Effects of oxidation and hydrolysis of frying oil on MCPD esters formation in Chinese fried dough sticks

Abstract

In this study, we investigated the influence of various factors on the formation of 2-monochloro-1,3-propanediol and 3-monochloro-1,2-propanediol (MCPD) esters in Chinese fried dough sticks. The results showed types of oil significantly affected the content of MCPD esters in fried dough sticks, with palm oil responsible for the highest. As well, temperature and time affected the content of MCPD esters (P < 0.05). Treatment at 200 °C for 4 min resulted in 1.87 mg/kg 3-MCPD esters and 0.68 mg/kg 2-MCPD esters, respectively. The dough containing 1 g/100 g NaCl was fried at 180 °C for 4 min, resulting in elevated levels of MCPD esters. MCPD esters in fried dough sticks constantly varied during the 8-h cycle in 3 consecutive days and the 12-h frying cycle. Pearson correlation test showed 3-MCPD esters had a positive correlation with 2-MCPD esters (R = 0.920), which allowed 3-MCPD esters to be a representative index of MCPD esters. A good correlation between the acid value (AV), p-anisidine value (p-AnV), color (ΔΕ) of frying oil and MCPD esters in fried dough sticks was also found. The changes of MCPD esters of fried dough sticks were assumed to be caused by oxidation and hydrolysis of oil during frying.