IDM ¦ Technology/IT
What influence does foaming
have on the release and
perception of aroma
compounds in dairy products?
Authors:
C. Borsum, J. Hinrichs, University of Hohenheim, Inst. of Food Science and Biotechnology,
Dept. Soft Matter Science and Dairy Technology, Garbenstrasse 21, D-70599 Stuttgart, Germany
For many years, companies have been reformulating foods
with the aim to reduce salt, sugar and fat consumption.
Meanwhile, based on the "White Paper on Nutrition, Overweight
and Obesity related health issues" (European Commission,
2007), many EU member states promote and call for food
reformulation "as a relationship prevention building block of a
holistic approach" to "facilitate healthy diets, especially for those
population groups that are not reached or poorly reached by behavioral
prevention measures" (German Federal Ministry of Food
and Agriculture, 2017).
However, if fat is reduced in a dairy product formulation, the
desired effect of energy reduction is accompanied by a different
sensory impression, which is usually less preferred. In addition to
the change in mouthfeel, this is mainly due to the absence of fat as
a reservoir for aroma substances. Aroma compounds are released
from this reservoir during consumption. It should be investigated
whether the release of aroma substances from fat-free milk matrices
can be influenced in another way. Qualitative sensory preliminary
studies showed, for example, that the aroma perception is
more intense in foamed products.
When a food product is consumed, various physical processes
take place that influence aroma perception (Fig. 1). In the closed
package, there is initially an equilibrium between the aroma concentration
in the food matrix and the headspace, which is perceived
as an odor via the olfactory sensors of the nose (orthonasally1)
when the package is opened. Diffusively2, the matrix
42 · March/April 2022 ¦ international-dairy.com
further releases aroma substances via the surface. If a portion is
now transferred to the mouth, the increased temperature and the
mechanics of chewing support the release of aroma substances.
The interaction of these processes results in what is known as retronasal
aroma perception, in that aroma substances are conducted
to the olfactory sensors during swallowing and exhalation. Other
influencing factors such as saliva, chewing intensity and breathing
make an individually varying contribution by strengthening or
weakening aroma perception, as studies have shown.
But why should the aroma perception be more intense during
consumption of a foamed food than an unfoamed one? Is it
related to the disintegration of the bubbles, which release contained
aroma substances in an "aroma boost"? Or do processes
take place at the enlarged interface that influence the release?
To investigate these questions, a simplified model system
(mouth model) was first constructed to study the physical processes
of aroma release. The simplified model consists of a 90 mL
vial containing 10 g of sample heated at 40 °C in an incubator
(Thomas et al., 2020). The model milk matrix contained 4% milk
protein, was stabilized with gelatin, and acidified with glucono-
δ-lactone for gel formation. Ten key aroma compounds, mostly
derived from herbs, spices, or dairy products, were added to the
matrix. They differed on the one hand in their solubility behavior3,
on the other hand in their volatility4. An overrun of approx. 150 %
was achieved by foaming. When the model milk matrix prepared
in this way is heated to 40 °C, softening occurs, which in the case
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