ANALISIS ADULTERAN KOPI ROBUSTA DAN BUBUK KAKAO PADA KOPI LUWAK MENGGUNAKAN METODE SPEKTROSKOPI ATTENUATED TOTAL REFLECTANCE (ATR) - FOURIER TRANSFORM INFRARED (FTIR) DENGAN PENDEKATAN KEMOMETRIKA

The analysis of adulterated Luwak coffee presents an analytical challenge due to the complexity and spectral similarity with adulterant materials such as Robusta coffee and cocoa powder, which cause overlapping infrared spectra and hinder accurate component identification. This study aims to perform spectral characterization, adulterant identification, and method validation based on FTIR spectroscopy combined with the Multivariate Curve Resolution (MCR) approach. Spectral characterization was carried out by comparing pure and mixed spectra to observe infrared absorption patterns. Adulterant identification was conducted using MCR, while method validation was performed through two parameters, namely linearity and accuracy tests. Based on the FTIR spectral measurements, Luwak coffee showed major absorption peaks at wavenumbers 3500–3300 cm⁻¹ (O–H), 2920–2850 cm⁻¹ (aliphatic C–H), and 1745 cm⁻¹ (C=O ester), while Robusta coffee and cocoa powder exhibited differences in intensity and peak positions, particularly in the regions 1655–1545 cm⁻¹ and 1459–720 cm⁻¹, which are associated with proteins and polyphenols. The MCR analysis successfully separated the spectral profiles of Luwak coffee, Robusta coffee, and cocoa powder. Validation of the semi-quantitative analysis method showed a linear correlation between the loading matrix and the actual concentration, yielding R² values of 0.9714 for Luwak coffee, 0.9482 for Robusta coffee, and 0.9302 for cocoa powder. The accuracy test results showed recovery percentages of 86.29% (Luwak), 102.10% (Robusta), and 87.60% (Cocoa) in single-component samples, and 83.45% (Luwak), 110.01% (Robusta), and 83.73% (Cocoa) in two-component samples. These results indicate that the MCR method is accurate and reliable for multicomponent analysis.