In this study, lupin proteins were extracted from lupin seeds by two different methods, namely, micellization and alkali dissolution followed by acid precipitation, and their physicochemical properties were evaluated. The molecular mass distribution of lupin proteins was mainly in the range of 18–90 kDa and consisted of proteins with various molecular masses. The total amino acid content of lupin proteins extracted by sequential alkali dissolution and acid precipitation (66.2%) was significantly higher (P < 0.05) than that obtained by micellization (27.8%). The isoelectric point (pI) of lupin proteins extracted by the two extraction methods was close to 5.0. The water-holding capacity of lupin protein extracted by micellization was significantly higher (P < 0.05) than that obtained by alkali dissolution followed by acid precipitation, but there was no significant difference (P > 0.05) in oil-holding capacity between the two methods. The foaming capacity of lupin protein extracted by sequential alkali dissolution and acid precipitation decreased significantly at pH 2.0–6.0, and was the lowest at pH 6.0, and the trend of foam stability was similar to that of foaming capacity. However, pH had no significant effect (P > 0.05) on the foaming ability of lupin protein extracted by micellization. The emulsifying capacity of lupin protein extracted by micellization was the lowest at pH 4.0, and then increased with the increase of pH. The emulsifying capacity of lupin proteins extracted by the two extraction methods was the highest at pH 10.0. The solubility of lupin protein extracted by alkali dissolution followed by acid precipitation was the lowest at pH 4.0, and increased rapidly with the increase of pH from 4.0 to 10.0. The solubility of lupin protein extracted by micellization increased with the increase of pH from 2.0 to 10.0. The results of this study can provide theoretical and technical support for the development and application of lupin proteins in the food industry.

In this study, the stability of cow’s milk with fat replacement by soybean oil bodies (SOB) was investigated under different environmental conditions. Moreover, the effect of replacing milk fat with SOB or anhydrous milk fat (AMF) on the stability of milk stability and yogurt quality was evaluated. The results showed that the particle sizes of milk with fat replacement and raw milk were larger at pH 2.0 and 4.0 than at other pH values. The particle size of SOB milk was significantly higher than those of AMF milk and raw milk at pH 2.0–10.0 (P < 0.05). At NaCl concentrations ranging from 0 to 500 mmol/L except for 200 mmol/L, significantly higher particle sizes were observed for SOB milk than AMF milk (P < 0.05). However, all three milks were stable without droplet aggregation. Under different heat treatments, they were very stable. After 6 h of fermentation, SOB milk reached the ideal pH (about 4.5) of yogurt, while a longer fermentation period was required for AMF milk and raw milk. The viscosity of fermented SOB milk was significantly higher than those of fermented AMF and raw milk (P < 0.05), but they had similar good sensory and texture properties. This study can provide a reference for the application of soybean oil bodies as a substitute for milk fat in dairy product processing.