Structure–rheology characterization of whey-less Feta cheese containing milk protein concentrate/soy protein isolate

In this study, the properties of whey-less Feta cheese (WLFC) manufactured from milk protein concentrate (MPC) with the addition of soy protein isolate (SPI) were investigated. Six treatments were made using different ratios of MPC:SPI (12:0, 10:2, 9:3, 8:4, 7:5, 6:6% w/v) and stored for 45 days. Then, the textural properties, rheological behavior of samples, and microstructural and sensory features were evaluated. Furthermore, FTIR spectroscopy was used to provide spectral data on the protein, acids, carbohydrates, lipids, and water. The results showed that different concentrations of SPI significantly affected pH, acidity, total solids (TS), and color parameters. So that, by increasing SPI concentration, the lightness and greenness decreased, and the yellowness increased. The viscoelastic behavior of all samples demonstrated a higher G′ compared to G″. The replacement of MPC with SPI decreased G′, G″, and texture parameters. The images of the microstructure indicated a weak structure with a more open protein network in WLFCs fortified with high levels of SPI (5, 6%). In conclusion, results showed that SPI could be a good substitution for MPC at a 2–3% concentration without negative effects on WLFCs.