Assessment of oil quantification methods for high oil seeds

Authors: AL-BAKRI, AHMED - University Of Kentucky; AL-AMERY, MAYTHEM - University Of Baghdad; SU, KAI - University Of Kentucky; ANDERSON, HANNAH - University Of Kentucky; GENEVE, ROBERT - University Of Kentucky; CROCKER, MARK - University Of Kentucky; TEETS, NICHOLAS - University Of Kentucky; Armstrong, Paul; KACHROO, PRADEEP - University Of Kentucky; HILDEBRAND, DAVID - University Of Kentucky

Submitted to: Analytical Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/2023
Publication Date: 4/28/2023
Citation: Al-Bakri, A., Al-Amery, M., Su, K., Anderson, H., Geneve, R., Crocker, M., Teets, N., Armstrong, P.R., Kachroo, P., Hildebrand, D. 2023. Assessment of oil quantification methods for high oil seeds. Analytical Chemistry. 50. Article 102715. https://doi.org/10.1016/j.bcab.2023.102715.
DOI: https://doi.org/10.1016/j.bcab.2023.102715

Interpretive Summary: Efficient and accurate determination of oil content in small oilseed samples is important aspect of sample evaluation for the multitude of samples breeders generate during the development of varieties. In most cases, samples are limited in size but abundant in number and thus timely and accurate measurement is important. The industry standard measurement technique is known as the Soxhlet method but requires relatively large sized samples and takes multiple extraction cycles that can take hours. This study looked at ten different efficient and inexpensive techniques for oil measurement to evaluate suitability as an alternative to the Soxhlet method. Twelve oilseed samples (comprising eleven soybean and one chia) covering an oil content range of 15.5 to 32.7% were measured using ten different methods. Of these, a physical oil extraction method, Bead Beating Extraction, was found to have the best agreement with the Soxhlet method and was the simplest, fastest and least expensive of the oil quantification methods. Other methods tested provided adequate to good results while the Nile red fluorescence technique performed poorly. These results will give guidance to breeders and geneticists on method accuracy and allow users to select the best method for the equipment and personnel they may have available.

Technical Abstract: Efficient and accurate determination of oil content in small oilseed samples is important. This study evaluated ten different methods of seed oil extraction and quantification, including methods that have not previously been applied to oilseeds. The aim of the study is to find techniques that are efficient and inexpensive to perform with small amounts of seeds. The Soxhlet method was used as a standard control. Twelve oilseed samples (eleven soybean and one chia) covering an oil content range of 15.5 to 32.7% (dry weight) were used. The Folch technique provided a higher percentage of oil extraction compared to Bligh and Dyer and hexane-isopropanol techniques. There was not a significant difference (P >0.05) between the Folch and Soxhlet technique. A supercritical fluid extraction method yielded lower amounts of oil extraction compared to the Soxhlet method. A Direct Transesterification (DT) with low moisture content (LMC) seeds gave higher oil levels than DT with high moisture content (HMC) seeds. A Double Direct Transesterification following the Griffiths et al. (2010) protocol, Qiao et al. (2015) protocol and a Bead Beating Extraction (BBE) protocol were highly correlated with the Soxhlet method. A Nile red fluorescence technique did not work well with oilseeds. The BBE is proposed to be the best small sample oilseed oil quantification technique as it provided results highly correlated with Soxhlet (0.88 R2) and is the simplest, fastest and least expensive of the oil quantification methods needing only mg sample sizes.