Comportamento reológico e propriedades térmicas da goma da Pereskia aculeata Miller adicionada de solutos e hidrocoloides comerciais e uma aplicação em bebida láctea fermentada

Abstract

Pereskia aculeata Miller mucilage presents properties that can be used in industry as thickener, gelling agent and/or emulsifier. The understanding of OPN mucilage in food systems can be studied in aqueous solutions, which are widely used for studying of isolated compounds. Fermented milk products can be produced with hydrocolloids, such as guar gum (GG) and gum Arabic (GA), to maintain their quality during the shelf-life period and to replace fat. The objectives of this study were to characterize the rheological behavior and thermal properties of OPN mucilage in different model solutions, and to evaluate the application of hydrocolloids in fermented milk beverages. OPN mucilage were extracted and the gums were prepared stirring for 30 min at 75°C. Rheological and thermogravimetric parameters were evaluated. The experimental design was divided into a 2 5-1 fractional factorial for screening factors (OPN mucilage, sucrose sodium chloride, calcium chloride and pH) and a 5x3x3 factorial (OPN mucilage, sucrose and sodium chloride). A mixture design was applied to studies of model solutions composed by OPN mucilage, GA, GG, sucrose, sodium chloride and deionized water. Rheological properties were evaluated. A hydrocolloid mix was defined and applied to a fermented milk beverage. Rheological and microstructural properties were studied. Model solutions studied for the selection factors presented pseudoplastic behavior in the presence of OPN mucilage, having significant effect over the apparent viscosity. Thermogravimetric analysis showed the presence of three distinct phases of mass loss with increasing temperatures, and may be related to water loss, change in conformation of polysaccharides, ending with remaining mineral material. OPN mucilage, sucrose and sodium chloride had significant effect over thermogravimetry responses. In full factorial studies, the samples presented Newtonian behavior with 0-1.25% OPN mucilage, and Power Law behavior with 2.50-5.00% OPN mucilage with a predominance of elastic behavior (G' > G" at 1Hz). Apparent viscosity had an increasing tendency with the increased concentration OPN mucilage. G' values are higher than those of G", confirming elastic predominant characteristic of the samples. Increasing OPN mucilage concentration increases this elastic behavior, contributing to the formation of stronger gels.The highest values for apparent viscosity of the model solutions with different hydrocolloids occurred on the region with hydrocolloids mix composed of 0.7 OPN mucilage, 0.0 GA and 0.3 GG, resulting in 0.5-0.7 Pa.s. Sucrose presented greater interference than sodium chloride over apparent viscosity. The effect of apparent viscosity, G’ and G”, were discussed, and the model solutions presented anti-thixotropic and pseudoplastic behavior with good fit to the Power Law rheological model. Fermented milk samples presented good fit to Power law and pseudoplastic and thixotropic behavior, also presenting predominant elastic behavior (G’>G”). The application of hydrocolloids mix increased the apparent viscosity and pH of the samples. The microstructure evaluation confirmed the results. Application of hydrocolloids mix with OPN mucilage on fermented milk showed feasibility.