Antioxidant Activity and Stability of Polysaccharide from Banana Flower

Objective: Banana flower polysaccharide was used as raw materials to analyze the antioxidant activity and stability. Methods: Bioactive polysaccharide from banana flower was extracted using hot-water extraction method combining with alcohol-precipitation method. Initially, the chemical composition of banana flower polysaccharide was detected and analyzed. Then, the total antioxidant capacity (T-AOC), as well as DPPH, hydroxyl and superoxide anion radicals scavenging activities were utilized to analyze the antioxidant activity of banana flower polysaccharide in vitro. On this basis, the antioxidant stability of banana flower polysaccharide was evaluated further by simulating different food processing conditions, including light, pH value, temperature, metal ions, common food ingredients, as well as sterilization methods, using the hydroxyl radical scavenging activity as the evaluation index. Results: The extraction yield of banana flower polysaccharide was about 14.56%, and the total sugar content, uronic acid content, protein content, phenolic content and flavonoid content of banana flower polysaccharide were 515.61, 287.88, 53.46, 2.23 and 7.94 mg/g, respectively. The result in this paper showed that polysaccharide obtained from banana flower possessed good reducing power, as well as DPPH and hydroxyl radicals scavenging capacities. The antioxidant property of banana flower polysaccharide was degraded by lighting, but remained stable under strong acidic as well as alkaline conditions. Banana flower polysaccharide had good heat resistance, specially under heating 60~80 ℃ from 2 to 3.5 h, its antioxidant stability was strong. Then, the good antioxidant stability of banana flower polysaccharide was observed in the presence of Na⁺ metal ion, whereas the antioxidant activity of banana flower polysaccharide was decreased with the increasing in the concentration of K⁺, Fe³⁺ and Cu²⁺ metal ions. Additionally, the antioxidant activity of banana flower polysaccharide was improved within the common food ingredients such as citric acid and sodium benzoate, but was decreased under sucrose and glucose as common food ingredients. The sterilization methods had different degrees of adverse effect on the antioxidant activity of banana flower polysaccharide, hence, high pressure sterilization could be used for sterilizing banana flower processing products. Conclusion: Banana flower polysaccharide had good antioxidant activity. The environmental factors including continuous light, Fe³⁺ and Cu²⁺ metal ions, as well as sucrose and glucose as common food ingredients might have the great influence on the antioxidant activity of banana flower polysaccharide. Hence, the direct contact with these environmental factors should be avoided during the processing and storage of banana flower.