Effects of Deep-Fat Frying Methods and Foodstuffs on Contents of 3-Monochloropropane-1,2-diol Esters and Glycidyl Esters in Frying Peanut Oil
LIU Yulan, LIU Hailan, HUANG Huina, MA Yuxiang, AN Jun, WANG Manyi
2019, 40(11):
42-48.
doi:10.7506/spkx1002-6630-20180504-042
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Different foodstuffs (deep-fried dough sticks, French fries, chicken wings, tofu and blank control) were subjected to different deep-fat frying methods: 32 h continuous frying and intermittent frying for a total of 15 h. Sampling was carried out during these processes for determination of the contents of polar components (PC), 3-monochloropropane-1,2-diol esters (3-MCPDE) and glycidyl esters (GEs) in the frying peanut oil. The purpose of this study was to investigate the effect of different frying methods and foodstuffs on the contents of 3-MCPDE and GE esters in the frying oil. The results showed that the content of 3-MCPDE in peanut oil when used for consecutive deep-fat frying of deep-fried dough sticks, French fries, chicken wings, tofu and blank control increased from an initial value of 0.84 to the maximum value of 2.08, 2.96, 17.45, 7.12 and 8.02 mg/kg after 12, 4, 12, 16 and 8 h, respectively, followed by a decrease afterwards, and the content of GEs increased from an initial level of 2.43 to 20.80, 7.20, 5.00, 2.10 and 66.34 mg/kg at the end of the 32 h frying period, respectively. When PC reached the national standard limit of 27%, the sum of 3-MCPDE and GEs in different frying oils followed the decreasing order of blank control (66.51 mg/kg) > deep-fried dough sticks (21.48 mg/kg) > tofu (12.93 mg/kg) > French fries (8.51 mg/kg) > chicken wings (6.60 mg/kg). The contents of 3-MCPDE in frying oils from French fries, chicken wings, tofu, deep-fried dough sticks and blank control increased to 9.96, 2.17, 4.60, 11.02 and 5.41 mg/kg over the first 3 h of intermittent frying, and were 3.51, 1.58, 12.88, 11.81 and 3.72 mg/kg, respectively at the end. The content of GEs increased from 2.43 to 46.47, 9.06, 9.00, 40.36 and 47.05 mg/kg over the 15 h intermittent frying period, respectively. After 15 h of intermittent frying, none of the five frying oils had a PC content exceeding the national standard limit, and the sum of 3-MCPDE and GEs was in the descending order of chicken wings (52.17 mg/kg) > blank control (50.87 mg/kg) > deep-fried dough sticks (49.98 mg/kg) > tofu (21.88 mg/kg) > French fries (10.64 mg/kg). The increase in the sum of 3-MCPDE, GEs and PC over the 32 h consecutive frying period was ranked in the decreasing order of blank control > deep-fried dough sticks > French fries > chicken wings > tofu, while that over the 15 h intermittent frying period in the decreasing order of chicken wings > deep-fried dough sticks > blank control > tofu > French fries. For each food stuff, the increase in the sum of 3-MCPDE, GEs and PC in the 16 h continuous frying oil was lower than that in the 15 h intermittent frying oil. In summary, the health risk of 3-MCPDE and GEs formed during deep-fat frying should be taken seriously.