Does the extraction method impact on the composition of the lipid fraction obtained from Acheta domesticus flour?

The aim of this preliminary research work was to quantify and characterize the lipid fraction from flour samples obtained from Acheta domesticus, used as alternative high-protein source for animal feeding. Adult cricket’s flour lipids were extracted with three different methods (Folch, Soxhlet and CO2 supercritical fluid extraction (CO2-SFE; 350 bar, 45ºC, 3h)); their total lipid profile and total fatty acid (FA) composition were determined. All tested methods were equally efficient with respect to lipid extraction (17.5-20.5% of extracted lipids). Regarding the total lipid profile, triacylglycerols (TAG) were the most representative class (78.10-90.06%), followed by diacylglycerols (DAG) (6.13-14.89%) and free fatty acids (FFA) (1.45-2.24%); the Folch extract was richer in DAG and FFA than the other 2 lipid extracts, which could be mainly attributed to the different solvent polarity. As for the composition of total FA, the distribution of the FA classes was similar among the extracts; the most abundant FA class were the saturated FA (SFA) (56.02-57.41%) (mainly palmitic acid), followed by monounsaturated FA (MUFA) (37.06-38.96%) (mainly oleic acid) and polyunsaturated FA (PUFA) (3.95-4.10%) (mostly gamma linolenic acid). The unsaturated FA (UFA)/SFA and PUFA/SFA ratios were similar (0.74-0.86 and 0.07-0.10, respectively) in all lipid extracts, while the n-6/n-3 ratio varied between 3.16 and 3.44. In conclusion, the lipid extraction methods here tested were all equally efficient, but relevant differences among lipid classes were found. If these compositional differences are considered, the obtained oil could be addressed to different applications, such as livestock feed formulation, food or cosmetic fields. Finally, it is important to highlight that, given that UFA are ≈45% of total FA, the defatting step could represent an option to improve the oxidative stability of cricket flour during storage.