collaborative study on the determination of tryptophan in feedingstuffs

The results are reported of collaborative work carried out at seven laboratories to assess the Miller−1 and Buttery and Soar2 procedures for the determination of tryptophan in soya bean, barley, groundnut, fish meal, a single cell protein and lysozyme. The results obtained by both methods were similar but the variation between laboratories was high and exaggerated by the variation in the recovery of tryptophan added before the hydrolysis stage. It was concluded that the determination of tryptophan in feedingstuffs is still a problem.