WINTERIZATION

What is winterization?

According to the introduction of Ranchana et al. (2017), the concrete undergoes a series of “washings” with a polar solvent such as ethanol; the polarity of the ethanol allows the volatile aromatics to be extracted from the concrete while leaving behind the non-polar plant waxes, which do not dissolve in ethanol. Finally, they write, the ethanol is evaporated to leave behind the absolute, which “typically” has ethanol remaining in it and “sometimes” a trace of hexane.

According to EFSA (FEEDAP, 2021, opinion 6891), the wax content of cold-pressed oils is commonly reduced by “winterisation” (de-waxing).

Where does the step sit in the making of an absolute?

The introduction of Baranauskienė et al. (2022) describes absolutes as produced industrially by extraction with an organic solvent (hexane or another), evaporation of that solvent, with some loss of volatile compounds, and removal of waxes.

What about labdanum resin?

According to Frazão et al. (2022), citing their reference 3, although waxes “may not be considered” constituents of labdanum resin, they are extracted together with it by organic solvents such as chloroform.

How did individual studies carry out the step?

Rose concretes (Erbaş and Baydar, 2016)

Erbaş and Baydar (2016) worked on concretes obtained with five solvents from fresh, hand-picked flowers of Rosa × damascena Herrm. (Rosa damascena Mill. in the source), from GULAR, Isparta (Turkey), harvested in May–June 2011. In their study, the concretes were dissolved in 96 % ethanol and stirred vigorously at 35–40 °C for 8 h. The alcoholic solution was then chilled at −20 °C for 8 h in a deep freezer, and the crystallised stearoptenes were filtered through filter paper under vacuum; the passage ends on a citation of their reference 9. For the absolute, the concretes were treated with ethanol at approximately 10 times their own weight, in a passage that cites their reference 8. The stearoptenes left on the filter paper were redissolved in 50 mL of ethanol (96 % purity) to obtain liquid filtrates. To yield the absolute, the filtrate was left overnight in a deep freezer, then evaporated under vacuum in a rotary evaporator at 55 °C to remove the ethanol and water. The article does not state whether these filtrates were combined with the first filtrate.

Jasmine concretes (Yassen et al., 2026)

Yassen et al. (2026) studied the concretes of four species grown in Egypt and harvested in August, Jasminum sambac (L.) Aiton, Jasminum azoricum L., Jasminum grandiflorum L. and Jasminum multiflorum (Burm.f.) Andrews, together with a purchased concrete of J. grandiflorum. In their study, jasmine absolute was extracted from the concrete with 95 % ethanol, washed three times and filtered at −80 °C to remove wax. The absolute was obtained by evaporating the alcohol at temperatures below 40 °C.

Labdanum resin (Frazão et al., 2022)

Frazão et al. (2022) worked on labdanum resin from Cistus ladanifer subsp. ladanifer (the source’s name in section 3.1; Cistus ladanifer L. in its title and introduction), obtained by the “Andalusian process” from terminal leafy stems of plants from Penha Garcia (Portugal), collected in August 2018. Their labdanum absolute was obtained by removing “waxes” from the resin following the method of Vogt et al.: at most one gram of resin was dissolved in 20 mL of methanol in an ultrasound bath, left at −20 °C overnight, then centrifuged at 3030× g at −5 °C for 15 min. The procedure was repeated three times and the supernatants were combined, over three independent extractions.

Fat from enfleurage (Soe’eib et al., 2016)

In the enfleurage study by Soe’eib et al. (2016), on jasmine, rose and frangipani flowers named without binomials, the fat was extracted at the end of enfleurage with alcohol at an alcohol-to-fat ratio of 1:1. The alcohol–fat mixture was kept in a refrigerator for 24 h, then separated on filter paper; the source calls the filtrate of alcohol and essential oils “pomade”. The source does not give the refrigerator temperature.

What did the studies measure in concretes and absolutes?

In the rose study

In Erbaş and Baydar (2016), the volatile compounds of the concretes obtained with diethyl ether, petroleum ether, cyclohexane, chloroform and n-hexane were rich in monoterpene and aromatic alcohols, such as phenylethyl alcohol (16.6–23.3 %), citronellol (3.8–5.4 %), nerol (2.2–3.3 %) and geraniol (5.0–7.4 %). They were also rich in long-chain hydrocarbons, such as nonacosane (19.2–38.5 %), hexadecane (6.1–17.3 %), eicosane (0.0–13.1 %) and nonadecane (0.0–11.8 %). Measured by GC-FID, the major compounds of the absolutes from these concretes were phenylethyl alcohol (35.2–38.4 %), hexadecane (28.3–36.3 %), geraniol (6.9–10.8 %), citronellol (5.6–8.4 %) and nerol (3.4–5.0 %). The authors do not themselves compare these contents with those of the concretes. The number of compounds detected in the absolutes was 10 to 11, fewer than in the concretes. Nonacosane, the main compound of the rose concretes, was not detected in the absolutes. According to the authors, this compound is “probably” not soluble in ethyl alcohol and stays in the solid residue by-product. The article is inconsistent about its tables: the text refers the GC-FID results of the concretes and absolutes to Tables 4 and 5, while the concretes are in Table 3 and the absolutes in Table 4, and the passage on the absolutes cites a Table 5 that the article does not contain.

In the jasmine study

In Yassen et al. (2026), aliphatic hydrocarbons (alkanes) accounted for approximately 66.3 % of the J. sambac concrete and 25.78 % of the J. sambac absolute (GC–MS, relative percentages). In the other concretes, aliphatic hydrocarbons accounted for about 48.81 % (J. multiflorum), 43.91 % (J. grandiflorum), 35.34 % (J. azoricum) and 39.65 % (purchased J. grandiflorum). The corresponding absolutes contained less of this class: 8.54 % (J. azoricum), 2.98 % (J. grandiflorum), 4.43 % (J. multiflorum) and 0.2 % (purchased J. grandiflorum). The source does not attribute these differences to the wax-removal step.

In the lavender absolutes

Nedeltcheva-Antonova et al. (2022) studied industrial absolutes of Lavandula angustifolia Mill. supplied by BulPhyto Oils Ltd. (harvests 2008–2017); LA1 to LA6 were obtained from concretes from the Zelenikovo area. The source does not write the author of the species name the same way throughout: “Mill.” in the abstract, “L.” in section 2.1. In the producer’s description given by the authors, lavender concrete is extracted from fresh, unsteamed flower mass treated with a non-polar solvent (petroleum ether or n-hexane). It is described as a yellow-green to green-brown jelly-like mass containing over 65 % absolute. The main constituents of the seven absolutes studied (LA1 to LA7) are terpene compounds and aliphatics (hydrocarbons, ketones, esters, etc.), and fatty acids, higher alcohols and waxes were also found. According to the authors, fatty acids, higher alcohols and aldehydes and waxes, naturally present in the lavender inflorescence, are normally not observed in the essential oil because of their low volatility, but were found in relatively high amounts in these absolutes. The source does not describe the wax-removal step of these absolutes, and does not quantify these compounds in that passage.

What does a study of CO2 extracts say about waxes?

Baranauskienė et al. (2022) extracted flowers of Narcissus poeticus L. with supercritical CO2 at 12 to 48 MPa, with or without 5 % ethanol as co-solvent, and carried out no dewaxing. According to their abstract, aliphatic hydrocarbons (waxes) made up the main part of the extracts (41.47 to 54.93 %), the percentage of alkanes being lowest with 5 % EtOH. The abstract adds that the wax fraction “may be removed” to separate higher-value fragrance materials. In the body of the article, saturated hydrocarbons (n-alkanes) are described as a very large fraction (41.47 to 54.93 %) of the GC-detectable volatiles of the narcissus lipophilic fraction, an amount that “could be reduced” by conventional dewaxing procedures. In their conclusions, the authors describe the large wax fraction of the extracts as not desirable in the production of higher-quality fragrance ingredients. Adding ethanol as co-solvent reduced the percentage of higher alkanes, while the amount of benzyl aromatics recovered increased; this reduction comes from the co-solvent, not from a removal of waxes.

References

• Yassen M.S., Ayoub I.M., El-Ahmady S.H., Singab A.N.B., « Comparative analysis of flower volatiles from four Jasminum species growing in Egypt using multivariate analysis », Scientific Reports 2026;16:8947, doi:10.1038/s41598-026-39688-w — https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=pmc&id=12988214&rettype=xml
• Ranchana P., Ganga M., Jawaharlal M., Kannan M., « Characterization of Volatile Compounds from the Concrete of Jasminum grandiflorum Flowers », International Journal of Current Microbiology and Applied Sciences 2017;6(7):1883-1891, doi:10.20546/ijcmas.2017.607.225 — https://www.ijcmas.com/6-7-2017/P.%20Ranchana%2C%20et%20al.pdf
• Erbaş S., Baydar H., « Variation in Scent Compounds of Oil-Bearing Rose (Rosa damascena Mill.) Produced by Headspace Solid Phase Microextraction, Hydrodistillation and Solvent Extraction », Records of Natural Products 2016;10(5):555-565 — https://www.acgpubs.org/uploads/articles/pdfs/2018080807064667-RNP-1412-058.pdf
• Nedeltcheva-Antonova D., Gechovska K., Bozhanov S., Antonov L., « Exploring the Chemical Composition of Bulgarian Lavender Absolute (Lavandula angustifolia Mill.) by GC/MS and GC-FID », Plants 2022;11(22):3150, doi:10.3390/plants11223150 — https://www.ebi.ac.uk/europepmc/webservices/rest/PMC9692913/fullTextXML
• Baranauskienė R., Venskutonis P.R., « Supercritical CO2 Extraction of Narcissus poeticus L. Flowers for the Isolation of Volatile Fragrance Compounds », Molecules 2022;27(2):353, doi:10.3390/molecules27020353 — https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=pmc&id=8782035&rettype=xml
• Frazão D.F., Martins-Gomes C., Steck J.L., Keller J., Delgado F. et al., « Labdanum Resin from Cistus ladanifer L.: A Natural and Sustainable Ingredient for Skin Care Cosmetics with Relevant Cosmeceutical Bioactivities », Plants 2022;11(11):1477, doi:10.3390/plants11111477 — https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=pmc&id=9183103&rettype=xml
• Soe’eib S., Asri N.P., A.S. Dwi Saptati N.H., Diah Agustina P., « Enfleurage Essential Oil from Jasmine and Rose Using Cold Fat Adsorbent », Jurnal Ilmiah Widya Teknik 2016;15(1):58-61 — https://journal.ukwms.ac.id/index.php/teknik/article/download/1525/pdf
• EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP), « Safety and efficacy of feed additives consisting of expressed sweet orange peel oil and its fractions from Citrus sinensis (L.) Osbeck for use in all animal species (FEFANA asbl) », EFSA Journal 2021;19(11):e06891, doi:10.2903/j.efsa.2021.6891 — https://www.ebi.ac.uk/europepmc/webservices/rest/PMC8603005/fullTextXML
• Govaerts R. (ed.), World Checklist of Vascular Plants (WCVP), Royal Botanic Gardens, Kew — https://sftp.kew.org/pub/data-repositories/WCVP/wcvp.zip