Effect in Physical, Thermo‐Mechanical Properties, and In Vitro Starch Digestibility of Extruded and Microwave‐Expanded Snacks—Mixture of Blue Corn, Black Bean, and Chard: An Optimization Study

Abstract

A mixture of blue corn, black bean, and chard with a moisture content (MC) of 22.3–35.7% is extruded at different extrusion temperatures (ET) (102—142 °C) using screw speeds (SP) of 96–172 rpm, and the extruded mixtures are subsequently expanded using microwave radiation to produce third‐generation (3G) snacks. The degree of starch gelatinization (DG); in vitro starch digestibility (SD); specific mechanical energy (SME); physical properties: radial expansion (RE), flexural modulus (Ef), and bulk density (BD); and rheological properties: storage modulus (G′) and loss modulus (G″) are evaluated and optimized. In addition, X‐ray and microstructure analyses are studied to correlate the chemical and structural changes. The SP and MC affect most variables in the unexpanded snack (UETS) and microwave‐expanded snacks (MWES). Increased MC results in UETS with low SD, DG, rheological properties, and mechanical resistance. An increase in SP at low MC results in MWES with high RE, low BD, and Ef while an increase in MC lowers SD. Micrographs and X‐ray diffraction spectra reveals that the extrusion results in a V‐type starch crystalline structure. The optimal conditions (24% MC, 133 rpm, and 122 °C) result in good expansion and moderate SD, DG, and SME products.

The Textural and Physical Characteristics of Red Radishes Based on a Puncture Test

“…Other studies demonstrate the importance of the post-harvest mechanical properties of agri-food materials for the design and adoption of various handling, packaging, transport, and storage systems [6,30]. Physical properties, such as: peel strength, breaking strength, cutting energy consumption, pulp firmness, and post-harvest hardness of oranges were determined under different storage conditions, from their behavior in the ambient environment to refrigerated storage conditions [6,9,27,30,[33][34][35].…”

“…Consequently, the texture of agri-food can be seen as the manifestation of agri-material rheological properties [1][2][3][4][5][6][7]. Texture analysis involves measuring the rheological response when materials are subjected to mechanical forces such as: mechanical harvesting, cutting, shearing, chewing, compression, or stretching [1,3,5,8,9]. The study of agri-food texture is important to determine the resistance of a product to mechanical stress (mechanical harvesting of fruit and vegetables), to determine the deformation resistance of products subjected to processing, transport, and storage, and to ascertain the mechanic behavior of an agri-food product on consumption [4].…”