Influence of heat denaturation and freezing–lyophilization on physicochemical and functional properties of quinoa protein isolate

Abstract Backgrounds and objectives Quinoa protein isolate has been shown to confer significant health benefits. However, it is necessary to evaluate the effect of processing on its properties. Therefore, the aim of this work was to evaluate the influence of heat denaturation or freezing followed by lyophilization on the physicochemical and functional properties of the quinoa protein isolate. Findings Freezing–lyophilization of quinoa protein isolate (QPI‐FL) exhibited a higher foaming capacity and emulsifying capacity at pH 10, and the oil retention capacity was ten times greater that exhibited by the unmodified quinoa protein isolate (QPI), while the particle size and water and oil retention capacity in the modified protein isolate by heat denaturation (QPI‐HD) were twice as compared to QPI. The pH had a significant effect on all physicochemical and functional properties. The flow properties and the micrograph analysis of modified protein isolates revealed greater porosity in comparison with those of the unmodified protein isolate. QPI‐FL showed higher water adsorption capacity at high water activity and a greater displacement in the thermal transitions. Conclusions In general, heating did not significantly affect the functional properties of the quinoa protein isolate, while the freezing–lyophilization improved them, which may be of interest in the processes of foods that include in their process the heating or freezing. Significance and novelty Quinoa protein isolate can be added to different food products with the purpose of improving its composition. However, heating and freezing are two frequent operations in most processes that could affect their properties.