Jiamei Wang

Crude lipoxygenase from pig muscle: partial characterization and interactions of temperature, NaCl and pH on its activity.

Crude lipoxygenase (LOX) was extracted from fresh pig bacon belly and studied of partial characteristics. The interactions of temperature, sodium chloride (NaCl) and pH on LOX activity were investigated by response surface methodology (RSM). Kinetic studies indicated that the Michaelis constant (K(m)) and maximum velocity (V(max)) for LOX activity using linoleic acid as substrate were 68 μM and 0.26 U/min at 20°C, respectively. The optimal conditions for this reaction were: substrate concentration 3.47 mM, reaction temperature 39°C and pH ≧9.0. The NaCl critical value for LOX activity was 3.0% (w/w) at 20°C, above which the LOX activity began to decrease. Temperature had significant interactions (p<0.05) with NaCl and pH. The temperature critical value decreased with NaCl content increasing, while increased with pH increasing. These indicated that LOX activity and enzyme-catalyzed lipid oxidation in dry-cured meat products could be regulated by controlling process factors during the processing.

Influence of partial replacement of NaCl with KCl on profiles of volatile compounds in dry-cured bacon during processing

This study investigated the influence of partial substitution of NaCl with KCl on the formation of volatile compounds in bacons during processing using a purge and trap dynamic headspace GC/MS system. Three substitutions were 0% KCl (I), 40% KCl (II), and 70% KCl (III). The profiles of the volatile compounds significantly changed during processing, particularly during the drying/ripening. At the end of process, the bacons from substitution III formed significantly higher levels of lipid-derived volatiles, such as straight chain aldehydes, hydrocarbons than bacons from substitution I and II, whereas the latter formed higher levels of volatiles from amino acid degradation such as 3-methylbutanal. There were very few differences in volatile formation between 0% and 40% KCl application. These results suggest that K(+) substitution of Na(+) by more than 40% may significantly change profiles of volatiles in finished dry-cured bacons and therefore would result in changes in the product aroma and/or flavour.

Proteolysis and sensory properties of dry-cured bacon as affected by the partial substitution of sodium chloride with potassium chloride

Quadriceps femoris muscle samples (48) from 24 pigs were processed into dry-cured bacon. This study investigated the influence of partial substitution of sodium chloride (NaCl) with potassium chloride (KCl) on proteolysis and sensory properties of dry-cured bacon. Three salt treatments were considered, namely, I (100% NaCl), II (60% NaCl, 40% KCl), and III (30% NaCl, 70% KCl). No significant differences were observed among treatments in the proteolysis, which was reflected by SDS-PAGE, proteolysis index, amino acid nitrogen, and peptide nitrogen contents. Furthermore, there were no significant differences in the moisture content between control and treatment II, whereas the moisture content in treatment III was significantly higher (p<0.05) in comparison with control (treatment I). The sensory analysis indicated that it was possible to reduce NaCl by 40% without adverse effects on sensory properties, but 70% replacement of NaCl with KCl resulted in bacon with less hardness and saltiness and higher (p<0.05) juiciness and bitterness.