JP2010116524A - Extraction method for polysaccharide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple hot-water extraction method for polysaccharides, especially pectin, from citrus rinds, enabling polymer-rich pectin with slight impurities to be obtained in high recovery without conducting any treatment with e.g. an acid, alkali, chelating agent or emulsifier. <P>SOLUTION: Polymer-rich pectin with very slight in impurities including protein is obtained in high recovery by conducting only a subcritical water extraction treatment of citrus peels under predetermined conditions of 120-140°C and 4-30 MPa without conducting any treatment with e.g. an acid, alkali, chelating agent or emulsifier. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for extracting polysaccharides, particularly pectin, from plant cell tissues, particularly citrus peel. More specifically, the present invention relates to a hot water extraction method for pectin from citrus peel using subcritical water extraction conditions as extraction conditions.

  In recent years, biomass (biological resources) has attracted attention from the viewpoint of breaking away from the high degree of dependence on limited fossil resources. Biomass refers to organic resources derived from renewable organisms excluding fossil resources.

  Biomass is used as waste in the municipal food waste and livestock industry, as well as waste in the food industry, unused resources such as rice husk and fruit juice extraction residue, and resource crops such as bioethanol raw materials. being classified. In particular, there is a strong demand for the development of an effective utilization method for waste and unused biomass in order to construct a system (biomass refinery) that uses all biomass as material and energy.

  Many waste-based and unused resource-based biomass contain useful polysaccharides such as cellulose, hemicellulose, and pectin derived from plant cell tissues (cell walls, etc.). Of these, pectin has been considered to be a component that is difficult to extract with hot water as it is because it is insoluble in plant cell tissues.

  As this pectin extraction method, for example, a method of extracting / separating from citrus peel (mainly lemon), apple juice lees, beet pulp, corn starch, aloe etc. using acid, alkali, chelating agent, etc. has been developed. However, these methods require repeated operations such as neutralization and removal of acids, alkalis, chelating agents, etc., making the recovery operation complicated. In addition, depending on the additive, pectin molecules may be decomposed to lower the molecular weight of pectin, which may affect the gelation ability of the obtained pectin.

In particular, citrus peel is considered to be highly useful as a pectin raw material because it is an unused resource that is discharged in large quantities during fruit processing and juice extraction and contains a large amount of pectin. However, the above-described pectin extraction method by treatment with acid, alkali, chelating agent, etc. does not satisfy the production cost or the quality of the obtained pectin. It has been desired to develop a method for easily obtaining a molecular pectin at a high recovery rate by hot water extraction.
JP 2000-7703 A JP 2002-514663 A JP 2004-197001 A

  An object of the present invention is to provide a pectin that can obtain a high-recovery pectin containing a large amount of impurities-free polymer from citrus peel without performing an additive treatment such as acid, alkali, chelating agent, or emulsifier. Is to provide a simple hot water extraction method. It is another object of the present invention to provide a method capable of confirming the pectin elution status at the same time as the extraction of pectin.

  In order to achieve the above object, the present inventors have paid attention to subcritical water extraction as a result of intensive studies. And, by performing only pressurized hot water extraction (subcritical water extraction treatment) under predetermined subcritical water extraction conditions in the range of 120 to 140 ° C. and 4 to 30 MPa for citrus peel, acid, alkali, chelating agent, Or, without any processing of additives such as emulsifiers, a pectin extract containing a large amount of high molecular weight pectin with very little mixture of proteins and contaminants can be obtained, and pectin can be recovered at a high recovery rate of 70% or more. Has been found to be recoverable, leading to the present invention. In addition, it was also found that elution of pectin can be confirmed simultaneously with extraction by immediately measuring the pH of the subcritical water extraction solution.

That is, the embodiment of the present invention is as follows.
(1) It is characterized by extracting from citrus peel using only subcritical water extraction treatment under conditions of 120 to 140 ° C. and 4 MPa without performing any treatment with acid, alkali, chelating agent, or emulsifier. A method for extracting pectin containing a large amount of high molecular weight pectin.
(2) Subcritical water extraction from citrus peel without any treatment with acid, alkali, chelating agent, or emulsifier under conditions of 130-140 ° C., 4-30 MPa, preferably 140 ° C., 4-10 MPa A method for extracting pectin containing a large amount of high molecular weight pectin, characterized by performing extraction only by treatment.
(3) The method according to (1) or (2), wherein the molecular weight of the high molecular weight pectin is 40 to 400,000, more preferably 5 to 300,000.
(4) The method according to any one of (1) to (3), wherein the total pectin recovery rate is 70% or more, and further 75 to 80%.
(5) The method according to any one of (1) to (4), wherein the extraction flow rate of subcritical water is 0.5 to 2.0 ml / min.
(6) A method of confirming elution of pectin simultaneously with extraction by immediately measuring the pH of the extract when extracting pectin from citrus peel using subcritical water extraction treatment.

  According to the present invention, high molecular weight pectin having a molecular weight of 40,000 to 400,000, which contains very little mixture of proteins and contaminants from citrus peel without any processing of additives such as acid, alkali, chelating agent or emulsifier. Can be obtained with a high recovery rate. Furthermore, by immediately measuring the pH of the extract obtained by subcritical water extraction, elution of pectin can be confirmed simultaneously with extraction.

  In the present invention, citrus peel that is discharged in large quantities during fruit processing or juice extraction is used as a pectin extraction raw material. Citrus fruit skin is exemplified by the origin of yuzu, lemon, mandarin orange, orange, kabosu, sudachi, daidai, seaquaser, lime, grapefruit, kumquat, and the like. In particular, yuzu fruit is very suitable as a raw material because yuzu fruit has a large percentage of pericarp (50% or more of yuzu fruit) and a large amount of waste compared to other citrus fruits. In addition to raw citrus peel, it is also possible to use not only raw citrus peel, but also dried residue of citrus peel, an extraction residue obtained by extracting essential oil or the like by supercritical extraction from pulverized product or citrus peel.

  Subcritical water extraction conditions are used for pectin extraction. Subcritical water refers to pressurized hot water of 100 ° C. or higher with a pressure of saturated water vapor pressure or higher. However, supercritical water (pressurized hot water of 374 ° C. or higher, 22 MPa or higher) is not included. In the method, citrus peel is placed in a reaction vessel, and deaerated water preheated at a predetermined flow rate is passed therethrough. Then, the reaction system is heated under pressure under predetermined conditions to obtain subcritical water extraction conditions. The extract after passing through subcritical water is quickly cooled and recovered. A schematic diagram of an extraction apparatus used in the present invention is shown in FIG.

  As the subcritical water extraction conditions, a pressure of 4 MPa is preferable when the temperature is 120 to 140 ° C, and a pressure of 4 to 30 MPa (further, the temperature is 140 ° C and the pressure is 4 to 10 MPa) when the temperature is 130 to 140 ° C. If the temperature exceeds 140 ° C., the total pectin recovery rate will be high, but the pectin quality will be unfavorable due to low molecular weight of pectin, large amounts of impurities such as impurities and proteins. Also, at temperatures below 120 ° C., pectin extraction cannot be obtained with a sufficient recovery rate. In the temperature range of 120 to 140 ° C., the higher the pressure, the lower the total pectin recovery rate in inverse proportion. Therefore, considering the efficiency and cost, the pressure is preferably around 4 to 10 MPa.

  In the conventional pectin extraction method, in order to facilitate elution from plant cell tissue, a method of adjusting the pH of the extraction raw material by acid or alkali treatment or adding a chelating agent during extraction is adopted. However, in the present invention, these treatments and additions are not necessary at all. In addition, a method of adding an emulsifier at the time of extraction is also known in order to prevent contamination with contaminants and proteins in the extract, but in the present invention, impurities are extremely mixed by subcritical water extraction under predetermined conditions. Therefore, it is not necessary to add an emulsifier at all.

  The flow rate during subcritical water extraction is not particularly limited, but is preferably 0.5 to 2.0 ml / min. By setting the flow rate within this range, an extract containing a large amount of high molecular weight pectin can be obtained at a high concentration, and the amount of subcritical water used for extraction can be reduced. Therefore, it is very effective in practical use. Even if the flow rate is increased from this range, the quality of pectin obtained, the recovery rate, etc. are not affected at all.

  The high molecular weight pectin obtained by the present invention is a pectin having a molecular weight of 40,000 to 400,000, and further a molecular weight of 5 to 300,000. Pectin is mainly used as a thickener in the food industry, and its viscosity correlates with pectin molecular weight. In other words, the molecular weight of pectin greatly affects the quality as a thickener. The present invention is a very useful method because a large amount of high molecular weight pectin can be extracted from citrus peel.

  In addition, the total pectin (high molecular weight pectin, low molecular weight pectin having a molecular weight of 40,000 or less, and total pectin containing a caracturonic acid monomer) recovery from the citrus peel according to the present invention is 70% or more, and further 75 to 80%, Very high recovery rate. The recovery rate decreases as the pressure is increased in the temperature range of 120 to 140 ° C. of the present invention, and the recovery rate is 4 to 30 MPa at 130 to 140 ° C., which exceeds 70%. However, the recovery rate is only 4 MPa at 120 ° C. The rate does not exceed 70%. When the recovery rate is 75% as an index, the recovery rate exceeds 4% at 4 to 30 MPa at 140 ° C., but the recovery rate exceeds 75% only at 4 MPa at 120 to 130 ° C.

  Furthermore, in the present invention, the elution of pectin can be confirmed simultaneously with the extraction by immediately measuring the pH of the extract at the time of subcritical water extraction. As the amount of elution of pectin increases, the pH of the extract moves more acidic (pH decreases), and when the amount of elution decreases, the pH of the extract returns to the original value. By acquiring this pH behavior data immediately, it is possible to confirm the elution status at the same time as the extraction of pectin, so that a pectin solution with fewer impurities can be acquired.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. In all the following examples, the reaction was carried out by the apparatus shown in FIG.

(Example 1: Confirmation of influence of subcritical water temperature on pectin elution)
As a pectin extraction raw material, 0.5 g of dried yuzu peel powder (particle size: 120 to 400 μm) was used. As extraction conditions, put the skin powder into a reaction vessel, and water sufficiently deaerated distilled water through the reactor at a flow rate of 3.5 ml / min, and after confirming that bubbles disappeared from the recovery port, After the pressure inside the container was increased to 4 MPa with a back pressure valve, the liquid passing temperature was gradually raised to 80 to 160 ° C., and 7 ml of the extract was recovered at each temperature zone. Pectin quantification of the obtained extract was performed by quantifying galacturonic acid monomers by the dimethylphenol-sulfuric acid method.

  As shown in FIG. 2, pectin elution was gradually confirmed from 100 ° C., and it was revealed that pectin elution was performed up to around 160 ° C. It was also shown that there was pectin elution most rapidly around 120-140 ° C.

(Example 2: Confirmation of effect of subcritical water temperature on pectin molecular weight and elution of components other than pectin)
The conditions other than the temperature and flow rate were the same as in Example 1, and the temperature was rapidly increased from 80 ° C. to 120 ° C., 140 ° C., and 160 ° C. at a flow rate of 0.5 ml / min. The condition (appearance, smell, etc.) of the pectin extract was confirmed, and the total pectin amount, pectin molecular weight, and protein amount were measured. Protein quantification was performed by the Kjeldahl method. Pectin molecular weight was measured by high performance liquid chromatography.

  As shown in FIG. 3, the pectin solution extracted at 120 ° C. and 140 ° C. has no turbidity or the like, and does not have the fragrance of the furan compound peculiar to the saccharide hyperdegradation product. In contrast, the pectin solution extracted at 160 ° C. was markedly cloudy, colored, and smelly. Furthermore, as shown in FIG. 4, although many proteins were mixed in the pectin solution extracted at 160 ° C., the amount of protein in the pectin solution extracted at 120 ° C. and 140 ° C. was very small. Therefore, it was revealed that pectin extracted at 120 ° C. and 140 ° C. is suitable with very few impurities.

  Moreover, as shown in FIG. 5, most of the pectin extracted at 160 ° C. has a molecular weight of 1 to 20,000 or less, and the molecular weight is clearly decreasing. Pectin exhibits gelling properties due to its higher-order structure, but those recovered at 160 ° C. are very low in molecular weight and have the properties of pectin (thickener) as a food additive. Not done. On the other hand, most of those extracted at 120 ° C. and 140 ° C. account for a pectin molecular weight of 40,000 to 400,000. That is, it can be extracted without losing the usefulness of pectin as a thickener. In addition, it is shown that pectin with various molecular weights can be collected depending on the application by setting the temperature.

(Example 3: Confirmation of influence of subcritical water temperature and pressure on total pectin recovery rate)
As a pectin extraction raw material, 0.5 g of dried yuzu peel powder was used as in Example 1. As extraction conditions, put the skin powder into the reaction vessel, and water distilled sufficiently deaerated through the reactor at a flow rate of 0.5 ml / min, and after confirming that bubbles disappeared from the recovery port, After increasing the pressure inside the container with a back pressure valve to a predetermined pressure (4, 10, 20, 30 MPa), the liquid passing temperature is rapidly increased from 80 ° C. to a predetermined temperature (110, 120, 130, 140, 150, 160 ° C.). The temperature was raised, and 7 ml of the obtained pectin extract was collected, and the quantification and recovery rate of pectin were measured.

  FIG. 6 shows the pectin elution amount (upper stage) and the integrated yield (lower stage) when the temperature is raised to each temperature under a pressure condition of 4 MPa. From the upper graph, it was found that pectin elution was promoted more rapidly as the temperature was raised to a higher temperature. However, from the lower graph, it can be seen that the recovery rate is clearly reduced at 160 ° C., and overdecomposition (decomposition of galacturonic acid) proceeds. It can also be seen that pectin release does not proceed sufficiently at 110 ° C. On the other hand, when extracted at 120 to 40 ° C., the recovery rate converged to about 76%, indicating that the extraction was performed without undergoing excessive decomposition.

  FIG. 7 shows the effect of pressure on the total pectin recovery rate when extracted in a temperature range of 120 to 150 ° C. In the temperature range of 120 to 140 ° C., the recovery rate increases as the pressure decreases. On the contrary, at 150 ° C., the recovery rate tended to increase as the pressure increased. Further, the recovery rate was highest at 140 ° C., and it was shown that the recovery was performed in a high yield of 76 to 80% in a pressure zone of 4 to 30 MPa. Furthermore, even at 130 ° C., a high recovery rate of 70% or more was shown in the pressure range of 4 to 30 MPa.

  As the impact of pressure on costs such as capital investment, the higher the pressure, the higher the output of the pump, the tube thickness for safety, and the accompanying heat exchange. In the present invention, it has been shown that pectin can be extracted even at a relatively low pressure, and that it is possible to reduce capital investment and running cost. In addition, the temperature zone and pressure zone which can extract total pectin with the recovery rate of 75-80% were shown in FIG.

(Example 4: Confirmation of effect of subcritical water flow rate on pectin elution)
As a pectin extraction raw material, 0.5 g of dried yuzu peel powder was used as in Example 1. As extraction conditions, put the peel powder into a reaction vessel, and pass distilled water that has been sufficiently degassed into the reactor at a predetermined flow rate (0.5, 1.0, 2.0 ml / min) for recovery. After confirming that air bubbles disappeared from the mouth, the inside of the container was pressurized to 4 MPa with a back pressure valve, and the liquid passing temperature was rapidly raised from 80 ° C. to 140 ° C., and 7 ml of the extract was collected to quantify pectin. And recovery was measured.

  FIG. 9 shows the state of elution of pectin when water is passed at each flow rate. As the flow rate increased, the elution of pectin became smoother, and it was revealed that the concentration of the eluted pectin per fraction decreased. That is, it was shown that pectin recovery becomes possible at a higher concentration as the flow rate is lower.

  In FIG. 10, the pectin integrated yield by this method with respect to the pectin contained in the raw material is shown. It was shown that the yield was as high as about 76 to 77% at any flow rate, and it was revealed that the excessive decomposition of galacturonic acid at 140 ° C. did not occur at any flow rate.

  Usually, it is considered that the extraction efficiency (recovery rate) decreases if the flow rate of subcritical water is lowered. In fact, at 110 ° C. and 150 to 160 ° C., the flow rate and the recovery rate are correlated. However, at 120 to 140 ° C., it was shown that the recovery rate does not depend on the flow rate but on the residence time in the reaction tube. These indicate that it is possible to reduce the amount of subcritical water used for extraction in a relatively low temperature range, which is expected to reduce costs and improve the quality of the obtained pectin. is there.

(Example 5: Confirmation of relationship between pectin elution and extract pH)
As a pectin extraction raw material, 0.5 g of dried yuzu peel powder was used as in Example 1. As extraction conditions, put the peel powder into a reaction vessel, and pass distilled water that has been sufficiently degassed into the reactor at a predetermined flow rate (0.5, 1.0, 2.0 ml / min) for recovery. After confirming the absence of bubbles from the mouth, the pressure inside the container was increased to 4 MPa with a back pressure valve, and the liquid passing temperature was rapidly increased from 80 ° C. to a predetermined temperature (120, 140, 160 ° C.). The obtained pectin extract was collected in an amount of 7 ml, and the amount of pectin and the pH of the extract were measured.

  FIG. 11 shows the relationship between the pectin elution status at each flow rate (0.5, 1.0, 2.0 ml / min) when extracted at 140 ° C. and the pH transition of the extract (fraction). Yes. It was revealed that the pH decreased with elution of pectin at any flow rate.

  FIG. 12 shows the relationship between the pectin elution state and the pH transition of the extract (fraction) when extraction was performed at each temperature (120, 140, 160 ° C.) at a flow rate of 0.5 ml / min. As in FIG. 11, a decrease in pH accompanying pectin elution was confirmed. As described above, it was shown that the elution of pectin can be confirmed simultaneously with extraction by measuring the pH of the extract immediately.

The schematic of the extraction apparatus used for this invention is shown. The amount of pectin extracted when the temperature of 4 MPa subcritical water is raised is shown. The condition of the extract when pectin is extracted from yuzu peel at a pressure of 4 MPa and at temperatures of 120 ° C., 140 ° C., and 160 ° C. is shown (drawing substitute photo). The elution behavior of pectin and protein when pectin is extracted from yuzu peel at a pressure of 4 MPa and at temperatures of 120 ° C., 140 ° C., and 160 ° C. is shown. The molecular weight distribution of the pectin which extracted the pectin from the yuzu peel at each temperature of 120 degreeC, 140 degreeC, and 160 degreeC by the pressure of 4 Mpa is shown. The pectin elution situation (upper stage) at each temperature of 110 to 160 ° C. when pectin is extracted from yuzu peel at a pressure of 4 MPa, and the pectin integrated yield (lower stage) when extracted at each temperature are shown. The correlation between pectin extraction temperature, pressure and total pectin recovery is shown. A temperature zone and a pressure zone in which the total pectin recovery rate is 75 to 80% are shown. The pectin elution situation at each subcritical water flow rate (0.5, 1.0, 2.0 ml / min) when pectin is extracted from yuzu peel at a pressure of 4 MPa and 140 ° C. is shown. The pectin integrated yield at each subcritical flow rate (0.5, 1.0, 2.0 ml / min) when pectin is extracted from yuzu peel at a pressure of 4 MPa and 140 ° C. is shown. The pectin elution situation and pH transition at each subcritical water flow rate (0.5, 1.0, 2.0 ml / min) when pectin is extracted from yuzu peel at a pressure of 4 MPa and 140 ° C. are shown. The pectin elution situation and pH transition at each extraction temperature (120 ° C, 140 ° C, 160 ° C) when pectin is extracted from yuzu peel at a pressure of 4 MPa and a flow rate of 0.5 ml / min are shown.

Claims (6)

  Extraction method of pectin characterized by extracting from citrus peel using only subcritical water extraction treatment under conditions of 120 to 140 ° C. and 4 MPa.   Extraction method of pectin characterized by extracting from citrus peel using only subcritical water extraction treatment under conditions of 130 to 140 ° C. and 4 to 30 MPa.   The method according to claim 1 or 2, wherein the molecular weight of pectin is 40,000 to 400,000.   The method according to any one of claims 1 to 3, wherein the total pectin recovery rate is 70% or more.   The method according to any one of claims 1 to 4, wherein the subcritical water extraction flow rate is 0.5 to 2.0 ml / min.   When extracting pectin from citrus peel using subcritical water extraction, the pH of the extract is measured immediately to confirm elution of pectin simultaneously with extraction.

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