A RAPID METHOD FOR DETERMINATION OF TRYPTOPHAN IN FOODS AND FEEDSTUFFS WITH FLUORIMETRIC METHOD
Liu Yuequn, Hu Jian(Shanghai Food Research Institute, Shanghai)
A rapid method for directly determining tryptophan contents in foods and feedstuffs was described. l-5mg dry sample could be completely hydro-lyzed in a teflon tube containing 5N NaOH with 0.5% soluble starch under 145℃ for 4 hours in vacuum (760mmHg). The hydrolysate was then adjusted to neutral with 6N HCL in icebath and diluted by five times with 4M urea solution (pH = 11), and was measured at excitation wavelength 280nm and fluorescence wavelength 368nm. The sensitivity of the method was 5ng /10ml, and the recovery rate of 97-107% were obtained in the range of 1-5 μg/10ml standard tryptophan. The value of a number of foods and feed-stuffs obtained were in agreement with the literatature values.