Development and Characterization of Extrudates Based on Rapeseed and Pea Protein Blends Using High-Moisture Extrusion Cooking

Rapeseed protein is not currently utilized for food applications, although it has excellent physicochemical, functional, and nutritional properties similar to soy protein. Thus, the goal of this study was to create new plant-based extrudates for application as high-moisture meat analogs from a 50:50 blend of rapeseed protein concentrate (RPC) and yellow pea isolate (YPI) using high-moisture-extrusion (HME) cooking with a twin-screw extruder to gain a better understanding of the properties of the protein powders and resulting extrudates. The effects of extrusion processing parameters such as moisture content (60%, 63%, 65%, 70%), screw speed (500, 700, and 900 rpm), and a barrel temperature profile of 40–80–130–150 °C on the extrudates’ characteristics were studied. When compared to the effect of varying screw speeds, targeted moisture content had a larger impact on textural characteristics. The extrudates had a greater hardness at the same moisture content when the screw speed was reduced. The specific mechanical energy (SME) increased as the screw speed increased, while increased moisture content resulted in a small reduction in SME. The lightness (L*) of most samples was found to increase as the target moisture content increased from 60% to 70%. The RPC:YPI blend was equivalent to proteins produced from other sources and comparable to the FAO/WHO standard requirements.

The Effect of pH and Storage Temperature on the Stability of Emulsions Stabilized by Rapeseed Proteins

Rapeseed press cake (RPC), the by-product of rapeseed oil production, contains proteins with emulsifying properties, which can be used in food applications. Proteins from industrially produced RPC were extracted at pH 10.5 and precipitated at pH 3 (RPP3) and 6.5 (RPP6.5). Emulsions were formulated at three different pHs (pH 3, 4.5, and 6) with soy lecithin as control, and were stored for six months at either 4 °C or 30 °C. Zeta potential and droplet size distribution were analyzed prior to incubation, and emulsion stability was assessed over time by a Turbiscan instrument. Soy lecithin had significantly larger zeta potential (−49 mV to 66 mV) than rapeseed protein (−19 mV to 20 mV). Rapeseed protein stabilized emulsions with smaller droplets at pH close to neutral, whereas soy lecithin was more efficient at lower pHs. Emulsions stabilized by rapeseed protein had higher stability during storage compared to emulsions prepared by soy lecithin. Precipitation pH during the protein extraction process had a strong impact on the emulsion stability. RPP3 stabilized emulsions with higher stability in pHs close to neutral, whereas the opposite was found for RPP6.5, which stabilized more stable emulsions in acidic conditions. Rapeseed proteins recovered from cold-pressed RPC could be a suitable natural emulsifier and precipitation pH can be used to monitor the stability in emulsions with different pHs.

Rapeseed protein as a novel ingredient of gluten-free bread

The aim of the study was to analyze the influence of rapeseed protein isolate on physico-chemical properties, sensory attributes and storage of gluten-free bread prepared on the basis of corn and potato starch mixture with the addition of pectin and guar gum. Starches used in bread formulation were replaced with rapeseed protein isolate in the amounts 6–15%. The bread was characterized in terms of physical properties, including volume, crumb structure and color, which was accompanied with sensory assessment. Texture and thermal properties were determined during 3 days of storage. It was observed that the presence of rapeseed protein, especially at higher levels, caused an increase in bread volume and density of pores and a decrease in crumb porosity, as compared to the control. Partial replacement of starch with rapeseed protein caused a significant increase of b* parameter, reflecting rising yellowness, which positively influenced bread acceptance. Rapeseed protein limited bread staling during storage in comparison to control sample. The results demonstrate that rapeseed protein could become a valuable component of gluten-free bread, as it provides valuable amino acids, but also beneficially influences quality characteristics.