Optimization of the Enzymatic Interesterification of Milk Fat and Canola Oil Blends Using Immobilized Rhizopus oryzae Lipase by Response Surface Methodology 

Gisele Fátima Morais Nunes*, Ariela Veloso de Paula, Heizir Ferreira de Castro and Júlio César dos Santos

Engineering School of Lorena, University of São Paulo, PO Box 116, 12602-810 Lorena, SP, Brazil

Article history:
Received September 13, 2010
Accepted February 1, 20111

Key words:
interesterification, Rhizopus oryzae lipase, milk fat, canola oil, experimental design

Summary:
Blends of milk fat and canola oil (MF:CNO) were enzymatically interesterified (EIE) by Rhizopus oryzae lipase immobilized on polysiloxane-polyvinyl alcohol (SiO₂-PVA) composite, in a solvent-free system. A central composite design (CCD) was used to optimize the reaction, considering the effects of different mass fractions of binary blends of MF:CNO (50:50, 65:35 and 80:20) and temperatures (45, 55 and 65 °C) on the composition and texture properties of the interesterified products, taking the interesterification degree (ID) and consistency (at 10 °C) as response variables. For the ID variable both mass fraction of milk fat in the blend and temperature were found to be significant, while for the consistency only mass fraction of milk fat was significant. Empiric models for ID and consistency were obtained that allowed establishing the best interesterification conditions: blend with 65 % of milk fat and 35 % of canola oil, and temperature of 45 °C. Under these conditions, the ID was 19.77 % and the consistency at 10 °C was 56 290 Pa. The potential of this eco-friendly process demonstrated that a product could be obtained with the desirable milk fat flavour and better spreadability under refrigerated conditions.

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