Enhancing Nutritional Value of Processed Cheese Slices through Soy Protein Isolate: A Physicochemical Study

Abstract

Processed cheese is widely consumed due to its uniform structure, extended shelf life, and formulation flexibility. This study evaluated the effect of soy protein isolate (SPI) incorporation on the physicochemical properties of milk-based processed cheese slices using a completely randomized design with five SPI levels (0%, 5%, 10%, 15%, and 20%) and triplicate measurements. Parameters analyzed included moisture content, water activity (aw), pH, color, texture, and proximate composition. The results showed that SPI addition significantly (p < 0.05) affected all physicochemical parameters. Moisture content decreased from 59.10% to 54.59%, accompanied by a reduction in water activity from 0.9644 to 0.9556 as SPI concentration increased. Protein content increased progressively from 7.41% to 11.59%, while ash content increased slightly from 4.34% to 4.63%. In contrast, fat content decreased at higher SPI levels, reaching 14.94% at 20% SPI. Color analysis showed a decrease in lightness (L*) from 88.99 to 83.12, indicating a darker product with increasing SPI concentration. These changes are attributed to the high water-binding capacity and functional properties of SPI, which promote stronger interactions with the casein matrix, resulting in reduced free water and a denser protein network that also contributes to increased firmness. In conclusion, SPI can be effectively utilized as a protein fortification ingredient in milk-based processed cheese, significantly enhancing protein content while modifying moisture distribution, color, and structural properties, although formulation optimization is required to balance nutritional improvement with physicochemical quality.