A method for measuring dielectric relaxation of water by NIR spectroscopy: Applicability and application to measurement of water diffusion coefficient

Abstract

AbstractDeterioration of biomaterial is subject to the interaction between biomolecules and water, which is often of special interest to the realization of long‐term preservation. In previous study, we reported the relationship between dielectric rotational relaxation time and the ν2 + ν3 NIR combination band of water as well as the theory behind it using saccharide solutions as examples and proposed a method accordingly which takes advantages of the infrared microscope to measure the dielectric relaxation time of water in biomaterials. In this work, we examined protein, polypeptide, sugar alcohol and some shelf‐stable vegetables to further discuss its applicability and limit. We also proved that this method can be used for measuring water diffusion coefficient and showed example of how the diffusion coefficient can be used to predict water distribution during drying process at a significantly enhanced spatial resolution relative to other techniques.Practical applicationsMolecular mobility of water determines many properties of biomaterials and can be characterized by different spectroscopies. This paper examined the applicability of a method of calculating the dielectric relaxation time of water using NIR spectrum on different solutions and proved that this method may also be used for calculating the diffusion coefficient of water, a parameter subject to molecular mobility and crucial in the drying process. This paper also provided example of the application of this method in the calculation of water distribution during drying process. The high spatial resolution of infrared microscope relative to other techniques may enable the measurement of water dynamics in biomaterials in a much quicker way and smaller scale.