Quality Evaluation of Skimmed Milk Treated with Ultra-high Pressure Jet Using Fast Gas Chromatography-Based Electronic Nose

This study explored the impact of ultra-high pressure jet (UHPJ) treatment on the quality of fresh skimmed milk. After UHPJ treatment at pressures ranging from 100 to 300 MPa, the changes in the color, odor and overall flavor of skimmed milk were detected by using electronic eye, electronic nose and sensory evaluation. The results showed that the main color number of skimmed milk was white 4095, constituting 46.80%-53.83%. A total of 42 volatile flavor components such as esters, ketones, and aldehydes were detected by electronic nose. The majority of the flavor components exhibited milky, fruity, roasted, and grassy aromas. Principal component analysis (PCA) revealed that the flavor of samples treated at 300 MPa differed greatly from that of other treated samples. Sensory evaluation indicated that among the flavor attributes evaluated, milky aroma and sweetness were prominent, and there were considerable differences between different samples in terms of sweetness, peptone-like, rusty, burnt and bland flavors. Samples treated at 250 and 300 MPa generated sulfide compounds such as dimethyl sulfide that significantly enhanced the burnt and peptone-like flavors of skimmed milk. In conclusion, UHPJ treatment with 200 MPa can better retain the flavor components in skimmed milk and consequently maintain the flavor of raw milk.