Tryptophan content of foods and feeds. Conditions for a reliable quantitation.

A procedure for the quantitative determination of tryptophan from complex material was developed. It involved the hydrolysis of samples in the presence of baryta. Data were presented, revealing its quantitativeness and pointing out its efficiency when it was compared with diverse methods developed by other laboratories as a part of collaborative studies. The influence of the way of treating and heating of (sample+baryta) mixture upon tryptophan recovery was also investigated. The placement of (sample+baryta) mixture in an autoclave, when water was boiling, or the careful deaeration of the mixture when it was heated in an oven was essential for quantitative results. These specific conditions can be explained by differences of the protein solvatation, related to the way by which the (sample+baryta) mixture was heated.