Abstract: Bromelain is easy to lose its activity during processing and storage. The effects of additives on bromelain activity were studied based on its relative enzyme activity and thermal inactivation kinetics. Meanwhile, different protective strategies for keeping the stability of bromelain during processing and storage were also discussed. The results showed that glucose, fructose and soluble starch could affect the stability of bromelain and fructose was the most powerful affecting factor followed by glucose and soluble starch. The protective mechanisms of metal ion chelators such as EDTA-2Na and sodium polyphosphate, preservatives such as sodium benzoate and reductants such as metabisulfite and β-mercaptoethanol on the activity of bromelain were different, but their application at appropriate amounts could increase bromelain activity. Metabisulfite revealed the best activation effect on bromelain. When the concentration of metabisulfite was 0.05%, the activity of bromelain could significantly improve and the relative activity of bromelain was 3.68. Moreover, the activity of metabisulfite-treated bromelain did not reduce to the original level until 3 days of storage.

Key words: bromelain, sugar, metal ion chelator, preservative, reductant