Abstract: The effects of ultra-high pressure (UHP) treatment (0.1–700 MPa for 10–30 min) on the sensory quality of fresh skim milk were studied. Changes in the light transmittance and average particle size were measured, and changes in the color, odor and taste were detected as well by electronic eyes, electronic nose and electronic tongue, respectively. The results showed that when the pressure was more than 200 MPa, the light transmittance was increased while the average particle size was decreased. In addition, UHP treatment caused changes in the sensory characteristics, and the major color number (3002 and 3018) gradually disappeared and some new color numbers (2183 and 2200) were obtained with the increase of pressure; the major odor component acetone did not change greatly after 10 min treatment in the range of 0.1–700 MPa but decreased when the holding time was 20–30 min, while acetaldehyde disappeared after treatment at 700 MPa for 10 min or at 200 MPa for 20 or 30 min. Meanwhile, some new components such as 2-methylthiophene and ethanol could be observed, with no significant difference (recognition index < 80) among UHP treatments. The intensity of sour, salty and umami taste were weakened, whereas sweetness and bitterness increased after 20–30 min treatment. Therefore, HUP treatment has little effect on the odor of skim milk, but can alter the color, taste, light transmittance and average particle size.

Key words: skim milk, ultra-high pressure, electronic nose, electronic tongue, electronic eyes