Food property improving agent comprising a composition coated with dextran

Abstract

According to the present invention, a food property improver containing a dextran-coated material exhibits a food property improving effect equivalent to dextran having a molecular weight of at least 150,000 Da. Also, since the outer peripheral portion of the dextran-coated material is coated with dextran having a molecular weight of at least 7,000 Da, a high-molecular dextran, wheat flour, or the like in the food property improver does not precipitate or separate even when stored for a long time. Thus, the food property improver can be used in a uniform state even without turning over and mixing. Furthermore, a food property improver according to the present invention includes dextran having a maximum molecular weight of 105 Da, but exhibits, due to said composition, the physical property improving effect equivalent to that achieved when dextran having a molecular weight 105 Da is added.

Description

[Technical field]

[0001] The present invention relates to a composition in which food particles are coated with dextran and a food property improver containing the same. [Background technology]

[0002] Dextran is a type of exopolysaccharide produced by lactic acid bacteria, and is a homopolysaccharide in which glucose is linked by α-1,6 bonds. Refined products are used in the fields of medicine, industrial products, cosmetics, food, etc., depending on the purity and molecular weight. In the food field, it is classified as a thickening polysaccharide, an existing food additive, under the Japanese Food Sanitation Act. According to the Food Sanitation Act, the lactic acid bacteria that can be used for the production of dextran are limited to Leuconostoc mesenteroides and Streptococcus equinus. However, lactic acid bacteria that produce dextran (hereinafter abbreviated as dextran-producing bacteria) are not limited to the above-mentioned species, but are isolated from various fermented foods, and Weissella confusa, Leuconostoc lactis, etc. are known (Non-Patent Document 1). In addition to the linear structure consisting of α-1,6 bonds, dextran's molecular structure also includes branches such as α-1,2, α-1,3, and α-1,4 bonds, and there are various patterns, but all of them exhibit water retention by binding to water with the -OH group facing outward from the molecule. Therefore, in the food industry, it has been reported that the higher the molecular weight, the higher the water retention effect when added to food (Non-Patent Document 2, Patent Document 1). Regarding the molecular weight of dextran, there is no clear distinction or definition between high molecular weight and low molecular weight, but a comparison of many previous documents reveals that a molecular weight of 10 5 Da or more is considered a polymer, and 10 4 Molecular weights below Da tend to be treated as small molecules.

[0003] For example, Patent Document 1 discloses that high molecular weight dextran is more effective than low molecular weight dextran in improving the softness, moistness, and anti-aging properties of bread. Similarly, Non-Patent Document 2 discloses that a fermentation starter containing a high molecular weight dextran with a molecular weight of 2000 kDa (2 million Da) exhibits the same additive effect as Patent Document 1. On the other hand, Patent Document 2 also points out that while high molecular weight dextran with a molecular weight of more than 200,000 Da improves the softness of bread when added to it, it also makes the texture chewy and makes it difficult to bite through, adversely affecting the physical properties of the bread dough.

[0004] In Patent Document 2, the leaven is required to improve the softness, moistness, and melt-in-the-mouth quality of bread without affecting the bread-making properties. Therefore, even in the case of products containing dextran as a main component, the improvement of the crispness of bread and the workability of bread dough remain as issues. In addition, the above-mentioned leaven is often liquid or semi-liquid in nature, and often undergoes solid-liquid separation when stored stationary. This is because the dextran, which has a large molecular weight, contained in the leaven and the substrate such as wheat flour precipitate, and once separated, the leaven and other products are difficult to mix completely even if they are inverted and mixed before use. If the solid-liquid separated leaven is used without being mixed sufficiently, there is a possibility that lot differences will occur in the final bread product. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 2119871 [Patent Document 2] Patent No. 6282875 [Non-patent literature]

[0006] [Non-Patent Document 1] Pepe, O., Ventorino, V., Cavella, S., Fagnano, M., Brugno, R., : Prebiotic content of bread prepared with flour from immature wheat grain and selected dextran-producing lactic acid bacteria. Applied Environmental Microbiology.,2013 Jun;79(12):3779-3785. [Non-Patent Document 2] Zhang, Y., Guo, L., Xu, D., Li, D., Yang, N., Chen, F., Jin, Z., Xu, : Effects of dextran with different molecular weights on the quality of wheat sourdough breads., Food Chemistry., 2018 Aug 1;256:373-379 [Non-Patent Document 3] Michio Ozaki, Yasushi Uchimura, Sanae Okada, "Lactic Acid Bacteria Experiment Manual: From Isolation to Identification", Asakura Publishing Co., Ltd., 1992 [Non-Patent Document 4] Atsuya Harada, Akira Misaki, "Comprehensive Polysaccharide Science (Part 2)", Kodansha, 1974 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem that the present invention aims to solve is to provide a food property improver which does not affect bread-making properties, has a property improving effect equal to or greater than that of high molecular weight dextran, and is homogeneous even when stored for a long period of time without undergoing solid-liquid separation. [Means for solving the problem]

[0008] As a result of extensive research into solving the above-mentioned problems, the inventors have discovered that the above-mentioned problems can be solved by using food particles whose outer periphery is coated with dextran having a molecular weight of 7,000 Da or less in combination with dextran having a molecular weight of 150,000 Da or more.

[0009] That is, the present invention provides: (1) Food particles whose outer periphery is partially or entirely covered with dextran having a molecular weight of 7,000 Da or less. (2) A food property improver containing dextran having a molecular weight of 150,000 Da or more and the food particles described in (1). (3) The food property improver according to (2) above, wherein the food particles are one or more of grain flour, seed flour, and vegetable flour. (4) A dough composition for heat-processed foods, comprising the food property improver of (2) or (3). (5) A heat-processed food obtained by baking the composition described in (4). (6) A method for improving the physical properties of heat-processed foods, comprising incorporating 0.5 to 20% by weight of the food property improver according to (2) or (3). Effect of the Invention

[0010] The dextran in the food property improver of the present invention binds with water, thereby increasing the water retention of the food and improving its physical properties. For example, in the case of bread, which is a heat-processed food, the addition of dextran with high water retention can improve the physical properties of the bread, such as improving its softness, moistness, and melting in the mouth, and suppressing starch aging. In addition, the food property improver is unlikely to cause precipitation of high molecular weight dextran or food particles even when stored stationary for a long period of time, that is, it is unlikely to separate into solid and liquid, so it can be used in a uniform state without inverting and mixing before use. [Brief description of the drawings]

[0011] [Figure 1] Molecular weight distribution of the low molecular weight region of dextran contained in the experiment area 1 [Diagram 2]Molecular weight distribution of the low molecular weight region of dextran contained in comparison group 1 [Diagram 3] Molecular weight distribution of the high molecular weight region of dextran contained in the experiment area 1 [Figure 4] Molecular weight distribution of the high molecular weight region of dextran contained in comparison group 1 [Diagram 5] Starch granules in area 1 measured by a Raman microscope [Figure 6] Low molecular weight dextran coating starch granules in area 1 as determined by a Raman microspectrometer [Figure 7] Appearance of test area 1 and comparison area 1 after centrifugation [Figure 8] Measurement results of the staling degree of sponge bread DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described in detail below. The food property improver of the present invention is a composition containing food particles whose outer periphery is partially or entirely covered with dextran having a molecular weight of 7000 Da or less, and dextran having a molecular weight of 150,000 Da or more. If the molecular weight of the dextran contained in the food property improver is greater than 7000 Da but less than 150,000 Da, the property improving effect when added to food is reduced and the agent is more likely to undergo solid-liquid separation during storage, so the molecular weight is preferably distributed between 7000 Da or less and 150,000 Da or more. The dextran used in the present invention is no different from known dextrans except that its molecular weight is within the above-mentioned range. Specifically, it may be a polysaccharide having glucose as its constituent sugar, a main chain formed by α-1,6 bonds, and some α-1,2 bonds, α-1,3 bonds, or α-1,4 bonds, and having a branched structure. In the present invention, the molecular weight of dextran is expressed as an average molecular weight, and the value calculated from the peak top molecular weight (Mp) is used.

[0013] The dextran used in the present invention may be of any origin or preparation method, such as commercially available purified dextran, dextran prepared by fermentation, enzymatic or acid hydrolysis, etc. Examples of dextran prepared by fermentation include dextran produced from sucrose as a precursor by dextransucrase produced by lactic acid bacteria, and dextran produced from a partial starch hydrolysate as a precursor by dextrin dextranase produced by Gluconobacter bacteria.

[0014] When lactic acid bacteria are made to produce dextran, the lactic acid bacteria (hereinafter also referred to as dextran-producing lactic acid bacteria) are preferably lactic acid bacteria that produce dextran from sucrose outside the bacterial cell, such as Streptococcus, Leuconostoc, Weissella, and Lactobacillus. As dextran-producing lactic acid bacteria, a commercially available lactic acid bacteria starter may be used, or it may be obtained from a culture collection institution and used, or it may be isolated from various fermented foods and used. When isolating dextran-producing lactic acid bacteria from fermented foods, screening is performed using a selective medium for lactic acid bacteria and a sucrose medium described in Non-Patent Document 3.

[0015] In the present invention, food particles whose outer periphery is partially or entirely coated with dextran having a molecular weight of 7000 Da or less (hereinafter also referred to as dextran-coated material of the present invention) refer to a single entity or multiple such entities, or a substance containing these, which has a structure in which a granular structure contained in a food material is used as a core material, and the outer periphery of the core material is partially or entirely coated with dextran having a molecular weight of 7000 Da or less. The food material used as the core material is preferably one or more selected from grain flour, seed flour, or vegetable flour, or starch, gluten, gliadin, or glutenin derived from these food materials. When dextran-producing lactic acid bacteria are made to produce dextran, as described below, it is preferable to select a food material that the dextran-producing lactic acid bacteria can assimilate as a fermentation substrate for the core material.

[0016] The flour used as the core material may be endosperm of a grain or flour prepared by grinding the endosperm with the germ and / or skin attached. Examples of grains include wheat, rice (non-glutinous rice, glutinous rice), barley, rye, corn, foxtail millet, barnyard millet, and pearl barley, while examples of grain flour include wheat flour (e.g., strong flour, semi-strong flour, medium-strength flour, weak flour, whole wheat flour, etc.), rice flour (joshinko, joyo flour, mochi flour, shiratama flour, brown rice flour, etc.), barley flour, rye flour (whole rye flour or peeled rye finely ground, medium ground, coarsely ground, or stone-ground), corn flour, foxtail millet flour, barnyard millet flour, pearl barnyard millet flour, and pearl barley flour.

[0017] The seed flour used as the core material may be a starchy plant seed other than a grain, the endosperm of the plant seed, or a flour prepared by grinding the endosperm with the germ and / or epidermis attached. Examples of plant seeds include soybean and buckwheat seeds, and examples of flour (seed flour) prepared by grinding the endosperm of these seeds or the endosperm with the germ and / or epidermis attached include soybean flour and buckwheat flour.

[0018] The vegetable powder used as the core material may be a starchy vegetable or a powder of the starchy vegetable. Examples of starchy vegetables include potatoes, sweet potatoes, and other tubers, and vegetables such as bracken. Examples of such vegetables powdered (vegetable powder) include powdered potato and bracken powder.

[0019] Starches used as the core material include starch extracted from plants other than the above-mentioned grains, starch-containing plant seeds other than grains, and starch-containing vegetables, and examples of such starches include corn starch, mung bean starch, potato starch, and kudzu starch.

[0020] The starch also includes processed starch (functional starch obtained by subjecting natural starch to physical or chemical treatment). Examples of such processed starch include acetylated adipate cross-linked starch, acetylated phosphate cross-linked starch, acetylated oxidized starch, sodium octenyl succinate starch, starch acetate, oxidized starch, hydroxypropyl starch, hydroxypropyl phosphate cross-linked starch, phosphate monoesterified phosphate cross-linked starch, phosphorylated starch, phosphate cross-linked starch, unmodified pregelatinized starch, modified pregelatinized starch, etc., which are processed using potato starch, corn starch, tapioca starch, wheat starch, etc. as raw starch.

[0021] These starches may be used alone or in combination of two or more. Preferably, the starch is derived from at least one selected from the group consisting of cereal flour, seed flour, vegetable flour, and starch (including modified starch). More preferably, the starch is derived from at least one selected from the group consisting of cereal flour, seed flour, and starch (including modified starch), even more preferably, the starch is derived from at least one selected from the group consisting of cereal flour and starch (including modified starch), and particularly preferably, the starch is derived from cereal flour. The cereal flour is preferably wheat flour, and the wheat flour can be used in combination with at least one selected from other starchy raw materials, such as rice flour, rye flour, corn flour, potato starch, and modified starch.

[0022] In the present invention, a method for coating a part or all of the outer periphery of a food particle serving as a core material with dextran having a molecular weight of 7000 Da or less includes dispersing dextran having a molecular weight of 7000 Da or less and the food particle serving as the core material in an appropriate aqueous medium such as water and stirring to prepare the food. Specifically, the food can be prepared by using dextran having a molecular weight of 7000 Da or less and the food particle serving as the core material as raw materials and subjecting it to a granulation method usually performed in the food industry. Examples of the granulation method include a granulation method using a fluidized bed granulator, a granulation method using an agitation type fluidized bed granulator equipped with an agitation blade attached to a fluidized bed granulator, a granulation method using a rolling type fluidized bed granulator equipped with a rolling plate, a granulation method using a fluidized bed granulator such as a Wurster type fluidized bed coating machine, a granulation method using an agitation type granulator in which powder is agitated and a binder is added thereto to form granules, and a granulation method using an extrusion granulator in which powder is extruded together with a binder at high pressure. In the present invention, "a part of the outer periphery of the food particle is covered" refers to a state in which at least 30% or more, and preferably 50% or more, of the surface area of ​​the food particle is covered with dextran. The dextran having a molecular weight of 7000 Da or less used to coat food particles can be prepared by subjecting dextran having a higher average molecular weight, or a component thereof, to a method capable of decomposing dextran, such as decomposition with dextranase or acid hydrolysis with hydrochloric acid. The obtained dextran-coated material of the present invention can be mixed with dextran having a molecular weight of 150,000 Da or more to form a mixture, which can be used in the preparation of the food property improver of the present invention. In addition to the above, the food property improver of the present invention can also be prepared directly by stirring the culture of dextran-producing lactic acid bacteria or under conditions in which low molecular weight dextran is produced from high molecular weight dextran by a dextran-degrading enzyme.

[0023] Hereinafter, an example will be given of a method for directly preparing the food property improving agent of the present invention by fermentation using dextran-producing lactic acid bacteria.

[0024] When preparing a dextran-coated material and a food property improver by fermentation, the following three raw materials are used. The first is wheat flour, potato starch, rice flour, or gliadin, which is a fermentation substrate and serves as the core material of the dextran-coated material. The second is sucrose, which is a precursor of dextran and serves as a primer for dextran production. The third is a preculture solution of dextran-producing lactic acid bacteria. All ingredients except the preculture solution of dextran-producing lactic acid bacteria are mixed with water in advance to prepare a medium for dextran production. The amount of each raw material used is such that, as a percentage of the final composition, wheat flour, potato starch, rice flour, or gliadin is 10 to 50% by weight, preferably 20 to 40% by weight, sucrose is 5 to 30% by weight, preferably 10 to 25% by weight, and water is 35 to 75% by weight, preferably 45 to 70% by weight, more preferably 25 to 35% by weight. Separately, a preculture solution is prepared by culturing dextran-producing lactic acid bacteria under culture conditions suitable for the lactic acid bacteria, and the preculture solution is added to the dextran-producing medium. The amount of the preculture solution to be added to the dextran-producing medium varies depending on the amount of bacteria in the preculture solution, but is usually 5 to 10 parts by weight per 100 parts by weight of the dextran-producing medium. These ingredients are mixed in a suitable container, the pH is adjusted to around 7 as necessary, and the mixture is cultured at 25 to 35°C for 24 to 48 hours. The culture may be a static culture, but it is preferable to stir the medium continuously or intermittently at a rotation speed that does not cause the food particles contained in the medium to settle. This is to make it easier for the dextran produced during the culture to coat the food particles in a state of a molecular weight of 7000 Da or less. The molecular weight of dextran can be evaluated by qualitative analysis using gel filtration chromatography, and a Raman microscope can be used to observe the state of coating with dextran.

[0025] The dextran-coated product or food property improver of the present invention may be used in any one of liquid, paste, dough, or powder form, and the form is not limited. When the dextran-coated product or food property improver of the present invention is powdered, the method of drying and powdering can be appropriately selected according to its characteristics and properties. For example, it can be powdered by any method such as spray drying method, freeze drying method, or drum drying method.

[0026] The method of adding the food property improver of the present invention to food is not particularly limited. For example, it may be added as a part of the raw material when producing food, or it may be added after mixing with other raw materials. The timing of addition is not particularly limited, and it is preferably added before or during mixing of the raw materials in terms of easy preparation into food. The food to which the food property improver of the present invention is added is not particularly limited. For example, dough of heat-processed foods such as bread and baked confectionery can be mentioned. The dough to which the food property improver of the present invention is added can be baked according to the normal baking conditions of each heat-processed food to produce a baked food. The obtained heat-processed food is excellent in moistness, softness, and melt-in-the-mouth feel. Furthermore, by appropriately changing the food material to be the core material, it may be added to noodles such as Chinese noodles and udon, and cooked rice, and each food can be processed according to the normal heating conditions. Therefore, the food property improver of the present invention can be suitably used as an agent for improving the texture of food, and the use of the food property improver of the present invention in food can be cited as a method for improving the physical properties of food. The food property improver of the present invention can be used in combination with the raw materials described below as long as the additive effect of the improver is not impaired. Examples of food additives or food materials that can be used in combination with the improving agent include monoglycerin fatty acid esters, calcium stearoyl lactylate, sodium stearoyl lactylate, wheat gluten, corn starch, modified dextrin, xylanase, wheat starch, dextrin, processed fats and oils, hardened palm oil, sucrose fatty acid esters, sorbitan fatty acid esters, diacetyl tartaric acid monoglyceride, propylene glycol, guar gum, tricalcium phosphate, α-amylase, β-amylase, glucose oxidase, hemicellulase, protease, potato starch, corn starch, salt, vitamin E, L-ascorbic acid, vitamin C, carotene pigments, lecithin, enzymatically decomposed lecithin, sodium caseinate, D-sorbitol, yeast extract, cystine, dietary fiber, brewed vinegar, isomerized liquid sugar, lipase, and phospholipase. EXAMPLES

[0027] The present invention will be specifically described below using examples and comparative examples. The present invention is not limited to these. EXAMPLES

[0028] Preparation of food property improvers [the purpose] A food property improver for use in the present invention was prepared. [method] The food particles that serve as the core material for the dextran coating were made from starch contained in wheat flour, and a food property improver was produced by fermentation using dextran-producing bacteria. Since the viscosity of wheat flour varies depending on the quality and standard value, the amount was set so that the viscosity before fermentation would be 100 cp or less using a B-type viscometer. The same amount of sucrose as the wheat flour was weighed out in a stainless steel beaker and dissolved in 2.6 times the amount of water as the wheat flour. The wheat flour was mixed into the sucrose solution and a separately prepared Weissella ConfuseATCC14434 (hereinafter abbreviated as ATCC14434) culture solution was added. The mixed wheat flour dough was adjusted to pH 7.0 with sodium bicarbonate and cultured at 30°C for 24 to 48 hours with stirring. The fermentation time was until the pH reached 4.0 or less, and the stirring speed was set so that the wheat flour did not settle. EXAMPLES

[0029] Molecular weight distribution measurement [the purpose] The food property improver of the present invention was designated as Experimental Area 1, and the molecular weight distribution of the dextran contained in the improver was examined. In Comparative Area 1, the molecular weight distribution of wheat flour fermentation liquid was examined, which has the same property improving effect when added to bread, but which causes precipitation of high molecular weight dextran and food particles and solid-liquid separation when stored for a long period of time. [method] Dextran contained in the analytical sample was extracted and subjected to gel filtration chromatography. (Dextran extraction) The analytical samples were shaken and mixed homogenously before weighing. 2 g of each of the experimental group 1 and the comparative group 1 were weighed into a 50 mL centrifuge tube, and 8 mL of distilled water was added to dilute the samples 10-fold, followed by centrifugation (10°C, 2300 rpm, 10 min). Ethanol was added to the resulting centrifugal supernatant to a final concentration of 85% or more, and the mixture was further centrifuged (15°C, 3000 rpm, 30 min) to obtain a centrifugal precipitate. The centrifugal precipitate was dried at room temperature for 2 days to remove the ethanol, and then vacuum-dried in a vacuum desiccator for 5 hours. The dried centrifugal precipitate was used as crude polysaccharide. (Dextran purification) The resulting crude polysaccharides were purified by anion exchange chromatography under the following analytical conditions. Carrier: ECTEOLA-cellulose (Cl - Mold, Wako Pure Chemical Industries, Ltd.) Column size: 2.6 x 30 cm Flow rate; 0.7 ml / min Dissolution medium: water Fraction: 7.0 ml / fraction Detection: Phenol-sulfuric acid method Total number of pieces: 80 (Phenol-sulfuric acid method) After adding 0.5 mL of 5% phenol aqueous solution to 0.5 mL of the sample solution, 2.5 mL of concentrated sulfuric acid was added dropwise directly onto the liquid surface. After leaving the mixture at room temperature for 20 minutes, the absorbance was measured at 490 nm. (Molecular weight analysis of dextran by gel filtration chromatography for small molecules) Gel chromatography was carried out according to the following analytical conditions: Column XK 26 / 100 (GE Healthcare) Carrier: Sephadex G-100 (GE Healthcare) Size: 2.6×90 cm Flow rate 0.50ml / min Solvent 1 M NaCl Injection volume 1.0 ml Fraction 7.0 ml / fraction Detection Phenol-sulfuric acid method In addition, dextran with molecular weights of 25,000 (Funakoshi Co., Ltd.), 40,000 (Funakoshi Co., Ltd.), and 75,000 (CarboMer, Inc.) and Blue Dextran were used as molecular weight standard curve substances when creating the molecular weight calibration curve. (Molecular weight analysis of dextran by polymer gel filtration chromatography) Gel chromatography was carried out according to the following analytical conditions: Column XK 26 / 100 (GE Healthcare) Carrier: Sephacryl S-400 HR (GE Healthcare) Size: 2.6×80 cm Flow rate 0.60ml / min Solvent 1M NaCl Injection volume 1.0 ml Fraction 7.0 ml / fraction Detection Phenol-sulfuric acid method In addition, dextrans with molecular weights of 150 kDa (Funakoshi Co., Ltd.), 75 kDa (CarboMer, Inc.), and 10 kDa (Funakoshi Co., Ltd.) were used as molecular weight standard curve substances when creating the molecular weight calibration curve. [result] The results of molecular weight analysis of dextran by low molecular weight gel filtration chromatography are shown in Figures 1 and 2. Figure 1 shows the chromatograph of experimental area 1, and Figure 2 shows the results of comparative area 1. Dextran was detected in the fraction with a retention volume of 200 to 500 mL. From the peak apex, the approximate molecular weight of dextran detected in both test areas was estimated. It was about 2700 Da in experimental area 1 and about 8300 Da in comparative area 1, and a large molecular weight peak was confirmed in the low molecular weight region in comparative area 1. When the peak areas in the low molecular weight region were compared, the peak area in experimental area 1 was clearly larger than that in comparative area 1, indicating that experimental area 1 contains a large amount of low molecular weight dextran. The results of molecular weight analysis of dextran by polymer gel filtration chromatography are shown in Figures 3 and 4. Figure 3 shows the chromatograph of Experimental Area 1, and Figure 4 shows the results of Comparison Area 1. In Experimental Area 1, there was a slight peak at the void volume, suggesting the presence of dextran with a larger molecular weight. The retention volume peak was larger in Comparison Area 1 than in Experimental Area 1, at approximately 270 kDa and approximately 190 kDa, respectively. From the above, it was shown that in the experimental area 1, dextran molecules were distributed in the area around the molecular weight of 2700 Da and the area around the molecular weight of 190 kDa, and that it contained a larger amount of low molecular weight dextran than the comparative area 1. On the other hand, the comparative area 1 contained a large amount of dextran with a molecular weight of 270 kDa, and almost no low molecular weight dextran was found. From the above results, the food property improving agent of the present invention is composed of low molecular weight dextran having a molecular weight of 7000 Da or less and low molecular weight dextran having a molecular weight of 10 Da or less, as shown in FIG. 1 and FIG. 2. 6 It was shown to contain a polymer of 1 Da. EXAMPLES

[0030] Structural Observation of Dextran Coating [the purpose] In the present invention, the appearance of dextran coating in which food particles are coated with low molecular weight dextran was investigated. A non-destructive analytical device, a Raman microscope (Renishaw Ltd.), was used to observe the crystal structures of starch granules and dextran in the food property improver in Experimental Area 1. [method] Equipment: inVia Reflex (Renishaw Ltd.) The measurement conditions were as follows. Laser wavelength: 785nm Measurement magnification: 50x Measurement range: 100 x 200um Measurement interval: Step 1.2um Data processing: Principal Component Analysis (PCA) [result] The Raman microscope can depict the cross-section of a microscopic object of several μm in size, and different substances can be color-coded according to the difference in the spectrum. Raman images of starch and dextran contained in the experimental area 1 are shown in Figures 5 and 6. Figure 5 depicts the starch granules contained in the food property improver in the experimental area 1. Starch granules are shown to be scattered in the areas filled in white to light gray. Figure 6 depicts the dextran contained in the experimental area 1. The areas filled in white are dextran, and when superimposed on the starch granules in Figure 5, it is shown that dextran is present to cover the starch granules. Furthermore, since the lactic acid bacteria used in the present invention have the characteristic of producing high molecular weight dextran outside the bacterial cell, dextran should be present to fill the gaps between the starch granules, but the dextran on the surface of the starch granules is captured with a spectrum different from that of the areas that fill the gaps. These findings suggest that starch granules are not embedded in high molecular weight dextran, but that the outer periphery of the starch granules is coated with low molecular weight dextran. EXAMPLES

[0031] Examination of conditions for solid-liquid separation [the purpose] In the test area 1, solid-liquid separation did not occur even after long-term storage, but solid-liquid separation occurred in a short period of time in the comparison area 1. The conditions under which solid-liquid separation occurs were expressed in terms of centrifugal force and compared. [method] 3 g of sample was weighed into a 15 mL centrifuge tube and centrifuged at 3000 G for 10 minutes, and the properties were compared. [result] The properties of experimental area 1 and comparative area 1 after centrifugation are shown in Figure 7. Comparative area 1 is shown on the left, and experimental area 1 on the right. As Figure 7 shows, by centrifuging at 3000G for 10 minutes, comparative area 1 separated into a wheat starch layer and a slightly more viscous layer at the bottom where dextran and water were mixed, and solid-liquid separation occurred from the bottom to the top of the centrifuge tube in the order of wheat starch, dextran, water, and aqueous solvent. Experimental area 1 did not appear to separate and remained homogeneous. EXAMPLES

[0032] Effective as a food property improver [the purpose] The effect of adding the food property improving agent obtained in Example 1 was evaluated using sponge dough bread. The evaluation items included bread making evaluation, sensory evaluation, and staling degree measurement. [method] (Preparation of test samples) For the comparison plot for experimental plot 1, 7 g of dextran reagent was added to 93 g of wheat flour fermentation liquid not containing dextran, and the mixture was stored in a refrigerator for a certain period of time to homogenize (4°C, several hours to half a day). The dextran concentration in the comparison plot was determined based on the information in Non-Patent Document 4, which states that the amount of dextran contained in experimental plot 1 is estimated to be 7% when the dextran production efficiency is set to 38% based on sugar yield. Three types of dextran reagents with different molecular weights, as shown in Table 1, were used. [Table 1] (Making bread using the sponge method) The ingredients and process for making sponge bread are shown in Tables 2 and 3, respectively. [Table 2] [Table 3] The ratio of sponge in the sponge method was 70% sponge. For the sponge dough, strong flour, yeast food, yeast, and water were weighed, mixed and kneaded in a vertical mixer, and fermented in an incubator at 28°C for 4 hours. For the main dough, the sponge dough after fermentation, granulated sugar, salt, skim milk powder, and water were mixed in a vertical mixer, and shortening was added and kneaded again. The food property improver and dextran of the present invention were mixed with the raw materials (except shortening) used in the main dough. After 20 minutes of floor time, the dough after mixing was divided into 220g portions, rested for 20 minutes on the bench, molded with a molder, and molded into 1.5 loaf loaf molds. The molded dough was subjected to secondary fermentation for about 50 minutes in a proofer kept at a temperature of 38°C and humidity of 85%, and baked in a reel oven at 200°C for 30 minutes. After baking, the bread was cooled at room temperature on a rack and then bagged after 90 minutes. (Sensory evaluation) Sensory evaluation was performed on samples that had been baked one day after baking (hereafter referred to as D1) using a 7-point rating system. The sponge bread of comparison group 2 was given a standard score of 4 points for the evaluation items listed below, and comparison group 1, comparison group 3, and comparison group 5 were compared and evaluated. The sensory evaluation items were "hardness," "moistness," and "melt in the mouth," and were performed by a trained panel of eight people. These sensory evaluation items were scored according to the criteria shown in Table 4. [Table 4] (Aging degree measurement) The degree of staling of bread was evaluated by measuring the softness of the crumb at D1 and D3. The D1 bread, which had been stored in a bag at room temperature, was sliced ​​to a thickness of 1.8 cm using a slicer (HARD 70V single slicer, Hakura Seiki Co., Ltd., Tokyo), and the compressive stress of the crumb was measured using a texture analyzer (measuring device: EZ Test, measurement and analysis software: TRAPEZIUM, both from Shimadzu Corporation) (analysis conditions: 1.8 cm, 30% compressive stress, 10 times, ver. xmez). The same measurement was also performed on the D3 bread, and the staling from D1 to D3 was investigated. [result] The sensory evaluation results for sponge dough bread D1 are shown in Table 5. When the wheat flour fermentation liquid not containing dextran was compared with comparison group 2, the addition of the liquid had a greater effect on softness and moistness in experimental group 1 and comparison group 5. The addition of the liquid to experimental group 1, comparison group 3, and comparison group 4 had a greater effect on melting in the mouth. The results of the aging measurement are shown in Figure 8. The steeper the slope of the graph for the aging degree from D1 to D3, the greater the aging, and the shallower the slope, the more aging is suppressed. When there is a difference of ±0.2 or more in the slope between the test sections being compared, it is said that there is a difference in the aging suppression effect. Compared to the other test sections, the slope of test section 1 is shallower, indicating that it has a high aging suppression effect. From the above, it was shown that the effect of improving the texture one day after baking in the experimental group 1 was high, improving the softness and moistness, and slightly improving the melt-in-the-mouth feeling. It was also shown that the experimental group 1 had a high effect of suppressing aging from the first to third day after baking. [Table 5] [Industrial Applicability]

[0033] As explained above, the food property improver of the present invention contains not only dextran with a molecular weight of 150,000 Da or more (high molecular weight dextran), but also dextran with a molecular weight of 7,000 Da or less (low molecular weight dextran), and the low molecular weight dextran forms a dextran coating that coats the food particles contained in the agent. The dextran coating suppresses solid-liquid separation that occurs during static storage, which has not been solved until now, and when added to various foods, it shows a property improving effect that is consistent with lot-to-lot differences. Furthermore, the food property improver of the present invention contains dextran with a maximum molecular weight of 10 5 The dextran contains 10 Da of molecular weight. 6It shows the same physical property improving effect as when dextran of 1 Da is added. In addition, potato starch, rice flour, gliadin, etc. have been examined as food particles that serve as the core material, and it has been confirmed that food property improving agents equivalent to wheat flour can be obtained. This makes it possible to expand not only to bread, but also to gluten-free confectionery, bread, cooked rice, etc., and to suppress the deterioration of quality caused by starch aging. Furthermore, it is thought that it can be offered as a candidate material to replace not only starch aging, but also foods that use thickening polysaccharides to adjust the water retention effect.

Claims

1. A physical property improver for heat-processed foods obtained from food particles whose outer periphery is partially or entirely covered with dextran having a molecular weight of 7,000 Da or less and cereal flour containing dextran having a molecular weight of 150,000 Da or more, obtained by the following step 1 or 2; Step 1: A step of adding dextran-producing lactic acid bacteria to a dextran-producing medium and then culturing the medium with stirring at a rotation speed at which food particles contained in the medium do not settle. Step 2: A step of stirring under conditions in which dextran is decomposed by enzymatic or acid hydrolysis to produce low molecular weight dextran from high molecular weight dextran.

2. 2. The physical property improver for heat-processed foods obtained from cereal flour according to claim 1, wherein the food particles are one or more of cereal flour, seed flour, and vegetable flour.

3. A dough composition for heat-processed foods obtained from cereal flour containing the food property improver according to claim 1 or 2.

4. A heat-processed food obtained from flour obtained by baking the composition according to claim 3.

5. 3. A method for improving the physical properties of baked foods obtained from cereal flour, comprising incorporating 0.5 to 20% by weight of the physical property improver according to claim 1 or 2.

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