Study on the Stability of Antioxidant Peptides from Safflower Seeds with Different Molecular Weight

Objective: The stability of antioxidant peptide activity of safflower seed protein with different molecular weight was studied. Methods: Using shelled safflower seed meal as experimental material, antioxidant peptides were prepared by compound enzymatic hydrolysis. The scavenging ability of 1-diphenyl-2-trinitrophenylhydrazine (DPPH) free radical, superoxide anion radical (O₂⁻·) and hydroxyl radical (·OH) were used as indexes. The effects of environmental factors such as temperature, pH, food raw materials, metal ions and simulated gastrointestinal digestion on the activity of antioxidant peptides from safflower seeds with different molecular weight were studied. Results: The activities of the protease hydrolysates <3 kDa (SSPH-Ⅰ) and 3~5 kDa (SSPH-Ⅱ) of safflower seeds were significantly higher than those before separation (P<0.05), while the activities of SSPH-Ⅲ (5~10 kDa) and SSPH-Ⅳ (>10 kDa) were significantly lower than those before separation (P<0.05). It was found that the antioxidant activity of SSPH-Ⅰ was more stable and could maintain its activity under the condition of 60 to 121 ℃ and weak acid and weak base of pH 6~8, and the free radical scavenging rate maintenance rate was more than 90%. 10 g/100 mL NaCl, glucose and 0.2 g/100 mL citric acid enhanced the antioxidant activity of SSPH-Ⅰ. The free radical scavenging rate maintenance rate was to about 105%. Sucrose of 10 g/100 mL and preservatives of 0.2 g/100 mL had little effect on the antioxidant activity. The addition of Cu²⁺, Zn²⁺ and K⁺ metal ions significantly decreased the antioxidant stability of SSPH-I and the order of effect was as follows: Cu²⁺>Zn²⁺>K⁺>Mg²⁺>Ca²⁺, was stable after simulated gastrointestinal digestion, and the maintenance rate was 80% (P<0.05). Conclusion: The antioxidant peptides of <3 kDa safflower seed protein showed high activity and stability, which provided theoretical basis for its industrial production and application.