Mercadé-Prieto Ruben, Rodriguez-Rivera Luis, Chen Xiao Dong
Suzhou Key Laboratory of Green Chemical Engineering, School of Chemical and Environmental Engineering, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou City, Jiangsu 215123, PR China.
Photochem Photobiol Sci. 2017 Nov 8;16(11):1727-1734. doi: 10.1039/c7pp00330g.
Rhodamine B (RhB) is a well known dye extensively used in thermometric studies, either considering the decrease in the fluorescence intensity or the lifetime (τ) with temperature. Lifetime measurements are preferred over intensity ones as they are more robust. In order to expand microscopy thermometry to complex food fluids, the effect of solutes on the τ of RhB was studied using fluorescence lifetime imaging microscopy (FLIM) in a two-photon microscope. Polysaccharides of different molecular weights (glucose, lactose, dextran, maltodextrin, and sodium alginate), as well as whey proteins, were considered as typical model food ingredients. A linear increase in τ with the concentration is observed in most polysaccharides, highlighting that it is not due to an increase in the macroscopic viscosity, but in maltodextrins a Langmuir-like concentration dependence is observed. There are extensive interactions between RhB and whey proteins at small concentrations that quickly increase τ up to saturation at >10 wt% proteins, with τ modelled well using an adsorption Langmuir model. Therefore, the effect of solutes on RhB τ is not related to changes in the macroscopic viscosity. The temperature sensitivity of τ, quantified using apparent activation energies, decreases at high solute contents.
罗丹明B（RhB）是一种广为人知的染料，在温度测量研究中被广泛使用，无论是考虑荧光强度的降低还是寿命（τ）随温度的变化。寿命测量比强度测量更受青睐，因为它们更可靠。为了将显微镜温度测量扩展到复杂的食品流体中，在双光子显微镜中使用荧光寿命成像显微镜（FLIM）研究了溶质对RhB寿命的影响。不同分子量的多糖（葡萄糖、乳糖、右旋糖酐、麦芽糊精和海藻酸钠）以及乳清蛋白被视为典型的模型食品成分。在大多数多糖中观察到τ随浓度呈线性增加，这突出表明这不是由于宏观粘度的增加，而是在麦芽糊精中观察到类似朗缪尔的浓度依赖性。在低浓度下，RhB与乳清蛋白之间存在广泛的相互作用，这种相互作用会迅速将τ提高到>10 wt%蛋白质时达到饱和，使用吸附朗缪尔模型可以很好地模拟τ。因此，溶质对RhB寿命的影响与宏观粘度的变化无关。使用表观活化能量化的τ的温度敏感性在高溶质含量下会降低。
