Effect of amino acids on the composition and properties of extruded mixtures of wheat flour and glucose

Wheat flour was extruded at 100-120 degrees C with 5% D-glucose or mixtures of 5% D-glucose and 0.5% or 2.0% of L-alanine, L-leucine, L-lysine, L-threonine or L-cysteine. The extent of browning was only moderate, and yellow and red pigments were produced. The odour intensity increased with the addition of either glucose or a mixture of glucose and amino acids; the odour was not significantly intensive according to sensory acceptancy analysis. The odour profile was influenced by the structure of amino acid present in the extruded material. The addition of D-glucose increased the production of furan derivatives, and in lesser degree, of pyrazines in the extruded product. The pyrazine content increased with the addition of amino acids, except cysteine which enhanced the production of sulphur compounds instead of pyrazines. The composition of the pyrazine fraction varied depending on the amino acid added. Pretreatment of D-glucose with an amino acid in aqueous solution affected the composition of volatiles, but it did not significantly enhance the pyrazine production.