Carrots are one of the most important tubers grown worldwide, with an annual production of 36 million tons. However, they have a high discard rate that stands at 30%.
Researcher Marta Ramos looked for a solution to this problem in her doctoral thesis, which was directed by Juan García Serna, from the Pressure Process Engineering Group of the University of Valladolid. In her thesis, she explores the valorization of biomass through a biorefinery based on processing the discarded carrots with subcritical water to obtain high-added-value products from waste.
When carrots are processed by the food industry, they generate some pulp and juice by-products that could have a new life after undergoing fractionation processes, such as hydrolysis and ultrafiltration, and stabilization processes, such as spray-drying or freeze-drying.
The recovery of the pulp is based on a process of extraction of the valuable compounds through hydrothermal extraction. This process uses a flow of pressurized 140° C to 180° C water that passes through a reactor with a biomass load, in this case, carrot pulp. The process allows extracting sugars, hemicelluloses, and pectins from the residues, which are compounds of great value for the circular economy.
What can be done with these compounds?
Sugars are an asset that can be transformed into bioethanol, for example, thanks to fermentation with yeast. Meanwhile, hemicellulose could be reused for the manufacture of biofilms for the food industry because of its elasticity, stated Garcia Serna. Finally, pectins present multiple possibilities both in the food industry -where they are used as thickeners and gelling agents- and in the pharmaceutical industry.
Carrot juice residues can also be reused in different ways. The recovery of juice is based on the recovery of its main components, carotenoids and sugars, through ultrafiltration and diafiltration processes, which consist of separating the juice components through the use of membranes, or membranes and water.
Carotenoids are natural pigments that stand out for their antioxidant components and because they help protect the body against cardiovascular diseases. In addition, they have a great application in the food and cosmetic industries. Meanwhile, the sugars obtained can be used to get lactic acid and ethanol through fermentation processes, as stated previously.