Quantitative Assessment of Coffee Quality Using Microwave Non-Destructive Testing

Mohd Khairil Adzhar Mahmood; Zuhani Ismail Khan; Megat Syahirul Amin Megat Ali; Ahmad Ihsan Mohd Yassin; Norziaton Ismail Khan; Michael Kwan Yeow Tan

doi:10.31436/iiumej.v27i2.3969

Authors

Mohd Khairil Adzhar Mahmood Universiti Teknologi MARA https://orcid.org/0000-0001-7843-8000
Zuhani Ismail Khan Universiti Teknologi MARA https://orcid.org/0000-0003-0496-5056
Megat Syahirul Amin Megat Ali Universiti Teknologi MARA https://orcid.org/0000-0003-2719-7889
Ahmad Ihsan Mohd Yassin Universiti Teknologi MARA https://orcid.org/0000-0001-6419-4797
Norziaton Ismail Khan Universiti Teknologi MARA https://orcid.org/0000-0003-0844-3220
Michael Kwan Yeow Tan KIS Coffee Community https://orcid.org/0009-0006-0786-6837

DOI:

https://doi.org/10.31436/iiumej.v27i2.3969

Keywords:

Specialty coffee, Coffee quality, MNDT, Dielectric permittivity, Multiple regression

Abstract

The geographical origin, processing, roast level, and post-roasting resting time affect coffee quality in multiple ways. The traditional quality assessments in the coffee industry (sensory and chemical analyses) are subject to analysts' biases and are destructive, requiring the coffee to be destroyed to run tests. This analysis uses Microwave Non-Destructive Testing (MNDT) to study the dielectric characteristics of specialty coffee (Coffea arabica L.) associated with roasting and resting period. Coffee beans were roasted to produce light, medium, and dark roasts, and the beans were tested for dielectric properties over 30 days in 5-day intervals. The dielectric permittivity was negatively correlated with the level of roasting (r = -0.590, p = 0.005) and the resting period (r = -0.483, p = 0.027). The multiple linear regression showed strong predictive ability (R = 0.762, Adjusted R² = 0.534), explaining the effects of roasting and resting period, and their combined effect on the coffee's dielectric properties. This study shows, for the first time, how MNDT can be applied to the coffee industry to evaluate and assess coffee quality.

ABSTRAK: Kualiti kopi dipengaruhi oleh pelbagai faktor seperti asal geografi, teknik pemprosesan, tahap panggang dan tempoh rehat selepas dipanggang. Kaedah tradisional bagi penilaian kualiti, termasuk penilaian deria dan analisis kimia, terdedah kepada subjektiviti dan keperluan ujian yang merosakkan sampel. Kajian ini menggunakan kaedah Microwave Non-Destructive Testing (MNDT) bagi menilai sifat dielektrik kopi istimewa (Coffea arabica L.) yang dipengaruhi oleh tahap pemanggangan dan tempoh rehat selepas dipanggang. Sampel kopi ini dipanggang pada tahap terang, sederhana dan gelap, dengan sifat dielektrik yang diukur selama 30 hari pada selang 5 hari. Keputusan menunjukkan korelasi negatif ketara antara kebolehtelapan dielektrik dan kedua-dua tahap panggang (r = -0.590, p = 0.005) dan tempoh rehat (r = -0.483, p = 0.027). Model regresi berganda menunjukkan keupayaan ramalan yang kuat (R = 0.762, R² Terlaras = 0.534), memberi kesan gabungan pemanggangan dan tempoh rehat pada sifat dielektrik. Penemuan ini menggariskan potensi MNDT sebagai alat berskala, bukan invasif bagi penilaian kualiti kopi, menyumbang kepada amalan pemprosesan lebih baik dan kawalan kualiti dalam industri kopi.

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Author Biographies

Mohd Khairil Adzhar Mahmood, Universiti Teknologi MARA

Mohd Khairil Adzhar Mahmood is a Deputy Research Officer at the Microwave Research Institute (MRI), UiTM Shah Alam. He holds a BSc (Hons) and MBA from Universiti Teknologi MARA and is currently pursuing his PhD in Electrical Engineering at the same institution. Previously, he served as an R&D Electrical Engineer at Motorola. His research interests include microwave circuit design, fabrication, measurements, and nanotechnology for microwave applications. Email: khairil833@uitm.edu.my

Zuhani Ismail Khan, Universiti Teknologi MARA

Zuhani Ismail Khan is the Director of MRI, UiTM Shah Alam. She earned her BEng in Electrical and Electronic Engineering from the University of Bradford, UK, and her Master’s and PhD from IIUM and UiTM, respectively. Her research focuses on RF and microwave devices and Microwave Non-Destructive Testing (MNDT). Email: zuhai629@uitm.edu.my

Megat Syahirul Amin Megat Ali, Universiti Teknologi MARA

Megat Syahirul Amin Megat Ali is an Associate Professor at the College of Engineering, UiTM and Deputy Director at MRI. He holds a B.Eng. in Biomedical Engineering (University of Malaya), M.Sc. (University of Surrey), and PhD (UiTM). He is a Chartered Engineer (UK) and a Senior IEEE Member. His expertise spans biomedical signal processing, machine learning, and precision agriculture. Email: megatsyahirul@uitm.edu.my

Ahmad Ihsan Mohd Yassin, Universiti Teknologi MARA

Ihsan Mohd Yassin is an Associate Professor in the College of Engineering, Universiti Teknologi Mara, Shah Alam, Selangor, Malaysia. Received his PhD in Electrical Engineering (Computer Engineering) in 2014. His research interests are in Artificial Intelligence (specifically Machine Learning), System Identification & Optimization. He can be contacted at email: ihsan_yassin@uitm.edu.my.

Norziaton Ismail Khan, Universiti Teknologi MARA

Norziaton Ismail Khan is an Associate Professor at the Faculty of Accountancy, UiTM, with over 20 years of academic experience. She holds a PhD (University of Malaya), Master’s (Curtin University), and Bachelor’s (UiTM). A member of CPA Australia and MIA, her research includes indigenous education, political connections, forensic accounting, and governance. Email: norzi153@uitm.edu.my

Michael Kwan Yeow Tan, KIS Coffee Community

Tan Kwan Yeow is a seasoned coffee expert and educator. Tan’s journey began in Kuala Lumpur and has since made him a prominent figure in the coffee industry. From mastering coffee brewing and barista skills to leading as a head judge at the Philippines AeroPress Coffee Brewing Championship, his expertise is unmatched. Michael’s passion extends beyond competitions. He has been instrumental in organizing record-breaking events, including the Guinness World Record for the largest culinary competition and the Malaysia Book of Records for the largest coffee festival. He can be contacted at email: michael.kiscoffeeco@gmail.com

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