Objective   The stepwise enzymatic hydrolysis was applied to hydrolyze chicken protein for the preparation of a food flavoring ingredient with improved quality.

  Method  An animal and a compound proteolytic enzyme were used to digest the chicken protein. Free amino acid and peptide contents in the hydrolyzed material were employed as the criteria to initially identify the critical process evaluation parameters based on a single factor Plackett-Burman design. A steepest ascent test was conducted to approximate the maximum response area and arrive at the center point in a response surface experiment. Then, according to the selected indicators for the Box-Behnken experiment, optimized process conditions were determined.

  Result   The selected indicators for the Box-Behnken optimization included the free amino acid and polypeptide contents as well as the flavor scores on the thermal reaction products of the hydrolyzed compounds. The optimal processing conditions were found to include the addition of 0.82% enzymes on the chicken protein substrate, a solid-liquid ratio of 1 ∶ 4.40, and a reaction duration of 7.26 h to achieve an actual composite evaluation score of 88.97 in comparison to the predicted 89.41. The method was deemed reliable.

  Conclusion  The multi-indicator response surface method effectively optimized the enzymatic proteolysis process of chicken protein materials in producing a high quality flavoring ingredient for food applications.