Effect of different alkalies, temperature, and hydrolysis times on tryptophan determination of pure proteins and of foods

✍ Scribed by Bernardo Lucas; Angela Sotelo

• Publisher: Elsevier Science
• Year: 1980
• Tongue: English
• Weight: 357 KB
• Volume: 109
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(80)90028-7

✦ Synopsis

A comparative study was carried out in order to determine which of the most commonly used alkalies for protein hydrolysis in tryptophan determination gave the best results. Hydrolyses were performed with 2.5 and 4N Ba (OH),, 4 and 1ON NaOH. 5 N NaOH containing 5% SnCI,, and with 4~ LiOH, not previously reported for use. The effect of temperature and hydrolysis time on the measured tryptophan content was also determined. Based on results obtained with lysozyme and with seven high protein preparations 4~ LiOH gave the best results. A temperature of 145°C was selected as the most convenient temperature since maximum tryptophan values were obtained with 4-8 h. The hydrolysis time required was inversely related to the protein content of the preparation. Lysozyme, casein. bovine plasma protein, and dehydrated whole egg gave maximum tryptophan content after 4 h hydrolysis while skimmed milk powder, rice flour, wheat flour. and wild legume flour required 8 h hydrolysis.