What should I do when my Fluid Thioglycollate Broths turn pink all over?
A. Fluid Thioglycollate contains the pH indicator resazurin, which turns pink in the presence of oxygen. It is normal to have a pink layer in the upper 10% of the broth. Often during shipment, the bottle or tubes become agitated and the entire medium turns pink due to dispersion of the small amount of oxygen that may be in the tube. Sometimes just allowing the broth to stand undisturbed for a few hours will settle the pink color/oxygen to just the upper layer. If this is not successful and more than 30% of the media remains pink, then the tubes or bottles should be immersed in a boiling waterbath for about 10 minutes with the caps loosened to drive off the oxygen (ref: Dehydrated Culture Media and Reagents for Microbiology, 10th ed. 1984. Difco Laboratories, Detroit, MI). The caps must be re-tightened while still hot to prevent the re-oxygenation of the media.
A. Fluid Thioglycollate contains the pH indicator resazurin, which turns pink in the presence of oxygen. It is normal to have a pink layer in the upper 10% of the broth. Often during shipment, the bottle or tubes become agitated and the entire medium turns pink due to dispersion of the small amount of oxygen present in the tube. Sometimes just allowing the broth to stand undisturbed for a few hours will settle the pink color/oxygen to just the upper layer. If this is not successful and more than 30% of the media remains pink, then the tubes or bottles should be immersed in a boiling waterbath for about 10 minutes with the caps loosened to drive off the oxygen (ref: Dehydrated Culture Media and Reagents for Microbiology, 10th ed. 1984. Difco Laboratories, Detroit, MI). The caps must be re-tightened while still hot to prevent re-oxygenation of the media.
