Relationship between the terpene enantiomeric distribution and the growth cycle of lemon fruit and comparison of two extraction methods

Abstract

Lemon essential oil is one of the most widely used natural flavours in the food and beverage industries. Knowledge of the enantiomeric ratio in flavours has gained relevance because they may indicate differences in their organoleptic characteristics or their authenticity. The study was carried out during the growth of the lemon fruit to evaluate the possible variations of the enantiomeric ratio of four characteristic terpenes: α-pinene, β-pinene, linalool and limonene. Two extraction methods were applied to extract the terpenes: simultaneous distillation-extraction at reduced pressure (V-SDE) and solid-phase microextraction; the results were equivalent whatever the method applied. In both cases, the target compounds were obtained from the lemon peel. Enantiomeric profiles were obtained by enantioselective multi-dimensional gas chromatography-mass spectrometry (enantio-MDGC-MS). Consistent enantiomeric ratios of α-pinene, β-pinene and limonene were observed; however, the enantiomeric ratio of linalool varied significantly according to the growth stage of the lemons in a spontaneous and natural way.

Analysis of the volatile monoterpene composition of citrus essential oils by photoelectron spectroscopy employing continuously monitored dynamic headspace sampling

“…51 Likewise, when headspace pre-concentration procedures are adopted prior to presentation of the vapour for analysis, the adsorption and desorption temperatures will influence the vapour/adsorbate equilibria, and the choice and preparation of adsorbent material may introduce additional selectivity in the transfer stages. 17,[52][53][54] It is not then uncommon for relevant experimental conditions to be empirically optimised to improve the resolution (reduce co-elution) of the components at the expense of quantitative precision. Preparation for fully quantitative analysis can be an onerous procedure, 10 and the complete calibration factors are unlikely to be directly transferable to other studies.…”

“…63 Looking beyond this, photoelectron spectroscopy has the ability simultaneously to determine enantiomeric excess of the individual chiral components. Enantioselective determination of the levels of chiral volatile species in essential oils is recognised as an extremely sensitive, informative tool when seeking to establish authenticity or prove adulteration of essential oils 52,54,64 and hence would be a desirable additional capability.…”

Experimental and Molecular Insights into Efficient Deterpenation of Essential Oil Intensified by Extraction with Deep Eutectic Solvent

“…Therefore, the concentration of citral (i.e., deterpenation) is crucial for the improvement of the quality of lemon essential oil. 17 The current methods employed for the deterpenation of lemon essential oil encompass vacuum distillation, 18,19 supercritical extraction, 20−22 and liquid−liquid extraction. 23,24 The distillation process is not suitable for the deterpenation of lemon essential oil with a low concentration of terpenoids due to the high energy requirement for vaporizing a large amount of limonene and discharging it from the top of the tower as well as the potential degradation of temperature-sensitive components caused by prolonged exposure.…”

“…The current methods employed for the deterpenation of lemon essential oil encompass vacuum distillation, , supercritical extraction, − and liquid–liquid extraction. , The distillation process is not suitable for the deterpenation of lemon essential oil with a low concentration of terpenoids due to the high energy requirement for vaporizing a large amount of limonene and discharging it from the top of the tower as well as the potential degradation of temperature-sensitive components caused by prolonged exposure. Supercritical extraction involves stricter operating conditions such as temperature or pressure, which may compromise the flavor of the essential oil during separation and require higher investment costs for equipment and present operational challenges .…”