Retention of natural antioxidants of blends of groundnut and sunflower oils with minor oils during storage and frying.

Unrefined groundnut oil (GNO) and refined sunflower
oil (SFO) were blended with four minor oils including
laboratory refined red palmolein (RRPO), physically refined
rice bran oil (RBO), unrefined sesame oil (SESO), and
unrefined coconut oil (CNO) containing natural antioxidants
viz., β-carotene, tocopherols, oryzanol and lignans. The five
blends prepared were GNO+RRPO (80:20), GNO+RBO
(80:20), GNO+SESO (80:20), SFO+RRPO (50:50) and
SFO+CNO (60:40). Prepared blends contained saturated
fatty acids (SFA) (16.7–53.3 %); monounsaturated fatty
acids (MUFA) (16.0–45.5 %) and polyunsaturated fatty
acids (PUFA) (29.2–37.8 %). GNO blends viz. ,
GNO+RRPO, GNO+RBO and GNO+SESO contained β-
carotene (10.7 mg/100 g), oryzanol (0.12 g/100 g) and
lignans (0.35 g/100 g) respectively as natural antioxidants.
SFO was enriched with β-carotene (28.7 mg/100 g) and
medium chain fatty acids (34.2 %) by blending with RRPO
and CNO respectively. The oil blends (200 ml) were packed
and stored at 38 °C/90 % relative humidity (RH) and
27 °C/65 % RH and samples were withdrawn at fixed intervals
for analysis. Freshly prepared blends were also investigated
for their frying performance. During storage,
GNO+RBO blend showed highest oxidative stability probably
due to the presence of oryzanol in the order
GNO+RBO>GNO+SESO>GNO+RRPO. During frying,
the peroxide value of GNO blends with RBO (rich in
oryzanol) and SESO (rich in lignans) was less while the free
fatty acid value was less in SFO blends with RRPO and
CNO. Hence, blending of natural antioxidants rich minor
oils (RRPO, RBO and SESO) with the major vegetable oils
(GNO and SFO) may preserve them by lowering their rate of
oxidation during storage and frying.