Verbesserte Methode zur Lysinoalaninbestimmung in Lebensmitteln

A faster method for the determination of lysinoalanine (LAL) was developed which is universally applicable to all kinds of food products and shows a better ability to separate LAL from interference substances. After appropriate sample preparation and liberation of protein bound LAL by acid hydrolysis the protein hydrolysate is directly neutralized with sodium hydroxide/sodium-citrate-solution. LAL is separated by means of an automatic amino acid analyzer with a special short time program for basic amino acids (sodium citrate buffer pH 4.50/0.61 nNa⁺, 60°C, LAL-elution after 55 min) and detected colorimetrically with ninhydrin. There are no interference problems with high concentrations of amino sugars, fructoselysine and lactuloselysine which occur to a considerable degree particularly in heated milk products. As for LAL-absorption on humin substances, recovery and detection limit, there is a difference between pure protein compounds and samples rich in carbohydrates. Depending on the type of sample matrix detection of 10-40 ppm LAL in protein is possible. Exact quantitative determination is limited to 80 ppm LAL in protein. The lowest amount of LAL that can be detected is 10 ng.