Dairy industries are interested to know the heat treatment undergone by milk for controlling the quality of drinking milks or in order to control their heating systems. The purpose of this work was to develop a specific and sensitive technique for classification of the heat-treatment a milk had been submitted to, without disposing of the original raw milk. For this purpose, -lactalbumin was chosen as a bioindicator of heat treatment and monoclonal antibodies specific for its native (NAL) or heat-denatured (HDAL) form were raised and used in two inhibition ELISA. ELISA allowed differentiation between raw, pasteurized, UHT and sterilized milks without even having to know the -lactalbumin concentration of the original raw milk. However, this technique was more suitable for intense heat-treatments like UHTtreatment and sterilization because of the heat stability of -lactalbumin.