Antioxidant properties and physical and sensory characteristics of a corn-based extruded breakfast cereal prepared with whole-grain wheat flour, "jabuticaba" and resistant starch

Abstract

Extrusion is one of the most common processes used to obtain ready-to-eat (RTE) breakfast cereals, where under the influence of high temperature, moisture, pressure and shear, a viscoelastic mass is formed that emerges from the extruder and expands. Starch is the main constituent and responsible for the structural characteristics of the breakfast cereal, which makes it a highly energetic food, however, nutritionally incomplete. Aware of the growing demand of consumers concerned with their health, studies have shown that it is possible to introduce ingredients that enhance the nutritional and/or functional value of extruded products and, in the case of breakfast cereals, whole-grain wheat flour, fruit products and resistant starch are examples with the potential of associating functionality to the product. Whole-grain wheat, apart from fiber, contains antioxidant compounds, and its consumption is related to the reduction of the risk of diseases such as colon cancer, diabetes and cardiovascular diseases. Similarly, "jabuticaba", a tropical fruit native of Brazil, presents a significant content of anthocyanins and antioxidant activity, appearing as an excellent option. Antioxidants have an important role in the prevention of diseases, acting through mechanisms such as the reaction with or removal of free radicals, reduction of peroxides and metal catalyst complex formation. Resistant starch presents behavior similar to dietary fiber, and has been related to local and systemic beneficial effects (primarily in the large intestine and through a series of mechanisms, respectively). From a technological point of view, resistant starch does not significantly affect product properties. However, there are few studies related to the effect of processing on these physiological functional compounds. Thus, it is important to study the influence of extrusion process parameters on the antioxidant activity and on the integrity of resistant starch, to permit the claim of their benefits to human health. The objective of this study is to evaluate the effect of the substitution of corn flour by whole-grain wheat flour (WGWF), extrusion temperature and raw-material moisture content on the technological, sensory and nutritional properties of a RTE breakfast cereal elaborated also with dehydrated "jabuticaba" (J) and resistant starch (RS). The raw-materials (corn flour, WGWF, J and RS) will be analyzed with respect to: chemical composition, phenolic compounds content and profile and antioxidant activity. To produce the breakfast cereals, a 23 experimental design will be followed. The assays will be carried out in a double-screw extruder model ZSK 30 - Werner Pfleiderer Corp. The extruded products will be evaluated physically (expansion index, density/specific volume, hardness/firmness and color), chemically (water activity, dietary fiber, resistant starch, phenolic compound content and antioxidant activity) and sensorially (acceptance and purchase intention tests), as well as analyses during shelf-life. The optimum formulation and processing conditions will be defined based on the best technological characteristics and functional properties. With this study, we intend to visualize what occurs with the functional compounds added during processing. (AU)