Physicochemical, Functional and Microstructural Changes during the Emulsification Process of Processed Cheese

In this study, we investigated the changes in the functional properties (meltability and fat precipitation), texture, rheological properties, and microstructure of processed cheese during emulsification (5–30 min) at different temperatures (80 and 85 ℃). The results showed that as the emulsification time increased, the meltability and fat precipitation showed a decreasing trend, and the fat precipitation at 85 ℃ was significantly higher than that at 80 ℃ during the emulsification process (P < 0.05). The gumminess and chewiness increased significantly (P < 0.05) with the increase in emulsification time, and the hardness, gumminess and chewiness at 85 ℃ were greater than those at 80 ℃. The storage modulus (G’) of processed cheese was greater than the loss modulus (G”) at the same degree of emulsification for both temperatures and both G’ and G” showed an upward trend with increasing frequency from 0.1 to 10 Hz. The microstructure of processed cheese showed that the number of fat globules was greatly reduced, the diameter was decreased, the distribution of fat globules became more uniform, the protein matrix became smoother and the cheese structure became denser at 5–15 min of emulsification. However, the microstructure of processed cheese was honeycomb-like at 20–30 min of emulsification, suggesting excessive creaming reaction. Therefore, a short emulsification time during the processing of processed cheese will result in inadequate creaming reaction; too long emulsification time will cause adverse changes in cheese texture. During the emulsification process, the protein-protein and protein-fat interactions were enhanced, thereby improving the functional properties of the product. In conclusion, the emulsification process of processed cheese is closely related to its physicochemical and functional properties and microstructure. This study provides some theoretical guidance for future process development of processed cheese production.