Diglyceride vegetable oil preparation process capable of reducing content of 3-chloropropanol ester

Abstract

The invention relates to the technical field of vegetable oil processing, in particular to a diglyceride vegetable oil preparation process capable of reducing the content of 3-chloropropanol ester, which comprises the following steps: adding degummed oil obtained after alkali refining degumming into a short-path distiller, and carrying out primary molecular distillation to obtain crude distilled oil; mixing the crude distilled oil with activated clay, and decolorizing to obtain decolorized oil; pouring the decolored oil into a rotary wiped film type molecular distiller for secondary molecular distillation to obtain a diglyceride vegetable oil semi-finished product; carrying out deodorization treatment on the diglyceride vegetable oil semi-finished product by adopting a double-tower double-temperature sectional deodorization process to obtain deodorized oil; and crystallizing the deodorized oil in a crystallizing tank, growing crystal, filtering and dewaxing to obtain the diglyceride vegetable oil. The diglyceride vegetable oil is prepared by performing molecular distillation twice in the refining process, deodorizing and then performing the dewaxing process, so that the content of 3-chloropropanol ester can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of vegetable oil processing, and particularly relates to a preparation process of diglyceride vegetable oil capable of reducing the content of 3-chloropropanol esters. Background Art

[0002] Untreated crude vegetable oil (such as crude corn oil, crude soybean oil, crude rapeseed oil, etc.) can be processed through refining processes such as degumming, decolorization, and dewaxing to prepare diglyceride vegetable oil. Diglyceride vegetable oil is rich in unsaturated fatty acids and vitamin E, has high nutritional value and health care functions, and is often called high-quality health care oil. However, during the refining process, diglyceride vegetable oil is prone to form 3-chloropropanol esters (3-MCPD esters). 3-chloropropanol esters are potential food safety hazard factors, and their toxicological data are not yet complete. Research shows that 3-chloropropanol esters entering the human body can be hydrolyzed by intestinal pancreatic lipase to generate free 3-chloropropanol, which can then harm human health.

[0003] Currently, the removal of 3-chloropropanol esters mainly starts from the crude oil end, and by changing and optimizing the process conditions of the oil refining process, the formation of 3-chloropropanol esters is reduced. For example, the invention patent CN106281672A discloses a method for reducing 3-chloropropanol esters in oil by contacting the oil with an antioxidant and / or an antioxidant derivative. The invention patent CN104694250A discloses a method for reducing 3-chloropropanol esters in oil by adding one or more antioxidants to the oil after decolorization or before deodorization and then performing deodorization. Both of these methods involve adding a large amount of antioxidants to the oil, which will cause the residue of antioxidants and a significant increase in production costs. The invention patent CN103525550A discloses a deodorization method for reducing the content of 3-chloropropanol esters in vegetable oil, but the content of 3-chloropropanol esters in the oil treated by this method is at least 70 ppm, which is still very high. Summary of the Invention

[0004] Aiming at the technical problems in the prior art that the addition of antioxidants during the removal of 3-chloropropanol esters is likely to cause residues and the removal effect of 3-chloropropanol esters is not good, the present invention provides a preparation process of diglyceride vegetable oil capable of reducing the content of 3-chloropropanol esters.

[0005] The technical solution of the present invention is as follows: A preparation process of diglyceride vegetable oil with reduced 3-monochloropropanediol ester content, adding the degummed oil obtained after alkali refining and degumming into a short-path distiller for the first molecular distillation to obtain a crude distillate oil; mixing the crude distillate oil with activated clay and decolorizing to obtain a decolorized oil; pouring the decolorized oil into a rotary thin-film molecular distiller for the second molecular distillation to obtain a semi-finished diglyceride vegetable oil; adopting a two-column and two-temperature staged deodorization process to deodorize the semi-finished diglyceride vegetable oil to obtain a deodorized oil; and crystallizing, ripening, and filtering and dewaxing the deodorized oil in a crystallization tank to obtain the diglyceride vegetable oil. Among them, the distillation temperature of the first molecular distillation is 190 - 220 °C, the rotation speed is 200 - 250 r / min, the vacuum pressure is controlled at 4 - 5 Pa, and the feed rate is 50 - 60 mL / min. For the second molecular distillation, the temperature of the evaporation surface of the rotary thin-film molecular distiller is 150 - 160 °C, the scraping rate is 200 - 220 r / min, the temperature of the condensation surface of the built-in condenser is 40 - 45 °C, and the vacuum degree is 2 - 2.5 Pa.

[0006] Furthermore, the alkali refining and degumming is that crude vegetable oil is acid-treated with food-grade phosphoric acid with a concentration of 75% - 76%, and then alkali solution is added for neutralization and centrifugation to obtain the degummed oil.

[0007] Furthermore, the addition amount of the food-grade phosphoric acid is 0.1% - 0.2% of the mass of the crude vegetable oil, and the acid treatment time is 20 - 30 min.

[0008] Furthermore, the Baume degree of the alkali solution is 30 - 35 °Bé, and the neutralization reaction time is 20 - 30 min.

[0009] Furthermore, in the decolorization step, the addition amount of the activated clay is 1.2% - 1.5% of the mass of the crude distillate oil, and the decolorization temperature is 45 - 50 °C.

[0010] Furthermore, in the two-column and two-temperature staged deodorization process, the temperature of the large tower of the deodorization equipment is set at 200 - 210 °C, and the reaction time is 40 - 50 min; the temperature of the soft tower of the deodorization equipment is set at 220 - 230 °C, and the reaction time is 15 - 20 min.

[0011] Furthermore, before entering the crystallization tank, the deodorized oil first enters a water heat exchanger to be cooled to 45 - 50 °C, and then enters an ice water heat exchanger to be cooled to 25 - 27 °C.

[0012] Furthermore, the crystallization temperature is 20 - 23 °C, and the ripening time is 20 - 22 h.

[0013] The beneficial effects of the present invention are as follows: The present invention provides a preparation process of diglyceride vegetable oil with reduced 3-monochloropropanediol ester content, which does not require additional addition of antioxidants to reduce the content of 3-monochloropropanediol ester, avoiding the risk of excessive antioxidant residues. Instead, molecular distillation is carried out under certain conditions using a short-path distiller and a wiped-film molecular distiller before and after decolorization respectively, and a dewaxing process is connected after the deodorization step to effectively reduce the content of 3-monochloropropanediol ester. The content of 3-monochloropropanediol ester in the obtained diglyceride vegetable oil can be reduced to less than 0.39 mg / kg, and the safety risk of the refined oil is lower. Detailed implementation mode

[0014] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0015] Example 1 A preparation process of diglyceride corn oil with reduced 3-monochloropropanediol ester content, comprising the following steps: (1) Alkali refining and degumming: First, heat the crude corn oil obtained by pressing to 45°C, then add food-grade phosphoric acid with a concentration of 75%, and the addition amount is 0.1% of the mass of the crude corn oil. The acid treatment time is 20 min. The mixture after acid treatment is subjected to a neutralization reaction. The Baume degree of the lye is 30°Bé, and the neutralization reaction time is 20 min. After the neutralization reaction, centrifugation is carried out to obtain degummed oil; (2) First molecular distillation: Add the degummed oil to a short-path distiller for heating. The distillation temperature is 190°C, the rotation speed is 200 r / min, the vacuum pressure is 4 Pa, and the sample injection amount is 50 mL / min to obtain crude distilled oil; (3) Decolorization: Uniformly mix the crude distilled oil and activated clay. The addition amount of activated clay is 1.2% of the mass of the crude distilled oil. Decolorize at a temperature of 45°C for 10 h, and then centrifuge to obtain decolorized oil; (4) Second molecular distillation: Pour the decolorized oil into a wiped-film molecular distiller for molecular distillation to obtain a semi-finished product of diglyceride corn oil; the temperature of the evaporation surface of the wiped-film molecular distiller is 150°C, the scraping rate is 200 r / min, the temperature of the condensation surface of the built-in condenser is 40°C, and the vacuum degree is 2 Pa; (5) Deodorization: Use a two-tower and two-temperature staged deodorization process to deodorize the semi-finished product of diglyceride corn oil. The temperature of the large tower of the deodorization equipment is set to 200°C and the reaction is carried out for 40 min. The temperature of the soft tower of the deodorization equipment is set to 220°C and the reaction is carried out for 15 min to obtain deodorized oil; (6) Dewaxing: Add the deodorized oil to a water heat exchanger to cool it down to 50°C, then enter an ice water heat exchanger to cool it down to 25°C, and then enter a crystallization tank for crystallization. The crystallization temperature is 20°C. Add a filter aid for crystal growth. The crystal growth time is 20 h. Finally, filter through a filter press to obtain diglyceride corn oil.

[0016] Example 2 A preparation process of diglyceride corn oil capable of reducing the content of 3-chloropropanol esters, comprising the following steps: (1) Alkaline refining and degumming: First, heat the crude corn oil obtained by pressing to 50°C, then add food-grade phosphoric acid with a concentration of 76%. The addition amount is 0.2% of the mass of the crude corn oil. The acid treatment time is 30 min. The mixture after acid treatment is subjected to a neutralization reaction. The Baume degree of the lye is 35°Bé, and the neutralization reaction time is 30 min. After the neutralization reaction, centrifuge to obtain degummed oil; (2) First molecular distillation: Add the degummed oil to a short-path distiller for heating. The distillation temperature is 220°C, the rotation speed is 250 r / min, the vacuum pressure is 5 Pa, and the feed rate is 60 mL / min to obtain crude distilled oil; (3) Decolorization: Uniformly mix the crude distilled oil and activated clay. The addition amount of activated clay is 1.5% of the mass of the crude distilled oil. Decolorize at a temperature of 50°C for 12 h, and then centrifuge to obtain decolorized oil; (4) Second molecular distillation: Pour the decolorized oil into a rotary wiped film molecular distiller for molecular distillation to obtain a semi-finished product of diglyceride corn oil. The temperature of the evaporation surface of the rotary wiped film molecular distiller is 160°C, the wiping rate is 220 r / min, the temperature of the condensation surface of the built-in condenser is 45°C, and the vacuum degree is 2.5 Pa; (5) Deodorization: Adopt a two-column and two-temperature staged deodorization process to deodorize the semi-finished product of diglyceride corn oil. The temperature of the large tower of the deodorization equipment is set at 210°C and the reaction time is 50 min. The temperature of the soft tower of the deodorization equipment is set at 230°C and the reaction time is 20 min to obtain deodorized oil; (6) Dewaxing: Add the deodorized oil to a water heat exchanger to cool it down to 45°C, then enter an ice water heat exchanger to cool it down to 27°C, and then enter a crystallization tank for crystallization. The crystallization temperature is 23°C. Add a filter aid for crystal growth. The crystal growth time is 22 h. Finally, filter through a filter press to obtain diglyceride corn oil.

[0017] Example 3 A preparation process of diglyceride soybean oil capable of reducing the content of 3-chloropropanol esters, comprising the following steps: (1)Alkali refining and degumming: First, heat the crude rapeseed oil obtained by pressing to 40 °C, then add food-grade phosphoric acid with a concentration of 76% for acid treatment. The addition amount is 0.2% of the mass of the crude rapeseed oil, and the acid treatment time is 25 min. The mixture after acid treatment is subjected to a neutralization reaction. The Baume degree of the lye is 33 °Bé, and the neutralization reaction time is 30 min. After the neutralization reaction, centrifugation is carried out to obtain degummed oil; (2)First molecular distillation: Add the degummed oil to a short-path distiller for heating. The distillation temperature is 200 °C, the rotation speed is 210 r / min, the vacuum pressure is 5 Pa, and the sample injection amount is 55 mL / min to obtain crude distilled oil; (3)Decolorization: Uniformly mix the crude distilled oil and activated clay. The addition amount of activated clay is 1.5% of the mass of the crude distilled oil, and decolorize at a temperature of 50 °C for 12 h, then centrifugation to obtain decolorized oil; (4)Second molecular distillation: Pour the decolorized oil into a rotary thin-film molecular distiller for molecular distillation to obtain a diglyceride rapeseed oil semi-finished product; The temperature of the evaporation surface of the rotary thin-film molecular distiller is 155 °C, the scraping rate is 210 r / min, the temperature of the condensation surface of the built-in condenser is 45 °C, and the vacuum degree is 2.5 Pa; (5)Deodorization: Adopt a two-column and two-temperature staged deodorization process to deodorize the diglyceride rapeseed oil semi-finished product. The temperature of the large tower of the deodorization equipment is set at 210 °C and reacts for 50 min. The temperature of the soft tower of the deodorization equipment is set at 230 °C and reacts for 20 min to obtain deodorized oil; (6)Dewaxing: Add the deodorized oil to a water heat exchanger to cool it to 45 °C, then enter an ice water heat exchanger to cool it to 27 °C, and then enter a crystallization tank for crystallization. The crystallization temperature is 23 °C, add a filter aid for crystal cultivation, the crystal cultivation time is 22 h, and finally filter through a filter to obtain diglyceride rapeseed oil.

[0018] Referring to the third method of GB 5009.191-2016 "National Food Safety Standard - Determination of the Content of Chloropropanols and Their Fatty Acid Esters in Foods", the content of 3-chloropropanol esters in diglyceride rapeseed oil was indirectly determined by acid hydrolysis method to be 0.39 mg / kg.

[0019] Example 4 A preparation process of diglyceride rapeseed oil with reduced 3-chloropropanol ester content, comprising the following steps: (1)Alkali refining and degumming: First, heat the crude rapeseed oil obtained by pressing to 50 °C, then add food-grade phosphoric acid with a concentration of 75% for acid treatment. The addition amount is 0.1% of the mass of the crude rapeseed oil, and the acid treatment time is 30 min. The mixture after acid treatment is subjected to a neutralization reaction. The Baume degree of the lye is 30 °Bé, and the neutralization reaction time is 20 min. After the neutralization reaction, centrifugation is carried out to obtain degummed oil; (2) First molecular distillation: The degummed oil was added to a short-path distiller and heated. The distillation temperature was 190 °C, the rotation speed was 200 rpm, the vacuum pressure was 4 Pa, and the sample injection rate was 60 mL / min to obtain a crude distillate oil. (3) De-coloring: The crude distillate oil and activated clay were evenly mixed. The addition amount of activated clay was 1.3% of the mass of the crude distillate oil. De-coloring was carried out at a temperature of 45 °C for 12 h, followed by centrifugation to obtain de-colored oil. (4) Second molecular distillation: The de-colored oil was poured into a rotary thin-film molecular distiller for molecular distillation to obtain a semi-finished product of diglyceride rapeseed oil. The temperature of the evaporation surface of the rotary thin-film molecular distiller was 150 °C, the scraping rate was 220 r / min, the temperature of the condensation surface of the built-in condenser was 40 °C, and the vacuum degree was 2 Pa. (5) Deodorization: The semi-finished product of diglyceride rapeseed oil was deodorized by a two-column and two-temperature staged deodorization process. The temperature of the large tower of the deodorization equipment was set at 210 °C and reacted for 50 min. The temperature of the soft tower of the deodorization equipment was set at 230 °C and reacted for 20 min to obtain deodorized oil. (6) Dewaxing: The deodorized oil was added to a water heat exchanger to cool down to 45 °C, then entered an ice water heat exchanger to cool down to 25 °C, and then entered a crystallization tank for crystallization. The crystallization temperature was 23 °C, a filter aid was added for crystal growth, the crystal growth time was 20 h, and finally, it was filtered by a filter press to obtain diglyceride rapeseed oil.

[0020] Referring to the third method of GB 5009.191-2016 "National Food Safety Standard - Determination of the Content of Chloropropanols and Their Fatty Acid Esters in Foods", the content of 3-chloropropanol esters in diglyceride rapeseed oil was indirectly determined by acid hydrolysis method to be 0.36 mg / kg.

[0021] Comparative Example 1 A preparation process of diglyceride corn oil includes the following steps: (1) Alkali refining and degumming: First, the crude corn oil obtained by pressing was heated to 45 °C, and then food-grade phosphoric acid with a concentration of 75% was added for acid treatment. The addition amount was 0.1% of the mass of the crude corn oil, and the acid treatment time was 20 min. The mixture after acid treatment was subjected to a neutralization reaction. The Baume degree of the lye was 30 °Bé, and the neutralization reaction time was 20 min. After the neutralization reaction, centrifugation was carried out to obtain degummed oil. (2) De-coloring: The degummed oil and activated clay were evenly mixed. The addition amount of activated clay was 1.2% of the mass of the crude distillate oil. De-coloring was carried out at a temperature of 45 °C for 10 h, followed by centrifugation to obtain de-colored oil. (3) Molecular distillation: Pour the decolorized oil into a rotating wiped film molecular distillation apparatus to obtain a semi-finished product of diglyceride corn oil through molecular distillation; the temperature of the evaporation surface of the rotating wiped film molecular distillation apparatus is 150 °C, the wiping rate is 200 r / min, the temperature of the condensation surface of the built-in condenser is 40 °C, and the vacuum degree is 2 Pa; (4) Deodorization: Use a two-column and two-temperature staged deodorization process to deodorize the semi-finished product of diglyceride corn oil. The temperature of the large column of the deodorization equipment is set at 200 °C and reacts for 40 min. The temperature of the soft column of the deodorization equipment is set at 220 °C and reacts for 15 min to obtain deodorized oil; (5) Dewaxing: Add the deodorized oil to a water heat exchanger to cool it down to 50 °C, then enter an ice water heat exchanger to cool it down to 25 °C, and then enter a crystallization tank for crystallization. The crystallization temperature is 20 °C, add a filter aid for crystal growth, the crystal growth time is 20 h, and finally filter through a filter to obtain diglyceride corn oil.

[0022] Comparative Example 2 A preparation process of diglyceride corn oil, comprising the following steps: (1) Alkali refining and degumming: First, heat the crude corn oil obtained by pressing to 45 °C, then add food-grade phosphoric acid with a concentration of 75%, the addition amount is 0.1% of the mass of the crude corn oil, the acid treatment time is 20 min, and the mixture after acid treatment is subjected to a neutralization reaction. The Baume degree of the alkali solution is 30 °Bé, the neutralization reaction time is 20 min, and after the neutralization reaction, centrifugation is carried out to obtain degummed oil; (2) Molecular distillation: Add the degummed oil to a short-path distillation apparatus for heating, the distillation temperature is 190 °C, the rotation speed is 200 revolutions / min, the vacuum pressure is 4 Pa, and the sample injection amount is 50 mL / min to obtain a crude distilled oil; (3) Decolorization: Uniformly mix the crude distilled oil and activated clay. The addition amount of activated clay is 1.2% of the mass of the crude distilled oil, and decolorize at a temperature of 45 °C for 10 h, then centrifuge to obtain decolorized oil; (4) Deodorization: Use a two-column and two-temperature staged deodorization process to deodorize the decolorized oil. The temperature of the large column of the deodorization equipment is set at 200 °C and reacts for 40 min. The temperature of the soft column of the deodorization equipment is set at 220 °C and reacts for 15 min to obtain deodorized oil; (5) Dewaxing: Add the deodorized oil to a water heat exchanger to cool it down to 50 °C, then enter an ice water heat exchanger to cool it down to 25 °C, and then enter a crystallization tank for crystallization. The crystallization temperature is 20 °C, add a filter aid for crystal growth, the crystal growth time is 20 h, and finally filter through a filter to obtain diglyceride corn oil.

[0023] Comparative Example 3 A preparation process of diglyceride corn oil capable of reducing the content of 3-chloropropanol esters, comprising the following steps: (1)Alkali refining and degumming: First, heat the crude corn oil obtained by pressing to 45°C, then add food-grade phosphoric acid with a concentration of 75% for acid treatment. The addition amount is 0.1% of the mass of the crude corn oil, and the acid treatment time is 20 min. The mixture after acid treatment is subjected to a neutralization reaction. The Baume degree of the lye is 30°Bé, and the neutralization reaction time is 20 min. After the neutralization reaction, centrifugation is carried out to obtain degummed oil; (2)First molecular distillation: Pour the degummed oil into a rotary thin-film molecular distiller for molecular distillation to obtain the initially distilled oil; the temperature of the evaporation surface of the rotary thin-film molecular distiller is 150°C, the scraping rate is 200 r / min, the temperature of the condensation surface of the built-in condenser is 40°C, and the vacuum degree is 2 Pa; (3)Decolorization: Uniformly mix the initially distilled oil and activated clay. The addition amount of activated clay is 1.2% of the mass of the crude distilled oil, and decolorize at a temperature of 45°C for 10 h, then centrifuge to obtain decolorized oil; (4)Second molecular distillation: Pour the decolorized oil into a rotary thin-film molecular distiller for molecular distillation to obtain a diglyceride corn oil semi-finished product; the temperature of the evaporation surface of the rotary thin-film molecular distiller is 150°C, the scraping rate is 200 r / min, the temperature of the condensation surface of the built-in condenser is 40°C, and the vacuum degree is 2 Pa; (5)Deodorization: Adopt a two-column and two-temperature staged deodorization process to deodorize the diglyceride corn oil semi-finished product. The temperature of the large tower of the deodorization equipment is set at 200°C and reacts for 40 min. The temperature of the soft tower of the deodorization equipment is set at 220°C and reacts for 15 min to obtain deodorized oil; (6)Dewaxing: Add the deodorized oil to a water heat exchanger to cool it to 50°C, then enter an ice water heat exchanger to cool it to 25°C, and then enter a crystallization tank for crystallization. The crystallization temperature is 20°C, add a filter aid for crystal growth, and the crystal growth time is 20 h. Finally, filter through a filter press to obtain diglyceride corn oil.

[0024] Comparative Example 4 A preparation process of diglyceride corn oil that can reduce the content of 3-chloropropanol esters, comprising the following steps: (1)Alkali refining and degumming: First, heat the crude corn oil obtained by pressing to 45°C, then add food-grade phosphoric acid with a concentration of 75% for acid treatment. The addition amount is 0.1% of the mass of the crude corn oil, and the acid treatment time is 20 min. The mixture after acid treatment is subjected to a neutralization reaction. The Baume degree of the lye is 30°Bé, and the neutralization reaction time is 20 min. After the neutralization reaction, centrifugation is carried out to obtain degummed oil; (2)First molecular distillation: Add the degummed oil to a short-path distiller for heating. The distillation temperature is 190°C, the rotation speed is 200 revolutions / min, the vacuum pressure is 4 Pa, and the sample injection amount is 50 mL / min to obtain crude distilled oil; (3) Decolorization: The crude distilled oil and activated clay are evenly mixed. The addition amount of activated clay is 1.2% of the mass of the crude distilled oil. Decolorize at 45 °C for 10 h, and then centrifuge to obtain the decolorized oil; (4) Second molecular distillation: Add the decolorized oil to a short-path distiller for heating. The distillation temperature is 190 °C, the rotation speed is 200 r / min, the vacuum pressure is 4 Pa, and the sample injection rate is 50 mL / min to obtain a semi-finished product of diglyceride corn oil; (5) Deodorization: The semi-finished product of diglyceride corn oil is deodorized by a two-column two-temperature staged deodorization process. The temperature of the large column of the deodorization equipment is set at 200 °C and reacts for 40 min. The temperature of the soft column of the deodorization equipment is set at 220 °C and reacts for 15 min to obtain the deodorized oil; (6) Dewaxing: Add the deodorized oil to a water heat exchanger to cool it down to 50 °C, then enter an ice water heat exchanger to cool it down to 25 °C, and then enter a crystallization tank for crystallization. The crystallization temperature is 20 °C, add a filter aid for crystal growth, the crystal growth time is 20 h, and finally filter through a filter press to obtain diglyceride corn oil.

[0025] Comparative Example 5 A preparation process of diglyceride corn oil, comprising the following steps: (1) Alkali refining and degumming: First, heat the crude corn oil obtained by pressing to 45 °C, then add food-grade phosphoric acid with a concentration of 75% for acid treatment. The addition amount is 0.1% of the mass of the crude corn oil. The acid treatment time is 20 min. The mixture after acid treatment is subjected to a neutralization reaction. The Baume degree of the alkali solution is 30 °Bé, and the neutralization reaction time is 20 min. After the neutralization reaction, centrifuge to obtain the degummed oil; (2) First molecular distillation: Add the degummed oil to a short-path distiller for heating. The distillation temperature is 190 °C, the rotation speed is 200 r / min, the vacuum pressure is 4 Pa, and the sample injection rate is 50 mL / min to obtain the crude distilled oil; (3) Decolorization: The crude distilled oil and activated clay are evenly mixed. The addition amount of activated clay is 1.2% of the mass of the crude distilled oil. Decolorize at 45 °C for 10 h, and then centrifuge to obtain the decolorized oil; (4) Second molecular distillation: Pour the decolorized oil into a rotary thin-film molecular distiller for molecular distillation to obtain a semi-finished product of diglyceride corn oil; the temperature of the evaporation surface of the rotary thin-film molecular distiller is 150 °C, the scraping rate is 200 r / min, the temperature of the condensation surface of the built-in condenser is 40 °C, and the vacuum degree is 2 Pa; (5) Deodorization: The semi-finished product of diglyceride corn oil is deodorized by a two-column two-temperature staged deodorization process. The temperature of the large column of the deodorization equipment is set at 200 °C and reacts for 40 min. The temperature of the soft column of the deodorization equipment is set at 220 °C and reacts for 15 min to obtain diglyceride corn oil.

[0026] Comparative Example 6 A preparation process of diglyceride corn oil, comprising the following steps: (1) Alkali refining and degumming: First, heat the crude corn oil obtained by pressing to 45 °C, then add food-grade phosphoric acid with a concentration of 75% for acid treatment, the addition amount is 0.1% of the mass of the crude corn oil, the acid treatment time is 20 min, the mixture after acid treatment is subjected to a neutralization reaction, the Baume degree of the lye is 30 °Bé, the neutralization reaction time is 20 min, and after the neutralization reaction, centrifugation is carried out to obtain degummed oil; (2) First molecular distillation: Add the degummed oil to a short-path distiller for heating, the distillation temperature is 250 °C, the rotation speed is 200 r / min, the vacuum pressure is 3 Pa, and the sample injection amount is 40 mL / min to obtain crude distilled oil; (3) De-coloring: Uniformly mix the crude distilled oil and activated clay, the addition amount of activated clay is 1.2% of the mass of the crude distilled oil, de-color at a temperature of 45 °C for 10 h, and centrifugation to obtain de-colored oil; (4) Second molecular distillation: Pour the de-colored oil into a rotary thin-film molecular distiller for molecular distillation to obtain a semi-finished product of diglyceride corn oil; the temperature of the evaporation surface of the rotary thin-film molecular distiller is 190 °C, the scraping rate is 180 r / min, the temperature of the condensation surface of the built-in condenser is 40 °C, and the vacuum degree is 3 Pa; (5) Deodorization: Adopt a two-tower and two-temperature staged deodorization process to deodorize the semi-finished product of diglyceride corn oil, wherein the temperature of the large tower of the deodorization equipment is set at 200 °C and the reaction is carried out for 40 min, the temperature of the soft tower of the deodorization equipment is set at 220 °C and the reaction is carried out for 15 min to obtain deodorized oil; (6) Dewaxing: Add the deodorized oil to a water heat exchanger to cool it to 50 °C, then enter an ice water heat exchanger to cool it to 25 °C, then enter a crystallization tank for crystallization, the crystallization temperature is 20 °C, add a filter aid for crystal cultivation, the crystal cultivation time is 20 h, and finally filter through a filter to obtain diglyceride corn oil.

[0027] Experimental Example 1 Perform quality inspections on the diglyceride corn oil obtained in Examples 1-2 and Comparative Examples 1-6. Refer to GB5009.209-2016 "Determination of zearalenone in foods" to determine the zearalenone content, refer to GB / T 25223-2010 "Determination of sterol composition and total sterols in animal and vegetable oils and fats" to determine the phytosterol content, refer to GB / T 19111-2017 "Inspection of acid value of corn oil" to determine the insoluble impurity content, and refer to the third method of GB 5009.191-2016 "National Food Safety Standard - Determination of the content of 3-chloropropanol esters in foods", and indirectly determine the content of 3-chloropropanol esters in diglyceride corn oil by means of acid hydrolysis. The results of each test are shown in Table 1.

[0028] Table 1 Quality inspection results of diglyceride corn oil

[0029] As can be seen from Table 1, the zearalenone, sterol content and insoluble impurity content of the diglyceride corn oil prepared in Examples 1-2 and Comparative Examples 1-6 all meet the relevant requirements.

[0030] Regarding the index of 3-monochloropropanediol ester content, in Comparative Example 1, Comparative Example 2 and Comparative Example 4, the processes of the first molecular distillation, the second molecular distillation and dewaxing were respectively omitted in the preparation method, and the 3-monochloropropanediol ester content of the diglyceride corn oil they prepared was significantly higher than that of Examples 1-2. In addition, although the 3-monochloropropanediol ester content of the diglyceride corn oil prepared in Comparative Example 3 was also low, but a rotary wiped film molecular distiller was used in both of its two molecular distillations, which increased the process cost, and the 3-monochloropropanediol ester content did not decrease significantly compared with Examples 1-2. Considering the cost, it is uneconomical. The 3-monochloropropanediol ester content of the diglyceride corn oil prepared in Comparative Example 4 was higher than that in Comparative Example 3. It can be seen that by performing two molecular distillations in a short-path distiller, the removal effect of 3-monochloropropanediol ester was not as good as that of Examples 1-2. In the process of preparing diglyceride corn oil in Comparative Example 6, the conditions of the two molecular distillations were adjusted, and the removal effect of 3-monochloropropanediol ester was also not as good as that of Examples 1-2.

[0031] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all be within the scope of the present invention. / Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention.

Claims

1. A preparation process of diglyceride vegetable oil with reduced 3-monochloropropanediol ester content, characterized in that, The degummed oil obtained after alkali refining and degumming is added to a short-path distiller for the first molecular distillation to obtain a crude distillate oil; the crude distillate oil is mixed with activated bleaching earth and decolorized to obtain a decolorized oil; the decolorized oil is poured into a rotating thin-film molecular distiller for the second molecular distillation to obtain a semi-finished product of diglyceride vegetable oil; the semi-finished product of diglyceride vegetable oil is deodorized by a two-column and two-temperature staged deodorization process to obtain a deodorized oil; the deodorized oil is crystallized, aged, and dewaxed by filtration in a crystallization tank to obtain diglyceride vegetable oil. Among them, the distillation temperature of the first molecular distillation is 190 - 220 °C, the rotation speed is 200 - 250 r / min, the vacuum pressure is controlled at 4 - 5 Pa, and the feed rate is 50 - 60 mL / min. For the second molecular distillation, the temperature of the evaporation surface of the rotating thin-film molecular distiller is 150 - 160 °C, the scraping rate is 200 - 220 r / min, the temperature of the condensation surface of the internal condenser is 40 - 45 °C, and the vacuum degree is 2 - 2.5 Pa.

2. The preparation process of diglyceride vegetable oil capable of reducing the content of 3-chloropropanol esters according to claim 1, characterized in that, Alkali refining and degumming means that crude vegetable oil is acid-treated with food-grade phosphoric acid with a concentration of 75% - 76%, and then alkali solution is added for neutralization and centrifugation to obtain degummed oil.

3. The preparation process of diglyceride vegetable oil capable of reducing the content of 3-chloropropanol esters as described in claim 2, characterized in that, The addition amount of food-grade phosphoric acid is 0.1% - 0.2% of the mass of crude vegetable oil, and the acid treatment time is 20 - 30 min.

4. The preparation process of diglyceride vegetable oil capable of reducing the content of 3-monochloropropanediol esters as claimed in claim 2, wherein The Baume degree of the alkali solution is 30 - 35 °Bé, and the neutralization reaction time is 20 - 30 min.

5. The preparation process of diglyceride vegetable oil capable of reducing the content of 3-chloropropanol esters according to claim 1, characterized in that, In the decolorization step, the addition amount of activated bleaching earth is 1.2% - 1.5% of the mass of the crude distillate oil, and the decolorization temperature is 45 - 50 °C.

6. The preparation process of diglyceride vegetable oil capable of reducing the content of 3-chloropropanol esters as described in claim 1, characterized in that, In the two-column and two-temperature staged deodorization process, the temperature of the large tower of the deodorization equipment is set at 200 - 210 °C, and the reaction time is 40 - 50 min; the temperature of the soft tower of the deodorization equipment is set at 220 - 230 °C, and the reaction time is 15 - 20 min.

7. The preparation process of diglyceride vegetable oil capable of reducing the content of 3-monochloropropanediol esters as described in claim 1, wherein, Before entering the crystallization tank, the deodorized oil first enters a water heat exchanger to be cooled to 45 - 50 °C, and then enters an ice-water heat exchanger to be cooled to 25 - 27 °C.

8. The preparation process of diglyceride vegetable oil capable of reducing the content of 3-chloropropanol esters according to claim 1, characterized in that, The crystallization temperature is 20 - 23 °C, and the aging time is 20 - 22 h.

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