Quantitative Assessment of Coffee Quality Using Microwave Non-Destructive Testing

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.