Table 1. Brief information about some studies discussing mitigation of 3-monochloropropane-1,2-diol (3-MCPD) and glycidyl ester (GE) during refining steps.

Oil type	Operation/step	Condition	Effect	Reference
Crude palm oil	Prewashing (applied prior to degumming)	20 min at 70 °C, 10 % deionised water	At the end of the physical refining, 2- and 3-MCPDE (w=0.54 and 1.04 mg/kg, respectively) were 19 and 22 % lower when prewashing was applied	(108)
Crude palm oil	Neutralisation	20 min at 70 °C with 2 L of 33 % NaOH solution	w(3-MCPDE) was reduced by 43 % but w(GE) was doubled	(108)
Crude palm oil	Neutralisation (only the addition of alkali, refining step was not like industrial practice)	1 mmol/kg NaHCO3	w(3-MCPDE) and w(GE) reduced 81 and 84 %, respectively	(5)
Crude palm oil	Neutralisation	KOH and NaOH were used (other conditions not given)	w(3-MCPDE) reduced 35 % and 45 % when NaOH and KOH were used, respectively	(20)
Pre-refined palm oil	Bleaching	w(Tonsil Optimum 214 FF bleaching earth)=0.8 % was added to the oil (90 °C, up to 1 kPa) and removed by filtering after 20 min treatment	w(3-MCPDE and related ester) was reduced from 6.06 to 2.48 mg/kg (59 % reduction)	(89)
Peanut oil (pressed)	Bleaching	The degummed oil was preheated to 95 °C and bleached by adding activated clay (activated by 3 % hydrochloric acid) up to 1 kPa and then filtered after 25 min treatment	w(3-MCPDE) was reduced by approx. 15–22 % after bleaching. Although DGF standard method C-VI 18 (10) of the German Society for Fat Science was used, GE results were not given	(37)
Crude soybean oil	Degumming, neutralisation, bleaching and deodorisation	Use of acid in the degumming stage and acid-activated clay	w(3-MCPDE) increased compared to crude oil	(109)
Crude palm oil	Degumming	Acid degumming (0.06 % of 85 % H3PO4 for 20 min at 90 °C) and water degumming (1 % water, 10 min at 90 °C)	Reduction ranging from 56 to 78 % for w(3-MCPDE) and 49–56 % for w(GE)	(110)
Rice bran oil and palm oil	Bleaching	20 g oil was bleached with 200 mg activated earth at 110 °C and 10 kPa, after 20 min, cooled to 30 °C and filtered	w(GE) of the model oil spiked with different ester forms of glycidol was reduced effectively to ˃0.1 mg/kg	(72)
Crude palm oil	Bleaching	At 105 °C for 20 min with acid-activated bleaching earth (1, 2 and 3 %)	w(3-MCPDE) reduced as bleaching earth content increased	(38)
Crude palm oil	Bleaching	At 95 °C for 20 min with w(clay)=0.5 %	The use of low Cl bleaching earth resulted in lower w(MCPD) than the use of high Cl bleaching earth	(111)
Crude palm oil	Bleaching	w(pure-Flo B80 natural bleaching earth)=10 %	Bleaching reduced 93 % of w(GE) formed during deodorisation, while w(3-MCPDE) were unaffected	(29)
Palm oil	Deodorisation	10 g sample was heated to 200–290 °C for 45–360 min; 20 kg/t steam was purged	Despite the increase in deodorisation temperature to 270 °C, the 3-MCPDE+GE content in the samples increased. Deodorisation for 240-360 min at 290 °C resulted in a decrease in contaminant levels	(20)
Peanut oil (pressed)	Deodorisation	At 220-260 °C up to 3 h under 200 Pa with steam speed of 0.1 g/min	w(3-MCPDE and related matter) were reduced after 2 h of deodorisation	(37)
Crude palm oil	Bleaching	w(zeolite-Fe)=1.5–15 % and different bleaching temperature (60–140 °C)	The most effective bleaching procedure was achieved with a w(zeolite-Fe)=5 % and a bleaching temperature of 80 °C for 30 min	(112)
Palm oil	Bleaching	Using activated carbon treated with a 2 M HCl solution	w(3-MCPD) 80 % reduction and w(GE) 97 % reduction	(113)
Palm oil	Bleaching	Using metal-organic frameworks (MOFs)	The MOFs, which are composed of 2,6-naphthalenedicarboxylic acid (Fe-MIL-88_BDC), exhibited the most effective adsorption capabilities	(114)
Palm oil	Bleaching	Using zeolite	The use of beta zeolites led to the most effective removal of 3-MCPDE (86 %) compared to other zeolites tested. Using a synergistic blend of beta zeolite and AC, the efficiency of removing 3-MCPDE was significantly improved to 94 %, resulting in a simultaneous reduction of 75 % in GE	(115)
Coconut oil	Bleaching	At 105 °C with w(activated clay)=1 %. Bleaching was performed under vacuum. After 30 min, the slurry was allowed to cool (to 50 °C) and filtered	In crude coconut oil w(3-MCPDE) and w(GE) were 0.21 and 0.29 mg/kg, respectively. After bleaching, w(3-MCPDE) remained the same, but w(GE) was reduced to 0.19 mg/kg	(116)
Camellia oil	Degumming, bleaching and deodorisation	Degumming water addition at 2.97 %, bleaching earth (acid activated) 2.69 %, deodorisation temperature 230 °C, deodorisation duration 90 min	w(3-MCPDE) reduced by 76.9 %	(116)
Palm olein oil	Bleaching and deodorisation	Bleaching; 95 °C up to 1 h under 8 kPa using neutral and acid-activated bleaching earth Deodorisation (at 200–230 °C up to 1.5 h under 0.15–0.2 kPa)	Use of neutral bleaching earth and deodorisation at 230 °C led to w(MCPD) reduction of 69.91 %. The glycidol esters may be effectively reduced by up to 93.85 % with the use of acid-activated bleaching earth and deodorisation at a temperature of 230 °C, without the need for neutralisation	(117)
Palm oil	Deodorisation	At 250 °C up to 2 h using 100 g bleached oil	Potassium acetate reduced w(3-MCPDE) almost 99 % and w(GE) 40 %. Sodium hydrogencarbonate, sodium acetate and sodium carbonate were able to lower w(3-MCPDE) by more than 80 %	(118)
Palm oil	Deodorisation	Different temperatures (210–270 °C) and time (30–120 min)	After 30 min at 210 °C, the formation of 3-MCPDE was most pronounced under the mildest conditions	(119)
High oleic sunflower and rapeseed oil	Water washing, degumming, bleaching and deodorisation	Different deodorisation temperatures (220–260 °C), at 70 °C up to 20 min using 0.5 % citric acid for degumming, at 95 °C up to 20 min with 3 different bleaching earth (0.1–2 %)	Double refining successfully decreased w(GE) in high oleic (HO) sunflower and rapeseed oil by 70 and 94 %, respectively	(120)