In recent years, because of the need to design food with a desirable texture, the study of rheological modeling for investigating biphasic systems suitable for food applications has received attention.
In this work, O/W emulgels were obtained by emulsifying an oil phase made of extra virgin olive oil and soy lecithin with a particle hydrogel structured with citrus fiber. Samples were prepared using microfluidization and modeled according to composite gel theories. The fiber fraction (xf) ranged from 0.01 w/w to 0.04 w/w, whereas that of the oil phase (φ) ranged from 0.05 w/w to 0.5 w/w. The viscoelastic behavior of samples in a linear region previously determined by the stress sweep test was investigated with frequency sweep tests. The relative complex modulus (G*r) was defined as the ratio between the complex modulus of the emulgel and the complex modulus of the continuous phase, and was adopted for discussing and comparing data and for rheological modeling. Microstructural and morphological investigations were carried out; laser diffraction and optical and confocal laser microscopy were adopted to support the rheological outcomes. The rheological results showed that G*r (0.23 - 1) decreased with xf and φ, whereas the phase angle (δ) exhibited a more complex trend. Microstructural and morphological changes were observed at high φ (close to 0.5). For the rheological modeling of samples, both theoretical and semi-empirical models were used. The Kerner model for incompressible material and the Palierne model for monodisperse systems, which take into account interfacial properties, were used to fit the data in both original and modified form. Finally, a modified Kerner model was applied to design emulgels with a consistency similar to that of light mayonnaise and light spreadable cheese. The results suggest that the modified Kerner model can be effectively used for consistency prediction from a practical point of view.
