Elderberry Concentrate Juice Industrial By-Products Characterization and Valorisation

Abstract

The elderberry juice industry generates by-products that can be valorised as a source of valuable compounds, namely anthocyanins and carbohydrates recovered from pomace and retentate. This work aims to valorise the anthocyanins and carbohydrates present in pomace and retentate, focused on the analysis and characterization of the polysaccharides present and their use for the stability of pink beverages. The present work shows that pomace contains 50% of carbohydrates, in which glucose and xylose are the major constituents, probably arising from cellulose and xyloglucans of cell walls polysaccharides and from the moiety of main anthocyanins present in berry skin. The concentrated juice is rich mainly in free sugars (55%), glucose and fructose, containing also pectic polysaccharides. However, a large amount of compounds are retained in the ultrafiltration membranes of 100 kDa, constituting the retentate, comprising 52% of water insoluble material. The remaining 48% constitutes the water-soluble fraction, composed of 47% of free sugars, mainly fructose (80%), and 14% of polymeric material constituted by 38% of pectic polysaccharides and 44% of anthocyanins. The use of the colourant in the form of a complex pectic polysaccharides-anthocyanins allowed to achieve a higher colour stability than the isolated anthocyanins, over more than 22 days. This property allowed to use the retentate water soluble fraction as a natural colourant ingredient to develop a stable pink tonic water.