How do I determine the protein (nitrogen) correction for dietary fiber analysis?

Protein determination is performed post the ANKOM TDF Dietary Fiber Analyzer. AOAC methods 991.43, 985.29, and 2001.03 suggest that the Kjeldahl method be used for determining protein content of the residue. 
AOAC methods 2009.01, 2011.25, 2017.16, and 2022.01 describe using either Kjeldahl or combustion methods for determining protein content of the residue. The selection is made by customer preference.
 
To prepare the ANKOM Filter Bags for analysis via Kjeldahl, refer to the TDF Operator’s Manual.
 
To prepare the ANKOM Filter Bags for analysis via combustion methods, cut open the Filter Bag and lightly scrape or brush the particles of sample residue and DE into a small mortar. Grind the mixture with the pestle until homogenous. Take several aliquots of the mixture and run them through your dumas. Use the average protein value of the aliquots for the TDF calculation.
 
Various manufacturer options are available for the nitrogen determination using combustion method. Contact your combustion/dumas manufacturer for further information regarding specific settings and recommendations regarding N2 determinations that involve DE.