THE D-AMINO ACID CONTENT OF FOODSTUFFS SUBJECTED TO VARIOUS TECHNOLOGICAL PROCEDURES

• Main Authors: János Csapó, Zsuzsanna Csapó-Kiss, Éva Varga-Visi, László Kametler, Péter Horn
• Format: Article
• Language: English
• Published: Faculty of Agrobitechnical Sciences Osijek 2000-06-01
• Series: Poljoprivreda
• Subjects: D-amino acids; racemisation; heat treatment; bacterial activity
• Online Access: http://poljoprivreda.pfos.hr/upload/publications/36_CSAPO.pdf

D-amino acids occurring in dietary proteins originate as a consequence of technological intervention while basic materials are being prepared for consumption. Foodstuffs are the most significant sources of D-amino acids, as in the process of cooking or during the various processing procedures used in the food industry dietary proteins undergo racemisation to a greater or lesser degree. Food stores are now selling increasing quantities of foods (such as breakfast cereals, baked potatoes, liquid and powdered infant foods, meat substitutes and other supplements) which in some cases contain substantial quantities of D-amino acids, which in turn possess characteristics harmful with respect to digestion and health. Alkali treatment catalyses the racemisation of optically active amino acids. The degree of racemisation undergone varies from protein to protein, but the relative order of the degree of racemisation of the individual amino acids within proteins shows a high level of similarity. The principal factors influencing racemisation are the pH of the medium, heat treatment, the duration of the application of alkaline treatment and the structure of the respective amino acids. D-amino acids formed in the course of treatment with alkalis or heat give rise to a deterioration in quality and reduce the extent to which food thus treated can be used safely. The presence of D-amino acids in proteins leads to a decrease in digestibility and the availability of the other amino acids. This results in a reduction in the quantities of the L-enantiomers of the essential amino acids, as the peptide bonds cannot split in the normal way. Some D-amino acids can exert an isomer-toxic effect and have the capacity to give rise to changes in the biological effect of lysinoalanine.