Title : Impact of seed storage and refining on oil quality from Hildegardia barteri (Mast.) Kosterm seed as biofuel feedstock
Abstract:
Bioenergy remains a cornerstone of the renewable energy mix. Coupled with the increasing cost and the environmental impacts of fossil fuel use, these have intensified the search for sustainable, lesser-used seed sources for bioenergy. For efficient conversion into power, heat, and fuels, the quality of biomass feedstock is critical. This study examined the oil yield, quality, molecular composition, and storage stability of Hildegardia barteri (kariya) seed oil as a potential biodiesel feedstock. Oil was extracted from freshly harvested seeds and seeds stored for two years using n-hexane, ethanol, and a 1:1 n-hexane–ethanol solvent mixture. The oil extracts were subjected to membrane purification using 0.45 µm microfiltration followed by 50 kDa ultrafiltration. Oil yield, tocopherol content, storage stability, molecular composition, and functional characteristics were subsequently evaluated using oil yield determination, LC-MS, and GC-MS analyses. The crude oil yield ranged from 42.20% to 71.87%, with the n-hexane–ethanol mixture producing the highest yield (71.87%). Following membrane purification, refined oil yield ranged from 35.22% to 53.13%, with the solvent mixture again producing the highest yield. The results indicate that membrane purification resulted in appreciable oil recovery while removing associated impurities. Tocopherol analysis showed higher antioxidant concentrations in oils obtained from freshly harvested seeds compared with those extracted from two-year-old stored seeds. Tocopherol concentration also varied with extraction solvent and storage temperature, generally declining during storage, particularly in oils obtained from aged seeds. GC-MS analysis revealed differences in molecular composition between oils from freshly harvested and stored seeds, with stored-seed oils showing increased proportions of unsaturated compounds, suggesting greater susceptibility to oxidative deterioration. Findings reveal that H. barteri seed oil has considerable potential as feedstock for biodiesel production. Membrane purification is also a promising pre-treatment approach for improving the quality of the oil. However, appropriate seed storage conditions and further optimization of the refining process are necessary to enhance oil stability and maximize its suitability for biodiesel production.
