S-Sulfonates (R-S-SO3-) are compounds formed by the reaction between the sulfites added to foodstuffs and the disulfide bonds of cystine, peptides, and proteins. The content of S-sulfonates has been determined in raw sausages and burgers (n = 62). The range of variation in the contents of the determined S-sulfonates is very wide and varies between 47 and 267 microg of SO2/g. The degree of formation of S-sulfonates with regard to the determined sulfite (total SO2 + S-sulfonates) is similar in all of the samples and does not seem to be conditioned by the meat compound (chicken or beef) or by the process of elaboration or type of product (burgers or sausages). In grilled burgers (n = 20) significant losses are produced in the levels of the additive in any of its forms. The value for the S-sulfonates is 31 +/- 9.8%, 29 +/- 6.6% corresponding to the free sulfite and a very similar percentage to the total sulfite (free + reversibly bound) 28 +/- 6.7%. It is possible that during the cooking process cleavages of some bound compounds occur, releasing SO2 and reacting to form new adducts.