Synergistic Effects during Physical Refining of Palm Oil to Mitigate the Formation of Monochloropropanediols

Abstract

The aim of this study is to assess the synergy of mitigating main chlorine sources in palm oil and the oil refining conditions in a lab-scale physical refining process. Mitigation concepts including centrifugation and washing steps are integrated into the physical refining protocol and the MCPD levels in the fully refined oils are determined. The endogenous chlorine content of the crude oil and that of the bleaching clay is confirmed to predominantly impact MCPD formation in this refining process. Residual sediments are shown to induce up to 1 ppm MCPD in the fully refined oils. Residual chlorine content of bleaching clay is shown to increase MCPD content of the oil twofold. t-Test statistical analysis confirms significant effect of centrifugation, phosphoric acid content, clay type and clay washing on the formation of MCPD. Centrifugation is shown to effectively reduce the chlorine source coming from the sediments, while clay washing is shown to effectively reduce the chlorine source coming from the bleaching clay. These mitigation effects are confirmed both in sealed ampoule tests and in deodorizer experiments. Practical Applications: A combined application of strong centrifugation and clay washing is recommended to potentially improve the MCPD content of physically refined palm oil.

Palm Oil Processing and Controversies over Its Health Effect: Overview of Positive and Negative Consequences

“…Recently, Hew et al 34) , reported the effectiveness of using optimal dose of different leaching earth in reducing 3-MCPDE and GE 34) . Strong centrifugation and clay washing are also suggested as an effective means of lowering level of MCPDE content of refine oil 35) . More recently, Oey et al 24) achieved 87％ reduction in GE by using double refining with highlow deodorization temperature.…”

Auxiliary Degumming and Pressurized High Temperature Water Washing to Mitigate the Formation of Monochloropropanediols in Palm Oil

“…The purpose of water washing was two-fold: on one hand to reduce the chloride content of the clay as reported previously [27] and on the other hand to reduce the acidity of the clay. This latter was followed by measuring the pH of the washing water obtained from the 10% suspension of the original and washed clays.…”

“…Clearly, the acidic conditions either introduced during the degumming process or as a result of high free fatty acid (FFA) content of the crude oil, favor the formation of MCPD and water-based degumming can lead to less MCPD. [16,19,20,26,27] Literature also reports about investigations on the role of the bleaching clay acidity in the formation of these process contaminants, however controversially while some of these studies found mitigation benefits using acid activated clays, [16] others did not. [18] From the theoretical point of view, however, both of these findings may be correct since both the input oil and the bleaching clay contribute to the overall manifested MCPD levels.…”

“…For example, using a high quality, low acid and low chlorine containing oil as input makes the contribution of the clay more noticeable. [27] Increased MCPD levels may be observed due to the use of acid activated clays either because the clay releases acid into the oil to be deodorized or the clay releases its residual chlorine into the oil or both.…”

“…[29] There is accumulating evidence, that the upfront purification of the crude oil from residual sediments and trace chlorine carriers can be beneficial in preventing the formation of MCPD. [27,30] In this regard, the composition of the sediment indicates that the phospholipid fraction correlates with the chlorine content. Furthermore, recent trials attempting to trap the chlorine carriers suggest that amphiphilic substances likely have a direct or indirect chlorine trapping capability, which may be leveraged for MCPD mitigation purposes.…”