The Effect of Polyglycerol Esters of Fatty Acids on the Crystallization of Palm Olein

Abstract

Introduction Palm oil PO is derived from the mesocarp of the palm fruit and is widely used in food applications. It is semi-solid at room temperature 25 and contains similar levels of saturated and unsaturated fatty acids. Generally, PO presents the crystal habit in β-form, which is usually the most functional polymorph in many fat-based products 1. This characteristic combined with other properties such as plasticity, oxidative stability and trans-fat free ensure its beneficial applications in food products 2. PO may be fractionated into a liquid fraction palm olein: POL and a more solid fraction palm stearin: PS. POL appears clear at ambient temperature of 25 due to its high content of C 18:1 39-45 and C 18:2 10-13 3 and has been identified as a good ingredient for several food formulations. However, its application is often limited by its tendency to form granular crystals and get cloudy at low temperature during longterm storage. The visual observation of these crystals is usually seen as a defect by consumers although there is no deterioration in the oil quality 4 .

A Review on the Fundamentals of Palm Oil Fractionation: Processing Conditions and Seeding Agents

“…The crystallized seeding agents act as a template for crystallization to occur at higher temperatures. [ 24 ] Seeding agents were also able to reduce the onset crystallization temperature. The mechanism is almost similar to how seeding agents increases the nucleation time.…”

“…The opposite effect was observed when PGE rich in unsaturated fatty acid was used whereby the onset crystallization temperature decreases from 5.0 to 4.8 °C. [ 24 ] This could be due to the high unsaturation which increases the solubility of PGE and the kink of unsaturated fatty acid hinders the binding of other TAG molecules. It is important to note that the enhancement of crystallization by PGE is only for the early stage.…”

“…As crystallization proceed, more PGE molecules were incorporated into the crystal and greater surface of the crystal will be occupied by the polyglycerol group, leading to lesser TAG molecules attachment. [ 24 ]…”

“…As the concentration increases above 0.5% in palm olein, enhancement of oil crystallization then started to occur (0.04–0.44 min −1 ) and a reduction in induction time (204.7–74.4 min) was observed. [ 24,78 ] As concentration of PGEmix‐8 increases, the proportion of saturated fatty acids added also increases and is able to crystallize out at higher temperature due to limited solubility. The crystallized PGEmix‐8 then acts as template for heterogeneous nucleation and enhances the crystallization process.…”

“…PGEmix‐8 increases the rate of crystallization leading to production of small crystals that are more uniform but do not show effect on SFC. [ 24,79 ] Thus, it is possible that PGEmix‐8 do not enhance the extend of crystallization but only enhance the rate of crystallization. This reduction in crystal size without change in extend of crystallization is favorable as it leads to lesser loss of olein.…”