NIR-based PLS method distinguishes soluble coffee and soluble chicory but not type of soluble coffee when in mixture: confirmation by NMR spectroscopy.

BACKGROUND: Soluble coffee has captivated the attention of consumers mainly because of convenient preparation which saves time and energy to brew the beverage. Soluble coffee is susceptible to food fraud with adulterants such as soluble chicory. RESULTS: We reveal a near-infrared (NIR) spectroscopy-based partial least squares regression (PLS) method for distinguishing and quantifying soluble coffee and soluble chicory percentages in a solid mixture. In addition, we also attempted a NIR-based PLS method to distinguish soluble Arabica coffee, soluble Robusta coffee and soluble chicory in one shot; however, it was realized that NIR with PLS is unable to distinctly recognize soluble Robusta and soluble Arabica when these three components are in a mixture. CONCLUSION: The results reveal limitations of NIR spectroscopy in combination with PLS to distinguish the type of soluble coffee (soluble Arabica and soluble Robusta) when mixed with soluble chicory. In addition, the inability of NIR spectroscopy to distinguish the type of soluble coffee is also confirmed by 1H NMR and 13C NMR spectroscopy. © 2026 Society of Chemical Industry.