Cosun is an international agri-food cooperative with its headquarters in The Netherlands offering solutions for food, feed and biobased products from agricultural crops such as sugar beets and potatoes as well as a wide range of agri-food residues. An example of such a residual stream is sugar beet pulp, which is a major residue from the sugar beet industry and currently mainly valorized as low value feed. In Europe, sugar beet pulp accounts for a production volume of approx. 13 million tons per year. Sugar beet pulp can be ensiled to ensure year-round availability. Given its volume and composition, biorefining of sugar beet pulp can make a substantial contribution to the societal need for sustainable food ingredients as well as biobased products as replacement of conventional fossil products in various industries.
Sugar beet pulp consists mainly of the cell wall polysaccharides (hemi)cellulose and pectin. In this presentation, we will focus on green extraction processes for pectin. Conventionally, pectin is isolated from apple pomace or citrus peels using acid extraction followed by ethanol precipitation and used as a gelling agent in the food industry. Because of environmental aspects, several green alternatives based on aqueous extraction or alternative solvents, such as deep eutectic solvents, have been proposed in the scientific literature. In our study, we have applied two of such processes on (ensiled) sugar beet pulp, i.e. subcritical water extraction and enzymatic pectin extraction. The first process uses hot pressurised water (typically, 100-160C) to open up the cell wall matrix and extract pectin. The second approach uses enzymes such as cellulases to break down the cellulose and thus release pectin from the matrix. The pectin extraction yield was determined as well as the properties of isolated pectin such as purity, molar mass distribution and degree of esterification. Results obtained as well as pros and cons of both extraction approaches will be discussed. Finally, pectin extraction will be positioned as part of a multi-product biorefinery concept for sugar beet pulp potentially yielding several additional products for food and the biobased economy such as arabinose and cellulose.