I see a white substance floating on top of the sulfuric acid after a Kjeldahl digestion. Will this substance affect my results?

If you do the de-fat procedure using ANKOM XT4 filter bags, after you complete the Kjeldahl digestion, there will be a white substance on top of the resulting liquid. This substance is the PTFE coating on the XT4 filter bags. This substance will NOT impact your results. ANKOM no longer recommends defatting in XT4 bags. We recommend that you refer to official methods that describe the defatting process, such as AOAC 985.29.