Re-Evaluation of Selectivity of Malachite Green Test for Presence of Sulfite in Mechanically Deboned Poultry

Abstract

A study was undertaken to determine whether free chlorine or sulfide anions could yield positive results for the malachite green test in meat samples when sulfite was not present. Malachite green solution was added to a mechanically deboned poultry (MDP) sample spiked with either chlorine or sulfide ions. The presence of chlorine in MDP samples at any concentration tested did not yield a positive reaction for the malachite green test. When sulfide ions were introduced into MDP samples, positive results were observed at 40 μg sulfide ion/g MDP and above. Because aqueous solutions of sulfide at the levels mentioned have a relatively high pH, it was necessary to determine whether the pH or the presence of the sulfide ions had caused this positive reaction to the malachite green test. After a comparison of a solution of sulfide, and a solution of a matching pH, it was observed that the sulfide present caused the positive reaction to the malachite green test.

Kinetics and mechanism of oxidation of super-reduced cobalamin and cobinamide species by thiosulfate, sulfite and dithionite

“…S-S bond is much longer (2.02 Å) 64 as compared to the S-O bonds (1.46 Å). 64 To assess S-S bond cleavage, we used a malachite green probe, since cleavage products (viz., sulfite, sulfide or polysulfide) result in a bleaching solution, 65 while thiosulfate and polythionates do not give this reaction. Equal concentrations of malachite green were added to a solution of Cbl(I) (6 × 10 −5 M) after oxidation by a ten-fold excess of thiosulfate at pH 7.2 and of Cbl(II) mixed with an excess of thiosulfate (a control experiment).…”