The effect ofb-lactoglobulin encapsulation in sodium bis (2-ethylhexyl) sulfosuccinate reverse micelles on the envi-ronment of protein and on Trp was analysed at different water contents (x0).CDdataunderlined thedistortionof the b-sheet and a less constrained tertiary structure as the x0 increased, in agreement with a concomitant red shift and a decrease in the signal intensity obtained in steady-state fluorescence measurements.