Yoghurt Fruit Preparations - Herbstreith & Fox

yield point
before shearing
destruction
yield point [Pa]
regeneration
based on
destruction
regeneration based
on yield point
before shearing
yield point [Pa]
yield point after
shearing [Pa]
regenerated yield
point [Pa]
Fig. 6: Determining the regenerative behaviour of yoghurt fruit preparations
To determine the yield point, the shear stress is
continuously increased. The yield point τ0 [Pa]
is exceeded when a shear rate is measured for
the first time.
To characterise both texture and regenerative
behaviour of cold yoghurt fruit preparations,
it is important to determinate the yield point
before and after distinct process steps.
By means of a shear-stress controlled rotation
rheometer, H&F is able to rheologically reconstruct
various stress profiles, thus simulating
the processing of yoghurt fruit preparations.
The so-called ”yield point before shearing” is
determined in the still intact fruit preparation
and is a measurement of its firmness, as to be
found for example in the container or other
trading unit.
Fruit preparations with a higher yield point
before shearing are perceived by the senses as
being firmer than fruit preparations with a
lower yield point before shearing.
Without a yield point a fruit preparation would
not be stable, it would be liquid and would
run, even if the viscosity were very high.
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Pectins in Yoghurt Fruit Preparations