Polyphenols in Jabuticaba (Plinia spp.) Peel Flours: Extraction and Comparative Evaluation of FTIR and HPLC for Quantification of Individual Compounds.

Jabuticabas are wild fruits native to Brazil, and their peels, the main residue from jabuticaba processing, contain significant amounts of bioactive compounds, which are mostly phenolics. Conventional methods based on the estimation of total extractable phenolics (TEP-Folin-Ciocalteau) or total monomeric anthocyanins (TMA) have limitations and may not reflect the actual antioxidant potential of these peels. Analytical methods, such as high-performance liquid chromatography (HPLC), are more appropriate for the quantification of specific phenolics, and can be used as a reference for the construction of mathematical models in order to predict the amount of compounds using simple spectroscopic analysis, such as Fourier Transform Infrared Spectroscopy (FTIR). Therefore, the objectives of this study were (i) to evaluate the composition of specific polyphenols in flours prepared from jabuticaba peels and verify their correlation with TEP and TMA results from a previous study, and (ii) to employ FTIR coupled with chemometrics to predict the concentrations of these polyphenols in jabuticaba peel flours (JPFs) using HPLC as a reference method. Cyanidin-3-glucoside (C3G), ellagic acid (EA) and delphinidin-3-glucoside (D3G) were the main polyphenols found in the samples. The C3G contents ranged from 352.33 mg/100 g (S10) to 1008.73 mg/100 g (S22), with a strong correlation to TMA (r = 0.97; p = 0.00) and a moderate correlation to TEP (r = 0.45; p = 0.02). EA contents ranged from 163.65 mg/100 g (S23) to 334.69 mg/100 g (S11), with a moderate to strong correlation to TEP (r = 0.69; p = 0.00). The D3G values ranged from 94.99 mg/100 g (S10) to 203.36 mg/100 g (S5), with strong correlations to TMA (r = 0.91; p = 0.00) and C3G levels (r = 0.92; p = 0.00). The developed partial least squares-PLS models based on FTIR data provided satisfactory predictions of C3G and EA levels, reasonably matching those of HPLC.

Jabuticaba (Plinia sp.) Peel as a Source of Pectin: Characterization and Effect of Different Extraction Methods.

The peel of jabuticaba, a small fruit native to Brazil, has been shown to be a potential source of antioxidants and soluble dietary fibers. In this study, flours prepared from these peels were evaluated as a source of pectin. Different extraction methods were employed: ultrasound (US) extraction followed by low temperature heating (40 °C); in a microwave (MW) without (method 1) or with cellulase (method 2) or hemicellulase (method 3); or in a water bath (method 4). Pectin yields ranged from approximately 18% for methods 1 and 4 up to 22% for enzyme-assisted extractions (methods 2 and 3). Methods that did not employ enzymes resulted in low amounts of methoxyl pectins, as opposed to high amounts of methoxyl pectins obtained after enzyme treatment. Cyanidin-3-O-glucoside (C3G) and ellagic acid were the main phenolic compounds found in jabuticaba peel pectins, with higher C3G levels obtained with enzyme-free extraction (methods 1 and 4). All pectins from jabuticaba peel presented a reddish tone, good emulsifying properties and high swelling capacity. The pectin extracted using US+MW+cellulase (method 2) presented better emulsifying performance (higher values of emulsifying activity and emulsion stability), more effective than commercially available citrus pectin.

FTIR and PLS-regression in the evaluation of bioactive amines, total phenolic compounds and antioxidant potential of dark chocolates.

Cloning techniques are used to improve agronomical traits and answer to the demand for fine chocolate. The objective of this study was to predict the concentrations of bioactive amines, phenolic compounds, and the antioxidant potential of dark monoclonal chocolate from nine fine cocoa varieties by FTIR analysis and conventional techniques. Total phenolic compounds, bioactive amines and antioxidant activity varied significantly among chocolates. The antioxidant activity was also affected by the analytical method (DPPH vs. Rancimat). Chemometric models based on FTIR data provided satisfactory predictions of the concentrations of the amines: spermidine (R2 = 0.92; RMSEP = 0.39; RMSEC = 0.21), tryptamine (R2 = 0.92; RMSEP = 0.41; RMSEC = 0.20), cadaverine (R2 = 0.82; RMSEP = 1.58; RMSEC = 0.75) and tyramine (R2 = 0.87; RMSEP = 1.87; RMSEC = 0.68); as well as phenolic compounds and antioxidant activity by Rancimat® (R2 = 0.98; RMSEP = 0.32; RMSEC = 0.21) and DPPH (R2 = 0.97; RMSEP = 4.05; RMSEC = 1.66). The wavenumbers of amines vibrations are among those that most affected antioxidant prediction models, confirming the contribution of amines to the antioxidant activity of chocolates.

Buriti (Mauritia flexuosa L. f.) fruit by-products flours: Evaluation as source of dietary fibers and natural antioxidants.

Buriti by-products flours were evaluated as sources of dietary fibers and natural antioxidants. All flours presented chemical characteristics that allowed classification as high dietary fiber powders. Presence of pectic polysaccharides, arabinoxylans and xyloglucans was inferred by the neutral monosaccharides profile. Peels and defatted pulp flours are highlighted as those with higher antioxidant potential (total extractable polyphenols and antioxidant activities by DPPH and FRAP) compared to endocarp and manually-produced bran flours. Carotenoids content were also higher in the peels flours. All produced flours showed expressive amounts of total non-extractable proanthocyanidins (NEPA). Buriti peels flours NEPA levels are among the highest values previously described in the literature. Blanching preserved the extractable polyphenols but not carotenoids or NEPA. Technological properties were influenced mainly by the size of the particles. Buriti by-products flours have potential to be used as sources of dietary fiber and natural antioxidants in food.