3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
Table II
Values of the induction periods – extrapolation to 25 °C (t i 25 )
and extrapolation to 100 °C (t i 100 )
Oils t i 25 [min] ti 100 [min]
Castor 3.00 × 10 7 2.81 × 10 3
Olive 1.28 × 10 7 1.70 × 10 3
Soya Bean 1.34 × 10 6 5.29 × 10 2
Avocado 1.03 × 10 6 5.37 × 10 2
Grape Seed 9.87 × 10 5 3.22 × 10 2
Almond 5.93 × 10 5 3.52 × 10 2
Corn 5.44 × 10 5 3.80 × 10 2
Apricot Kernel 3.31 × 10 5 2.65 × 10 2
Crude Linseed 1.79 × 10 5 9.49 × 10 1
In the case low temperature (25 °C), sequence of stability
vegetable oils was falled: castor > olive > soya bean > avocado
> grape seed > almond > corn > apricot kernel > crude linseed.
Enormously high induction period values, especially castor
and olive oil, appeared unreal. By this reason, the extrapolation
on high temperature (100 °C) was applied.
From the determined values it is obvious that castor
and olive oil had the longest induction period and apricot kernel
and crude linseed oil had the shortest induction period. In
the case soya bean and avocado oil, it was obtained the similar
results and the values of the both oils differed about 8
minutes.
Induction periods for individual oils were determined
from the known values onset temperatures and parameters
A and B. Equation 1 was used for calculation. Dependences
of the experimental calculated induction periods on the temperatures
are demonstrated in Fig. 1.
s796
Fig. 1. Temperature dependences of the induction periods for
the most stable (castor and olive oil) and the least stable (apricot
kernel and crude linseed oil) vegetable oils
Conclusions
The order of stability of vegetable oils was identified
by statistical comparison of record gained from various temperature
extrapolation and reciprocal comparison of stability
of given oils. The order of the most stable oils (castor
and olive oil) and the least stable oil (linseed oil) depending
on extrapolation and reciprocal comparison did not differ.
The non-isothermal method DSC was employed with the aim
to determine the induction period of vegetable oils.
REFEREnCES
1. Dugo G. et al.: Food Chem. 87, 639 (2004).
2. Coni E., et. al.: Thermochim. Acta 418, 11 (2004).
3. Šimon P. Kolman L., et al.: JAOCS 77, 639 (2000).
4. Tan C. P., Che Man Y. B.: Trends Food Sci. Technol. 13,
312 (2002).
5. Giuffrida F., et al.: Food Chem. 101, 1108 (2007).
6. Crapiste G. H., et al: JAOCS 77, 1437 (1999).
7. Frankel E. n.: Trends Food Sci. Technol. 4, 220 (1993).