Impact of the residual lipids of yellow mealworm protein isolate on the protein structure and techno-functionalities

Abstract: The current low consumer acceptability for mealworm could be enhanced by using insect protein-rich ingredients such as protein isolates. However, mealworm protein isolates (MPI) contain a residual lipid fraction which could influence their techno-functional properties. Thus, this study aims to investigate the impact of MPIs with different lipid contents (partially or totally defatted) on lipid and protein profiles, protein structure and techno-functional properties. These different MPIs were obtained after a defatting step by cold centrifugation (MPIC), hexane (MPIS) and chloroform-methanol (MPIF).
The use of chloroform-methanol was the most efficient method since no residual lipids were detected in isolates. Higher proportions of linoleic and stearic acids were detected in the lipid fraction recovered when chloroform-methanol was used (31.81 and 5.07 %) compared to hexane (28.76 and 4.58 %) and cold centrifugation (22.62 and 2.24 %). No difference was obtained between the three-defatting method in terms of protein profile whereas a unimodal population of smaller particles was observed after using solvents (MPIS and MPIF). Surface hydrophobicity was lower for MPIS and MPIF compared to MPIC. The solubility of the isolates was similar, except at pH 6 where MPIF (49.74 %) was lower than the others (57.62 and 59.28 % for MPIC and MPIS, respectively). The MPIF isolate exhibited the highest foaming capacity (FC) at pH 9 with a firm and fluffy texture although FC of 597.50 and 58.85 % were calculated for MPIS and MPIC, respectively. Additionally, foaming stability (FS) at 30 min was higher for MPIF compared to MPIS and MPIC.
Consequently, the residual lipid fraction in MPIs impacted their protein structures and foaming properties. Thus, a control of this residual lipid fraction is crucial to develop ingredients with improved techno-functionalities. The next step will involve an evaluation of the impact of the residual lipids on the emulsifying properties.