Food Lipids: Chemistry, Nutrition, and Biotechnology

matography (GLC). Other methods not discussed include mass spectroscopy [62]
and stereospecific lipase hydrolysis [63,64].
A. Physical Properties
Physical properties can be determined by examining thermal characteristics, rheological
characteristics, or crystal habit.
1. Cloud Point
The cloud point, or temperature at which crystallization is induced, producing a
crystal cloud, is one of the older indices used to study physical properties of fats.
Eckey [35] monitored the change in cloud point during cottonseed oil interesterification.
Generally, randomization increased the cloud point quickly at first and then
more slowly until an increase of 13–15�C was reached, after which no change was
observed, regardless of reaction duration. For Placek and Holman [47], a study of
cloud point indicated the extent of interesterification of lard.
2. Dropping Point
The Mettler dropping point is a simple yet effective method of measuring the effect
of interesterification on fats. In this procedure, liquefied fats are crystalized in sample
cups and subsequently heated until they begin flowing under their own weight. Kaufmann
and Grothues [65] performed a thorough study of the dropping points of hardstock
and vegetable oil mixtures as an indicator of catalyst activity. Laning [14]
demonstrated the effect of chemical interesterification on palm, palm kernel, and
coconut oils (Table 3). A reduction in dropping point for saturated palm kernel oil
(PKO) and saturated coconut oil was due to the lower average molecular weight of
the triacylglycerol in the randomized fat. The reduction in dropping point reported
for randomized PKO was due to an increase of triacylglycerol species with intermediate
degrees of unsaturation. Cho et al. [66] used the dropping point as in indicator
of the measure of reaction equilibrium. A blend of 70% hydrogenated canola
oil, 10% palm stearin, and 20% canola oil had an initial dropping point of 37�C,
which dropped to 35�C following 5 minutes of reaction and to 32�C after 20 minutes,
remaining constant thereafter. List et al. [67] used dropping point as a verification
of interesterification completion in the preparation of ‘‘zero-trans’’ soybean oil margarine
base stock. Rousseau et al. [34] examined the effect of chemical interesteri-
Table 3 Effect of Interesterification on Dropping Point in
Palm, Palm Kernel, and Coconut Oils (�C)
Oil
Palm oil
Palm kernel (PKO)
Coconut oil (CO)
Saturated PKO
Saturated CO
Source: Ref. 14.
Before
treatment
39.4
28.3
25.5
45.0
37.8
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.
Random
treatment
42.7
26.9
28.2
34.4
31.6
Directed
treatment
51.1
30.0
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