Chloride reduction by water washing of crude palm oil to assist in 3-monochloropropane-1, 2 diol ester (3-MCPDE) mitigation.

ABSTRACT

Chloride reduction in crude palm oil (CPO) of greater than 80% was achieved with water washing conducted at 90°C. Inorganic chloride content in CPO was largely removed through washing, with no significant reduction in the organic chloride. Phosphorous content of CPO reduced by 20%, while trace elements such as calcium, magnesium and iron were also reduced in the washing operation. The 3-MCPDE formed in the refined, bleached and deodorised palm oil displayed (RBDPO) a linear relationship with the chloride level in washed CPO, which could be represented by the equation y = 0.91x, where y is 3-MCPDE and x represents the chloride in RBDPO refined from washed CPO. In plant scale trials using 5% water at 90°C, mild acidification of the wash water at 0.05% reduced chloride by average 76% in washed CPO. Utilising selected bleaching earths, controlled wash water temperature and wash water volume produced low chloride levels in RBDPO. Chloride content less than 1.4 mg kg-1 in plant RBDPO production was achieved, through physical refining of washed CPO containing less than 2 mg kg-1 chloride and would correspond to 3-MCPDE levels of 1.25 mg kg-1 in RBDPO. The 3-MCPDE reduced further to 1.1 mg kg-1 as the chloride level of washed CPO decreased below 1.8 mg kg-1. Chloride has been shown to facilitate the 3-MCPDE formation and its removal in lab scale washing study has yielded lower 3-MCPDE levels formed in RBDPO. In actual plant operations using washed CPO, 3-MCPDE levels below 1.25 mg kg-1 were achieved consistently in RBDPO.