# Technological Aspects and Potential Cutaneous Application of Wine Industry By-Products
## 2 Opportunity to Obtain Value-Added Products in Circular Economy  
The evident climate changes outline a worrying panorama in several sectors. It is estimated that around 1/3 of agricultural products are wasted before reaching the market, leading to environmental pressure. Although considered comparatively more polluting, regarding greenhouse gases, livestock shows reduced loss and waste. The \"healthy\" food system is represented by, for example, the production of vegetable proteins, using up-to-date agricultural techniques, restricting the pollution of terrestrial and aquatic ecosystems, limiting, or replacing fertilizers, such as nitrogen and phosphorus, and the recycling of water resources. This complex scenario requires complementary initiatives that mitigate part of the environmental effects arising from the agricultural sector and its influence on food and nutrition security [30]. In this context, the education of the population is urgent since once people become aware of the problem of natural adversities, they can actively participate in reducing the pressure on the environment. Food choices (type, quantity, etc.) associated with maintaining people's health and/or reducing the incidence of non-communicable diseases can help achieve environmental sustainability goals by curbing environmental degradation [31]. Viticulture generates various residues from pruning the vine and the fruits used in winemaking (stems, pomace, and grape seed), being a small part of these residues that is reused in value-added products. Existing technologies and the demand for by-products can help to reallocate such wastes [32]. The stalks and stems of pruning vines are considered sources of procyanidins, lignin, cellulose, and hemicellulose. The cellular contents of these wall components depend on the cultivar, winemaking, and destemming processes. The stalks, for example, represent an average of 25% weight of the grape pomace [33]. Additionally, the effluent can be used for other purposes, for example, as a medium for microalgae cultivation [34]. Researchers suggest a sequence of zero-waste alternatives applying circular economy guidelines as follows: (I) the recuperation of higher value compounds, such as polyphenols through \"green\" techniques (biorefinery of economically viable and environmentally correct agro-industrial residues); (II) anaerobic biodegradation for biogas production; and (III) composting of depleted biomass [35] (Figure 1). Obtaining biogas using processed water, initiated during the hydrothermal carbonization of depleted grape pomace, can enable the preservation of energy and physical-chemical properties of hydro charcoal, suggesting its use in adsorbing atmospheric and water pollutants. Polyphenols from wine production residue are natural raw materials that can help to prevent diseases [36]. Studies indicated their beneficial effects, mainly linked to the elimination and transmission of reactive oxygen species through the processes of autoxidation by donating hydrogen atoms or electrons and the synthesis of antioxidant molecules involved in the signaling of enzyme-linked receptors [17; 36]. An overview of recent trials (Table 2) reports a strong antioxidant effect of white and red wine grape pomace extracts mostly performed using in vitro assays [5; 11; 20; 24; 25; 28; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48]. The bioaccessibility and bioavailability potential of phytochemicals of white wine grape pomace (_V. vinifera_ cv. Zalema grapes) depend on the type of by-product, digestion phase, and recovery of phenolic groups. The phenolic compounds in seeds and pomace extract significantly decreased after gastric digestion compared to undigested samples. The total contents of phenolic acids (skin extract) and flavanols (stem and pomace extracts) increased significantly after gastric and intestinal digestion compared to undigested samples. The antioxidant activity of seed and stem extracts increased (-149% and 219%, respectively) after intestinal digestion.