Model of dehydration and assessment of moisture content on onion using EIS

Abstract

Onion is perishable and thereby subject to drying during unrefrigerated storage. Its moisture content is important to ensure optimum quality in storage. To track and analyze the dynamics of natural dehydration in onion and also to assess its moisture content, noninvasive and nondestructive methods are preferred. One of them is known as electrical impedance spectroscopy (or EIS in short). In the first phase of our experiment, we have used EIS, where we apply alternating current with multiple frequency to the object (onion in this case) and generate impedance spectrum which is used to characterize the object. We then develop an equivalent electrical circuit representing onion characteristics using a computer assisted optimization technique that allows us to monitor the response of onion undergoing natural drying for a duration of 3 weeks. The developed electrical model shows better congruence with the impedance data measured experimentally when compared to other conventional models for plant tissue with a mean absolute error of 0.42% and root mean squared error of 0.55%. In the second phase of our experiment, we attempted to find a correlation between the previous impedance data and the actual moisture content of the onions under test (measured by weighing) and developed a mathematical model. This model will provide an alternative tool for assessing the moisture content of onion nondestructively. Our model shows excellent correlation with the ground truth data with a deterministic coefficient of 0.9767, root mean square error of 0.02976 and sum of squared error of 0.01329. Therefore, our two models will offer plant scientists the ability to study the physiological status of onion both qualitatively and quantitatively.

Equivalent Electrical Circuits and Their Use Across Electrochemical Impedance Spectroscopy Application Domains

“…These additional circuit components correspond to the plant cell's vacuolar resistance and its tonoplasts' capacitance. Applications of EIS in plant science [3] include, but are not limited to, root growth estimation, frost hardening capability evaluation, plant-based food quality assessment [117], fruit ripening [118], [119], and (a)biotic stress detection. Variations on the Hayden model are typically applied in studies aiming to characterize some plant properties.…”

“…Unlike many other EIS application domains, the Randles circuit is rarely applied as an out-of-the-box circuit here. In some cases, very simple and interpretable circuits consisting of three components are applied, while in other cases, complex non-interpretable circuits that are capable of modelling the impedance behavior are used [117].…”

Plant Tissue Modelling Using Power-Law Filters

“…More electrical models were used to characterize certain plants such as the Grout Citrus Fruit model, which was proposed to model constituent parts of the orange [ 17 ]. In [ 18 ], a bio-impedance model was proposed to track and analyze the natural dehydration dynamics and properties in onions. In [ 19 ], a Warburg impedance was used to represent the interface between the electrode and the surface of the fruit.…”

A noninvasive method for detecting frozen injuries in potatoes based on electrical impedance spectroscopy

“…Electrical impedance spectroscopy (EIS) is a low cost and noninvasive method and has a potential to characterize agricultural products in vivo (at harvest or storage sites) (Jha et al, 2019; Zhang & Willison, 1992). EIS has been widely used to evaluate bio‐tissues in vivo conditions (Islam, Wahid, Dinh, & Bhowmik, 2019). The impedance of bio‐tissues is defined as Z () = V ( t )/ I ( t ) (1), where V ( t ) is the applied voltage, I ( t ) is the resulting steady‐state current measured, Z () is the impedance, and ω is the angular speed.…”