Optimization of the Extraction Methodology of Grape Pomace Polyphenols for Food Applications

Abstract

This study aims to take advantage of the wine industry by-products and extract bioactive compounds from grape pomace by applying methodologies susceptible to be integrated easily into industrial workflows because of the association with standard instrumentation and facilities, while the main factors affecting the efficiency of the process have been optimized. The sampling consisted of two grape varieties: ‘Touriga Nacional’ and ‘Sousão’. A response surface methodology (RSM) method was used to optimize the extraction conditions based on three independent variables according to the chemical characteristics and stability/lability traits associated with polyphenols; the main bioactive phytochemical in grape pomace: solvent (50%, 70%, and 90% ethanol); temperature (20 °C, 40 °C, and 60 °C); and pH (0.5% HCl, 2% HCl, and 3.5% HCl). The phytochemical profile, as well as the radical scavenging and reducing powers were determined on 27 different samples. The highest yield and antioxidant activity corresponded to extracts obtained at 60 °C using 3.5% HCl and 70% ethanol. The values for total phenols and flavonoids were 44.93 mg of gallic acid equivalents (GAE) and 22.95 mg of catechins equivalents (CE) per gram, respectively. Concerning the evaluation of antioxidant capacity using various assays such as ABTS, DPPH, and FRAP, the results obtained were 0.30, 0.43, and 0.36 mmol of Trolox equivalent antioxidant capacity (TEAC) per gram, correspondingly. The analysis of the extract obtained with the best extraction performance using these parameters via High-Performance Liquid Chromatography–Mass Spectrometry has been also performed, allowing us to identify fourteen (14) compounds, including phenolic acids (n = 3), flavonols (n = 7), and anthocyanins (n = 4). As a result of this process, the best conditions for the production of a natural and environmentally friendly dye, not only avoiding waste but also reusing these by-products, were achieved.

Exploring the Benefits of Nutritional and Chemical Characteristics of Touriga Nacional and Arinto Varieties (Vitis vinifera L.)

“…It is especially acclaimed for its cardiovascular advantages and its role in safeguarding against heart disease. This is in line with findings by other researchers [59][60][61][62][63], who have also identified its presence in wine grapes.…”

“…This compound is frequently emphasized for its capacity to reduce oxidative stress and inflammation. Consistent with studies by Dimitrovska [58], Yang [59], Moutinho [60], and respective research colleagues, who documented delphinidin-3-O-glucoside in various varieties of grape pomace, our findings confirm its presence in GPF samples.…”

Impact of High-Pressure Homogenization on Enhancing the Extractability of Phytochemicals from Agri-Food Residues

“…Notably, extracts derived from roasted coffee beans exhibited higher antioxidant activity compared to other extracts, which was likely due to the higher amount of recovered phenolic compounds. The antioxidant capacities of different agri-food residues, as reported by previous researchers, are in support of our results [34][35][36][37]. Nevertheless, since not all phenolic compounds show antiradical capabilities, the correlation between the polyphenols found in agri-food residues' extracts and their reducing antioxidant capacity (FRAP) must be carefully analyzed and needs further studies.…”

The Effects of Drying and Grinding on the Extraction Efficiency of Polyphenols from Grape Skin: Process Optimization

“…There are several examples of the optimization of polyphenol extraction from grape pomace. For example, Moutinho et al [34] applied the RSM to optimize polyphenol extraction from two grape varieties, taking into consideration the ethanol concentration, extraction temperature, and extraction pH. Ćurko et al [35] optimized the effect of methanol concentration, temperature, and extraction time on the microwave-assisted extraction of different groups of polyphenolic compounds from grape skin pomace, while Putnik et al [36] optimized the different acidities and extraction time effects on flavonoid recovery from grape skin pomace (Vitis vinifera L. cv.…”