The worrying and constant increase in the quantities of food and beverage industry by-products and wastes is one of the main factors contributing to global environmental pollution. Since this is a direct consequence of continuous population growth, it is imperative to reduce waste production and keep it under control. Re-purposing agro-industrial wastes, giving them new life and new directions of use, is a good first step in this direction, and, in global food production, vegetables and fruits account for a significant percentage. In this paper, brewery waste, cocoa bean shells, banana and citrus peels and pineapple wastes are examined. These are sources of bioactive molecules such as polyphenols, whose regular intake in the human diet is related to the prevention of various diseases linked to oxidative stress. In order to recover such bioactive compounds using more sustainable methods than conventional extraction, innovative solutions have been evaluated in the past decades. Of particular interest is the use of deep eutectic solvents (DESs) and compressed solvents, associated with green techniques such as microwave-assisted extraction (MAE), ultrasonic-assisted extraction (UAE), pressurized liquid extraction (PLE) and pulsed-electric-field-assisted extraction (PEF). These novel techniques are gaining importance because, in most cases, they allow for optimizing the extraction yield, quality, costs and time.

The increasing pollution and wastage of food and byproducts from agro-industrial production is an increasingly worrying issue. Grape is one of the most diffused fruit crops cultivated, and grape pomace is the main solid byproduct obtained in the winemaking process; interestingly, it is rich in health-beneficial bioactive molecules. In order to recover these molecules, in this work, a green method has been developed, considering two grape pomaces from different cultivars, namely, Petit Verdot and Cabernet Sauvignon. The extraction procedure, as the first step of this process, was carried out with seven selected deep eutectic solvents (DESs). Then, analysis using HPLC-DAD allowed the detection and quantification of eight out of fifteen different phenolic compounds under examination in the extracts produced, including three quercetin glucosides. The evaluation of antioxidant activity, through the DPPH photometric assay, led to the selection of choline chloride/urea 1:2 + 40% water DES extracts as the extracts with the most promising results. Moreover, significant antibacterial activity was also achieved, in particular, for the betaine/lactic acid 1:4 + 40% water DES extract. Further studies will employ this method for numerous cultivars of grape pomaces with the ambitious aim of the production of polyphenol-enriched food and feed supplements.

Reusing waste materials is a sustainable practice to reduce the impact of human activities on the global ecosystem. In particular, agro-industrial waste can be explored as an innovative and green source of beneficial bioactive compounds. For this purpose, seventeen different varieties of wine grape pomace were collected from the Apulia region (Italy) to perform extractions and qualitative–quantitative phenolic profile characterization. To ensure an environmentally friendly extraction process, natural deep eutectic solvents (NADESs) were used as privileged media. After an initial screening, Merlot (MEA) and Sangiovese (SGA) varieties were then selected for extraction with betaine/lactic acid 1:4 (mol/mol) +40% water (w/w) and choline chloride/ascorbic acid 2:1 (mol/mol) +40% water (w/w). They were further investigated by LC-QTOF-MS for a comprehensive metabolomic evaluation. Betaine-based extracts from both cultivars exhibited higher polyphenol contents than choline chloride-based ones: 175.0 and 161.8 mg/kg compared to 59.6 and 40.4 mg/kg. Qualitative antimicrobial assays confirmed the effectiveness of betaine/lactic acid (MEA) and choline chloride/ascorbic acid (SGA) extracts on B. allii and E. coli, respectively, as well as the NADES themselves, even though it is difficult to discriminate the individual effects. Finally, the evaluation of both antioxidant activity and total polyphenol content led to good results for betaine/lactic acid (2.8 and 3.2 mg TEAC/g DW and 0.92 and 0.93 mg GAE/g DW for SGA and MEA, respectively), while the content of ascorbic acid, used as a component of NADES, substantially influenced the relevant obtained results in choline chloride/ascorbic acid samples. These findings support the potential of combining NADES with polyphenols recovered from grape pomace as a promising approach for further optimization and application-oriented investigation.