Abstract:

Fresh papaya pulp was quick-frozen by liquid immersion freezing or in an ultra-low temperature freezer both
at －40 ℃ to evaluate the effects of the quick-freezing methods on the stability of enzymes in frozen papaya pulp. The
corresponding freezing curves were plotted. Meanwhile, changes in the activities of papain, chymopapain and lipase
in papaya pulp quick-frozen by the two methods were analyzed during storage at －18 ℃. The results showed that the
internal temperature of papaya pulp quick-frozen by liquid immersion freezing passed through the zone of maximum ice
crystal formation 8.2 times than that observed with air convection freezing. The quick-freezing rate significantly affected
preservation of enzyme activities in papaya pulp during frozen storage. The investigated enzyme activities in liquid
immersion frozen papaya pulp were retained well for 90 d at －18 ℃.

Key words: quick-freezing method, papaya pulp, freezing, functional enzymes, stability