A high-purity naked oat beta-glucan and its preparation method and application

Abstract

The present invention belongs to the technical field of food additives, and specifically discloses a high-purity naked oat β-glucan and a preparation method and application thereof. The high-purity naked oat β-glucan is extracted by enzyme-assisted water extraction and alcohol precipitation, and the extract has the function of maintaining moisture stability in cereal products and improving water holding capacity. The high-purity naked oat β-glucan extraction of the present invention is obtained by pretreatment, hot water extraction, enzyme-assisted removal of starch and protein, freeze drying to obtain crude polysaccharides, and crude polysaccharide purification; the example of making cereal bread proves that the high-purity naked oat β-glucan can significantly improve the water holding capacity of cereal products and prolong their shelf life, and can be used in bread, biscuits, and meal replacements to achieve its high-value application.

Description

Technical Field

[0001] The invention belongs to the technical field of food additives, and particularly relates to high-purity naked oat beta-glucan and a preparation method and application thereof. Background Art

[0002] Oat β-glucan is a viscous soluble fiber and a non-starch polysaccharide. The β-glucan content of naked oats is higher than that of hulled oats, and there is a significant difference. Oat β-glucan has functional properties such as good water solubility, high viscosity, and gelation, as well as physiological activities such as lowering blood sugar, lowering cholesterol, anti-cancer, and anti-oxidation. In the food field, oat β-glucan has been applied to bread, biscuits, meal replacements, and nutritional supplements. The addition of oat β-glucan not only enriches the nutritional content of bread, but also improves the dough's kneading resistance. The unique water-retaining property of oat β-glucan also prolongs the shelf life of bread.

[0003] Preparation of oat β-glucan is generally done by solvent extraction or mild alkaline extraction. These methods require the introduction of organic solvents, which are costly and difficult to remove. Moreover, the isoelectric precipitation method is commonly used in the protein separation process, which has low removal efficiency and requires centrifugation, which is not conducive to industrial production. These extraction methods also have the disadvantages of complicated steps, adding many reagents, and low purity of the obtained products. When used to make bread, it will also affect the water retention of bread. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a high-purity naked oat β-glucan and a preparation method and application thereof.

[0005] The technical solution adopted by the present invention is:

[0006] A high-purity naked oat β-glucan, the preparation method of which comprises the following steps:

[0007] 1) Naked oat pretreatment: Naked oats are crushed into naked oat flour, and then boiled in 85% ethanol in a water bath at 85° C. for 3 h, and then filtered to obtain a precipitate after cooling, and then the precipitate is placed in a water bath to evaporate and remove the ethanol to obtain a pretreated product;

[0008] 2) Hot water extraction: The pretreated product was extracted with hot water at 52°C for 2 h, and then the supernatant was collected by centrifugation; the obtained precipitate was further extracted with hot water at 52°C, and then the supernatant was collected by centrifugation; the two supernatants were combined and the precipitate was discarded;

[0009] 3) Enzyme-assisted removal of starch and protein: Dissolve amylase in warm water and add it to the combined supernatant, cook at 60-70°C for 2 hours to remove starch, then add papain and cook at 65°C for 3 hours to remove protein, inactivate the enzyme at 100°C for 15 minutes, then centrifuge to remove the precipitate, and evaporate the supernatant to obtain a concentrated solution;

[0010] 4) Freeze-drying to obtain crude polysaccharide: adding 4 times the volume of 95% ethanol to the concentrate for alcohol precipitation, centrifuging after 12 hours, collecting the precipitate, redissolving the precipitate in water, and freeze-drying;

[0011] 5) Purification of crude polysaccharide to obtain high-purity naked oat β-glucan: freeze-dried samples were prepared into 5 mg / mL polysaccharide solution, precipitated with anhydrous ethanol for 12 h until the ethanol volume fraction was 20%, and the precipitate left after centrifugation was dissolved with a small amount of water, placed in a water bath to evaporate the ethanol, and freeze-dried to obtain high-purity oat β-glucan.

[0012] Furthermore, in the above-mentioned high-purity naked oat β-glucan, in step 1), the material-liquid ratio of naked oat powder to 85% ethanol is 1g:10g.

[0013] Furthermore, in the above-mentioned high-purity naked oat β-glucan, in step 2), the material-liquid ratio of the pretreated product to hot water is 1g:10g.

[0014] Furthermore, in the above-mentioned high-purity naked oat β-glucan, in step 2), the first centrifugation speed is 5000 r / min and the centrifugation time is 10 min; the second centrifugation speed is 6000 r / min and the centrifugation time is 13 min.

[0015] Furthermore, in the above-mentioned high-purity naked oat β-glucan, in step 3), the amount of amylase used is 1.5% of the mass of the pretreated product, and the amount of papain used is 0.5% of the mass of the pretreated product.

[0016] Furthermore, in the above-mentioned high-purity naked oat β-glucan, in step 3), the centrifugal speed is 8000r / min and the centrifugal time is 20min.

[0017] Furthermore, in the above-mentioned high-purity naked oat β-glucan, in step 3), the temperature of the rotary evaporation of the supernatant does not exceed 60°C.

[0018] Furthermore, in the above-mentioned high-purity naked oat β-glucan, in step 4), the centrifugal speed is 7000 r / min and the centrifugal time is 10 min.

[0019] Use of any of the above-mentioned high-purity naked oat β-glucans in the preparation of high water-holding cereal bread.

[0020] Furthermore, in the above application, the mass of high-purity naked oat β-glucan added to the cereal bread is 0.8% to 0.9% of the dry weight of the cereal bread.

[0021] The beneficial effects of the present invention are:

[0022] 1. The present invention innovates a simple method to improve the purity of oat β-glucan with the assistance of enzyme. The raw materials are abundant and easy to obtain, and the production process is simple. After pre-treatment, hot water extraction, enzyme-assisted and other technical means are used. No toxic or harmful drugs are used. It is safer and more environmentally friendly while shortening the extraction time. The oat β-glucan concentrate prepared by ethanol-based enzyme technology has better solubility and higher molecular weight than the product prepared by traditional single water extraction method, reducing waste; the purity of the extracted oat β-glucan reaches 63.14%.

[0023] 2. The high-purity naked oat β-glucan extract obtained by the present invention can be added to cereal bread to significantly improve the water holding capacity of the bread, so that the bread has better texture performance. The moisture content is always at a relatively high state during storage, which prolongs the shelf life and will not affect the consumer acceptance level. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a process flow chart for preparing high-purity naked oat β-glucan.

[0025] Figure 2 The infrared spectra of the high-purity naked oat β-glucan prepared in Example 1 and the commercially available oat β-glucan.

[0026] Figure 3 This is the molecular weight distribution diagram of the high-purity naked oat β-glucan prepared in Example 1. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the invention.

[0028] Example 1

[0029] Preparation process reference Figure 1 .

[0030] 1) Naked oat pretreatment:

[0031] The naked oats were crushed into naked oatmeal powder, 100 g of naked oatmeal powder was weighed, and 1000 mL of 85% ethanol was used to cook in a water bath at 85°C for 3 h, and then the precipitate was filtered out after cooling, and then the precipitate was placed in a water bath to evaporate and remove the ethanol to obtain a pretreated product;

[0032] 2) Hot water extraction:

[0033] Weigh 100 g of the precipitate after removing the ethanol, use 1000 mL of 52°C hot water to extract the precipitate to remove the ethanol for 2 hours, then centrifuge at 5000 r / min for 10 minutes to collect the supernatant; continue to extract the obtained precipitate with 52°C hot water, then centrifuge at 6000 r / min for 13 minutes to collect the supernatant; combine the two supernatants and discard the precipitate;

[0034] 3) Enzyme-assisted removal of starch and protein:

[0035] Dissolve 1.5% of the mass of the pretreatment product in amylase with warm water and add it to the combined supernatant, cook at 65°C for 2h to remove starch, then add 0.5% of the mass of the pretreatment product in papain, cook at 65°C for 3h to remove protein, inactivate the enzyme at 100°C for 15min, then centrifuge at 8000r / min for 20min to remove the precipitate, and rotary evaporate the supernatant at 50°C to obtain a concentrated solution;

[0036] 4) Freeze-drying to obtain crude polysaccharide:

[0037] Take 10 mL of the concentrate, add 40 mL of 95% ethanol to the concentrate for alcohol precipitation, centrifuge at 7000 r / min for 10 min after 12 h, collect the precipitate, redissolve the precipitate in water, and freeze-dry;

[0038] 5) Purification of crude polysaccharide to obtain high-purity naked oat β-glucan:

[0039] The freeze-dried sample was prepared into a 5 mg / mL polysaccharide solution, precipitated with anhydrous ethanol for 12 h until the ethanol volume fraction was 20%, and the precipitate left after centrifugation was dissolved with a small amount of water, placed in a water bath to evaporate the ethanol, and freeze-dried to obtain high-purity oat β-glucan, which was tested to have a purity of 63.14%.

[0040] Example 2

[0041] 1) Naked oat pretreatment:

[0042] The naked oats were crushed into naked oatmeal powder, 100 g of naked oatmeal powder was weighed, and 1000 mL of 85% ethanol was used to cook in a water bath at 85°C for 3 h, and then the precipitate was filtered out after cooling, and then the precipitate was placed in a water bath to evaporate and remove the ethanol to obtain a pretreated product;

[0043] 2) Hot water extraction:

[0044] Weigh 100 g of the precipitate after removing the ethanol, use 1000 mL of 52°C hot water to extract the precipitate to remove the ethanol for 2 hours, then centrifuge at 5000 r / min for 10 minutes to collect the supernatant; continue to extract the obtained precipitate with 52°C hot water, then centrifuge at 6000 r / min for 13 minutes to collect the supernatant; combine the two supernatants and discard the precipitate;

[0045] 3) Enzyme-assisted removal of starch and protein:

[0046] Dissolve 1.5% of the mass of the pretreatment product in amylase with warm water and add it to the combined supernatant, cook at 60°C for 2h to remove starch, then add 0.5% of the mass of the pretreatment product in papain, cook at 65°C for 3h to remove protein, inactivate the enzyme at 100°C for 15min, then centrifuge at 8000r / min for 20min to remove the precipitate, and rotary evaporate the supernatant at 40°C to obtain a concentrated solution;

[0047] 4) Freeze-drying to obtain crude polysaccharide:

[0048] Take 10 mL of the concentrate, add 40 mL of 95% ethanol to the concentrate for alcohol precipitation, centrifuge at 7000 r / min for 10 min after 12 h, collect the precipitate, redissolve the precipitate in water, and freeze-dry;

[0049] 5) Purification of crude polysaccharide to obtain high-purity naked oat β-glucan:

[0050] The freeze-dried sample was prepared into a 5 mg / mL polysaccharide solution, precipitated with anhydrous ethanol for 12 h until the ethanol volume fraction was 20%, and the precipitate left after centrifugation was dissolved with a small amount of water, placed in a water bath to evaporate the ethanol, and freeze-dried to obtain high-purity oat β-glucan, which was tested to have a purity of 60%.

[0051] Example 3

[0052] 1) Naked oat pretreatment:

[0053] The naked oats were crushed into naked oatmeal powder, 100 g of naked oatmeal powder was weighed, and 1000 mL of 85% ethanol was used to cook in a water bath at 85°C for 3 h, and then the precipitate was filtered out after cooling, and then the precipitate was placed in a water bath to evaporate and remove the ethanol to obtain a pretreated product;

[0054] 2) Hot water extraction:

[0055] Weigh 100 g of the precipitate after removing the ethanol, use 1000 mL of 52°C hot water to extract the precipitate to remove the ethanol for 2 hours, then centrifuge at 5000 r / min for 10 minutes to collect the supernatant; continue to extract the obtained precipitate with 52°C hot water, then centrifuge at 6000 r / min for 13 minutes to collect the supernatant; combine the two supernatants and discard the precipitate;

[0056] 3) Enzyme-assisted removal of starch and protein:

[0057] 1.5% of the mass of the pretreatment product amylase was dissolved in warm water and added to the combined supernatant, and the starch was removed at 70°C for 2 hours. Then 0.5% of the mass of the pretreatment product papain was added, and the protein was removed at 65°C for 3 hours. The enzyme was inactivated at 100°C for 15 minutes, and then the precipitate was removed by centrifugation at 8000 r / min for 20 minutes. The supernatant was rotary evaporated at 60°C to obtain a concentrated solution;

[0058] 4) Freeze-drying to obtain crude polysaccharide:

[0059] Take 10 mL of the concentrate, add 40 mL of 95% ethanol to the concentrate for alcohol precipitation, centrifuge at 7000 r / min for 10 min after 12 h, collect the precipitate, redissolve the precipitate in water, and freeze-dry;

[0060] 5) Purification of crude polysaccharide to obtain high-purity naked oat β-glucan:

[0061] The freeze-dried sample was prepared into a 5 mg / mL polysaccharide solution, precipitated with anhydrous ethanol for 12 h until the ethanol volume fraction was 20%, and the precipitate left after centrifugation was dissolved with a small amount of water, placed in a water bath to evaporate the ethanol, and freeze-dried to obtain high-purity oat β-glucan, which was tested to have a purity of 54%.

[0062] Figure 2 The infrared spectra of the high-purity oat β-glucan prepared in Example 1 and the commercially available oat β-glucan are shown in FIG. Figure 2 It can be seen that the high-purity oat β-glucan prepared in Example 1 has significant absorption peaks of carbohydrate substances, including absorption peaks of intramolecular or intermolecular hydrogen bonds, methylene, etc. Figure 3 This is the molecular weight diagram of the high-purity oat β-glucan prepared in Example 1. Figure 3 It can be seen that the molecular weight dispersion coefficient of the high-purity oat β-glucan prepared in Example 1 is small, indicating that it has good uniformity.

[0063] Example 4 Application

[0064] 1) Kneading: Dissolve the highly active dry yeast and sucrose with appropriate amount of warm water, and then put them into a kneading cylinder containing high-gluten wheat flour, add egg liquid, and add the remaining water and high-purity naked oat β-glucan prepared in Example 1 in batches. After kneading, cover with plastic wrap and relax the dough for 20 minutes, knead butter and salt into the dough respectively, and finally make the dough reach a state of full gluten expansion. At this time, the dough should have a smooth surface, no cracks, soft hand feel, and can generally be pulled into a uniform film. The temperature of the kneaded dough should be 30℃±1℃.

[0065] 2) Shaping: Take the adjusted dough out of the dough mixing bowl and knead it into a cuboid with your hands.

[0066] 3) Fermentation: Place the shaped dough in a slightly oiled fermentation bowl, apply a thin layer of egg liquid on the surface of the dough and place it in a fermentation box to ferment for 60 minutes. After the fermentation is over, poke a hole in it. If it does not shrink or rebound, it means the fermentation is just right.

[0067] 4) Baking and cooling: After fermentation, the bread is immediately placed in an oven for baking at 180°C for 10 min. When the surface of the bread turns brown, it is taken out and cooled at room temperature to obtain bread with added high-purity naked oat β-glucan (WB with OBG-20).

[0068] Application Comparative Example 1

[0069] 1) Mixing dough: Dissolve highly active dry yeast and sucrose with appropriate amount of warm water, and then put them into the mixing bowl containing high-gluten wheat flour, add egg liquid, and add the remaining water and commercial naked oat β-glucan in batches. After mixing the dough, cover with plastic wrap and relax the dough for 20 minutes, knead butter and salt into the dough respectively, and finally make the dough reach a state of full gluten expansion. At this time, the dough should have a smooth surface, no cracks, and a soft feel. It can generally be pulled into a uniform film. The temperature of the mixed dough should be 30℃±1℃.

[0070] 2) Shaping: Take the adjusted dough out of the dough mixing bowl and knead it into a cuboid with your hands.

[0071] 3) Fermentation: Place the shaped dough in a slightly oiled fermentation bowl, apply a thin layer of egg liquid on the surface of the dough and place it in a fermentation box to ferment for 60 minutes. After the fermentation is over, poke a hole in it. If it does not shrink or rebound, it means the fermentation is just right.

[0072] 4) Baking and cooling: After fermentation, the bread was immediately put into the oven for baking at 180°C for 10 min. When the surface of the bread turned brown, it was taken out and cooled at room temperature to obtain wheat bread with commercially available oat β-glucan (WB with OBG-CA).

[0073] Application Comparative Example 2

[0074] 1) Mixing dough: Dissolve highly active dry yeast and sucrose with appropriate amount of warm water, and then put them into the mixing bowl containing high-gluten wheat flour, add egg liquid and the remaining water. After mixing, cover with plastic wrap and relax the dough for 20 minutes, knead butter and salt into the dough respectively, and finally make the dough reach a state of full gluten expansion. At this time, the dough should have a smooth surface, no cracks, soft touch, and can generally be pulled into a uniform film. The temperature of the mixed dough should be 30℃±1℃.

[0075] 2) Shaping: Take the adjusted dough out of the dough mixing bowl and knead it into a cuboid with your hands.

[0076] 3) Fermentation: Place the shaped dough in a slightly oiled fermentation bowl, apply a thin layer of egg liquid on the surface of the dough and place it in a fermentation box to ferment for 60 minutes. After the fermentation is over, poke a hole in it. If it does not shrink or rebound, it means the fermentation is just right.

[0077] 4) Baking and cooling: After fermentation, the bread is immediately put into the oven for baking at 180°C for 10 min. When the surface of the bread turns brown, it is taken out and cooled at room temperature to obtain wheat bread (WB).

[0078] 5) The effect of high-purity naked oat β-glucan extract was evaluated by constructing a cereal bread model and exploring its physicochemical properties. The physicochemical properties characterization of the above model included the following steps:

[0079] Determination of moisture content of bread: The moisture content of bread was determined according to the method of GB / T 20981-2021 Determination of moisture in food. The results are shown in Table 1.

[0080] Table 1 Comparison of moisture content of three types of bread

[0081] Basic Ingredients / Types of Bread WB WB with OBG-CA WB with OBG-20 Water content (g / 100g) <![CDATA[37.683±0.012 a ]]> <![CDATA[36.979±0.142 a ]]> <![CDATA[37.801±0.118 a ]]>

[0082] Note: The results are expressed as the mean ± standard deviation of three parallel experiments. Different letters indicate significant differences (P < 0.05).

[0083] Effect of high-purity naked oat β-glucan on bread texture: The baked bread was cooled at room temperature, put into a fresh-keeping bag and sealed at room temperature for two days. The bread texture was tested every 24 hours. The results are shown in Table 2.

[0084] Table 2 Comparison of texture changes of three types of bread

[0085]

[0086] Note: The results are expressed as the mean ± standard deviation of three parallel experiments. Different letters indicate significant differences (P < 0.05).

[0087] Effect of high-purity naked oat β-glucan on storage stability of bread: The baked bread was cooled at room temperature, put into a fresh-keeping bag and sealed at room temperature for two days. The moisture and hardness of the bread were tested every 24 hours. The results are shown in Tables 3 and 4.

[0088] Table 3 Comparison of moisture changes of three types of bread

[0089] Moisture content (g / 100g) / sample WB WB with OBG-CA WB with OBG-20 Moisture content on the first day <![CDATA[37.683±0.012 a ]]> <![CDATA[37.479±0.565 a ]]> <![CDATA[37.800±0.118 a ]]> Moisture content on the second day <![CDATA[33.993±0.594 a ]]> <![CDATA[35.094±0.018 ab ]]> <![CDATA[35.366±0.338 b ]]> Moisture content on the third day <![CDATA[32.325±0.417 a ]]> <![CDATA[33.232±0.450 ab ]]> <![CDATA[34.230±0.302 b ]]>

[0090] Note: The results are expressed as the mean ± standard deviation of three parallel experiments. Different letters indicate significant differences (P < 0.05).

[0091] Table 4 Comparison of hardness changes of three types of bread

[0092] sample Bread hardness on the first day (N) Bread hardness on the second day (N) Bread hardness on the third day (N) WB <![CDATA[3.42±0.12 b ]]> <![CDATA[9.20±0.76 b ]]> <![CDATA[10.33±0.63 b ]]> WB with OBG-CA <![CDATA[3.18±0.15 b ]]> <![CDATA[8.82±0.88 b ]]> <![CDATA[9.61±0.07 b ]]> WB with OBG-20 <![CDATA[2.53±0.16 a ]]> <![CDATA[6.93±0.36 a ]]> <![CDATA[8.63±0.06 a ]]>

[0093] Note: The results are expressed as the mean ± standard deviation of three parallel experiments. Different letters indicate significant differences (P < 0.05).

[0094] The above results show that high-purity naked oat β-glucan, due to its high water binding capacity, contributes to better hydration in the dough matrix and complete formation of the gluten network, improves elasticity, significantly reduces the hardness, stickiness, and chewiness of bread, and improves the texture characteristics of bread. In addition, during storage, the moisture in the bread migrates from the bread crumb to the surface, and high-purity naked oat β-glucan has a strong water-holding capacity, which hinders the diffusion of moisture and improves the water-retention capacity of the internal microstructure of the bread. Therefore, the moisture content of the bread added with high-purity naked oat β-glucan is always at a relatively high state during storage, the hardness is low, and the shelf life of the bread is extended.

[0095] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A high-purity naked oat β-glucan, characterized in that: The preparation method comprises the following steps: 1) Naked oat pretreatment: Naked oats were crushed into naked oat flour, and then boiled in 85% ethanol in a water bath at 85°C for 3 h. After cooling, the precipitate was filtered to obtain a precipitate, and then the precipitate was placed in a water bath to evaporate and remove the ethanol to obtain a pretreated product; 2) Hot water extraction: The pretreated product was extracted with hot water at 52°C for 2 h, and then the supernatant was collected by centrifugation; the obtained precipitate was further extracted with hot water at 52°C, and then the supernatant was collected by centrifugation; the two supernatants were combined and the precipitate was discarded; 3) Enzyme-assisted removal of starch and protein: Dissolve amylase in warm water and add it to the combined supernatant, cook at 60-70℃ for 2h to remove starch, then add papain and cook at 65℃ for 3h to remove protein, inactivate the enzyme at 100℃ for 15min, then centrifuge to remove the precipitate, and evaporate the supernatant to obtain a concentrated solution; The dosage of amylase was 1.5% of the mass of the pretreatment product, and the dosage of papain was 0.5% of the mass of the pretreatment product; 4) Freeze-drying to obtain crude polysaccharide: add 4 times the volume of 95% ethanol to the concentrate for alcohol precipitation, centrifuge after 12 hours, collect the precipitate, redissolve the precipitate in water, and freeze-dry; 5) Purification of crude polysaccharide to obtain high-purity naked oat β-glucan: freeze-dried samples were prepared into 5 mg / mL polysaccharide solution, precipitated with anhydrous ethanol for 12 h until the ethanol volume fraction was 20%, and the precipitate left after centrifugation was dissolved with a small amount of water, placed in a water bath to evaporate the ethanol, and freeze-dried to obtain high-purity oat β-glucan.

2. A high-purity naked oat β-glucan according to claim 1, characterized in that: In step 1), the material-liquid ratio of naked oatmeal powder to 85% ethanol is 1 g:10 g.

3. A high-purity naked oat β-glucan according to claim 1, characterized in that: In step 2), the material-liquid ratio of the pretreated product to hot water is 1 g:10 g.

4. The high-purity naked oat β-glucan according to claim 1, characterized in that: In step 2), the first centrifugation speed is 5000 r / min and the centrifugation time is 10 min; the second centrifugation speed is 6000 r / min and the centrifugation time is 13 min.

5. The high-purity naked oat β-glucan according to claim 1, characterized in that: In step 3), the centrifugal speed is 8000 r / min and the centrifugal time is 20 min.

6. The high-purity naked oat β-glucan according to claim 1, characterized in that: In step 3), the temperature of the supernatant during rotary evaporation does not exceed 60°C.

7. The high-purity naked oat β-glucan according to claim 1, characterized in that: In step 4), the centrifugal speed is 7000 r / min and the centrifugal time is 10 min.

8. Use of the high-purity naked oat β-glucan according to any one of claims 1 to 7 in the preparation of high water-holding cereal bread.

9. The use according to claim 8, characterized in that: The added mass of high-purity naked oat β-glucan in cereal bread is 0.8%~0.9% of the dry weight of cereal bread.

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