Abstract:

As polypenol oxidase (PPO) is a key enzyme for enzymatic browning in burdock, crude PPO was extracted from burdock and characterized enzymlogically to provide experimental evidences for browning control in the production of fresh-cut burdock shreds. Based on this investigation, citric acid in color protection solution, soaking time and bleaching time were optimized using orthogonal array design for maximizing overall sensory quality score of fresh-cut burdock shreds. Results showed that the optimal reaction temperature and pH of burdock PPO were within the ranges of 30 － 40 ℃ and 6.5 － 7.5, respectively. VC presented higher inhibitory effect against this enzyme when compared to sodium bisulfite and EDTA. The optimal color protection was achieved for fresh-cut burdock slices by soaking for 30 min followed by bleaching in a mixed solution containing 0.5% VC, 1.0% citric acid and 0.5% CaCl2. After cooling, fresh-cut burdock slices were shredded and stored at (4 ± 1)℃. Neither change in color nor unfavorable odor was perceived after 14 days of storage.

Key words: burdock, polyphenol oxidase, browning, inhibition, fresh-cut