The effects of the mass ratio of soybean lecithin to cholesterol, the dosage of Tween-80 and homogenization pressure on the mean particle size and encapsulation efficiency of docosahexaenoic acid (DHA)-rich algae oil liposomes prepared by high-pressure microfluidization were studied. Using a combination of one-factor-at-a-time (OFAT) method and statistical response surface methodology (RSM), the optimal preparation parameters were determined as follows: soy lecithin concentration 20 mg/mL, lecithin to DHA algae oil mass ratio 4:1, lecithin to cholesterol mass ratio 11.9:1, Tween-80 dosage 15% (relative to soy lecithin), homogenization pressure 138 MPa, and five cycles of homogenization. The mean particle size, polydispersity index and encapsulation efficiency of the algal oil liposomes prepared under these conditions were (59.35 ± 3.05) nm, 0.189 ± 0.025, and (94.2 ± 2.9)%, respectively. By transmission electron microscope (TEM), it was observed that the liposomes were spherical and uniformly distributed. Differential scanning calorimetric (DSC) analysis showed that high-pressure microfluidizer homogenization improved the phase transition temperature of the liposomes effectively. Moreover, the liposomes treated with high-pressure microfluidizer homogenization had good physical, storage and oxidation stability.

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.

During storage, milk is prone to different degrees of oxidative degradation of fat with varying storage conditions, which changes the aroma components of milk. In this study, electronic nose based on gas chromatography (GC) and sensory evaluation were used to compare the changes in the composition of volatile flavor compounds and sensory properties of pasteurized whole milk, low-fat milk and skim milk (fat contents of 4, 1.4 and 0 g/100 mL) during storage at different temperatures. The results showed that all three milks maintained good flavor characteristics during storage at 4 ℃. The composition of flavor substances in whole milk was more complex, where 43 volatile compounds were identified, and no obvious stale flavor was perceived. The decreasing order of difficulty of fat oxidation was whole milk > low-fat milk > skim milk. Nonanal, a marker of lipid oxidation, was detected in both skim milk and low-fat milk. Methyl ketones derived from lipid oxidization such as 2-butanone, 2,3-butanedione, 2-hexanone, 2-heptanone and 2-undecanone were detected in skim milk during storage. The results of sensory evaluation were basically consistent with those of electronic nose. The sweetness and milky flavor of whole milk were more prominent, the flavor of low-fat milk was relatively bland, and skim milk tasted slightly bitter after 21 days of storage at 25 ℃. The findings of this study will provide a scientific basis for monitoring the flavor changes of milk products during storage and improving the quality of milk products.