Physics and Physical Chemistry of Foods, Wageningen University, Bornse Weilanden 9, Wageningen 6700 AA, the Netherlands; Dairy Science and Technology, Food Quality and Design, Wageningen University, Bornse Weilanden 9, Wageningen 6700 AA, the Netherlands.
Physics and Physical Chemistry of Foods, Wageningen University, Bornse Weilanden 9, Wageningen 6700 AA, the Netherlands.
J Colloid Interface Sci. 2022 Feb;607(Pt 2):1050-1060. doi: 10.1016/j.jcis.2021.09.071. Epub 2021 Sep 20.
The rheology of milk fat, which is strongly related to its functionality, reflects multiscale structural transitions in the colloidal network formed by crystallizing triacylglycerols.
To relate rheology to structure, early stages of milk fat crystallization at 15-22 °C were studied combining different techniques; XRD and microscopy to study structural changes, NMR to quantify the different structures, and rheology to evaluate their effect on macroscopic properties.
Network strength increased with the synchronized formation of micro- and nanostructures. A rheological response was only obtained when these structures became visibly connected on a microscale, and internal transitional changes could be detected with rheology. On the nanoscale, transitions were linked to the formation of specific crystal polymorphs. We quantified the formation of polymorphs commonly found in milk fat (α-2 and β-2) and of two less commonly obtained polymorphs: β-2 and β-2. For the first time, the formation of these polymorphs was quantified and related to the composition of fat. Besides providing insights into the complex phase behavior of milk fat, this study shows that the structural transitions involved can be characterized and quantified by combining XRD with NMR and be detected at an early stage using rheology and microscopy.
牛奶脂肪的流变学与其功能密切相关，反映了由结晶三酰基甘油形成的胶体网络中的多尺度结构转变。
为了将流变学与结构联系起来，在 15-22°C 下结合不同技术研究了牛奶脂肪的早期结晶阶段；X 射线衍射和显微镜用于研究结构变化，NMR 用于定量不同结构，流变学用于评估它们对宏观性质的影响。
网络强度随着微观和纳米结构的同步形成而增加。只有当这些结构在微观尺度上变得可见连接时，才会产生流变学响应，并且可以通过流变学检测到内部过渡变化。在纳米尺度上，转变与特定晶体多晶型的形成有关。我们定量了牛奶脂肪中常见的多晶型（α-2 和 β-2）以及两种不太常见的多晶型（β-2 和 β-2）的形成。首次定量了这些多晶型的形成，并将其与脂肪的组成相关联。除了深入了解牛奶脂肪的复杂相行为外，这项研究还表明，可以通过将 X 射线衍射与 NMR 相结合来表征和定量涉及的结构转变，并使用流变学和显微镜在早期阶段检测到这些转变。
