Physicochemical characterization and comparison between harvests of oil obtained from Speciomerus rufcornis larvae developed in tucumã (Astrocaryum vulgare) seeds

In Northern Brazil, particularly on Marajó Island (Pará), traditional communities consume the larvae of the beetle Speciomerus ruficornis, which develop inside tucumã seeds (Astrocaryum vulgare). These larvae are eaten raw, fried, or processed to obtain an oil traditionally used in local cuisine. The present study aimed to characterize the physicochemical properties of Speciomerus ruficornis larvae oil (SRO), compare oils obtained from different harvests, and evaluate storage stability based on selected quality parameters. The oils were obtained through artisanal extraction in the community of Vila do Pesqueiro, municipality of Soure (Marajó Island, Pará), from tucumã fruits containing larvae collected in the local Extractive Reserve. The samples analyzed were SRO-produced year/analyzed year: SRO-2022/2023, SRO-2023/2023, SRO-2022/2025, and SRO-2023/2025. Oils were stored under controlled room temperature (20 °C), with SRO-2022 kept in high-density polyethylene bottle and SRO-2023 in amber glass bottle. The parameters analyzed included total lipid fraction (AOCS Am 5-04), water content (AOCS Ca 2e-84), mono-, di-, and triacylglycerol (MAG, DAG, TAG) contents (AOCS Cd 11b-91), fatty acid profile (AOCS Ce 1-62), and free fatty acid (FFA) content (AOCS Cd 3d-63), expressed as the average molar mass of the fatty acids constituting the oils. SRO samples exhibited exceptionally high lipid content (>98%) and extremely low water content (0.05–0.12%), highlighting the concentrated and stable nature of the oil. The oils were predominantly composed of triacylglycerols (TAG, 96–96.6%), with minor proportions of diacylglycerols (DAG, 1.90–2.57%), monoacylglycerols (MAG, 0.39–0.93%), and free fatty acids (FFA, 0.55–0.81%). Acidity remained low (1.30–1.92 mg KOH/g), slightly increasing in older or longer-stored samples. The fatty acid profile was dominated by medium-chain saturated fatty acids, mainly lauric (C12:0, 26.92–30.22%) and myristic (C14:0, 19.26–20.92%), with lower amounts of palmitic (C16:0, 14.92–16.31%) and stearic (C18:0, 3.25–4.03%), and minor unsaturated fractions oleic (C18:1, 26.26–29.20%) and linoleic (C18:2, 3.83–4.34%). Slight variations between harvests and storage periods were observed, but the overall composition remained consistent. Low standard deviations for all parameters indicate high reproducibility and sample homogeneity. Overall, these findings demonstrate that SRO is a highly pure, stable, and functional oil, with triacylglycerols as the major component, minimal hydrolysis, and high thermal and oxidative stability, supporting its potential for long-term storage and culinary and industrial applications. The results contribute to understanding the nutritional and technological potential of SRO, supporting its valorization as a traditional food resource and providing insights into its stability during storage.