Process for manufacturing soybean paste, and soybean paste

Abstract

A method for producing a soybean paste having aroma and sweet taste characteristic of soybeans, with a grassy smell and an astringent taste being suppressed, and a soybean paste produced by the method are provided. Raw soybeans are immersed in water at normal temperature, and thus swollen soybeans are obtained having a swelling ratio (weight of swollen soybeans / weight of raw soybeans) of 1.7 or more. Subsequently, the swollen soybeans are immersed in hot water at a temperature of higher than or equal to 80ºC and lower than 90ºC for a time from 13 minutes to 30 minutes obtain heat-treated soybeans, and the heat-treated soybeans are further subjected to wet grinding, thereby a soybean paste being obtained. According to the present invention, a soybean paste having a favourable flavour can be obtained stably with a simple and convenient facility.

Description

[0001] The present invention relates to a method for producing soybean paste and soybean paste. More specifically, it relates to a method for producing soybean paste that has little grassy odor and astringency, and is rich in aroma and sweetness, and soybean paste obtained by the method thereof.

[0002] The plant-based protein contained in soybeans has an excellent balance of amino acids, and the lipids contain a large amount of linoleic acid, which is said to have a cholesterol-lowering effect. For this reason, soy-based processed foods such as tofu and soy milk are popular as health foods. Furthermore, soybean hypocotyls are known to contain high concentrations of nutrients such as isoflavones, which are believed to have cancer-preventive and osteoporosis-preventive effects, and saponins, which are believed to have cancer-preventive, antiviral, and antioxidant effects. However, the majority of these are discarded during the production of tofu and soy milk. For this reason, many attempts are being made to produce soy paste that makes effective use of all the components of soybeans.

[0003] Incidentally, when linoleic acid contained in soybeans comes into contact with oxygen, it is converted to n-hexanal through oxidation by lipoxygenase, a lipid oxidizing enzyme inherent in soybeans. n-hexanal is known to be the substance that causes the grassy smell of soybeans. For this reason, various methods of lipoxygenase inactivation have been attempted to improve the odor of soybean processed products.

[0004] For example, Japanese Patent Publication No. 2004-16120 (hereinafter referred to as "Patent Document 1") discloses a method for producing a soy milk-like beverage by dissolving dried soybean pulverized material in hot water and homogenizing it. Republished Japanese Patent Publication No. WO2004 / 00880 (hereinafter referred to as "Patent Document 2") discloses a method for producing a soybean processed material by pulverizing raw soybeans, adding water to swell the soybean powder, and then heating it. Japanese Patent Publication No. 2006-136294 (hereinafter referred to as "Patent Document 3") discloses a method for producing soybean paste by dry pulverizing raw soybeans to obtain dried soybean particles, and then adding water to the dried soybean particles and heating it. Japanese Patent Publication No. 2007-228851 (hereinafter referred to as "Patent Document 4") discloses a method for producing soy milk in which raw soy flour is dispersed and dissolved in hot water at a temperature of 80°C to 90°C (first heating), and then further heated at 95°C to 140°C (second heating). The methods described in Patent Documents 1 to 4 above are all common in that they involve pulverizing (dry pulverization) raw soybeans (dry soybeans, raw soybeans) without adding water, dispersing them in water, and then heating them (hereinafter, these methods may be abbreviated as the "dry pulverization and post-heating method"). However, since soybeans contain a large amount of lipids, a special pulverization device is required for dry pulverization (if necessary, refer to "Non-Patent Document 1" etc.). In addition, in the case of the "dry pulverization and post-heating method", there is a problem that the soy product becomes fishy due to the action of the aforementioned lipoxygenase as a result of the dry-pulverized soybean powder with a large surface area contacting oxygen in the air or dissolved oxygen in water.

[0005] Patent Publication No. 2007-222158 (hereinafter referred to as "Patent Document 5") discloses a method for grinding and heating soybeans by adding water to soybeans and then heating them. Re-published Patent WO2008 / 081948 (hereinafter referred to as "Patent Document 6") discloses a method for producing soy milk by grinding soybeans in a liquid together with squeezed water to obtain a soy liquid, preheating the soy liquid, and further heating it at a predetermined temperature. The methods described in Patent Documents 5 and 6 above are both methods for producing soy milk, and they are both common in that water is added to soybeans for pulverization (wet pulverization) and then heated (hereinafter, these methods may be abbreviated as the "wet pulverization and post-heating method"). Even in these "wet pulverization and post-heating methods", since the soybean grindings have a large surface area (contact area), the action of dissolved oxygen in water and lipoxygenase cannot be avoided, and there is a problem that the soy product becomes fishy.

[0006] Patent Publication No. 2007-289144 (hereinafter referred to as "Patent Document 7"), Patent Publication No. 2008-125 (hereinafter referred to as "Patent Document 8"), and Patent Publication No. 2003-23989 (hereinafter referred to as "Patent Document 9") disclose a method of heat-treating raw soybeans (hereinafter, raw soybeans) in hot water at a predetermined temperature for a predetermined time and then pulverizing them to obtain a soybean paste. In particular, Patent Document 9 states that "when soybeans are immersed in water, the lipoxygenase is activated and a fishy-causing substance is generated, and the produced soy milk becomes fishy." (Patent Document 9, paragraph

[0004] ). Japanese Patent Publication No. 2006-191860 (hereinafter referred to as "Patent Document 10") and its republication WO2010-073575 (hereinafter referred to as "Patent Document 11") disclose a method for producing soy milk by heating raw soybeans in hot water at a predetermined temperature for a predetermined time. Japanese Patent Publication No. 2006-129877 (hereinafter referred to as "Patent Document 12") discloses processed soybean powder material, soybean beverages, etc., obtained by heating raw soybeans with steam at a predetermined temperature for a predetermined time, followed by grinding and drying. The methods described in Patent Documents 7 to 12 all share the common feature of directly heating raw soybeans in hot water or steam without thoroughly immersing them in room-temperature water prior to the heat treatment (hereinafter, these methods may be abbreviated as the "direct heating and post-grinding method").

[0007] On the other hand, a method has also been disclosed in which, prior to the heat treatment, raw soybeans are soaked in water at room temperature for a predetermined time, then heat-treated at a high temperature, and further crushed to obtain soybean paste. For example, Japanese Patent Publication No. 2011-217642 (hereinafter referred to as "Patent Document 13") discloses a method for processing soybeans (Claim 4) in which raw soybeans are soaked in water, then heated with superheated steam, and then crushed into a puree or paste. Japanese Patent Publication No. 2007-244330 (hereinafter referred to as "Patent Document 14") discloses a method for processing soybeans by soaking them in water, then heating them under heated and pressurized conditions, and then grinding them. Patent Publication 2006-75011 (hereinafter referred to as "Patent Document 15") discloses a method for producing processed soybean liquid, in which soybeans are soaked in water, then heated under pressure, and then ground. Patent Publication 2002-262805 (hereinafter referred to as "Patent Document 16") discloses a method for producing soybean-derived food in which soybeans are added to water to swell, the swollen soybeans are boiled, and the boiled soybeans are ground. The methods described in Patent Documents 13 to 16 all share the common characteristic of immersing raw soybeans in water and then heating them at a high temperature. Regarding the heating at a high temperature, for example, in the heating treatment described in Patent Document 13, it is preferable to use superheated steam at 120 to 500°C; in the heating treatment described in Patent Document 14, the temperature conditions are in the range of 90 to 130°C (paragraph

[0040] of the same document); in the pressurized heating treatment described in Patent Document 15, it is preferable that the temperature be in the range of 110 to 125°C (paragraph

[0028] of the same document); and in the heating treatment described in Patent Document 16, boiling is performed under normal pressure or under pressure (paragraph

[0025] of the same document). In other words, the inventions disclosed in Patent Documents 13 to 16 all share the common feature of employing a high temperature range of 90°C or higher as the temperature for the heat treatment (hereinafter, these methods may be abbreviated as the "high-temperature heating and post-grinding method").

[0008] The "direct heating and post-grinding method" and the "high-temperature heating and post-grinding method" are considered to be more effective in suppressing the generation of grassy odor components by lipoxygenase compared to the "dry grinding and post-heating method" and the "wet grinding and post-heating method" because they inactivate lipoxygenase before the grinding process.

[0009] Patent Publication No. 2004-16120 (republished) Patent WO2004 / 00880 Patent Publication No. 2006-136294 Patent Publication No. 2007-228851 Patent Publication No. 2007-222158 (republished) Patent WO2008 / 081948 Patent Publication No. 2007-289144 Patent Publication No. 2008-1 Patent Publication No. 25, Patent Publication No. 2003-23989, Patent Publication No. 2006-191860, Republished WO2010-073575, Patent Publication No. 2006-129877, Patent Publication No. 2011-217642, Patent Publication No. 2007-244330, Patent Publication No. 2006-75011, Patent Publication No. 2002-262805

[0010] Journal of the Japan Society for Food Science and Technology, Vol. 58, No. 11, pp. 552-558

[0011] The present inventors attempted to manufacture soybean paste using the "direct heating and post-grinding method" represented by the methods described in Patent Documents 7 to 12 and the "high-temperature heating and post-grinding method" represented by the methods described in Patent Documents 13 to 16, and found that the following problems still exist.

[0012] In other words, with the "direct heating and post-grinding method," while increasing the heating time tends to reduce the grassy and astringent taste, the aroma and sweetness decrease significantly. Ultimately, it was found that, as long as the "direct heating and post-grinding method" is used, it is difficult to achieve both "suppression of grassy and astringent taste" and "preservation of aroma and sweetness" in soybean paste by adjusting only the temperature and heating time.

[0013] On the other hand, it was found that even in the "high-temperature heating and post-grinding method," as long as the high-temperature heating conditions of 90°C or higher are used, it is difficult to achieve both the "suppression of grassy odor and astringency" and the "preservation of aroma and sweetness" of the soybean paste.

[0014] As described above, none of the conventional methods are yet sufficient in that they can produce soybean paste that does not impair the original flavor of soybeans and is free from grassy or bitter tastes. Therefore, the inventors set the goal of establishing a simple and efficient method for producing soybean paste that is free from grassy or astringent tastes and retains the original flavor of soybeans, and proceeded with their research.

[0015] As a result of diligent research to achieve the above objectives, the present inventors have found that when obtaining soybean paste, they use raw soybeans instead of dried soybean powder as the starting material, first immerse the raw soybeans in water at room temperature to obtain swollen soybeans having a predetermined swelling ratio, then heat the swollen soybeans in hot water at a predetermined temperature under normal pressure for a predetermined time, and then grind them, thereby obtaining a soybean paste in which the grassy smell and astringency are suppressed, the original aroma of soybeans is retained, and the sweetness is increased, and furthermore, they have found that the flavor and taste of the soybean paste obtained in this way are even better when the content of a specific trace component in a sample of a predetermined solid content concentration of the soybean paste is below a specific amount, and have completed the present invention.

[0016] The present invention is based on the discovery that when raw soybeans are heated, sweet components are formed in the soybeans, while these sweet components gradually dissipate from the surface of the soybeans in contact with hot water due to diffusion. Furthermore, the present invention is based on the novel discovery that by soaking raw soybeans in water to make them swollen soybeans prior to the heating process, the heating time required to deactivate lipoxygenase in the soybeans in the subsequent heating process can be shortened. Furthermore, the present invention is based on the discovery that by soaking swollen soybeans, rather than raw soybeans, in hot water and heating them, astringent components in the soybeans can be efficiently removed.

[0017] In other words, the present invention is (i) A swelling process in which raw soybeans are soaked in water at room temperature to obtain swollen soybeans, (b) A heating step in which the swollen soybeans obtained in step (a) above are heated to obtain heated soybeans, A method for producing soybean paste, comprising: (c) a grinding step of wet grinding the heated soybeans obtained in step (b) above to obtain a soybean grinding product, The above step (i) is a step to make the swelling ratio (weight of swollen soybeans / weight of raw soybeans) 1.7 or more, and The above step (b) is a step of immersing the swollen soybeans in hot water at 80°C or higher but less than 90°C for a period of 13 minutes or more but less than 30 minutes. This invention provides a method for producing soybean paste characterized by the following:

[0018] Furthermore, the present invention relates to a soybean paste obtained by the above method, wherein in a sample of the soybean paste with a solid content concentration of 20% by weight, 1) The n-hexanal content is 0.05 μg / g or less, and 2) To provide a soybean paste having a soy saponin-derived soy saponol A content of 120 μg / g or less.

[0019] The soybean paste obtained by the method of the present invention has no grassy or astringent taste and retains the original flavor of soybeans, so it can be eaten on its own or used as an ingredient for soybean hamburgers and other products.

[0020] In the present invention, raw soybeans are used as the starting material instead of soybean powder. There are no particular restrictions on the variety or origin of the soybeans, and various varieties of soybeans from different producing regions can be used.

[0021] First, an overview of the method of the present invention will be described. As described above, the present invention comprises (a) a swelling step, (b) a heating step, and (c) a grinding step. In the present invention, if any of the above steps (a) to (c) are omitted, the objective cannot be achieved. Furthermore, in this invention, raw soybeans must be processed in the order of steps (a), (b), and (c) described above. For example, if soybeans are subjected to a swelling process, then a grinding process, and then a heating process, the ground soybeans immediately after the grinding process still contain active lipoxygenase. As a result, the lipid components in the ground soybeans are easily oxidized upon contact with air, and the resulting soybean paste has a strong grassy odor, thus failing to achieve the objective of the present invention.

[0022] The method of the present invention will be described below step by step. a) Swelling process; The swelling process of the present invention involves immersing raw soybeans in room temperature water to obtain swollen soybeans. By swelling the soybeans, the highly thermally conductive water is sufficiently contained in the core of the soybean grain. As a result, when the swollen soybeans are subjected to the subsequent heating process, heat is transferred more quickly from the surface to the core of the soybean compared to when raw soybeans are directly subjected to the heating process. Therefore, in the heating process described later in (b), it becomes possible to shorten the time required to deactivate the enzyme lipoxygenase in the soybeans. As a result, the inventors estimate that the loss of both aroma and sweetness components from the soybeans can be minimized.

[0023] Therefore, if this swelling step is omitted, it will be difficult to remove the grassy and bitter taste while maintaining the aroma and sweetness of the soybeans by simply adjusting the temperature and time of the heating step described in (b) below. Thus, in the present invention, subjecting the soybeans to the swelling step is an essential requirement.

[0024] In this swelling process, raw soybeans absorb water and become swollen soybeans. At this time, it is necessary to control the swelling ratio of the soybeans (weight of swollen soybeans / weight of raw soybeans) to be 1.7 or higher. If the swelling ratio is less than 1.7, the water will not penetrate sufficiently into the soybean tissue, and as a result, the effects of the swelling process described above will not be fully realized. The swelling ratio is preferably 1.8 or higher. On the other hand, even if the swelling ratio exceeds 2.2, the effects of the swelling process described above will not be obtained in proportion to the increase in the swelling ratio, and this is not a good strategy in terms of production efficiency.

[0025] In this swelling process, raw soybeans are immersed in room temperature water in order to achieve the above-mentioned swelling ratio. Here, room temperature refers to a temperature of 5°C to 35°C. If the water temperature is below 5°C, the time required for raw soybeans to absorb water sufficiently will be longer, which is not advantageous in terms of the efficiency of soybean paste production. The water temperature is preferably 10°C or higher, more preferably 15°C or higher, and even more preferably 25°C or higher. On the other hand, even if the water temperature exceeds 35°C, it is not advisable because it will not shorten the soaking time of raw soybeans enough to justify the increase in temperature.

[0026] In order to obtain swollen soybeans with the aforementioned swelling ratio, raw soybeans are soaked in room temperature water for approximately 90 to 180 minutes. The water ratio (weight of water / weight of raw soybeans) should be sufficient to fully immerse the raw soybeans in the container, and is usually in the range of approximately 2 to 6.

[0027] In addition to the method of leaving raw soybeans to stand in water, the swelling process can also employ modified methods such as a method of stirring the raw soybeans gently under conditions that do not damage them in order to refresh the layer of water in contact with the surface of the raw soybeans, or a method of bringing them into contact with flowing water.

[0028] b) Heating process; In this process, the swollen soybeans obtained in the swelling process are heated to produce heated soybeans. If the swollen soybeans are subjected to the grinding process described later without going through this heating process, the active enzyme lipoxygenase in the soybeans will generate the grassy odor component n-hexanal, making it impossible to obtain soybean paste of the desired quality. Furthermore, since this heating process can be carried out at atmospheric pressure, no pressurizing equipment is required.

[0029] In this process, the key point is to immerse the swollen soybeans in hot water, and if they are heated with steam, for example, the objective of the present invention cannot be achieved. By immersing the swollen soybeans in hot water, the astringent components in the soybeans are extracted by the hot water, and the resulting soybean paste is of excellent quality, possessing aroma and sweetness while having little grassy or astringent taste. If the swollen soybeans are heated with steam instead of hot water, the effect of extracting the astringent components from the swollen soybeans is poor, and the resulting soybean paste will remain astringent, thus failing to achieve the objective of the present invention. Therefore, in this heating process, it is essential to maintain a sufficient amount of hot water so that the swollen soybeans are immersed in the hot water throughout the process.

[0030] In this heating process, the temperature of the hot water must be 80°C or higher and less than 90°C. If the hot water temperature is below 80°C, the lipoxygenase deactivation effect is insufficient, and as a result, the ground soybean product that undergoes the next grinding process generates grassy-tasting components due to contact with oxygen and the action of lipoxygenase. On the other hand, if the hot water temperature is 90°C or higher, the grassy-tasting and astringent flavor of the soybean paste is suppressed, but it lacks flavor and sweetness. This is presumed to be because when the hot water temperature is 90°C or higher, the flavor and sweetness components in the soybeans tend to diffuse and leach into the hot water in a short time. The hot water temperature is preferably between 82°C and 88°C. When the hot water temperature is between 82°C and 88°C, both bitterness and grassy taste are removed, and a soybean paste with the unique flavor and sweetness of soybeans is obtained. The most preferred hot water temperature is between 84°C and 86°C. When the hot water temperature is between 84°C and 86°C, as described later, the "acceptable range of heating time" for obtaining a soybean paste with suppressed grassy taste and bitterness, and good aroma and sweetness is widened, and the process control benefit of reduced variation in soybean quality can also be enjoyed. While the present invention does not exclude methods of raising or lowering the temperature of hot water at a constant rate while controlling the temperature within a range of 80°C to less than 90°C, from the viewpoint of controllability of the hot water temperature and uniformity of product quality, it is preferable to control the hot water temperature within ±2°C of the set temperature, and more preferable to control it within ±1°C of the set temperature.

[0031] In this heating step, it is necessary to control the hot water temperature within the above range and to heat for 13 minutes or more and 30 minutes or less. If the heating time is less than 13 minutes, the grassy smell and astringency of the soybean paste will become strong. On the other hand, if the heating time exceeds 30 minutes, the aroma and sweetness of the soybean paste will dissipate. The lower limit of the heating time is preferably 15 minutes, and more preferably 18 minutes. The upper limit of the heating time is preferably 27 minutes, and more preferably 25 minutes.

[0032] When the hot water temperature is 82°C or higher and 88°C or lower, controlling the heating time to 15 minutes or higher and 27 minutes or lower will further suppress the grassy taste and astringency, and produce a soybean paste with better aroma and sweetness.

[0033] When the hot water temperature is 82°C or higher and less than 84°C, controlling the heating time to 18 minutes or more and 25 minutes or less will further suppress the grassy taste and astringency, and produce a soybean paste with better aroma and sweetness.

[0034] When the hot water temperature is between 84°C and 86°C, controlling the heating time to between 18 minutes and 27 minutes will further suppress the grassy and astringent taste, and produce a soybean paste with better aroma and sweetness.

[0035] When the hot water temperature is between 86°C and 88°C, controlling the heating time to 18 minutes or more and 23 minutes or less will further suppress the grassy taste and astringency, and produce a soybean paste with better aroma and sweetness.

[0036] H) Grinding process; This process involves wet grinding the heated soybeans obtained in the heating process described above, resulting in a soybean grinding product in which the finely ground heated soybean particles are suspended in water. (Hereafter, the soybean-derived suspended particles in the soybean grinding product will simply be referred to as "suspended particles.") Various commercially available wet grinders can be suitably used for grinding the heated soybeans in this grinding process. In this grinding process, it is preferable that the heated soybeans are finely ground so that the average particle size of the suspended particles is in the range of 20 to 200 μm. In this invention, the average particle size of the suspended particles refers to the particle size corresponding to 50 percent of the cumulative particle size volume distribution, which is obtained by measurement based on the laser diffraction scattering principle. By setting the average particle size within the above range, the final soybean paste obtained will be mild and have a pleasant texture. It is more preferable that the average particle size of the suspended particles in the ground soybean product is 20 to 150 μm. Furthermore, it is even more preferable that the average particle size of the suspended particles is within the above range, and the particle size of 90 percent of the cumulative particle size volume distribution is 500 μm or less. When measuring, the ground soybean product is left to stand at room temperature for 24 hours so that the suspended particles reach a state of sufficient swelling equilibrium with water. The ground soybeans that have undergone this process are used as is, or water is added as needed to adjust the consistency, to make soybean paste.

[0037] (ii) Retort sterilization process; In the present invention, an optional step may be included following the grinding step described in (c) above: a retort sterilization step. By implementing this process, the quality of the soybean paste can be maintained over a long period of time. This process is carried out in accordance with the "Standards for Quality Labeling of Retort Pouch Foods" (Ministry of Agriculture, Forestry and Fisheries Notification No. 1680, December 19, 2000).

[0038] Next, a soybean paste obtained by the above method will be described, which has a controlled n-hexanal content and a controlled soy saponin-derived soy saponol A content, and is particularly excellent in flavor and taste. (Hereinafter, a soybean paste obtained by the method of the present invention, in which the above trace component amounts are controlled, may be referred to as "the soybean paste of the present invention.") 1) n-hexanal content The soybean paste of the present invention is characterized in that the n-hexanal content in a sample with a solid content of 20% by weight is 0.05 μg / g or less. When the n-hexanal content is kept to 0.05 μg / g or less, the grassy taste is suppressed to the point where it is only slightly noticeable, resulting in a soybean paste with good flavor. When the n-hexanal content is kept to 0.03 μg / g or less, the soybean paste has an even better flavor.

[0039] 2) Content of soy saponin-derived soy saponol A Soybeans are known to contain trace amounts of saponin glycosides collectively known as soy saponins. Soy saponins are broadly classified into Group A saponins and DDMP saponins based on differences in the chemical structure of the aglycone (the non-sugar portion of the glycoside). Group A saponins are considered to be the cause of unpleasant tastes. Group A saponins have soy sapogenol A (3β,21β,22β,24-tetrahydroxyolean-12-ene, which has hydroxyl groups at positions C-3,21,22,24) as their aglycone. Therefore, by hydrolyzing a soybean sample (soybean paste) and quantifying the soy sapogenol A in the hydrolysate, it is possible to obtain an indicator of the Group A saponin content in soybean paste. The soybean paste of the present invention is characterized in that the content of soy sapogenol A derived from soybean saponins in a sample of the soybean paste with a solid content of 20% by weight is 120 μg / g or less. When the content of soy sapogenol A is kept to 120 μg / g or less, the soybean paste has less astringency and a good taste. When the content of soy sapogenol A is kept to 100 μg / g or less, the astringency is further suppressed, and as a reflex effect, the sweetness is more easily perceived, resulting in a soybean paste with an even better taste.

[0040] Soybean paste in which the content of the above trace components (n-hexanal, soy saponin-derived soy sapogenol A) is controlled to the above range can be effectively obtained in the method for producing soybean paste of the present invention by immersing swollen soybeans in hot water at 82°C to 88°C for a period of 15 minutes to 27 minutes. It can be reliably obtained by immersing swollen soybeans at a temperature of 84°C to 86°C for a period of 18 minutes to 27 minutes.

[0041] In the following Examples, Comparative Examples, and Reference Examples, sensory tests and analytical tests were conducted according to the following procedures. <<Sensory Test>> Four panelists evaluated the items of beany odor, astringency, aroma, and sweetness of the soybean paste obtained in the Examples, etc., and ranked them in five grades according to the intensity. The average value of the evaluation scores of the four panelists was taken as the evaluation score of that item. When the evaluation score of beany odor or astringency was 4.0 or higher, or when the evaluation score of aroma or sweetness was 2.0 or lower, it was regarded as "unqualified" (indicated as "poor" in the table), and otherwise as "qualified" (indicated as "good" in the table). Among the "qualified" evaluations, when the evaluation scores of both beany odor and astringency were 3.0 or lower, and the evaluation scores of both aroma and sweetness were 3.0 or higher, it was particularly regarded as "extra high quality" (indicated as "excellent" in the table). Note that the rank evaluation scores for each item are as follows: Beany odor: Rank 1 (Almost no beany odor is felt.) Rank 2 (A faint beany odor is slightly felt.) Rank 3 (A slight beany odor is felt.) Rank 4 (A distinct beany odor is felt.) [[ID=2F]] Rank 5 (A strong beany odor is felt.) Astringency: Rank 1 (Almost no astringency is felt.) Rank 2 (A faint astringency is slightly felt.) Rank 3 (A slight astringency is felt.) Rank 4 (A distinct astringency is felt. It lingers on the tongue.) Rank 5 (A strong astringency is felt.) Aroma: Rank 1 (Almost no aroma is felt.) Rank 2 (A faint aroma is slightly felt.) Rank 3 (A weak aroma is felt.) Rank 4 (A distinct aroma is felt.) Rank 5 (A strong aroma is felt.) Sweetness: Rank 1 (Almost no sweetness is detected.) Rank 2 (A faint sweetness can be detected.) Rank 3 (A slight sweetness can be detected.) Rank 4 (Sweetness is clearly noticeable.) Rank 5 (I can taste a strong sweetness.)

[0042] Quantitative determination of n-hexanal The quantification of n-hexanal was performed by headspace GC / MS. [Headspace GC / MS measurement conditions] Approximately 2 g of soybean paste is accurately weighed, placed in a 20 mL vial with 3 mL of ultrapure water, and sealed. The vial is then kept at 70°C for 20 minutes. Next, a sample is taken using the equilibrium headspace method and subjected to GC / MS analysis. The equipment and analytical conditions used are as follows: Equipment used: GC / MS (Agilent 7890A / 7000), Autosampler (GERSTEL MPS2XL) • Analytical column: DB-5ms, length 30 mm, inner diameter 0.25 mm, film thickness 0.25 μm (manufactured by Agilent J&W) ・Inlet temperature: 250℃ • Injection mode: Split (Split ratio 50:1) • Heating conditions: Maintain 40°C for 30 minutes, then increase the temperature at 10°C per minute up to 70°C, and once 70°C is reached, increase the temperature at 20°C per minute, and once 250°C is reached, maintain that temperature. Carrier gas: Helium Ion source temperature: 280°C Ionization method: Electron ionization (70 eV) • Detection mode: SIM (Select Ion Monitoring) mode • Measured ions (m / z): 56, 72, 82 ・Injection volume: 1000μL The amount of n-hexanal in the sample was determined using a pre-prepared calibration curve.

[0043] Quantitative determination of soy sapogenol A [Extraction and hydrolysis of soy saponins] Approximately 600 mg of soybean paste is accurately weighed, 6 mL of 70% ethanol (containing 0.1% acetic acid) is added, and the mixture is stirred using a vortex mixer. After standing at 25°C for 48 hours, a soybean saponin extract is obtained. [Hydrolysis of soy saponins] The above soybean saponin extract is centrifuged in a high-speed centrifuge for 10 minutes, and 300 μL of the supernatant is collected. 30 μL of hydrochloric acid is added, and the mixture is stirred using a vortex mixer. After stirring, liquid paraffin is added to the surface of the sample, and the mixture is heated at 80°C for 6 hours to hydrolyze the saponin components. The resulting hydrolyzed solution is allowed to cool and then subjected to high-performance liquid chromatography analysis. [High-performance liquid chromatography] The soyasapogenol A content in the above hydrolyzed solution was determined by high-performance liquid chromatography. The equipment and analytical conditions used are as follows. • Measurement equipment: High-performance liquid chromatograph (Waters Alliance e2695 / 2487 UV-VIS, detector: UV detection method) Mobile phase: Water / acetonitrile / acetic acid (volume ratio 4:6:0.01) ・Injection volume: 10μL ・Flow rate: 1.0mL / min ・Ultraviolet wavelength: 210nm • Column: InertSustain C8 4.6×150mm 5μm (GL Sciences Co., Ltd.) Column temperature: 40°C The qualitative determination of soy sapogenol A in the sample is performed by comparing it with the retention time of a pre-prepared standard sample of soy sapogenol A, and the quantitative determination is performed by the calibration curve method.

[0044] The present invention will be specifically illustrated below with reference to examples. [Example 1] <<Preparation of soybean paste>> Raw soybeans were subjected to the following swelling, heating, and grinding processes to produce soybean paste. 1. Swelling process 100g of raw soybeans were added to a container with 400g of water and soaked for 180 minutes while maintaining the water temperature at 30°C. After that, the soybeans were separated to obtain swollen soybeans. The swelling ratio of the soybeans (weight of swollen soybeans / weight of raw soybeans) was 2.0. 2. heating process A container was filled with 1000g of fresh water and heated to 85°C. Next, 200g of swollen soybeans (containing 100g of raw soybeans) were immersed in the hot water and kept at 85°C for 20 minutes. Then, the soybeans were separated and immediately cooled under running water to obtain heated soybeans. The swelling ratio of the heated soybeans (weight of heated soybeans / weight of raw soybeans) was 2.2. 3. Grinding process 220 g of heated soybeans (containing 100 g of raw soybeans) were mixed with 280 g of water and ground using a wet grinder to obtain a ground soybean product with a solid content concentration (weight of raw soybeans / weight of ground soybeans) of 20% by weight. (In all of the following examples, comparative examples, and reference examples, the solid content concentration was 20% by weight.) Using a laser diffraction scattering particle size distribution analyzer (Beckman Coulter LS13320), the average particle size of the suspended particles was measured to be 100 μm. The particle size at 90 percent of the cumulative volume distribution was 230 μm. Next, the ground soybean product was subjected to retort sterilization in accordance with the "Standards for Quality Labeling of Retort Pouch Foods" (Ministry of Agriculture, Forestry and Fisheries Notification No. 1680, December 19, 2000). A sensory evaluation was conducted on the obtained soybean paste. The results are shown in Table 1. The grassy and astringent taste was suppressed, and it emitted a subtle aroma and exhibited a pleasant sweetness. n-hexanal and soy sapogenol A were quantified in soybean paste. The results are shown in Table 1.

[0045] [Comparative Example 1] In Example 1, the swelling step was omitted, and the heating step was performed in the same manner as in Example 1, except that 100 g of raw soybeans were directly immersed in hot water instead of swollen soybeans. The swelling ratio of the heated soybeans (weight of heated soybeans / weight of raw soybeans) was 2.0. Next, the heating step, grinding step, and retort sterilization treatment were performed in the same manner as in Example 1 to obtain soybean paste. A sensory evaluation of the obtained soybean paste was conducted. The results are shown in Table 1. Compared to the soybean paste of Example 1, the sweetness was slightly better, but the grassy and astringent taste was stronger.

[0046] [Reference example 1] In Comparative Example 1, soybean paste was obtained in the same manner as in Comparative Example 1, except that the heating time in the heating process was further extended to 60 minutes, and the same test was conducted. The results are shown in Table 1. Compared to Comparative Example 1, the grassy taste was improved, but the astringency remained strong, while the sweetness was reduced, resulting in a soybean paste with inferior flavor.

[0047] [Reference example 2] In Comparative Example 1, soybean paste was obtained in the same manner as in Comparative Example 1, except that the heating time in the heating process was extended to 120 minutes, and the same tests were conducted. The results are shown in Table 1. Compared to Comparative Example 1, the grassy smell and astringency were improved, but the resulting soybean paste lacked aroma and sweetness.

[0048] [Reference example 3] In Comparative Example 1, soybean paste was obtained in the same manner as in the heating process, except that the hot water temperature in the heating step was set to 90°C and the heating time to 10 minutes, and the same test was performed. The results are shown in Table 1. The resulting soybean paste had a strong grassy and astringent taste and a weak aroma.

[0049] [Reference example 4] In Reference Example 3, soybean paste was obtained in the same manner as in the previous example, except that the heating time in the heating process was set to 20 minutes, and the same tests were conducted. The results are shown in Table 1. While the aroma and sweetness were at acceptable levels, the soybean paste had a strong grassy and astringent taste.

[0050] [Reference example 5] In Reference Example 3, soybean paste was obtained in the same manner as in the previous example, except that the heating time in the heating process was set to 25 minutes, and the same test was conducted. The results are shown in Table 1. While the grassy odor and astringency reached acceptable levels, both the aroma and sweetness were lost, resulting in a soybean paste lacking flavor. From Comparative Example 1 and Reference Examples 1-5, it is clear that if the swelling process is omitted, even if the temperature of the hot water and heating time in the heating process are adjusted, a soybean paste with a balanced flavor—one that suppresses grassy and astringent tastes while exhibiting aroma and sweetness—cannot be obtained.

[0051] [Comparative Example 2] In Example 1, a soybean paste was obtained in the same manner as in Example 1, except that the heating step of immersing the swollen soybeans in 85°C hot water was replaced with a step of placing the swollen soybeans in an 85°C steam atmosphere. The same tests were then conducted. The results are shown in Table 2. Compared to the case where the soybeans were immersed in hot water, the paste was sweeter but lacked aroma, and on the other hand, it had a strong grassy and astringent taste. (For the sake of comparison, the results of Example 1 are reproduced in Table 2.)

[0052] [Reference example 6] In Comparative Example 2, soybean paste was obtained in the same manner except that the heating time was 60 minutes, and the same test was conducted. The results are shown in Table 2. Although the heating time was extended, the flavor of the soybean paste was at the same level as in Comparative Example 2, and almost no improvement in flavor was observed.

[0053] [Reference Example 7] In Comparative Example 2, soybean paste was obtained in the same manner except that the heating time was 90 minutes, and the same test was conducted. The results are shown in Table 2. Even when the heating time was further extended, the aroma became even weaker, and the flavor of the soybean paste did not improve.

[0054] [Reference example 8] In Comparative Example 2, soybean paste was obtained in the same manner as in the previous example, except that the steam temperature was set to 90°C and the heating time to 10 minutes, and the same test was conducted. The results are shown in Table 2. The resulting soybean paste had excellent sweetness, but lost its aroma, while also having a strong grassy and astringent taste.

[0055] [Reference Example 9] In Reference Example 8, soybean paste was obtained in the same manner except that the heating time was 20 minutes, and the same test was conducted. The results are shown in Table 2. The aroma was improved compared to Reference Example 8, but the soybean paste still had a strong grassy and astringent taste.

[0056] [Reference Example 10] In Reference Example 8, soybean paste was obtained in the same manner except that the heating time was 60 minutes, and the same test was conducted. The results are shown in Table 2. The aroma was further improved compared to Reference Example 9, but the soybean paste still had a strong astringent taste. From Comparative Example 2 and Reference Examples 6-10, it can be seen that even after a swelling process, if the subsequent heating process is steam heating rather than hot water immersion, it is difficult to remove the grassy and astringent taste, even if the heating time is extended to more than 30 minutes.

[0057] [Comparative Example 3] In Example 1, soybean paste was obtained and the same tests were conducted, except that the hot water temperature in the heating process was set to 75°C. The results are shown in Table 3. Compared to Example 1, the resulting soybean paste had an extremely strong grassy odor and astringent taste. (For the sake of comparison, the results of Example 1 are also shown again in Table 3.)

[0058] [Reference Example 11] In Comparative Example 3, soybean paste was obtained in the same manner as in Comparative Example 3, except that the heating time in the heating process was 60 minutes, and the same test was conducted. The results are shown in Table 3. Although the grassy smell was improved compared to Comparative Example 3, the aroma and sweetness were lost, resulting in a soybean paste lacking flavor.

[0059] [Example 2] In Example 1, soybean paste was obtained in the same manner as in Example 1, except that the hot water temperature in the heating step was set to 80°C, and a sensory evaluation was conducted. The results are shown in Table 3. Compared to Example 1, the grassy odor and astringency were slightly stronger, but a soybean paste at an acceptable level was obtained. n-hexanal and soyasapogenol A in the soybean paste were quantified. The results are shown in Table 3.

[0060] [Example 3] Soybean paste was obtained in the same manner as in Example 1, except that the hot water temperature in the heating step was set to 88°C, and the same tests were performed. The results are shown in Table 3. Soybean paste with the same flavor as in Example 1 was obtained. n-hexanal and soyasapogenol A in the soybean paste were quantified. The results are shown in Table 3.

[0061] [Comparative Example 4] In Example 1, soybean paste was obtained in the same manner as in Example 1, except that the hot water temperature in the heating step was set to 90°C, and the same tests were conducted. The results are shown in Table 3. Although the grassy odor and astringency were suppressed, the resulting soybean paste lacked aroma and sweetness. The n-hexanal and soyasapogenol A in the soybean paste were quantified. The results are shown in Table 3.

[0062] [Reference Example 12] In Comparative Example 4, soybean paste was obtained in the same manner except that the heating time in the heating process was 13 minutes. The results are shown in Table 3. Although the sweetness increased compared to Comparative Example 4, the soybean paste had increased grassy and astringent tastes, and the aroma was inferior. From Examples 1-3, Comparative Example 3, Reference Example 11, Comparative Example 4, and Reference Example 12, it is clear that when the hot water temperature is below 80°C or above 90°C, it is difficult to achieve both "removal of grassy and astringent taste" and "preservation of aroma and sweetness" simply by adjusting the heating time.

[0063] [Comparative Example 5] In Example 1, soybean paste was obtained in the same manner as in Example 1, except that the heating time in the heating step was 10 minutes. The results are shown in Table 4. Compared to Example 1, the resulting soybean paste had significantly less aroma and significantly increased grassy and astringent taste. (For the sake of comparison, the results of Example 1 are also shown again in Table 4.) n-hexanal and soyasapogenol A in the soybean paste were quantified. The results are shown in Table 4.

[0064] [Examples 4-9] In Example 1, soybean paste was obtained in the same manner as in Example 1, except that the heating time in the heating step was set to 13, 15, 18, 25, 27, and 30 minutes, respectively. The results are shown in Table 4. In all cases, a good soybean paste was obtained in which the grassy smell and astringency were suppressed, and which had aroma and sweetness.

[0065] [Comparative Example 6] In Example 1, soybean paste was obtained in the same manner as in Example 1, except that the heating time in the heating step was 35 minutes. The results are shown in Table 4. Compared to Example 1, the grassy smell and astringency were improved, but the soybean paste had a poor flavor, lacking aroma and sweetness. n-hexanal and soyasapogenol A in the soybean paste were quantified. The results are shown in Table 4. Examples 4-9 and Comparative Example 6 show that when the hot water temperature in the heating process is 85°C, a soybean paste with a fragrance and sweetness is obtained by heating for 13 minutes or more and 30 minutes or less, while suppressing both the grassy smell and astringency. A soybean paste with an even better balance of flavor is obtained by controlling the heating time to 15 minutes or more and 27 minutes or less, and a soybean paste with an even better balance of flavor is obtained by controlling the heating time to 18 minutes or more and 27 minutes or less.

[0066] [Examples 10-13] In Example 1, soybean paste was obtained in the same manner as in Example 1, except that the hot water temperature in each heating step was set to 82°C and the heating time was set to 15, 18, 23, and 25 minutes, respectively. The results are shown in Table 5. In all cases, soybean paste was obtained with suppressed grassy odor and astringency, and with good aroma and sweetness. In particular, soybean paste with excellent flavor was obtained by heating for 18 minutes or more and 23 minutes or less. n-hexanal and soyasapogenol A were quantified in the soybean paste obtained with a heating time of 15 minutes. The results are shown in Table 5.

[0067] [Examples 14-17] In Example 1, soybean paste was obtained in the same manner as in Example 1, except that the hot water temperature in each heating step was set to 88°C and the heating time was set to 15, 18, 23, and 25 minutes, respectively. The results are shown in Table 5. In all cases, soybean paste was obtained with suppressed grassy odor and astringency, and with good aroma and sweetness. In particular, soybean paste with excellent flavor was obtained by heating for 18 minutes or more and 23 minutes or less.

[0068] From Examples 1 to 17 above, it is clear that by setting the hot water temperature to 80°C or higher and less than 90°C in the heating process, a soybean paste can be obtained that has both aroma and sweetness while suppressing the grassy smell and astringency. In particular, when the hot water temperature is controlled to around 85°C, it is clear that the allowable time range in which both the removal of the grassy smell and astringency and the preservation of aroma and sweetness can be achieved is wider than in other temperature ranges.

[0069] [Example 18] In Example 1, soybean paste was obtained in the same manner as in Example 1, except that the immersion time in water during the swelling process was 120 minutes. The swelling ratio of the soybeans was 1.8. The results of the sensory evaluation are shown in Table 6. (For the sake of comparison, the results of Example 1 are also shown again in Table 6.)

[0070] [Example 19] In Example 1, soybean paste was obtained in the same manner as in Example 1, except that the immersion time in water during the swelling process was 90 minutes. The swelling ratio of the soybeans was 1.7. The results of the sensory test are shown in Table 6.

[0071] [Comparative Example 7] In Example 1, soybean paste was obtained in the same manner as in Example 1, except that the immersion time in water during the swelling process was 60 minutes. The swelling ratio of the soybeans was 1.6. The results of the sensory test are shown in Table 6. As shown in Examples 1, 18, 19 and Comparative Example 7, when the swelling ratio of soybeans was 1.6 or less in the swelling process, only soybean paste with a strong astringent taste and poor aroma was obtained. By increasing the swelling ratio of soybeans to 1.7 or higher, and especially to 1.8 or higher, a soybean paste with a grassy taste and astringency, as well as good aroma and sweetness, was obtained.

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078] The soybean paste obtained by the method of the present invention has reduced grassy and astringent tastes, and is rich in aroma and sweetness. Therefore, it is useful as a food ingredient for bread, tofu-like foods, juices, sweets, soups, ice cream, sherbet, cheese, yogurt, and other foods.

Claims

[1] a) A swelling process in which raw soybeans are soaked in water at room temperature to obtain swollen soybeans, (b) A heating step in which the swollen soybeans obtained in step (a) above are heated to obtain heated soybeans, (h) A grinding step in which the heated soybeans obtained in step (b) above are wet-ground to obtain a soybean grinding product, A method for producing soybean paste containing, The above step (i) is a step to control the swelling ratio (weight of swollen soybeans / weight of raw soybeans) to 1.7 or more, and The above step (b) is a step of immersing the swollen soybeans in hot water at 80°C or higher but less than 90°C for a period of 13 minutes or more but less than 30 minutes. A method for producing soybean paste characterized by the above. [2] The method for producing soybean paste according to claim 1, wherein step (a) is a step of controlling the swelling ratio to a range of 1.8 to 2.

2. [3] The method for producing soybean paste according to claim 2, wherein step (b) is a step of soaking the swollen soybeans in hot water at 82°C or higher and 88°C or lower for a period of 15 minutes or more and 27 minutes or less. [4] The method for producing soybean paste according to claim 2, wherein step (b) is a step of soaking the swollen soybeans in hot water at 82°C or higher and less than 84°C for a period of 18 minutes or more and 25 minutes or less. [5] The method for producing soybean paste according to claim 2, wherein step (b) is a step of soaking the swollen soybeans in hot water at 84°C or higher and 86°C or lower for a period of 18 minutes or more and 27 minutes or less. [6] The method for producing soybean paste according to claim 2, wherein step (b) is a step of soaking the swollen soybeans in hot water at a temperature greater than 86°C and less than or equal to 88°C for a period of 18 minutes or more and less than or equal to 23 minutes. [7] A method for producing soybean paste according to any one of claims 1 to 6, further comprising the step of subsequently performing a retort sterilization treatment on the soybean grinding treatment obtained in step (c) above. [8] A soybean paste obtained by any of claims 1 to 7, characterized in that the n-hexanal content in a sample of the soybean paste with a solid content of 20% by weight is 0.05 μg / g or less, and the soy saponin-derived soy saponol A content is 120 μg / g or less. [9] The soy paste according to claim 8, wherein the n-hexanal content is 0.03 μg / g or less, and the soy saponin-derived soy saponin-derived soy saponol A content is 110 μg / g or less. [10] The soybean paste according to claim 9, wherein the soy sapogenol A content is 100 μg / g or less.