Paprika powder is a common cooking spice. The bright red color makes paprika powder an ideal natural colorant in seasonings, sauces, confectionary products, processed cheeses, etc. Its quality is directly associated with the presence and proportions of flavoring, coloring, and pungent compounds. Paprika's pungency is primarily attributed to capsaicinoids. Capsaicin accounts for ~71% of the total capsaicinoids in the most pungent paprika varieties [1]. Spiciness is measured using the Scoville Heat Unit (SHU) scale (sweet paprikas <500 SHU, hot paprikas 2500–8000 SHU). The color is determined according to the American Spice Trade Association (ASTA) [2]. In this study, quality parameters including the capsaicin content, ASTA color, SHU, water activity (a_w), and ash content were measured simultaneously in paprika powder samples using near-infrared spectroscopy (NIRS).

Paprika samples were measured using a Metrohm NIR Analyzer. No sample preparation nor solvents were required. All measurements were performed in reflection mode (1000–2250 nm) using the large cup accessory. The samples were measured in rotation to collect spectral data from several areas. Spectral averaging of signals from different spots helped to reduce sample inhomogeneity. Metrohm software was used for all data acquisition and prediction model development.

The obtained NIR spectra of paprika powder (Figure 1) were used to create prediction models for quantification of capsaicin content, ASTA color, SHU, water activity (a_w), and ash content. The quality of the prediction models was evaluated using correlation diagrams (Figures 2–6) which display a very high correlation between the NIR prediction and the reference values. The respective figures of merit (FOM) display the expected precision of a prediction during routine analysis.

This Application Note displays the benefits of analyzing paprika powder with NIR spectroscopy. NIRS allows all the mentioned quality parameters (i.e., capsaicin content, ASTA color, SHU, water activity (a_w), and ash content) to be measured simultaneously in only a few seconds. Measurements performed with NIR spectroscopy do not need any sample preparation nor solvents, unlike other conventional analytical methods (Table 1). This ultimately leads to a reduction in workload and related costs, and also keeps lab personnel safer.