Process cheese food was made using sodium citrate (2.7%) or trisodium phosphate (TSP, 2.7%) as emulsifying agents. No precooked cheese (rework) was used in some samples whereas in others the rework (20%) consisted of a cheese blend emulsified with sodium citrate (2.7%) and (a) briefly heated to 82 degrees C, (b) heated to 82 degrees C for 1 h, (c) heated to 82 degrees C for 5 h, and (d) heated to 82 degrees C for 5 h, frozen at -10 degrees C for 24 h, and thawed at +4 degrees C. Heating for extended periods of time produced so-called hot melt. When used as rework, hot melt considerably decreased the meltability of the product made. All samples under study were examined by light microscopy (LM), scanning electron microscopy (SEM), and transission electron microscopy (TEM). Gradual solubilization of the emulsifying agents in the cheese blend and emulsification of fat were visualized by LM and SEM. TEM revealed considerable changes in the protein matrices of the hot melt and the process cheese food made with TSP. Small electron-dense areas having a high affinity for osmium developed in both products, but their shapes and degrees of affinity for osmium were different. It was possible to detect the presence of hot melt used as rework in the process of cheese food samples under study.
Kalab, Miloslav; Yun, Joseph; and Yiu, Suk Hing
"Textural Properties and Microstructure of Process Cheese Food Rework,"
2, Article 10.
Available at: http://digitalcommons.usu.edu/foodmicrostructure/vol6/iss2/10