Effect of the extrusion process and expansion by microwave heating on physicochemical, phytochemical, and antioxidant properties during the production of indirectly expanded snack foods

The aim of this study was to evaluate the physicochemical, phytochemical, and antioxidant changes in different stages (unprocessed mixture [UM], extruded pellet [EP], and expanded product [EXP]) during the production of indirectly expanded snacks by microwave. Four mixtures (from corn starch/whole yellow corn flour), adding naranjita bagasse (NB) and/or skimmed milk powder, were used. Ash content, water absorption index (WAI), water solubility index (WSI), soluble dietary fiber (SDF), free phenolic compounds (FP), bound phenolic compounds (BP), and antioxidant activity (AOA) were higher in EP than in UM, whereas lipids, crude fiber, total carotenoids (TC), and total and insoluble dietary fiber (TDF and IDF) were lower. Also, WAI, WSI, color b*, FP, SDF, and AOA from FP were higher in EXP than in EP, while BP, TC, TDF, IDF, and AOA from BP were lower. The snacks with added NB presented acceptable sensory characteristics. Snacks with appropriate nutritional/nutraceutical properties from raw materials rich in bioactive compounds can be produced. Practical applications Based on the high demand of consumers for purchasing healthier products, the food industry has shown great interest in improving the nutritional properties of some products that are rich in calories, but very poor in nutrients. The incorporation of raw materials rich into bioactive compounds, such as cereals and by-products of the citrus industry, as well as the addition of milk powder for the fortification of snack foods has been highly recommended. Several studies have shown increased nutritional properties and potential health benefits on humans by the addition of these materials. Furthermore, there is little information on the physicochemical, phytochemical, and antioxidant changes that are generated during the processing of indirectly expanded snack foods.