Abstract: Jinhua ham was processed by traditional processing technology with 60 hind legs weighed 6.2～6.9 kg. Biceps femoris from 5 hams randomly taken at seven key stages, i.e. green ham stage, end of salting, end of sun-drying, middle of aging, end of aging, post-aging-1 and post-aging-2, were used as samples to analyze the changes of TBA value, carbonyl value, conjugated diene value and lipoxygenase activity, while the effects of main influencing factors on the lipoxygenase activity were studied using response surface methodology. Results showed that TBA value reached its highest level at end of sun-drying, carbonyl value and conjugated diene value reached their highest level at end of salting, the changes in the other stages showed insignificant (p>0.05); the lipoxygenase activity reached its highest level of 12.55 U/min.g protein at end of salting from 8.00 U/min.g protein at the green ham stage, then decreased continuously to 4.87 U/min.g protein at post-aging-2; temperature, salt and nitrate contents were the main influencing factors of lipoxygenase activity and interaction effects existed between temperature and salt, nitrate content. The actual activity of lipoxygenase during processing estimated with the gained response surface regression equation and reached the highest level at middle of aging could explain about 20% of the lipid oxidation level. This indicated that lipoxygenase did not take a key role in the lipid oxidation during processing of Jinhua ham; the major cause of lipid oxidation during processing of Jinhua ham was auto-oxidation.

Key words: dry-cured ham, Jinhua ham, lipid oxidation, lipoxygenase