September 16/Vienna, Austria/Science Letter -- According to recent research from Vienna, Austria, "Recent trends to extend the shelflife of pasteurized milk, without the negative flavor normally associated with ultra-high-temperature (UHT) milk, have resulted in the development of extended shelflife (ESL) milk. Acid-soluble beta-lactoglobulin (beta-Lg) and furosine contents were chosen as relevant indicators for heat load of ESL milk products."
"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.