Method for improving browning of quick-frozen cured chestnut kernels

Abstract

The invention relates to a method for improving browning of quick-frozen cured chestnut kernels, which comprises the following steps: performing enzyme deactivation and freeze thawing treatment on raw chestnut kernels to prepare freeze-thawed raw chestnut kernels; soaking the frozen and thawed raw chestnut kernels in a color protection solution 1, soaking the drained frozen and thawed raw chestnut kernels in a color protection solution 2, and preparing the frozen and thawed raw chestnut kernels subjected to color protection treatment; and steaming the frozen and thawed raw chestnut kernels subjected to color protection treatment, cooling in the air, and performing quick-freezing treatment to prepare the quick-frozen cured chestnut kernels. According to the method, the color of the quick-frozen cured chestnut kernels can be remarkably improved, and browning of the quick-frozen cured chestnut kernels is effectively improved; furthermore, the quick-frozen cooked iced chestnut kernels prepared by the method have higher total sugar content and better shape, color, taste and mouth feel, the microbiological indexes meet related requirements, and the appearance and market competitiveness of the product can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of food production, and in particular to a method for improving the browning of quick-frozen and matured chestnut kernels. Background Art

[0002] With the rapid development of China's economy and society, consumers' demand for food products is no longer limited to basic nutritional functions, but they pay more and more attention to the appearance and quality of products. Consumers are more inclined to choose chestnut products with exquisite appearance and bright colors, which is not only a recognition of the quality of the chestnuts sold, but also a reflection of the company's brand value.

[0003] Chestnuts not only have a large yield, but are also rich in vitamins and minerals, and have multiple health benefits, such as replenishing qi and blood, nourishing the stomach, nourishing the kidneys, strengthening the liver and spleen, and promoting blood circulation and stopping bleeding. With the rapid development of the chestnut industry, the planting area and output continue to grow. Fully developing chestnut resources can not only meet market demand, but also make important contributions to economic development and corporate income growth.

[0004] Among the various processing forms of chestnuts, quick-frozen chestnuts, as a frozen food favored by consumers, are gradually gaining popularity in the market due to their convenience and high quality. Quick-frozen chestnuts are made from fresh chestnut kernels and are made through screening, selection, peeling, ripening, freezing and other processes, which can preserve the natural nutrition and taste of chestnuts. Compared with traditional chestnuts, quick-frozen chestnuts can meet consumers' snack needs with their convenient characteristics and cool taste, and have broad prospects and strong competitiveness in the summer market.

[0005] During the processing of quick-frozen chestnuts, chestnuts are prone to browning due to the dual effects of enzymatic browning and non-enzymatic browning. Enzymatic browning is usually caused by peeling, mechanical damage or long-term exposure to air. These factors activate polyphenol oxidase and catalyze the oxidation of phenolic substrates, thereby inducing browning. Non-enzymatic browning occurs during the ripening and heating process, when reducing sugars in chestnuts react with amino acids or proteins to produce melanin. Browning not only affects the appearance of chestnuts, but may also have a negative impact on their flavor and taste, causing the loss of nutrients, affecting the supply of raw materials for fresh chestnuts and chestnut processed products, resulting in a decrease in the economic value and market value of the products, and restricting the development of the chestnut processing industry and increasing value and efficiency. Therefore, it is crucial to develop effective browning control technology. Traditional browning control methods include physical means such as blanching, microwaves, ultrasound, etc., as well as chemical means such as acidic modifiers such as citric acid, ascorbic acid, amino acids, and edible coatings. However, these methods are still difficult to completely improve the browning phenomenon. Summary of the invention

[0006] Based on this, it is necessary to provide a method for improving the browning of quick-frozen and matured chestnut kernels, which can effectively improve the browning of quick-frozen and matured chestnut kernels and improve the product appearance and market competitiveness.

[0007] The technical solution of this application is as follows:

[0008] The present invention provides a method for improving the browning of quick-frozen and matured chestnut kernels, comprising the following steps:

[0009] The raw chestnut kernels are subjected to enzyme inactivation and freeze-thaw treatment to prepare freeze-thawed raw chestnut kernels;

[0010] The frozen-thawed raw chestnut kernels are soaked in color protection liquid 1, and the drained frozen-thawed raw chestnut kernels are soaked in color protection liquid 2 to prepare frozen-thawed raw chestnut kernels that have been subjected to color protection treatment;

[0011] Steaming the frozen-thawed raw chestnut kernels that have undergone color protection treatment, and then quickly freezing them after cooling to prepare quick-frozen mature chestnut kernels;

[0012] Wherein, the color protection solution 1 comprises a mixture of disodium ethylenediaminetetraacetic acid, citric acid, vitamin C and water;

[0013] The color protecting solution 2 comprises a mixture of sucrose, trehalose and water.

[0014] In one embodiment, the color protecting solution 1 is composed of the following raw materials in percentage by weight: 0.1% to 5.0% disodium ethylenediaminetetraacetic acid, 0.1% to 5.0% citric acid, 0.05% to 3.0% vitamin C, and 90% to 99.8% water.

[0015] In one embodiment, the color protecting solution 2 is composed of raw materials including, by weight percentage: 5.0% to 40% sucrose, 5.0% to 40% trehalose, and 20% to 90% water.

[0016] In one embodiment, the step of soaking the frozen-thawed raw chestnut kernels in the color protection liquid 1 satisfies at least one of the following conditions:

[0017] (1) The mass ratio of the frozen-thawed raw chestnut kernels to the color protection solution 1 is 1:1 to 1:4;

[0018] (2) The soaking temperature is 10°C to 60°C;

[0019] (3) The soaking time is 4h to 24h.

[0020] In one embodiment, the step of soaking the drained frozen-thawed raw chestnut kernels in the color protection liquid 2 satisfies at least one of the following conditions:

[0021] (1) The mass ratio of the drained frozen-thawed raw chestnut kernels to the color-protecting liquid 2 is 1:1 to 1:3;

[0022] (2) The soaking temperature is 70°C to 95°C;

[0023] (3) The soaking time is 5 minutes to 30 minutes.

[0024] In one embodiment, the conditions for steaming the frozen-thawed raw chestnut kernels that have undergone color protection treatment include: the steaming temperature is 100° C. to 121° C.; and / or

[0025] The steaming time is 6 minutes to 20 minutes.

[0026] In one embodiment, the conditions for the quick freezing step include:

[0027] The quick freezing temperature is -30℃~-18℃; and / or

[0028] The quick freezing time is 0.3h to 1h.

[0029] The step of inactivating enzymes in the raw chestnut kernels satisfies at least one of the following conditions:

[0030] (1) The temperature for inactivating the enzyme is 90°C to 100°C;

[0031] (2) The enzyme inactivation time is 2 minutes to 5 minutes.

[0032] In one embodiment, the step of subjecting the raw chestnut kernels to freeze-thaw treatment includes a frozen storage step and a thawing step;

[0033] The temperature of the frozen storage is -30°C to -18°C; the temperature of the thawing is 5°C to 30°C; and the time of the thawing is 0.3h to 1h.

[0034] In one embodiment, the step of preparing raw chestnut kernels includes: pre-treating chestnuts to provide raw chestnut kernels with the outer shell and inner skin removed.

[0035] Compared with the prior art, this application has the following beneficial effects:

[0036] This application combines the characteristics of chestnuts and adopts a composite color protection technology of enzyme inactivation, freeze-thaw, and two-step color protection, which can significantly improve the color of quick-frozen and mature chestnut kernels and effectively improve the browning of quick-frozen and mature chestnut kernels; further, the quick-frozen and matured ice chestnut kernels prepared by this method have a higher total sugar content, better shape, color, flavor and mouthfeel, and the microbial indicators all meet the relevant requirements, which can improve the product appearance and market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 This is a process flow chart of quick-frozen and matured chestnut kernels of this application.

[0039] Figure 2 This is the appearance diagram of the quick-frozen and ripened chestnut kernels of the present application, from left to right are Comparative Example 4, Comparative Example 3, Comparative Example 2, Example 1 and Comparative Example 1.

[0040] Figure 3 This is the standard chromatogram of quick-frozen and cooked chestnut kernels of this application.

[0041] Figure 4 This is the standard chromatogram of quick-frozen and cooked chestnut kernels of this application. DETAILED DESCRIPTION

[0042] The following is a further detailed description of a method for inhibiting browning of quick-frozen and ripened chestnut kernels of the present application in conjunction with specific examples. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thoroughly understood.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0044] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0045] The percentage content involved in the present invention, unless otherwise specified, refers to mass percentage for solid-liquid mixing and solid-solid mixing, and refers to volume percentage for liquid-liquid mixing.

[0046] As used herein, "one or more" refers to any one, any two, or any two or more of the listed items.

[0047] Herein, the optional scope of "and / or", "or / and", and "and / or" includes any one of two or more relevant listed items, and also includes any and all combinations of the relevant listed items, wherein said any and all combinations include any two relevant listed items, any more relevant listed items, or a combination of all relevant listed items. (It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in the present application, the technical solution undoubtedly includes technical solutions that are all connected by "logical AND", and also undoubtedly includes technical solutions that are all connected by "logical OR". For example, "A and / or B" includes three parallel solutions of A, B and A+B. For another example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, technical solutions that are all connected by "logical OR"), and also includes any and all combinations of A, B, C, and D, that is, a combination of any two or any three of A, B, C, and D, and also includes a combination of four items of A, B, C, and D (that is, a technical solution that is all connected by "logical AND").)

[0048] Herein, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0049] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0050] Only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, and any upper limit can be combined with any other upper limit to form an undefined range. In addition, each separately disclosed point or single value itself can be combined with any other point or single value as a lower limit or upper limit or with other lower limits or upper limits to form an undefined range. The use of numerical ranges represented by endpoints includes all numbers within the range and any range within the range, for example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4 and 5, etc.

[0051] The percentage contents involved in this application, unless otherwise specified, refer to mass percentage for solid-liquid mixing and solid-solid mixing, and refer to volume percentage for liquid-liquid mixing.

[0052] The percentage concentrations mentioned in this application, unless otherwise specified, refer to the final concentration, which refers to the percentage of the added component in the system after the addition of the component.

[0053] The temperature parameters in this application, unless otherwise specified, allow both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±2°C, ±1°C, ±0.5°C, ±0.4°C, ±0.3°C, ±0.2°C, and ±0.1°C are allowed. Normal temperature or room temperature in this application refers to no temperature control operation, generally 4°C to 35°C, preferably 20±5°C.

[0054] Furthermore, for those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0055] Colorants such as citric acid and EDTA-2Na slow down browning by inhibiting enzyme activity during chestnut processing. Secondly, the high osmotic pressure of sugar solution helps to form a protective film on the surface of chestnuts and reduce oxidation. In addition, freeze-thaw treatment destroys cell walls and enhances the penetration of colorants, further improving the color protection effect. The combination of these technologies can further improve the color protection performance of chestnuts during processing.

[0056] Although China has made some progress in the prevention and control of chestnut browning, the research is mainly focused on the color protection technology of fresh chestnut kernels, while the research on color protection methods during the heating process is still relatively scarce. These patents mainly solve the browning problem of fresh peeled chestnuts by adding color protection agents such as glutathione, tea polyphenols, kojic acid and vitamin C. However, these single color protection methods may not be effective in finished products after heating and cannot fully meet the diverse color protection needs. Therefore, exploring more efficient composite color protection technologies to adapt to different processing conditions and product requirements is still an important direction in the current research field.

[0057] Through extensive research, the technical personnel of this application have proposed a method that combines freeze-thaw treatment with chemical color protection technology to address the problem of immature color protection technology currently available on the market. This method combines the characteristics of chestnuts and comprehensively evaluates the quality of quick-frozen and matured ice chestnut kernels through a colorimeter, Pantone color card discrimination method, and fuzzy mathematical sensory evaluation method. This method aims to solve the common browning problem of quick-frozen and matured ice chestnut kernels during processing, thereby effectively improving their appearance and overall quality. This technology will help improve the color stability and market competitiveness of quick-frozen and matured ice chestnut kernels.

[0058] The present invention provides a method for improving the browning of quick-frozen and matured chestnut kernels, comprising the following steps:

[0059] The raw chestnut kernels are subjected to enzyme inactivation and freeze-thaw treatment to prepare freeze-thawed raw chestnut kernels;

[0060] The frozen-thawed raw chestnut kernels are soaked in color protection liquid 1, and the drained frozen-thawed raw chestnut kernels are soaked in color protection liquid 2 to prepare frozen-thawed raw chestnut kernels that have been subjected to color protection treatment;

[0061] Steaming the frozen-thawed raw chestnut kernels that have undergone color protection treatment, and then quickly freezing them after cooling to prepare quick-frozen mature chestnut kernels;

[0062] Wherein, the color protection solution 1 comprises a mixture of disodium ethylenediaminetetraacetic acid, citric acid, vitamin C and water;

[0063] The color protecting solution 2 comprises a mixture of sucrose, trehalose and water.

[0064] In some examples, the raw materials of the color protection solution 1 include, by weight percentage: 0.1% to 5.0% disodium ethylenediaminetetraacetate, 0.1% to 5.0% citric acid, 0.05% to 3.0% vitamin C, and 90% to 99.8% water. Further, by weight percentage, the raw materials of the color protection solution 1 include: 0.1% to 1.0% disodium ethylenediaminetetraacetate, 0.1% to 1.0% citric acid, 0.05% to 1.0% vitamin C, and 97% to 99.8% water.

[0065] In some examples, the color-protecting liquid 2 includes, by weight percentage, 5.0% to 40% sucrose, 5.0% to 40% trehalose, and 20% to 90% water. Further, by weight percentage, the color-protecting liquid 2 includes, by weight percentage, 10.0% to 30% sucrose, 5.0% to 10% trehalose, and 60% to 85% water.

[0066] In some of the examples, the step of preparing the raw chestnut kernels includes: pre-treating the chestnuts to provide the raw chestnut kernels with the outer shell and the inner skin removed.

[0067] In some of the examples, the steps of pre-treating chestnuts include: grading and picking chestnuts, removing moldy, rotten and worm-eaten chestnuts, washing, removing surface impurities and dust, and removing the outer shell and inner skin of chestnuts. Among them, grading and picking chestnuts refers to selecting chestnuts with a mesh size of 22 to 26, and using a chestnut high-temperature carbonization furnace, a skin rubbing machine, a vibrating screen and a manual picking process to remove the outer shell and inner skin of chestnuts. The high-temperature carbonization furnace is a device for carbonizing chestnuts at high temperature, with the temperature controlled at 800°C and the time being 3 minutes. The carbonized chestnuts are conveyed to the skin rubbing machine, and the carbonized outer skin of the chestnuts is removed by rubbing. Then, the mixture is conveyed to a rinsing machine, and the carbonized outer skin is removed by using the buoyancy of water. After that, the carbonized residue adhering to the chestnut kernels is further removed by a vibrating screening machine to obtain clean raw chestnut kernels. Finally, the clean raw chestnut kernels are transported to the sterilization and maturation tank for sterilization and maturation, and unqualified chestnut kernels are removed by manual selection.

[0068] In some examples, the step of soaking the frozen-thawed raw chestnut kernels in the color protection liquid 1 satisfies at least one of the following conditions:

[0069] (1) The mass ratio of the frozen-thawed raw chestnut kernel to the color protection liquid 1 is 1:1 to 1:4;

[0070] (2) The soaking temperature is 10°C to 60°C;

[0071] (3) The soaking time is 4h to 24h.

[0072] It can be understood that in the step of soaking the frozen-thawed raw chestnut kernels in the color protection liquid 1, the mass ratio of the frozen-thawed raw chestnut kernels to the color protection liquid 1 includes but is not limited to 1:1, 1:2, 1:3, 1:4; the soaking temperature includes but is not limited to 10°C, 20°C, 30°C, 40°C, 50°C, 60°C; the soaking time includes but is not limited to 4h, 8h, 12h, 16h, 20h, 24h.

[0073] In some examples, the step of soaking the drained frozen-thawed raw chestnut kernels in the color protection liquid 2 satisfies at least one of the following conditions:

[0074] (1) The mass ratio of the drained frozen-thawed raw chestnut kernels to the color-protecting liquid 2 is 1:1 to 1:3;

[0075] (2) The soaking temperature is 70°C to 95°C;

[0076] (3) The soaking time is 5 minutes to 30 minutes.

[0077] It can be understood that the mass volume ratio of the drained frozen-thawed raw chestnut kernels to the color protection liquid 2 includes but is not limited to 1:1, 1:2, 1:3; the soaking temperature includes but is not limited to 70℃, 75℃, 80℃, 85℃, 90℃; the soaking time includes but is not limited to 5min, 10min, 15min, 20min, 25min, 30min.

[0078] In some examples, the conditions for steaming the frozen-thawed raw chestnut kernels that have undergone color protection treatment include: the steaming temperature ranges from 100° C. to 121° C. It is understandable that the steaming temperature includes but is not limited to 100° C., 105° C., 110° C., 115° C., 120° C., and 121° C.

[0079] In some examples, the steaming time is 6 min to 20 min. It can be understood that the steaming time includes but is not limited to 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, and 20 min.

[0080] In some examples, the cooling time is 10 minutes to 30 minutes. It can be understood that the cooling time includes but is not limited to 10 minutes, 15 minutes, 20 minutes, 25 minutes, and 30 minutes.

[0081] In some examples, the cooling temperature is 10° C. to 35° C. It can be understood that the cooling temperature includes but is not limited to 10° C., 15° C., 20° C., 25° C., 30° C., and 35° C.

[0082] In some examples, the conditions for the quick freezing step include: the quick freezing temperature is -30°C to -18°C. It can be understood that the quick freezing temperature includes but is not limited to -30°C, -25°C, -20°C, and -18°C.

[0083] In some examples, the conditions for the quick freezing step include: the quick freezing time is 0.3h to 1h. It can be understood that the quick freezing time includes but is not limited to 0.3h, 0.5h, 0.7h, 0.9h, and 1h.

[0084] In some of the examples, the quick freezing equipment is not limited to a tunnel-type quick freezing line or a quick freezing storehouse. Further, the quick freezing line is a tunnel-type quick freezing line, and the time from the feed inlet to the discharge outlet is 10 minutes to 50 minutes.

[0085] In some examples, the step of inactivating the enzyme in the raw chestnut kernels satisfies at least one of the following conditions:

[0086] (1) The temperature for inactivating the enzyme is 90°C to 100°C;

[0087] (2) The enzyme inactivation time is 2 minutes to 5 minutes.

[0088] It can be understood that the temperature for inactivating the enzyme includes, but is not limited to, 90° C., 92° C., 94° C., 96° C., 98° C., and 100° C. The time for inactivating the enzyme includes, but is not limited to, 2 min, 3 min, 4 min, and 5 min.

[0089] In some examples, the step of subjecting the raw chestnut kernels to freeze-thaw treatment includes frozen storage and thawing steps.

[0090] In some examples, the temperature of the frozen storage is -30°C to -18°C. It can be understood that the temperature of the frozen storage includes but is not limited to -30°C, -25°C, -20°C, and -18°C.

[0091] In some examples, the melting temperature is 5° C. to 30° C. It can be understood that the melting temperature includes but is not limited to 5° C., 10° C., 15° C., 20° C., 25° C., and 30° C.

[0092] In some examples, the melting time is 0.3h to 1h. It can be understood that the melting time includes but is not limited to 0.3h, 0.5h, 0.7h, 0.9h, and 1h.

[0093] In some examples, the method for improving browning of quick-frozen and cooked chestnut kernels comprises the following steps:

[0094] (1) The chestnuts are graded and sorted, and moldy, rotten, and worm-eaten chestnuts are removed. The chestnuts are washed to remove surface impurities and dust.

[0095] (2) A high-temperature carbonization furnace, a skin rubbing machine, a vibrating screen and manual selection are used to remove the outer shell and inner skin of the chestnut.

[0096] (3) Mix the raw chestnut kernels with the shell and inner skin removed with hot water in a ratio of 1:3 (w / v), inactivate the enzyme at 95°C for 3 min, place on a perforated filter plate to drain for 10 to 30 min, cool to 25°C, and manually remove unqualified raw chestnut kernels such as those with diseases, insect pests, and disease spots, and set aside.

[0097] (4) Pre-cool the selected raw chestnut kernels in a -10°C to 10°C cold storage environment, place them evenly on quick-freezing trays to avoid stacking, and place them in a -30°C quick-freezing warehouse until the center temperature of the chestnut kernels is lower than -18°C. After quick freezing, place them in sealed bags and store them in a -18°C cold storage for later use.

[0098] (5) taking out the desired quick-frozen raw chestnut kernels from the cold storage, placing them in a room temperature environment of 25° C., thawing them naturally for 3 h, draining the water, and obtaining the frozen-thawed raw chestnut kernels for later use;

[0099] (6) According to the formula, citric acid, EDTA and vitamin C are mixed in distilled water in proportion to prepare color protection solution 1. Color protection solution 1 is heated to 30°C, and the thawed raw chestnut kernels are immersed in the color protection solution 1 at a ratio of 1:2 (w / v) for 8 hours. After the soaking, the chestnut kernels are taken out from the color protection solution 1 using a sieve, and the excess liquid is drained to obtain sample A for later use;

[0100] (7) According to the formula, sucrose and trehalose are mixed in distilled water at a specified ratio to prepare color protection solution 2; the color protection solution 2 is heated to 92° C., and sample A and color protection solution 1 are immersed in the color protection solution 2 at a ratio of 1:1 (w / v) for 30 minutes. After the soaking, the chestnut kernels are removed from the color protection solution 2 using a sieve, and the excess liquid is drained to obtain sample B for later use;

[0101] (8) Place sample B evenly on a steaming tray and steam it at a programmed temperature. After steaming, cool it to room temperature and take the steamed chestnuts out of the steaming tray to obtain sample C.

[0102] (9) Place sample C evenly on the conveyor belt of the quick-freezing line in a single layer to avoid stacking. Start the quick-freezing equipment. Sample C enters the quick-freezing tunnel along the conveyor belt and is quick-frozen at -30°C for 1 hour. When the center temperature is lower than -18°C, turn off the quick-freezing equipment and take the sample out of the conveyor belt to obtain quick-frozen cooked chestnut kernels.

[0103] The following is further described in conjunction with specific embodiments. The raw materials involved in the following specific embodiments, unless otherwise specified, can all be commercially available; the instruments used, unless otherwise specified, can all be commercially available; the processes involved, unless otherwise specified, are all routinely selected by those skilled in the art.

[0104] The chestnut variety used in the embodiments and comparative examples is Hebei Qianxi chestnut, which is Grade A chestnut kernel, with moldy kernels ≤ 2.0% and soluble solid content greater than 12%.

[0105] The following are specific embodiments.

[0106] Example 1

[0107] This embodiment is used to prepare quick-frozen mature chestnut kernels. The process flow chart is as follows: Figure 1 The specific steps are as follows:

[0108] (1) Pretreatment: chestnuts are graded and selected to select chestnuts of 22 mesh, moldy, rotten and worm-eaten chestnuts are removed, and the chestnuts are washed to remove surface impurities and dust.

[0109] (2) Peeling: The outer shell and inner skin of chestnuts are removed by using a high-temperature carbonization furnace, a peeling machine, a vibrating screen and manual selection process;

[0110] (3) Inactivation of enzymes: Mix the raw chestnut kernels with the shell and inner skin removed with hot water in a ratio of 1:2 (w / v), inactivate the enzymes at 95°C for 3 min, place on a perforated filter plate to drain for 20 min, cool to 25°C, and manually remove unqualified raw chestnut kernels with pests, diseases, and spots, and set aside.

[0111] (4) Freeze-thaw: Pre-cool the selected raw chestnut kernels in a -10°C cold storage environment, place them evenly on a quick-freezing tray to avoid stacking, and place them in a -30°C quick-freezing warehouse until the central temperature of the chestnut kernels is lower than -18°C. Quick freezing is completed, and the kernels are placed in sealed bags and stored in a -18°C cold storage for 7 days. Take out the required quick-frozen raw chestnut kernels from the cold storage, place them in a 25°C room temperature environment, and thaw naturally for 3 hours. Drain the water to obtain the frozen-thawed raw chestnut kernels for later use.

[0112] (5) Color protection 1: immerse the frozen and thawed raw chestnut kernels and color protection solution 1 in a ratio of 1:2 (w / v), the immersion temperature is 25°C, and the immersion time is 8 hours; after the immersion, use a sieve to take out the chestnut kernels from the color protection solution 1, and drain the excess liquid to obtain sample A for later use; the color protection solution 1 is composed of the following raw materials in percentage by weight: 0.27% disodium ethylenediaminetetraacetic acid, 0.2% citric acid, 0.05% vitamin C, and the balance is distilled water:

[0113] (6) Color protection 2: Sample B and color protection solution 2 are immersed in color protection solution 2 at a ratio of 1:1 (w / v), the immersion temperature is 90°C, and the immersion time is 0.5h; after the immersion, the chestnut kernels are taken out from the color protection solution 2 using a sieve, and the excess liquid is drained to obtain sample B for later use; the color protection solution 2 is composed of the following raw materials in percentage by weight: 18.8% sucrose, 6.8% trehalose, and the balance is distilled water:

[0114] (7) Steaming: Place sample B evenly on a steaming tray and steam at 121°C for 12 min. After steaming, cool at room temperature to 25°C for 10 min. Take the steamed chestnuts out of the steaming tray to obtain sample C.

[0115] (8) Quick freezing: Place sample C evenly on the conveyor belt of the tunnel quick freezing line in a single layer to avoid stacking. Start the quick freezing equipment. Sample C enters the quick freezing tunnel along the conveyor belt and is quick frozen at -30°C for 0.5 h. When the center temperature is lower than -18°C, turn off the quick freezing equipment and take the sample out of the conveyor belt to obtain quick-frozen cooked chestnut kernels.

[0116] Example 2

[0117] This embodiment is used to prepare quick-frozen and mature chestnut kernels, and the specific steps are as follows:

[0118] (1) Pretreatment: chestnuts are graded and selected to select chestnuts of 22 mesh, moldy, rotten and worm-eaten chestnuts are removed, and the chestnuts are washed to remove surface impurities and dust.

[0119] (2) Peeling: The outer shell and inner skin of chestnuts are removed by using a high-temperature carbonization furnace, a peeling machine, a vibrating screen and manual selection process;

[0120] (3) Inactivation of enzymes: Mix the raw chestnut kernels with the shell and inner skin removed with hot water in a ratio of 1:2 (w / v), inactivate the enzymes at 90°C for 5 min, place on a perforated filter plate to drain for 30 min, cool to 25°C, and manually remove unqualified raw chestnut kernels with pests, diseases, and spots, and set aside.

[0121] (4) Freeze-thaw: Pre-cool the selected raw chestnut kernels in a 6°C cold storage environment, place them evenly on a quick-freezing tray to avoid stacking, and place them in a -20°C quick-freezing warehouse until the central temperature of the chestnut kernels is lower than -18°C. After quick freezing, place them in sealed bags and store them in a cold storage at <-18°C for 10 days; take out the required quick-frozen raw chestnut kernels from the cold storage, place them in a 25°C room temperature environment, thaw them naturally for 6 hours, drain the water, and obtain the frozen-thawed raw chestnut kernels for later use;

[0122] (5) Color protection 1: immerse the frozen and thawed raw chestnut kernels and color protection solution 1 in a ratio of 1:3 (w / v) in the color protection solution 1 for 8 hours; after the immersion, use a sieve to remove the chestnut kernels from the color protection solution 1, and drain the excess liquid to obtain sample A for later use; the color protection solution 1 is composed of the following raw materials in percentage by weight: 1.0% disodium ethylenediaminetetraacetic acid, 0.5% citric acid, 1% vitamin C, and the balance is distilled water:

[0123] (6) Color protection 2: Sample B and color protection solution 2 are immersed in color protection solution 2 at a ratio of 1:2 (w / v) for 0.3 h. After the immersion, chestnut kernels are taken out from color protection solution 2 using a sieve and excess liquid is drained to obtain sample B for later use. Color protection solution 2 is composed of the following raw materials in percentage by weight: 30% sucrose, 10% trehalose, and the remainder is distilled water:

[0124] (7) Steaming: Place sample B evenly on a steaming tray and steam at 121°C for 12 min. After steaming, cool at room temperature to 25°C for 10 min. Take the steamed chestnuts out of the steaming tray to obtain sample C.

[0125] (8) Quick freezing: Place sample C evenly on the conveyor belt of the tunnel quick freezing line in a single layer to avoid stacking. Start the quick freezing equipment. Sample C enters the quick freezing tunnel along the conveyor belt and is quick frozen at -30°C for 0.5 h. When the center temperature is lower than -18°C, turn off the quick freezing equipment and take the sample out of the conveyor belt to obtain quick-frozen cooked chestnut kernels.

[0126] Example 3

[0127] This embodiment is used to prepare quick-frozen and mature chestnut kernels, and the specific steps are as follows:

[0128] (1) Pretreatment: chestnuts are graded and selected to select chestnuts of 24 mesh, moldy, rotten and worm-eaten chestnuts are removed, and the chestnuts are washed to remove surface impurities and dust.

[0129] (2) Peeling: The outer shell and inner skin of chestnuts are removed by using a high-temperature carbonization furnace, a peeling machine, a vibrating screen and manual selection process;

[0130] (3) Inactivation of enzymes: Mix the raw chestnut kernels with the shell and inner skin removed with hot water in a ratio of 1:2 (w / v), inactivate the enzymes at 80°C for 5 min, place on a perforated filter plate to drain for 20 min, cool to 25°C, and manually remove unqualified raw chestnut kernels with pests, diseases, and spots, and set aside.

[0131] (4) Freeze-thaw: Pre-cool the selected raw chestnut kernels in a 5°C cold storage environment, place them evenly on a quick-freezing tray to avoid stacking, and place them in a -25°C quick-freezing warehouse until the central temperature of the chestnut kernels is lower than -18°C. Quick freezing is completed, and the kernels are placed in sealed bags and stored in a -18°C cold storage for 7 days. Take out the required quick-frozen raw chestnut kernels from the cold storage, place them in a 25°C room temperature environment, and thaw naturally for 3 hours. Drain the water to obtain the frozen-thawed raw chestnut kernels for later use.

[0132] (5) Color protection 1: immerse the frozen and thawed raw chestnut kernels and color protection solution 1 in a ratio of 1:2 (w / v) in the color protection solution 1 for 12 hours; after the immersion, use a sieve to remove the chestnut kernels from the color protection solution 1, and drain the excess liquid to obtain sample A for later use; the color protection solution 1 is composed of the following raw materials in percentage by weight: 0.15% disodium ethylenediaminetetraacetic acid, 0.1% citric acid, 0.1% vitamin C, and the balance is distilled water:

[0133] (6) Color protection 2: Sample B and color protection solution 2 are immersed in color protection solution 2 at a ratio of 1:1 (w / v) for 0.5 h. After the immersion, chestnut kernels are taken out from color protection solution 2 using a sieve and excess liquid is drained to obtain sample B for later use. Color protection solution 2 is composed of the following raw materials in percentage by weight: 10% sucrose, 5% trehalose, and the remainder is distilled water:

[0134] (7) Steaming: Place sample B evenly on a steaming tray and steam at 121°C for 12 min. After steaming, cool at room temperature to 25°C for 10 min. Take the steamed chestnuts out of the steaming tray to obtain sample C.

[0135] (8) Quick freezing: Place sample C evenly on the conveyor belt of the tunnel quick freezing line in a single layer to avoid stacking. Start the quick freezing equipment. Sample C enters the quick freezing tunnel along the conveyor belt and is quick frozen at -30°C for 0.5 h. When the center temperature is lower than -18°C, turn off the quick freezing equipment and take the sample out of the conveyor belt to obtain quick-frozen cooked chestnut kernels.

[0136] Example 4

[0137] This embodiment is used to prepare quick-frozen and mature chestnut kernels, and the specific steps are as follows:

[0138] (1) Pretreatment: chestnuts are graded and selected to select chestnuts of 22 mesh, moldy, rotten and worm-eaten chestnuts are removed, and the chestnuts are washed to remove surface impurities and dust.

[0139] (2) Peeling: The outer shell and inner skin of chestnuts are removed by using a high-temperature carbonization furnace, a peeling machine, a vibrating screen and manual selection process;

[0140] (3) Inactivation of enzymes: Mix the raw chestnut kernels with the shell and inner skin removed with hot water in a ratio of 1:2 (w / v), inactivate the enzymes at 99°C for 3 min, place on a perforated filter plate to drain for 20 min, cool to 25°C, and manually remove unqualified raw chestnut kernels with pests, diseases, and spots, and set aside.

[0141] (4) Freeze-thaw: Pre-cool the selected raw chestnut kernels in a -10°C cold storage environment, place them evenly on a quick-freezing tray to avoid stacking, and place them in a -30°C quick-freezing warehouse until the central temperature of the chestnut kernels is lower than -18°C. Quick freezing is completed, and the kernels are placed in sealed bags and stored in a -18°C cold storage for 7 days. Take out the required quick-frozen raw chestnut kernels from the cold storage, place them in a 25°C room temperature environment, and thaw naturally for 3 hours. Drain the water to obtain the frozen-thawed raw chestnut kernels for later use.

[0142] (5) Color protection 1: immerse the frozen and thawed raw chestnut kernels in the color protection solution 1 at a ratio of 1:4 (w / v) for 6 hours; after the immersion, use a sieve to remove the chestnut kernels from the color protection solution 1, and drain the excess liquid to obtain sample A for later use; the color protection solution 1 is composed of the following raw materials in percentage by weight: 0.27% disodium ethylenediaminetetraacetic acid, 0.2% citric acid, 0.05% vitamin C, and the balance is distilled water:

[0143] (6) Color protection 2: Sample B and color protection solution 2 are immersed in color protection solution 2 at a ratio of 1:3 (w / v) for 0.5 h. After the immersion, chestnut kernels are taken out from color protection solution 2 using a sieve and excess liquid is drained to obtain sample B for later use. Color protection solution 2 is composed of the following raw materials in percentage by weight: sucrose 18.8%, trehalose 6.8%, sugar content of about 20%, and the remainder is distilled water:

[0144] (7) Steaming: Place sample B evenly on a steaming tray and steam at 121°C for 12 min. After steaming, cool at room temperature to 25°C for 10 min. Take the steamed chestnuts out of the steaming tray to obtain sample C.

[0145] (8) Quick freezing: Place sample C evenly on the conveyor belt of the tunnel quick freezing line in a single layer to avoid stacking. Start the quick freezing equipment. Sample C enters the quick freezing tunnel along the conveyor belt and is quick frozen at -30°C for 0.5 h. When the center temperature is lower than -18°C, turn off the quick freezing equipment and take the sample out of the conveyor belt to obtain quick-frozen cooked chestnut kernels.

[0146] Comparative Example 1

[0147] Comparative Example 1 is substantially the same as Example 1, except that: Comparative Example 1 is not subjected to freeze-thaw, enzyme inactivation, color protection 1, or color protection 2 treatments.

[0148] Comparative Example 2

[0149] Comparative Example 2 is substantially the same as Example 1, except that: Comparative Example 2 is not subjected to the color protection 2 treatment.

[0150] Comparative Example 3

[0151] Comparative Example 3 is substantially the same as Example 1, except that: Comparative Example 3 is not subjected to freeze-thaw treatment.

[0152] Comparative Example 4

[0153] Comparative Example 4 is substantially the same as Example 1, except that: Comparative Example 4 is not subjected to the color protection 1 treatment.

[0154] The total sugar content of the quick-frozen and mature chestnut kernels prepared in Example 1 and Comparative Example 1 was determined by anthrone colorimetry. The quick-frozen and mature chestnut kernels were crushed to less than 2 mm, and 80% (v / v) ethanol was used to purify the total sugar. The anthrone reagent and the sample solution were added, and the reaction was carried out at 95°C for 10 minutes. The absorbance was measured at 620nm using a spectrophotometer (752 UV-visible spectrophotometer, Platinum Temperature Instrument Co., Ltd.). The total sugar content of the quick-frozen and mature chestnut kernels prepared in Example 1 of the present application was measured to be 10.21%, and the total sugar content of the quick-frozen and mature chestnut kernels prepared in Comparative Example 1 was 11.09%. It can be seen from the total sugar content of Example 1 and Comparative Example 1 that the quick-frozen and mature chestnut kernels prepared in Example 1 have a higher total sugar content.

[0155] Fuzzy mathematics was used to conduct a comprehensive sensory evaluation of quick-frozen and mature chestnut kernels. The shape, color and taste of quick-frozen and mature chestnut kernels are important sensory indicators that determine their quality. Therefore, these four indicators were selected for evaluation in this experiment (see Table 1 for specific evaluation criteria). A sensory evaluation team consisting of five sensory evaluation experts and 15 company employees scored the quick-frozen and mature chestnut kernels according to the standards. The five sensory evaluation experts gave the membership degrees of different indicators based on the importance of the four sensory indicators in the sensory evaluation. The membership degrees ranged from 0 to 1 (0 represents unimportant and 1 represents the most important), and the membership degrees were normalized to determine the weight vector. Determine the evaluation domain U of quick-frozen mature chestnut kernels, U = {morphology, color, flavor and mouthfeel}, u represents the sensory quality evaluation index of the product, and in this experiment, u is composed of three factors: morphology, color, flavor and mouthfeel; determine the evaluation domain V of quick-frozen mature chestnut kernels, and according to the sensory quality evaluation grade of quick-frozen mature chestnut kernels in Table 1, obtain its evaluation domain V = {better, good, average, poor}. According to the fuzzy judgment method, the sensory evaluation results of quick-frozen mature chestnut kernels are processed, and the sensory quality comprehensive evaluation result vector is calculated, and the grades of three products are divided. The weight set X = {0.20, 0.50, 0.30}, that is, 20 points for morphology, 50 points for color, 20 points for flavor and mouthfeel, a total of 100 points. The fuzzy relationship comprehensive evaluation set Y = X*R, where X is the weight set and R is the fuzzy matrix.

[0156] Table 1 Sensory evaluation indicators

[0157]

[0158] Ten evaluators conducted sensory evaluation on the two products according to the established evaluation methods and standards. The results are shown in Table 2.

[0159] Table 2 Sensory evaluation results

[0160]

[0161] According to the sensory evaluation results, 4 of the 10 assessors thought that the shape of the quick-frozen and ripened chestnut kernels was good, 2 were good, 3 were average, and 1 was poor, so U1 = (0.4, 0.2, 0.3, 0.1); similarly, U2 = (0.1, 0.1, 0.3, 0.4), U3 = (0.4, 0.2, 0.2, 0.2), and the evaluation results of the four factors were combined into a matrix:

[0162]

[0163] Similarly,

[0164]

[0165] The matrix is ​​fuzzy transformed, and the fuzzy relationship is used to comprehensively judge the set Y = A × R

[0166] have to

[0167] Same reason

[0168] 0.10}.

[0169] The evaluation results are graded as 90, 70, 40, and 10 points respectively, and each quantity of the comprehensive evaluation result after fuzzy change is multiplied by the corresponding score and added up to get the final score of each sample:

[0170]

[0171] Similarly, H2 = 70.4 points

[0172] Therefore, the overall score of the above samples is H2>H1, the overall sensory quality of Sample 2 is better, the control group is rated as "average", and Example 1 is rated as "good", and Example 1 has a higher comprehensive score, which is reflected in the higher scores in color and morphology.

[0173] The color difference values ​​of the quick-frozen and ripened chestnut kernels prepared in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were measured by a colorimeter (Ci64 X-Rite (Shanghai) Color Technology Co., Ltd.), where L* is the brightness value, a* is the red-green value, and b* is the yellow-blue value. The L, a and b of Comparative Example 1 are relatively low, the color is darker, close to medium gray, and the color tends to be yellow-red. The results are shown in Table 3. In contrast, Example 1 and Comparative Example 2 show significant color improvement. The overall color difference (ΔE) of Example 1 is 42.68, the brightness (ΔL) is significantly increased (21.39), the red-green degree (Δa*) and the yellow-blue degree (Δb*) change greatly, showing a higher brightness and obvious yellow and red, indicating that Example 1 has the most significant improvement in color. The brightness of Comparative Example 1 is lower than that of Example 1, but the red-green degree changes more (16.44), the yellow-blue degree changes less (7.40), and the overall color difference (ΔE) is 33.73. The color improvement is slightly inferior to that of Example 1. This may be due to the high osmotic pressure of the sugar solution in Example 1, which effectively reduces oxidation and browning by extracting water and forming a protective film. In contrast, the color difference (ΔE) of Comparative Example 2 is the smallest (7.82), and the changes in brightness, red-green degree, and yellow-blue degree are very small. The color is closest to Comparative Example 1, indicating that the color protection liquid is difficult to penetrate and adhere without freeze-thaw treatment, and chestnuts are prone to browning. The color difference (ΔE) of Comparative Example 3 is 13.17, the brightness changes moderately (13.55), the red-green degree decreases slightly (-0.74), the yellow-blue degree changes greatly (8.57), the color is darker, and the red-yellow change is not obvious, indicating that chestnuts lacking color protection 1 treatment are difficult to completely protect their color. In summary, the composite color protection technology of Example 1 shows the most significant effect in improving browning and improving color quality, while the single color protection treatment of Comparative Examples 2, 3 and 4 has no significant effect. Figure 2 shown.

[0174] Table 3 Color difference data of quick-frozen and cooked chestnut kernels

[0175]

[0176] The internationally accepted standard color card, PANTONE, was used to perform color quantitative comparison on Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4. With reference to the 2016 edition of the Pantone color card atlas, 10 food professionals with sensory evaluation experience discussed and selected 10 colors that can represent the color of quick-frozen and matured chestnut kernels to produce a reference map of quick-frozen chestnut kernels. 10 sensory reviewers selected 6 pictures that can cover all samples from the pictures of quick-frozen and matured chestnut kernels, sorted them from light to dark in color, and assigned corresponding scores (0 to 10 points) to produce a standard atlas of quick-frozen and matured chestnut kernels (see Figure 3 and Figure 4). The average score of the samples in the comparative example 1 group was 1.5 points, the average score of the samples in the embodiment 1 was 8.5 points, the average score of the samples in the comparative example 2 was 8.4 points, the average score of the samples in the comparative example 3 was 3.7 points, and the average score of the samples in the comparative example 4 was 3.4 points. Observation shows that the color of the samples in the embodiment 1 which fully implemented the process was the best, followed by the comparative example 2 which lacked the sugar-preserving color, and the color improvement of the comparative examples 3 and 4 which were not subjected to the freeze-thaw treatment and the color-preserving 1 treatment was less.

[0177] For Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4, the quick-frozen chestnut kernels with a score of > 4 points according to the standard spectrum of quick-frozen chestnut kernels in Example 4 are N1 that have successfully protected their color, the total number is N, and the qualified rate of color protection = N1 / N. The test results are shown in Table 4. In Example 1, the composite color protection technology of enzyme inactivation, freeze-thaw and two-step color protection is adopted, and the color protection effect is the most significant, while the effects of Comparative Examples 2, Comparative Examples 3 and Comparative Examples 4 are relatively poor.

[0178] Table 4 Color protection qualified rate of quick-frozen and ripened chestnut kernels

[0179]

[0180] The total colony count, Escherichia coli, Staphylococcus aureus and Salmonella were measured for Example 1 and Comparative Example 1. The total colony count was detected according to the detection method of GB 4789.2, the Escherichia coli was detected according to the detection method of GB4789.3, and the Escherichia coli and Staphylococcus aureus were detected according to the detection method of GB 4789.4. The test results are shown in Table 5, and the results are in accordance with Q / AHS 0001S. The microbial indicators of the quick-frozen and matured chestnut kernels prepared in this application all meet the relevant requirements.

[0181] Table 5 Colony standard of quick-frozen and ripened chestnut kernels

[0182]

[0183] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0184] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims, and the description may be used to interpret the content of the claims.

Claims

1. A method for improving the browning of quick-frozen and matured chestnut kernels, characterized in that: The following steps are involved: The raw chestnut kernels are subjected to enzyme inactivation and freeze-thaw treatment to prepare freeze-thawed raw chestnut kernels; The frozen-thawed raw chestnut kernels are soaked in color protection liquid 1, and the drained frozen-thawed raw chestnut kernels are soaked in color protection liquid 2 to prepare frozen-thawed raw chestnut kernels that have been subjected to color protection treatment; Steaming the frozen-thawed raw chestnut kernels that have undergone color protection treatment, and then quickly freezing them after cooling to prepare quick-frozen mature chestnut kernels; Wherein, the color protection solution 1 comprises a mixture of disodium ethylenediaminetetraacetic acid, citric acid, vitamin C and water; The color protecting solution 2 comprises a mixture of sucrose, trehalose and water.

2. The method for improving browning of quick-frozen and matured chestnut kernels according to claim 1, characterized in that: Calculated by weight percentage, the raw materials of the color protection liquid 1 include: 0.1% to 5.0% disodium ethylenediaminetetraacetic acid, 0.1% to 5.0% citric acid, 0.05% to 3.0% vitamin C, and 90% to 99.8% water.

3. The method for improving browning of quick-frozen and matured chestnut kernels according to claim 1, characterized in that: Calculated by weight percentage, the raw materials of the color-protecting liquid 2 include: 5.0% to 40% sucrose, 5.0% to 40% trehalose, and 20% to 90% water.

4. The method for improving browning of quick-frozen and matured chestnut kernels according to claim 1, characterized in that: The step of soaking the frozen-thawed raw chestnut kernels in the color protection liquid 1 satisfies at least one of the following conditions: (1) The mass ratio of the frozen-thawed raw chestnut kernels to the color protection solution 1 is 1:1 to 1:4; (2) The soaking temperature is 10°C to 60°C; (3) The soaking time is 4h to 24h.

5. The method for improving browning of quick-frozen and matured chestnut kernels according to claim 1, characterized in that: The step of soaking the drained frozen-thawed raw chestnut kernels in the color-protecting liquid 2 satisfies at least one of the following conditions: (1) The mass ratio of the drained frozen-thawed raw chestnut kernels to the color-protecting liquid 2 is 1:1 to 1:3; (2) The soaking temperature is 70°C to 95°C; (3) The soaking time is 5 minutes to 30 minutes.

6. The method for improving browning of quick-frozen and matured chestnut kernels according to claim 1, characterized in that: The conditions for steaming the frozen-thawed raw chestnut kernels that have undergone color protection treatment include: the steaming temperature is 100° C. to 121° C.; and / or The steaming time is 6 minutes to 20 minutes.

7. The method for improving browning of quick-frozen and matured chestnut kernels according to claim 1, characterized in that: The conditions for the quick freezing step include: The quick freezing temperature is -30℃~-18℃; and / or The quick freezing time is 0.3h to 1h.

8. The method for improving browning of quick-frozen and matured chestnut kernels according to claim 1, characterized in that: The step of inactivating enzymes in the raw chestnut kernels satisfies at least one of the following conditions: (1) The temperature for inactivating the enzyme is 90°C to 100°C; (2) The enzyme inactivation time is 2 minutes to 5 minutes.

9. The method for improving browning of quick-frozen and matured chestnut kernels according to claim 1, characterized in that: The step of subjecting the raw chestnut kernels to freeze-thaw treatment comprises a freezing storage step and a thawing step; The temperature of the frozen storage is -30°C to -18°C; the temperature of the thawing is 5°C to 30°C; and the time of the thawing is 0.3h to 1h.

10. The method for improving browning of quick-frozen and matured chestnut kernels according to claim 1, characterized in that: The step of preparing raw chestnut kernels comprises: pre-treating chestnuts to provide raw chestnut kernels with the shell and inner skin removed.

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