For the UA-oil blend and emulsion, the peaks appeared around 100 μm in the oral and gastric digestion stages of both systems. It suggested that UA and rapeseed oil could combine with oral and gastric components (such as mucin, pepsin and various salt ions) to produce larger particle size, which might be more conducive to the digestion and hydrolysis of oil and the release of UA in the subsequent intestinal digestion stage. After intestinal digestion, the particle size distribution of UA emulsion was more dispersed than that of the two digestion medium of UA and UA-oil blend.