2种脱酸工艺对米糠油甘油酯组成及3-氯丙醇酯和缩水甘油酯含量的影响

依据酸价和甘一酯、甘二酯含量降低情况,确定米糠油水蒸气蒸馏脱酸的最佳条件,之后对相同米糠毛油分别进行碱炼脱酸和水蒸汽蒸馏脱酸,再对脱酸米糠油进行蒸馏脱臭,并对其酸价、甘油酯组成及3-氯丙醇酯、缩水甘油酯含量进行检测,对比研究2种脱酸工艺对米糠油甘油酯组成及3-氯丙醇酯和缩水甘油酯含量的影响。结果显示:米糠油水蒸汽蒸馏脱酸的最佳条件为温度250℃、时间100 min;经水蒸汽蒸馏脱酸,米糠油酸价(mgKOH/g)从14.64降低至5.58,甘二酯、甘一酯含量分别从18.18%、4.08%降低至5.78%、1.87%,降幅分别为68.21%、54.17%,3-氯丙醇酯、缩水甘油酯分别从6.28、4.47 mg/kg上升至10.27、7.70 mg/kg;经碱炼脱酸,米糠油酸价降低至0.11,甘二酯、甘一酯含量降低至9.09%、2.45%,降幅分别为50.0%、39.95%,3-氯丙醇酯、缩水甘油酯含量分别上升至7.35、6.67 mg/kg;蒸馏脱酸米糠油再经脱臭,3-氯丙醇酯和缩水甘油酯含量分别升高至16.04、12.94mg/kg,而碱炼脱酸米糠油再经脱臭,3-氯丙醇酯和缩水甘油酯含量分别升高至17.18、13.91 mg/kg,较蒸馏脱酸再脱臭的升幅提高,这可能源于水蒸汽蒸馏脱酸相比于碱炼脱酸能更好地降低待脱臭油脂中3-氯丙醇酯和缩水甘油酯的前体物质即甘一酯和甘二酯含量,但由于水蒸气蒸馏脱酸本身会生成较大量的3-氯丙醇酯和缩水甘油酯,使得待脱臭油脂中的含量很高,致使脱臭后油脂中3-氯丙醇酯和缩水甘油酯的含量仍然很高。因此,如何在降低待脱臭油脂中甘一酯、甘二酯含量的同时减少3-氯丙醇酯和缩水甘油酯含量,或将成为防范和消减米糠油精炼过程3-氯丙醇酯和缩水甘油酯形成需要突破的关键技术问题。

Effects of two deacidification processes on the composition of glycerides and the content of 3-chloropropanol ester and glycidyl ester

Firstly,according to the change of acid value and the removal of monoglycerides and diglycerides,the optimal conditions for steam distillation deacidification of rice bran oil were selected.Then the same rice bran oil was deacidified by alkali deacidification and steam distillation deacidification.Acid value,glycerides composition and content of 3-chloropropanol ester,glycidyl ester of oil samples from two refining processes were determined.The effects of two different deacidification methods on the composition of glycerides and the content of 3-chloropropanol and glycidyl esters were compared.The results showed that the optimum conditions for deacidification by steam distillation of rice bran oil were 250℃and 100 min.After deacidification by steam distillation,acid value(mgKOH/g)of rice bran oil decreased from 14.64 to 5.58,the content of glyceride and glyceride decreased from 18.18%and 4.08%to 5.78%and 1.87%respectively.The 3-chloropropol ester and glycidyl ester increased from 6.28 and 4.47 mg/kg to 10.27 and 7.70 mg/kg,respectively.After deacidification by alkali refining,acid value(mgKOH/g)of rice bran oil was reduced to 0.11,the contents of glyceride and glyceride were reduced to 9.09%and 2.45%,with a decrease of 50.0%and 39.95%,respectively.The contents of 3-chloropropanol ester and glycidyl ester were increased to 7.35 and 6.67 mg/kg,respectively.Distilled deacidified rice bran oil was deodorized,and the content of 3-chloropropanol ester and glycidyl ester increased to 16.04 and 12.94 mg/kg,respectively.Alkali-refined rice bran oil was deodorized,and the content of 3-chloropropanol ester and glycidyl ester increased to 17.18 and 13.91 mg/kg,respectively.This may be due to the fact that steam distillation deacidification can better reduce the content of glyceride and glycidyl ester,the precursors of 3-chloropropanol ester and glycidyl ester,in the deodorized oil than alkali deacidification.However,due to the fact that a large amount of 3-chloropropanol ester and glycidyl ester will be generated by steam distillation deacidification itself,the content of 3-chloropropanol ester and glycidyl ester in the oil after demodulation is was very high.Therefore,how to reduce the contents of glycerin and glycidyl ester while reducing the contents of 3-chloropropanol ester and glycidyl ester in the deodorized oil may become a key technical problem to prevent and reduce the formation of 3-chloropropanol ester and glycidyl ester in the refining process of rice bran oil.