Department of Food Science and Technology, The Ohio State University, Columbus 43210-1007.
Department of Food Science and Technology, The Ohio State University, Columbus 43210-1007.
J Dairy Sci. 2021 Jun;104(6):6449-6462. doi: 10.3168/jds.2020-19690. Epub 2021 Mar 25.
Anthocyanins (ACN) are pigments with vivid colors, but their application as food colorants is restricted by their limited stability and color expression. Anthocyanins exhibit higher stability in dairy systems than in buffers at similar pH, suggesting that pigments may be able to interact with dairy components such as proteins, resulting in improved performance as colorants. Our objective was to determine the type of interaction between whey proteins (WP) and ACN leading to color enhancements and to determine the role of the ACN chemical structure in this interaction. Model solutions colored with semipurified pigments from sources with different ACN profiles (Berberis boliviana, grape skin, purple corn, black carrot, and red cabbage) were mixed with different concentrations of whey protein isolate (WPI) in pH 3 buffer. Absorption spectra of these solutions were acquired using an absorbance microplate reader, and color parameters were calculated from spectral data. Isolated ACN 3-glucosides were used to determine the role of the aglycone structure in the WP-ACN interaction using visible and fluorescence spectroscopy. In silico modeling was used to visualize potential differences in the interaction between β-lactoglobulin and ACN. Addition of WPI resulted in hyperchromic shifts at the wavelength of maximum absorption in the visible range (λ) of up to 19%, and a significant increase in tinctorial strength for all ACN sources (ΔE > 5). Moreover, ACN acylation did not seem to play a significant role in the WP-ACN interaction. When using isolated ACN, WPI addition resulted in hyperchromic shifts at the λ only for methoxylated ACN such as petunidin-3-glucoside (up to 24%), and malvidin-3-glucoside (up to 97%). The bimolecular quenching constant values (K > 10Ms) strongly suggested that the predominant type of quenching interaction was static. Analysis of enthalpy, entropy, and Gibbs free energy showed that this binding was spontaneous; depending on the chemical structure of the ACN, the predominant binding forces could be hydrophobic interactions or hydrogen bonding. Modeling suggested that methoxylations in the B ring of the aglycon structure promoted interactions with electron acceptor amino acids. Overall, WP could be used to enhance the tinctorial strength of select ACN depending on their structural characteristics. Therefore, ACN source selection may play a key role for specific applications in dairy products.
花色苷（ACN）是具有鲜艳颜色的色素，但由于其稳定性和颜色表达有限，其作为食品着色剂的应用受到限制。花色苷在与 pH 相似的缓冲液中的稳定性低于乳制品系统，这表明色素可能能够与乳制品成分（如蛋白质）相互作用，从而改善作为着色剂的性能。我们的目标是确定乳清蛋白（WP）与 ACN 之间导致颜色增强的相互作用类型，并确定 ACN 化学结构在这种相互作用中的作用。用来自不同 ACN 谱的半纯化色素（Bolivian 小檗、葡萄皮、紫玉米、黑胡萝卜和红甘蓝）给模型溶液染色，然后将其与不同浓度的乳清蛋白分离物（WPI）在 pH 3 缓冲液中混合。使用吸光度微孔板读数器获取这些溶液的吸收光谱，并从光谱数据中计算颜色参数。使用可见和荧光光谱法，使用分离的 ACN 3-葡萄糖苷来确定糖苷配基结构在 WP-ACN 相互作用中的作用。使用计算机模拟来可视化β-乳球蛋白和 ACN 之间相互作用的潜在差异。添加 WPI 会导致在可见范围内（λ）最大吸收波长处的增色位移高达 19%，并且所有 ACN 来源的比色强度显著增加（ΔE > 5）。此外，ACN 酰化似乎在 WP-ACN 相互作用中不起重要作用。当使用分离的 ACN 时，只有添加 WPI 会导致甲氧基化 ACN（如花色素-3-葡萄糖苷（高达 24%）和矢车菊素-3-葡萄糖苷（高达 97%））在 λ 处发生增色位移。双分子猝灭常数（K > 10Ms）值强烈表明，主要的猝灭相互作用类型是静态的。焓、熵和吉布斯自由能的分析表明，这种结合是自发的；取决于 ACN 的化学结构，主要的结合力可能是疏水相互作用或氢键。建模表明，糖苷配基结构 B 环中的甲氧基化促进了与电子接受氨基酸的相互作用。总的来说，WP 可以根据 ACN 的结构特征增强某些 ACN 的比色强度。因此，ACN 来源的选择可能在乳制品中的特定应用中发挥关键作用。
