Effect of oil replacement with tofu and Persian gum on physicochemical, textural and rheological properties of Mayonnaise sauce

Increasing society's desire to consume healthy and low-calorie foods has led to the production of low-fat and healthy foods. In this study, the effect of oil replacement with tofu cheese and Persian gum on physicochemical, textural, rheological and sensory properties of Mayonnaise sauce as well as its particle size, were investigated. Tofu was replaced with fat at three concentration levels of 20, 35 and 50% and Persian gum was added to the sauce at three concentrations of 2.5, 3, and 3.5%. The control sample contained 60% fat and guzanthan gum. With increasing tofu, pH and acidity increased and with increasing Persian gum acidity decreased. With increasing tofu, histological test (hardness, adhesiveness, adhesive force, work done to hardness, apparent modulus) decreased and with increasing Persian gum, their increased. With increasing tofu, decreased particle size. With increasing gum until 3%, average of particle size decreased and with more increase of gum, average of particle size increased.  The rheological behavior of all samples at a shear rate of 0.01 to 1000 (on second) showed that the viscosity decreased with increasing tofu decreased and with increasing gum, increased. In all samples, with increasing shear rate, the viscosity was decreased, and the behavior of the samples was pyseudoplastic and the parameters followed the power law model. Sample with 20% tofu cheese and 3.5% Persian gum as top samples, whose properties are closer to fatty mayonnaise and can be called Mayonnaise with reduced fat.

Physical and thermal stability tests of the emulsion were performed with a centrifuge machine. PH test was performed using pH meter and acidity test in terms of acetic acid percentages. The fat percentage was performed with a Soxhlet. The texture properties were performed by back extrusion test and the parameters of hardness, adhesiveness, adhesiveness force, apparent modulus and force required to squeeze were calculated. The particle size was measured using a dynamic light dispersion apparatus, and the average particle size, mod, and D50 of the emulsion particles of oil were investigated. The rheological behavior was performed by the rheometer and sensory evaluation was conducted by the hedonic method. Statistical analysis was performed by using SPSS software and the mean comparison test at 5% probability level and in the form of factorial test.

In the physical and thermal stability test of the emulsion, no two phases were observed in the samples. This could be due to the strong structure of the emulsion and the high viscosity of the continuous phase. By increasing the tofu value, the pH increased, which can be attributed to the decrease in the concentration of hydrogen ion or the increase of the aqueous phase. With increasing amount of gum, there is no change in pH, because the Persian gum has a neutral nature. Increasing the amount of gum did not affect acidity. As the tofu increased, acidity increased, and this increase was very slight, which can be attributed to buffering mode of tofu due to high amounts of high amino acids. By increasing the tofu percentage, the percentage of fat decreases because the percentage of fat in tofu cheese is law and its protein content is much. The increase in gum did not affect the amount of fat, because Persian gum structure was made up of saccharides. The tofu increase up to 35% reduced the texture properties, because the aqueous phase increased, with increasing gum percentage, texture properties increased because it produced a strong gel structure. With the increase in tofu content, the particle size of the oil decreased, because with increasing the amount of fat, the particle size increased. By adding gum the particle size decreased to 3% and then increased, because in the Persian gum structure, there are insoluble branches and the solubility of these branches is low. In the evaluation of rheological behavior, flow behavior test was investigated; viscosity of all samples was reported at shear rates of 0.1, 1, 10, 100/ sec. In all samples, the viscosity decreases with increasing frequency. By increasing the gum at a constant shear rate, the viscosity increased, which can be explained by the fact that the formation of a stronger structure in the presence of higher concentrations of gum. By increasing the shear rate at a constant concentration of gum, the viscosity decreased, and the increase in gum with increasing shear rate also reduced the viscosity and sauce had profit and plastic behavior that could be due to the opening of the bonds. As the tofu percentage increased in all shear rates, viscosity decreased and by increasing the tofu value at a constant shear rate, the viscosity decreased, and the increasing tofu with increasing shear rate reduced viscosity due to high moisture content of the cheese. The rheological parameters of mayonnaise sauce were checked in accordance with the power law. As the gum increased, the consistency coefficient increased , because the number of molecules with high molecular weight in the liquid phase increased, with increasing the percentage of tofu cheese, the coefficient of consistency decreased. The flow behavior coefficient does not have a clear trend, and since it is less than 1, the samples are non-Newtonian. In the strain scan test in lower strains, mayonnaise always has linear viscoelastic behavior. By increasing the gum concentration, both the elastic and viscous components are transported to higher values, which can be due to more interaction between the Persian gum and the components of the emulsion. In the sensory evaluation of the samples, the addition of gum and tofu percentage was not effective. With regarding the data of the tests, mayonnaise sample was identified with the replacement of 20% tofu cheese and 3.5% Persian gum as a superior sample, which its properties are closer to fatty mayonnaise and can be classified as Mayonnaise with law Fat. An extensive medicinal property of Persian gum with tofu cheese in mayonnaise sauce makes it a rich and very good source.