Fragrance

• Aroma chemicals


  Compounds possessing a complex and distinct scent that enhances the aroma or fragrance of formulations they are infused in
• Aroma chemicals


  • Highly volatile with the ability to easily disperse any scent, which enhances the diffusive properties required to create long-lasting fragrances
  • Can be used to infuse fragrance into various products with their simple, pure, and manageable aroma
• Natural aroma chemicals


  Obtained from various plant parts including, flowers, fruits, peels, leaves, barks, seeds, woods, roots, and resinous exudates
• Terpenes


  A family of chemicals biochemically synthesized by many plants, particularly citrus species like orange and lemon
• Isoprene


  The basic building block of terpenes, with head-to-tail unions forming the larger polymer structures

  
• Terpene types


  • Monoterpene (C10H16)
  • Sesquiterpene (C15H24)
  • Diterpene (C20H32)
  • Triterpene (C30H48)

  
• Terpenes


  • Can have open or closed rings, double bonds, and readily accept hydroxy or carboxy groups
  • Many of the transitions between these forms occur easily, so it is easy to synthesize numerous derivatives with an interesting olfactory range

  
• The flat depiction of terpenes, particularly a puckered bicyclic terpene like pinene, does not do justice to the complexity of its three-dimensional structure

  
• Landmarks in the history of fragrance-related science

  • 1834: Cinnamic aldehyde isolated from cinnamon oil
  • 1837: Benzaldehyde isolated from bitter almond oil
  • 1844: Methyl salicylate identified in wintergreen oil
  • 1856: Cinnamic aldehyde synthesized
  • 1863: Benzaldehyde synthesized
  • 1868: Coumarin synthesized
  • 1876: Vanillin synthesized
  • 1888: Discovery of nitro musks
  • 1919: Linalool synthesized
  • 1923: Amyl cinnamaldehyde discovered
  • 1934: Muscone synthesized
  • 1939: Leopold Ruzicka wins Nobel Prize for Chemistry
  • 1971: Synthesis of a and b damascone

  
• Aroma raw materials


  Characterized by great chemical diversity, with the size of aroma molecules ranging from C5 to C17, and nitrogen, oxygen, and sulfur as common heteroatoms
• Osmophores


  Elements present in a molecule that are responsible for its odour
• Esters


  • The largest family of aroma chemicals
  • At high pH and elevated temperature, the reverse of the esterification (hydrolysis) reaction occurs and results in a total change in odour quality
  • Low-molecular-weight esters have a fruity odour, examples being the odours of apples (methyl butyrate) or bananas (3-methylbutyl acetate)
• Alcohols


  • Contain a hydroxyl (OH) group and can be aliphatic or aromatic
  • Phenols are very sensitive to oxidation and can undergo autoxidation, examples include vanillin, methyl salicylate, eugenol, and thymol
• Glycols


  • Like alcohols, having two or more hydroxyl groups
  • Common diluents in perfumery, i.e dipropylene glycol (DPG), propylene glycol, butylene glycol, and hexylene glycol
  • The polarity of the diluent affects solubility properties of the fragrance oil
• Aldehydes and ketones


  • Aldehydes can be aromatic or aliphatic
  • Aldehydes are easy to oxidize or reduce, and some can be oxidized in air
  • Aldehydes can condense with primary amine to form Schiff bases, an important example is hydroxycitronellal and methyl anthranilate, which yields Aurantiol
• Heterocyclics


  • Cyclic compounds that contain one or more heteroatoms: oxygen, nitrogen, or sulfur
  • Typically five- or six-member rings, and rings can be fused
  • Ring sizes are denoted by suffixes: -irane for a 3-membered ring, -etane for 4, -olane for 5, -ane for 6, and -epam for 7
  • The rings can be aromatic or nonaromatic

  
• Lactones

  Cyclic esters, common examples are p or o-hydroxy acids forming 5- or 6-member rings by intramolecular esterification

  
• Nitriles


  • Contain triple-bonded nitrogen
  • Commonly encountered in plant and animal sources, especially fruit pits and during the cooking of certain vegetables
  • Sometimes have an odour similar to their corresponding aldehyde, and are more stable than aldehydes to oxidation and extremes of pH

  
• Musks


  • Naturally derived musk is rare and expensive, so many synthetic compounds are made to satisfy the demands of perfumery
  • The first successful synthetics were nitro musks, but more recent molecules have been polycyclic musks, macrocyclic musks, and acyclic musks
• Nonionic surfactants


  • May be used as a fragrance ingredient when extra polarity is needed to make a "water-soluble" version
  • Creates a microemulsion that is visibly clear through hydrogen bonding, which can reversibly become hazy when heated
• Plant parts used to derive essential oils/fragrances

  • Flowers (e.g. rose, jasmine, carnation, clove, mimosa, rosemary, lavander)
  • Leaves (e.g. mint, Ocimum spp., lemongrass, jamrosa)
  • Leaves and stems (e.g. geranium, patchouli, petitgrain, verbena, cinnamon)
  • Bark (e.g. cinnamon, cassia, canella)
  • Wood (e.g. cedar, sandal, pine)
  • Roots (e.g. angelica, sassafras, vetiver, saussurea, valerian)
  • Seeds (e.g fennel, coriander, caraway, dill, nutmeg)
  • Fruits (bergamot, orange, lemon, juniper)
  • Rhizomes (e.g. ginger, calamus, curcuma, orris)
  • Gums or oleoresin exudations (e.g. balsam of Peru, Myroxylon balsamum, storax, myrrh, benzoin)
• Fragrance extraction processes


  • Enfleurage (cold and hot)
  • Expression or cold pressing
  • Distillation (hydrodistillation, hydro and steam distillation, direct steam distillation)
  • Extraction by volatile solvent
  • Extraction by CO2 fluid
• Cold enfleurage


  1. Spreading a layer of animal fat at room temperature on a plate surrounded by a wooden frame

  2. Flowers are first sorted to keep only the freshest, then placed manually, one by one, on the fat for about 24 hours

  3. The fat absorbs the scents of the flowers

  4. The fat is then collected and washed with alcohol to separate it from the odorous molecules and obtain a precious "ointment absolute" after evaporation
• Hot enfleurage


  Flowers are exposed to higher temperatures to extract their fragrance
• Processes of fragrance extraction


  • Enfleurage
  • Expression or cold pressing
  • Distillation (hydrodistillation, hydro and steam distillation, direct steam distillation)
  • Extraction by volatile solvent
  • Extraction by CO2 fluid
• Enfleurage


  Extraction process used for fragile flowers like jasmine, daffodil, or tuberose that cannot be heated
• Cold enfleurage


  1. Spreading a layer of animal fat at room temperature on a plate

  2. Flowers placed manually on the fat for 24 hours

  3. Fat absorbs the scents

  4. Fat collected and washed with alcohol to separate odorous molecules and obtain "ointment absolute"
• Hot enfleurage


  1. Also known as "maceration"

  2. Infusing more resistant flowers or vegetables in oils and fats made up of 75% pork and 25% beef, heated in a water bath between 40 and 60 degrees

  3. Flowers stirred in the heated fat for two hours

  4. Flowers infused for at least 24 hours and then replaced with fresh ones
• Enfleurage


  • Low yield: 1 kg of fat could absorb 3 kg of flowers
  • Manual technique requiring demanding know-how and qualified personnel
  • Very long process
  • Large number of materials required
  • Room temperature control necessary
  • Final "ointment absolute" product reserved for big perfume houses
  • Replaced by volatile solvent extraction and CO2 fluid extraction
• Expression or cold pressing

  Puncturing the skins of whole fruit or fruit peel and mechanically pressing the oil out
• Limonene


  A terpene that may be undesirable as it has minimal olfactive value and easily oxidizes into sensitizing materials
• Folding


  Process that removes most of the limonene by distillation, leaving a more concentrated product with a stronger odour value
• Steam distillation


  • Common extraction process for aroma compounds, working well for most heat-tolerant materials
  • Adding steam to the native material creates an azeotrope that lowers the boiling points of the compounds being extracted
• CO2 supercritical fluid extraction


  • CO2 is easily compressed to a supercritical liquid phase at ambient temperatures and has lipophilic solvent properties
  • The solubility of supercritical liquids changes with temperature and pressure, allowing fine-tuning of the extraction
• Olfactory memory


  • Perfumers must develop a refined olfactory memory through practice
  • First learn to identify contrasting odours, then various members within an odour family
  • Study the volatility of various perfume materials to understand top notes, middle notes, and base notes
• Note


  The characteristic odour of a single material
• Accord


  Mixtures of two or more materials, having a unified olfactory theme
• Main perfume accords used in perfumery

  • Chypre
  • Cologne
  • Fougere
  • Amber
• Creating a chypre accord

  1. Evaluate a series of ratios of oakmoss and ambergris

  2. Choose a 6:4 ratio, add musk character

  3. Use materials of medium volatility to modify the base accord, including an animal note

  4. Add pleasant, highly volatile top notes to create the immediate impression
• The ratio of 25% top notes, 20% modifiers, and 55% base notes is characteristic of a well-balanced fragrance blend