Browsing by Author "Suomalainen, Liisa"

In recent years the demand for plant-based products has grown. In high-moisture extrusion the water content of extrudate mass is approximately 40-80% and plant protein products that mimic meat can be produced. The aim of this Master’s thesis was to study how faba bean starch concentrate content and extrusion factors affected the properties of pea protein isolate based extrudates and torque and pressure of extruder in high-moisture extrusion. The effect of frozen storage to the mechanical properties of extrudates was also studied and what kind of bonds between proteins were found in extrudates. Hypothesis was, that increase of starch concentrate content would result in more fibrous structure in the extrudates. Split-plot Box-Behnken-design was used as an experimental design. Independent variables were starch concentrate content (10, 30 and 50%), water content in extrusion (55; 57.5 and 60%) and temperature of long cooling die (40, 60 and 80 ℃). Response variables were the properties of extrudates and torque and pressure during extrusion. When starch concentrate content increased for example the perpendicular and longitudinal cutting strengths of fresh extrudates increased statistically significantly, but their water contents, water absorption capacities and lightness (L*) decreased statistically significantly. When the water content of extrusion increased, for example the water content of extrudates increased statistically significantly, but the values of their mechanical properties and torque and pressure during extrusion decreased statistically significantly. When the temperature of long-cooling-die increased for example the hardness of the fresh extrudates increased statistically significantly, but their water absorption capacities and torque and pressure during extrusion decreased statistically significantly. As a consequence of frozen storage for example increasing of starch concentrate content didn’t increase the perpendicular and longitudinal cutting strengths of extrudates statistically significantly. The values of hardness, gumminess, and chewiness in frozen-storaged extrudates were smaller than in the fresh extrudates. As a result of increasing the starch concentrate content the number of noncovalent interactions between proteins in the extrudates decreased and the number of covalent disulfide bonds increased. The extrudates had a fibrous structure when starch concentrate content was 10% or 30%, but in 50% the fibrous structure was not visible anymore. Higher temperature of long cooling die and water content in extrusion resulted in more visible fibrous structure in the extrudates. More research about the effect of extrusion factors and addition of polysaccharides to the properties of extrudates is needed. It enables the production of even more diverse and high-quality plant protein based products to meet the expectations of the consumers.