Abstract: The purpose of the present study was to investigate the effect of chloride ion content on the contents 3-monochloro-1,2-propanediol esters (3-MCPD esters) and glycidyl esters (GES) during the deodorization of soybean oil. The chloride ion contents of the water source of steam used directly for the deodorization of soybean oil was analyzed. The deodorization was carried out by distillation with steams of different chloride ion contents and we determined the contents of chloride ion, 3-MCPD esters and GES in soybean oil before and after deodorization. The results showed that the chloride ion content in the steam increased with the increase of chloride ion content in the water, and the retention rate of chloride ion in the water was about 0.1%. When the content of chloride ion in the steam was increased from 1–10 to 50–200 mg/L, the content of 3-MCPD esters in deodorized oil was increased by 2.6 times, while the content of chloride ion in deodorized oil did not rise. Increasing chloride ion content in undeodorized oil resulted in increased contents of 3-MCPD ester and GEs after deodorization. The contents of 3-MCPD ester and GEs in deodorized oil were 4.49–7.84 and 14.88–19.84 mg/kg, respectively, when 0.5–5 mL of sodium chloride solution at a concentration of 100 mg/L (the final concentration in the oil was 1–10 mg/kg) was added before deodorization, which were 5.5–9.5 and 5.8–7.7 times higher than in undeodorized oil. Therefore, controlling or reducing the chloride ion content during the deodorization process plays an important role in reducing the contents of 3-MCPD ester and GEs in deodorized oil.

Key words: oil, deodorization, chloride ion, 3-chloro-1,2-propanediol esters, glycidyl ester