Page 48 - FoodFocusThailand No.170 May 2020

STRATEGIC R & D

Olive oil consists predominantly of triglycerides; approximately 80% below room temperature. Soybean oil contains a significant fraction
of the fatty acids are unsaturated (oleic acid and linoleic acid). Palm oil of saturated fatty acids (10% C16) and also a high percentage of
is one of the few highly saturated vegetable fats. Soybean oil is similar monobasic and dibasic unsaturated fatty acids (nutritionally valuable).
to olive oil regarding the ratio of saturated to unsaturated fatty acids. Triglyceride specimens analyzed by HPLC show fractions with
Rapeseed oil contains practically only unsaturated fatty acids. predominantly saturated fatty acids, with some unsaturated fatty acids
and also with highly unsaturated fatty acids. These 3 triglyceride
Samples, Preparation and Method fractions are visible in the DSC curve at different crystallization
Samples include rapeseed oil and pressed, soybean oil (Homa brand), temperatures. The high fraction of linolenic acid in soybean oil (50%)
olive oil (Dante brand) and Italian first pressing palm oil. Measuring cell leads to a high fraction of glycerides with three linolenic acid units
is DSC with an accessory and DSC measurement is cooling from (melting point -45 °C), which is shown as a peak at -42 °C. Rapeseed
1
50 °C to -100 °C at 10 K/min in the atmosphere that has nitrogen flow oil contains virtually only unsaturated fatty acids (60% C18 monobasic,
at 20 mL/min. Aluminum crucibles, 40 μL with hermetically sealed is 25% C18 dibasic, 10% C18 tribasic) and crystallizes at a very low
used. And there is no special preparation needed. Samples are used temperature. Only 5% of the fatty acids are saturated and this is
as received. indicated by ‘small peaks’ between -20 °C and -40 °C. Even though
DSC cannot clearly identify fatty acids or triglyceride fractions, rapid
Interpretation characterization of the oils/fats is possible.
Olive oil crystallizes below -10 °C. The triglyceride fraction, with in part In conclusion, DSC is a rapid means of investigating the
saturated fatty acids, crystallizes between -10 °C and -35 °C. The main crystallization behavior of edible oils. For comparison purposes
fraction of olive oil, the triglyceride with 3 oleic acid units (70%), approximately identical sample sizes should be taken, e.g. 20 ± 5 mg.
crystallizes at lower temperatures and is recognizable as a crystallization The sample size may influence the supercoiling: the smaller the
peak at -45 °C (a temperature of -35 °C is given in the literature for the sample size the greater the degree of super cooling.
stable α-form). ข้้อมููลเพิ่่�มูเติ่มู/Additional Information
Commercial palm oil 1 อุุปกรณ์์เสริม IntraCooler
crystallizes below +15 °C. It
has a high percentage of
saturated fatty acids (50%
C12, 18% C14) and hence a
high melting point; 8%
unsaturated oleic acid lowers
the melting point to values

DSC Measurement of

Crystallization of vegetable oils

Vegetable oils and fats are mainly esters of glycerol
with fatty acids, so-called triglycerides. Oils are
free flowing at room temperature; fats are solid.
Vegetable oils often contain a higher content
of unsaturated fatty acids than animal fats
and are therefore considered to be healthier.
Furthermore, vegetable oils do not contain
cholesterol.

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