Contactless monitoring of food drying and freezing processes with millimeter waves
This publication appears in: Journal of Food Engineering
Authors: G. Pandey, W. Vandermeiren, V. Matvejev and J. Stiens
Publication Date: Jun. 2018
Millimeter (mm) waves are of interests to monitor the properties of interest (POIs) of food productswhich are opaque for optical and infrared frequencies as they not suffer from all the atomic and intermolecularabsorption processes situated in the latter bands of the Electromagnetic (EM) spectrum. Theyalso offer a higher penetration depth into water containing products than the IR domain. With respect tothe microwave domain, they are less perturbed by ionic contributions of food products, hydration shelleffects and finally they offer a higher spatial resolution compared to microwaves. In the considered mmwavefrequency range, the dipole moment of free water molecules plays a dominant role compared to theother constituents, hence the electromagnetic interaction depends mainly on the amount and phasestate of free water present in food products. These features make mm-wave based sensors an appealingalternative for monitoring and quality control of food processes. However, the effectiveness of mm-wavesensing solutions has not yet been explored in the food industry. In this paper, we present a real time,contactless and non-destructive sensor methodology based on mm-waves to monitor food processes. Ananalytical model is developed to estimate the dielectric properties of food products with varying POIsand to establish the relation between the mm-wave sensor's output and the POIs. A drying and freezingprocess of potato slabs are monitored by measuring the transmission and reflection coefficients bymeans of mm-wave sensors. The theoretical and experimental results are compared and validated. It willbe proven that mm-wave based sensors are a promising real time, contactless and non-destructivemonitoring tool for food quality control.