Permittivity measurements for roasted ground coffee versus temperature, bulk density, and moisture content

IF 0.9 4区工程技术 Q4 ENGINEERING, CHEMICAL

Journal of Microwave Power and Electromagnetic Energy Pub Date : 2023-04-03 DOI:10.1080/08327823.2023.2206666

R. Pérez-Campos, J. Fayos-Fernández, J. Monzó-Cabrera

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引用次数: 2

Abstract

Abstract For a large variety of food products, the moisture content can be indirectly determined by measuring their dielectric properties. In the case of coffee, the permittivity knowledge can be applied to determine the moisture content indirectly or for online moisture meters in automatic control of coffee dryers. However, there is little data on the dielectric properties of roasted ground coffee near the 2.45 GHz ISM band. In this contribution, the permittivity was measured versus temperature, bulk density, and moisture content. A resonant technique based on a coaxial microwave cavity was employed to obtain the complex permittivity as a function of those magnitudes near the 2.45 GHz ISM band. In addition, the permittivity of the coffee particle kernel has been estimated from a complex refractive index mixture equation, thus calculating the permittivity of the coffee particle kernel from the permittivity values of the mixture air-coffee (ground coffee) at different bulk densities. The results showed that both dielectric constant and loss factor increase for increasing temperature, bulk density, and moisture content values. Furthermore, expressions fitting the experimental data were provided, thereby facilitating the estimation of the values throughout the studied temperature, bulk density, and moisture content ranges.

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焙炒咖啡粉的介电常数与温度、体积密度和水分含量的关系

摘要对于种类繁多的食品，可以通过测量其介电性能来间接测定其水分含量。在咖啡的情况下，介电常数的知识可以应用于间接确定水分含量或在线水分计在咖啡烘干机的自动控制。然而，在2.45 GHz ISM波段附近，很少有关于烘焙咖啡粉介电特性的数据。在这项贡献中，介电常数与温度，体积密度和水分含量进行了测量。采用基于同轴微波腔的谐振技术，得到了2.45 GHz ISM频段附近复介电常数的函数。此外，通过复折射率混合方程估算了咖啡粒子核的介电常数，从而通过不同体积密度下混合空气-咖啡(磨碎咖啡)的介电常数值计算出咖啡粒子核的介电常数。结果表明，随着温度、容重和含水率的升高，介电常数和损耗因子均增大。此外，还提供了与实验数据拟合的表达式，从而便于在整个研究温度、容重和含水量范围内的值的估计。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Journal of Microwave Power and Electromagnetic Energy ENGINEERING, CHEMICAL-ENGINEERING, ELECTRICAL & ELECTRONIC

CiteScore

2.50

自引率

6.70%

发文量

期刊介绍： The Journal of the Microwave Power Energy (JMPEE) is a quarterly publication of the International Microwave Power Institute (IMPI), aimed to be one of the primary sources of the most reliable information in the arts and sciences of microwave and RF technology. JMPEE provides space to engineers and researchers for presenting papers about non-communication applications of microwave and RF, mostly industrial, scientific, medical and instrumentation. Topics include, but are not limited to: applications in materials science and nanotechnology, characterization of biological tissues, food industry applications, green chemistry, health and therapeutic applications, microwave chemistry, microwave processing of materials, soil remediation, and waste processing.