Abstract: The large amount of discarded old stems generated during the process of asparagus harvesting and processing contains rich dietary fiber and active substances, which have certain antioxidant effects and can be used to prepare asparagus old stems with antioxidant activity. Using asparagus stems rich in dietary fiber as raw materials, the content of soluble dietary fiber was increased through cellulase hydrolysis, thereby enhancing its antioxidant activity. By measuring the antioxidant activity and soluble dietary fiber content of asparagus stem liquid before and after enzymatic hydrolysis, single factor and orthogonal optimization experiments were conducted to study the enzymatic hydrolysis time, enzyme addition amount, enzymatic hydrolysis temperature, and determine the optimal enzymatic hydrolysis conditions.The results showed that under the conditions of cellulase addition of 1.0%, enzymolysis time of 1.75 h, and enzymolysis temperature of 50 ℃, the content of soluble dietary fiber increased by 2.9 times, the scavenging capacity of hydroxyl radical increased by 1.69 times, and the content of active substances such as polysaccharides, flavonoids, and saponins increased by 1.39, 1.56, and 1.84 times respectively compared with non enzymolysis.This study can provide a certain theoretical basis for the reuse of old asparagus stems.

Key words: old stem of asparagus, enzymatic hydrolysis, soluble dietary fiber, antioxidant activity