and crystallised between 40 8C and 53 8C (see Figs. 1 and 2),
thus at higher temperatures than the bulk fat.
The thermal behaviour of the bulk fat changed with the
addition of different quantities of MDGs. In the crystallisation
curves (see Fig. 1) the two exothermal peaks of the bulk fat
were replaced by a single peak at around 0–5 8C. Moreover,
with the addition of greater quantities of MDGs a second peak
appears on both melting and crystallisation, one in the
position of the bulk fat peak (see ‘A’ in Figs. 1 and 2), and
the other at a higher temperature representative of the MDGs
(35–50 8C for the crystallisation and 40–57 8C for the melting
thermograms; see ‘B’ in Figs. 1 and 2). The melting and
crystallisation peaks in position ‘B’ (see Fig. 3B) shifted to
higher temperature with the addition of MDGs (logarithmic
R2 = 0.97 and 0.93 for melting and crystallisation, respectively).
However, the peak temperatures were always lower than the
MDGs alone, probably due to the effect that the sunflower oil
exerted on it.
Given the presence of the peaks in position B it was assumed
that there was independent melting and crystallisation of the
bulk fat and the MDGs. In order to have a clearer understanding
of the behaviour observed, experimental enthalpies of peaks in
position B were calculated and compared to predicted enthal-
pies calculated assuming that this peak was as a result of
melting or crystallisation of the MDGs alone.
As the experimentally measured enthalpies were very
similar to the predicted DH’s (see Fig. 4) it was concluded that
MDGs melt and crystallise independently from the bulk fat,
with the peak in position ‘B’ being a result of the melting or
crystallisation of the MDGs only. Nevertheless, on the addition
of MDGs there was still an effect on the melting and
crystallisation of the bulk fat as the shape of the curves in
position ‘A’ changed (see Figs. 1 and 2), even if the melting
peak maximum (see Fig. 3A) and the enthalpies (see Fig. 5) did
not change significantly (linear R2 = 0.57 and 0.3 for melting
and crystallisation peak maximums and linear R2 = 0.08 and