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

Lactoperoxidase activity and lactulose, furosine and undenatured whey prote in contents were determined in Spanish commercial milks labelled as pasteur ized (group A) and high-temperature pasteurized (group B), in order to asse ss 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 amo unts of lactulose, even though their concentrations of undenatured P-lactog lobulin were higher than 2600 mg/l. In general, samples of group B showed h igher lactulose and furosine and lower undenatured whey protein contents. H igh levels of furosine and lactulose accompanied by high levels of undenatu red P-lactoglobulin could indicate the addition of milk heated at high temp eratures, whereas high levels of furosine and relatively low levels of lact ulose may have been due to the presence of reconstituted milk powder.