Rapid rehydration method for maintaining quality of dried beancurd sticks at high temperature

Abstract

The invention belongs to the technical field of food processing, and particularly relates to a rapid rehydration method for keeping the quality of dried beancurd sticks at high temperature. The rapid rehydration method comprises the following steps: (1) adding sodium chloride and an ascorbic acid compound into hot water at 60-70 DEG C, and uniformly dissolving to obtain a rehydration agent solution; and (2) adding the dried bean curd sticks into the rehydration agent solution in the step (1) for soaking and rehydration to obtain the rehydrated bean curd sticks. The rehydration method of the dried beancurd sticks is carried out at high water temperature of 60-70 DEG C, and compared with rehydration at normal temperature of 25 DEG C, the rehydration time of the dried beancurd sticks is shortened by 0.5-2 hours. According to the rehydration method disclosed by the invention, on the basis of not changing the traditional preparation process of the dried beancurd sticks, the aim of quickly rehydrating the dried beancurd sticks can be achieved through simple steps by taking the rehydration of the dried beancurd sticks as a starting point and adopting food additives with high acceptability of consumers, and indexes such as color, sense and texture after rehydration can be kept. The method has a good application prospect in the food industry and related fields.

Description

Technical Field

[0001] The present invention belongs to the technical field of food processing, and particularly relates to a rapid rehydration method for maintaining the quality of yuba at high temperatures. Background Art

[0002] Yuba is made from soybeans through processes such as bean selection, soaking, grinding, boiling, and skin peeling, and is formed by drying the protein-fat film that aggregates on the surface of soy milk. Yuba has a protein content as high as 45%-50% and a fat content of 25%-30%, with extremely high nutritional value and the reputation of "the meat among vegetables". In addition, yuba contains rich nutrients such as minerals, soy saponins, and amino acids. Its isoflavone content is 1.12-2.9 times higher than that of raw soybeans and tofu, and it has functions such as improving immunity, preventing blood vessel sclerosis, promoting bone development, antioxidation, and anti-iron deficiency anemia. As a traditional soy product, yuba is widely used in various foods due to its rich protein and unique taste. However, dried yuba often needs to be rehydrated before consumption. During the rehydration process, in addition to taking a long time, problems such as dull color and soft texture are likely to occur. Therefore, the rehydration process of dried yuba is a key step in determining the edible quality of yuba, directly affecting the nutrition, color, and taste of yuba and determining the ultimate experience of consumers. Some consumers will soak yuba in warm water to rehydrate it quickly. Although this method greatly shortens the rehydration time, the fading phenomenon and texture deterioration of yuba during high-temperature rehydration will be more obvious. Therefore, shortening the rehydration time of dried yuba and maintaining its quality such as nutrition, appearance, and taste are common technical problems in current yuba products.

[0003] Among the existing publicly disclosed patents, there are few patents on yuba rehydration. For example, Patent CN114287551A discloses a preservative for fresh yuba and its preparation method and a method for preparing fresh yuba. This method uses 10 5 -10 6After the Lactobacillus plantarum LY-78 at CFU / mL was activated and centrifuged, the precipitated cells were resuspended with sterile water to obtain a bacterial suspension of Lactobacillus plantarum LY-78, which was added to fresh yuba. This patent extended the shelf life and storage period of fresh yuba products. However, the operation steps were numerous, the raw material costs and requirements were restricted, and it was limited to fresh yuba products only. Most consumers have a higher acceptance of traditional dried yuba. Patent CN111345355B discloses a preparation method for quickly rehydrating yuba. The preparation process includes soaking soybeans, grinding soy milk, boiling soy milk, maintaining temperature to form yuba sheets, high-temperature dehydration drying, and packaging processes. It mainly adjusts the pH of the soy milk by adding edible sodium bicarbonate after boiling soy milk, and uses two-stage tunnel far-infrared drying for high-temperature dehydration drying to control the structure of dried yuba, so as to achieve the purpose of quick rehydration. However, this method has a complex process and high equipment requirements (requiring a high temperature of 140 - 150 °C); in addition, this method changes the traditional drying process of yuba. Due to the short drying time, the taste of this dried yuba may be poor. The inventors only focused on rehydration and did not pay attention to quality indicators such as texture.

[0004] In terms of rehydration of other products, there are often complex processes or the need to add exogenous substances during the production process of products to achieve the purpose of quick rehydration of products, which is itself unacceptable to consumers. For example, Patent CN110800911A discloses a preparation method for a soybean-water lactic acid bacteria dry rehydrating agent. The preparation process is to add soy milk to probiotics for fermentation, stir and process at a temperature of 70 - 75 °C to obtain a diluted probiotic coagulation liquid; add the probiotic coagulation liquid to the boiling soy milk to coagulate the soy milk into tofu, keep it warm and stand still, filter the clarified supernatant, add lemon juice, and then add the probiotic coagulation liquid for fermentation to obtain the soybean-water lactic acid bacteria dry rehydrating agent. This rehydrating agent shortens the soaking time of dried goods, but the production method is complex. The probiotics used include Bifidobacterium adolescentis, Lactobacillus bulgaricus, Bifidobacterium bifidum, Lactobacillus acidophilus, Lactobacillus plantarum, and yeast, with a wide variety and high cost, which is easily restricted for enterprise production. In this patent, this rehydrating agent is more suitable for dried goods with obvious flavors, which can remove miscellaneous flavors such as fishy and astringent tastes, so its application has certain limitations. For example, Patent CN104489668B discloses a preparation method for quickly rehydrating broad bean flowers, and additional rehydrating agents such as maltodextrin and sucrose are added during the production process, and at the same time, a more complex two-stage drying process is adopted; Patent CN106234564B discloses a method for low-frequency ultrasonic-assisted improvement of dehydration and rehydration of Nostoc commune, and this patent adopts an extremely complex preparation process such as low-frequency ultrasonic pretreatment, freezing, pulsed spouted low-frequency microwave vacuum freeze-drying, and hot air drying, and the inventors did not study the rehydration of the products. Summary of the Invention

[0005] Aiming at the disadvantages of long rehydration time at low temperature and deterioration of rehydration color and texture at high temperature for dried yuba, the purpose of the present invention is to provide a rapid rehydration method for maintaining the quality of yuba at high temperature. Without changing the traditional preparation process of dried yuba, starting from the rehydration of dried yuba, the present invention uses food additives with high consumer acceptance, and can achieve the purpose of rapid rehydration of dried yuba through simple steps, and can maintain indicators such as color, sensory properties and texture after rehydration.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A rapid rehydration method for maintaining the quality of yuba at high temperature, comprising the following steps:

[0008] (1) Add sodium chloride and ascorbic acid compound to hot water at 60-70°C and dissolve evenly to obtain a rehydration agent solution.

[0009] (2) Add dried yuba to the rehydration agent solution in step (1) for immersion rehydration to obtain rehydrated yuba.

[0010] Further, the ascorbic acid compound in step (1) is one or both of ascorbic acid and D-isoascorbic acid.

[0011] Further, the mass concentration of sodium chloride in the rehydration agent solution in step (1) is 1%-6%.

[0012] Further, the mass concentration of ascorbic acid compound in the rehydration agent solution in step (1) is 0.1%-0.4%.

[0013] Further preferably, the ascorbic acid compound in step (1) is ascorbic acid, and the mass concentration of ascorbic acid in the rehydration agent solution is 0.1%-0.4%.

[0014] More preferably, the ascorbic acid compound in step (1) is ascorbic acid, the mass concentration of sodium chloride in the rehydration agent solution is 1%, and the mass concentration of ascorbic acid is 0.1%.

[0015] Further preferably, the ascorbic acid compound in step (1) is D-isoascorbic acid, and the mass concentration of D-isoascorbic acid in the rehydration agent solution is 0.1%-0.3%.

[0016] More preferably, the ascorbic acid compound in step (1) is D-isoascorbic acid, the mass concentration of sodium chloride in the rehydration agent solution is 1%, and the mass concentration of D-isoascorbic acid is 0.2%.

[0017] Further, the time of immersion rehydration in step (2) is 15-30 min.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) The rehydration method of dried beancurd sticks of the present invention is carried out at a high water temperature of 60-70 °C. Compared with rehydration at room temperature of 25 °C, the rehydration time of beancurd sticks is shortened by 0.5-2 h.

[0020] (2) The present invention reduces the deterioration effect of high-temperature rehydration on the quality of beancurd sticks, ensuring that under the premise of not affecting the quality of beancurd sticks, the quality indicators such as color and texture are equal to or even exceed those of beancurd sticks rehydrated in normal temperature water at 25 °C.

[0021] (3) The present invention uses sodium chloride, ascorbic acid and D-isoascorbic acid as common food additives, which are low in price, easy to obtain and easily accepted by consumers; the concentration of the rehydrating agent solution prepared therefrom is appropriately selected and can be used in high-temperature beancurd stick rehydration to improve the problem of deterioration of beancurd stick rehydration quality (color fading and texture deterioration), and has good application prospects in the food industry and related fields. Specific Embodiments

[0022] The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto.

[0023] Example 1

[0024] A rapid rehydration method for maintaining the quality of beancurd sticks at high temperature, comprising the following steps:

[0025] (1) Add sodium chloride and ascorbic acid to hot water at 65 °C and dissolve evenly to obtain a rehydrating agent solution;

[0026] (2) Add dried beancurd sticks to the rehydrating agent solution in step (1) and soak for rehydration for 25 min to obtain rehydrated beancurd sticks.

[0027] In this example, the mass concentration of sodium chloride in the rehydrating agent solution was controlled to be 1%, and the mass concentrations of ascorbic acid were adjusted to 0.05%, 0.10%, 0.20%, 0.40% and 1.00% respectively. The color difference (ΔE value) and elongation at break of the obtained rehydrated beancurd sticks were measured. And the beancurd sticks rehydrated by soaking in a 1% sodium chloride rehydrating agent solution at 65 °C for 25 min, soaking in a 0.10% ascorbic acid rehydrating agent solution at 65 °C for 25 min, soaking in pure water at 25 °C for 2.5 h for rehydration and soaking in pure water at 65 °C for 25 min for rehydration were compared, and the results are shown in Table 1 below.

[0028] Table 1

[0029] Rehydrating agent solution ΔE value Elongation at break Condition of hard core after rehydration 1% sodium chloride + 0.05% ascorbic acid 21.3 0.51 No hard core 1% sodium chloride + 0.10% ascorbic acid 15.6 0.53 No hard core 1% sodium chloride + 0.20% ascorbic acid 18.5 0.66 No hard core 1% sodium chloride + 0.40% ascorbic acid 20.1 0.69 Slight hard core 1% sodium chloride + 1.00% ascorbic acid 17.1 0.78 Partial hard core 1% sodium chloride 19.9 0.64 No hard core 0.10% ascorbic acid 14.5 0.48 No hard core Pure water at 25°C 18.1 0.49 No hard core Pure water at 65°C 26.3 0.26 No hard core

[0030] Example 2

[0031] A rapid rehydration method for maintaining the quality of dried bean curd sticks at high temperatures, comprising the following steps:

[0032] (1) Add sodium chloride and D-isoascorbic acid to hot water at 65°C and dissolve evenly to obtain a rehydrating agent solution;

[0033] (2) Immerse dried bean curd sticks in the rehydrating agent solution obtained in step (1) for 25 minutes to obtain rehydrated bean curd sticks.

[0034] In this example, by controlling the mass concentration of sodium chloride in the rehydrating agent solution to be 1% and adjusting the mass concentration of D-isoascorbic acid to be 0.05%, 0.10%, 0.20%, 0.30% and 0.40% respectively. The color difference (ΔE value) and elongation at break of the obtained rehydrated bean curd sticks were measured. And a comparison was made with the bean curd sticks rehydrated by soaking in a 1% sodium chloride rehydrating agent solution at 65°C for 25 minutes, soaking in a 0.20% D-isoascorbic acid rehydrating agent solution at 65°C for 25 minutes, soaking in pure water at 25°C for 2.5 hours for rehydration and soaking in pure water at 65°C for 25 minutes for rehydration. The results are shown in Table 2 below.

[0035] Table 2

[0036] Rehydrating agent solution ΔE value Elongation at break Condition of hard core after rehydration 1% sodium chloride + 0.05% D-isoascorbic acid 17.9 0.46 No hard core 1% sodium chloride + 0.10% D-isoascorbic acid 15.6 0.50 No hard core 1% sodium chloride + 0.20% D-isoascorbic acid 12.6 0.54 No hard core 1% sodium chloride + 0.30% D-isoascorbic acid 11.1 0.68 Slight hard core 1% sodium chloride + 0.40% D-isoascorbic acid 10.7 0.75 Partial hard core 1% sodium chloride 19.9 0.64 No hard core 0.20% D-isoascorbic acid 14.5 0.48 No hard core Pure water at 25°C 18.1 0.49 No hard core Pure water at 65°C 26.3 0.26 No hard core

[0037] Example 3

[0038] A rapid rehydration method for maintaining the quality of dried bean curd sticks at high temperatures, comprising the following steps:

[0039] (1) Add sodium chloride and ascorbic acid to hot water at 65°C and dissolve evenly to obtain a rehydrating agent solution;

[0040] (2) Immerse dried bean curd sticks in the rehydrating agent solution obtained in step (1) for 25 minutes to obtain rehydrated bean curd sticks.

[0041] In this example, by adjusting the mass concentration of sodium chloride in the rehydrating agent solution to be 0.5%, 1.0%, 2.0%, 3.0%, 6.0% and 9.0% respectively and controlling the mass concentration of ascorbic acid to be 0.10%. The color difference (ΔE value) and elongation at break of the obtained rehydrated bean curd sticks were measured. The results are shown in Table 3 below.

[0042] Table 3

[0043] Rehydrating agent solution ΔE value Elongation at break Condition of hard core after rehydration 0.5% sodium chloride + 0.10% ascorbic acid 18.3 ― No hard core 1.0% sodium chloride + 0.10% ascorbic acid 15.6 0.53 No hard core 2.0% sodium chloride + 0.10% ascorbic acid 14.4 0.65 No hard core 3.0% sodium chloride + 0.10% ascorbic acid 14.2 0.68 No hard core 6.0% sodium chloride + 0.10% ascorbic acid 13.7 0.87 Small amount of hard core 9.0% sodium chloride + 0.10% ascorbic acid 9.9 ― Large amount of hard core

[0044] Note: "―" means that the rehydrated bean curd stick sample was too soft or too hard to measure the elongation at break.

[0045] The above research data show that compared with the rehydrated yuba rehydrated with pure water at 25°C for 2.5 h, the yuba rehydrated with pure water at 65°C for 25 min has a lighter color, softer texture and lower chewiness. In contrast, adding 0.10% ascorbic acid, 0.20% D-isoascorbic acid or 1% sodium chloride can improve the deterioration of color and texture during rehydration at 65°C to a certain extent; among them, ascorbic acid and D-isoascorbic acid mainly improve its fading, while sodium chloride mainly improves its texture characteristics and increases the chewiness of the rehydrated yuba.

[0046] Furthermore, in the compound system based on 1% sodium chloride, the concentration gradient of the compound ascorbic acid substances shows significant difference characteristics. As shown in Example 1, compared with rehydration with pure water at 25°C, when the concentration of ascorbic acid is 0.10%, the compounding effect with 1% sodium chloride is the best, and the color difference ΔE is reduced by 2.5±0.3 compared with the pure water group, and the anti-tensile strength is increased to 0.53±0.04 N / mm 2 , the yuba is well rehydrated, light yellow in color, and has good structural toughness. However, in the sample group with an ascorbic acid concentration of 0.05%, the texture of the rehydrated yuba shows a slight improvement, but the color improvement effect is weak, indicating that low-concentration ascorbic acid cannot effectively inhibit the fading of yuba at high temperatures; however, when the ascorbic acid concentration exceeds 0.20%, the color of the completely rehydrated yuba gradually fades, and the texture gradually hardens, and a slight hard core appears inside the yuba in the 0.40% ascorbic acid compounding group. In addition, the hard core rate of 1% sodium chloride + 1.00% ascorbic acid reaches more than 30%, and the rehydration effect becomes worse, resulting in a smaller color difference and an improved texture.

[0047] Example 2 shows that the law of compounding D-isoascorbic acid with sodium chloride is similar to that of compounding ascorbic acid with sodium chloride. The optimal concentration is 1% sodium chloride + 0.20% D-isoascorbic acid compounding, and the ΔE value is 12.6±0.1 at this time, and the anti-tensile strength reaches 0.54±0.02 N / mm 2 , and both the color and texture are better than those of pure water at 25°C. When the concentration of D-isoascorbic acid ≥ 0.30%, the color also becomes abnormally deep and the texture tends to be too tight. In addition, the 1% sodium chloride + 0.40% D-isoascorbic acid compounding group cannot be completely rehydrated, resulting in too dark a color and too tight a texture.

[0048] In Example 3, under the condition of fixing 0.10% ascorbic acid, there are obvious differences among different sodium chloride concentrations. Among them, the 1.0% sodium chloride compounding group performs the best. The yuba is light yellow and has excellent elasticity. After rehydration, the texture is tough and the elasticity is good. When the sodium chloride concentration is lower than 1.0%, the yuba is overly softened and fragile and cannot maintain its complete shape, so the elongation at break cannot be measured; when the concentration exceeds 6.0%, the osmotic pressure imbalance in the system causes the yuba to gradually have difficulty in rehydration, and its ΔE value and texture parameters are all abnormal data. The texture gradually becomes tight, inhibiting the normal rehydration of the yuba sample. In the compounding group of 9.0% sodium chloride + 0.10% ascorbic acid, most of the hard cores still remain after extending the rehydration time.

[0049] The research results confirm that the optimal concentration for the synergistic effect of sodium chloride and ascorbic acid is: 1.0% sodium chloride + 0.10% ascorbic acid, and the range of ascorbic acid concentration that can be tried is: 0.1% - 0.4%; the optimal concentration for the synergistic effect of sodium chloride and D-isoascorbic acid is: 1% sodium chloride + 0.20% D-isoascorbic acid, and the range of D-isoascorbic acid concentration that can be tried is: 0.1% - 0.3%. The concentration range of sodium chloride that can be added to improve the texture is within the range of 1% - 6%. Compounding modifiers for high-temperature rehydration within the above range can simultaneously achieve the dual improvement effects of color difference control and texture optimization.

[0050] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A rapid rehydration method for maintaining the quality of yuba at high temperature, characterized in that: The steps include: (1) adding sodium chloride and ascorbic acid compound into hot water at 60-70° C. and dissolving them uniformly to obtain a rehydrating agent solution; (2) adding the dried bean curd sticks into the rehydrating agent solution of step (1) to soak and rehydrate, thereby obtaining rehydrated bean curd sticks.

2. The rapid rehydration method for maintaining the quality of yuba at high temperature according to claim 1, characterized in that: The ascorbic acid compound in step (1) is one or both of ascorbic acid and D-isoascorbic acid.

3. The rapid rehydration method for maintaining the quality of yuba at high temperature according to claim 1, characterized in that: The mass concentration of sodium chloride in the rehydrating agent solution in step (1) is 1% to 6%.

4. The rapid rehydration method for maintaining the quality of yuba at high temperature according to claim 1, characterized in that: The mass concentration of the ascorbic acid compound in the rehydrating agent solution in step (1) is 0.1% to 0.4%.

5. The rapid rehydration method for maintaining the quality of yuba at high temperature according to claim 1, characterized in that: The ascorbic acid compound in step (1) is ascorbic acid, and the mass concentration of ascorbic acid in the rehydrating agent solution is 0.1% to 0.4%.

6. The rapid rehydration method for maintaining the quality of yuba at high temperature according to claim 5, characterized in that: The mass concentration of sodium chloride in the rehydrating agent solution is 1%, and the mass concentration of ascorbic acid is 0.1%.

7. The rapid rehydration method for maintaining the quality of yuba at high temperature according to claim 1, characterized in that: The ascorbic acid compound in step (1) is D-isoascorbic acid, and the mass concentration of D-isoascorbic acid in the rehydrating agent solution is 0.1% to 0.3%.

8. The rapid rehydration method for maintaining the quality of yuba at high temperature according to claim 7, characterized in that: The mass concentration of sodium chloride in the rehydrating agent solution is 1%, and the mass concentration of D-isoascorbic acid is 0.2%.

9. The rapid rehydration method for maintaining the quality of yuba at high temperature according to claim 1, characterized in that: The soaking and rehydration time in step (2) is 15 to 30 minutes.