Diacylglycerol (DG) is a structural lipid, in which fatty acids in triglycerides (TG) are replaced by hydroxyl groups. Diglyceride is a trace component in natural vegetable oil, an endogenous intermediate product of body fat metabolism, and a recognized safe (GRAS) food component. Recent studies show that diglyceride has many unique physiological functions and physical and chemical properties, and can be widely used in chemical products such as food, medicine and cosmetics. It is a new chemical raw material with great development prospect. In this paper, the enzymatic alcoholysis and hydrolysis of diglyceride and the preparation of enzymatic hydrolysis assisted by ultrasonic external force field were studied.

Firstly, the preparation of diglycerides from palm oil by enzymatic glycolysis was studied. The results showed that the molar ratio of palm oil to glycerol substrate was 2: 1, the amount of enzyme was 8% of the weight of oil, the amount of glycerol was 0%, the reaction temperature was 42℃, and the reaction was slow. After 30h, the mass fraction of DG reached 40%. At the same time, it was found that the formation rate of free fatty acids in the system was faster, especially in the initial 12 hours. There is no water added in the system, and the water involved in the reaction mainly comes from the water existing in enzymes and oils, both of which have low water content. In this case, the hydrolysis reaction is faster, which shows that the enzyme has strong ability to catalyze the hydrolysis reaction. Because enzymatic hydrolysis is easy to carry out, the preparation of DG by enzymatic hydrolysis is studied below.

The results showed that under the condition of mechanical stirring, the optimum conditions of enzymolysis were as follows: the molar ratio of substrate (water: palm oil) 1. 1, the amount of enzyme added was 6% of the weight of oil, the reaction temperature was 42℃, and the reaction time was 4 hours. The content of diglyceride in the product reached 42.6%. The experiment shows that the enzymatic hydrolysis reaction is much faster than the alcoholysis reaction of glycerol, and the yield of diglyceride is high.

In order to further accelerate the reaction speed, the hydrolysis of palm oil catalyzed by lipase to prepare diglycerides was tested under the action of ultrasound. The results showed that when the molar ratio of substrate (water: palm oil) was 1. 1, the amount of enzyme was 6% of the weight of oil, the reaction temperature was 37℃, the ultrasonic power was 50W, and the reaction time was only 2h, the content of diglyceride in the product reached 50.72%.

Key words: ultrasonic diglyceridase catalyzes glycerol hydrolysis of diglyceride lipase

Abstract: diglyceride (DG) is a structural lipid of triglyceride (TG)sn- 1, 2,3-hydroxy substituted acyl group. DG is a natural trace component of various edible oils and an endogenous intermediate metabolite of lipids. In addition, it is generally considered safe by FDA (GRAS). Recent studies show that diglycerides can be widely used in food, medicine, cosmetics and other chemical products because of their special physiological functions and physical and chemical properties. Diglyceride is a new and promising chemical product. In this paper, the preparation of DG under different conditions was studied.

Firstly, the preparation of DG from palm oil by enzymatic glycerol alcoholysis was studied. The results showed that under the conditions of mechanical stirring, the ratio of palm oil to glycerol was 2: 1, the lipase content was 8%, the water content of glycerol was 0%, the reaction temperature was 42℃, and the reaction time was 30h, the content of diglyceride in the product was only about 40%. At the same time, the results show that the enzymatic hydrolysis reaction is more powerful than the enzymatic glycolysis reaction.

Secondly, the process of preparing DG by enzymatic hydrolysis of palm oil under mechanical stirring was studied. Through single factor experiment, the optimum reaction conditions were as follows: oil-water ratio 1∶ 1. 1, lipase content 6%, reaction temperature 42℃ and reaction time 4 h. Under these conditions, the DG content is 42.62%.

Thirdly, the technology of preparing DG by enzymatic hydrolysis of palm oil in ultrasonic field was studied. The optimum reaction conditions were as follows: the ratio of palm oil to water 1∶ 1. 1, lipase content 6%, reaction temperature 37℃, ultrasonic power 50W and reaction time 2h. Under the above conditions, the DG content is 50.72%.

Key words: diacylglycerol (DG); Lipase; Glycerol alcoholysis; Hydrolysis; Ultrasonic catalogue

1 Introduction 1

1. 1 Preface 1

Composition, structure and function of 1.2 diglyceride 1

Composition and structure of diglyceride 1.2. 1 1

1.2.2 Physiological function of diglyceride 2

Application of 1.3 diglyceride 3

1.3. 1 Application of diglycerides in food additives 3

1.3.2 Application of diglyceride in medicine 4

1.3.3 Application of diglyceride in cosmetics 4

1.3.4 Other applications 4

Various preparation methods of 1.4 diglyceride 5

Chemical preparation method of 1.4. 1 diglyceride 5

Enzymatic preparation of 1.4.2 diglyceride 6

Characteristic analysis of various preparation methods of 1.4.3 diglyceride 8

1.4.4 Analysis method of diglyceride 9

1.5 ultrasonic wave and its application in enzyme reaction

1.5. 1 ultrasonic 10

1.5.2 ultrasonic working principle

1.5.3 Application of ultrasonic wave in enzymatic reaction 12

1.6 project research content 13

2 determination method 14

2. 1 sample preparation 14

2.2 Determination of hydroxyl value 14

2.2. 1 configuration of acetylating reagent 14

2.2.2 Determination Steps 14

2.3 Determination of Monoglycerides 14

2.4 Determination of free glycerol content 15

2.5 determination of free fatty acids 15

2.6 The content of diglyceride is 16.

2.7 The triglyceride content is 16.

Preparation of diglycerides 17 by enzymatic alcoholysis and hydrolysis of palm oil glycerol

3. 1 test materials and instruments 18

3. 1. 1 test material 18

3. 1.2 test instrument 18

3.2 test method 18

3.2. 1 enzymatic alcoholysis of glycerol 18

3.2.2 Enzymatic Hydrolysis 19

3.3 Results and discussion 19

3.3. 1 Factors affecting enzymatic glycolysis of glycerol 19

3.3.2 Influencing factors of enzymatic hydrolysis reaction 20

Effect of (1) reaction time on the yield of diglyceride 20

(2) The effect of enzyme dosage on the yield of diglyceride 20.

(3) Effect of reaction temperature on the yield of diglyceride 2 1

(4) Effect of substrate molar ratio on the yield of diglyceride 22.

3.4 Conclusion 23

Preparation of diglyceride 24 by enzymatic hydrolysis in ultrasonic field

4. 1 test materials and instruments 24

4. 1. 1 test material 24

4. 1.2 test instrument 24

4.2 Test Method 25

4.3 Results and discussion 25

4.3. 1 Effect of ultrasonic power on the yield of diglycerides 25

4.3.2 Comparison of ultrasonic field and mechanical stirring conditions 26

4.4 Conclusion 27

5 Conclusion and prospect 28

5. 1 conclusion 28

5.2 Existing Problems and Prospects 28

Reference 29

Abstract 3 1

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