A calcium alginate-silicon dioxide porous composite humidity-controlling material for food, and its preparation method and application

Abstract

The present invention relates to the field of food, and the present invention discloses a calcium alginate-silicon dioxide porous composite humidity-controlling material for food, and a preparation method and application thereof. The preparation method of the porous composite humidity-controlling material comprises the following steps: step one: preparing a sodium alginate solution; step two: mixing a sodium silicate solution with a sodium alginate solution; step three: dripping acetic acid, heating to generate a silica sol, adding sodium bicarbonate to react and form pores, and obtaining a porous sol liquid; step four: freezing the porous sol liquid to obtain a porous frozen block; step five: immersing the porous frozen block in a calcium lactate solution to generate a porous composite gel from the outside to the inside; step six: rinsing the porous composite gel and drying it. The composite humidity-controlling material obtained by the method of the present invention not only has excellent humidity-controlling ability, but also the shape of the product can be precisely controlled; the raw materials used for the composite humidity-controlling material of the present invention are highly safe, suitable for humidity control in a food storage environment, and conform to the concept of green development.

Description

Technical Field

[0001] The present invention relates to the field of food, and in particular to a calcium alginate-silicon dioxide porous composite humidity-controlling material for food, and a preparation method and application thereof. Background Art

[0002] Humidity is crucial for the storage of food, especially fruits. Currently, the control of humidity in common storage environments mainly relies on air conditioners and humidifiers. This method generally consumes a lot of energy. Other passive humidity control methods, such as desiccants, will cause public discussion on whether their ingredients are green and healthy. Therefore, a completely healthy and energy-saving humidity control material is needed, and sodium alginate has begun to enter the public eye.

[0003] Currently, sodium alginate is widely used in biocompatible materials. For example, sodium alginate is often used as a drug because of its anticoagulant, lipid-lowering and blood viscosity-lowering effects. In addition, sodium alginate has many other uses, including industrial applications, and can be made into various forms of hemostatic agents such as alginate, including hemostatic sponges, hemostatic gauze, hemostatic membranes, scald gauze, spray hemostatic agents, etc. In the food field, as a food additive, for example, adding sodium alginate to products such as bread and pastries can improve the uniformity and water retention of the internal tissue of the product and extend the storage time. However, its application in maintaining humidity in the food environment is still a blank. Summary of the Invention

[0004] To address the above technical issues, the present invention provides a porous calcium alginate-silica composite humidity-control material for food, its preparation method, and its application. The composite humidity-control material produced by this method not only exhibits excellent humidity-control capabilities but also allows for precise control of its shape. The raw materials used in this composite humidity-control material are highly safe and suitable for humidity control in food storage environments, particularly fruits and vegetables, aligning with the concept of green development.

[0005] The specific technical solutions of the present invention are:

[0006] In a first aspect, the present invention provides a calcium alginate-silicon dioxide porous composite humidity-controlling material for food, which has a porous calcium alginate-silicon dioxide composite gel as a skeleton and is in the form of a porous block.

[0007] In a second aspect, the present invention provides a method for preparing a sodium alginate-dioxide porous composite humidity-controlling material for food, comprising the following steps:

[0008] Step 1: Dissolve 1-2 parts of sodium alginate in 100 parts of water in a water bath and continue stirring until it is completely dissolved to form a viscous solution.

[0009] Step 2: Dissolve 1 to 3 parts of zero-hydrated sodium silicate in 50 parts of water, mix with the viscous solution obtained in step 1, and stir thoroughly.

[0010] Step 3: Take 15-25 parts of acetic acid and add it dropwise to the mixed solution obtained in step 2 to react with zero-hydrated sodium silicate to generate silicic acid, and then heat and stir in a water bath to hydrolyze the silicic acid into sol-like silicon dioxide.

[0011] Step 3: Take 15-25 parts of acetic acid and add it dropwise to the mixed solution obtained in step 2 to react with zero-hydrated sodium silicate to produce silicic acid. Then, heat and stir in a water bath to hydrolyze the silicic acid into sol-like silicon dioxide. Then, add 4-8 parts of sodium bicarbonate to the system and stir evenly. After reacting with the remaining acetic acid, a porous sol solution is obtained.

[0012] In step three, acetic acid first reacts with zero-hydrated sodium silicate to produce silicic acid. During subsequent heating in a water bath, the silicic acid decomposes into a silica sol that adheres to the sodium alginate, forming a composite of the two. Sodium bicarbonate is then added, reacting with residual acetic acid to produce a large amount of gas. This gas escapes, forming numerous pores, resulting in a viscous, porous sol.

[0013] Step 4: The porous sol obtained in step 3 is placed into a mold of appropriate shape and subjected to freezing treatment to obtain a porous frozen block.

[0014] Step 5: Take 3 to 6 parts of calcium lactate and stir them thoroughly to dissolve in 100 parts of water. Immerse the frozen block prepared in step 4 in the calcium lactate solution. As the porous frozen block gradually dissolves from the outside to the inside, sodium alginate reacts with calcium lactate to gradually form a porous composite gel of the target shape from the outside to the inside.

[0015] In the prior art, it is difficult to customize calcium alginate gel products into special shapes. If the sol is placed in a mold before forming a gel, and then a cross-linking agent is added to convert it into a gel, the external sodium alginate will first contact the cross-linking agent and convert it into a gel during this process. However, since the external sodium alginate that first contacts the cross-linking agent lacks internal skeleton support, the converted gel is easy to collapse and difficult to shape, especially for porous gels, which is more detrimental to the shaping of the porous structure. On the other hand, the gel formed first on the outside will hinder the cross-linking agent from penetrating into the interior of the sodium alginate, resulting in the internal sodium alginate being unable to be completely converted into a gel. If the gel is processed into a special shape by physical methods after it is formed, the processing of special shapes is more difficult due to the soft texture of the calcium alginate gel.

[0016] To this end, the present invention adopts an improved scheme of first shaping and then cross-linking and curing. After obtaining the sodium alginate-silicon dioxide composite sol in step three, it is transferred to a mold and frozen, and then the frozen block is immersed in a calcium lactate solution. During this process, the frozen block is gradually dissolved from the outside to the inside, and the sodium alginate reacts with the calcium lactate to gradually generate a composite gel of the target shape from the outside to the inside. Since the method is to obtain a solid-state frozen block in advance, even if the composite sol on the surface is first converted into a gel, the gel formed first is not easy to collapse under the support of the internal frozen block as a skeleton; and since the frozen block itself is also porous, what is formed on the outside is a porous gel, which can reduce the cross-linking agent's penetration resistance to the inside of the frozen block, and the porous gel is also more conducive to the humidification effect of the material. Therefore, according to the method of the present invention, not only can a composite gel with excellent humidification ability be obtained, but it can also be customized to any shape.

[0017] Step 6: Rinse the porous composite gel obtained in step 5 with deionized water and dry it to obtain a calcium alginate-silicon dioxide porous composite humidity-controlling material for food. The rinsing process can wash away impurities.

[0018] The above parts are all parts by weight.

[0019] Preferably, in step 1, the water bath temperature is 80-100° C., and stirring is continued for 20-30 minutes.

[0020] During this process, the 80-100°C water bath is used to accelerate the dissolution of sodium alginate.

[0021] Preferably, in step 2, the temperature in the water bath is maintained at 80-100° C. during stirring.

[0022] During this process, the water bath is kept at 80-100°C to maintain the stability of the sodium alginate solution.

[0023] Preferably, in step three, the water bath heating and stirring temperature is 80-100° C., and the time is 20-30 min.

[0024] Preferably, in step five, 3 to 6 parts of calcium lactate and 0.1 to 1.5 parts of potassium sulfate are dissolved in 100 parts of water with thorough stirring.

[0025] The present invention has found that the addition of potassium sulfate can further improve the moisture absorption rate of the porous composite humidity-controlling material, but it will reduce the final moisture absorption rate of the material. Therefore, the comprehensive addition amount needs to be strictly limited.

[0026] Preferably, in step six, the drying conditions are: 60-80° C., 3-6 h.

[0027] In a third aspect, the present invention provides the use of the above-mentioned sodium alginate-silicon dioxide porous composite humidity-controlling material in maintaining the humidity of a food environment.

[0028] Compared with the prior art, the present invention has the following technical effects:

[0029] (1) The raw materials used in the composite humidity-controlling material of the present invention are generally safe, and therefore suitable for controlling the humidity of food storage environments, especially fruits and vegetables, in line with the concept of green development.

[0030] (2) The composite humidity-controlling material prepared by the method of the present invention not only has excellent humidity-controlling ability (excellent moisture absorption rate and moisture absorption capacity), but also the shape of the product can be more accurately controlled during the preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a test chart of moisture absorption rate of different samples in Example 1;

[0032] Figure 2 This is a test chart of the environmental humidity control capabilities of different samples in Example 1. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the embodiments.

[0034] Example 1

[0035] 1) Dissolve 1.5 g of sodium alginate in 100 mL of water at 90°C and stir continuously for 25 min until it is completely dissolved to form a viscous solution.

[0036] 2) Dissolve 2 g of zero-hydrated sodium silicate in 50 mL of water, and mix it with the solution prepared in step 1) and stir thoroughly until completely mixed. Keep the water bath at 90° C. during this process.

[0037] 3) 20 g of acetic acid was slowly added dropwise to the mixed solution from step 2) using a rubber-tipped dropper, and the mixture was heated and stirred at 90° C. for 20 to 30 minutes. 6 g of sodium bicarbonate was then added to the system and stirred evenly. The solution reacted with the remaining acetic acid to obtain a porous sol solution.

[0038] 4) The porous sol obtained in step 3) is placed in a mold, and transferred to an ultra-low temperature refrigerator to be frozen into a cube-shaped porous frozen block.

[0039] 5) 4.5 g of calcium lactate and 0, 0.5, 1.0, and 1.5 g of potassium sulfate were thoroughly stirred and dissolved in 100 mL of water. The porous frozen block prepared in step 4) was placed in the calcium lactate solution. As the porous frozen block gradually dissolved from the outside to the inside, porous gels were also generated from the outside to the inside, thereby obtaining four porous gels with different potassium sulfate contents.

[0040] 6) The porous gel obtained in step 5) was rinsed with deionized water several times and placed in an oven at 70° C. for 4.5 hours to obtain the product.

[0041] Four samples from Example 1 (7.5 g each) were placed in a constant temperature and humidity chamber set at 25°C and 55% humidity. The samples were allowed to stand until the mass difference between two weighings within one hour was no more than 1%. Samples with potassium sulfate additions of 0, 0.5, 1, and 1.5 g were labeled A, B, C, and D.

[0042] like Figure 1 As shown, the single porous composite humidity-control material has an excellent moisture absorption rate and final moisture absorption rate. Adding potassium sulfate further accelerates the moisture absorption rate of the material, but reduces the final moisture absorption rate. Therefore, considering all factors, the addition amount of 0.5g is the best.

[0043] As for the humidity control performance of the sample, 0.15 g of the sample of Example 1 was placed in a sealed box of 60*45*42 mm to test its ability to regulate the environment.

[0044] Depend on Figure 2 It can be seen that the single porous composite humidity-controlling material has excellent humidity-controlling ability, and the performance is further improved by adding potassium sulfate. Taking all factors into consideration, the addition of 0.5g potassium sulfate has the best improvement on performance. The addition of potassium sulfate will accelerate the moisture absorption efficiency of the material, but due to its own properties, it will reduce the overall moisture capacity of the material.

[0045] Example 2

[0046] 1) Dissolve 1 g of sodium alginate in 100 mL of water at 80°C and stir continuously for 20 min until it is completely dissolved to form a viscous solution.

[0047] 2) Dissolve 1 g of zero-hydrated sodium silicate in 50 mL of water, and mix it with the solution prepared in step 1) and stir thoroughly until completely mixed. Maintain a water bath at 80° C. during this process.

[0048] 3) 15 g of acetic acid was slowly added dropwise to the mixed solution from step 2) using a rubber-tipped dropper, and the mixture was heated and stirred at 90° C. for 20 min. Then, 4 g of sodium bicarbonate was added to the system and stirred evenly. After reaction with the remaining acetic acid, a porous sol solution was obtained.

[0049] 4) The porous sol obtained in step 3) is placed into a mold of an appropriate shape and transferred to an ultra-low temperature refrigerator to be frozen into a certain shape.

[0050] 5) 3 g of calcium lactate was dissolved in 100 mL of water with thorough stirring. The porous frozen block prepared in step 4) was placed in the calcium lactate solution. As the porous frozen block gradually dissolved from the outside to the inside, a porous gel was also generated from the outside to the inside, thereby obtaining a porous gel.

[0051] 6) The porous gel obtained in step 5) was rinsed with deionized water several times and placed in an oven at 60° C. for 6 hours to obtain the product.

[0052] Example 3

[0053] 1) Dissolve 2 g of sodium alginate in 100 mL of water at 100°C and stir continuously for 30 min until the solution is completely dissolved to form a viscous solution.

[0054] 2) Dissolve 3 g of zero-hydrated sodium silicate in 50 mL of water, and mix the solution prepared in step 1) with the solution and stir thoroughly until completely mixed. Keep the temperature in a 100° C. water bath during the process.

[0055] 3) 25 g of acetic acid was slowly added dropwise to the mixed solution from step 2) using a rubber-tipped dropper, and the mixture was heated and stirred at 90° C. for 30 min. 8 g of sodium bicarbonate was then added to the system and stirred evenly. The solution reacted with the remaining acetic acid to obtain a porous sol solution.

[0056] 4) The mixed solution obtained in step 3) is placed into a mold of an appropriate shape and transferred to an ultra-low temperature refrigerator to be frozen into a certain shape.

[0057] 5) 6 g of calcium lactate was dissolved in 100 mL of water with thorough stirring. The porous frozen block prepared in step 4) was placed in the calcium lactate solution. As the porous frozen block gradually dissolved from the outside to the inside, a porous gel was also generated from the outside to the inside, thereby obtaining a porous gel.

[0058] 6) The porous gel obtained in step 5) was rinsed with deionized water several times and placed in an oven at 80° C. for 3 h to obtain the product.

[0059] Unless otherwise specified, the raw materials and equipment used in the present invention are commonly used in the art; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0060] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a calcium alginate-silicon dioxide porous composite humidity-controlling material for food, characterized by: The calcium alginate-silicon dioxide porous composite humidity-controlling material for food has a porous calcium alginate-silicon dioxide composite gel as a skeleton and is in the form of a porous block; It includes the following steps: Step 1: Dissolve 1-2 parts of sodium alginate in 100 parts of water in a water bath and continue stirring until it is completely dissolved to form a viscous solution. Step 2: Dissolve 1 to 3 parts of zero-hydrated sodium silicate in 50 parts of water, mix with the viscous solution obtained in step 1, and stir thoroughly; Step 3: Take 15-25 parts of acetic acid and add it dropwise to the mixed solution obtained in step 2 to react with zero-hydrated sodium silicate to produce silicic acid. Then, heat and stir in a water bath to hydrolyze the silicic acid into sol-like silicon dioxide. Then, add 4-8 parts of sodium bicarbonate to the system and stir evenly. After reaction with the remaining acetic acid, a porous sol solution is obtained. Step 4: Pour the porous sol obtained in step 3 into a mold of appropriate shape and freeze it to obtain a porous frozen block; Step 5: Take 3-6 parts of calcium lactate and stir them thoroughly to dissolve in 100 parts of water. Immerse the porous frozen block prepared in step 4 in the calcium lactate solution. As the porous frozen block gradually dissolves from the outside to the inside, the sodium alginate reacts with the calcium lactate to gradually form a porous composite gel of the target shape from the outside to the inside. Step 6: Rinse the porous composite gel obtained in step 5 with deionized water and dry it to obtain a calcium alginate-silicon dioxide porous composite humidity-controlling material for food; The above parts are all parts by weight.

2. The preparation method according to claim 1, wherein: In step 1, the water bath temperature is 80-100°C and stirring is continued for 20-30 minutes.

3. The preparation method according to claim 1, wherein: In step 2, the temperature in the water bath is maintained at 80-100°C during stirring.

4. The preparation method according to claim 1, wherein: In step 3, the water bath is heated and stirred at a temperature of 80-100°C for 20-30 minutes.

5. The preparation method according to claim 1, wherein: In step 5, 3-6 parts of calcium lactate and 0.1-1.5 parts of potassium sulfate are dissolved in 100 parts of water by thorough stirring.

6. The preparation method according to claim 1, wherein: In step six, the drying conditions are: 60-80°C, 3-6h.

7. Use of the calcium alginate-silicon dioxide porous composite humidity-controlling material for food obtained by the preparation method according to any one of claims 1 to 6 in maintaining the humidity of a food environment.

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