Condições melhoradas de hidrólise de compostos fenólicos ligados em feijão (Phaseolus vulgaris) e jabuticaba (Myrciaria cauliflora)

Abstract

Sequential hydrolysis in alkaline and acidic media is widely used to extract insoluble phenolic compounds from foods, and their conditions determine the extraction yield. This study evaluated the effect of these conditions on the extraction of phenolic compounds from black beans (Phaseolus vulgaris) and jabuticaba (Myrciaria cauliflora). For alkaline hydrolysis, a 2³ factorial design was used, varying the NaOH concentration (2 M, 6 M and 10 M), time (30 min, 495 min and 960 min) and temperature (30 ºC, 45 ºC and 60 ºC). Acid hydrolysis followed a 2² factorial design, with HCl concentration (1.0 M, 6.5 M and 12.0 M) and time (20, 40 and 60 min), setting the temperature at 85 ºC. To describe the binding profiles of insoluble phenolic compounds with the food matrix in black beans, enzymatic hydrolysis was performed with the enzyme CeluMax® and porcine liver esterase. The phenolic compounds were analyzed by high-performance liquid chromatography (HPLC) and the data were treated by ANOVA and Tukey's post-test. In beans, the soluble fraction presented the anthocyanin delphinidin-3-O-glucoside as the main flavonoid (61% of the total), followed by petunidin-3-O-glucoside (20%) and malvidin-3-O-glucoside (10%). After alkaline hydrolysis, the predominant compounds were quercetin-3-O-glucoside and kaempferol-3-O-glucoside, representing 81% of the total content. The highest extraction occurred under conditions 2 (10 M NaOH; 30 min; 30 ºC) and 6 (10 M NaOH; 30 min; 60 ºC), suggesting that high NaOH concentrations associated with short times optimize the process, reducing the time required compared to usual protocols (up to 16 h). Acid hydrolysis allowed the identification of quercetin and kaempferol, but without statistical significance, indicating that extraction can be performed only in the alkaline stage, reducing costs and analysis time.The total content of phenolic compounds after hydrolysis with the CeluMax® enzyme (7.49 g/100 g) was statistically higher than that observed after hydrolysis with pork liver esterase (2.06 g/100 g). These results suggest that, in black beans, insoluble phenolic compounds are mostly linked to cellular structures through beta-glycosidic bonds. In jabuticaba, the anthocyanins cyanidin-3-O-glucoside (70%) and delphinidin-3-O-glucoside (15%) were the predominant compounds in the soluble fraction. After hydrolysis, gallic and ellagic acids were identified, with the former predominating. The most efficient conditions for extraction of phenolic compounds were 7 (2 M NaOH; 960 min; 60 ºC) and 9 (6 M NaOH; 495 min; 45 ºC), demonstrating that high times and temperatures favor the release of the compounds. The most efficient acid hydrolysis occurred in condition 3 (1 M HCl; 60 min), evidencing that lower concentrations of HCl can be used, making the process safer and more 8 sustainable. Furthermore, the possibility of reducing NaOH consumption is advantageous, since dissolutions in high concentrations require heating. Overall, the results indicate that the extraction of phenolic compounds can be optimized with less use of aggressive reagents and reduced times, making the method faster, more economical and environmentally sustainable compared to the methodologies described in the literature.