Food Lipids: Chemistry, Nutrition, and Biotechnology

as more recent efforts [70] showed that the final cocoa butter polymorph depends
on the crystallization temperature, not the polymorphic form of the added seed.
The effects of several triacylglycerol seeds on the polymorphism and solidification
of cocoa butter in dark chocolate have also been investigated [71,72]. Regarding
crystallization rate, it was concluded that thermodynamic stability and crystal
structure similarity to cocoa butter are most effective. Specifically, 1,3-distearoyl-2oleoylglyceride
(StOSt) produced greater enhancement than 1,3-dibehenoyl-2-oleoylglyceride
(BOB), which produced a much greater enhancement than 1,2,3-tristearoylglyceride
(StStSt). It seems that a chain length similarity between the cocoa
butter and the crystal seed better facilitates crystal growth. Interestingly, the � form
of the StOSt produced a greater crystallization rate than a mixture of �� and �.
Therefore, although crystallization temperature alone determines the final cocoa butter
form, the rate of crystallization may be a function of the polymorphic form of
the seed.
5. Intrinsic ‘‘Seeding’’ and Cocoa Butter Crystallization
The crystal morphology of cocoa butter during isothermal crystallization has been
detailed [73]. A higher concentration of StOSt was found in crystals that developed
early versus the original StOSt concentration in the melt. It was hypothesized that
subsequent crystallization occurred on these crystal ‘‘seeds.’’ Such fractional crystallization
may produce crystal seeds, rich in StOSt, which have been shown to
accelerate cocoa butter crystallization [71,72].
Compounds other than triacylglycerols, found in cocoa butter, have also been
investigated for their potential to act as crystal seeds. High-melting crystals isolated
from crystallizing cocoa butter melts during the very early stages of crystallization
were found to contain very high phospholipid and glycolipid concentrations relative
to the original cocoa butter [74,75]. Dimick [76a,76b] proposed that these amphiphilic
compounds may associate with the small amount of water in cocoa butter and
serve as the nuclei for crystallization (Fig. 12). The phospholipid species found in
both the crystal seed and the original butter were identified [11,77]. The data indicated
that faster crystallizing cocoa butters contained a relatively high percentage of
phosphatidylcholine and phosphatidylglycerol, whereas the slower crystallizing samples
had more phosphatidylinositol and significantly less phosphatidylcholine.
The effects on cocoa butter crystallization from simple degumming and those
due to added phospholipid seed material were subsequently investigated in the same
laboratory [79,80]. Degummed Bahian and Côte d’Ivoire cocoa butters both had
significantly slower crystallization rates relative to the untreated butters. Addition of
pure sn-1,2-distearoylphosphatidylcholine completely inhibited the crystallization of
the original butters. However, addition of 0.1% of this phospholipid to the degummed
butters increased their crystallization rates to match the untreated samples. After
tempering, the original Côte d’Ivoire butter containing pure sn-1,2-distearoylphosphatidylcholine
had greater solids at 30�C (via NMR) than the untreated butter. Pure
sn-1,2-dioleoylphosphatidylcholine increased the crystallization rate of the Côte
d’Ivoire butter but inhibited the crystallization of the Bahian butter. Also, as with
sn-1,2-distearoylphosphatidylcholine, added sn-1,2-dioleoylphosphatidylcholine in
the Côte d’Ivoire butter significantly increased the solids at 30�C. These data show
that phospholipids can increase the crystallization rate and enhance the development
of the more stable polymorphic form of cocoa butter.
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.