Upcycling a local by-product from viticulture: application of unripe grape juice as an alternative acidifier in elderflower syrup

Abstract

Juice extracted from unripe grapes during the thinning stage, also named "verjuice", has a very low pH and sour taste, making it a sustainable substitute for acidifying additives in pasteurized preserves, such as elderflower syrup. This traditional beverage is very popular due to its pleasant taste and health-promoting properties, including a high amount of phenolics. In this study, the suitability of verjuice as an acidifier in elderflower syrup was assessed and compared with citric acid, indicated in the label as E330. Chemical characterization, antioxidant activity and sensory characteristics of elderflower syrups were investigated. The product obtained with verjuice exhibited higher antioxidant activity compared to the one acidified with citric acid, despite having the same total polyphenol amount. Sensory tests indicated no significant difference in the overall liking between citric acid and verjuice acidified syrups, even though they were recognizably different. In conclusion, verjuice can be used as an acidifying ingredient in elderflower processing, with benefits regarding the reuse of an agrifood side product thereby lowering waste, creating new value from regional products, and allowing to obtain a „clean label”.