Preparation technology of long-acting fresh-keeping honeyed raw lemon slice at room temperature

Abstract

The application provides a kind of normal temperature long-acting fresh-keeping honeyed slice of lemon slice preparation technology, it is related to food processing technical field, it is characterized in that, including the following steps: raw material screening pretreatment, color protection hardening treatment, gradient negative pressure honey dipping, low temperature predehydration, instantaneous mild sterilization, modified atmosphere packaging, light-proof aseptic packaging, constant temperature curing warehouse.The sugar content of the honeyed lemon slice is 63-67 °Bx, the water activity is less than or equal to 0.82, the pH is less than or equal to 2.5, the total phenol retention rate is greater than or equal to 85%, and the vitamin C retention rate is greater than or equal to 70%.The application has the advantages that: by optimizing raw material pretreatment, color protection hardening, gradient negative pressure honey dipping, low temperature dehydration, precise sterilization, modified atmosphere packaging and constant temperature curing whole set process, honeyed lemon slice with bright color, compact taste, mellow flavor and high nutrient retention rate is prepared, normal temperature long-acting storage of the product is realized, cold storage is not needed, and the product quality and market applicability are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, and in particular to a method for preparing honey-preserved raw lemon slices with long-lasting preservation at room temperature. Background Technology

[0002] Lemons are rich in functional nutrients such as vitamin C, total phenols, and citric acid, and have the effects of quenching thirst, anti-oxidation, and regulating metabolism. They are a popular food and medicine ingredient in daily life. Honey-preserved lemon slices are widely used in tea drinks, desserts, and ready-to-eat snacks due to their sweet and sour taste, convenience, and unique flavor, and market demand continues to grow.

[0003] Currently, the traditional process for preparing candied lemon slices suffers from several drawbacks. Firstly, the single method of pre-treatment and sterilization of raw materials fails to completely eliminate microorganisms on the surface, easily leading to mold and spoilage later on. Secondly, the lack of a dedicated color-protecting and hardening process makes the lemon pulp highly susceptible to oxidative browning during processing, resulting in a dull color and poor appearance. Thirdly, the traditional method of soaking in sugar at normal pressure and temperature results in slow and uneven sugar penetration, significant differences in sweetness between the inside and outside of the lemon slices, and prolonged soaking time, which can lead to the loss of nutrients from the pulp and unstable sugar binding. Fourthly, the crude dehydration process cannot accurately control the product's moisture content, easily leading to problems such as excessive moisture causing microbial growth or insufficient moisture resulting in a dry and hard texture. Fifthly, the simple sterilization process and finished product packaging result in a very short shelf life at room temperature, low integration of sugar solution and pulp, a thin flavor, poor taste complexity, and a tendency for sugar return and water separation during storage, leading to poor product stability.

[0004] Therefore, there is an urgent need for a room-temperature, long-lasting preservation technology for honey-preserved raw lemon slices, which can produce honey-preserved lemon slices with a long shelf life, good color, rich nutrition, and excellent taste under room-temperature conditions. Summary of the Invention

[0005] The purpose of this invention is to provide a long-lasting, room-temperature-controlled technology for preparing raw lemon slices preserved in honey. This technology solves the problems of severe browning, significant nutrient loss, low sugar extraction efficiency, and short shelf life at room temperature in existing technologies. Through the synergistic effect of processes such as composite color-protecting hardening, gradient negative pressure honey preservation, low-temperature pre-dehydration, instantaneous mild sterilization, modified atmosphere packaging, and constant-temperature ripening, long-lasting preservation of lemon slices at room temperature is achieved, while maximizing the preservation of the lemon's nutritional components and natural flavor.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0007] A technology for preparing room-temperature, long-lasting, honey-preserved raw lemon slices includes the following steps:

[0008] S1. Raw material screening and pretreatment: Select fresh lemons with uniform maturity, no rot, no insect infestation, and no mechanical damage as raw materials. Wash, disinfect, and drain the lemons. Then cut them into uniform thin slices of 2-3mm. Manually remove the lemon seeds to avoid the bitter taste caused by the lemon seeds. Finally, clean and complete lemon slices are obtained.

[0009] The disinfection process employs a combined treatment method of ozone water and acidic electrolyzed water. Specifically, fresh lemons are first soaked in ozone water with a concentration of 1.0-2.0 mg / L for 3-5 minutes to remove insect eggs, pesticide residues, and most microorganisms from the surface. Then, they are sprayed and rinsed with acidic electrolyzed water with a pH of 2.5-3.0 for 1-2 minutes to deeply sterilize and inhibit bacteria. Finally, they are thoroughly rinsed with sterile pure water to remove residual disinfectant.

[0010] S2. Color protection and hardening treatment: Soak lemon slices in a compound color protection and hardening solution at room temperature for 6-10 minutes. The color protection components inhibit oxidative browning, and the hardening components solidify the pulp tissue. After soaking, remove the lemon slices, rinse them thoroughly with sterile water to remove any residual color protection solution, and drain them for later use.

[0011] The composite color-protecting hardening solution is composed of the following components in parts by weight: 100 parts sterile water, 0.1 parts citric acid, 0.05 parts sodium isoascorbate, and 0.1 parts calcium chloride.

[0012] S3. Gradient negative pressure honey soaking: The lemon slices treated in step S2 are placed in a compound honey soaking solution. The mass ratio of the compound antibacterial honey soaking solution to the lemon slices is 4:1. A segmented low-temperature negative pressure sugar soaking process is adopted, with the overall sugar soaking temperature controlled at 22-25℃. First, the lemon slices are soaked in a vacuum of -0.06MPa for 2 hours to achieve initial sugar penetration. Then, the vacuum is adjusted to -0.09MPa for 3 hours to enhance the deep penetration of the sugar solution, thus completing the gradient sugar soaking process and ensuring uniform penetration of the sugar solution and full fusion of flavors.

[0013] The compound honey-soaking liquid is composed of the following components by weight percentage: 60% mature multifloral honey, 25% fructose, 10% sucrose, and 5% sterile pure water;

[0014] S4. Low-temperature pre-dehydration: Spread the lemon slices soaked in honey in step S3 on the drying rack to avoid stacking and sticking. Dry with hot air for 35-45 minutes under constant conditions of 40-45℃ and wind speed of 1.2m / s. Precisely control the degree of dehydration so that the final moisture content of the finished product is stable at 32%-35%, taking into account both the soft and glutinous texture of the product and its storage stability.

[0015] S5. Instantaneous and gentle sterilization: The dehydrated lemon slices are instantaneously pasteurized in an 85℃ water bath for 30 seconds to achieve thorough sterilization while preserving nutrients and pulp texture to the maximum extent. After sterilization, a segmented cooling method is used to lower the temperature. First, the slices are pre-cooled in 40-45℃ warm water for 5-8 minutes to buffer the temperature difference, and then transferred to 15-20℃ cold water to cool to room temperature. This completely avoids problems such as cracking of lemon slice pulp, soft texture, and deterioration of tissue structure caused by heat shock.

[0016] S6. Modified atmosphere aseptic packaging: In the aseptic workshop, the cooled lemon slices are packaged with amber-colored light-proof packaging material and sealed with a mixture of nitrogen and carbon dioxide to isolate external oxygen and light, inhibiting oxidation and microbial growth.

[0017] The mixture consists of the following components by mass percentage: 90% nitrogen and 10% carbon dioxide.

[0018] S7. Constant Temperature Maturation and Storage: After packaging, the product is placed in a room temperature and light-proof environment for 72 hours for constant temperature maturation to stabilize the sugar molecular structure, promote the deep integration of the flavor of the honey liquid and the flavor of lemon pulp, and eliminate the raw sugar taste of the product. After maturation, the product passes the sampling inspection and is then stored at room temperature.

[0019] The room-temperature long-lasting preserved honey-soaked lemon slices prepared using the technology of this invention have the following specifications: sugar content 63-67°Bx, water activity ≤0.82, pH ≤2.5, total phenol retention rate ≥85%, and vitamin C retention rate ≥70%.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. The dual disinfection process of ozone water and acidic electrolyzed water is adopted to improve the sterilization coverage, reduce the risk of product spoilage, and enhance food safety.

[0022] 2. The citric acid in the compound color-protecting hardening solution adjusts the pH of the system and inhibits the activity of polyphenol oxidase; sodium isoascorbate is a highly effective antioxidant that blocks the oxidative degradation of vitamin C and total phenols; calcium chloride solidifies the cell wall tissue of lemon pulp, improves the firmness of the pulp, and reduces the occurrence of problems such as browning, softening, and misshapen lemon slices.

[0023] 3. The gradient negative pressure design achieves a gradual sugar-soaking effect, first shallow penetration and then deep immersion, so that the sugar content of the lemon slices is uniform inside and out, effectively improving the taste of the product. The negative pressure sugar-soaking process has a short sugar-soaking time, which improves production efficiency.

[0024] 4. The constant temperature ripening process stabilizes the sugar structure, avoiding problems such as sugar return, water separation, and flavor loss during product storage, allowing the fruit pulp and honey flavor to fully blend, and the product taste becomes more mellow with storage time. Attached Figure Description

[0025] Figure 1 This is a flowchart of a process for preparing honey-preserved raw lemon slices with long-lasting preservation at room temperature, according to the present invention.

[0026] Figure 2 This is a schematic diagram of the composite color-protecting and curing treatment in this invention.

[0027] Figure 3 This is a schematic diagram of the segmented gradient negative pressure sugar impregnation process in this invention. Detailed Implementation

[0028] To make the content of this invention easier to understand, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings.

[0029] Example 1

[0030] A technology for preparing room-temperature, long-lasting, honey-preserved raw lemon slices includes the following steps:

[0031] S1. Raw Material Screening and Pretreatment: Select fresh lemons of moderate maturity, free from mechanical damage and pests / diseases, with Eureka lemons being the preferred variety. Rinse the lemons in running water to remove surface dirt. First, soak them in ozone water with a concentration of 1.5 mg / L for 4 minutes, then rinse them with acidic electrolyzed water with a pH of 2.8 for 1.5 minutes, and finally rinse them with sterile pure water. After disinfection, place the lemons in a sterile environment to drain the surface moisture. Cut the drained lemons into uniform 2.5 mm slices using a stainless steel slicer, and manually remove the lemon seeds to obtain lemon slices.

[0032] S2. Color-protecting and curing treatment: Prepare the composite color-protecting and curing solution: Weigh out 100 parts by weight of sterile water, 0.1 parts by weight of citric acid, 0.05 parts by weight of sodium isoascorbate, and 0.1 parts by weight of calcium chloride, and stir until completely dissolved. Add the lemon slices obtained in step S1 to the composite color-protecting and curing solution and soak at room temperature for 8 minutes, stirring gently during this time to ensure the lemon slices are fully in contact with the color-protecting solution. After removal, rinse twice with sterile water and drain the surface moisture.

[0033] S3. Gradient Negative Pressure Honey Soaking: Prepare the compound honey soaking solution: Weigh out 60% mature wildflower honey, 25% fructose, 10% sucrose, and 5% sterile pure water by mass percentage, and stir at 22-25℃ until completely dissolved and homogeneous. Place the lemon slices treated in step S2 into a vacuum sugar soaking tank, add the compound honey soaking solution (compound honey soaking solution to lemon slices mass ratio 4:1). Start the vacuum system, first evacuate to -0.06MPa, and soak at 22-25℃ for 2 hours; then adjust the vacuum to -0.09MPa and continue soaking at 22-25℃ for 3 hours. The entire sugar soaking process takes 5 hours. After sugar soaking, release the vacuum, remove the lemon slices, and drain off excess honey soaking solution.

[0034] S4. Low-Temperature Pre-Dehydration: Lay the lemon slices soaked in honey in step S3 in a single layer on a stainless steel sieve, avoiding overlap. Place them in a hot air drying oven and dry for 40 minutes at a temperature of 42℃ and a wind speed of 1.2m / s. Turn them over periodically during the drying process to ensure uniform drying. After drying, the moisture content of the lemon slices was measured to be 33.5%, which meets the control requirement of 32%~35%.

[0035] S5. Instantaneous and gentle sterilization: Pack the dried lemon slices from step S4 into food-grade heat-resistant packaging bags, pre-quantitatively package each bag, seal them, and place them in an 85℃ constant temperature water bath for 30 seconds for sterilization. Immediately after sterilization, remove them and pre-cool them in 42℃ warm water for 6 minutes, then transfer them to 18℃ cold water to cool to room temperature to avoid thermal shock that could cause the lemon slices to deteriorate.

[0036] S6. Modified atmosphere aseptic packaging: In an aseptic workshop, the lemon slices cooled in step S5 are placed into an amber-colored light-proof packaging bag. First, a vacuum is drawn, then a mixed gas consisting of 90% nitrogen and 10% carbon dioxide is filled in, and the bag is heat-sealed to ensure that the residual oxygen content inside the packaging is less than 0.5%.

[0037] S7. Constant Temperature Maturation and Storage: Place the packaged product in a room temperature, light-proof environment for 72 hours to mature, allowing the sugar structure to stabilize further and the flavor components to fully blend. After maturation, inspect according to product quality standards. Once the inspection is passed, store the product at room temperature.

[0038] The product specifications of the honey-preserved lemon slices prepared in this embodiment are as follows:

[0039]

[0040] Example 2

[0041] The difference between this embodiment and Embodiment 1 is that:

[0042] In step S1, the ozone water concentration is 1.0 mg / L, and the soaking time is 5 min; the pH value of the acidic electrolyzed water is 2.5, and the rinsing time is 2 min.

[0043] In step S2, the color-protecting hardening solution is soaked at room temperature for 6 minutes.

[0044] In step S3, the segmented negative pressure honey soaking process is as follows: first soaking in a vacuum of -0.06MPa for 2 hours, then soaking in a vacuum of -0.09MPa for 3 hours, with the temperature controlled at 22℃.

[0045] In step S4, the hot air drying conditions are: temperature 40℃, wind speed 1.2m / s, drying time 45min, and moisture content controlled at 32%.

[0046] In step S5, the segmented cooling method is as follows: first, pre-cool in 40℃ warm water for 8 minutes, and then transfer to 15℃ cold water to cool to room temperature.

[0047] The remaining steps and parameters are the same as in Example 1.

[0048] The product specifications of the honey-preserved lemon slices prepared in this embodiment are as follows:

[0049]

[0050] Example 3

[0051] The difference between this embodiment and Embodiment 1 is that:

[0052] In step S1, the ozone water concentration is 2.0 mg / L, and the soaking time is 3 min; the pH value of the acidic electrolyzed water is 3.0, and the rinsing time is 1 min.

[0053] In step S2, the color-protecting hardening solution is soaked at room temperature for 10 minutes.

[0054] In step S3, the segmented negative pressure honey soaking process is as follows: first soaking in a vacuum of -0.06MPa for 2 hours, then soaking in a vacuum of -0.09MPa for 3 hours, with the temperature controlled at 25℃.

[0055] In step S4, the hot air drying conditions are: temperature 45℃, wind speed 1.2m / s, drying time 35min, and moisture content controlled at 35%.

[0056] In step S5, the segmented cooling method is as follows: first, pre-cool in 45℃ warm water for 5 minutes, and then transfer to 20℃ cold water to cool to room temperature.

[0057] The remaining steps and parameters are the same as in Example 1.

[0058] The product specifications of the honey-preserved lemon slices prepared in this embodiment are as follows:

[0059]

[0060] Comparative Example 1: No color-protecting and hardening treatment performed.

[0061] The difference between this comparative example and Example 1 is that the color-protecting and hardening treatment in step S2 is omitted, and the sliced ​​lemons are directly subjected to the gradient negative pressure honey soaking in step S3. The remaining steps are the same as in Example 1.

[0062] The results showed that the lemon slices prepared in Comparative Example 1 exhibited significant browning during the honey-soaking process, with the finished product ranging in color from dark brown to brownish-red, and its appearance quality was significantly inferior to that of Example 1. After three months of storage at room temperature, the browning intensified further, rendering the product uncommercial.

[0063] Comparative Example 2: Sugar immersion using traditional atmospheric pressure

[0064] The difference between this comparative example and Example 1 is that step S3 uses the traditional atmospheric pressure sugar immersion method, that is, the lemon slices are soaked in the compound honey immersion solution for 24 hours under normal temperature and pressure conditions, during which the honey immersion solution is replaced with fresh honey immersion solution once. The remaining steps are the same as in Example 1.

[0065] The results showed that the soaking time in Comparative Example 2 was longer than that in Example 1, but the sugar penetration in the finished product was uneven, with the sugar content in the center being significantly lower than that on the surface, resulting in inconsistent taste. Furthermore, the prolonged soaking caused the lemon slices to soften, leading to insufficient toughness in the finished product.

[0066] Comparative Example 3: No modified atmosphere packaging

[0067] The difference between this comparative example and Example 1 is that step S6 uses only ordinary vacuum packaging and does not involve filling with a mixture of nitrogen and carbon dioxide gas. The remaining steps are the same as in Example 1.

[0068] The results showed that the product of Comparative Example 3 began to show oxidative browning after 6 months of storage at room temperature, with darkening of color and deterioration of flavor; after 12 months of storage, the browning was severe and the product quality declined significantly.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A technology for preparing honey-preserved raw lemon slices with long-lasting preservation at room temperature, characterized in that, Includes the following steps: S1. Raw material screening and pretreatment: Select mature and undamaged fresh lemons. After washing, disinfecting and draining, cut the lemons into uniform thin slices of 2-3mm and remove the lemon seeds to obtain lemon slices. S2. Color protection and hardening treatment: Soak lemon slices in the composite color protection and hardening solution at room temperature for 6-10 minutes, then rinse with sterile water. S3, Gradient negative pressure honey soaking: Place the lemon slices treated in step S2 into the compound honey soaking solution and use a segmented low-temperature negative pressure sugar soaking process for 5 hours; S4. Low-temperature pre-dehydration: Spread the lemon slices soaked in honey in step S3 flat and dry them with hot air at 40-45℃ and a wind speed of 1.2m / s for 35-45 minutes, controlling the moisture content of the finished product to be 32%-35%. S5. Instantaneous mild sterilization: Instantaneous pasteurization in an 85℃ water bath for 30 seconds, followed by cooling to room temperature; S6. Modified atmosphere aseptic packaging: In the aseptic workshop, amber-colored light-proof packaging material is used, and nitrogen and carbon dioxide are mixed for modified atmosphere packaging to isolate oxygen and light. S7. Constant temperature aging and storage: After packaging, let it stand at room temperature in the dark for 72 hours to age, stabilize the sugar structure and blend the flavor. After passing the inspection, it will be stored in the warehouse.

2. The technology for preparing room-temperature, long-lasting, honey-preserved raw lemon slices according to claim 1, characterized in that, The disinfection described in step S1 uses a combined treatment method of ozone water and acidic electrolyzed water. Specifically, the solution is first soaked in ozone water with a concentration of 1.0-2.0 mg / L for 3-5 minutes, then rinsed with acidic electrolyzed water with a pH of 2.5-3.0 for 1-2 minutes, and finally rinsed with sterile pure water.

3. The technology for preparing room-temperature, long-lasting, honey-preserved raw lemon slices according to claim 1, characterized in that, The composite color-protecting and hardening solution described in step S2 is composed of the following components in parts by weight: 100 parts sterile water, 0.1 parts citric acid, 0.05 parts sodium isoascorbate, and 0.1 parts calcium chloride.

4. The technology for preparing room-temperature, long-lasting, honey-preserved raw lemon slices according to claim 1, characterized in that, The compound honey-soaking liquid described in step S3 is composed of the following components by mass percentage: 60% mature wildflower honey, 25% fructose, 10% sucrose, and 5% sterile pure water.

5. The technology for preparing room-temperature, long-lasting, honey-preserved raw lemon slices according to claim 1, characterized in that, The segmented low-temperature negative pressure sugar soaking process described in step S3 is as follows: first, soaking at a vacuum degree of -0.06MPa for 2 hours, and then adjusting the vacuum degree to -0.09MPa for 3 hours.

6. The technology for preparing room-temperature, long-lasting, honey-preserved raw lemon slices according to claim 1, characterized in that, In step S3, the temperature of the segmented low-temperature negative pressure sugar soaking process is controlled at 22-25℃, and the mass ratio of the compound antibacterial honey soaking solution to lemon slices is 4:

1.

7. The technology for preparing room-temperature, long-lasting, honey-preserved raw lemon slices according to claim 1, characterized in that, After sterilization in step S5, a segmented cooling method is adopted: first, pre-cool in 40-45℃ warm water for 5-8 minutes, and then transfer to 15-20℃ cold water to cool to room temperature, so as to avoid thermal shock causing deterioration of the lemon slices.

8. The technology for preparing room-temperature, long-lasting, honey-preserved raw lemon slices according to claim 1, characterized in that, The mixed gas in step S6 consists of the following components by mass percentage: 90% nitrogen and 10% carbon dioxide.

9. The room-temperature long-lasting freshness-preserving honey-soaked lemon slices obtained by the preparation technique according to any one of claims 1-8, characterized in that, The honey-preserved lemon slices have a sugar content of 63-67°Bx, a water activity of ≤0.82, and a pH of ≤2.

5.

10. The room-temperature long-lasting freshness-preserving honey-soaked lemon slices obtained by the preparation technique according to any one of claims 1-8, characterized in that, The total phenol retention rate of the honey-preserved lemon slices is ≥85%, and the vitamin C retention rate is ≥70%.

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