onstituents.
Fig. 3 shows the firmness of the stirred yoghurt samples as
a function of time (1, 2, 3, 7 and 21 d after production). All stirred
yoghurt samples showed an increased firmness with time. The
firmness of the yoghurt with 3% fat (reference) showed the smallest
and constant increase with time, resulting in a structure change
during shelf-life between 3 and 21 d. The firmness of the ATScontaining
yoghurts showed the large increase with time. As
most of this build up was observed within one day, this resulted in
a constant structure during shelf-life. It required 2 d of storage at
5 C to reach a similar level as the reference. The final firmness (21 d
after production) of all yoghurt samples with ATS was similar to the
reference. This effect can be explained by the findings in yoghurt
serum that the formation of ATS domains is a time-driven process.
A CLSM image of stirred yoghurt (Fig. 4) shows in detail the presence
and entrapment of ATS domains in the pores of the protein
matrix as was described by Alting et al. (2009).