Lipase-Mediated Interesterification of Oils for Improving Rheological, Heat Transfer Properties and Stability During Deep-Fat Frying

This paper deals with the rheological and heat
transfer properties and stability of rice bran oil (RBO);
refined, bleached and deodorised palm olein (RBDPO) and
their blends in terms of viscosity, heat transfer coefficient
and thermo-oxidative stability. These values were compared
with interesterified oils prepared by subjecting blended oils
to 1, 3-specific lipase treatment. Results showed that the
apparent viscosities and convective heat transfer coefficients
of these oils are within the range of 52.8–61.5 mPa s
and 229.1–258.0 Wm−2 °C−1, respectively. The quality
parameters, namely free fatty acid (0.12–0.68%), peroxide
value (1.47–5.31 meq O2/kg), diene value (0.16–2.39%),
triene value (0.07–0.7%), polar material (2.4–8.8%) and
colour unit (1.0–5.5 red; 7–50 yellow), were significantly
(p<0.05) different in fresh and fried oils for all the oil
systems. The total polar material correlated well (r=0.97)
with change of viscosity of native, blended and interesterified
oils. The interesterified oils are more resistant to
degradation during frying in terms of the formation of
colour and polar materials in comparison to their blended
counterparts. The sensory odour profiles generated by
descriptive analysis showed that both RBO and RBDPO
had desirable characteristic odour notes and these notes did
not alter significantly after frying for ten cycles. Both
blended oil and interesterified oil samples exhibited similar
sensory notes for the fresh and fried oil samples. The poori
fried using blended and interesterified oil have shown
desirable and good consumer acceptance score.