Luzzana U ; Mentasti T ; Moretti VM ; Albertini A ; Valfre F ;

Aquaculture Nutrition vol. 2 (2)   pp. 95-99, 1996

Istituto di Zootecnica, Facolta di Medicina Veterinaria, Universita degli Studi di Milano, via Trentacoste 2, 20134 Milano, Italy

The effect of heat treatment during fish meal processing on amino acid racemization was studied. The hydrolysis-induced racemization rate (R) and the D-isomer content in the sample before hydrolysis (I) were differentiated by means of deuterium labelling and gas chromatography-mass spectrometry (GC-MS) analysis in selected ion monitoring mode. A preliminary experiment on laboratory-made herring meals cooked at 125 degree C for different time intervals showed aspartic acid (Asp) as the only amino acid with significant racemization before hydrolysis. Aspartic acid racemization rate appeared to be a nearly linear function of the duration of thermal treatment (R super(2) = 0.93; P < 0.01). Analyses were carried out on several samples of commercial fish meals from different origin. Low-temperature-dried fish meals had a D-Asp content, expressed as I = 100 [D-isomer concentration before hydrolysis / (D- + L-isomer concentration before hydrolysis)], at less than 1%, while the D-isomer content of high-temperature dried fish meals exceeded 2%. Differences between the two commercial categories were statistically significant (P < 0.001). Further studies are required in order to evaluate the effects of D-Asp in protein of fish feeds and the role of the raw material and processing parameters in inducing amino acid racemization in protein of fish meals

Heating ;  Fish meal processing ;  Amino acids ;  Aspartic acid ;  Proteins ;  Chemical reactions ;  Food technology ;