It swallows, breathes, salivates and knocks back fizzy drinks
like there is no tomorrow. It is the latest weapon in food chemistry:
the artificial throat.
Developing the flavour of a new sports or low-carbohydrate
drink is a lengthy task, involving many tests by panels of human
tasters. The artificial throat was developed to spare drinks makers the
expense and hassle involved in organising and analysing hundreds of
tests by helping to predict how a drink will taste. It works by
mimicking the process of human tasting.
Taste is mostly smell. The tongue’s taste receptors identify
only the basic flavours: sweet, sour, salt, bitter and umami. The finer
distinctions are made high in the nasal passages where flavours such as
orange, cherry and chocolate are sensed.
Most of the information used to sense these more subtle
flavours comes from the very first puff of air we exhale after
swallowing. That breath picks up molecules from the drink or food and
carries them up the nasal passages. This information is especially
important with drinks, because they spend so little time in the mouth
before heading down the hatch.
Oral physiology
When drinks makers are experimenting with hundreds of
different recipes, they need to work out quickly how different
ingredients will influence flavour. They analyse a drinker’s breath
using a mass spectrometer to read the concentration profile of various
volatile compounds.
But using people for these tests yields highly variable
results, because everyone has a slightly different oral physiology,
with different mouth volumes and breath patterns. Yet until now it was
the only option because the act of swallowing is so important to
flavour release: measuring a static pool of liquid cannot predict which
aromas will make it to the nose.
So Alexandra Boelrijk at NIZO Food Research and colleagues at
flavourings company Quest International and Wageningen University in the
Netherlands have developed the artificial throat. The team connected
two glass tubes with a segment of rubber tubing that could be closed
with a clamp.
The top tube represented the mouth, the lower one the
oesophagus. At the bottom of the set-up they attached an air jet, which
sent gas up the tubes at the same rate as an average human exhalation.
Aroma profiles
When the clamp was closed, they filled the top portion with a
few millilitres of a lemon-flavoured test liquid. Once the “mouth” was
full, they opened the clamp to release it. When the liquid drained
leaving just a thin layer behind on the interior walls of the
“oesophagus”, they turned on the air.
The “breath” was then sampled at the top of the device and
analysed by a mass spectrometer. Boelrijk’s team found that all the
flavours they tested almost perfectly matched the breath aroma profiles
from human panellists. Salivation did not appear to be a factor, for
drinks at least: when human saliva was included in the throat in some
tests, it made no difference to the taste signatures.
Boelrijk says the set-up is useful for complicated beverages,
like sports or low-carbohydrate drinks, because the proteins and sugars
in them can interfere with other flavours. “You can screen out a lot of
mixtures really quickly. Some ingredients are great for texture, but
they just taste awful,” she says.
Andrew Taylor, a food chemist at the University of Nottingham
in the UK, welcomed the development. The next step, he says, is to
understand why that first breath matters so much and how individual
differences in swallowing physiology contribute to taste perception.
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