Processing method of instant boiled peanuts based on low-temperature permeation technology

Abstract

The invention belongs to the field of food processing, and discloses a processing method of instant boiled peanuts based on a low-temperature permeation process, which comprises the following steps: by taking fresh peanut kernels with specific water content as raw materials, pretreating the raw materials with a sodium bicarbonate solution, and then preparing flavor permeation liquid prepared from spices, salt, sugar and compound preservatives (D-sodium erythorbate and nisin); and carrying out low-temperature (35-40 DEG C) permeation under vacuum and ultrasonic assistance, carrying out two-stage boiling at 80-85 DEG C and 92-95 DEG C, and finally, rapidly cooling and carrying out modified atmosphere packaging with the oxygen residual quantity of less than or equal to 0.5%. The method effectively solves the problems of peanut coat damage, soft and rotten texture, non-uniform flavor permeation, short shelf life and the like caused by a traditional process, and the obtained product peanut coat is high in integrity rate, uniform in flavor, good in taste and capable of being stored for a long time at normal temperature.

Description

Technical Field

[0001] The invention belongs to the field of food processing and specifically discloses a method for processing instant boiled peanuts based on a low-temperature permeation process. Background Art

[0002] Ready-to-eat boiled peanuts, a traditional snack food, are widely loved by consumers for their rich nutrition and unique flavor. However, existing processing technologies commonly suffer from poor texture stability, uneven flavor penetration, short shelf life, and nutrient loss. Traditional processes often use normal pressure and high-temperature cooking. While this can achieve initial ripening, prolonged high-temperature processing can easily lead to severe damage to the peanut coating, excessive softening of the peanut kernel, and difficulty in effectively penetrating spices and flavors into the peanuts, resulting in unstable product taste and flavor quality.

[0003] The current mainstream processing methods have obvious technical limitations: First, the thermal effect during normal pressure cooking is intense, the peanut cell structure is damaged, and the free starch precipitates, resulting in turbid soup and sticky products; second, single temperature cooking makes it difficult to take into account both tissue softening and flavor retention, and often sacrifices texture in exchange for maturity; third, although conventional preservative treatments (such as high-temperature sterilization) can extend the shelf life, they aggravate texture deterioration and color browning, and easily produce a steamed flavor that covers the original peanut aroma; fourth, the existing process has lax requirements on the freshness of raw materials, and the physiological activity after harvest is not effectively regulated, resulting in accelerated lipid oxidation in the finished product, and the product is prone to produce a rancid taste.

[0004] Furthermore, existing technologies for flavor enhancement often rely on pre-soaking or extended cooking times, which is not only inefficient but also leads to increased microbial risks due to insufficient water activity control. Conventional vacuum packaging is commonly used in packaging, but high residual oxygen levels can easily lead to oxidative deterioration, making long-term storage and transportation at room temperature difficult. Therefore, there is an urgent need to develop a new, green processing technology that can maintain the intact shape of the peanut kernel, ensure uniform flavor penetration, achieve suitable texture characteristics, and maintain a long shelf life. Summary of the Invention

[0005] In view of the above problems, the present invention discloses a method for processing instant boiled peanuts based on a low-temperature infiltration process.

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

[0007] A method for processing instant boiled peanuts based on a low-temperature permeation process. The raw materials, by weight, include: 100 parts of fresh flower kernels, 1.5-3 parts of edible salt, 0.5-2 parts of white sugar, 0.3-0.8 parts of star anise, 0.2-0.6 parts of cinnamon, 0.1-0.4 parts of licorice, 150-200 parts of purified water, 0.05-0.15 parts of sodium D-erythorbate, and 0.01-0.03 parts of nisin. The fresh flower kernels are shelled peanut kernels harvested within 24 hours, with a moisture content of 30-35%, and a particle size range of 8-12 mm.

[0008] The method comprises the following steps:

[0009] (1) Pretreatment: After screening, fresh flower kernels are soaked in 0.5-1% sodium bicarbonate solution at 40-45°C for 15-20 minutes;

[0010] (2) Preparation of flavoring solution: Add edible salt, white sugar, star anise, cinnamon bark, and licorice to purified water, heat and stir at 60-70°C for 30-60 minutes, filter, and add sodium D-isoascorbate and nisin to obtain flavoring solution;

[0011] (3) Low-temperature infiltration: soak the treated peanut kernels in the infiltration solution and infiltrate for 40-60 minutes at a vacuum degree of -0.08 to -0.09 MPa and a temperature of 35-40°C;

[0012] (4) Staged cooking: first cook at 80-85℃ for 15-20 minutes, then heat to 92-95℃ and cook for 5-8 minutes;

[0013] (5) Rapid cooling: Use ice water spray to reduce the core temperature of the peanut kernel to below 10°C within 3 minutes;

[0014] (6) Modified atmosphere packaging: Fill the bag with a mixture of nitrogen and carbon dioxide, and the residual oxygen content in the bag is ≤0.5%.

[0015] Furthermore, in the above processing method, the osmotic pressure of the flavoring solution in step (3) is adjusted to 1200-1500 mOsm / L, and the pH value is controlled at 6.0-6.5.

[0016] Furthermore, in the above processing method, the low-temperature infiltration in step (3) is carried out with the assistance of ultrasound, with an ultrasonic power of 200-400W and a frequency of 28kHz.

[0017] Furthermore, in the above processing method, the low-temperature penetration equipment in step (3) adopts a sandwich vacuum odor penetration tank, and a variable frequency ultrasonic auxiliary system is installed in the tank.

[0018] Furthermore, in the above processing method, 0.02-0.05% of the weight of the peanut kernels is added with sodium citrate as a texture improver during the staged cooking process in step (4).

[0019] Furthermore, in the above processing method, the hardness of the peanut kernel after cooling in step (5) is controlled to be 2000-2500g.

[0020] The invention discloses instant boiled peanuts prepared by the method. The water activity Aw of the product is less than or equal to 0.85, and the total bacterial count is less than or equal to 100 CFU / g.

[0021] Furthermore, the instant boiled peanuts have a peanut skin integrity rate of ≥95%, a peanut skin breakage rate of ≤3%, and are uniformly milky yellow in color.

[0022] Furthermore, in the accelerated storage test at 37°C, the peroxide value of the instant boiled peanuts mentioned above reached 0.25g / 100g for no less than 180 days, and aflatoxin B1 was not detected, with a detection limit of 0.1μg / kg.

[0023] Furthermore, the shelf life of the instant boiled peanuts mentioned above is not less than 9 months at room temperature.

[0024] Compared with the existing technology, the present invention has the following advantages and beneficial effects:

[0025] 1) Significantly Improved Quality: Vacuum ultrasound-assisted low-temperature penetration allows flavor substances to evenly penetrate the interior of the peanut kernel, avoiding a "salty outside and bland inside" appearance. The synergistic effect of segmented cooking and rapid cooling ensures a peanut skin integrity rate of ≥95%, a hardness controlled at 2000-2500g, and excellent texture, avoiding soft or hard cores.

[0026] 2) Shelf life is greatly extended: The composite preservative works in conjunction with modified atmosphere packaging technology to effectively inhibit oil oxidation and microbial growth. After 180 days of accelerated storage at 37°C, the peroxide value of the product is still below 0.25g / 100g, and the shelf life at room temperature can reach more than 9 months.

[0027] 3) Better nutrient retention: Low-temperature penetration and segmented heating processes reduce the damage to heat-sensitive nutrients, with the retention rate of vitamin E reaching 88.5%, which is better than traditional high-temperature processes. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is described in further detail below. However, it should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the present invention.

[0029] Example 1

[0030] Instant boiled peanuts prepared by a low-temperature permeation process are prepared from the following raw materials in parts by weight:

[0031] 100 parts of fresh flower kernels, 1.5 parts of edible salt, 0.5 parts of white sugar, 0.3 parts of star anise, 0.2 parts of cinnamon bark, 0.1 parts of liquorice, 150 parts of purified water, 0.05 parts of sodium D-erythorbate, 0.01 parts of nisin;

[0032] The fresh peanut kernels are peanut kernels with skins and a moisture content of 30% within 24 hours after harvesting, with a particle size range of 8-10 mm;

[0033] The processing method includes the following steps:

[0034] (1) Pretreatment: After screening, fresh flower kernels were soaked in 0.5% sodium bicarbonate solution at 40°C for 20 minutes, removed and rinsed once with purified water;

[0035] (2) Preparation of flavoring solution: Add edible salt, white sugar, star anise, cinnamon bark, and licorice to purified water, heat and stir at 60°C for 60 minutes, filter through a 200-mesh filter cloth, add sodium D-isoascorbate and nisin to the filtrate, stir and dissolve, and obtain flavoring solution; the osmotic pressure of the flavoring solution was measured to be 1200 mOsm / L, and the pH was adjusted to 6.0 with sodium bicarbonate;

[0036] (3) Low-temperature infiltration: The treated peanut kernels and the infiltration solution were placed in a sandwich vacuum infiltration tank at a mass ratio of 1:1.5. The variable frequency ultrasonic assisted system was turned on (set power 200 W, frequency 28 kHz), and the infiltration was carried out at a vacuum degree of -0.08 MPa and a temperature of 35°C for 60 minutes.

[0037] (4) Staged cooking: Transfer the peanut kernels and the flavoring liquid into a cooking pot and cook them at 80°C for 20 minutes. Then add 0.02% sodium citrate based on the weight of the peanut kernels, stir evenly, and then heat to 92°C and cook for 8 minutes.

[0038] (5) Rapid cooling: Remove the peanut kernels immediately after cooking, spray them with ice water to reduce their core temperature to below 10°C within 3 minutes, remove them and drain;

[0039] (6) Modified atmosphere packaging: The cooled peanut kernels are packed into bags, filled with a mixture of nitrogen and carbon dioxide (volume ratio 7:3), heat-sealed, and the residual oxygen content in the bag is controlled to ≤0.5%.

[0040] Example 2

[0041] Instant boiled peanuts prepared by a low-temperature permeation process are prepared from the following raw materials in parts by weight:

[0042] 100 parts of fresh flower kernels, 2.2 parts of edible salt, 1.2 parts of white sugar, 0.5 parts of star anise, 0.4 parts of cinnamon bark, 0.25 parts of liquorice, 180 parts of purified water, 0.1 parts of sodium D-erythorbate, and 0.02 parts of nisin;

[0043] The fresh peanut kernels are peanut kernels with skins and a moisture content of 32% within 24 hours after harvesting, and the particle size ranges from 9 to 11 mm;

[0044] The processing method includes the following steps:

[0045] (1) Pretreatment: After screening, fresh flower kernels were soaked in 0.8% sodium bicarbonate solution at 42°C for 18 minutes, removed and rinsed once with purified water;

[0046] (2) Preparation of flavoring solution: Add edible salt, white sugar, star anise, cinnamon bark, and licorice to purified water, heat and stir at 65°C for 45 minutes, filter through a 200-mesh filter cloth, add sodium D-isoascorbate and nisin to the filtrate, stir and dissolve, and obtain flavoring solution; the osmotic pressure of the flavoring solution was measured to be 1350 mOsm / L, and the pH was adjusted to 6.2 with sodium bicarbonate;

[0047] (3) Low-temperature infiltration: The treated peanut kernels and the infiltration solution were placed in a sandwich vacuum infiltration tank at a mass ratio of 1:1.8. The variable frequency ultrasonic assisted system was turned on (set power 300 W, frequency 28 kHz), and the infiltration was carried out at a vacuum degree of -0.085 MPa and a temperature of 38°C for 50 minutes.

[0048] (4) Staged cooking: Transfer the peanut kernels and the flavoring solution into a cooking pot and cook them at 83°C for 18 minutes. Then, add 0.035% sodium citrate based on the weight of the peanut kernels, stir evenly, and then heat to 94°C and cook for 6 minutes.

[0049] (5) Rapid cooling: Remove the peanut kernels immediately after cooking, spray them with ice water to reduce their core temperature to 8°C within 3 minutes, remove them and drain;

[0050] (6) Modified atmosphere packaging: The cooled peanut kernels are packed into bags, filled with a mixture of nitrogen and carbon dioxide (volume ratio 7:3), heat-sealed, and the residual oxygen content in the bag is controlled to ≤0.4%.

[0051] Example 3

[0052] Instant boiled peanuts prepared by a low-temperature permeation process are prepared from the following raw materials in parts by weight:

[0053] 100 parts of fresh flower kernels, 3 parts of edible salt, 2 parts of white sugar, 0.8 parts of star anise, 0.6 parts of cinnamon bark, 0.4 parts of liquorice, 200 parts of purified water, 0.15 parts of sodium D-erythorbate, and 0.03 parts of nisin;

[0054] The fresh peanut kernels are peanut kernels with a moisture content of 35% within 24 hours after harvesting, and the particle size range is 10-12 mm;

[0055] The processing method comprises the following steps:

[0056] (1) Pretreatment: After screening, the fresh peanut kernels are soaked in 1% sodium bicarbonate solution at 45°C for 15 minutes, and then rinsed once with pure water;

[0057] (2) Preparation of permeation liquid: edible salt, white sugar, star anise, cassia bark, and licorice are added to pure water, heated and stirred at 70°C for 30 minutes, filtered through a 200-mesh filter cloth, and then the filtrate is added with sodium D-isoascorbate and nisin, stirred and dissolved to obtain the permeation liquid; the osmotic pressure of the permeation liquid is measured to be 1500 mOsm / L, and the pH is adjusted to 6.5 with sodium bicarbonate;

[0058] (3) Low-temperature permeation: the treated peanut kernels and the permeation liquid are put into a sandwich type vacuum permeation tank at a mass ratio of 1:2, the variable frequency ultrasonic auxiliary system is turned on (set power 400W, frequency 28kHz), and permeation is carried out at a vacuum degree of-0.09MPa and a temperature of 40°C for 40 minutes;

[0059] (4) Sectional cooking: the peanut kernels and the permeation liquid are transferred into a cooking pot, first cooked at 85°C for 15 minutes, then 0.05% sodium citrate is added based on the weight of the peanut kernels, stirred uniformly, and then heated to 95°C for 5 minutes;

[0060] (5) Rapid cooling: the peanut kernels are immediately taken out after cooking, and the center temperature is reduced to 5°C within 3 minutes by spraying ice water, and then taken out and drained;

[0061] (6) Modified atmosphere packaging: the cooled peanut kernels are packed into bags, filled with a mixture of nitrogen and carbon dioxide gas (volume ratio 7:3), heat sealed, and the residual oxygen in the packaging bag is controlled to be ≤0.3%.

[0062] Comparative Example 1

[0063] Process comparison: no vacuum ultrasonic assistance

[0064] A boiled peanut, the raw materials and processing method of which are basically the same as those of Example 2, the only difference being that:

[0065] In step (3) low-temperature permeation, the vacuum and ultrasonic auxiliary system are not turned on, and only soaking is carried out at normal pressure and 38°C for 50 minutes.

[0066] Comparative Example 2

[0067] Process comparison: single cooking

[0068] A boiled peanut, whose raw materials and processing method are basically the same as those in Example 2, the only difference is:

[0069] Step (4) was changed from staged cooking to single temperature cooking: cooking directly at 95°C for 25 minutes without adding sodium citrate.

[0070] Comparative Example 3

[0071] Raw material comparison: no compound preservatives

[0072] A boiled peanut is prepared by the same processing method as in Example 2, except that the raw materials do not contain sodium D-erythorbate and nisin.

[0073] Comparative Example 4

[0074] Process comparison: natural cooling

[0075] A boiled peanut, whose raw materials and processing method are basically the same as those in Example 2, the only difference is:

[0076] Step (5) was changed from rapid cooling to natural cooling at room temperature. The cooling time was about 25 minutes, and the center temperature of the peanut kernel dropped to room temperature (25° C.).

[0077] Comparative Example 5

[0078] Ingredient comparison: flavor recipe imbalance

[0079] A boiled peanut is prepared by the same processing method as in Example 2, except that the flavoring material ratio in the raw materials is modified to: 3.5 parts of edible salt, 0.3 parts of white sugar, 1.2 parts of star anise, 0.9 parts of cinnamon bark, and 0.1 parts of liquorice.

[0080] Test Example 1

[0081] Comparative testing of texture characteristics and peanut integrity

[0082] Objective: To verify the effect of low-temperature penetration and segmented cooking process on maintaining the intact morphology and ideal texture (mouthfeel) of peanut kernels.

[0083] method:

[0084] Sample preparation: 100 pieces of instant peanut samples prepared in Example 2, Comparative Example 1 (without vacuum ultrasound), Comparative Example 2 (single cooking) and Comparative Example 4 (natural cooling) were taken.

[0085] Integrity testing: Manually count the number of peanuts in each sample group that were completely covered with skin and intact, and calculate the peanut skin integrity rate (%). Also count the number of peanuts with broken skin (peanut skin with a broken area > 1 / 4 of the peanut) and calculate the broken skin rate (%).

[0086] Texture Analysis (TPA): Using a texture analyzer (model: TA.XT Plus), 10 peanut kernels of uniform particle size were selected. Testing parameters: P / 36R probe, pre-test speed of 1.0 mm / s, test speed of 1.0 mm / s, post-test speed of 10.0 mm / s, compression ratio of 50%, trigger force of 5 g. The average values ​​of hardness (g), springiness (springiness), and chewiness (mJ) were recorded.

[0087] The results are shown in Table 1.

[0088] Table 1: Comparative test of texture characteristics and peanut integrity

[0089]

[0090] Conclusion: Example 2 of the present invention had the highest peanut skin integrity rate and the lowest shell breakage rate, indicating that vacuum ultrasound-assisted penetration effectively reduced physical damage to the skin during subsequent thermal processing. Its hardness, elasticity, and chewiness were balanced, resulting in a moderately soft and firm texture with a pleasant chewiness. Comparative Example 1 experienced uneven flavor penetration, requiring greater chewing effort and resulting in a firmer texture. Comparative Example 2 experienced excessive softening and a doughy texture due to prolonged high-temperature cooking. Comparative Example 4 experienced a deterioration in texture due to slow cooling and residual heat. This demonstrates that low-temperature penetration and rapid cooling are crucial for maintaining the excellent texture of peanuts.

[0091] Test Example 2

[0092] Flavor penetration uniformity test

[0093] Objective: To verify the effect of vacuum ultrasound-assisted low-temperature permeation process on improving the permeation uniformity of flavor substances (represented by salt and sugar).

[0094] method:

[0095] Sample preparation: Take the peanut samples prepared in Example 2 and Comparative Example 1, and randomly select 20 peanut kernels for each group.

[0096] Sample processing: Carefully peel off the red seed coat of each peanut kernel, collect the kernel and coat of each peanut separately and crush them separately.

[0097] Testing: High-performance liquid chromatography (HPLC) was used to determine the sodium chloride and sucrose content of each peanut kernel and skin sample. The salt / sugar ratio (R) of the kernel to skin sample was calculated for each of the 20 peanut samples. The coefficient of variation (CV%) of this ratio was also calculated to assess flavor uniformity. A lower CV% indicates more uniform flavor distribution.

[0098] The results are shown in Table 2.

[0099] Table 2: Comparison of flavor penetration uniformity (n=20)

[0100]

[0101] Conclusion: The salt and sugar content in the peanut kernels of Example 2 was significantly higher than that of Comparative Example 1, with a smaller difference between the kernel and shell (R value closer to 1). In particular, the coefficient of variation (CV%) of flavor compounds in the kernel was much lower than that of Comparative Example 1. This demonstrates that the vacuum ultrasound-assisted permeation process of the present invention significantly promotes the efficient and uniform migration of flavor compounds into the interior of the peanut kernels, resolving the core issue of traditional soaking methods: salty on the outside, bland on the inside, and uneven flavor.

[0102] Test Example 3

[0103] Accelerated Storage Test (ASLT)

[0104] Objective: To verify the synergistic effect of composite preservatives and modified atmosphere packaging on extending the shelf life of products.

[0105] method:

[0106] Sample grouping: Samples of Example 2, Comparative Example 3 (without composite preservative) and commercially available ordinary vacuum-packed boiled peanuts (as a control) were taken.

[0107] Storage conditions: The samples were placed in a 37°C incubator for accelerated storage testing. According to the ASLT principle, one day of storage at 37°C is equivalent to 3-4 days of storage at room temperature (25°C).

[0108] Index testing: Sampling and testing on days 0, 30, 60, 90, 120, 150, and 180.

[0109] Peroxide Value (POV): Determined according to GB 5009.227-2016, it measures the degree of rancidity of fats and oils. A POV exceeding 0.25g / 100g is considered the critical point for fat rancidity.

[0110] Total colony count: determined according to GB 4789.2-2016.

[0111] Sensory evaluation: Blind evaluation is conducted by 10 trained judges, and a score below 6 points (out of 10 points) is considered unacceptable.

[0112] Table 3: Comparison of key indicators of shelf life

[0113]

[0114] Conclusion: After 180 days of accelerated storage, the peroxide value of the product of the present invention (Example 2) still did not exceed the safety limit, the total bacterial count remained at an extremely low level, and the sensory quality was stable. Its expected shelf life at room temperature far exceeded 9 months. However, due to the lack of sodium D-isoascorbate (antioxidant) and nisin (antibacterial), the shelf life of Comparative Example 3 was significantly shortened. This proves that the combination of composite preservatives and modified atmosphere packaging can effectively inhibit oil oxidation and microbial growth, which is the key to achieving long-term shelf life.

[0115] Test Example 4

[0116] Nutrient retention test

[0117] Objective: To evaluate the protective effect of low-temperature segmented cooking on heat-sensitive nutrients (vitamin E and folic acid) in peanuts.

[0118] method:

[0119] Sample preparation: Take samples of fresh peanut kernels (control), Example 2, and Comparative Example 2 (single high-temperature cooking).

[0120] Detection: HPLC was used to determine the content of α-tocopherol (the main active form of vitamin E) and folic acid in the samples. The retention rate (%) of each processed sample was calculated based on the nutritional content of fresh peanut kernels (100%).

[0121] The results are shown in Table 4.

[0122] Table 4: Comparison of retention rate of heat-sensitive nutrients (%)

[0123] Group α-Tocopherol retention rate Folate retention rate Fresh peanut kernels 100.0 100.0 Example 2 88.5±3.2 85.1±4.5 Comparative Example 2 72.4±4.1 60.3±5.8

[0124] Conclusion: The present invention's low-temperature permeation followed by staged heating significantly reduces the damage to heat-sensitive nutrients. The retention rates of vitamin E and folic acid in Example 2 were significantly higher than those in the traditional high-temperature, long-term cooking process (Comparative Example 2). This demonstrates that this process achieves both ripening and sterilization while better preserving the nutritional value of peanuts.

[0125] Test Example 5

[0126] Sensory evaluation blind test

[0127] Objective: To comprehensively evaluate the overall acceptance of the product of the present invention in terms of color, shape, aroma, taste and flavor.

[0128] method:

[0129] Jury: Recruiting 50 sensory evaluators (half male and half female, aged 20-55).

[0130] Samples: randomly numbered Example 2, Comparative Example 2, Comparative Example 5 (flavor imbalance) and a commercially available high-end brand product.

[0131] Evaluation indicators: A 9-point preference rating system (1 = extremely dislike, 9 = extremely like) is used to evaluate the product's color (milky yellow and uniform), shape (complete particles), aroma (harmony between the original peanut aroma and spices), taste (moderately soft and hard, without a soft or hard core), flavor (sweet and salty, rich and uniform flavor) and overall preference.

[0132] The results are shown in Table 5.

[0133] Table 5: Average scores of sensory evaluation (n=50)

[0134]

[0135] Conclusion: The product of the present invention (Example 2) received the highest scores across all sensory indicators, with particular strengths in morphological integrity, mouthfeel, and flavor uniformity. Its overall preference rating was significantly higher than that of the other comparison groups (P < 0.05). This demonstrates the scientific nature and superiority of the present invention's processing technology and flavor formulation, resulting in high-quality, ready-to-eat boiled peanuts that are more popular with consumers.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, based on the innovative concept of the present invention, changes and modifications to the embodiments described herein, or equivalent structural or equivalent process transformations made using the contents of the present invention specification, directly or indirectly applying the above technical solutions to other related technical fields are all included in the scope of protection of the patent of the present invention.

Claims

1. A method for processing instant boiled peanuts based on a low-temperature infiltration process, characterized in that: The raw materials include, by weight, 100 parts of fresh flower kernels, 1.5-3 parts of edible salt, 0.5-2 parts of white sugar, 0.3-0.8 parts of star anise, 0.2-0.6 parts of cinnamon bark, 0.1-0.4 parts of licorice, 150-200 parts of purified water, 0.05-0.15 parts of sodium D-erythorbate, and 0.01-0.03 parts of nisin. The fresh flower kernels are shelled peanut kernels harvested within 24 hours, with a moisture content of 30-35%, and a particle size range of 8-12 mm. The method comprises the following steps: (1) Pretreatment: After screening, fresh flower kernels are soaked in 0.5-1% sodium bicarbonate solution at 40-45°C for 15-20 minutes; (2) Preparation of flavoring solution: Add edible salt, white sugar, star anise, cinnamon bark, and licorice to purified water, heat and stir at 60-70°C for 30-60 minutes, filter, and add sodium D-isoascorbate and nisin to obtain flavoring solution; (3) Low-temperature infiltration: soak the treated peanut kernels in the infiltration solution and infiltrate for 40-60 minutes at a vacuum degree of -0.08 to -0.09 MPa and a temperature of 35-40°C; (4) Staged cooking: first cook at 80-85℃ for 15-20 minutes, then heat to 92-95℃ and cook for 5-8 minutes; (5) Rapid cooling: Use ice water spray to reduce the core temperature of the peanut kernel to below 10°C within 3 minutes; (6) Modified atmosphere packaging: Fill the bag with a mixture of nitrogen and carbon dioxide, and the residual oxygen content in the bag is ≤0.5%.

2. The processing method according to claim 1, characterized in that: The osmotic pressure of the odor solution in step (3) is adjusted to 1200-1500 mOsm / L, and the pH value is controlled at 6.0-6.

5.

3. The processing method according to claim 1, characterized in that: The low-temperature infiltration in step (3) is carried out with the assistance of ultrasound, with an ultrasonic power of 200-400W and a frequency of 28kHz.

4. The processing method according to claim 1, characterized in that: The low-temperature permeation equipment in step (3) adopts a sandwich vacuum permeation tank, which is equipped with a variable frequency ultrasonic auxiliary system.

5. The processing method according to claim 1, characterized in that: During the staged cooking process in step (4), 0.02-0.05% of the weight of the peanut kernel is added with sodium citrate as a texture improver.

6. The processing method according to claim 1, characterized in that: After cooling in step (5), the hardness of the peanut kernel is controlled at 2000-2500g.

7. Instant boiled peanuts prepared by the method according to any one of claims 1 to 6, characterized in that: The water activity of the product Aw≤0.85, the total colony count≤100CFU / g.

8. The instant boiled peanuts according to claim 7, characterized in that: The peanut skin integrity rate is ≥95%, the broken skin rate is ≤3%, and the peanut skin is uniformly milky yellow.

9. The instant boiled peanuts according to claim 7, characterized in that: In the accelerated storage test at 37°C, the peroxide value of the product reached 0.25g / 100g for no less than 180 days, aflatoxin B1 was not detected, and the detection limit was 0.1μg / kg.

10. The instant boiled peanuts according to claim 7, characterized in that: The shelf life of the product is not less than 9 months at room temperature.

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