original network, thereby blocking these pores, greatly diminishing the
permeability. Because the crystals aggregate unhindered (W¼1) and crystal
growth is relatively slow, despite the high supersaturation, such events can
occur. The second generation aggregates will also become bonded to the
original network, thereby making it much stiffer.
Moreover, the crystals in the network will grow by deposition of
crystallizing triglycerides, which can lead tosintering; this is illustrated by
the two details given of frames 2 and 4. The occurrence of sintered bonds is
borne out in that the moduli observed are significantly larger than is
calculated on the basis of van der Waals attraction between crystals.
Some Variables. Figure 17.22 shows that for a higher initial
supersaturation, the values forBare smaller and those forG^0 are larger at
the samej. This is in qualitative agreement with the sequence of events
outlined above: for a higher value of lnb 0 , the supersaturation at the
moment of gel formation is higher, allowing more extensive nucleation,
whereby more second generation aggregates can be formed; this will result
FIGURE17.22 Properties of fats consisting of hydrogenated palm oil in sunflower
oil, crystallized at various initial supersaturation lnb 0 (indicated near the curves) as
functions of the volume fraction solidj. (a) PermeabilityB. (b) Storage shear
modulusG^0. Heavy solid lines give experimental results. (From results by W. Kloek.
Ph.D. thesis, Wageningen University, 1998.)