Abstract
Issues on 3-monochloropropane-diol-1,2-diol (MCPD) esters and glycidyl esters in refined oil have gained much attention when these heat-induced contaminants are associated with health implications. Oil that undergoes the frying process could influence the fates of 3-MCPD esters and glycidyl esters, especially with the addition of an anti-clouding agent. In this study, we investigated the effect of polyglycerol fatty acid esters (PGE) on the transients of 3-MCPD esters and glycidyl esters in palm olein (POo) during intermittent frying. Thermal resistance of POo fortified with PGE (0.1% to 0.4%) was assessed for 8 h of daily frying operations at 180 °C across five consecutive days. The addition of PGE decelerated the reduction of 3-MCPD esters and glycidyl esters with the progression of frying. The presence of these compounds coincided with the amount of oil taken up by the fried product. The inclusion of PGE in POo also induced higher augmentation of polar compound fractions, i.e., oxidised triacylglycerols (OxTAG) and polymerised triacylglycerols (PTAG), but gave comparable free fatty acid (FFA), p-anisidine value (AnV), total chloride and fatty acid composition (FAC) with control oil (POo). The results also showed that the presence of chloride in POo did not onset further formation of 3-MCPD esters and glycidyl esters throughout the frying period. As the behaviours of 3-MCPD esters and glycidyl esters were affected by PGE, only a sufficient amount should be added into POo to ensure oil clarity at a realistic period.
Highlights
Palm olein (POo), which is the liquid fraction of palm oil, is extensively used in commercial cooking and frying attributed by its resistance against high temperatures [1], as well as consistent supply and price competitiveness [2]
Due to health concern associated to heated oils, we report the fates of 3-MCPD esters and glycidyl esters, and the physico-chemical changes occurring in POo upon repeated frying when the oil is fortified with polyglycerol fatty acid esters (PGE) at different dosages, i.e., 0.1%, 0.2%, 0.3% and 0.4%
Increase the PGE dosages of more than 0.1% retarded the decomposition rate of 3MCPD esters even though the final concentration were considerably low at the end of frying session
Summary
Palm olein (POo), which is the liquid fraction of palm oil, is extensively used in commercial cooking and frying attributed by its resistance against high temperatures [1], as well as consistent supply and price competitiveness [2]. As POo has equivalent amounts of saturated and unsaturated fatty acids, a natural occurrence of solid precipitation is expected when the oil is stored at a lower temperature. There are consumers who still perceive cloudy oil as a deteriorated or poor-quality oil, and preclude them from choosing POo [3]. POo experiences crystallisation when the oil is shelved in temperate countries. Incorporation of anti-clouding agent like polyglycerol fatty acid esters (PGE) has proven to delay cloudiness by slowing down crystallisation and improving the oil clarity [4,5].
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