In early 2017, a wine and grape juice producer in Spain was interested in recovering anthocyanins from their solid waste stream. Anthocyanins are valuable naturally occurring pigments found in blue, purple or red fruits such as grapes and blueberries—including red grape skins and seeds. They also have antioxidant properties and many other positive health effects. Although their status as a food additive continues to be evaluated, anthocyanins are used as colorants in the food, pharmaceuticals and cosmetics industries, as well as in beverages and dairy desserts such as ice cream and sorbets.
The customer’s waste stream resulting from grape juice and wine production contained an abundance of competing organic compounds. To recover the anthocyanins, the first challenge was to find an adsorbent product that could specifically load a consistent amount of the desired anthocyanins without significant irreversible fouling due to the adsorption of other molecules. The second challenge was to elute off the anthocyanin from the adsorbent and achieve a purity level > 70% in the recovered product.
Due to an existing relationship, Purolite began working with a consultant hired by the customer to evaluate different adsorbent technologies, which included Purolite adsorbents as well as products from other suppliers.
Purolite offered two adsorbents to test—a polystyrenic adsorbent, Purosorb™ PAD900 as well as an acrylic adsorbent, Purosorb™ PAD950. It was expected that Purosorb™ PAD950 would perform well because it has a lower hydrophobicity which could help improve selectivity and the elution of the anthocyanins as well as decrease the adsorption of non-desirable organics compounds.
Compared side by side with competitive products, the Purolite product showed significantly higher recovery. The anthocyanin recovery for the competitive products were 50 – 60%, while the recovery rate for Purosorb™ PAD950 was 70 – 80%. Additionally, the elution of PAD950 was easier and did not require an extra step of caustic cleaning as the competitive products did.
After a few months of testing, Purosorb™ PAD950 was chosen as the best option. The customer purchased and installed the adsorbent in the 3rd quarter of 2017 and the system was commissioned soon thereafter. Since then, the recovery of anthocyanins from the customer’s waste has exceeded expectations. They were also pleased that our technical experts were available to answer questions about the product and provide onsite direction to improve their process.
Adsorbent resins have several variable characteristics that determine their effectiveness in different systems. Each system has a different liquid to be treated as well as flow rate and recovery solvent. For these reasons, Purolite produces a wide range of adsorbent products with different characteristics such as specific hydrophobic capacity, pore size and pore volume. They can also have a polystyrenic or acrylic backbone.
If you have any questions regarding adsorbents, or would like more information about this application, please contact your local Purolite technical sales representative.