Gracilaria powder with high water-retaining property and low heavy metal content and preparation method of gracilaria powder

Abstract

The invention discloses gracilaria powder with high water-retaining property and low heavy metal content and a preparation method thereof, and the preparation method comprises the following steps: washing gracilaria, adding saccharomycetes liquid, and carrying out sealed fermentation at 20-30 DEG C to obtain a gracilaria fermentation product; filtering the gracilaria fermentation product to remove the yeast liquid, washing the gracilaria fermentation product with 30-50 times of water for 1-4 times, adding a 0.9% sodium chloride solution, adding medium-temperature alpha-amylase and saccharifying enzyme, and carrying out enzymolysis at 45-60 DEG C to obtain a gracilaria enzymolysis product; and filtering out enzymatic hydrolysate from the gracilaria enzymolysis product, adding food-grade citric acid for acid hydrolysis, filtering out reaction liquid, drying, crushing and sieving to obtain the gracilaria powder. According to the method, the gracilaria is subjected to specific pretreatment and synergistic processing of fermentation, enzymolysis and acid treatment, so that the water retention capacity of the gracilaria powder is remarkably improved, and meanwhile, the heavy metal content is remarkably reduced.

Description

Technical Field

[0001] This invention relates to the technical field of seaweed processing, specifically to a Gracilaria powder with high water retention and low heavy metal content and its preparation method. Background Technology

[0002] Gracilaria is an important economic seaweed, belonging to the phylum Rhodophyta, class Evoryopsida, order Gracilaria, and family Gracilariaceae. Gracilaria is rich in mucilage and is a recognized source of raw materials for agar extraction. In the food industry, Gracilaria powder can be used as a thickener and stabilizer; in the cosmetics and pharmaceutical fields, it can be used as a film-forming material.

[0003] However, the Gracilaria powder prepared by washing and crushing has two problems. On the one hand, Gracilaria powder has poor water retention. On the other hand, Gracilaria powder contains a certain amount of heavy metals, including lead, cadmium, arsenic, and copper. Therefore, it is of great significance to develop a Gracilaria powder processing method that can improve the water retention of Gracilaria powder while reducing the heavy metal content. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides Gracilaria powder with high water retention and low heavy metal content, and its preparation method. This method significantly improves the water retention performance of Gracilaria powder and significantly reduces the heavy metal content by subjecting Gracilaria to specific pretreatment and utilizing fermentation, enzymatic hydrolysis, and acid treatment in a synergistic process.

[0005] An embodiment of the present invention provides a method for preparing Gracilaria powder with high water retention and low heavy metal content, which includes the following steps: Step 1: Wash the Gracilaria, add yeast culture and seal for fermentation at 20 ℃~30 ℃ to obtain Gracilaria fermentation product; Step 2: Filter the fermented product of Gracilaria to remove the yeast liquid, wash it 1 to 4 times with 30 to 50 times the amount of water, add 0.9% sodium chloride solution, and add medium-temperature α-amylase and saccharifying enzyme to carry out enzymatic hydrolysis at 45 ℃-60 ℃ to obtain the enzymatic hydrolysis product of Gracilaria. Step 3: Filter out the enzymatic hydrolysate from the Gracilaria enzymatic hydrolysate, add food-grade citric acid for acid hydrolysis, filter out the reaction solution, dry, pulverize, and sieve to obtain Gracilaria powder.

[0006] This invention discloses a method for preparing Gracilaria powder with high water retention and low heavy metal content. The method employs a combination of fermentation, enzymatic hydrolysis, and acid hydrolysis to treat Gracilaria. The alcohol dehydrogenases and aldehyde dehydrogenases in the yeast can oxidize or reduce aldehydes and enaldehydes into alcohols and acids, increasing water retention. Simultaneously, amylase and saccharifying enzymes hydrolyze starch and other components, forming a porous network structure. Then, citric acid forms soluble complexes with metal ions, promoting their migration. The resulting Gracilaria powder exhibits a 1.91-fold increase in water retention, along with a high heavy metal removal rate, resulting in heavy metal content in the obtained Gracilaria powder below the national standard. The fermentation strains and enzyme preparations used in this application are safe and environmentally friendly biological materials that do not introduce new chemical impurities, meeting green and environmentally friendly production requirements and possessing promising application prospects.

[0007] Optionally, in step one, the ratio of Gracilaria to yeast culture liquid is 1:20 g / mL.

[0008] Optionally, in step one, the mixture is sealed and fermented at 25 °C for 4 h.

[0009] Optionally, in step one, the yeast culture is prepared as follows: take 0.5~1.5 g of Angel high-temperature resistant brewing high-activity dry yeast, add 1000 mL of sterilized 3% white sugar solution, mix well, seal and place at room temperature for 10 h for activation, and then dilute 2~8 times to obtain the culture.

[0010] Optionally, in step two, the concentration of mesophilic α-amylase is 0.10~0.25% w / w, and the concentration of saccharifying enzyme is 0.05~0.15% w / w.

[0011] Optionally, in step two, the enzymatic hydrolysis time is 1.5 to 3 hours.

[0012] Optionally, in step two, the pH of the solution is adjusted to 5.0-6.0 using 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide.

[0013] Optionally, in step three, the concentration of the food-grade citric acid is 1.5~3.0% w / v; the acid hydrolysis is carried out by stirring at 37°C for 12 h.

[0014] Optionally, in step three, the drying temperature is 60 ℃, the drying time is 12 h, and the material is pulverized and passed through a 60-mesh sieve.

[0015] The embodiments of the present invention also propose the above-described preparation method to obtain Gracilaria powder with high water retention and low heavy metal content. This Gracilaria powder has the characteristics of high water retention and low heavy metal content, and has high application value.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0017] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0018] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0019] The test materials used in this invention are all common commercial products and can be purchased on the market.

[0020] The raw material for the fine-grained gynostemma pentaphyllum was provided by Green New (Fujian) Food Co., Ltd.

[0021] The yeast used is Angel high-temperature resistant active dry yeast.

[0022] Determination of water-holding capacity of Gracilaria powder: Weigh 0.5 g of Gracilaria powder into a 50 mL centrifuge tube, and record its mass as W1. Add 30 mL of distilled water, place in a 37 ℃ water bath for 30 min, shake well, centrifuge at 4000 rpm for 15 min, discard the supernatant, and record its mass as W2. Water-holding capacity (%) = (W2 - W1) / W1 × 100. Where W1 is the mass of Gracilaria powder before centrifugation, g; W2 is the mass of Gracilaria powder after centrifugation, g.

[0023] Determination of heavy metal content in gecko powder: The contents of Pb, As, Cd and Cu were determined according to GB 5009.268-2016 "Determination of multiple elements in food".

[0024] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0025] Example 1 Step 1: Take 0.5 g of Angel high-temperature resistant brewing yeast, add 1000 mL of sterilized 3% sugar solution, seal and activate at room temperature for 10 h. Accurately weigh 20 g of Gracilaria, wash with 15 times the volume of water, place in a 500 mL Erlenmeyer flask, add yeast solution diluted 2 times at a ratio of 1:20 (g / mL), mix well and ferment at 25 ℃ for 4 h.

[0026] Step 2: Filter the Gracilaria fermentation product obtained in Step 1 to remove the yeast culture, and wash once with 30 times the amount of water. Add 0.9% NaCl solution at a ratio of 1:10, adjust the pH to 5 with 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide, add 0.10% (w / w) mesophilic α-amylase and 0.05% (w / w) saccharifying enzyme, and react in a 45 ℃ constant temperature water bath for 1.5 h.

[0027] Step 3: Filter the enzymatic hydrolysate of Gracilaria obtained in Step 2, remove the hydrolysate, add 1.5% (w / v) of food-grade citric acid, place it in a shaking incubator at 37 ℃ and 100 rpm for 12 h, filter the reaction solution, dry it at 60 ℃ for 12 h, then pulverize it and pass it through a 60-mesh sieve to obtain Gracilaria powder.

[0028] As shown in Table 1, the water-holding capacity of the Gracilaria powder obtained in this embodiment was 582%, and the content of lead (Pb) was 0.209 mg / kg, arsenic (As) was 0.349 mg / kg, cadmium (Cd) was 0.0137 mg / kg, and copper (Cu) was 1.475 mg / kg. Compared with my country's GB 2762-2022 "Limits of Contaminants in Food", the heavy metal content of the Gracilaria powder obtained in this embodiment is lower than the national standard. Compared with Comparative Example 1, the water-holding capacity of this embodiment is approximately 1.76 times that of Comparative Example 1, and the contents of heavy metals Pb, As, Cd, and Cu are all lower than those of Comparative Example 1. This indicates that the synergistic treatment method of fermentation-enzymatic hydrolysis-acid hydrolysis is more effective than the synergistic treatment method of enzymatic hydrolysis-acid hydrolysis alone. Therefore, fermentation is an essential condition for improving water-holding capacity and reducing heavy metals through the synergistic treatment of fermentation-enzymatic hydrolysis-acid hydrolysis.

[0029] Example 2 Step 1: Take 1.5 g of Angel high-temperature resistant brewing yeast, add 1000 mL of sterilized 3% sugar solution, seal and activate at room temperature for 10 h. Accurately weigh 20 g of Gracilaria, wash with 20 times the volume of water, place in a 500 mL Erlenmeyer flask, add yeast solution diluted 8 times at a material-to-liquid ratio of 1:20 (g / mL), and seal for fermentation at 25 ℃ for 4 h.

[0030] Step 2: Filter the Gracilaria fermentation broth obtained in Step 1 to remove the yeast culture, wash it 4 times with 50 times the amount of water, add 0.9% NaCl solution at a ratio of 1:10, adjust the pH to 6 with 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide, add 0.25% (w / w) mesophilic α-amylase and 0.15% (w / w) saccharifying enzyme, and react in a 60 ℃ constant temperature water bath for 3 h.

[0031] Step 3: Filter the enzymatic hydrolysate of Gracilaria obtained in Step 2, remove the hydrolysate, add 3.0% (w / v) of food-grade citric acid, place it in a shaking incubator at 37 ℃ and 100 rpm for 12 h, filter the reaction solution, dry it at 60 ℃ for 12 h, then pulverize it and pass it through a 60-mesh sieve to obtain Gracilaria powder.

[0032] As shown in Table 1, the water-holding capacity of the Gracilaria powder obtained in this embodiment was 623%, and the heavy metal content was 0.205 mg / kg for Pb, 0.340 mg / kg for As, 0.0082 mg / kg for Cd, and 1.358 mg / kg for Cu. Compared with my country's GB2762-2022 "Limits of Contaminants in Food", the heavy metal content of the Gracilaria powder obtained in this embodiment is lower than the national standard. Compared with Comparative Example 2, the water-holding capacity of Example 2 is approximately 1.45 times that of Comparative Example 2, and the heavy metal contents (Pb, As, Cd, and Cu) are all lower. In particular, the Cd content in Comparative Example 2 is 1.89 times that in Example 2. This indicates that the synergistic treatment method of fermentation-enzymatic hydrolysis-acid hydrolysis is more effective than the synergistic treatment method of fermentation-acid hydrolysis alone. Therefore, enzymatic hydrolysis is an essential condition for improving water-holding capacity and reducing heavy metals through the synergistic treatment of fermentation-enzymatic hydrolysis-acid hydrolysis.

[0033] Example 3 Step 1: Take 1 g of Angel high-temperature resistant brewing yeast and add it to 1000 mL of sterilized 3% sugar solution. Seal and activate at room temperature for 10 h. Accurately weigh 20 g of Gracilaria, wash it with 17.5 times the volume of water, and add yeast solution diluted 6 times to a 500 mL Erlenmeyer flask at a material-to-liquid ratio of 1:20 (g / mL). Seal and ferment at 25 ℃ for 4 h.

[0034] Step 2: Filter the Gracilaria fermentation broth obtained in Step 1 to remove the yeast culture, wash twice with 40 times the amount of water, add 0.9% NaCl solution at a ratio of 1:10, adjust the pH to 5.5 with 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide, add 0.15% (w / w) mesophilic α-amylase and 0.10% (w / w) saccharifying enzyme, and react in a 50 ℃ constant temperature water bath for 2 h.

[0035] Step 3: Filter the enzymatic hydrolysate of Gracilaria obtained in Step 2, remove the hydrolysate, add 2.5% (w / v) of food-grade citric acid, place it in a shaking incubator at 37 ℃ and 100 rpm for 12 h, filter the reaction solution, dry it at 60 ℃ for 12 h, then pulverize it and pass it through a 60-mesh sieve to obtain Gracilaria powder.

[0036] As shown in Table 1, the water-holding capacity of the Gracilaria powder obtained in this embodiment was 622%, and the heavy metal content was 0.208 mg / kg for Pb, 0.341 mg / kg for As, 0.0095 mg / kg for Cd, and 1.390 mg / kg for Cu. Compared with my country's GB2762-2022 "Limits of Contaminants in Food", the heavy metal content of the Gracilaria powder obtained in this embodiment is lower than the national standard. Compared with Comparative Example 3, the water-holding capacity of Example 3 is approximately 1.53 times that of Comparative Example 3, and the heavy metal contents (Pb, As, Cd, and Cu) are all lower than those of Comparative Example 3. In particular, the Cd content in Comparative Example 3 is 1.94 times that in Example 3. This indicates that the synergistic treatment method of fermentation-enzymatic hydrolysis-acid hydrolysis is more effective than the synergistic treatment method of fermentation-enzymatic hydrolysis alone. Therefore, acid hydrolysis is an essential condition for improving water-holding capacity and reducing heavy metals through the synergistic treatment of fermentation-enzymatic hydrolysis-acid hydrolysis.

[0037] Example 4 Step 1: Take 1 g of Angel high-temperature resistant brewing yeast and add it to 1000 mL of sterilized 3% sugar solution. Seal the container and activate it at room temperature for 10 h. Accurately weigh 20 g of Gracilaria, wash it with 17.5 times its volume of water, and add it to a 500 mL Erlenmeyer flask. Add yeast solution diluted 4 times at a ratio of 1:20 (g / mL) and ferment at 25 ℃ for 4 h.

[0038] Step 2: Filter the Gracilaria fermentation broth obtained in Step 1 to remove the yeast culture, wash it three times with 40 times the amount of water, add 0.9% NaCl solution at a ratio of 1:10, adjust the pH to 5 with 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide, add 0.20% (w / w) mesophilic α-amylase and 0.10% (w / w) saccharifying enzyme, and react in a constant temperature water bath at 55 ℃ for 2.5 h.

[0039] Step 3: Filter the enzymatic hydrolysate of Gracilaria obtained in Step 2, remove the hydrolysate, add 2.0% (w / v) of food-grade citric acid, place it in a shaking incubator at 37 ℃ and 100 rpm for 12 h, filter the reaction solution, dry it at 60 ℃ for 12 h, then pulverize it and pass it through a 60-mesh sieve to obtain Gracilaria powder.

[0040] As shown in Table 1, the water-holding capacity of the Gracilaria powder obtained in this embodiment was 633%, and the heavy metal content was 0.200 mg / kg for Pb, 0.325 mg / kg for As, 0.0060 mg / kg for Cd, and 1.347 mg / kg for Cu. Compared with my country's GB2762-2022 "Limits of Contaminants in Food", the heavy metal content of the Gracilaria powder obtained in this embodiment is lower than the national standard. The water-holding capacity of the Gracilaria powder obtained in this embodiment is higher than that of other embodiments and comparative examples, and the heavy metal content is lower than that of other embodiments and comparative examples, indicating that parameter optimization can further improve water-holding capacity and reduce heavy metal content.

[0041] Comparative Example 1 Step 1: Accurately weigh 20 g of Gracilaria, wash it with 15 times the volume of water, and place it in a 500 mL Erlenmeyer flask. Remove impurities such as mud and broken shells mixed in with the Gracilaria. Add 0.9% NaCl solution at a ratio of 1:10. Adjust the pH to 5 with 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide. Add 0.10% (w / w) medium-temperature α-amylase and 0.05% (w / w) saccharifying enzyme. React in a constant temperature water bath at 45℃ for 1.5 h. After the reaction is complete, filter out the enzyme hydrolysate.

[0042] Step two, add 1.5% (w / v) of food-grade citric acid, place in a shaking incubator at 37 ℃ and 100 rpm for 12 h, filter out the reaction solution, dry at 60 ℃ for 12 h, then pulverize and pass through a 60-mesh sieve to obtain Gracilaria powder.

[0043] As shown in Table 1, the water-holding capacity of the Gracilaria powder obtained in this comparative example was 331%, the content of heavy metals Pb was 0.258 mg / kg, the content of As was 0.383 mg / kg, the content of Cd was 0.0162 mg / kg, and the content of Cu was 1.496 mg / kg. The water-holding capacity obtained in this comparative example was lower than that of the example, and the heavy metal content was higher than that of the example.

[0044] Comparative Example 2 Step 1: Take 1.5 g of Angel high-temperature resistant brewing yeast and add it to 1000 mL of sterilized 3% sugar solution. Seal and activate at room temperature for 10 h. Accurately weigh 20 g of Gracilaria, wash it with 20 times its volume of water, and place it in a 500 mL Erlenmeyer flask. Remove any impurities such as mud and broken shells from the Gracilaria. Add yeast solution diluted 8 times to the 500 mL Erlenmeyer flask at a material-to-liquid ratio of 1:20 (g / mL). Seal and ferment at 25 ℃ for 4 h. Filter out the yeast solution and wash four times with 50 times its volume of water.

[0045] Step 2: Add 3.0% (w / v) of food-grade citric acid, place in a shaking incubator at 37 ℃ and 100 rpm for 12 h, filter out the reaction solution, dry at 60 ℃ for 12 h, then pulverize and pass through a 60-mesh sieve to obtain Gracilaria powder.

[0046] As shown in Table 1, the water-holding capacity of the Gracilaria powder obtained in this comparative example was 431%, the content of heavy metals Pb was 0.213 mg / kg, the content of As was 0.352 mg / kg, the content of Cd was 0.0155 mg / kg, and the content of Cu was 1.490 mg / kg. The water-holding capacity obtained in this comparative example was lower than that of the example, and the heavy metal content was higher than that of the example.

[0047] Comparative Example 3 Step 1: Take 1 g of Angel high-temperature resistant brewing yeast and add it to 1000 mL of sterilized 3% sugar solution. Seal and activate at room temperature for 10 h. Accurately weigh 20 g of Gracilaria, wash it with 17.5 times its volume of water, and place it in a 500 mL Erlenmeyer flask. Remove any impurities such as mud and broken shells from the Gracilaria. Add yeast solution diluted 6 times to the 500 mL Erlenmeyer flask at a material-to-liquid ratio of 1:20 (g / mL). Seal and ferment at 25 ℃ for 4 h. Filter out the yeast solution and wash twice with 40 times its volume of water.

[0048] Step two: Add 0.9% NaCl solution at a ratio of 1:10, adjust the pH to 5.5 with 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide, add 0.15% (w / w) mesophilic α-amylase and 0.10% (w / w) saccharifying enzyme, and react in a 50 ℃ constant temperature water bath for 2 h. After the reaction is complete, filter off the enzyme hydrolysate, dry at 60 ℃ for 12 h, and pulverize through a 60 mesh sieve to obtain Gracilaria powder.

[0049] As shown in Table 1, the water-holding capacity of the Gracilaria powder obtained in this comparative example was 406%, the content of heavy metals Pb was 0.295 mg / kg, the content of As was 0.396 mg / kg, the content of Cd was 0.0184 mg / kg, and the content of Cu was 1.871 mg / kg. The water-holding capacity obtained in this comparative example was lower than that of the example, and the heavy metal content was higher than that of the example.

[0050] Comparative Example 4 Step 1: Accurately weigh 20 g of Gracilaria, wash it with 15 times the volume of water, and place it in a 500 mL Erlenmeyer flask to remove impurities such as mud and broken shells mixed in with the Gracilaria. Add 0.9% NaCl solution at a ratio of 1:10, adjust the pH to 5 with 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide, add 0.20% (w / w) medium-temperature α-amylase and 0.10% (w / w) saccharifying enzyme, and react in a constant temperature water bath at 55℃ for 2.5 h.

[0051] Step 2: Take 1 g of Angel high-temperature resistant brewing yeast and add it to 1000 mL of sterilized 3% sugar solution. Seal the mixture and activate it at room temperature for 10 h. Filter the Gracilaria enzymatic hydrolysate obtained in Step 1, remove the hydrolysate, and wash it three times with 40 times the amount of water. Then add yeast culture diluted 4 times at a material-to-liquid ratio of 1:20 (g / mL) and ferment in a sealed container at 25 ℃ for 4 h.

[0052] Step 3: Filter the fermentation broth of Gracilaria obtained in Step 2 to remove the yeast liquid, then add 2.0% (w / v) of food-grade citric acid, place it in a shaking incubator at 37 ℃ and 100 rpm for 12 h, filter out the reaction liquid, dry it at 60 ℃ for 12 h, then pulverize it and pass it through a 60-mesh sieve to obtain Gracilaria powder.

[0053] As shown in Table 1, the water-holding capacity of the Gracilaria powder obtained in this comparative example was 562%, and the heavy metal content was 0.211 mg / kg for Pb, 0.350 mg / kg for As, 0.0146 mg / kg for Cd, and 1.482 mg / kg for Cu. Compared with my country's GB 2762-2022 "Limits of Contaminants in Food", the heavy metal content of the Gracilaria powder obtained in this comparative example is lower than the national standard.

[0054] Table 1 compares the water-holding capacity and heavy metal content of the Gracilaria powder obtained according to the embodiments of the present invention.

[0055] my country's GB 2762-2022 standard, "Limits of Contaminants in Food," specifies the limits for contaminants in algae and their products. The Chinese national standard for lead in algae products (excluding spirulina products) is 1 mg / kg, which is one-fifth of the French limit (5.0 mg / kg). Current Chinese standards do not specify limits for arsenic, cadmium, and copper in seaweed. France specifies a maximum limit of 0.5 mg / kg for cadmium and 3 mg / kg for arsenic in edible seaweed. As shown in Table 1, the heavy metal content in the Gracilaria powder obtained in this application is lower than the national standards.

[0056] In summary, according to embodiments of the present invention, a combined fermentation-enzymatic hydrolysis-acid hydrolysis method, through the synergistic effect of multiple mechanisms, significantly improves the water retention capacity and heavy metal removal rate of Gracilaria powder. Tests show that this method increases the water retention capacity of Gracilaria powder by 1.91 times while achieving a high heavy metal removal rate. The fermentation strains and enzyme preparations used in this application are all safe and environmentally friendly biological materials that do not introduce new chemical impurities, meeting green and environmentally friendly production requirements and possessing promising application prospects.

[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. The illustrative expressions of the above terms in this specification should not be construed as necessarily referring to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0058] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing Gracilaria powder with high water retention and low heavy metal content, characterized in that, Includes the following steps: Step 1: Wash the Gracilaria, add yeast culture and seal for fermentation at 20 ℃~30 ℃ to obtain Gracilaria fermentation product; Step 2: Filter the fermented product of Gracilaria to remove the yeast liquid, wash it 1 to 4 times with 30 to 50 times the amount of water, add 0.9% sodium chloride solution, and add medium-temperature α-amylase and saccharifying enzyme to carry out enzymatic hydrolysis at 45 ℃-60 ℃ to obtain the enzymatic hydrolysis product of Gracilaria. Step 3: Filter out the enzymatic hydrolysate from the Gracilaria enzymatic hydrolysate, add food-grade citric acid for acid hydrolysis, filter out the reaction solution, dry, pulverize, and sieve to obtain Gracilaria powder.

2. The preparation method according to claim 1, characterized in that, In step one, the ratio of Gracilaria to yeast culture liquid is 1:20 g / mL.

3. The preparation method according to claim 1, characterized in that, In step one, the mixture is sealed and fermented at 25 °C for 4 h.

4. The preparation method as described in claim 1, characterized in that, In step one, the yeast culture is prepared as follows: take 0.5~1.5 g of Angel high-temperature resistant brewing high-activity dry yeast, add 1000 mL of sterilized 3% white sugar solution, mix well, seal and place at room temperature for 10 h for activation, and then dilute 2~8 times to obtain the culture.

5. The preparation method according to claim 1, characterized in that, In step two, the concentration of mesophilic α-amylase is 0.10~0.25% w / w, and the concentration of saccharifying enzyme is 0.05~0.15% w / w.

6. The preparation method according to claim 1, characterized in that, In step two, the enzymatic hydrolysis time is 1.5 to 3 hours.

7. The preparation method according to claim 1, characterized in that, In step two, the pH of the solution is adjusted to 5.0-6.0 using 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide.

8. The preparation method according to claim 1, characterized in that, In step three, the concentration of the food-grade citric acid is 1.5~3.0% w / v; the acid hydrolysis is carried out by stirring at 37°C for 12 h.

9. The preparation method according to claim 1, characterized in that, In step three, the drying temperature is 60 ℃, the drying time is 12 h, and the powder is pulverized and passed through a 60-mesh sieve.

10. The preparation method according to any one of claims 1-9 yields Gracilaria powder with high water retention and low heavy metal content.

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