Tryptophan (Trp) is an essential amino acid for mammals since they cannot synthesise it. Wheat (Triticum aestivum L.) is a major source of dietary Trp, and wheat high in Trp would thus be very beneficial. This study investigated the impact of location and wheat variety on the content of free Trp and mineral nutrients in wheat grain. Four wheat cultivars from national variety tests on wheat with varying protein contents were selected from seven different locations of Sweden representing different climatic zones and soil contents of trace elements. Grain was analysed for Trp content using reversed phase HPLC. Mineral nutrients were analysed using inductively coupled plasma emission spectrometry. Wheat yield and grain content of nutrients and Trp differed significantly between sites. High N content in grain was correlated with a high content of Cu, Fe and S, and also Ca and Mg. However, it was correlated with a low content of K and Na. Trp content was positively correlated with Na and Zn content and negatively correlated with K/Na and K/(Na+Zn) ratio. The varieties differed in Trp content and the two ratios, but there were no significant differences in yields between the varieties at any location. The results indicated salt stress induction of Trp synthesis, which may protect wheat against salt stress and yield losses.

Tryptophan is a precursor for the production of skatole and indole in the large intestine of pigs. Accumulation of these compounds in adipose tissue causes on objectionable odour in meat from entire male pigs. Potential market impact illustrates the importance in developing an accurate method of determining skatole and indole content in adipose tissue. In the present study, a method is described for determination of skatole and indole concentrations by liquid chromatography combined with mass spectrometry (LC-MS) using atmospheric pressure chemical ionization (APCI). The optimization of chromatographic and APCI conditions is reported. This method showed excellent linearity over the concentration range tested (from 10 to 1000 ng mlE-1 of liquefied fat for both skatole and indole).