Key Points
· A recent study used gas chromatography–ion mobility spectrometry (GC-IMS) to analyze the volatile organic compounds (VOCs) of olive oil extracted from eight different fruit maturity indices (MIs) of Koroneiki olives. They identified 33 VOCs (alcohols, esters, aldehydes, ketones, acids, and others) and screened 20 differential markers for key flavors. This allowed them to effectively distinguish oils from different MIs, highlighting the importance of VOCs in defining olive oil quality.
· The researchers found that the oil samples from the seventh maturity index (mid-November harvest) exhibited significant differences from the others, suggesting that the oil’s VOC profile can serve as an indicator to determine the optimal harvest time. This is crucial for maximizing oil quality and ensuring desirable sensory properties.
· The researchers acknowledged limitations in their GC-IMS database, which hindered the complete classification of some substances. They recommended updating the database, correlating GC-IMS data with chemical structure and bioactivity databases, and further comparing unidentified substances to improve accuracy and reliability in future studies.
A study conducted by the College of Life Science at Northwest Normal University (Lanzhou, China) aimed to determine the optimal harvest period of olives by distinguishing the olive oils with different fruit maturity indices. Gas chromatography ion-mobility spectrometry (GC-IMS) technology was employed to qualitatively and differently analyze the volatile organic compounds (VOCs) of olive oil extracted from eight MIs of Koroneiki olive fruits. A paper based on this study was published in the Journal of the Science of Food and Agriculture (1).
A significant oil tree crop that has a wide distribution in Spain, Italy, Greece, Turkey, and other coastal countries, the olive tree plantation industry in China has flourished in the provinces of Gansu, Sichuan, Hubei, Chongqing, and Yunnan. This success has been attributed not only to achieving high yields but also to the cultivation of exceptional olive cultivars that are well-suited to the local environment (1).
Olive oil, obtained by pressing whole olives and extracting the oil, is commonly used in cooking for frying foods, as a condiment, or as a salad dressing. It can also be found in some cosmetics, pharmaceuticals, soaps, and fuels for traditional oil lamps, as well as utilized in various religious practices (2). Commonly referred to as “liquid gold” and “queen of vegetable oils” (3), olive oil is abundant in oleic acid, which reduces cholesterol levels and plays a crucial role in effectively preventing coronary heart disease and cardiovascular disease (4). In addition, it contains linolenic acid, linoleic acid, and other unsaturated fatty acids, along with abundant fat-soluble vitamins, as well as other plant components, such as polyphenols and sterols (5,6) which have antioxidant effects by removing free radicals in the body, phytosterols have anticancer activity (7). Olive oil, therefore, not only possesses a high nutritional value comparable to other edible vegetable oils, but it also finds extensive applications in various domains such as beauty care, medicine, textiles, and chemicals (8).
The harvesting period of olive fruits is a crucial factor which influences the resulting oil’s quality. Furthermore, oils produced from various olive cultivars with different MIs also exhibit distinct quality characteristics. The sensory properties of olive oil are greatly influenced by its VOCs greatly influence olive oil’s sensory properties, contributing not only to the flavor variations, but also play a significant role in its quality, thus offering the potential of being an indicator determining the optimal time for olive harvest (9).
Fresh Koroneiki olive fruits were collected from the Germplasm Resource Gene Bank at the Olive Research Institute in Longnan City, Gansu Province, between September and November 2021 for this experiment, and oil from eight maturity indices of the fruits were extracted directly from the fruits using physical pressing. GC-IMS analysis revealed that 40 signal peaks were isolated in these oils with different maturity indices, and 33 VOCs were identified. These include seven kinds of alcohols, seven kinds of esters, six kinds of aldehydes, five kinds of ketones, two kinds of acids, and two kinds of olefins, as well as four other compounds. A total of 20 differential markers for key flavors, with variable importance in the projection (VIP) > 1, were screened out by orthogonal partial least squares-discriminant analysis (OPLS-DA). The results showed that the olive oil samples of the seventh maturity index (mid-November) had significant differences from the other oils, suggesting that oils with different maturity indices can be effectively distinguished (1).
However, the researchers offer the caveat that further research is still required to recognize certain as-yet unidentified substances, as the current limitations of the GC-IMS database hamper the full classification of these materials, and recommend the adoption of these strategies to address this issue and enhance the accuracy and reliability of their identification:
- Updating the database to incorporate additional information about the as-yet-unidentified substances
- Conducting correlation analyses between the GC-IMS data and various databases (such as chemical structure databases and bioactivity databases）
- Identifying potential unknown substances through comparison and matching (1).
References
1. Wang, H. M.; Zhang, H. J.; Ma, J. Y. et al. Analysis of Volatile Organic Compounds in Olive Oil of 'Koroneiki' with Different Maturity Indices by GC-IMS. J. Oleo Sci. 2025, 74 (6), 503-512. DOI: 10.5650/jos.ess24339
2. Olive oil. Wikipedia. https://en.wikipedia.org/wiki/Olive_oil (accessed 2025-06-05).
3. Jimenez-Lopez, C.; Carpena, M.; Lourenço-Lopes, C. et al. Bioactive Compounds and Quality of Extra Virgin Olive Oil. Foods 2020, 9 (8), 1014. DOI: 10.3390/foods9081014
4. Martínez-González, M. A.; Sayón-Orea, C.; Bullón-Vela, V. et al. Effect of Olive Oil Consumption on Cardiovascular Disease, Cancer, Type 2 Diabetes, and All-Cause Mortality: A Systematic Review and Meta-Analysis. Clin. Nutr. 2022, 41 (12), 2659-2682. DOI: 10.1016/j.clnu.2022.10.001
5. Gorzynik-Debicka, M.; Przychodzen, P.; Cappello, F. et al. Potential Health Benefits of Olive Oil and Plant Polyphenols. Int. J. Mol. Sci. 2018, 19 (3), 686. DOI: 10.3390/ijms19030686
6. Yu, L.; Wang. Y.; Wu, G. et al. Chemical and Volatile Characteristics of Olive Oils Extracted from Four Varieties Grown in Southwest of China. Food Res. Int. 2021, 140, 109987. DOI: 10.1016/j.foodres.2020.109987
7. Sun, S.; Xie, Y.; Zhao, W. et al. Progress in Characteristic Chemistry Compositions and Flavor Compounds of Olive Oils. Journal of Henan University of Technology (Natural Science Edition) 2015,36, 113-119.
8. Gagour, J.; Hallouch, O.; Asbbane, A. et al. A Review of Recent Progresses on Olive Oil Chemical Profiling, Extraction Technology, Shelf-life, and Quality Control. Chem. Biodivers. 2024, 21 (4), e202301697.DOI: 10.1002/cbdv.202301697
9. Lukić, M.; Lukić, I.; Moslavac, T. Sterols and Triterpene Diols in Virgin Olive Oil: A Comprehensive Review on Their Properties and Significance, with a Special Emphasis on the Influence of Variety and Ripening Degree. Horticulturae 2021, 7, 493. DOI: 10.3390/horticulturae7110493
