouling behavior in the pilot-scale plate heat exchanger during pasteurization treatment was investigated. It was shown that Casein/WPI significantly affects the fouling behavior: at low Casein/WPI, fouling mass dropped dramatically until a minimum value was reached located at Casein/WPI of 0.2. While at higher Casein/WPI, fouling mass increased with elevated Casein/WPI. Element mapping of the fouling layer also reveals that different structures and fouling mechanisms occur depending on Casein/WPI ratio. Finally, it was established that contrary to WPI solutions, BLG thermal denaturation is poorly correlated to decrease/extent of fouling for casein protein-based solutions showing that the presence of casein deeply modifies mineral and protein interactions and fouling build-up.

中文翻译：

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酪蛋白/乳清比例对乳清蛋白热变性和板式换热器随后结垢的影响

摘要 乳制品污染是食品加工中普遍存在的问题，然而，污染机制尚不完全清楚，研究主要来自仅包含乳清蛋白的模型系统的实验，通常由乳清蛋白分离粉 (WPI) 重构。尽管酪蛋白是牛奶蛋白质的主要成分，但很少考虑它对结垢的影响。为了填补这一空白，制备了含有不同酪蛋白浓度和固定添加钙含量的基于乳清蛋白的模型流体，从而产生不同的酪蛋白/WPI 质量比。研究了酪蛋白/WPI 在分子水平上对 β-乳球蛋白 (BLG) 变性的影响以及随后在巴氏杀菌处理过程中中试规模板式换热器中的结垢行为。结果表明，酪蛋白/WPI 显着影响结垢行为：在低酪蛋白/WPI 下，结垢质量急剧下降，直到在酪蛋白/WPI 为 0.2 时达到最小值。而在较高的酪蛋白/WPI 下，污垢质量随着酪蛋白/WPI 的升高而增加。污垢层的元素映射还表明，根据酪蛋白/WPI 比率会出现不同的结构和污垢机制。最后，已确定与 WPI 解决方案相反，BLG 热变性与基于酪蛋白的解决方案的污垢减少/程度的相关性较差，表明酪蛋白的存在深度改变了矿物质和蛋白质的相互作用以及污垢积聚。污垢质量随着酪蛋白/WPI 升高而增加。污垢层的元素映射还表明，根据酪蛋白/WPI 比率会出现不同的结构和污垢机制。最后，已确定与 WPI 解决方案相反，BLG 热变性与基于酪蛋白的解决方案的污垢减少/程度的相关性较差，表明酪蛋白的存在深度改变了矿物质和蛋白质的相互作用以及污垢积聚。污垢质量随着酪蛋白/WPI 升高而增加。污垢层的元素映射还表明，根据酪蛋白/WPI 比率会出现不同的结构和污垢机制。最后，已确定与 WPI 解决方案相反，BLG 热变性与基于酪蛋白的解决方案的污垢减少/程度的相关性较差，表明酪蛋白的存在深度改变了矿物质和蛋白质的相互作用以及污垢积聚。