Physico-chemical changes in rice bran oil during heating at frying temperature.

Rice bran oil was subjected to static heating at
180+2°C in a domestic fryer for 8 h in this process 150 ml
of the heated oil samples were drawn, at intervals of every
2 h, to study the changes in the physico-chemical characteristics.
Results indicated that the peroxide value and free
fatty acid content increased gradually from 0.2 to 2.9 Meq.
O2/kg of oil and 0.25 to 0.63% respectively. The oil
became darker as given by the colour value (5R + Y) 63
Lovibond units. Tocopherol content was found to decrease
from 48 mg/100gram to 5 mg/100gram at the end of 8 h of
heating whereas, oryzanol was fairly stable (1.59 to 1.40%).
The p-anisidine value and Total polar compound (TPC)
increased from 5.04 to 18.30 and 1.0 to1.8% respectively,
showing the formation of secondary oxidation products.
Rice bran oil is a non-Newtonian fluids having shear
thinning behavior. Heating was found to cause an increase
in the flow behavior index. Fatty acid composition did not
show significant changes except for the linoleic acid
content which decreased from 29.4 to 27.1%.