In this research, the effect of enriching processed cheese with three food ingredients—egg white powder (0%, 3%, and 6% w/w), soy protein isolate (0%, 7.5%, and 15% w/w), and corn oil (0%, 8%, and 16% w/v)—was examined using response surface methodology within a central composite design. The study evaluated the physicochemical, textural, rheological, and microbiological characteristics of the processed cheese. The results showed that as the levels of egg white powder and soy protein isolate increased, the protein content of the samples also increased, whereas the addition of corn oil caused a decrease in this parameter (p < 0.05). Increasing the levels of corn oil enhanced the meltability and oiling-off properties of the processed cheese samples. Conversely, higher levels of egg white powder and soy protein isolate reduced the meltability and oiling-off. The required adhesion force decreased with increasing levels of corn oil and egg white powder but increased with higher levels of soy protein isolate. Additionally, higher concentrations of soy protein isolate increased the work required for cutting the cheese samples. At elevated levels of corn oil and soy protein isolate, the elasticity decreased, while higher levels of egg white powder improved elasticity. Furthermore, microbiological findings revealed that the total colony count (≤ 10 cfu/g) and Staphylococcus (negative) values remained within the standard range set by the national standard of Iran. However, mold and yeast levels, as well as the total microbial count, increased during the 90-day storage period (p < 0.05). In conclusion, incorporating egg white powder (6% w/w), soy protein isolate (7.5% w/w), and corn oil (16% w/v) into processed cheese formulations enhances its overall characteristics. This approach shows promise for developing new functional processed cheese products.
