A method for simultaneously preparing Cyperus esculentus starch sugar and Cyperus esculentus oil

Abstract

The present invention discloses a method for simultaneously preparing Cyperus esculentus starch sugar and Cyperus esculentus oil, belonging to the technical field of comprehensive processing of oil crops. The present invention uses Cyperus esculentus as raw material and simultaneously prepares starch sugar and Cyperus esculentus oil through five steps of dry crushing, water washing, liquefaction, saccharification and purification. The present invention adopts the process of dry crushing to minimize the average particle size of Cyperus esculentus powder, and then dissolves non-starch polysaccharides in the bean powder through water washing. After discarding the aqueous phase, the starch with higher purity in the residue phase is liquefied and saccharified to produce glucose syrup, and the oil on the upper layer is collected during the process to complete the extraction of Cyperus esculentus oil. The preparation method of the present invention is simple and has a high preparation yield. The extraction rate of Cyperus esculentus oil reaches 89.40%, the yield of glucose syrup is 90.10%, and the purity is 89.41%.

Description

Technical Field

[0001] The present invention relates to a method for simultaneously preparing Cyperus esculentus starch sugar and Cyperus esculentus oil, belonging to the technical field of oil extraction and processing (or the technical field of comprehensive processing of oil crops). Background Art

[0002] Cyperus esculentus (Tiger nut, Cyperus esculentus) is native to Africa and Mediterranean coastal countries. It is a high-quality, high-yield oil crop with high comprehensive utilization value. It is rich in nutrients, especially high in starch and oil content. At the same time, protein and fiber can also be processed and utilized as by-products. As an important special oil crop that enriches the supply of vegetable oil, the cultivation of Cyperus esculentus has been vigorously promoted in China, and its planting area has been increasing year by year. At present, the general idea of comprehensive utilization of Cyperus esculentus is a technical route that first extracts oil by pressing method or solvent extraction method, and then extracts starch from the cake. This process can continuously complete the extraction of oil and starch. However, the pressing method and the solvent method have the disadvantages of low extraction rate and organic solvent residue respectively. At the same time, the crude oil obtained by the pressing method and the solvent extraction method is usually of poor quality and requires a comprehensive refining process, which has a certain damage to the quality of the oil.

[0003] The water-medium method for extracting vegetable oil is a technology that uses water as a medium, supplemented or not supplemented with technologies such as ethanol, food-grade enzymes or physical fields to destroy the cell wall or other components of oil crops so as to release vegetable oil. The prior art CN102234335B, a production process for continuously extracting Cyperus esculentus starch, oil and sugar, discloses the use of the aqueous enzymatic method to extract oil, simultaneously separate protein and oil, and prepare syrup from starch. This technology has the problems of complex preparation process and low yields of oil (70%) and sugar (65%). The prior art CN107099375B, a method for preparing Cyperus esculentus oil and Cyperus esculentus powder, discloses a method of first crushing Cyperus esculentus, then adding water for grinding, enzymatically hydrolyzing with alkaline protease, alkaline pectinase and alkaline cellulase, and then separating to obtain crude Cyperus esculentus oil. This technology does not involve the liquefaction and saccharification of Cyperus esculentus starch, and the crude Cyperus esculentus oil prepared is a by-product with a low yield. At the same time, this technology also has the following problems: (1) Under the process conditions of adding water for slurry grinding, the original reducing sugar in Cyperus esculentus powder dissolves, and at a certain temperature, it is very likely to undergo the Maillard reaction with the protein after enzymatic hydrolysis, and its products may ultimately affect the color, purity and flavor of the product; (2) This patent adds many types of enzymes and a large amount of enzymes, with the disadvantage of high production cost; (3) The interior of the starch molecule is a hydrophobic helical structure, which will encapsulate part of the oil. Reacting without destroying the starch molecule will limit the extraction rate of the oil.

[0004] Therefore, it is necessary to develop a simple and high-yield preparation process for Cyperus esculentus oil and Cyperus esculentus starch saccharification. Summary of the Invention

[0005] The present invention adopts a dry grinding process to minimize the average particle size of tiger nut powder, and then uses water washing to dissolve the non-starch polysaccharides in the bean powder. After discarding the aqueous phase, the starch with higher purity in the residue phase is liquefied and saccharified to produce glucose syrup. The oil on the upper layer is collected during the process to complete the extraction of tiger nut oil.

[0006] The first object of the present invention is to provide a method for simultaneously preparing tiger nut starch sugar and tiger nut oil, including the steps of:

[0007] (1) Dry grinding: Dry grind tiger nuts to obtain tiger nut powder with an average particle size of 20 - 80 μm;

[0008] (2) Water washing: Add an appropriate amount of water to the tiger nut powder obtained by grinding in step (1), stir at a certain temperature for a certain time, and then centrifuge to obtain a residue phase, an aqueous phase, an oil phase, and an emulsion. Demulsify the emulsion to obtain clear oil, and combine the clear oil and the oil phase to obtain the first tiger nut oil;

[0009] (3) Liquefaction: Collect the residue phase in step (2), add water to the residue phase and mix evenly, add thermostable α-amylase, and perform jet liquefaction or holding liquefaction;

[0010] (4) Saccharification: Cool the solution after liquefaction in step (3) to a temperature suitable for enzyme reaction, add pullulanase and glucoamylase, and stir for saccharification;

[0011] (5) Separation: Centrifuge the solution after saccharification in step (4) again to obtain the second tiger nut oil, an aqueous phase, and a residue phase. Combine the second tiger nut oil with the first tiger nut oil in step (2) to obtain the total tiger nut oil;

[0012] (6) Purification: Purify the aqueous phase in step (5). The purification steps are as follows: Add a certain amount of diatomaceous earth and activated carbon to the aqueous phase, stir at an appropriate temperature for a certain time, and then centrifuge or filter to remove proteins and pigments to obtain tiger nut starch syrup.

[0013] The existing crushing methods for tiger nuts mainly use wet grinding. The particles obtained by this method are relatively large, and at the same time, wet grinding will cause emulsification of oil, water, and protein, which is not conducive to the extraction of oil. In the present invention, dry grinding is used to avoid excessive emulsification and obtain particles with an average particle size of 20 - 80 μm, which is further conducive to the release of intracellular contents.

[0014] In one embodiment, the ratio of tiger nut powder to water in step (2) is 1:(2 - 10).

[0015] In one embodiment, the temperature in step (2) is 15 - 25 °C.

[0016] In one embodiment, the stirring time in step (2) is 20 to 40 min.

[0017] In one embodiment, the addition amount of thermotolerant α-amylase in step (3) is 20 to 60 U / g of substrate.

[0018] In one embodiment, the temperature of jet liquefaction or holding liquefaction in step (3) is 95 to 100 °C, and the pH is 6.0 to 7.0.

[0019] In one embodiment, the addition amount of pullulanase in step (4) is 0 to 40 U / g of substrate; the addition amount of glucoamylase is 100 to 300 U / g of substrate.

[0020] In one embodiment, the temperature in step (4) is 50 to 60 °C, and the pH is 5.0 to 6.0.

[0021] In one embodiment, the addition amount of diatomite in step (6) is 0.1 to 0.3% w / v.

[0022] In one embodiment, the addition amount of activated carbon in step (6) is 0.1 to 0.3% w / v.

[0023] In one embodiment, in step (6), it is stirred at 50 to 90 °C for 10 to 60 min.

[0024] In one embodiment, the demulsification method is as follows: Take the upper layer of the emulsion and place it in a -20 °C refrigerator for freezing for about 12 h, then thaw it in a 50 °C water bath, and collect the upper layer of clear oil after centrifugation at 10000 rpm.

[0025] In one embodiment, the specific steps are as follows:

[0026] (1) Dry pulverization: The sun-dried and dehulled Cyperus esculentus tubers are fully pulverized, and the pulverization is carried out 8 to 12 times to obtain Cyperus esculentus tuber powder with an average particle size of 10 to 80 μm as the extraction raw material;

[0027] (2) Water washing: Take 100 to 200 g of the Cyperus esculentus tuber powder obtained by pulverization in step (1), add water at a solid-liquid ratio of 1:(3 to 6), and stir well for 30 to 60 min under the conditions of room temperature (15 to 25 °C) and natural pH (without additional interference with pH), centrifuge to obtain the residue phase, water phase, oil phase and emulsion, demulsify the emulsion to obtain clear oil, and combine it with the oil phase and clear oil to obtain the first Cyperus esculentus oil;

[0028] (3) Liquefaction: Collect the slag phase in step (2), add 500 - 1000 mL of water to the slag phase and mix well. Add thermotolerant α - amylase (enzyme dosage 30 - 60 u / g of starch slag phase), raise the temperature to 95 - 100 °C, and stir vigorously for 30 - 60 min or more under the condition of pH 5.0 - 6.5 to fully liquefy the starch. After the liquefaction is completed, detect that the DE value of the aqueous phase reaches about 20%;

[0029] (4) Saccharification: Cool the enzymatic hydrolysis system to 50 - 60 °C, adjust the pH to 5.0 - 6.0, and at the same time add pullulanase (enzyme dosage 10 - 30 U / g of slag phase) and glucoamylase (enzyme dosage 100 - 250 u / g of slag phase), and stir vigorously for 2 - 4 h to fully saccharify the liquefied liquid. After the saccharification is completed, the DE value of the aqueous phase reaches more than 93%;

[0030] (5) Purification: Centrifuge the solution after saccharification in step (4) again to obtain the second Cyperus esculentus oil, aqueous phase and slag phase. Combine the second Cyperus esculentus oil with the first Cyperus esculentus oil in step (2) to obtain the total Cyperus esculentus oil; Collect the aqueous phase for purification. The purification steps are as follows: Add 0.1 - 0.3% w / diatomaceous earth and 0.1 - 0.3% w / activated carbon to the aqueous phase, stir at 50 - 90 °C for 10 - 60 min, then centrifuge or filter to remove proteins and pigments to obtain Cyperus esculentus starch syrup.

[0031] In one embodiment, the specific steps are as follows:

[0032] (1) Dry pulverization: Sufficiently pulverize the sun - dried and shelled Cyperus esculentus, with the pulverization times being 8 - 10 times, to obtain Cyperus esculentus powder with an average particle size of 20 - 60 μm as the extraction raw material;

[0033] (2) Water washing: Take 100 - 150 g of the Cyperus esculentus powder obtained by pulverization in step (1), add water at a solid - liquid ratio of 1:(4 - 5), stir vigorously for 30 - 50 min under the conditions of room temperature (15 - 25 °C) and natural pH (without additional interference with pH), centrifuge to obtain the slag phase, aqueous phase, oil phase and emulsion. Demulsify the emulsion to obtain clear oil, and combine it with the oil phase and clear oil to obtain the first Cyperus esculentus oil;

[0034] (3) Liquefaction: Collect the slag phase in step (2), add 500 - 800 mL of water to the slag phase and mix well. Add thermotolerant α - amylase (enzyme dosage 40 - 50 u / g of starch slag phase), raise the temperature to 95 - 100 °C, and stir vigorously for 30 - 60 min or more under the condition of pH 6.0 - 6.5 to fully liquefy the starch;

[0035] (4) Saccharification: Cool the enzymatic hydrolysis system to 50 - 55 °C, adjust the pH to 5.0 - 5.5, and simultaneously add pullulanase (enzyme dosage: 10 - 20 U / g of residue phase) and glucoamylase (enzyme dosage: 100 - 200 u / g of residue phase), and stir thoroughly for 2 - 4 h to fully saccharify the liquefied liquid. After the saccharification ends, the DE value of the aqueous phase reaches over 93%.

[0036] (5) Purification: Centrifuge the solution after saccharification in step (4) again to obtain the second Cyperus esculentus oil, aqueous phase, and residue phase. Combine the second Cyperus esculentus oil with the first Cyperus esculentus oil in step (2) to obtain the total Cyperus esculentus oil; collect the aqueous phase for purification. The purification steps are as follows: Add 0.2 - 0.3% w / w diatomaceous earth and 0.1 - 0.3% w / w activated carbon to the aqueous phase, stir at 50 - 90 °C for 10 - 60 min, then centrifuge or filter to remove proteins and pigments, and obtain Cyperus esculentus starch syrup.

[0037] Beneficial effects

[0038] The present invention uses Cyperus esculentus as the raw material and simultaneously prepares starch sugar (taking glucose as an example) and Cyperus esculentus oil through five steps: dry pulverization, water washing, liquefaction, saccharification, and purification.

[0039] Compared with the existing wet grinding method of Cyperus esculentus, the obtained particles are larger, and wet grinding will cause emulsification of oil, water, and protein, which is not conducive to the extraction of oil. The dry pulverization used in the present invention can avoid excessive emulsification and is conducive to the release of cell contents.

[0040] The preparation method of the present invention is simple and has a high preparation yield. The extraction rate of Cyperus esculentus oil reaches 89.40%, the yield of glucose syrup is 90.10%, and the purity is 89.41%. Description of the drawings

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0042] Figure 1 : Influence of α - amylase dosage on hydrolysis degree;

[0043] Figure 2 : Influence of glucoamylase dosage on hydrolysis degree;

[0044] Figure 3 : Influence of temperature on water washing effect;

[0045] Figure 4 : Change of residue phase components. Specific embodiments

[0046] Yield calculation formula

[0047] Oil extraction rate = mass of refined oil / total fat content in tiger nut powder × 100%;

[0048] Glucose syrup yield = (mass of purified glucose syrup × 0.9) / total starch mass in tiger nut powder × 100% (where 0.9 is the conversion coefficient for glucose to starch, and the denominator is the starch contained in the raw material);

[0049] Glucose syrup purity = mass of glucose in glucose syrup / mass of glucose syrup × 100%.

[0050] Demulsification step:

[0051] Take the upper layer of the emulsion and place it in a -20°C refrigerator for about 12 h, then thaw it in a 50°C water bath, and collect the upper layer of refined oil after centrifugation at 10000 rpm.

[0052] Example 1: Preparation of tiger nut starch sugar and tiger nut oil

[0053] Simultaneously prepare tiger nut starch sugar and tiger nut oil by the double-enzyme method. The specific steps are as follows:

[0054] (1) Dry pulverization: Sufficiently pulverize the sun-dried and shelled tiger nuts 10 times to obtain tiger nut powder with an average particle size of 20 - 40 μm as the extraction raw material.

[0055] (2) Water washing: Take 100 g of the tiger nut powder obtained by pulverization in step (1), add water at a solid-liquid ratio of 1:5, and stir well for 30 min at room temperature (15 - 25°C) and natural pH (without additional interference with pH). Centrifuge to obtain the residue phase, aqueous phase, oil phase, and emulsion, and collect the emulsion for freeze demulsification (provide the source of the literature or patent) to obtain refined oil.

[0056] (3) Liquefaction: Collect the residue phase in step (2), add 500 mL of water and mix well, add thermostable α-amylase (enzyme addition amount: 40 u / g starch), raise the temperature to 95 - 100°C, and stir well for more than 30 min at pH = 6.5 to fully liquefy the starch. After the liquefaction is completed, detect that the DE value of the aqueous phase reaches about 20%.

[0057] (4) Saccharification: Cool the enzymatic hydrolysis system to 55°C, adjust the pH to 5.5, and simultaneously add pullulanase (enzyme addition amount: 10 U / g starch) and glucoamylase (enzyme addition amount: 200 u / g starch), and stir well for 2 h to fully saccharify the liquefied liquid. After the saccharification is completed, the DE value of the aqueous phase reaches more than 93%.

[0058] (5) Purification: Centrifuge the saccharified solution again to obtain an oil phase, an aqueous phase, and a residue phase. Combine this oil phase with the oil phase obtained in step (2) to obtain Cyperus esculentus oil. Collect the aqueous phase for purification. The purification steps are as follows: suction filtration → add 0.2% (w / v) diatomaceous earth and 0.1% (w / v) activated carbon, stir at 60 °C for 30 min → suction filtration → remove protein by Sevag method (stir for 25 min) → remove the lower layer with a separating funnel → centrifuge the upper solution at 8000 rpm for 10 min, pour it onto a plate and dry it, and collect the dried sample to measure the yield and purity.

[0059] In steps (2) to (4), the residual conditions of each component in the residue phase were detected respectively, and the results are as Figure 4 shown. It can be seen that pullulanase can debranch amylopectin and convert it into amylose, which is beneficial to the action of glucoamylase and accelerates the hydrolysis of starch into glucose. At the same time, the hydrolysis of starch can reduce the residual fat in the residue phase and improve the extraction rate of oil. Finally, the extraction rate of Cyperus esculentus oil was calculated to be 89.40%, the yield of glucose syrup was 90.10%, and the purity was 89.41%.

[0060] Example 2: Optimization of the addition amount of α-amylase

[0061] Change the addition amount of α-amylase in step (3) to 20 U / g starch, 40 U / g starch, and 60 U / g starch, and the other conditions are the same as those in Example 1. Detect the degree of hydrolysis of starch. The results are as Figure 1 shown. When the addition amount of α-amylase is 60 U / g, the degree of hydrolysis reaches more than 25% in 30 min. When the addition amount is 40 U / g starch, the degree of hydrolysis reaches more than 20% in 30 min.

[0062] During the saccharification process, glucoamylase needs to form a complex structure with the substrate molecules and then undergo hydrolysis catalysis. This requires the size of the substrate molecules to be within a certain range, which is beneficial to the formation of this complex structure. It is not suitable if it is too large or too small. According to the production practice of starch sugar, it is more appropriate that the DE value after liquefaction reaches the range of 15% - 25%. Hydrolysis beyond this degree is not conducive to the formation of a complex structure by glucoamylase, affecting the catalytic efficiency and thus the final DE value.

[0063] Therefore, select the lowest enzyme addition amount of 40 u / g within this range, which can not only control the cost but also reach the appropriate DE value range.

[0064] Example 3: Optimization of the addition amount of glucoamylase

[0065] Change the addition amount of glucoamylase in step (4) to 0 U / g starch, 100 U / g starch, 200 U / g starch, and 300 U / g starch, and the other conditions are the same as those in Example 1. Detect the degree of hydrolysis of starch. The results are as Figure 2As shown, when the addition amount of glucoamylase is 200 U / g starch, the hydrolysis degree reaches over 93% in 3 hours, and there is little difference from the hydrolysis degree when the addition amount of glucoamylase is 300 U / g starch. Therefore, 200 U / g starch is selected as the optimal addition amount of glucoamylase.

[0066] Example 4: Optimization of the particle size of crushed Cyperus esculentus

[0067] Change the particle size of the crushed Cyperus esculentus in step (1) to 80 μm, 100 μm, and 120 μm respectively, and keep the other conditions the same as in Example 1, then detect the oil extraction rate, the yield of glucose syrup, and the purity of glucose syrup.

[0068] The results are shown in Table 1. It is detected that when the particle size is 80 μm, the oil extraction rate of Cyperus esculentus oil is 86.32%, the yield of glucose syrup is 89.66%, and the purity is 88.40%. When the particle size is 100 μm, the oil extraction rate of Cyperus esculentus oil is 84.57%, the yield of glucose syrup is 87.28%, and the purity is 87.12%. When the particle size is 120 μm, the oil extraction rate of Cyperus esculentus oil is 80.36%, the yield of glucose syrup is 85.57%, and the purity is 86.48%.

[0069] Table 1 Influence of different particle sizes on the yield

[0070]

[0071] Example 5: Optimization of the water washing temperature

[0072] Change the temperature in step (2) to 30 °C, 40 °C, 50 °C, and 60 °C, and keep the other conditions the same as in Example 1, then detect the dissolution rate and yield of non-starch polysaccharides.

[0073] It is detected that when the temperature is 30 °C, the oil extraction rate of Cyperus esculentus oil is 88.25%, the yield of glucose syrup is 88.66%, and the purity is 89.35%; when the temperature is 40 °C, the oil extraction rate of Cyperus esculentus oil is 88.72%, the yield of glucose syrup is 88.28%, and the purity is 89.12%; when the temperature is 50 °C, the oil extraction rate of Cyperus esculentus oil is 89.80%, the yield of glucose syrup is 88.57%, and the purity is 89.48%; when the temperature is 60 °C, the oil extraction rate of Cyperus esculentus oil is 90.48%, the yield of glucose syrup is 88.69%, and the purity is 89.76%. It can be seen that the temperature has little influence on the yield and purity.

[0074] Table 2 Influence of water at different temperatures on the yield

[0075]

[0076] The results of the dissolution rate of non-starch polysaccharides are as Figure 3As shown, in the range of 30 to 60 °C, the higher the temperature, the less significant the impact of temperature on the dissolution rate. Moreover, since excessive temperature can cause starch gelatinization, resulting in a sharp increase in viscosity and being unfavorable for operation, the water washing temperature should not exceed 60 °C. From the perspective of cost, this patent selects water washing at room temperature.

[0077] Comparative Example 1: Influence of not performing water washing on the preparation of Cyperus esculentus starch sugar and Cyperus esculentus oil

[0078] Based on Example 1, step (2) was omitted, and the DE values after liquefaction and saccharification were detected, and the oil extraction rate, glucose syrup yield, and glucose syrup purity were calculated. The results are shown in the following table.

[0079] The results show that not performing water washing will affect starch hydrolysis and saccharification, resulting in a decrease in the degree of hydrolysis; at the same time, the oil extraction rate, glucose syrup yield, and glucose syrup purity decrease.

[0080] Table 3 Influence of not performing water washing on the yield

[0081]

[0082] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or modifications made without departing from the technical spirit of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for synchronously preparing tiger nut starch sugar and tiger nut oil, characterized in that, Including the steps: (1) Dry grinding: Dry grind tiger nuts to obtain tiger nut powder with an average particle size of 20 - 40 μm. (2) Water washing: Add water to the tiger nut powder obtained by grinding in step (1) according to a solid - liquid ratio of 1:2 - 10, stir at 15 - 60 °C for 10 - 60 min and then centrifuge to obtain a residue phase, an aqueous phase, an oil phase and an emulsion. Demulsify the emulsion to obtain clear oil, and combine the clear oil and the oil phase to obtain the first tiger nut oil. (3) Liquefaction: Collect the residue phase in step (2), add water and mix evenly, add heat - resistant α - amylase at 20 - 60 U / g of substrate, and perform jet liquefaction or holding liquefaction. (4) Saccharification: Cool the solution after liquefaction in step (3) to a temperature suitable for enzymatic reaction, add pullulanase at 10 U / g of substrate and glucoamylase at 100 - 300 U / g of substrate, and stir for saccharification. (5) Separation: Centrifuge the solution after saccharification in step (4) again to obtain the second tiger nut oil, an aqueous phase and a residue phase. Combine the second tiger nut oil with the first tiger nut oil in step (2) to obtain the total tiger nut oil. (6) Purification: Purify the aqueous phase in step (5). The purification steps are as follows: Add diatomaceous earth and activated carbon to the aqueous phase, stir at an appropriate temperature, and then centrifuge or filter to remove proteins and pigments to obtain tiger nut starch syrup.

2. The method according to claim 1, wherein In step (3), the temperature is 90 - 150 °C and the pH is 5.0 - 8.

0.

3. The method according to claim 1, wherein In step (4), the temperature is 40 - 70 °C and the pH is 5.0 - 6.

0.

4. The method according to claim 1, wherein In the purification step of step (6), the addition amount of diatomaceous earth is 0.1 - 2% w / w.

5. The method according to claim 1, wherein In the purification step of step (6), the addition amount of activated carbon is 0.1 - 10% w / w.

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