The Study On Changes Of Esters Of Monochloro Propanediol And Glycidyl Esters And Their Influencing Factors During Deep Fying

Esters of 3-monochloro-1,2-propanediol?3-MCPD esters?,esters of 2-monochloro-1,3-propanediol?2-MCPD esters?and glycidyl esters?GEs?are contaminants in edible oils and oil-based products.They are widely concerned because they may be deesterified in vivo to form products with nephrotoxicity,reproductive toxicity or genotoxicity.3-MCPD esters and 2-MCPD esters collectively referred to as monochloro propanediol esters?MCPD esters?.MCPD esters and GEs can be easily formed under high temperatures.Therefore,frying industry should pay more attention on it since frying is conducted under high temperatures and uses a large amount of oil.This study explored the changes of MCPD esters and GEs during deep frying,analyzed and explored factors affecting the changes form oil oxidation and potential precursors.The main contents are as follows:?1?The frying systems of high-oleic acid sunflower oil?HOSO?,high-oleic acid rapeseed oil?HORO?,and rapeseed oil?RO?frying fish steaks,nuggets,and HOSO frying French fries were chosen,and GC-MS was used to detect the content the MCPD esters and GEs.The results showed that:in fish steaks frying system,3-MCPD esters decreased after increasing with the frying time,and no significant change at frying 60⁷2 h.The 3-MCPD ester content reached the maximum?2.22².70 mg/kg?at 12 h;2-MCPD esters increased to 0.69⁰.81 mg/kg at first24h and then decreased.In nuggets frying system,3-MCPD esters increased at first 12 h and then decreased in HOSO and RO frying wheares 3-MCPD esters almost unchanged after increasing at first 12 h in HORO;2-MCPD esters increased at 12 h firstly and almost unchanged in HOSO and HORO frying,wheares 2-MCPD esters decreased after increasing in RO frying.In French fry frying system,3-MCPD esters decreased after increasing at first 12 h?to0.41mg/kg?with the frying time,and no significant change at frying 36¹20 h.Frying time affected MCPD esters most while oil types and food also have effect.A great linear correlation was observed between 3-MCPD esters and 2-MCPD esters during the frying which R² were0.793.GEs declined with frying time,and the sharpest decrease was mainly taken place in the previous 12 h frying,and the decline rate in the previous 12 h of GEs was sorted as follow:fish steaks>nuggets>French fries;oils with higher oleic acid content>oils with lower oleic acid content.?2?The correlation between MCPD esters,GEs and oil deterioration index was conducted.The results showed that 3-MCPD esters and 2-MCPD esters had great correlation with peroxide value?POV??r=0.633⁰.758?and p-anisidine value?p-AnV??r=0.539⁰.583?;2-MCPD ester had significant correlation with oxidation product from total polar compounds?TPCs??P<0.01?.Changes in 3-MCPD esters and 2-MCPD esters contents may be related to oil oxidation.GEs had signicifantly?P<0.05?or extremely signicifantly?P<0.01?negative correlation with acid value?AV?,POV,p-AnV,TPCs and composition of polar compounds?r=-0.788^-0.471?.?3?Fe₂?SO₄?₃ and tert-Butylhydroquinone?TBHQ?were used to explore the effect of oil oxidation on MCPD esters;besides the effect of potential precursor?chloride types,NaCl,monoglyceride?MAG?and water?were also investigated.The results showed that Fe³⁺promoted the formation of MCPD esters,and the higher Fe³⁺content,the higher MCPD esters content;1⁴ mg/g Fe₂?SO₄?₃ content of could increase the contents of 3-MCPD esters and 2-MCPD esters by 9.69²1.10 fold and 10.64²3.79 fold,respectively.TBHQ inhibited the formation of 3-MCPD esters,the inhibition rate was 16.28%²2.16%;TBHQ had no obvious effect on 2-MCPD esters.Different chloride types promoted the formation of MCPD esters,the promotion effect were as followe:FeCl₃>FeCl₂>MgCl₂>NaCl>KCl.NaCl content of0.25%¹%could promote the formation of 3-MCPD esters,but formation of 3-MCPD esters was reduced when NaCl content was too high?5%?,and NaCl content had no significant effect on 2-MCPD esters.MAG promoted the formation of MCPD esters,and the promotion effect was positively correlated with MAG content;the maximum production of 3-MCPD esters?3 h?in the 0.5%to 1%MAG system increased by 73%to 207%;the maximum production of 2-MCPD ester was increased?5 h?by 108%to 121%.The water content contributed to the formation of MCPD esters while MCPD esters contents were higher in system with 10%water content than 2%water content.GEs content in frying system was near the detection limit,and the influence of various factors on the formation of GEs was not obvious.