Characterization, quantification and quality assessment of Avocado (Persea americana Mill.) oils

Authors: WANG, MEI - University Of Mississippi; YU, PING - Nanchang University; CHITTIBOYINA, AMAR - University Of Mississippi; CHEN, DILU - Hunan University Of Chinese Medicine; ZHAO, JIANPING - University Of Mississippi; AVULA, BHARATHI - University Of Mississippi; WANG, YAN-HONG - University Of Mississippi; KHAN, IKHLAS - University Of Mississippi

Submitted to: Molecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/2020
Publication Date: 3/24/2020
Citation: Wang, M., Yu, P., Chittiboyina, A.G., Chen, D., Zhao, J., Avula, B., Wang, Y., Khan, I.A. 2020. Characterization, quantification and quality assessment of Avocado (Persea americana Mill.) oils. Molecules. 25(6):1453. https://doi.org/10.3390/molecules25061453.
DOI: https://doi.org/10.3390/molecules25061453

Interpretive Summary: Avocado oil is traditionally extracted from the mature fruit flesh and is prized for its high nutrient value due to the substantial amounts of triglycerides and unsaturated fatty acids. Recently the popularity of avocado oil is promoted with the newly introduced avocado seed oil. However, there is neither sufficient evidence to support the claimed health benefit nor safe use of oils derived from avocado seed. The current study endeavors to establish the comprehensive profiles and quality standards of oils extracted from avocado peel, pulp and seed, as well as to identify possible adulteration. An Ultra-High-Performance Liquid Chromatography/Electrospray Ionization-Mass Spectrometry (UHPLC/ESI-MS) was developed for the quantification of 13 triglycerides in authenticated and commercial avocado oils. The precision and accuracy of the UHPLC/ESI-MS method was verified by fatty acid analysis using a Gas Chromatography/Mass Spectrometry (GC/MS) method, and the results from these two methods were in good agreement. The statistical analysis based on triglyceride and fatty acid compositional data reveled that, among the 19 commercial oils analyzed, 7 samples were adulterated with soybean/sesame oil or mislabeled. None of the oils claimed as avocado seed oil was actually derived from avocado seed.

Technical Abstract: Avocado oil is prized for its high nutrient value due to the substantial amounts of triglycerides (TGs) and unsaturated fatty acids (FAs) present in the oil. While avocado oil is traditionally extracted from mature fruit flesh, alternate sources such as avocado seed oil have recently increased in popularity. Unfortunately, there is neither sufficient evidence to support the claimed health benefit nor safe use of oils derived from these sources. To address the potential quality issue and identify possible adulteration, authenticated oils extracted from avocado peel, pulp and seed by supercritical fluid extraction, as well as commercial avocado pulp and seed oils sold in the US market were analyzed for TGs and FAs in the present study. Characterization and quantification of TGs were conducted using Ultra-High-Performance Liquid Chromatography/Electrospray Ionization-Mass Spectrometry (UHPLC/ESI-MS). Thirteen TGs containing saturated and unsaturated fatty acids in avocado oils were unambiguously identified. Compared to traditional analytical methods, which based only on the relative areas of chromatographic peaks neglecting the differences in the relative responses of each individual TG, our method improved the quantification of TGs by using the reference standards whenever possible or the reference standards with the same equivalent carbon number. To verify the precision and accuracy of the UHPLC/ESI-MS method, the hydrolysis and transesterification products of avocado oil were analyzed for fatty acid methyl esters using a Gas Chromatography/Mass Spectrometry (GC/MS) method. The concentrations of individual FA were calculated, and the results were in good agreement with the UHPLC/ESI method. Although chemical profiles of avocado oils from pulp and peel are very similar, a significant difference was observed for the seed oil. TG and FA compositional data, along with statistical analysis was able to identify the possible adulteration in the commercial oils.