Abstract: The digestive characteristics of micro/nano-sized colloidal particles (MNCPs) in bighead carp head soup and the effects of processing conditions on them was investigated using an in vitro digestion model. The results showed that salt addition and homogenization did not change the overall trend of MNCPs in the soup during digestion. During gastric digestion, proteins adsorbed to the membrane of MNCPs were degraded, and lipid droplets were released and aggregated for raw, salt-incorporated and homogenized fish soup. During intestinal digestion, the lipid droplets were dispersed and the MNCPs aggregates were cleaved. After salt addition, the average particle size of MNCPs decreased, but a local demulsification phenomenon appeared, thereby reducing the release rate of fatty acids. After subsequent homogenization, the average particle size of MNCPs was further reduced and MNCPs were rearranged; the membrane structure was changed, and the number of contact sites between lipids and enzymes in MNCPs was increased, promoting the release of fatty acids and consequently compensating for the decrease in the release rate of some fatty acids in bighead carp head soup after adding salt. Therefore, the changes in the composition and microstructure of MNCPs induced by salt and homogenization may be the major cause of the differences in the digestion properties of MNCPs.

Key words: bighead carp head soup; micro/nano-sized colloidal particles; salt addition; homogenization; digestion characteristics