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CHEMICAL WEEKLY NOVEMBER 18, 2003 ■ 183

Water Based FragrancesSITARAM DIXIT

Senior Manager — Fragrance ApplicationsInternational Flavours & Fragrances India Limited

I n today’s time, prosperity and comfortable livingare closely related. The quality of the fragrance istaken for granted as good if the brand is well

known and the container elegant.

Personal fragrance is no longer a luxury today, withboth men and women considering it as a daily com-modity to improve aesthetics. Developing an attrac-tive fragrance is never a matter of chance. Creativeimagination, systematic study of the behaviour ofodorants, combined with years of practice is requiredto develop a product designed to appeal to others. Useof top quality raw materials having absolute purity ofodour is a prerequisite.

Consideration must also be given to other factorslike environment, government rules and regulation andother subjective influences that directly affect fragrancedevelopment, manufacturing and marketing. Patienceand time are required to create a fragrance, to evalu-ate, and make changes necessary to balance it beforelaunch. Only a fragrance that has attained the desireddegree of perfection demanded by today’s discrimi-nating consumer will make it to the best seller list andconquer the world.

A cursory look at the world fragrance market willreveal the trend of alcohol-free fragrance sprays be-coming popular. The basic underlying reason for thisglobal market trend might be different. However,we cannot ignore the fact that aqueous dispersionsof fragrances are becoming popular in the worldmarket. Volatile Organic Chemical (VOC) restric-tions in the US, environmental pressures in Europe,religious constraints in Islamic nations, and politi-cal climate coupled with Indian government restric-tion of alcohol usage in consumer products hashelped to create this new market segment of non-alcoholic fine fragrances.

Use of water as a solvent in place of alcohol has itslimitations. The biggest constraint with water basedfragrances, is our inherent desire to achieve near iden-

tical drying effect, odour diffusion, application me-thods, appearance and skin feel in comparison to con-ventional alcoholic fragrances.

The limitations of water as a solvent are equally di-vided on both the manufacturer and the user. Oil basedfragrances, although present in the market, is not verypopular, and is limited to a small section of the popu-lace. Microemulsion technology is one route to realisea clear to opalescent solution of the fragrance oil inwater. Water based fine fragrance formulations largelyconsist of the fragrance oil, surfactant blends and otherminor additives like actives, UV absorbers, antioxi-dants, preservatives, colour, etc.

Marvin Balsam almost three decades ago pointedout that solubilisation of fragrance oil is easier if theperfumer avoids use of terpenes, sesquiterpenes,resinoids, crystalline ingredients and materials that havemore than 12 carbon atoms (e.g. benzyl benzoate orsalicylate).

Although in the pure form the above materials aredifficult to dissolve, they generally form stable soluteswhen used as one of the many ingredients in fragranceoil. Avoiding use of limonene and pinenes does notsignificantly change the odour quality of the fragrancecreated. However, it enables the fragrance compoundedto be used at a higher level, as the solubility is signifi-cantly greater.

One important observation to be noted is that natu-ral essential oils comprising of various ingredientsshow a high solubility in comparison to pure chemi-cals. In short, creative expertise, patience, and timeare needed to formulate a fragrance if solubility, inaddition to a high degree of odour perfection, is de-sired.

To formulate water based fragrances we have to takerecourse to using solubiliser surfactants. Lower thelever of solubilisers, lesser the stickiness perceived inthe final product. The optimum quantity and type ofthe solubilisers used is therefore an important factor in

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the formulation. A variety of solubilisers are availablefor use. However, comparative solubilisation data isnot available. Solubiliser requirement also changes withspecific fragrance types, making it all the more diffi-cult to choose the correct one. Only by tedious trialsand expertise gained thereby, an optimum quantity ofthe selected solubiliser can be determined.

Typical solubilisers popular with development chemists are:

• PEG 40 Hydrogenated Castor oil isostearate.

• PEG 60 Hydrogenated Castor oil.

• Nonyl Phenol (10M Ethoxylate)

• Polysorbate 20

• Polysorbate 80

• Cateth 20

• Ethoxylated alcohol

• Trideceth -11

• Fatty alcohol ethoxylate

• PPG 2 Ceteareth 9

• Laureth –35

• Cocodimethyl amine oxide.

Commercial fine fragrances normally have 5 to 25%of fragrance oil dissolved in a solvent. Experience in-dicates that to get an aqueous fragrance, 1 to 2 timesthe weight of the solubilisers is required to achieve astable clear solution. A typical spray fragrance formu-lation will look like this:

Fragrance (deterpenated) 6.0

Solubilisers 9.0

PPG 20 (Antifoam) 0.02

Preservatives/Antioxidants/UV absorbers/Colour q.s.

De-ionised water to 100

Normally the aqueous fragrances obtained have afaint opalescence, the microemulsion remaining clearbetween 10-40°C. As the fragrance oil percentage in-creases, the solubiliser requirement will also changefor the higher. Sometimes, higher proportion of

solubilisers gives a viscous product not suitable foruse in pump spray dispensers. Another important pointto be noted is the tendency of the final product to foamin the bottle when relatively high concentration ofsolubilisers is used in the product formula.

Small amounts of silicone anti-foaming agentswhen added can reduce high foaming; however theclarity of the solution is disturbed with an increase inopalescence. Use of high molecular weightpolypropylene glycol (20M) is better suited for thispurpose instead.

Solubilisers used generally are non-ionic surfactantswith polyoxyethylene chains. They all exhibit inversesolubility coefficients with temperature (i.e. higher thetemperature, lower the solubility). Lower the solubi-lity, lesser the effectiveness of the solubiliser.Solubilisers perform better at lower temperature. How-ever lower temperature limit lies between 5-15 °C justas the higher temperature when the products becomeinsoluble ranges between 35-80°C.

Generally, all fragrance microemulsions are ther-modynamically stable. A fragrance solution that is clearat room temperature and becoming cloudy at 50°C orseparate at 10°C will again become clear when tem-perature is brought back to room temperature. This ruleis general and only storage studies at various tempera-ture conditions and cycles can provide data on longterm adverse effects on emulsion consistency and prod-uct stability.

Contrary to general belief that only alcoholic fra-grances give better lift to a fine fragrance, water basedproducts also give good diffusion, but after the elapseof a first few seconds of application on our skin.Substantivity and retentivity of the fragrance is com-parable to the one obtained by alcoholic fragrances.Although water based fragrances do not necessarilygive rise to changes to odour profile, it is essential tocontrol the residual acidity and alkalinity in the finalproduct.

The pH of the formulation should be maintainedbetween 5 and 6. Utmost care has to be taken whenuse of buffer is resorted to maintain pH levels, as somebuffers (e.g., EDTA-Na2) themselves can catalysemalodour development in the product.

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When water based fragrances have a viscosity ofmore than 15cps then the pumps used for alcoholicfine fragrances are not suitable and special nylon basedpumps may have to be designed.

Water has a slower rate of evaporation as comparedto alcohol. This apparent disadvantage can be addressedto by lowering the pump capacity from the usual150 µl to 100µl. The reduced capacity will allow thepump to give a finer spray, which, in turn, will give abetter spread on the skin. In any case, the consumershould also be tolerant while using water based fra-grance sprays, as it will take a longer time to dry.

Use of solubilisers in the formulation can give a feel-ing of stickiness during the transitory drying period.However, if correct solubilisers are chosen and levelsoptimised, excessive stickiness can be avoided. More-over, this inherent disadvantage can become a market-ing claim if consumers perceive a moisturising effectduring use. Although solubilisers are specific for a fra-grance oil chosen, solubilisers having an HLB valueof 11 is optimum. This is achieved by blendingsolubilisers having lower and higher HLB values. If

products with higher fragrance oil concentration arerequired then the solubiliser requirement will be higher.The product will naturally be in the form of a viscouscream or lotion. Sometimes solubilisers alone are notsufficient and colloids or soluble acrylic resins may benecessary for solubilising the fragrance oil.

Although water-based fragrance do offer some ad-vantages to conventional alcoholic fragrances, it is alsonecessary to adhere to some specific requirements.Optimum olfactive stability is achieved by minimis-ing the exposure of the final product to air and oxygenas this invariably leads to rancidity on ageing, even ifantioxidants are used in the preparation. Emulsifierswith oleate or ricinolate groups is avoided, as they areprone to get rancid on ageing, especially when the topnotes of the fragrance are reduced by natural evapora-tion.

Creating a successful water based fragrance is a timeconsuming process. Joint effort and co-operation bet-ween the perfumer, development chemist, and the sur-factant supplier is of paramount importance if one hasto taste success.