Extrusion Conditions and Amylose Content Affect Physicochemical Properties of Extrudates Obtained from Brown Rice Grains

Abstract

The utilization of whole grains in food formulations is nowadays recommended. Extrusion cooking allows obtaining precooked cereal products and a wide range of ready-to-eat foods. Two rice varieties having different amylose content (Fortuna 16% and Paso 144, 27%) were extruded using a Brabender single screw extruder. Factorial experimental design was used to study the effects of extrusion temperature (160, 175, and 190°C) and grits moisture content (14%, 16.5%, and 19%) on extrudate properties. Specific mechanical energy consumption (SMEC), radial expansion (E), specific volume (SV), water absorption (WA), and solubility (S) were determined on each extrudate sample. In general, Fortuna variety showed higher values of SMEC and S (703–409 versus 637–407 J/g; 33.0–21.0 versus 20.1–11.0%, resp.) than those of Paso 144; on the contrary SV (8.64–3.47 versus 8.27–4.53 mL/g) and WA tended to be lower (7.7–5.1 versus 8.4–6.6 mL/g). Both varieties showed similar values of expansion rate (3.60–2.18). Physical characteristics depended on extrusion conditions and rice variety used. The degree of cooking reached by Paso rice samples was lower than that obtained for Fortuna. It is suggested that the presence of germ and bran interfered with the cooking process, decreasing friction level and broadening residence time distribution.

Soaking and extrusion effects on physicochemical parameters, phytic acid, nutrient content and mineral bio-accessibility of whole rice grain

“…It is possible to observe the different expansion reached by the extrudates. E values ranged between 1.64 and 3.28, the highest values corresponding to 160 C and 14% M condition, as it was expected according to previous works using whole rice grits (González et al, 2013a). The effects of T and M were significant in both linear terms and the quadratic term of T. E is an important characteristic of snack type products.…”

Physicochemical properties and structural characteristics of whole grain Oryza sativa L. with different treatments

“…Available carbohydrates were higher in extruded samples because of macromolecular degradation, which depends on extrusion cooking parameters such as temperature, moisture and screw speed (Mercier, 1993). Values of WA ( Table 2) are in the range of those obtained for brown rice at similar extrusion cooking conditions in a previous work (González et al, 2013a). WA is directly related with WS 11 until the maximum WA is reached.…”

“…While the extruder feeding section was maintained cool by circulating water through the jacketed device, the metering and die sections were both kept at the temperature corresponding to each run by using the heat control device of the extruder. The extrusion cooking conditions: 160 ºC -14 %M for EBR; 160 ºC 16.5 %M for ESR; 175 ºC 14 % M for EGR were selected according to preliminary studies (González et al, 2013a) taking into account good expansion, sensorial hardness and flavor.…”

Nutritional, physical and sensory properties of extruded products from high-amylose corn grits

“…Table 3 shows that the HACG extrudate had a lower WSI and a higher WAI, which indicated the HACG extrudate possessed a lower degree of gelatinization. The lower WSI was mainly caused by the higher amylose content because of the inverse relationship between the amylose content and solubility (González et al, 2013). The lower amylopectin/amylose ratio and higher crude fiber content contributed to the higher WAI.…”