Filamentous fungus-fermented composition and method for producing the same

Abstract

To provide a filamentous fungus-fermented yeast protein-containing composition with mitigated off-flavor commonly referred to yeast odor, and a method for producing the same, as well as a method for mitigating off-flavor in yeast-derived protein materials.SOLUTION: Culturing filamentous fungi in a culture medium containing a suspended yeast-derived protein material makes it possible to impart an elegant aroma to the protein material, thereby reducing off-flavor derived from the protein material. Furthermore, heating the protein material after fermentation results in a protein composition exhibiting resilient properties.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a yeast protein composition having reduced off-flavors and a method for producing the same. [Background technology]

[0002] In recent years, as the demand for protein increases with the global population growth, there are concerns that the supply will be insufficient. For this reason, much research has been done with the aim of using protein materials derived from plants, microorganisms, insects, etc. as foods. Among them, microorganisms are expected to be a source of protein because they grow quickly, can grow with little nutrition, and are suitable for mass production. Among microorganisms, yeast is also expected to be a source of protein, but it has a unique odor known as yeast odor, which poses challenges in using it as a food. Methods reported for masking the unique odor caused by yeast in food systems include a flavor enhancer for chocolate products that contains yeast extract and 2-furanmethanol and / or 5-methyl-2-furanmethanol as active ingredients (Patent Document 1), and a method for masking the yeast odor by adding flavoring to a yeast extract-containing paste that is characterized by being composed of yeast extract powder, liquid oil and fat, and solid fat (Patent Document 2).

[0003] However, methods for masking the yeast odor by adding food additives or flavorings have tended to be avoided due to consumers' increasing preference for natural foods. Furthermore, no methods have yet been reported for improving the unique odor of yeast as a protein ingredient. For this reason, there has been a demand for a yeast-derived protein composition that satisfies consumer needs and has an improved unique odor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-175963 A [Patent Document 2] JP 2017-184625 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a yeast-derived protein composition that is improved in an off-flavor known as yeast odor, and a method for producing the same, and to provide a method for improving the off-flavor of a yeast-derived protein composition. [Means for solving the problem]

[0006] As a result of intensive research into solving the above-mentioned problems, the inventors discovered that when a filamentous fungus is cultured in a medium in which a yeast-derived protein material is suspended, the protein material is imparted with a gorgeous aroma and any off-flavors inherent to the protein material are suppressed, and further, that heating the fermented protein material gives it elastic physical properties, thereby completing the present invention.

[0007] That is, the present invention relates to the following first to sixth aspects. The first type is a composition containing yeast protein fermented by filamentous fungi, which uses as a culture medium a yeast protein material having a protein content of 40% by weight or more and a dietary fiber content of 4% by weight or more before fermentation by filamentous fungi, and which has the property of gelling upon heat treatment. The second is a method for producing the composition according to the first aspect, which comprises the step of culturing a filamentous fungus in a medium containing a protein material derived from yeast. Thirdly, there is provided a method for suppressing the off-flavor of a yeast-derived protein material, which comprises adding a yeast-derived protein material having a protein content of 40% by weight or more and a dietary fiber content of 4% by weight or more before fermentation by a filamentous fungus to a culture medium for the filamentous fungus and culturing the filamentous fungus. Fourthly, there is provided a method for improving the physical properties of a yeast-derived protein material, which comprises adding the yeast-derived protein material to a medium and culturing a filamentous fungus therein. Fifth, a food or drink comprising the fermentation composition described in the first aspect. Sixth, there is provided a method for producing the food or drink described in the fifth aspect. Effect of the Invention

[0008] According to the present invention, a yeast protein composition having a pleasant aroma and suppressed off-flavor derived from yeast can be obtained by suspending a yeast-derived protein material in a medium and culturing a filamentous fungus in the medium.Furthermore, by heating the yeast protein composition, it shows soft, elastic, jelly-like physical properties, and can be used as a protein source having water retention capacity, suppressing off-flavor derived from yeast and imparting a gorgeous aroma, in general foods and supplements, especially foods for people with difficulty swallowing, etc. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The protein composition of the present invention is made from a yeast-derived protein material and is a protein composition in which the off-flavor expressed as yeast odor is suppressed compared to the original yeast-derived protein material. The yeast odor in the present invention refers to the unique odor or off-flavor of the yeast itself, and the degree of this can be known by sensory evaluation.

[0010] The yeast from which the protein composition of the present invention is derived can be any yeast that is generally used in the production of food products such as beer, sake, bread, and seasonings, without any restrictions. Specific examples include budding yeast (Saccharomyces cerevisiae) and torula yeast (Siblindonella jadini; also known as Candida utilis). Among these, torula yeast is preferable.

[0011] The yeast-derived protein material in the present invention may be yeast cells after soluble extract components are separated and removed from the yeast cells. Alternatively, the yeast-derived protein material may be an insoluble fraction obtained by treating the yeast cells after soluble extract components are separated and removed with an enzyme having glucanase activity, and then removing the soluble fraction. The protein content of the insoluble fraction may be 40% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more, based on the solid content, as the total amino acid content measured by an amino acid analyzer according to a conventional method. Here, the enzyme having glucanase activity may be a commonly available enzyme preparation. The reaction conditions may be the optimal conditions for the enzyme used. The soluble fraction may be removed after the enzyme reaction by a general method such as centrifugation or filtration.

[0012] Moreover, the protein material preferably contains dietary fiber, more preferably 4% by weight or more, and even more preferably 4.5% by weight or more. The amount of dietary fiber can be determined by hydrolysis. Specifically, a sample is hydrolyzed with 1N sulfuric acid at 110°C for 3.5 hours, neutralized, and the resulting hydrolysates, mannose and glucose, are measured by high performance liquid chromatography (HPLC) and converted into glucan and mannan to determine the amount of dietary fiber. The HPLC analysis conditions may be general sugar analysis conditions as long as they allow the measurement of glucose and mannose.

[0013] The composition of the present invention can be produced by adding the above yeast-derived protein material to a medium for culturing a filamentous fungus. The amount of the yeast-derived protein material added to the medium for culturing a filamentous fungus can be 5 to 20% by weight, preferably 8 to 15% by weight, and more preferably 9 to 12% by weight.

[0014] As long as the effects of the present invention are not adversely affected, other components may be added to the medium, such as enzyme decomposition products of proteins, inorganic salts, sugars, vitamins, and minerals.

[0015] The composition of the present invention can be produced by adding the above yeast-derived protein material to a fluid medium for culturing filamentous fungi. The filamentous fungus used in the production of the composition of the present invention is not particularly limited as long as it is a filamentous fungus that is commonly used in the production of foods and beverages, and examples of such filamentous fungi include Aspergillus oryzae, Aspergillus kawachii, Aspergillus awamori, Aspergillus sojae, Aspergillus glaucus, Aspergillus tamari, Aspergillus luchuensis, Aspergillus nigar, Rhizopus oligosporus, Rhizopus oryzae, and Rhizopus stolonifer. Aspergillus oryzae is particularly preferred. Furthermore, one of the microorganisms listed above may be used alone, or a combination of two or more of them may be used.

[0016] The conditions for culturing the filamentous fungus are not particularly limited as long as the yeast odor of the yeast-derived protein material is suppressed, and the temperature, pH, culture time, aeration conditions, and the like generally adopted in culturing filamentous fungi can be appropriately set. For example, in the case of shaking culture, the fermentation temperature can be 20 to 40°C, preferably 25 to 35°C. The fermentation time can be 24 to 240 hours, preferably 72 to 168 hours. It is desirable to culture under aerobic conditions for aeration.

[0017] The filamentous fungal culture thus obtained is derived from yeast, but contains a protein composition that is endowed with a fruity, sweet and gorgeous aroma and has a suppressed yeast odor. Therefore, this culture can be used as the yeast protein composition of the present invention as it is. If necessary, excipients and the like may be added to the culture, and the culture may be concentrated and dried. The drying method may be a method generally used in food production, such as spray drying, drum drying, or freeze drying. The form is not particularly limited, and the culture may be prepared in the form of powder, granules, capsules, tablets, paste, or the like.

[0018] The composition of the present invention also has the property of gelling upon heating. By gelling upon heating, water retention and elasticity increase, and the composition exhibits bouncy and soft physical properties. Heating conditions may be at a temperature of 80°C or higher for 1 minute or more, and examples of such conditions include autoclaving using steam at 100°C or higher and retorting under pressurized heating conditions. The composition of the present invention that has been heat-treated gels, whereas the unheated composition does not gel and remains liquid, so that the change in physical properties due to heating can be judged by appearance.

[0019] The composition of the present invention may be eaten as it is, or may be added to general foods or supplements. It may also be mixed with a product whose physical properties have been changed by heat treatment, or may be added to food and the like and then heat-treated to change the physical properties of the food. The composition of the present invention may be added to food or drink in any manner, and may be added simultaneously with other ingredients, or may be added separately to produce food or drink. In addition, the heat-treated product of the composition of the present invention may be gelled and have increased binding properties, so that it can bind other food materials, and therefore it can also be added as a binding agent.

[0020] The method for suppressing the off-flavor of a yeast-derived protein material in the present invention is to ferment the yeast-derived protein material with a filamentous fungus. The method for fermentation with a filamentous fungus is as described above.

[0021] The method for improving the physical properties of a yeast-derived protein material in the present invention is to ferment the yeast-derived protein material with a filamentous fungus. The method for fermentation with a filamentous fungus is as described above. EXAMPLES

[0022] The present invention will be specifically described below using examples, but the present invention is not limited to these.

[0023] <Raw materials for the composition of the present invention> Among the protein materials derived from yeast, "KR Yeast" (Mitsubishi Corporation Life Sciences) was used as sample 1, which is the yeast cell after separating and removing soluble extract components from the yeast cell. The protein content of "KR Yeast" was analyzed as total amino acid content using an amino acid analyzer L8800 (Hitachi) according to standard methods, and was found to be 45% by weight. The dietary fiber content was analyzed by HPLC (column: SUGAR SP0810 (Shodex), detector: RI, mobile phase: ultrapure water) and was found to be 4.1% by weight. In addition, the torula yeast cells after separating and removing the soluble extract components were suspended in water at 10% by weight, and a commercially available glucanase preparation was added at 0.05% relative to the cells and allowed to act for 3 hours under optimal enzyme conditions, after which the soluble fraction was removed and the resulting insoluble fraction was dried to obtain Sample 2. The protein and dietary fiber amounts were analyzed using the same method as for Sample 1, and the protein content was 82% by weight and the dietary fiber content was 15.2% by weight.

[0024] <Production of the composition of the present invention> 10 g of sample 1 and 10 g of glucose were added to water to make 100 mL, and the mixture was heat sterilized to prepare a medium. Aspergillus oryzae was seeded in the medium and cultured with shaking under aerobic conditions at 30° C. for 6 days. The resulting culture solution was freeze-dried to obtain a powdered sample of Example 1. A similar procedure was carried out except that Rhizopus oligosporus was used as the seeding microorganism, to obtain a sample of Example 2. Moreover, the same procedure was carried out except that no microorganism was seeded, to obtain a sample of Comparative Example 1. Furthermore, as a sample of Control Example 1, "KR yeast" was used. In addition, 10 g of sample 2 and 10 g of glucose were added to water to make 100 mL, and the mixture was heat sterilized to prepare a medium. Aspergillus oryzae was seeded in the medium and cultured with shaking under aerobic conditions at 30° C. for 6 days. The resulting culture solution was freeze-dried to obtain a powdered sample of Example 3. A similar procedure was carried out except that Rhizopus oligosporus was used as the seeding microorganism, to obtain a sample of Example 4. Furthermore, a sample of Comparative Example 2 was obtained by carrying out the same procedure except that no microorganism was seeded.

[0025] <Confirmation test for yeast odor suppression by sensory evaluation> A panel of five people evaluated the odor of each of the powder samples of Examples 1 to 4 and Comparative Examples 1 and 2 on a seven-point scale: 1 point: very weak, 2 points: quite weak, 3 points: slightly weak, 4 points: same as the control example, 5 points: strong, 6 points: quite strong, and 7 points: very strong. As a result, the value of Example 1 was 6.6 points, which indicated that a fragrance was imparted compared to Control Example 1. The fragrance was also fruity. On the other hand, the value of Comparative Example 1 was 3.9 points, but this was a score due to yeast odor, and did not indicate that a gorgeous fragrance was imparted. Similarly, the value of Example 2 was 6.1 points, which revealed that a gorgeous fragrance was imparted. Moreover, the scores for Examples 3 and 4 were 6.8 and 5.8 points, respectively, and a gorgeous aroma was imparted, whereas the score for Comparative Example 2, which did not undergo the fermentation process using filamentous fungi, was 3.8 points, and a slightly stuffy odor was observed.

[0026] <Evaluation of physical properties> In the process of obtaining the sample of Example 1 and the sample of Comparative Example 1, each culture solution was heated at 121°C for 20 minutes without being freeze-dried, and a portion of the heated sample was scooped out and its physical properties were visually confirmed. As a result, the culture solution seeded with Aspergillus oryzae was found to have a soft, bouncy elasticity like chawanmushi (savory egg custard), and was confirmed to have physical properties that made it easy to swallow, while the culture solution not seeded with Aspergillus oryzae remained liquid even when heated. Furthermore, when the culture solutions obtained in the steps of producing the samples of Examples 2 to 4 were subjected to a heat treatment, it was confirmed that they had gelling ability.

[0027] From the above, it was shown that a yeast-derived protein composition with a suppressed yeast odor can be obtained by fermenting a yeast-derived protein material with a filamentous fungus. It was also shown that the gelling ability of this yeast-derived protein composition is a property imparted by fermentation with a filamentous fungus.

Claims

1. A composition containing filamentous fungus-fermented yeast protein, which uses as a medium a protein material derived from yeast having a protein mass of 40% by weight or more and a dietary fiber content of 4% by weight or more before fermentation by filamentous fungus, and which has the property of gelling when heated.

2. A method for producing the composition according to claim 1, comprising the step of culturing a filamentous fungus in a medium containing a protein material derived from yeast.

3. The method for suppressing the off-flavor of a yeast-derived protein material is characterized in that a yeast-derived protein material having a protein mass of 40% by weight or more and a dietary fiber mass of 4% by weight or more before fermentation by a filamentous fungus is added to a culture medium for the filamentous fungus, and the filamentous fungus is cultivated.

4. A method for improving the physical properties of a yeast-derived protein material, comprising adding the yeast-derived protein material to a medium and culturing a filamentous fungus.

5. A food or drink comprising the fermented composition according to claim 1.

6. A method for producing the food or beverage according to claim 5.