Environmentally friendly procedure for determination of total furfurals in coffees exploiting digital image photometry

Roasting is an essential process in developing the flavor and aroma of coffee beverages, and furfurals are volatile compounds intrinsically correlated with this process, as well as indicators of product quality. Traditional analytical procedures for the determination of furfurals require multiple steps, including extraction, chemical derivation, and preconcentration, and costly equipment (GC or HPLC) are usually demanded. In this study, digital image photometry (DIP) was exploited to determine furfural content in roasted coffee samples as an alternative to traditional labor-intensive techniques. The proposed method was based on the reaction of furfurals with aniline in an acidic-ethanolic medium to form a pink compound (furfurylidenaniline). The reaction was carried out in polypropylene microtubes, the resulting colored product was measured using a smartphone camera, and the images were converted into RGB values using the PhotoMetrix® 1.8 App. The channel G, which corresponds to the complementary color of furfurylidenaniline solution, was taken as the analytical parameter. Analyte extraction in ethanol was exploited to diminish sample background absorption, making feasible the photometric measurements. Under optimal reactional conditions, i.e. 8 % (w/v) aniline solution in 80 % (v/v) acetic acid and 20 % (v/v) ethanol, and a reaction time of 5 min, a linear response within 0.16–1.33 mg L−1 furfural was achieved, described by the equation S = (104.4 ± 0.5) + (29.2 ± 0.7)C (r = 0.998). A limit of detection of 0.05 mg L−1, coefficient of variation of 0.54 % (n = 10), and accurate results in comparison to the HPLC reference method demonstrated the method reliability. The procedure required 100 mg of sample, 2 mL of ethanol, and 40 mg of aniline per determination, resulting in minimal waste generation (2.5 mL). The proposed DIP method is advantageous due to its simplicity, cost-effectiveness, and environmental friendliness, making it attractive for routine quality control and monitoring of the coffee roasting process.

Saiba mais: https://doi.org/10.1016/j.microc.2024.112543