Bestandsaufnahme zum Vorkommen von Lysinoalanin in milcheiweißhaltigen Lebensmitteln

In 350 commercial samples of food and food ingredients containing milk protein lysinoalanine (LAL) was determined by an improved method. Most of the samples originated from the central European market. LAL was not detectable in fresh milk and pasteurized milk products. Ultra-High-Temperature(UHT)-products (milk, mixed milk and cream) generally did not contain LAL, samples with 60 ppm LAL i.p. (i.p. = in the protein) evidently had been heat treated to a greater extent than usual. In unsweetened evaporated and condensed milk LAL was present at an average of 150 ppm to 250 ppm i.p., whereas in most sweetened condensed milk samples there were only from traces up to 40 ppm LAL. Autoclave sterilized products such as sterilized milk, coffee cream and above all liquid infant milk formulas contained 200 to 1,160 ppm LAL i.p., the higher levels indicating intensive protein damage. The wide range of LAL in these samples was attributed to the diverse heat treatment - both in temperature and time. The production of powdered milk and whey, acid and rennet casein, cheese and cheese products as well as powdered infant milk formulas induced no appreciable LAL formation. LAL-levels in caseinates and coprecipitates diverged widely (0-1,530 ppm LAL i.p.). Conversion of casein curd into caseinate dispersion by carbonate and citrate salts or by a careful and gradual addition of hydroxide led to maximum LAL-levels of 250 ppm i.p. High LAL values resulted from direct addition of hydroxide and temperatures above 100 °C. In numerous food samples containing milk protein as an ingredient (e.g. whipped topping mix, coffee creamer, dessert cream) the degree of LAL varied from 0 to 1,300 ppm i.p.; the high values were attributed to the use of strong alkali treated cascinates. In dietetic protein concentrates (e.g. formula diet) containing granulated casein or whey protein LAL was found in relatively large amounts up to 1,180 ppm i.p. Some whipping agents from partially alkali hydrolyzed milk protein showed extremely high levels of LAL up to 53,000 ppm i.p. and some of the samples contained also free LAL. In all other kinds of food LAL seems to be exclusively present as protein-bound LAL.