Grape pomace, an undervalued by-product: industrial reutilization within a circular economy vision

Grape is one of the most well-known fruits worldwide, being transformed into distinct food products, one of which is wine. A significantly large portion of grape production is exclusively destined for winemaking which, as an industrial process, produces significant amounts of by-products. Grape pomace is considered the major by-product of winemaking and consists of skins, seeds and stems that are left behind after the stage of grapes’ pressing. According to the Waste Framework Directive (Directive 2008/98/EC) of the European Parliament, “waste prevention should be the first priority of waste management and re-use and material recycling should be preferred to energy recovery from waste”. This review aims to approach the recent advances over the valorization of grape pomace as a value-adding material, exploring its potential uses in the industry. The main methods for this purpose are discussed, including traditional methods (such as distillates production, animal feed, and soil fertilizer), its use as a technological aid in different industrial processes (e.g., adsorption, immobilization, food packaging and cosmetics), its addition in food products, highlighting its potential effects on physicochemical, functional and sensory attributes of these products, and as a raw material for bioenergy production. The large number of strategies that have been employed for the possible use of grape pomace show its high revalorization potential, with studies being conducted on several different food products of different categories, such as dairy, meat, fish and bakery products or even wine itself. The main positive effect of this addition consists the increase of the antioxidant activity of the medium, contributing towards enhanced shelf-life, both microbiologically and physicochemically. Given the fact that a linear production model is not satisfactory for sustainable development and focus has been shifted towards circular models, it appears that grape pomace consists a major value-adding component that can promote such economy schemes, as it can be reutilized in numerous ways across a number of industrial categories, including the winery that it came from. However, this study highlighted also the absence of a comprehensive legislative framework covering the addition of grape pomace in foods, of studies analyzing completely the cost of grape pomace revalorization, and of specific research on green/food-grade extraction methods of valuable compounds from grape pomace.

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