Effects of twin‐screw extrusion processing variables on physicochemical properties and antioxidant activity of rice incorporated with Agriophyllum squarrosum flour

Effects of extrusion temperature on structure and physicochemical properties of proso millet starch

Due to its thermal stability, and high viscosity, proso millet starch has limited practical applications. Extrusion can alter the functional properties of starch by pre-gelatinization, but the specific effects of extrusion temperature on starch behavior are not clear. In this study, proso millet starch was modified using extrusion at varying temperatures (70 °C, 90 °C, 110 °C), and its structure as well as physicochemical properties were evaluated. As the extrusion temperature increased, the starch granules were gelatinized, and the particle size increased significantly. The relative crystallinity of extruded starch decreased and the short-range order was enhanced notably, but the starch still exhibited an A-type structure. Starch chains degraded, migrated, and aggregated, showing an increase in the double helix content, but there was no difference in the single helix structure with temperature. With the increase of extrusion temperature, the amorphous layer of extruded starch thickened. Moreover, the peak viscosity, breakdown viscosity and setback viscosity initially increased and then decreased, the peak temperature and enthalpy change increased. The water absorption index, water solubility and swelling power significantly decreased with increasing temperatures. The freeze-thaw stability and transparency of extruded starch decreased, and showed a downward trend with prolonged time. The above results indicate that extrusion treatment effectively modifies the thermal stability and viscosity of proso millet starch, laying a foundation for applying it different industrial applications.

Effect of extrusion using plasma-activated water on the structural, physicochemical, antioxidant and in vitro digestive properties of yam flour

The synergistic effects of plasma-activated water (PAW) and twin-screw extrusion (TSE) on the structural, physicochemical, antioxidant, and digestive properties of yam flour (YF) were studied. Compared to common TSE, PAW-TSE reduced the protein, starch, and polyphenol contents, swelling power, and gel property of YF, while PAW-TSE enhanced the flavonoid content, whiteness index, solubility, and antioxidant property of YF. Moreover, the results of structural characterization and differential scanning calorimetry indicated that the long-range or short-range ordering, and gelatinization enthalpy of starch in YF were reduced after PAW-TSE, while the structure ordering of proteins in YF increased. Furthermore, the in vitro digestibility results demonstrated a reduction in the rate of enzymatic hydrolysis, coupled with an increase in total contents of slowly digestible and resistant starch after PAW-TSE. It should be noted that TSE using PAW prepared by a longer plasma treatment resulted in a more significant improvement effect on YF.

Comparison of quinoa and highland barley derived dietary fibers influence on the physicochemical properties and digestion of rice starch

This study investigated the potential of highland barley and quinoa dietary fibers, rich in β-glucan and pectin respectively, as cost-effective and nutritionally valuable physical modifiers for rice starch (RS). HPAEC revealed differences between the monosaccharide composition of soluble and insoluble dietary fibers sourced from highland barley and quinoa (HSDF, HIDF, QSDF and QIDF). Results from both RVA and DSC analysis revealed that the addition of low amounts of dietary fiber significantly modified the pasting properties of RS. Notably, the addition of quinoa soluble dietary fiber (QSDF) significantly inhibits the formation of a stable gel network in rice starch, even at low concentrations (0.1 %), as confirmed by rheological measurements. Furthermore, the incorporation of QSDF effectively reduces the content of rapidly digestible starch in rice starch by 15.6 % and increases the content of slowly digestible starch, from 23.36 % ± 3.02 % to 31.07 % ± 3.98 %. By leveraging the compositional richness of these fibers, this research opens up novel opportunities for developing functional food products with improved nutritional profiles, as well as for improving texture and reducing glycemic index (GI) in starch-based foods.

Correlation analysis between extrusion process variables and quality of purslane leaf powder rice extrudates

Extrusion has become one of the most popular techniques in food processing, and the process parameters are closely related to product quality. Purslane (Portulaca oleracea L.) can be used in medical and food products as a vegetable and herb. It has limited application in extrusion. The effects of extrusion process variables (screw speed, barrel temperature, and feed moisture) on system variables (specific mechanical energy [SME], die head pressure, and torque) and target variables (water absorption index, water solubility index, iodine blue value, color, pasting properties, and textural properties) of purslane powder compound rice were studied. The results showed that SME was moderately positively correlated with screw speed (r = 0.608, p < 0.05). However, torque was moderately negatively correlated with feed moisture (r = -0.574, p < 0.05), and die head pressure was moderately negatively correlated with barrel temperature (r = -0.635, p < 0.01). The target variables of extrudates were also correlated with the system parameters to varying degrees. These results are helpful to control and predict the texture, pasting properties, and other quality characteristics of extruded products containing purslane powder. PRACTICAL APPLICATION: The results showed that torque and die head pressure were moderately negatively related to barrel temperature, specific mechanical energy was moderately positively related to screw speed, peak viscosity and breakdown viscosity were moderately negatively related to specific mechanical energy, and water absorption index was moderately negatively related to torque and die head pressure. It provides a reference for the research of influencing system parameters and changing product quality by controlling extrusion process parameters. In this study, some possibilities for the application of broken rice and purslane in extrusion processing were proposed.

Modifying the rheological properties, in vitro digestion, and structure of rice starch by extrusion assisted addition with bamboo shoot dietary fiber

This paper investigated the effect of extrusion treatment on the rheological properties, in vitro digestibility, and multi-structure of starch with or without bamboo shoot dietary fiber (BSDF). The viscoelasticity and thixotropy decreased after extrusion treatment, however, they increased after BSDF addition, and decreased with increasing BSDF content. The starch granules became smooth and formed big lumps after extrusion treatment. The dense lumps became loose after the addition of BSDF. Extrusion treatment changed the movement and arrangement of starch chains and thus the relative crystallinity and branching degree decreased by 92.6% and 40.9%, respectively. The disruption of starch further increased rapid digestion starch (RDS) content by 10%. The decreased disruption of starch granules and increased entanglement between BSDF and starch decreased the RDS content. The addition of BSDF is a novelty method to enhance the nutritional properties and control the physicochemical properties of extruded starchy foods.

Effects of soy flour types and extrusion-cooking conditions on physicochemical, microstructural and sensory characteristics of puffed rice snack base

The physicochemical properties of puffed rice snack base (PRSB) prepared via extrusion cooking under various feed moisture contents and screw speeds were investigated. The moisture content, screw speed, and soy flour type significantly (p < 0.05) affected the physicochemical properties of PRSB viz; size, density, porosity, color, breaking strength, crystallinity, water absorption index (WAI) and water solubility index (WSI). While, a slight effect on pasting properties was observed between PRSB added with defatted and full-fat soy flour, respectively. Soy flour lipids significantly (p < 0.05) influenced extrusion cooking conditions especially at high screw speed and feed moisture content. The result revealed that extrusion cooking with addition of full-fatty soy flour can be exploited as a viable method to produce PRS with a high expansion ratio and low breaking strength at recommended extrusion conditions of feed moisture content of 19 % and screw speed of 300 rpm.