JP6990019B2 - Method for producing fatty acids - Google Patents

Description

The present invention relates to a method for producing fatty acids by an enzymatic decomposition method.

Fatty acids are widely used as intermediate raw materials for foods, additives for various other industrial products, and intermediate raw materials. Such fatty acids are generally produced by hydrolyzing vegetable oils such as rapeseed oil and soybean oil and animal oils such as beef tallow.
As a method for hydrolyzing fats and oils, there are a high-temperature high-pressure decomposition method and an enzymatic decomposition method. The former reacts under high temperature and high pressure conditions and has the advantage of high productivity. However, if a large amount of unsaturated fatty acids is used as a raw material fat, a large amount of trans-unsaturated fatty acids may be produced depending on the conditions. be. On the other hand, the latter uses an enzyme such as lipase as a catalyst and the reaction is carried out at a relatively low temperature, so that trans-unsaturated fatty acids are not produced, but the problem is that the productivity is lower than that of the high-temperature and high-pressure decomposition method. ..

In order to increase the productivity of fatty acids by the enzymatic decomposition method, for example, the equilibrium reaction is promoted toward the hydrolysis reaction of fats and oils by increasing the amount of water added into the reaction system or replacing the water. Is effective (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2009-268414

However, there is still room for improvement in the conventional enzymatic decomposition method from an industrial point of view.
Further, after hydrolysis, it is required that fatty acids can be easily obtained by facilitating the oil-water separation of the reaction solution, but it may be difficult to recover the fatty acids without oil-water separation in a short time. In general, the reaction solution after enzymatically hydrolyzing fats and oils contains unreacted fats and oils, partially hydrolyzed fats and oils, etc. in addition to fatty acids and glycerin. Monoglyceride was a cause of difficulty in oil-water separation of the reaction solution.
Therefore, an object of the present invention is to provide a method capable of improving the efficiency of the hydrolysis reaction and reducing the monoglyceride in the reaction solution in producing fatty acids from fats and oils by the enzymatic decomposition method.

The present inventor has conducted intensive research on the enzymatic decomposition method of fats and oils. First, the fats and oils are hydrolyzed until a predetermined free fatty acid concentration is reached, the water of the reaction system is replaced at such a specific time point, and then the fats and oils are replaced again. It was found that the hydrolysis reaction proceeds efficiently in a short time and the monoglyceride concentration in the reaction solution is lowered by hydrolyzing.

That is, the present invention describes the following steps (A) and (B):
(A) A step of hydrolyzing an oil or fat by an enzymatic decomposition method until the free fatty acid concentration reaches 50 to 84% by mass, and then separating the aqueous phase and the oil phase to obtain an oil phase.
(B) A method for producing fatty acids, which comprises a step of adding fresh water to the oil phase obtained in the step (A) and hydrolyzing the fat and oil again by an enzymatic decomposition method.

According to the present invention, the efficiency of the hydrolysis reaction of fats and oils can be improved, and the monoglyceride in the reaction solution can be reduced, so that fatty acids can be obtained with good productivity.

In the method for producing fatty acids of the present invention, (A) fats and oils are hydrolyzed by an enzymatic decomposition method until the free fatty acid concentration reaches 50 to 84% by mass, and then the aqueous phase and the oil phase are separated to obtain an oil phase. It has a step (B), a step of adding fresh water to the oil phase obtained in the step (A), and a step of hydrolyzing the fat and oil again by an enzymatic decomposition method.

[Step (A)]
This step is a step of hydrolyzing fats and oils by an enzymatic decomposition method until the free fatty acid concentration reaches 50 to 84% by mass, and then separating the aqueous phase and the oil phase to obtain an oil phase.
As used herein, the "enzymatic decomposition method" is a method for obtaining fatty acids and glycerin by adding water to fats and oils, using a fat and oil hydrolase as a catalyst, and reacting under low temperature conditions. Fatty acids may contain fats and oils in addition to fatty acids.
In the present specification, "fat and oil" is synonymous with "oil", and the substances constituting the fat and oil (oil) include not only triglyceride (TAG) but also monoglyceride (MAG) and diglyceride (DAG). That is, the fat (oil) contains any one or more of monoglyceride, diglyceride and triglyceride.

In the present invention, the fats and oils to be hydrolyzed may be either vegetable fats or oils or animal fats and oils. For example, soybean oil, rapeseed oil, safflower oil, rice oil, corn oil, sunflower oil, cottonseed oil, olive oil, sesame oil, peanut oil, honeybee oil, wheat germ oil, perilla oil, flaxseed oil, sesame oil, chia seed oil, sacha inch oil. , Walnut oil, kiwi seed oil, salvia seed oil, grape seed oil, macadamia nut oil, hazelnut oil, pumpkin seed oil, camellia oil, brown seed oil, borage oil, palm oil, palm olein, palm stea, palm oil, palm kernel Vegetable fats and oils such as oils, cacao fats, monkey fats, shea fats and algae oils; animal fats and oils such as fish oils, lard, beef fats and butter fats; or their ester exchange oils, hydrogenated oils or fractionated oils. Can be mentioned. These fats and oils may be used alone or in combination of two or more.

The fatty acids constituting the fats and oils to be hydrolyzed are not particularly limited and may be either saturated fatty acids or unsaturated fatty acids, but 60 to 100% by mass of the fatty acids constituting the fats and oils are unsaturated fatty acids. It is preferable, more preferably 70 to 99% by mass, further 75 to 97% by mass, and further preferably 80 to 95% by mass as unsaturated fatty acids in terms of appearance and industrial productivity of fats and oils. The unsaturated fatty acid has 14 to 24 carbon atoms, and more preferably 16 to 22 carbon atoms from the viewpoint of physiological effects. The amount of fatty acid in the present specification is a free fatty acid equivalent.

Further, among the fatty acids constituting the fats and oils to be hydrolyzed, the content of saturated fatty acids is preferably 30% by mass or less, more preferably 20% by mass or less, and further 15 in terms of suppressing crystal precipitation at low temperatures. It is more preferably 10% by mass or less, and more preferably 10% by mass or less. Further, in terms of the industrial productivity of fats and oils, it is preferably 0.5% by mass or more. As the saturated fatty acid, those having 14 to 24 carbon atoms and further 16 to 22 carbon atoms are preferable.

It is preferable that the fats and oils are extracted from the plants or animals that are the raw materials thereof, and then the solids other than the oils are removed by filtration, centrifugation or the like. Then, it is preferable to add and mix water and, in some cases, an acid, and then degumming by separating the gum component by centrifugation or the like. Further, it is preferable that the fats and oils are deoxidized by adding and mixing an alkali, washing with water and dehydrating. Further, it is preferable that the fats and oils are decolorized by contacting them with an adsorbent such as activated clay and then separating the adsorbent by filtration or the like. Further, deodorization is a process of removing unpleasant odors and taste substances to obtain refined oil having good flavor, hue and storage stability, and removes odorous components while blowing steam under high temperature and reduced pressure conditions. It is preferable to perform steam deodorization. These processes are preferably performed in the above order, but the order may be changed. In addition to this, the fat and oil may be wintered to separate the solid content at a low temperature in order to remove the wax content.

Lipase is preferable as the fat hydrolase. The lipase is not particularly limited, and a lipase derived from an animal, a plant, or a microorganism can be used. For example, the genus Rhizopus, the genus Aspergillus, the genus Mucor, the genus Rhizomucor, the genus Pseudomonas, the genus Geotrichum, the genus Geotrichum, the genus Penicilium. Examples include lipases of origin.
Among them, from the viewpoint of hydrolysis efficiency, it is preferable to use a so-called non-selective lipase having no position / chain length selectivity, and further, a non-selective lipase produced by Candida cylindracea is used. Is preferable.

As the oil / fat hydrolase, it is preferable to use an immobilized oil / fat hydrolase in which the enzyme is immobilized on a carrier, because the enzyme activity can be effectively utilized.
The immobilized carrier includes inorganic carriers such as Celite, diatomaceous earth, kaolinite, silica gel, molecular sieves, porous glass, activated carbon, calcium carbonate, and ceramics, ceramic powder, polyvinyl alcohol, polypropylene, chitosan, ion exchange resin, and hydrophobic adsorption. Examples thereof include organic polymers such as resins, chelate resins, and synthetic adsorption resins. Of these, an ion exchange resin is preferable because of its high water retention capacity. Further, among the ion exchange resins, the porous one is preferable from the viewpoint that the adsorption amount of the enzyme can be increased by having a large surface area.

The particle size of the resin used as the immobilized carrier is preferably 50 to 2000 μm, more preferably 100 to 1000 μm. The pore diameter is preferably 10 to 150 nm, more preferably 10 to 100 nm. Examples of the material include phenol formaldehyde, polystyrene, acrylamide, divinylbenzene and the like, and a phenol formaldehyde resin (for example, Duolite A-568 manufactured by Rohman and Haas) is preferable from the viewpoint of improving enzyme adsorption.
At this time, the amount of the oil-and-fat hydrolase used is preferably 0.1 to 300% by mass, further 0.5 to 200% by mass, and further preferably 1 to 150% by mass with respect to the carrier mass from the viewpoint of industrial productivity. At the time of immobilization, the enzyme is put into a solution state, and it is preferable to adjust the pH to 3 to 7 with a buffer. The temperature at the time of immobilization is preferably 0 to 60 ° C, more preferably 3 to 40 ° C.

In order to enhance the activity of the immobilized oil-and-fat hydrolase, a treatment of adsorbing the fat-soluble fatty acid or its derivative on the carrier may be performed in advance before the immobilization of the oil-and-fat hydrolase. Examples of the method for performing the treatment include a method in which a fat-soluble fatty acid or a derivative thereof is once dispersed and dissolved in an organic solvent such as chloroform, hexane and ethanol, and then added to a carrier dispersed in water.
Examples of the fat-soluble fatty acid used include saturated or unsaturated, linear or branched-chain fatty acids having 8 to 18 carbon atoms, which may be substituted with hydroxyl groups. Specific examples thereof include capric acid, lauric acid, myristic acid, oleic acid, linoleic acid, α-linolenic acid, and ricinoleic acid. Examples of the derivative include an ester of these fatty acids and a monohydric or polyhydric alcohol, a phospholipid, and a derivative obtained by adding ethylene oxide to these esters. Specific examples thereof include methyl esters, ethyl esters, monoglycerides, diglycerides of the above fatty acids, ethylene oxide adducts thereof, polyglycerin esters, sorbitan esters, sucrose esters and the like. Two or more of these fat-soluble fatty acids or derivatives thereof may be used in combination.

The hydrolyzing activity of the fat hydrolase has a titer of 20 U / g (dry mass) or more, further 100 to 10,000 U / g (dry mass), and further 500 to 5000 U / g (dry mass) measured by the method described later. It is preferably in the range.

The amount (dry mass) of the fat hydrolase used in the enzymatic decomposition method can be appropriately determined in consideration of the activity of the enzyme, but is 0.1 to 20% by mass, further 0.2, based on the fat and oil. It is preferable to use ~ 15% by mass from the viewpoint of industrial productivity. In the case of the immobilized fat-and-fat hydrolase, it is preferable to use 1 to 20% by mass and further 2 to 15% by mass with respect to the fat and oil from the viewpoint of industrial productivity.

In order to cause the oil / fat hydrolase to act on the oil / fat, the oil / fat may be brought into contact with the oil / fat hydrolase. To do, etc. In the case of stirring, although it depends on the diameter of the reaction tank, 10 to 1000 r / min is preferable, and 10 to 1000 r / min is preferable from the viewpoint that the immobilized oil-and-fat hydrolase does not settle, crushing is suppressed, and the hydrolysis reaction proceeds efficiently. Is preferably 20 to 700 r / min, more preferably 30 to 500 r / min.

In the present invention, the hydrolysis of fats and oils can be carried out in a batch system, a continuous system, or a semi-continuous system. The oil and fat and water may be supplied into the device by either a parallel flow type or a countercurrent type. As the fat and oil and water supplied to the hydrolysis reaction apparatus, fat and oil and water that have been degassed or deoxidized in advance may be used, if necessary.

In the hydrolysis reaction, the water content in the reaction system may be 5 to 500% by mass, further 10 to 300% by mass, and further 20 to 200% by mass with respect to the fat and oil from the viewpoint of industrial productivity. preferable.
As a method of controlling the amount of water in the reaction system, (i) the method of measuring the water content of each component in advance by the Karl Fischer method or the like and controlling the total water content, (ii) the reaction component. There is a method of completely dehydrating and adding a predetermined amount of water later.
In the present invention, the water in the reaction system includes the water contained in the fat and oil and the fat and oil hydrolase in the water content.
In the present invention, the water added to the reaction system may be distilled water, ion-exchanged water, degassed water, tap water, well water or the like. Other water-soluble components such as glycerin may be mixed. If necessary, a buffer solution having a pH of 3 to 9 may be used so that the stability of the enzyme can be maintained.

The reaction temperature of hydrolysis can be determined by the characteristics of the enzyme, but from the viewpoint of improving the reaction rate and suppressing the inactivation of the enzyme, it is 0 to 80 ° C, further 10 to 70 ° C, and further 20 to 60. ° C is preferred.

The hydrolysis reaction of fats and oils in this step is carried out in the range of free fatty acid concentration of 50 to 84% by mass. The hydrolysis reaction is controlled by the free fatty acid concentration, and when the predetermined free fatty acid concentration is reached, the reaction is temporarily stopped and the water of the reaction system is replaced, so that the hydrolysis reaction of fats and oils proceeds efficiently in a short time. Moreover, the monoglyceride concentration in the reaction solution decreases.
The free fatty acid concentration is represented by the following formula (1) from the acid value and fatty acid composition of the oil phase.
Free fatty acid concentration (% by mass) = xxy / 56.11 / 10 (1)
(X = acid value of oil phase [mgKOH / g], y = average molecular weight obtained from fatty acid composition)
The acid value of the oil phase can be measured by "acid value (23.1-1996)" in "Standard Oil and Fat Analysis Test Method 2003" edited by the Japan Oil Chemists' Society.
In the hydrolysis reaction of fats and oils in this step, the free fatty acid concentration is 55% by mass or more, 60% by mass or more, and 83% by mass or less because the monoglyceride in the reaction solution can be reduced and the reaction time can be shortened. Further, it is preferably carried out at 82% by mass or less, further 81% by mass or less, and further preferably 80% by mass or less.

The reaction time for hydrolysis can be appropriately determined in consideration of the amount of oil and fat hydrolase used and the enzyme activity, but is preferably 1 to 24 hours, more preferably 2 from the viewpoint of industrial productivity. It is from 12 hours, more preferably 2.5 to 6 hours, still more preferably 3 to 4.5 hours.

The hydrolysis reaction is preferably carried out in the presence of an inert gas such as nitrogen so that contact with air is avoided as much as possible.

After hydrolysis, the aqueous phase and the oil phase are separated to obtain an oil phase. On the other hand, the aqueous phase is excluded from the reaction system. The aqueous phase and the oil phase can be separated by, for example, a static separation method, a centrifugal separation method, or the like.
The conditions for static separation and centrifugation can be set as appropriate depending on the state of separation. The oil phase after separating and removing the aqueous phase may be dehydrated under reduced pressure, if necessary.
The fat hydrolase used for hydrolysis can be reused for hydrolysis of fats and oils after separation and recovery.

[Step (B)]
This step is a step of adding fresh water to the oil phase obtained in the step (A) and hydrolyzing the fat and oil again by the enzymatic decomposition method.
The amount of water to be newly added is preferably such that the amount of water in the reaction system is 10 to 120% by mass and further 20 to 100% by mass with respect to the fat and oil.

The enzymatic decomposition of fats and oils in this step can be carried out by the same method as described above.
As the oil / fat hydrolase, a new enzyme may be used, or the one used in the step (A) may be reused, but from the viewpoint of industrial productivity, it is used in the step (A). It is preferable to reuse the product.
As for the hydrolyzing activity of the oil and fat hydrolase in this step, the titer measured by the method described later is 20 U / g (dry mass) or more, further 100 to 10000 U / g (dry mass), and further 500 to 5000 U. It is preferably in the range of / g (dry mass). The amount of the fat hydrolase used (dry mass) can be appropriately determined in consideration of the activity of the enzyme, but is 0.1 to 20% by mass and further 0.2 to 15% by mass with respect to the fat and oil. % It is preferable to use it from the viewpoint of industrial productivity. In the case of the immobilized fat-and-fat hydrolase, it is preferable to use 1 to 20% by mass and further 2 to 15% by mass with respect to the fat and oil from the viewpoint of industrial productivity.

By replacing the water in the reaction system, the enzymatic decomposition of fats and oils in this step proceeds in a short time. The hydrolysis reaction of fats and oils in this step may be carried out until the free fatty acid concentration is 85% by mass or more, further 86 to 98% by mass, and further 91 to 97% by mass because the free fatty acid concentration and yield can be increased. preferable. The reaction time for hydrolysis to reach such a free fatty acid concentration can be appropriately determined in consideration of the amount of fat hydrolase used and the enzyme activity, but is preferably 3 to 6 hours, more preferably 4 to 4 hours. 5 hours.

In order to obtain fatty acids as an oil phase from the reaction solution after hydrolysis, the aqueous phase and the oil phase may be separated from each other, and the aqueous phase and the oil / fat hydrolyzing enzyme may be removed from the oil phase.
The reaction solution contains unreacted fats and oils, partially hydrolyzed fats and oils, and the like in addition to fatty acids and glycerin, but in the present invention, monoglyceride is low. Therefore, oil-water separation can be facilitated.
The monoglyceride concentration in the reaction solution is preferably 8.5% by mass or less, more preferably 8% by mass or less, still more preferably 2 to 2 to 2, from the viewpoint of facilitating oil-water separation of the reaction solution and easily recovering fatty acids. It is 8% by mass. Here, in the present specification, the concentration of monoglyceride in the reaction solution is calculated by the following formula (2) by determining the glyceride composition of the oil phase of the reaction solution.
Monoglyceride concentration [mass%]
= Monoglyceride concentration [mass%] / (monoglyceride concentration [mass%] + diglyceride concentration [mass%] + triglyceride concentration [mass%]) x 100 (2)

[Analysis method]
(I) Measurement of glyceride composition The "glyceride composition" is prepared by adding 10 mg of a sample and 0.5 mL of a trimethylsilylating agent ("silylating agent TH", manufactured by Kanto Chemical Co., Inc.) to a glass sample bottle, sealing the bottle, and then sealing at 70 ° C. Was heated for 15 minutes. Distilled water (1.0 mL) and hexane (2.0 mL) were added thereto, and after mixing, the hexane layer was measured by gas chromatography (GLC).
Equipment: Hewlett-Packard 6890 type column; DB-1HT (J & W Scientific) 7m
Column temperature; initial = 80 ° C, final = 340 ° C
Temperature rise rate = 10 ° C / min, held at 340 ° C for 20 minutes Detector; FID, temperature = 350 ° C
Injection part; split ratio = 50: 1, temperature = 320 ° C
Sample injection volume; 1 μL
Carrier gas; helium, flow rate = 1.0 mL / min

(Ii) Calculation of Free Fatty Acid Concentration The free fatty acid concentration was determined by the following formula (1) after centrifuging the reaction solution (3000 r / min, 1 minute) and then measuring the acid value and fatty acid composition of the oil phase.
Free fatty acid concentration (% by mass) = xxy / 56.11 / 10 (1)
(X = acid value of oil phase [mgKOH / g], y = average molecular weight obtained from fatty acid composition)

(Iii) Measurement of acid value The acid value was measured according to "Acid value (23.1-1996)" in "Standard Oil and Fat Analysis Test Method 2003" edited by Japan Oil Chemists' Society.

(Iv) Measurement of fatty acid composition Fatty acids according to "Methyl esterification method (boron trifluoromethanol method) (2.4.1.2-1996)" in "Standard Fatty Acid Analysis Test Method 2003" edited by Japan Oil Chemists' Society. Methyl esters were prepared and the obtained samples were subjected to gas chromatography (GLC) for analysis of constituent fatty acids.

(V) Measurement of dry mass ratio About 1 g of the immobilized enzyme was weighed in a 20 mL sample bottle, and washed twice with acetone and hexane alternately. Further, it was washed with acetone, the solvent was volatilized by blowing nitrogen, and then it was dried in a constant temperature bath at 60 ° C. for 12 hours or more. The weight after drying was measured, and the dry mass ratio was obtained from the following formula (2).
Dry mass ratio [-] = (weight of resin after washing [g]) / (weight of immobilized enzyme before washing [g]) (2)

(Vi) Measurement of expression activity Add 5 g of immobilized enzyme and 50 g of rapeseed oil to a 100 mL three-necked flask, and stir at 430 r / min with a crescent blade (width 50 mm x height 20 mm) to 40 ° C in a water bath. It was heated. 30 g of distilled water was added thereto to start the reaction. Sampling was performed at the time of passage, oil and water were separated by centrifugation (3000 r / min, 1 minute), and then the acid value of the oil phase was measured. The time required for the acid value to reach 175 mgKOH / g was determined, and the expression activity was determined from the following formula (3).
Expression activity [U / g (dry mass)]
= (Acid value 175 arrival time [hr] /523.12) ^ (-1 / 1.0919)
× Canola oil [g] / (immobilized enzyme [g] × dry mass ratio [-]) (3)

[Preparation of immobilized enzyme]
Anion exchange resin Duolite A-568 (manufactured by Rohman and Haas, 96% by mass of particles having a particle size distribution of 150 to 850 μm) is crushed and classified, and 1 part by mass of a resin having 97% by mass of particles having a particle size of 150 to 425 μm. Was stirred in 10 parts by mass of N / 10 NaOH solution for 1 hour. After filtration, the mixture was washed with 10 parts by mass of ion-exchanged water, and pH was equilibrated with 10 parts by mass of 500 mM phosphate buffer (pH 7). After filtration, pH equilibration was performed twice for 2 hours with 10 parts by mass of 50 mM phosphate buffer (pH 7). After that, filtration was performed, the carrier was recovered, and then ethanol substitution was performed with 4 parts by mass of ethanol for 30 minutes. After filtration, 4.22 parts by mass of ethanol containing 1 part by mass of soybean fatty acid was added, and the soybean fatty acid was adsorbed on the carrier for 30 minutes. After recovering the carrier by filtration, the carrier was washed 4 times with 5 parts by mass of 50 mM phosphate buffer (pH 7) for 30 minutes each, and the carrier was recovered by filtration.
Next, 0.388 parts by mass of a commercially available lipase AY "Amano" (manufactured by Amano Enzyme) derived from the genus Candida cylindracea was contacted with an enzyme solution dissolved in 18 parts by mass of 50 mM phosphate buffer (pH 7) for 2 hours. , Immobilization was performed. After filtration, the immobilized enzyme was recovered and washed with 5 parts by mass of 50 mM phosphate buffer (pH 7) to remove the non-immobilized enzyme and protein. All of the above operations were performed at 20 ° C. Then, 4 parts by mass of rapeseed oil was added, and the mixture was stirred at 40 ° C. for 2 hours. After that, it was filtered and separated from fats and oils to obtain an immobilized enzyme.
The hydrolytic activity (activity to be expressed) of the immobilized enzyme was 2680 U / g (dry mass).

[Example 1]
25 g of the immobilized enzyme was weighed by dry weight and placed in a 1000 mL four-necked flask. 500 g of flaxseed oil and 300 g of distilled water were added thereto, and a hydrolysis reaction was carried out at 40 ° C. while stirring under a nitrogen stream. The water content in the reaction system was 62% by mass with respect to the fat and oil. During the reaction, the free fatty acid concentration was calculated while sampling the reaction solution over time.
Water was replaced when the free fatty acid concentration reached 61% by mass. Specifically, the immobilized enzyme was separated by filtration, and the oil phase and the aqueous phase were separated by centrifugation (6000 r / min, 10 minutes). Next, to the oil phase excluding the aqueous phase, the previously separated and recovered immobilized enzyme and 300 g of fresh distilled water were added, and the mixture was stirred under a nitrogen stream until the free fatty acid concentration reached 90% by mass at 40 ° C. The hydrolysis reaction was carried out again. At this time, the water content in the reaction system was 66% by mass with respect to the fat and oil.
The reaction solution was separated into oil and water by centrifugation to obtain fatty acids as an oil phase. The monoglyceride concentration was calculated by determining the glyceride composition of the oil phase when the free fatty acid concentration reached 90% by mass.

[Example 2]
Fatty acids were obtained according to the method described in Example 1 except that water was replaced when the free fatty acid concentration was 80% by mass.

[Comparative Example 1]
According to the method described in Example 1, a hydrolysis reaction was carried out until the free fatty acid concentration reached 90% by mass without replacing water to obtain fatty acids.

[Comparative Example 2]
Fatty acids were obtained according to the method described in Example 1 except that water was replaced when the free fatty acid concentration was 32% by mass.

[Comparative Example 3]
Fatty acids were obtained according to the method described in Example 1 except that water was replaced when the free fatty acid concentration was 88% by mass.

Table 1 shows the free fatty acid concentration at the time of water replacement, the reaction time until the free fatty acid concentration reaches 90% by mass, and the monoglyceride concentration.

As is clear from Table 1, by replacing the water in the reaction system at a specific time point, the hydrolysis reaction proceeded efficiently in a short time, and the monoglyceride in the reaction solution was significantly reduced.
On the other hand, in Comparative Example 1 in which the water was not replaced and Comparative Example 2 in which the free fatty acid concentration was low even after the water was replaced, the reaction time was long and the monoglyceride concentration was also high. Further, in Comparative Example 3 in which water was replaced when the free fatty acid concentration was high, the reaction time tended to be longer.

Claims (3)

Next steps (A) and (B):
(A) Water (excluding those containing glycerin) is added to fats and oils, hydrolyzed to a free fatty acid concentration of 60 to 82 % by mass by an enzymatic decomposition method using an immobilized fat and oil hydrolase, and then the aqueous phase. And the process of separating the oil phase and obtaining the oil phase,
(B) Fresh water (excluding those containing glycerin) is added to the oil phase obtained in step (A), and the oil and fat are hydrolyzed again by an enzymatic decomposition method using an immobilized oil and fat hydrolase to obtain monoglyceride. A method for producing fatty acids, which comprises a step of obtaining a reaction solution having a concentration of 8% by mass or less . The method for producing fatty acids according to claim 1, wherein in the step (B), a hydrolysis reaction by an enzymatic decomposition method is carried out until the free fatty acid concentration becomes 85% by mass or more. The method for producing a fatty acid according to claim 1 or 2, wherein in the step (B), a reaction solution having a monoglyceride concentration of 2 to 8% by mass is obtained by a hydrolysis reaction by an enzymatic decomposition method.