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

Abstract

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 W m−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.