"RP-HPLC methods were developed using the same column (Symmetry 300 (TM), Waters), which enabled the separation of whey proteins within 22 minutes; furosine was analysed using ion-pair RP-HPLC within eight minutes. Electrophoresis was used as a high-throughput and cost-effective screening method to assess the impact of thermal processes on milk and to distinguish different categories of heat-treated milk samples. Liquid milk samples (n = 128; including seven raw, 33 pasteurized, 71 ESL, and 17 UHT milk samples) were obtained from retail outlets in Austria and analyzed. Only 45% of the analyzed samples designated as ESL milk showed furosine contents < 40mg.100 g(-1) protein as well as acid-soluble beta-Lg contents > 1800mg.L-1 milk, which had been discussed as threshold levels for ESL milk. A further 55% of the analysed ESL milk samples had low acid-soluble beta-Lg (< 500mg.L-1) and high furosine contents (> 40mg.100g(-1) protein), levels comparable to the excessive heat load of UHT milk," wrote H.K. Mayer and colleagues.
The researchers concluded, "Thus, there is an urgent need for an EU regulation to define legal limits for the tolerable heat load of ESL milk as soon as possible."
Mayer and colleagues published their study in Dairy Science & Technology ("RP-HPLC Analysis of Furosine and Acid-soluble Beta-lactoglobulin to Assess the Heat Load of Extended Shelflife Milk Samples in Austria." Dairy Science & Technology, 2010;90(4 Sp. Iss.):413-428).
For additional information, contact H.K. Mayer, University of Nat Resources & Applied Life Science Vienna, Dept. of Food Science & Technology, Division Food Chemical, Gregor Mendel Str 33, A-1180 Vienna, Austria.
From the October 4, 2010, Prepared Foods E-dition