Sulfur compounds reduce potato toxins during extrusion cooking

Free sulfhydryl groups in sulfur compounds have been reported to act direct ly on natural toxins to reduce toxicity. The objective of this study was to reduce protease inhibitors and glycoalkaloids in simulated snack foods by the addition of sulfur-containing compounds prior to extrusion. Thiamine, m ethionine, and benzyl disulfide were added to potato flakes at levels of 0. 5% or 1.0% prior to twin-screw extrusion. Total and free thiols and proteas e inhibitors were monitored before and after extrusion by colorimetric assa ys. Potato glycoalkaloids were analyzed by HPLC and by immunoassay. Extrusi on reduced potato flake disulfide bonds; disulfide bonds were higher in sam ples containing added sulfur compounds. Trypsin inhibitor activity was redu ced by as much as 79% by extrusion plus methionine. Extrusion significantly reduced carboxypeptidase inhibitor, but only when benzyl disulfide and 0.5 % methionine were not added. One percent methionine and thiamine resulted i n 60% reductions in glycoalkaloids.