Composite color protection method for inhibiting red heart of canned water chestnut

Abstract

The invention belongs to the technical field of food preservation, and particularly relates to a composite color protection method for inhibiting red heart of canned water chestnut, which is characterized by comprising the following steps: (1) pretreatment; (2) fixing color, curing and rinsing; and (3) canning and sterilizing. According to the composite color protection method disclosed by the invention, through organic combination of pretreatment, color fixation and enzyme deactivation and long-acting anti-oxidation and corrosion prevention in the tank, systematic blocking of a plurality of mutagenic paths such as enzymatic browning, metal ion catalysis and oxyradical attack is realized, so that the color stability and shelf life of the canned water chestnuts are remarkably improved; meanwhile, the sensory quality and the edible safety of the product are considered, and the product has outstanding synergy, durability and industrial application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of food preservation, and particularly relates to a compound color protection method for inhibiting the red heart of canned Eleocharis tuberosa. BACKGROUND

[0002] Eleocharis tuberosa, also known as water chestnut or black taro, is a perennial aquatic herb of the family Cyperaceae. Due to its unique flavor and good medicinal value, it has broad application prospects in the food processing field. As it is difficult to clean and peel, hygienic and convenient processing products of Eleocharis tuberosa are increasingly favored by consumers. With the rapid growth of demand for instant healthy food in the consumer market, the processing industry of Eleocharis tuberosa is facing the demand for technological innovation to improve quality and efficiency. Canned Eleocharis tuberosa is the most important processing product of Eleocharis tuberosa on the international market, and its export volume has been increasing year by year, occupying a large market share. However, the color of canned Eleocharis tuberosa deteriorates during heat processing, resulting in a red heart phenomenon, which seriously affects product quality and has become a key bottleneck problem restricting the development of the industry.

[0003] The red heart phenomenon of canned Eleocharis tuberosa is different from the enzymatic browning of other fruit and vegetable cans. The traditional color protection strategy based on polyphenol oxidase inhibition has obvious limitations and cannot effectively protect the color. Our research found that the red heart phenomenon of Eleocharis tuberosa is essentially a multi-path co-color effect in a complex non-enzymatic reaction system, involving multi-level interaction of Maillard reaction intermediates and terpenes (genipin, etc.) and phenolic substances (proanthocyanidins, catechins, etc.). This multi-component synergistic color mechanism raises higher requirements for the development of new color protection technology. Therefore, the design of the color protection agent needs to consider the synergy of free radical scavenging, metal ion chelation, pH regulation, and other functions. It is necessary to block the carbonyl reaction path, inhibit the oxidation and polymerization of phenolic substances, and the condensation reaction of terpenes-amino acids, and to select the appropriate color protection agent formula to effectively inhibit the red heart of Eleocharis tuberosa. At present, the food color protection agent technology has made significant progress in the field of browning inhibition of fruit and vegetable products, but there is no report on the inhibition technology for the red heart of canned Eleocharis tuberosa. SUMMARY

[0004] In order to achieve the above-mentioned application purposes, the technical scheme adopted by the application is as follows: A compound color protection method for inhibiting the red heart of canned Eleocharis tuberosa, comprising the following steps: (1) Pretreatment: select tender and crisp, thin skin, uniform fruit shape and non-damaged Eleocharis tuberosa, cut off the main lateral buds and roots, and perform peeling treatment to obtain peeled Eleocharis tuberosa; (2) Fixation, curing and rinsing: the peeled horse hoof obtained in step (1) is soaked in a first color protection liquid, the first color protection liquid comprising a stabilizer, the stabilizer consisting of cysteine and disodium EDTA; the temperature of the soaking is 48-52℃, and the time of the soaking is 20-40 minutes; then the peeled horse hoof is heated to 85-90℃ together with the first color protection liquid and maintained for 3-5 minutes for curing; after the curing is completed, the horse hoof is taken out, rinsed quickly with cold water, and then drained; (3) Canning and sterilization: the drained horse hoof in step (2) is canned, injected with a second color protection liquid, sealed, and subjected to sterilization treatment to obtain a finished product of horse hoof cans; wherein the second color protection liquid comprises tea polyphenol palmitate, rosemary extract, D-erythorbic acid and a pH adjuster.

[0005] Further, in step (2), the mass concentration of the stabilizer in the first color protection liquid is 1%-3%, and the mass ratio of cysteine to disodium EDTA in the stabilizer is (1:1)-(3:2).

[0006] Further, in step (2), the first color protection liquid further comprises sodium phytate, and the mass concentration of the sodium phytate in the first color protection liquid is 0.03%-0.08%.

[0007] Further, in step (2), the soaking operation is first carried out under a vacuum condition of-0.06MPa to-0.09MPa for 5-8 minutes, and then restored to normal pressure and continued to complete the remaining soaking time.

[0008] Further, in step (3), the mass concentration of the tea polyphenol palmitate in the second color protection liquid is 0.1%-0.3%.

[0009] Further, in step (3), the mass concentration of the rosemary extract in the second color protection liquid is 2%-5%, and the mass concentration of the D-erythorbic acid in the second color protection liquid is 0.1%-0.3%.

[0010] Further, in step (3), the pH adjuster is a citric acid-sodium citrate buffer solution, and after being adjusted by the citric acid-sodium citrate buffer solution, the pH value of the second color protection liquid is 4.0-4.5.

[0011] Further, in step (3), the sterilization treatment adopts a gradient high-temperature sterilization mode, specifically: first sterilization at 105±1℃ for 14-16 minutes, and then sterilization at 121±1℃ for 9-11 minutes.

[0012] Compared with the prior art, the present application has the following advantages: (1) The present application starts from the source of "red heart" and carries out precise and phased intervention. In the first phase of color fixing and curing treatment, cysteine in the first color protection liquid forms a synergistic combination with disodium EDTA: cysteine as a reducing agent directly inhibits the activity of polyphenol oxidase and reduces the intermediate product of browning, while disodium EDTA chelates metal ions such as copper and iron to eliminate enzyme activity catalysts and oxidation reaction mediators. With vacuum soaking process, the color protection ingredients penetrate deeply, and then heat is applied to completely inactivate the enzyme, which fundamentally prevents the occurrence of enzymatic browning in the early processing.

[0013] (2) The present application innovatively adopts the "internal and external double color protection" strategy to provide long-term protection for the product. The second color protection liquid injected during canning constitutes the key second line of defense. Among them, tea polyphenol palmitate and rosemary extract as a powerful natural liposoluble antioxidant can effectively scavenge free radicals generated during sterilization and storage, and inhibit non-enzymatic browning caused by lipid oxidation, which is difficult to achieve by traditional water-soluble color protection agents. At the same time, D-erythorbic acid and the acidic environment adjusted by the citric acid system together maintain the persistent reducing state and low pH conditions in the can, and comprehensively inhibit various browning reactions.

[0014] (3) The present application focuses on the overall improvement of synergy and product quality in process design. The gradient high-temperature sterilization process ensures commercial sterility while reducing the damage to color and texture caused by single high temperature, better preserving the crisp and tender taste of lotus root. Most of the color protection ingredients used are natural or recognized safe additives, which significantly improve the safety of the product, avoid the residual problem that may be caused by traditional sulfite color protection, and meet the modern clean label trend.

[0015] In summary, the composite color protection method of the present application realizes the systematic blocking of enzymatic browning, metal ion catalysis, oxidative radical attack and other multiple pathogenic pathways through pretreatment color fixing and enzyme inactivation combined with long-term antioxidant and preservation in the can. It not only significantly improves the color stability and shelf life of lotus root cans, but also takes into account the sensory quality and edible safety of the product, with outstanding synergy, durability and industrial application value. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the red heart effect picture of lotus root cans of example 1 and comparative example 1 to comparative example 5 after high-temperature sterilization. DETAILED DESCRIPTION

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 (1) Pretreatment: Select tender, crisp, thin-skinned, uniformly shaped, and undamaged water chestnuts, remove the main and lateral buds and roots, and peel them to obtain peeled water chestnuts. (2) Color fixing, curing and rinsing: The peeled water chestnuts obtained in step (1) are soaked in the first color-protecting solution, with the amount of solution sufficient to completely submerge the water chestnuts. The first color-protecting solution contains a stabilizer composed of cysteine ​​and disodium EDTA in a mass ratio of 1:1, and the mass concentration of the stabilizer in the first color-protecting solution is 1%. The first color-protecting solution also contains sodium phytate with a mass concentration of 0.03%. The soaking operation was first carried out under a vacuum of -0.06 MPa for 5 minutes, then restored to normal pressure, and continued to soak at 48°C for a total soaking time of 20 minutes. The peeled water chestnuts were then heated together with the first color-protecting liquid to 85°C and maintained for 3 minutes to ripen. After the water chestnuts have matured, remove them, rinse them quickly with cold water, and then drain them. (3) Canning and sterilization: After draining the water chestnuts in step (2), put them into a jar, pour in the second color-protecting liquid until it completely covers the water chestnuts, and then seal the jar. The second color-protecting liquid contains tea polyphenol palmitate, rosemary extract, D-isoascorbic acid and pH adjuster. The concentration of tea polyphenol palmitate in the second color-protecting solution is 0.1%, the concentration of rosemary extract is 2%, and the concentration of D-isoascorbic acid is 0.1%. The pH adjuster is a citrate-sodium citrate buffer solution, which adjusts the pH of the second color-protecting solution to 4.0.

[0019] The sealed products are sterilized using a gradient high-temperature sterilization method: first, sterilization is carried out at 105±1℃ for 14 minutes, followed by sterilization at 121±1℃ for 9 minutes to obtain the finished water chestnut canned product.

[0020] Example 2 (1) Pretreatment: Select tender, crisp, thin-skinned, uniformly shaped, and undamaged water chestnuts, remove the main and lateral buds and roots, and peel them to obtain peeled water chestnuts. (2) Color fixing, curing and rinsing: The peeled water chestnuts obtained in step (1) are soaked in the first color-protecting solution, with the amount of color-protecting solution being sufficient to completely submerge the peeled water chestnuts; the first color-protecting solution contains a stabilizer, which is composed of cysteine ​​and disodium EDTA in a mass ratio of 2:1, and the mass concentration of the stabilizer in the first color-protecting solution is 1.5%; the first color-protecting solution also contains sodium phytate, with a mass concentration of 0.05%; The soaking operation was first carried out under a vacuum of -0.075 MPa for 6 minutes, then restored to atmospheric pressure, and continued to soak at 50°C for a total soaking time of 25 minutes. The peeled water chestnuts were then heated together with the first color-protecting liquid to 87°C and maintained for 4 minutes to ripen. After the water chestnuts have matured, remove them, rinse them quickly with cold water, and then drain them. (3) Canning and sterilization: After draining the water chestnuts in step (2), put them into a jar, pour in the second color-protecting liquid until it completely covers the water chestnuts, and then seal the jar. The second color-protecting liquid contains tea polyphenol palmitate, rosemary extract, D-isoascorbic acid and pH adjuster. The concentration of tea polyphenol palmitate in the second color-protecting solution is 0.15%, the concentration of rosemary extract is 3%, and the concentration of D-isoascorbic acid is 0.15%. The pH adjuster is citrate-sodium citrate buffer solution, and after adjustment, the pH value of the second color-protecting solution is 4.2. The sealed products are sterilized using a gradient high-temperature sterilization method: first, sterilization is carried out at 105±1℃ for 15 minutes, followed by sterilization at 121±1℃ for 10 minutes to obtain the finished water chestnut canned product.

[0021] Example 3 (1) Pretreatment: Select tender, crisp, thin-skinned, uniformly shaped, and undamaged water chestnuts, remove the main and lateral buds and roots, and peel them to obtain peeled water chestnuts. (2) Color fixing, curing and rinsing: The peeled water chestnuts obtained in step (1) are soaked in the first color-protecting solution, with the amount of color-protecting solution being sufficient to completely submerge the peeled water chestnuts; the first color-protecting solution contains a stabilizer, which is composed of cysteine ​​and disodium EDTA in a mass ratio of 3:2, and the mass concentration of the stabilizer in the first color-protecting solution is 2.0%; the first color-protecting solution also contains sodium phytate, with a mass concentration of 0.06%; The soaking operation was first carried out under a vacuum of -0.08 MPa for 7 minutes, then restored to atmospheric pressure, and continued to soak at 52°C for a total soaking time of 30 minutes. The peeled water chestnuts were then heated together with the first color-protecting liquid to 88°C and maintained for 4 minutes to ripen. After the water chestnuts have matured, remove them, rinse them quickly with cold water, and then drain them. (3) Canning and sterilization: After draining the water chestnuts in step (2), put them into a jar, pour in the second color-protecting liquid until it completely covers the water chestnuts, and then seal the jar. The second color-protecting liquid contains tea polyphenol palmitate, rosemary extract, D-isoascorbic acid and pH adjuster. The concentration of tea polyphenol palmitate in the second color-protecting solution is 0.2%, the concentration of rosemary extract is 3.5%, and the concentration of D-isoascorbic acid is 0.2%. The pH adjuster is citrate-sodium citrate buffer solution, after which the pH value of the second color-protecting solution is 4.3. The sealed products are sterilized using a gradient high-temperature sterilization method: first, sterilization is carried out at 105±1℃ for 15 minutes, followed by sterilization at 121±1℃ for 10 minutes to obtain the finished water chestnut canned product.

[0022] Example 4 (1) Pretreatment: Select tender, crisp, thin-skinned, uniformly shaped, and undamaged water chestnuts, remove the main and lateral buds and roots, and peel them to obtain peeled water chestnuts. (2) Color fixing, curing and rinsing: The peeled water chestnuts obtained in step (1) are soaked in the first color-protecting solution, with the amount of color-protecting solution being sufficient to completely submerge the peeled water chestnuts; the first color-protecting solution contains a stabilizer, which is composed of cysteine ​​and disodium EDTA in a mass ratio of 3:2, and the mass concentration of the stabilizer in the first color-protecting solution is 2.5%; the first color-protecting solution also contains sodium phytate, with a mass concentration of 0.07%; The soaking operation was first carried out under a vacuum of -0.085 MPa for 7 minutes, then restored to atmospheric pressure, and continued to soak at 52°C for a total soaking time of 35 minutes. The peeled water chestnuts were then heated together with the first color-protecting liquid to 89°C and maintained for 5 minutes to ripen. After the water chestnuts have matured, remove them, rinse them quickly with cold water, and then drain them. (3) Canning and sterilization: After draining the water chestnuts in step (2), put them into a jar, pour in the second color-protecting liquid until it completely covers the water chestnuts, and then seal the jar. The second color-protecting liquid contains tea polyphenol palmitate, rosemary extract, D-isoascorbic acid and pH adjuster. The concentration of tea polyphenol palmitate in the second color-protecting solution is 0.25%, the concentration of rosemary extract is 4%, and the concentration of D-isoascorbic acid is 0.25%. The pH adjuster is citrate-sodium citrate buffer solution, and after adjustment, the pH value of the second color-protecting solution is 4.4. The sealed products are sterilized using a gradient high-temperature sterilization method: first, sterilization is carried out at 105±1℃ for 16 minutes, followed by sterilization at 121±1℃ for 10 minutes to obtain the finished water chestnut canned product.

[0023] Example 5 (1) Pretreatment: Select tender, crisp, thin-skinned, uniformly shaped, and undamaged water chestnuts, remove the main and lateral buds and roots, and peel them to obtain peeled water chestnuts. (2) Color fixing, curing and rinsing: The peeled water chestnuts obtained in step (1) are soaked in the first color-protecting solution, with the amount of color-protecting solution being sufficient to completely submerge the peeled water chestnuts; the first color-protecting solution contains a stabilizer, which is composed of cysteine ​​and disodium EDTA in a mass ratio of 3:2, and the mass concentration of the stabilizer in the first color-protecting solution is 3%; the first color-protecting solution also contains sodium phytate, with a mass concentration of 0.08%; The soaking operation was first carried out under a vacuum of -0.09 MPa for 8 minutes, then restored to atmospheric pressure, and continued to soak at 52°C for a total soaking time of 40 minutes. The peeled water chestnuts were then heated together with the first color-protecting liquid to 90°C and maintained for 5 minutes to ripen. After the water chestnuts have matured, remove them, rinse them quickly with cold water, and then drain them. (3) Canning and sterilization: After draining the water chestnuts in step (2), put them into a jar, pour in the second color-protecting liquid until it completely covers the water chestnuts, and then seal the jar. The second color-protecting liquid contains tea polyphenol palmitate, rosemary extract, D-isoascorbic acid and pH adjuster. The concentration of tea polyphenol palmitate in the second color-protecting solution is 0.3%, the concentration of rosemary extract is 5%, and the concentration of D-isoascorbic acid is 0.3%. The pH adjuster is citrate-sodium citrate buffer solution, after which the pH value of the second color-protecting solution is 4.5. The sealed products are sterilized using a gradient high-temperature sterilization method: first, sterilization is carried out at 105±1℃ for 16 minutes, followed by sterilization at 121±1℃ for 11 minutes to obtain the finished water chestnut canned product.

[0024] To illustrate the technical effects of this invention, the inventors set up the following comparative examples and conducted tests, with the results as follows: Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the first color-protecting solution was replaced with a traditional color-protecting agent, and sterile water with adjusted pH was injected (without adding any components of the second color-protecting solution). The specific steps are as follows: (1) Pretreatment: Same as in Example 1; (2) Color protection and ripening: Peeled water chestnuts are soaked in a 0.2% sodium sulfite aqueous solution and soaked at 48°C under normal pressure for 20 minutes (without vacuum treatment), and then heated to 85°C and maintained for 3 minutes; (3) Rinsing, canning and sterilization: After aging, rinse with cold water and drain, put into cans, inject sterile water (pH adjusted to 4.0), seal the cans and use the same gradient high temperature sterilization process as in Example 1.

[0025] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the first color-protecting liquid is not used, and only water is used for color-fixing and curing treatment.

[0026] The specific steps are as follows: (1) Pretreatment: Same as in Example 1; (2) Cooking treatment: Place the peeled water chestnuts in clean water and treat them under vacuum conditions of -0.06 MPa for 5 minutes. After restoring normal pressure, continue soaking at 48℃ for a total time of 20 minutes. Then heat to 85℃ and maintain for 3 minutes. (3) Subsequent processes: rinsing, canning (using the second color-protecting liquid of Example 1), and sterilization are the same as in Example 1.

[0027] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that no second color-protecting liquid is added during canning; only pH-adjusting water is injected.

[0028] Specifically as follows: (1) Pretreatment, color fixing and curing: exactly the same as in Example 1 (using a first color-protecting solution containing stabilizer and sodium phytate). (2) Canning and sterilization: After the water chestnuts are drained, they are placed into cans and sterile water is added (the pH is adjusted to 4.0 with citric acid-sodium citrate buffer solution, without adding any color-protecting ingredients). After sealing the cans, the sterilization process is the same as in Example 1.

[0029] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the vacuum stage is omitted during the first color-protecting liquid immersion process.

[0030] Specifically as follows: (1) Pretreatment: Same as in Example 1; (2) Soaking and aging under normal pressure: Peeled water chestnuts were soaked directly in the first color-protecting solution (composition same as in Example 1) at 48°C and normal pressure for 20 minutes (without vacuum treatment), and the subsequent heating and rinsing were the same as in Example 1; (3) Canning and sterilization: exactly the same as in Example 1.

[0031] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that the first color-protecting solution uses only cysteine, while the second color-protecting solution uses only D-isoascorbic acid.

[0032] Specifically as follows: (1) Pretreatment: Same as in Example 1; (2) Fixing and curing: Only 1% cysteine ​​was added to the first color-protecting solution (without adding disodium EDTA and sodium phytate), and the soaking process (including vacuum) was the same as in Example 1; (3) Canning and sterilization: Only 0.1% D-isoascorbic acid was added to the second color protection solution (without adding tea polyphenol palmitate and rosemary extract), the pH was adjusted to 4.0, and the sterilization process was the same as in Example 1.

[0033] Effect evaluation The canned water chestnuts obtained in Examples 1-5 and Comparative Examples 1-5 of this invention were tested for the following indicators, and the results are as follows: Figure 1 As shown in Table 1: Figure 1 The figures show a comparison of the red core effect of canned water chestnuts from Example 1 and Comparative Examples 1-5 after high-temperature sterilization. The figures clearly show that the canned water chestnuts from Example 1, treated with the composite color-protecting method of this invention, have a clean, uniform white color on the cut surface, with no obvious red core or browning, exhibiting excellent sensory quality. In contrast, the canned goods from Comparative Example 1 (traditional sodium sulfite color protection) and Comparative Example 2 (without the first color-protecting solution) both showed obvious red core areas on the cut surface, with a darker color. Comparative Example 3 (without the second color-protecting solution) had a relatively acceptable initial color, but still showed slight red cores. Comparative Example 4 (immersion under normal pressure) showed a significantly increased red core area compared to Example 1. Comparative Example 5 (single-component color protection) also showed localized red cores. This visual effect matches the data in Table 1 below, directly demonstrating the significant advantage of this invention in suppressing red cores.

[0034] Table 1 Comparison of Quality Indicators of Water Chestnut Canned Food in Different Groups

[0035] Evaluation Notes: Red heart inhibition rate: a core indicator reflecting the color protection effect. In all embodiments of this invention, it is >98%, which is significantly higher than that of each pair of ratios.

[0036] Color index: A higher L value indicates better brightness, and a lower a value indicates a lower red tendency. The product of this invention has high brightness and significant red suppression.

[0037] Storage stability: The incidence of red heart was extremely low after 6 months, indicating that the present invention has long-lasting color protection ability.

[0038] Results analysis: The experimental data from Examples 1-5 and Comparative Examples 1-5 show that the composite color-protecting method described in this invention exhibits significant advantages in inhibiting redness, maintaining color, protecting texture, and improving storage stability of water chestnut canned goods. Specific analysis is as follows: 1. Significant color protection effect, high red heart inhibition rate The red heart inhibition rates in Examples 1-5 were all above 98%, indicating that the method of the present invention can effectively prevent the occurrence of red heart phenomenon in water chestnuts during processing and storage. In contrast, the inhibition rates of Comparative Example 1 (traditional sodium sulfite color protection) and Comparative Example 3 (using only the first color-protecting solution) were 65.3% and 71.5%, respectively, indicating that the effect of a single color-protecting method or traditional color-protecting agent is limited. The inhibition rate of Comparative Example 2 (without using the first color-protecting solution at all) was only 42.1%, further confirming the crucial role of the first stage in color fixation and enzyme inactivation.

[0039] 2. The "dual-color protection" strategy has a synergistic effect. Although Comparative Example 3 used the first color-protecting solution, it did not use the second color-protecting solution. After 6 months of storage, the incidence of red heart still reached 22.6%, significantly higher than the Example group (≤2.1%). This indicates that relying solely on color protection during the pretreatment stage cannot achieve long-term color stability. The second color-protecting solution, containing natural antioxidants such as tea polyphenol palmitate and rosemary extract, along with the acidic environment, forms a second line of defense that plays an irreplaceable role in inhibiting non-enzymatic browning during storage.

[0040] 3. Vacuum soaking process enhances the penetration of color-protecting ingredients. In Comparative Example 4, after the vacuum soaking step was removed, the red heart inhibition rate decreased to 85.6%, indicating that vacuum treatment can significantly promote the penetration of effective components (such as cysteine ​​and disodium EDTA) in the first color-protecting solution into the interior of the hoof tissue, thereby more thoroughly inhibiting enzymatic browning.

[0041] 4. The synergistic effect of compound ingredients is superior to that of single ingredients. Comparative Example 5, using only cysteine ​​and D-isoascorbic acid, achieved a red heart inhibition rate of 76.4%, lower than all other examples. This demonstrates that the combination of cysteine ​​and disodium EDTA, as well as the combined use of natural fat-soluble antioxidants (tea polyphenol palmitate, rosemary extract) and water-soluble antioxidants (D-isoascorbic acid), exhibits a significant synergistic effect in inhibiting different types of browning reactions.

[0042] 5. Color and texture are well preserved. The L-values ​​(brightness) of the example group were all above 82.5, and the a-values ​​were all negative (-1.2 ~ -1.5), indicating that the finished product had a bright color, a very low red tendency, and excellent sensory quality. The hardness values ​​were stable between 35.6 and 36.5 N, indicating that the gradient sterilization process effectively reduced the damage of high temperature to the crisp and tender texture of water chestnuts.

[0043] 6. Excellent storage stability In all examples, the incidence of red heart was less than 2.1% after 6 months of storage, while in the comparative examples it was generally higher than 15%, reaching a maximum of 51.4%. This indicates that the present invention achieves long-lasting color protection and significantly extends the shelf life of the product by systematically blocking multiple browning pathways, including enzymatic, oxidative, and metal ion catalytic processes.

[0044] in conclusion: The composite color-protecting method provided by this invention utilizes a two-stage color-protecting system combining pretreatment for color fixation and enzyme inactivation with long-term in-can antioxidant effects. This system, combined with optimized processes such as vacuum permeation and gradient sterilization, achieves highly efficient and long-lasting inhibition of the red core phenomenon in canned water chestnuts. Its color-protecting effect, product quality, and storage stability are significantly superior to traditional color-protecting methods and single color-protecting strategies, demonstrating promising prospects for industrial application.

[0045] The foregoing description illustrates and describes preferred embodiments of the present invention. As previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A composite color-protecting method for suppressing red centers in canned water chestnuts, characterized in that, Includes the following steps: (1) Pretreatment: Select tender, crisp, thin-skinned, uniformly shaped and undamaged water chestnuts, remove the main and lateral buds and roots, and peel them to obtain peeled water chestnuts; (2) Color fixing, curing and rinsing: The peeled water chestnuts obtained in step (1) are soaked in the first color-protecting solution, which contains a stabilizer composed of cysteine ​​and disodium EDTA; the soaking temperature is 48-52°C and the soaking time is 20-40 minutes; then the peeled water chestnuts and the first color-protecting solution are heated together to 85-90°C and maintained for 3-5 minutes for curing; after curing, the water chestnuts are taken out, rinsed quickly with cold water, and then drained. (3) Canning and sterilization: The water chestnuts drained in step (2) are put into cans, the second color-protecting liquid is injected and the cans are sealed, and the sealed products are sterilized to obtain the finished water chestnut canned products; wherein, the second color-protecting liquid contains tea polyphenol palmitate, rosemary extract, D-isoascorbic acid and pH adjuster.

2. The composite color-protecting method for suppressing red centers in canned water chestnuts according to claim 1, characterized in that: In step (2), the mass concentration of the stabilizer in the first color-protecting solution is 1% to 3%, and the mass ratio of cysteine ​​to disodium EDTA in the stabilizer is (1:1) to (3:2).

3. The composite color-protecting method for suppressing red centers in canned water chestnuts according to claim 1, characterized in that: In step (2), the first color-protecting solution also contains sodium phytate, and the mass concentration of sodium phytate in the first color-protecting solution is 0.03% to 0.08%.

4. The composite color-protecting method for suppressing red centers in canned water chestnuts according to claim 1, characterized in that: In step (2), the soaking operation is first carried out under vacuum conditions of -0.06MPa to -0.09MPa for 5 to 8 minutes, and then restored to normal pressure and the remaining soaking time is completed.

5. The composite color-protecting method for suppressing red centers in canned water chestnuts according to claim 1, characterized in that: In step (3), the mass concentration of the tea polyphenol palmitate in the second color-protecting solution is 0.1% to 0.3%.

6. The composite color-protecting method for suppressing red centers in canned water chestnuts according to claim 1, characterized in that: In step (3), the mass concentration of the rosemary extract in the second color-protecting solution is 2% to 5%; the mass concentration of the D-isoascorbic acid in the second color-protecting solution is 0.1% to 0.3%.

7. The composite color-protecting method for suppressing red centers in canned water chestnuts according to claim 1, characterized in that: In step (3), the pH adjuster is a citrate-sodium citrate buffer solution, and after adjustment, the pH value of the second color-protecting solution is 4.0 to 4.

5.

8. The composite color-protecting method for suppressing red centers in canned water chestnuts according to claim 1, characterized in that: In step (3), the sterilization process adopts a gradient high-temperature sterilization method, specifically: first sterilize at 105±1℃ for 14 to 16 minutes, and then sterilize at 121±1℃ for 9 to 11 minutes.

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