Filled snack production by coextrusion-cooking: 1. Rheological modelling of the process

Gluten-Free Precooked Rice-Yellow Pea Pasta: Effect of Extrusion-Cooking Conditions on Phenolic Acids Composition, Selected Properties and Microstructure

Rice/yellow pea flour blend (2/1 ratio) was used to produce gluten-free precooked pasta using a single-screw modified extrusion-cooker TS-45. The effect of moisture content (28%, 30%, and 32%) and screw speed (60, 80, and 100 rpm) on some quality parameters was assessed. The phenolic acids profile and selected pasta properties were tested, like pasting properties, water absorption capacity, cooking loss, texture characteristics, microstructure, and sensory overall acceptability. Results indicated that dough moisture content influenced all tested quality parameters of precooked pasta except firmness. Screw speed showed an effect only on some quality parameters. The extrusion-cooking process at 30% of dough moisture with 80 rpm is appropriate to obtain rice-yellow pea precooked pasta with high content of phenolics and adequate quality. These pasta products exhibited firm texture, low stickiness, and regular and compact interne structure confirmed by high score in sensory overall acceptability.

Thermoplastic Foams from Zein and Gelatin

The aim of this study was to characterize the foaming of natural proteins as thermoplastic polymers. In particular, two proteins, one of vegetal origin, zein, and one of animal origin, gelatin, were processed to achieve thermoplastic polymers, and subsequently foamed by a gas foaming batch process. The effects of suitable plasticizing additives and melt-mixing process on the thermal and mechanical properties of the thermoplasticized proteins were evaluated to assess the thermoplastic characteristics of these materials. Furthermore, selected protein/plasticizers systems were foamed with mixtures of CO2 and N2 as blowing agents, in a batch foaming apparatus, at different temperatures, pressures and pressure drop rates, to evaluate the processing window and the final properties of the foams. Foams with densities of 0.1 g/cm3 and morphologies characterized by uniform distributions of cells with 10 μm diameters were obtained. Results indicated the suitability of zein and gelatin for being processed with classical thermoplastic processing technologies including melt mixing and foaming and their potentials as biodegradable polymers.

Effect of process and machine parameters on physical properties of extrudate during extrusion cooking of sorghum, horse gram and defatted soy flour blends

Extrusion cooking of sorghum (Sorghum vulgaris), horse gram (Dolichos biflorus) and defatted soy (Glycine max) flour blends was done to prepare snacks by using a Brabender single-screw laboratory extruder. The combined effect of moisture content, blend ratio of feed, barrel temperature and screw speed of extruder on physical parameters of extrudate was studied. It was observed that 15% moisture content of feed, 80:10:10 (sorghum flour: horse gram flour: defatted soy flour) of blend ratio, 130 °C barrel temperature and 130 rpm of screw speed gave the highest sectional expansion index and longitudinal expansion index of extrudate, while 12% moisture content, 75:15:10 of blend ratio of feed, 135 °C of barrel temperature and 135 rpm of screw speed gave lowest bulk density of extrudate. A central composite rotable design (CCRD) of response surface methodology was used to develop prediction model. Second order quadratic regression model fitted adequately in the variation. The significance was established at p ≤ 0.05. It was also observed that increasing feed moisture content results in a higher density and lower expansion of extrudate. Increasing barrel temperature and screw speed reduced density but increased expansion of extrudate.