Essential Oils and Floral Products Quiz

Volatile Oils: Definition

• Complex liquid mixtures of odoriferous compounds
• Varying chemical compositions
• Easily evaporate at ordinary temperatures
• Also known as ethereal oils or essential oils
• Used therapeutically, for flavoring, and perfuming
• Starting materials for semi-synthesizing other compounds

Volatile Oils: Combined with

• Sugars forming the aglycone part of certain glycosides
• Gums, resins, or both to form oleo-gums, oleoresins, or oleo-gum-resins

Physical Properties

• Volatile liquids
• Pleasant smells
• Steam-distilled (e.g., fixed oils)
• Immiscible with water but soluble enough to impart a distinct fragrance to water (aromatic waters)
• Soluble in common organic solvents and lipids (liposoluble)
• May darken in color when exposed to light (due to oxidation and resinification)

Chemical Composition

• Complex mixtures of constituents
• Hydrocarbons
• Oxygenated compounds (e.g., alcohols, ketones, aldehydes, ethers, oxides, phenols, esters)
• Some oils consist of one main component (e.g., volatile oil of mustard (93% allylisothiocyanate), oil of clove (85% eugenol))

Methods of Preparation: Factors Affecting Selection

• Plant material condition (dry or fresh)
• Degree of comminution (intact, crushed, or powdered)
• Oil localization in the plant (superficial or deep)
• Amount of oil
• Nature of constituents

Methods of Preparation

• Distillation
• Expression
• Extraction
• Enzymatic hydrolysis

Distillation Methods

• Water distillation method: Dry plant material directly contacts boiling water (e.g., turpentine oil)
• Water and steam distillation: Plant material (dry or fresh) is supported on a perforated screen, with water below the screen, only steam contacts the material (e.g., cinnamon, cloves)
• Direct steam distillation: No water in the still; steam is introduced through a steam coil (e.g., peppermint, spearmint)

Precautions in Handling Plant Material

• Crush plant material just before distillation to prevent loss through volatilization
• Dried plant material subjected to saturated steam distillation should be wet before packing
• Even packing/charging to facilitate "hydro diffusion"
• Use stainless steel for oxygenated compounds (avoid iron)

Different Types of Distillation Apparatus

• Diagrams of water distillation, water & steam distillation, direct steam distillation

Expression Methods:

• Mechanical procedures at room temperature
• Used for heat-sensitive oils present in large amounts in fruit peels (e.g., Citrus fruits, orange, lemon).
• Methods: Sponge method, Expression of rasping, Scarification method, Machine processes

Extraction Methods:

• Used for delicate flowers oils (e.g., jasmine, violet, narcissus)
• Contains small amounts of oils easily lost in large volumes of distillation water
• Oils that decompose with heat
• Methods include non-volatile and volatile solvent extraction

Non-Volatile Solvent Extraction

• Used for preparing natural flower oils (e.g., perfumes)
• Based on the liposolubility of fragrant plant components
• Uses highly pure lipids (e.g., fats such as lard and tallow—a 2:1 mixture to avoid melting; fixed oils such as olive oil)
• Methods: Enfleurage Process - a method using glass plates, fat layers, and flowers to extract oils, followed by scraping and cooling to yield a floral pomade product

Volatile Solvent Extraction

• Select solvents based on selectivity, stability, boiling points, volatility, and safety (non-toxic, non-flammable) like absolute alcohol to prepare concretes & absolutes
• Uses the Soxhlet apparatus (details shown pictorially) for hot extraction at constant temperatures

Preparation of "Floral Concretes":

1. Extraction by percolation/maceration at room temperature or continuous hot extraction in a Soxhlet apparatus at a constant temp (no over 50°C). 2.Removal of the solvent by distillation under reduced pressure. 3."Floral concrete" of jasmine is a semi-solid yellowish-orange product. 4."Floral concrete" consists of fragrant constituents with liposoluble impurities (e.g., fats, waxes, pigments).

Preparation of "Floral Absolutes":

• More expensive & purified products compared to concretes.
• Repeated extraction with absolute alcohol to extract oxygenated constituents.
• Followed by chilling and decantation to remove waxes and fat-soluble pigments.
• Resulting absolutes are richer in oxygenated constituents that yield the characteristic odor.
• Used at lower concentrations than concretes in perfume industry.

Enzymatic Hydrolysis of Glycosides

• Many glycosides yield volatile aglycones upon hydrolysis
• Enzymes used in plants for hydrolysis of glycosides
• Aglycones belong to different classes. Procedure steps for enzymatic hydrolysis.

Determination of Volatile Oil: Quantitative Analysis

• Evaluates plant species quality and raw material suitability for commercial preparation to differentiate genuine from adulterated oil
• Uses Clavenger’s apparatus (pictured) for analysis

Determination of Volatile Oil: Qualitative Analysis

• Odor analysis: Abnormal odor implies adulteration/deterioration
• Solubility analysis: Solubility in different alcohol strengths (e.g., varied percentage ethyl alcohol solutions)
• Optical rotation analysis: Rotations of polarized light, using a polarimeter, show activity of chemical products
• Chemical tests: chemical tests of isolated plant volatile oils to determine functional groups present

Chemistry of Volatile Oils

• Single-component oils (e.g., benzaldehyde, methyl salicylate)
• Complex mixtures of hydrocarbons known as terpenes and related oxygenated compounds
• Definition of terpenes: natural products with formulas divisible into isoprene units, with a "head-to-tail" arrangement (isoprene rule)
• Classification of terpene types (e.g., monoterpenes, sesquiterpenes) shown visually (tables)