FUNCTIONAL INGREDIENTS
How Polycitronellol enhances fragrances
Delano Wood, Tania Salam, Patrick Foley - P2 Science Marc de Mul - Measured Innovation
By their nature, fragrances are fleeting. Their purpose is to evaporate and reach the olfactory receptors in our nasal passages. Yet product designers are often aiming for a persistent scent that does not dissipate after initial perception. This can be achieved in three ways –
continuously generating new fragrance molecules, as flowers do; controlling release of the fragrance molecules by encapsulation or other means; or lowering the vapour pressure of the fragrance ingredients, so that they do not volatilize as quickly. A fine fragrance is generally composed of
top, middle, and bottom notes, along with a volatile solvent (often ethanol) and a fragrance fixative system. After application to skin, the solvent and top notes evaporate quickly, leaving behind the middle and bottom notes and the fragrance fixative. The rate of evaporation of a fragrance
component is proportional to its partial vapour pressure, which is proportional to its concentration in the mixture according to Henry’s Law, first formulated by William Henry in an 1803 publication.1 This law applies to dilute solutions of
volatile ingredients. In concentrated fragrance mixtures, fragrance ingredients interact with the other mixture components, which affects their vapour pressure. These interactions can be described in terms of the thermodynamic activity coefficients of the individual ingredients.2 The activity coefficients can be calculated
with interaction models such as UNIFAC, UNIQUAC, and COSMO-RS. Such models calculate the activity coefficients based on the
contributions of the chemical composition of an ingredient and the entropy of mixing due to an ingredient’s molecular shape. In an evaporating fragrance, the mixture
composition changes, which changes the ingredient activities. The partial vapour pressures of each ingredient will change with the mixture composition. The function of a fragrance fixative is to reduce the partial vapour pressures of the remaining fragrance components on skin by decreasing their activity coefficients.
This means diluting them and altering
their intermolecular interactions. This lowers the evaporation rate of those fragrance components, thus prolonging their presence.
TABLE 1: MODEL EAU DE TOILETTE FORMULATION WITH DIFFERENT FRAGRANCE FIXATIVES (POLYCITRONELLOL, SUCROSE ACETATE ISOBUTYRATE (SAIB), GLUCAM P20, TRIETHYL CITRATE (TEC))
Ethanol (192 proof) DI Water
Fragrance (Dihydromyrcenol, Carvone, Anthamber) Fixatives
Control (no fixative) 88% 5% 7% -
With fragrance fixative 78% 5% 7%
10%
TABLE 2: MODEL EAU DE TOILETTE FORMULATION WITH DIFFERENT LEVELS OF POLYCITRONELLOL BETWEEN 0 AND 10%. NOTE: ANTHAMBER WAS OMITTED FROM THE MODEL FRAGRANCE FOR THESE TESTS
Polycitronellol DI Water
Fragrance (Dihydromyrcenol, Carvone) Ethanol (192 proof)
www.personalcaremagazine.com
Amount in formula 0-10% 5%
4.7% q.s.
An effective fragrance fixative slows
evaporation of the top and middle notes throughout their residence time on skin. The fixative should provide good solubility to the fragrance components as they progressively become more concentrated. The fixative itself should be non-volatile and odourless or nearly so – if the fixative has a perceptible scent, it needs to be integrated into the overall fragrance profile. Preferred fixatives dissolve fragrance ingredients without forming a sticky or greasy film on the skin.3 Lowering vapour pressure and hence
volatility is not the whole story, however, because some fragrance ingredients can also be absorbed into the skin.4, 5
Most fragrance
fixatives have negligible skin absorption. They may form an oily film on the skin after most of the fragrance has evaporated. If present, this hydrophobic film can further retard evaporation of the remaining fragrance ingredients – the
September 2024 PERSONAL CARE ABSTRACT
Citropol® F (Polycitronellol) is a new fragrance enhancer derived from renewable sources using a process based on the principles of green chemistry. Using gas chromatography measurements and sensory observations, this article shows that this material prolongs the duration of fragrance perception more than competitive alternatives.
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