Use of different thermal indices to assess the quality of pasteurized milks

Lactoperoxidase activity and lactulose, furosine and undenatured whey protein contents were determined in Spanish commercial milks labelled as pasteurized (group A) and high-temperature pasteurized (group B), in order to assess their quality. Three samples of group A and all of the samples of group B were lactoperoxidase negative. Most samples of group A had measurable amounts of lactulose, even though their concentrations of undenatured β-lactoglobulin were higher than 2600 mg/l. In general, samples of group B showed higher lactulose and furosine and lower undenatured whey protein contents. High levels of furosine and lactulose accompanied by high levels of undenatured β-lactoglobulin could indicate the addition of milk heated at high temperatures, whereas high levels of furosine and relatively low levels of lactulose may have been due to the presence of reconstituted milk powder.