APPLICATION OF THE CLARIFYING REAGENT INDEX AS A HEAT-INDUCED PARAMETER IN COMMERCIAL MILK

The absorbance at 340 nm of transparent modified milk solutions (desig nated as Clarifying Reagent index) from industrially processed samples as well as from milk-resembling systems was measured in order to test the validity of this index for determining the extent of previous hea t treatment. A statistical study (n = 81) of the Clarifying Reagent in dex of different commercial milks was carried out. There was a signifi cant difference (P < 0.001, Student's t test) between three groups of samples: (1) raw and pasteurized milk, (2) UHT-treated milk, and (3) i n-bottle sterilized milk. The Clarifying Reagent index showed signific ant relationships (P < 0.001, Student's t test) with other heat-induce d parameters such as hydroxymethylfurfural formation, loss of availabl e lysine, and free fluorescent intermediary compounds formed by the Ma llard reaction. Between 90 and 140 degrees C, the Clarifying Reagent i ndex of the clarified milk or milk-resembling systems followed zero-or der kinetics as determined by nonlinear regression analysis.