was selected along with coconut oil

was selected along with coconut oil for modification by fractionation and blending. The objective of the present study was to assess the suitability of coconut oil to preparetrans-free plastic fat
for use in bakery products.
2. Materials and methods
2.1. Material
Palm oil was a gift from M/s Palm Tech. Limited, Mysore, India.
Coconut oil and commercial bakery shortening were purchased
from local market. Standard fatty acid methyl esters, triacylglycerols and BF3/methanol were procured from Sigma Chemical Co.,
St. Louis, MO. HPLC solvents – acetone and acetonitrile – were from
M/s Qualigens, Mumbai, India. Other chemicals and solvents used
were of analytical grade.
2.2. Refining of fats
The crude fats were analysed for free fatty acids (FFA) content,
according to the standard procedure (AOCS, 2003). The oils were
heated to 55C and the required amount of alkali (14Baume), calculated based on FFA, was added slowly. The soap stock was allowed to settle and then removed by centrifuging. The residual
soap was removed by repeated washing using hot water and traces
of water removed under vacuum (Hodgson, 1996). The refined oil
was stored at 4C and used for further work.
2.3. Fractionation methodology
Fractionation was carried out in beakers in a thermostaticallycontrolled circulating water bath (Julabo Labortechnik, Germany).
The samples were gradually cooled to a pre-determined temperature and kept in the water bath for various time intervals. Care
was taken that the water was above the level of oil in the beaker.
The sample was gently stirred and the temperature was constantly
monitored using a thermometer kept inside the sample. After a
specified time, the partially crystallised mass was filtered, the solid
(stearin) and the liquid (olein) fractions were weighed and the percentage was calculated. The conditions used for various fats are described below.
2.3.1. Fractionation of palm oil
Palm oil (100 g) was heated to about 60C to destroy all crystal
nuclei. The fat was cooled gradually to 31C and held at this temperature for 3 h. The partially crystallised mass was then filtered
through a Buchner funnel under vacuum to separate the stearin
(13.8%; PSt) and the olein fractions.
2.3.2. Fractionation of coconut oil
Coconut oil (100 g) was heated to about 60C to destroy all
crystal nuclei. The fat was cooled gradually to 14C and held at this
temperature for 90 min. The solid and liquid fractions were separated by filtration to yield 40% stearin (CSt1). In another experiment, a stearin of 60% yield (CSt2) was obtained by increasing
the time of holding to 2 h.
2.4. Preparation of blends
Liquified coconut stearin (CSt1 and CSt2) and palm stearin (PSt)
were mixed in different proportions ranging from 10% to 90%, in
10% increments (w/w).
The commercial bakery shortening was found to contain about
16% moisture. This sample was heated to 60C in a hot-air oven
and the water was removed by decanting. The residual moisture
was removed using anhydrous sodium sulphate and the dry fat
was used for further studies.
2.5. Slip melting point (SMP)
The slip melting point was measured according to the official
AOCS procedure, using an open capillary tube (AOCS, 2003). The
sample was melted and a capillary tube with thin walls and
1 mm i.d was dipped to fill with fat to a 10 mm height. The capillary was touched over a piece of ice and the fat was solidified. The
capillary was left at refrigerated temperature for about 10 h and
then left at 0C for 1 h. Two capillaries were attached gently to a
thermometer using a rubber band and fixed onto a Thiele tube.
The side arm of the tube was heated slowly and the temperature
at which the fat slips and rises was noted. Duplicate measurements
were made and the average value is reported.
2.6. Iodine value
Standard AOCS official method was followed to determine the
iodine value using Wij’s solution (AOCS, 2003).
2.7. Fatty acid composition
The fatty acid composition of the samples was determined by
analysing the fatty acid methyl esters by gas chromatography.
The methyl esters were prepared using 14% BF3/methanol (Morrison
& Smith, 1964) and were analysed using a Shimadzu GC-15A
(Shimadzu, Kyoto, Japan) equipped with a flame ionisation detector attached to a CR-4A data processor. The operating conditions
were: column length 3 m3.3 mm; stainless steel packed with
15% diethylene glycol succinate (DEGS) coated on Chromosorb W
(60–80 mesh); column temperature 180C; injector temperature
220C; detector temperature: 230C; carrier gas, nitrogen at a flow
rate of 40 ml/min. The peaks were identified by comparing the
retention times with those of authentic standards and reported as
relative percentage of individual fatty acids.
2.8. Triacylglycerol composition
The triacylglycerol composition of the samples was determined
by high-performance liquid chromatography using a Shimadzu LC-10A with system controller CBM-10A and refractive index detector
RID-10A. A C-18 column (Shimadzu ODS; 25 cm4.6 mm i.d;
5lm particle size) maintained at 36C was used. The mobile phase
was a mixture of acetone/acetonitrile (63.5:36.5, v/v) at a flow rate
of 1 ml/min. Samples were purified by passing through a silica gel
column and eluting with hexane. The solvent was evaporated, the
pure triglycerides dissolved in chloroform and 10ll was injected
into the HPLC. The peaks were identified by comparing the retention times with those of authentic standards, and with literature
values (Laureles et al., 2002; Tan & Che Man, 2002) and reported
as relative percentages for individual triglycerides.
2.9. Solid fat index
The percent solids at different temperatures was determined
using dilatometers, according to a standard method (Paquot & Hautfenne, 1987). A circulatory water bath was used to control the
temperature (±0.1C).
2.10. Fourier transform infrared spectroscopy
FTIR studies were carried out using an FTIR spectrometer (Perkin–
Elmer Spectrum 2000, Norwalk, CT). The samples were melted and