Hydrothermal treatments enhance the solubility and antioxidant characteristics of dietary fiber from asparagus by-products

摘要

Asparagus by-products were submitted to hydrothermal treatments to improve their solubility and antioxidant capacity. Four severity conditions were applied (logR(o) 3.05, 3.64, 4.23, 4.82) and two fractions were isolated from each treatment. The solid fibrous residues were enriched in cellulose, and depleted of hemicelluloses and phenolics. Their antioxidant activities were higher than those presented for asparagus bioactive fibers (81-154 vs 21-26 mmol Trolox/Kg) and did not correlate with phenol content. The soluble liquors were rich in phenolics and also contained changeable amounts of mono-, oligo-, and polysaccharides as a function of severity. The majority of the released oligosaccharides (xylooligosaccharides) are considered as prebiotic and their percentage could be optimized by modifying hydrothermal treatment conditions. This fraction presented very high antioxidant activity (131-232 mmol Trolox/Kg), and had a moderate correlation with phenols. Melanoidins are suggested to be present in both fractions. A new fiber fraction with potential prebiotic activity and high antioxidant activity has been obtained from asparagus by-products. Its high solubility in water and a pleasant flavor broaden its applications in food formulations. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.