Utilization of a resonant cavity for characterization of single in-shell peanuts

Authors: Lewis, Micah; Trabelsi, Samir; Bennett, Rebecca; Chamberlin, Kelly

Submitted to: Journal of Food Measurement and Characterization
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2021
Publication Date: 4/13/2024
Citation: Lewis, M.A., Trabelsi, S., Bennett, R., Chamberlin, K.D. 2024. Utilization of a resonant cavity for characterization of single in-shell peanuts. Food Analytical Methods, 17,855-866. https://doi.org/10.1007/s12161-024-02620-x.
DOI: https://doi.org/10.1007/s12161-024-02620-x

Interpretive Summary: After peanuts are harvested, they go through several post-harvest procedures to determine quality. Such determinations establish the grade of the peanuts and the amount the farmer will receive for the crop. Examples of parameters used to determine the grade of the peanuts include moisture content, meat content, and foreign material. These parameters are usually determined on bulk samples weighing more than 1.5 kg, and the resulting values are averages of peanuts within the bulk sample. Such processes are destructive and lack provision for assessment of single, in-shell peanuts (peanut pods). Therefore, single in-shell peanuts were characterized using a resonant cavity connected to a vector network analyzer (VNA). Measurements for over 300 individual peanut pods were performed at microwave frequencies (approximately 4 GHz) at room temperature, 22 °C. The peanuts were divided into seven categories based on custom fillings provided to simulate diseased or damaged peanuts. One category, consisting of peanuts left intact, served as the control for the experiment. The other categories consisted of peanuts filled with coffee, cornstarch, and/or a single kernel. Measurements of the various peanut pods within the resonant cavity yielded 14 parameters used to characterize each in-shell peanut. The parameters consisted of microwave properties, dielectric properties, and physical properties. Statistical analysis methods were applied to assess differentiation between the seven categories. With those methods, significant differences between categories were able to be determined with 95% confidence.

Technical Abstract: After peanuts are harvested, they endure routine procedures to assess quality, establishing the grade of the product and the amount that the farmer will be allotted. Moisture content and meat content are examples of parameters determined to assess the grade of the peanuts. Such parameters are assessed for bulk samples usually with mass > 1 kg, and the resulting values are averages of peanuts within the bulk sample. Such processes are destructive and lack provision for assessment of single, in-shell peanuts. Thus, the characterization of single, in-shell peanuts (peanut pods) was investigated. A vector network analyzer (VNA) was used to perform microwave measurements of single, in-shell peanuts within a resonant cavity. Measurements of over 300 peanuts were taken at 22 °C between 3.7 and 4.1 GHz. The peanuts were divided into seven categories based on the custom fillings provided to simulate diseased and damaged peanuts. One category, serving as the control, consisted of peanuts left intact; while the other categories consisted of peanuts filled with coffee, cornstarch, and/or a single kernel. The measurements within the resonant cavity yielded parameters needed to determine the dielectric properties. The resonant-cavity, dielectric, and physical properties yielded 14 parameters to characterize each peanut. Statistical analysis was performed to assess differentiation between the seven categories. Kruskal-Wallis One-Way ANOVA on Ranks, Tukey test, and Dunn’s Method were used to determine which categories were statistically different from each other for each parameter at the 95% confidence interval.