Kinetic modelling of the formation of sulphur-containing flavour components during heat-treatment of milk

Multiresponse modelling was used to construct a mechanistic model for the changes in volatile sulphur components and protein-bound sulphydryl groups in skimmed and semi-skimmed milk, subjected to a broad range of heat-treatments. The model yielded an acceptable fit for all measured components: hydrogen sulphide, methanethiol, dimethyl sulphide, dimethyl disulphide and carbonyl sulphide, and in addition protein-bound masked-SH, free-SH and S-S bonds. However, this acceptable fit was obtained only if the model contained not previously described reactions of carbonyl sulphide and dimethyl sulphide into unknown components X and Y. The model could be used to calculate reference reaction rate constants and activation energies in skimmed milk and 1.5% fat milk with fair accuracy. Constants and energies were different for the two milk types, showing that formation and/or release of volatiles is very product specific. A formation/degradation kinetic model was used to describe the change in cooked flavour. Formation and disappearance of cooked flavour correlated well with that of methanethiol, and activation energies were similar. (c) 2007 Elsevier Ltd. All rights reserved.