Thermo-oxidative Changes in Vegetable Oil Blends at Frying Conditions

Effect of dry heat and atmospheric oxygen have
been reported in binary mixture of groundnut, sunflower,
mustard and palmolein oils with sesame oil (GS, SS,
MS, PS ; 70:30) and ternary mixture of above oils with
rice bran and sesame oils (GRS, SRS, MRS, PRS;
60:20:20) during this study. Blends were prepared to
assess the efficacy of antioxidant and nutritional factors
present in sesame and rice bran oils. Blends were
heated at frying temperature, 180-190ºC, for 30, 60,
120 and 180 minutes with an interval of 3 days each
to allow thermal changes during heating and autooxidation.
Free fatty acids, peroxides, moisture,
anisidine values, UV, FT-IR, glyceride composition,
thin-layer chromatography, color TLC, UV spectral
analysis and smoke points were carried out for untreated
and heat treated binary and ternary blends. The
increase in FFA, PV and anisidine value was maximum
in SS (2.0), SS (52.8) and MS (33.3) whereas minimum
in GS (0.79), PS (29.9) and GS (20.3) respectively
indicating blend SS was least stable and GS was most
stable combination. UV absorbance at 232-234 nm
was maximum (1.4) for SS blend. Hydroperoxides
were confirmed by FT-IR between 3650-3590 cm-1.
Among ternary blends namely GRS, SRS, MRS and
PRS, maximum degradation of triglycerides occurred
in SRS (99.3 to 98%) and minimum in MRS (99.5 to
98.5%) indicating that latter was most heat resistant
and former least. UV-data and smoke points have
confirmed that ternary blends PRS and MRS were
more heat resistant than GRS and SRS. In totality
sunflower oil blend was found to be least stable and
palmolein/ground nut oil based most stable.