Enzymatic transesterification of palm stearin and olein blends to produce zero-trans margarine fat

Abstract

Background: Food industries aim to replace trans fat in their products by formulations having equivalent functionality and economic viability. Enzymatic transesterification can be a technological option to produce trans free fats targeting commercial applications.

Results: Palm stearin and palm olein blends in different ratios were enzymatically transesterified in a solvent free system using a Rhizopus oryzae lipase immobilised onto CaCO3 to produce a suitable fat for margarine formulation. Slip melting points and triacylglycerols profiles were evaluated upon transesterification. Results indicated that all transesterified blends had lower slip melting points than their non transesterified counterparts. Furthermore, the triacylglycerols profile showed a decrease in the concentration of the high melting point triacylglycerols. The rheological analysis showed that margarine prepared with the transesterified blend showed a better spreadability than that of a control margarine prepared with non transesterified fat. Adding powder of dry bark orange to margarine preparation improved its colour and fairly affected its spreadability and rheological behaviour. The margarine prepared with transesterified fat displayed a rheological behaviour that was comparable to that of commercial sample.

Conclusions: This study is an ecofriendly approach to the utilization of relatively low value bioresources like palm stearin and palm olein for making margarine free of trans fatty acids that are now implicated as risk factor for heart diseases.

Figure 1

Slip melting point of palm stearin (PS)/ palm olein (PO) mixture during transesterification. PS/PO (w/w): 35/65 (closed triangles) 40/60 (closed squares) 60/40 (closed diamonds). Reaction conditions: 1000 IU ROLi, 50 °C and 200 rpm.

Figure 2

HPLC Chromatograms of (A) non-transesterified and (B) transesterified palm stearin and palm olein blend (40:60) obtained after 24 h of reaction time (P, Palmitic; O, oleic acid; L, linoleic; Ln, Linolenic acid; S, stearic acid).

Figure 3

Margarine prepared with PS:PO (40:60) blend. (A) non transesterified blend, (B) transesterified blend, (C) transesterified blend containing powder of dry bark orange.

Figure 4

Rheological data, (A) Effect of shear strain rate on the apparent viscosity. (B) Effect of shear strain rate on the shear stress. Margarines prepared with PS:PO (40:60) blend. (closed diamonds) non transesterified blend added 3 % butter; (closed squares) transesterified blend; (closed triangles) transesterified blend added 3 % butter; (open triangles) transesterified blend added 3 % butter and 0.2 % powder of dry bark orange; (open circles) commercial margarine sample.

Figure 5

Effect of repeated use of biocatalyst. Reaction conditions: an enzyme amount of 1000 IU, a PS/PO mass ratio of 40/60 and an incubation time of 24 h.