Farinhas de casca de jabuticaba: caracterização, avaliação do potencial como fonte de pectina, estudo da interação fibras–polifenóis e predição de compostos por espectroscopia FTIR

Abstract

Jabuticaba (Plinia sp.) is a fruit native to Brazil, whose pulp is consumed fresh or in the form of jams, drinks and desserts. Their dark purple to black peels are usually discarded. Jabuticaba peel flours were produced as a strategy to use and conserve this residue, which is rich in dietary fiber and bioactive compounds. The general objectives of this study were to produce and characterize jabuticaba peel flours (JPF), aiming at the use and conservation of this residue rich in dietary fiber and bioactive compounds. JPF were produced from twenty-eight lots of jabuticabas from different origins. Characterization was performed by conventional techniques and by Fourier transform infrared spectroscopy (FTIR). The tests performed were proximate composition; soluble and insoluble dietary fiber; total contents of anthocyanins, carotenoids, extractable and non-extractable phenolics; and cyanidin-3-glycoside, delphinidin-3-glycoside and ellagic acid contents. Partial least squares (PLS) regression models, employing FTIR data, were constructed to predict the concentration of compounds. Pectins were obtained from jabuticaba peel flour by ultrasound-assisted extraction and heating at low temperature (about 40 °C) by microwave, with and without the aid of enzymes, and also by a water bath. Interactions between extractable polyphenols from jabuticaba peel flour with total dietary fiber and pectin extracted from the flour itself, in addition to commercial cellulose, were investigated in simulated digestion. High variability was observed in the composition of jabuticaba peels. The PLS models satisfactorily predicted the concentration of fibers, phenolics and total anthocyanins, cyanidin-3-glucoside, delphinidin-3-glucoside and ellagic acid, with results similar to conventional analytical methods. Four pectins with good emulsifying performance and high swelling capacity were obtained. After simulated digestion, the free cyanidin-3-glucoside content reduced and the free ellagic acid content increased. All fibers showed increased post-digestion antioxidant capacity, indicating the adsorption of polyphenols.