Introduction Mayonnaise is one of the world’s most popular sauces. It is a semi-solid oil-in-water emulsion made by mixing vegetable oil, egg yolk, water, vinegar, and other ingredients. Due to the high calorie and cholesterol content of egg yolks, excessive consumption of mayonnaise can lead to health-related problems. Major issues faced by mayonnaise producers include fat oxidation during storage, which leads to off-flavor and taste, as well as reduction in nutritional value and food safety. These factors may negatively affect on the consumer acceptance of mayonnaise. With increasing consumer demand for low-fat and low-cholesterol foods, low-fat mayonnaise has significant consumption potential. One of the consumer demands is to reduce the fat content in mayonnaise and salad dressing. Fats play many functional roles in food emulsions, contributing to the taste, appearance, texture, and shelf life of the product in specific ways. Therefore, it is challenging to maintain the quality of traditional products when preparing low-fat foods. It is possible to select specific fat substitutes in particular amounts to create a product with a texture similar to traditional mayonnaise. Light mayonnaise often contains certain fats added to help stabilize the emulsion and thicken its consistency. This research studied the possibility of using aloe vera gel as partial fat substitute in mayonnaise. Materials and Methods All the powdered ingredients were mixed together with eggs, water, and half of the required amount of vinegar in a blender for 3 minutes. To form an emulsion, oil was added in two stages while stirring together with starch and gums for 5 minutes. Mixing oil and the aqueous phase simultaneously leads to the formation of a water-in-oil emulsion. Finally, the remaining vinegar was added and mixed for 3 minutes until the fat particles were evenly dispersed in the sauce. Aloe Vera gel was also added in proportion to the reduction of oil according to the formulation of the samples. The optimal mixture design was used for three independent variables: oil A 15-60%, gel B 0-55%, and water C 0-10%. The multiple combinations of these variables led to an experimental design with 16 samples that were determined using Design Expert software, and the physicochemical, rheological, and textural characteristics of the samples were investigated. Additionally, suitable regression equations and mixed contour diagrams were obtained by this software for each response. Results and Discussion The results showed that increasing the replacement percentage of aloe vera gel and decreasing the percentage of oil led to an increase in pH and a decrease in acidity, stability, textural properties, and transparency of the samples. To describe the rheological properties, Bingham\\\'s model was used, and the viscosity parameters and Bingham\\\'s yield stress were investigated with an increasing the percentage of aloe vera gel replacement. Additionally, the apparent viscosity of the samples exhibited a decreasing trend and thinning behavior with shear. These changes in characteristics are attributed to the effect of adding fat to the mayonnaise formulation. The optimal values of independent variables in the production of low-fat mayonnaise were oil (40%), aloe vera gel (30%) and water (0%), respectively. Conclusion This research showed that aloe vera gel can be used in the formulation of mayonnaise as apartial substitute to oil. Due to the strong demand from consumers for this product, reformulating this high-fat emulsion is a fundamental need in the food industry. The use of aloe vera gel offers many benefits, including reducing cholesterol and fat levels overall, increasing microbiological stability, and, in some cases, lowering manufacturing costs.

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