Biorefinery of discarded carrot juice to produce carotenoids and fermentation products

Abstract

Discarded carrots are a major food waste that is produced from cultivation to sale. This waste has high humidity, which generates not only economic but also environmental problems, requiring a specific biorefinery for its valorization. The pulp and the juice were separated and received a different treatment. The juice was subjected to a process of separation and purification using several diafiltration cycles (30 kDa) giving rise to a fraction rich in carotenoids (4996.4 μg/g) and a fraction rich in sugars (84.83 ± 3.26 g/L) and nutrients. The carotenoids have potential applications in the food and pharmaceutical industry; therefore, they were formulated through encapsulation with gum Arabic using spray drying and freeze drying. Encapsulation using spray drying was effective as it improved stability in water and reduced degradation by 51.9% compared to unencapsulated carotenoids. The sugar-rich fraction was valorized to obtain lactic acid and ethanol through three types of fermentation: with autochthonous microorganisms, with lactic acid bacteria, and with yeast, resulting in obtaining mostly lactic acid (17.64 ± 1.54 g/L) or ethanol (49.46 ± 0.28 g/L). The addition of 6% (w/v) of NaCl to the medium allowed the production of pure lactic acid with both autochthonous microorganisms and lactic bacteria. Sugar consumption was high (92.4–97.5%) except in cases with autochthonous microorganisms (23.3%) and lactic bacteria (43.8%) where a pH control seems to be necessary for total sugar consumption.