Composição química da cachaça por espectroscopia no infravermelho médio (MIR)

Abstract

Cachaça is a genuinely Brazilian alcoholic drink, with an alcohol content of 38 to 48 °GL. Among the current challenges, it is necessary for the food industry, which seeks precise tools for quality control and to determine its characteristics. This work aimed to determine the quality characteristics of cachaças using the mid-infrared spectrum (MIR) using multivariate calibration. 13 samples of cachaça were used and these were subjected to analyzes of color, pH, volatile acidity (AV), total acidity (AT), fixed acidity (AF), density (D), alcoholic content (TA), dry extract (ES), total phenolics (TF), total esters (ET) and copper (Cu). After physical-chemical analyses, the samples were subjected to diffuse reflectance spectrophotometric measurements using the MIR (Agilent Cary 630 FTIR spectrophotometer) at intervals of 650 to 4000 cm-1, with a resolution of 4 cm-1. All information was acquired using software (Resolutions Pro FTIR). Results reveal that all samples evaluated contain TA between 38-48°GL (%, v:v) and Cu <5mg/L, as recommended by current legislation. Sample C12 (805 mg/100mL) contains the highest concentration of ES (p<0.05). In contrast, sample C4 (12 mg/100mL) contains the lowest concentration of ES (p<0.05). Crystal cachaças have ES concentrations < 15 mg/100mL, except cachaças C5 (304 mg/100mL) and C11 (314 mg/100mL). Additionally, samples of crystal cachaças present a lower TF concentration < 14 mg/100mL, except for cachaças C5 and C11 which presented TF > 110 mg/100mL. Cachaça C5 (267 mg/100mL) contains the highest concentration of ET (p<0.05). In contrast, sample C6 (112 mg/100mL) contains the lowest concentration of ET (p<0.05). Crystal cachaças had ET concentrations < 150 mg/100mL, except for cachaças C5 and C11, which had ET concentrations > 150 mg/100mL. All other samples showed significant differences between their ET concentrations from 116 to 212 mg/100mL ET (p<0.05). Samples C2, C3, C4, C5, C8, C10 and C11 revealed AV concentrations > 150 mg/mL. Only C6 and C7 cachaças presented AV concentrations < 60 mg/mL. In the spectra generated by MIR, alcohols (O-H, 3771-3076 cm-1), alkanes (C-H, 3019-2961cm-1), carbonyl group (esters) (C=O, 1749 1576 cm-1), esters (C-O, 1114-1056 cm-1), esters (C-O, 1056-1000 cm-1) and aromatics (=C-H, 883 825 cm-1). PCA discriminated the samples revealing their similarities and differences. The MIR generated spectra that are related to the composition of the cachaça, highlighting alcohols, esters and aromatics. The similarities and differences between cachaças classified as crystal, rested and aged were identified. This work contributed to a more complete understanding of the application and use of infrared spectroscopy in the assessment of cachaça quality parameters.