Odour to a sensing scale

Packaging Professional magazine
,
17 Jul 2011

A novel scaling system
has been developed
to evaluate off-odours
in fluid food packs with
headspace.

A collaborative team from
Tetra Pak, in Lund, Sweden,
and the University of
Copenhagen, Denmark, has
developed a scaling system that
measures the intensity of
odours using a brightness scale
that ranges from light grey
to black.

The team claims that no
specific method for monitoring
odours in package headspace
has previously existed.

According to Senior
Laboratory Scientist Lars
Kristoffersson, of Tetra Pak,
and Professor Wender Bredie,
from the University of
Copenhagen, the process
involves assembling a team of
panelists to rate five 1-butanol
reference samples (0.5, 25, 125
and 625 parts per million) on
a colour brightness scale in
three replicates.

After a five-minute break, offodour
intensity in the package
headspace is assessed in the
replicates using the colour
brightness line scale ranging
from ‘nothing’ to ‘very strong’. A
15cm line scale completes the
trio of scales tested.

One-butanol is used as the
reference point, in accordance
with the American Society for
Testing and Materials odour
standards. To test the method, a
laminated carton type for fluid
foods was used.

The researchers say the
scales, ‘did not affect the
odour intensity ratings. However,
the colour-graded brightness
line scale tended to give a
greater accuracy of odour
intensity and may strengthen
the repeatability of the
intensity measures due to the
cross-modal support in the
judgment processes.’

They add that, ‘The method
allows the conversion of intensity
judgment of a package headspace
to a physical intensity
scale of 1-butanol and thus
provides a valuable reference for
comparing different package
assessments over time’.

In relation to the benefits of
the scale, Kristoffersson says,
‘The feedback from the trained
sensory assessors is that
this scale is easier to use for
them. The scale combines a
cross-modal match between the
perceived intensity of the odour
or taste with the visual intensity
of the lightness of the scale. This
task is simplified since the
traditional scaling on a line scale
matches perceived odour/taste intensity with the length of
a scale.’

He adds that it could provide
support in making odour judgements
and improve the accuracy
of odour intensity ratings.

While the scale is ready for
use, the team says that further
studies are needed to improve
sensory knowledge and achieve
more reliable results.

The University of Copenhagen
researchers are also developing
scales for other purposes, such
as measurement of preferences
and satisfaction.