Effects of extrusion with CO2 injection on physical and antioxidant properties of cornmeal-based extrudates with carrot powder.

Carrot powder and cornmeal were extruded at ratios of 0:100, 10:90, and 20:80 with and without CO2 injection at die temperatures of 80, 100, and 120 °C. The effects of the composition of the extrudate, die temperature, and CO2 injection on physicochemical and antioxidant properties of extruded products were studied. The results showed that die temperature had a significant effect on expansion ratio (ER), specific length, piece density, color, water absorption index (WAI), and water solubility index (WSI) (p < 0.05). The injection of CO2 significantly affected the ER, WAI, WSI, lightness, redness, microstructure, total phenolic content, and the 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity of extrudates (p < 0.05). Increasing the proportion of carrot powder in extrudates resulted in better antioxidant properties and higher levels of crude ash, crude fat, crude protein, and redness; however, it resulted in lower WAI, lightness, and yellowness (p < 0.05). The study demonstrated that extrusion with CO2 injection and addition of carrot powder may improve the nutritional quality and structure-forming ability of extrudates.

The Effect of Extrusion Conditions on Water-extractable Arabinoxylans from Corn Fiber.

The effect of feed moisture contents (30%, 40%, and 50%) and screw speed (200 rpm, 250 rpm, and 300 rpm) on the corn fiber gum (CFG) yield and soluble arabinoxylans (SAX) content of destarched corn fiber was investigated. The CFG yields and SAX contents of extruded, destarched corn fiber were higher than that of destarched corn fiber. In extruded, destarched corn fiber, increased screw speed and decreased feed moisture contents resulted in a higher SAX contents. The maximum yields of CFG obtained from extruded, destarched corn fiber were 79.1±19.0 g/kg (30% feed moisture content) and 82.3±11.30 g/kg (300 rpm screw speed). The highest SAX content was also observed at a screw speed of 300 rpm. The results of the present study show that water extraction and extrusion combined have the potential to increase CFG and SAX yields from corn fiber.

Influence of germination and extrusion with CO(2) injection on physicochemical properties of wheat extrudates.

Whole wheat and germinated wheat flour were extruded in a laboratory co-rotating twin screw extruder with die temperatures (90 and 130°C), screw speeds (150 and 200rpm) and CO2 injection. The effects of germination and extrusion process on specific mechanical energy (SME) input, expansion ratio, specific length, piece density, elastic modulus, breaking strength, colour, water solubility index (WSI), water absorption index (WAI) and microstructure were determined. The study showed that the use of germinated wheat flour increased the specific length, lightness and the WSI. When CO2 was injected, the expansion ratios (only 90°C die temperature for extruded germinated wheat) and lightness were significantly increased (p<0.05). The chemical properties (crude protein, fat, ash, reducing sugar, γ-aminobutyric acid, soluble arabinoxylans, ß-glucan and phytic acid) were also investigated. The germination step and extrusion process mainly affected the chemical properties. However, the difference of die temperatures, screw speed and CO2 injection had slight effect on the chemical properties.

Influence of twin-screw extrusion on soluble arabinoxylans and corn fiber gum from corn fiber.

BACKGROUND: The effect of feed moisture content and screw speed in the extrusion process with and without chemical pretreatment of corn fiber was investigated. Different chemical pretreatment methods (NaOH and H2 SO4 solution) were compared. The improvement of reducing sugar, soluble arabinoxylans (SAX) content and the yield of corn fiber gum was measured. RESULTS: A high reducing sugar content was obtained in the filtrate fraction from the extruded destarched corn fiber (EDCF) with H2SO4 pretreatment. Feed moisture content most effectively improved both reducing sugar and SAX content of filtrate. Increasing feed moisture content and screw speed resulted in a higher SAX content in the filtrate of the EDCF with NaOH pretreatment. The SAX content of the residual solid from the EDCF with NaOH pretreatment was higher compared to H2SO4 pretreated and unpretreated samples and significantly increased with decreasing feed moisture content. The screw speed did not have a major impact after enzyme hydrolysis. The yield of corn fiber gum was increased by 12% using NaOH pretreatment combined with extrusion process as compared to the destarched corn fiber. CONCLUSION: The results show the great potential of the extrusion process as an effective pretreatment for disruption the lignocelluloses of corn fiber, leading to conversion of cellulose to glucose and hemicelluloses to SAX and isolation of corn fiber gum.