Natural aroma chemicals for use in foods and beverages - Natural Food Additives, Ingredients and Flavourings - page 212

10.2.3 Techniques
While the basic techniques of distillation and crystallisation remain the
cornerstones of isolation techniques, the increased demand for natural aroma
chemicals means that greater effort is expended in isolating components at
low concentrations - materials that might be said to be 'down in the noise' on
chromatographic traces!

10.3 Quality control and natural aroma chemicals
There is an irony here. In general, the aim of the supplier of natural aroma chemicals,
refl ecting the general desire in the fl avour industry, is for the natural materials to be
as close in quality to that of the already established 'synthetic' material; this enables
the fl avourist to replace a nature-identical fl avour with a natural one with minimal
effort. Yet at the same time this emphasises that the lack of technical advantage to
using natural aroma chemicals, that 'natural' is purely a marketing conceit. It has
the added impact that as natural materials increasingly approximate the quality of
their synthetic cousins, it becomes harder to tell them apart!
Originally, natural aroma chemicals were often best described as fractions or
cuts from distillations; one still comes across things like 'decanal 50% in orange
oil'. Higher purity materials always have an advantage that the potential variations
in quality are less (a similar phenomenon has taken place in synthetics, especially
where materials are a mixture of isomers, e.g. the 'industry standard' trans -2-
hexenal moving from 95% to 98%). Quality requirements have also risen in
organoleptic terms. Dimethyl sulfi de [10.1], formerly isolated from mint oils (in
the form of 'peppermint heads', the most volatile fraction from mint oils) was
generally ca. 95% pure, with the remainder consisting of a range of materials with
volatilities ranging from acetaldehyde to furfural, and whose odour standard was
'if it doesn't smell of mint, it's OK'. This is now produced as a fermentation
by-product (see below), assays in the region of 99% and approximates to the
clean, sweetcorn-asparagus note of good quality, washed and redistilled synthetic
material.

￿ ￿ ￿ ￿ ￿ [10.1]

10.4 Natural aroma chemicals by direct isolation
10.4.1 Natural aroma chemicals from essential oils and extracts
This is still the single most important approach, especially in terms of sheer volume.
It is also potentially the most turgidly dull to write or read about, so the author will
try to avoid the worst 'book of lists' approach and NOT do a table of citrus oils and
their terpenes! However, it is equally true that the citrus oils, produced in enormous