Slicing and fresh-keeping method for fruits and vegetables

Abstract

The invention provides a slicing preservation method for fruits and vegetables, which comprises the following steps: firstly, cleaning, peeling, denucleating and deseeding complete fruits and vegetables, and then slicing the fruits and vegetables in a low-temperature environment by using a disinfected cutter; completely immersing the obtained slices in a composite fresh-keeping solution for treatment; taking out the treated slices, using filtered and sterilized low-temperature high-speed air flow to blow away residual liquid on the surfaces, and then sealing the slices and a modified atmosphere preservative in a high-barrier packaging bag; the packaged fruit and vegetable slices are placed in a low-temperature environment to be stored and transported; the low-temperature composite fresh-keeping liquid containing the edible calcium salt, the antioxidant and the pH regulator is adopted for treating the slices, juice loss and tissue softening caused by cutting are reduced, meanwhile, the low-pH environment and the antioxidant act jointly, the activity of polyphenol oxidase and other enzymes is greatly inhibited, and therefore enzymatic browning is prevented, and the fresh-keeping effect is good. And the fresh appearance color of the product is kept.

Description

Technical Field

[0001] The present invention relates to the technical field of fruit and vegetable preservation, and in particular to a method for preserving slices of fruits and vegetables. Background Art

[0002] Sliced ​​fruit and vegetable products are popular among consumers because they are convenient to eat and rich in nutrition. However, the cutting process will cause mechanical damage to the tissue, leading to a series of changes such as juice loss, accelerated enzymatic browning, and increased microbial infection. These products are extremely prone to spoilage and have a shelf life that is significantly shorter than that of whole fruits and vegetables. Therefore, there is an urgent need to develop an efficient, safe and scalable sliced ​​fruit and vegetable preservation technology to reduce food waste, increase product added value and protect consumer health.

[0003] Existing technologies used to preserve fruit and vegetable slices mainly include chemical immersion preservation, physical low-temperature preservation, and modified atmosphere packaging (MAP). The chemical immersion method often uses a single colorant or preservative, which has limited treatment effects, and excessive use may cause consumers to worry about food safety. Although physical low-temperature preservation can inhibit microbial activity and respiration, it cannot effectively solve the problems of enzymatic browning and juice loss. Traditional modified atmosphere packaging is usually sealed after filling a certain proportion of mixed gas. This is a passive preservation method. The gas environment in the package will change rapidly due to product respiration and external temperature fluctuations, making it difficult to maintain the ideal ratio for a long time, resulting in unstable preservation effect and even accelerated spoilage.

[0004] Therefore, in response to the above-mentioned problems, the present invention proposes a method for preserving slices of fruits and vegetables. Summary of the Invention

[0005] In order to overcome the problems of the existing technology such as single preservation effect, possible excessive use of chemical reagents and unstable passive atmosphere environment, the present invention proposes a comprehensive preservation method that integrates chemical treatment, surface precision dehydration and active atmosphere control. This method solves the problems of browning, rotting and quality deterioration of sliced ​​fruits and vegetables through the synergistic effect of multiple barriers, thereby significantly extending their commercial shelf life and ensuring food safety.

[0006] The technical solution of the present invention is: a method for preserving slices of fruits and vegetables, comprising the following steps: S1, wash, peel, core and seed the whole fruits and vegetables, and then slice them using a sterilized knife under low temperature environment; S2, completely immersing the slices obtained above in the composite preservative solution for treatment, so as to provide comprehensive protection for the slices; S3: Remove the slices after the above treatment and use a sterilized, filtered, low-temperature, high-speed airflow to blow away any residual liquid on the surface to prevent excess moisture accumulation in the package. The slices are then sealed in a high-barrier packaging bag along with a modified atmosphere preservative to create a stable microenvironment. S4, placing the packaged fruit and vegetable slices in a low temperature environment for storage and transportation.

[0007] Preferably, the low temperature environment in step S1 is 4-10°C, which can effectively inhibit enzyme activity and microbial reproduction while avoiding chilling damage to fruits and vegetables. The slices are in the form of sheets, blocks or strips with a thickness of 5-15 mm, ensuring that the fresh-keeping treatment liquid can effectively penetrate and the product has a consistent taste. The knife is wiped with 75% edible-grade alcohol.

[0008] Preferably, the composite fresh-keeping solution in step S2 is an aqueous solution prepared by dissolving edible calcium salt, antioxidant and pH regulator in sterile water, and the temperature thereof is 2-8°C.

[0009] Preferably, the edible calcium salt is calcium chloride or calcium lactate, and its concentration in the composite preservative solution is 0.5%-2.0% w / v. This concentration range can effectively strengthen the cell wall structure without affecting the taste. The antioxidant is ascorbic acid, and its concentration in the composite preservative solution is 0.5%-1.5% w / v, which can effectively prevent enzymatic browning. The pH regulator is citric acid, and its added amount is used to adjust the pH value of the composite preservative solution to 3.0-4.0, thereby creating an environment that is not conducive to the growth of most spoilage microorganisms.

[0010] Preferably, the immersion treatment time in step S2 is 2-5 minutes. This time period allows the effective ingredients to take effect without causing excessive water absorption and softening of the fruit and vegetable tissues and loss of nutrients. During the treatment process, slight stirring is required to ensure that the preservative liquid is in full contact with the surface of the slice. This step can ensure that all surfaces of each fruit and vegetable slice are in full and uniform contact with the preservative liquid, avoiding the generation of treatment dead corners, thereby achieving a consistent and reliable preservation effect.

[0011] Preferably, the temperature of the filtered and sterilized high-speed airflow in step S3 is 4-10° C., the wind speed is 10-20 m / s, and the processing time is 1-3 minutes.

[0012] Preferably, the packaging bag in step S3 is a composite polyethylene packaging bag with polyvinylidene chloride or ethylene-vinyl alcohol copolymer as the intermediate barrier layer, and its oxygen permeability is lower than 20 cm³ / m²·24h·atm under the conditions of 23°C and 0% RH.

[0013] Preferably, the modified atmosphere preservative in step S3 is a solid mixture pre-sealed in a breathable small bag, the mixture consisting of ascorbic acid, sodium bicarbonate and a carrier. After being sealed together with the fruit and vegetable slices in the packaging bag, the mixture can actively consume the oxygen in the bag and release a small amount of carbon dioxide through a chemical reaction, and ultimately adjust and maintain the gas composition in the packaging bag to: oxygen concentration 3%-5%, carbon dioxide concentration 5%-15%, and nitrogen concentration 80%-92%. This low-oxygen and high-carbon dioxide environment can effectively inhibit the respiration of fruits and vegetables and the growth of aerobic microorganisms.

[0014] Preferably, the mass percentages of the components in the modified atmosphere preservative are: ascorbic acid 30%-50%, sodium bicarbonate 20%-40%, and silica carrier 15%-45%, wherein ascorbic acid is the main oxygen-consuming component, sodium bicarbonate is the gas-producing component, and the silica carrier plays the role of adsorption, dispersion, and stabilization of the reaction.

[0015] Preferably, the low temperature environment in step S4 is a refrigeration temperature of 1-4° C., and the relative humidity of the environment is maintained at 85%-95%.

[0016] Beneficial effects of the present invention: 1. The present invention treats slices with a low-temperature composite preservative solution containing edible calcium salts, antioxidants, and pH regulators. Calcium ions combine with pectin acid in the cell walls of fruits and vegetables to form calcium pectate, significantly enhancing the structural strength and mechanical integrity of the cell walls and reducing juice loss and tissue softening caused by cutting. The low pH environment and antioxidants work together to significantly inhibit the activity of enzymes such as polyphenol oxidase, thereby preventing enzymatic browning and maintaining the fresh appearance and color of the product.

[0017] 2. The present invention uses low-temperature sterilized airflow to dehydrate the slices treated with preservative liquid before packaging, thereby removing moisture attached to the surface of the slices, effectively reducing the humidity in the sealed package, destroying the moist environment suitable for microbial reproduction, and thus significantly inhibiting the growth rate of bacteria, mold and yeast.

[0018] 3. The present invention replaces traditional passive gas-filled packaging with an active modified atmosphere preservative. This preservative can continuously and actively consume oxygen and release carbon dioxide after the package is sealed, thereby adjusting the atmosphere inside the package to a low-oxygen, high-carbon dioxide state. This effectively inhibits the respiration intensity and ethylene catalysis of fruit and vegetable slices, delaying metabolism and the aging process. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 What is shown is a schematic diagram of the workflow of the present invention. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0021] See also Figure 1 The present invention provides an embodiment: a method for preserving slices of fruits and vegetables, comprising the following steps: First, use clean water or slightly acidic electrolyzed water that meets food hygiene standards to thoroughly wash the fruits and vegetables (in actual application, the pH value of slightly acidic electrolyzed water is usually 5.0-6.5. It contains hypochlorous acid, which can effectively kill microorganisms and leaves no residue after decomposition. It is a safe non-thermal sterilization method) to remove surface dust, pesticide residues and some microorganisms. Then, according to the type of fruits and vegetables, they are manually or mechanically peeled, cored or seeded to obtain clean edible parts. After completing the preliminary treatment, the fruits and vegetables are transferred to a low-temperature and clean workroom with a constant ambient temperature of 4-10°C (this low-temperature environment uses low temperature to inhibit the respiration intensity and enzyme activity of fruits and vegetables, delaying quality from the source). Deterioration), all cutting knives and equipment are pre-wiped and disinfected with 75% edible-grade alcohol (although alcohol disinfection is common, it is highly volatile and cannot provide long-term bactericidal protection. Therefore, the disinfection operation must be repeated regularly before each shift and during each shift to ensure sterility). This minimizes the introduction of microorganisms at the source. Finally, according to product requirements, fruits and vegetables are precisely cut into slices, blocks or strips with a uniform thickness of 5-15 mm (uniform cutting thickness is very important. Excessive thickness differences may lead to uneven penetration and dehydration in subsequent processing, thereby affecting the consistency of the overall preservation effect). The entire cutting process is completed quickly in a low-temperature environment.

[0022] The fruit and vegetable slices obtained in the previous step are immediately and completely immersed in a pre-prepared composite preservative solution cooled to 2-8°C for treatment. The preservative solution is an aqueous solution prepared by dissolving a specific concentration of food-grade additives in sterile water. Its core components include 0.5%-2.0% (w / v) calcium chloride or calcium lactate as a calcium source to strengthen the cell wall structure, 0.5%-1.5% (w / v) ascorbic acid as an antioxidant to effectively inhibit the activity of polyphenol oxidase, and citric acid is used to adjust the pH value of the solution to a weak acid range of 3.0-4.0 to create an environment that is not conducive to the growth of microorganisms. The fruit and vegetable slices are immersed in this low-temperature preservative solution for 2-5 minutes, and are gently stirred during this period to ensure that the surface of each slice is fully and evenly in contact with the preservative solution components.

[0023] The fruit and vegetable slices treated with the preservative solution are taken out of the solution and immediately transferred to a low-temperature air drying device equipped with a high-efficiency air filter (in actual production lines, this equipment is usually a tunnel-type device, and the slices pass through a section of low-temperature clean high-speed airflow on the conveyor belt to achieve continuous production). The surface of the fruit and vegetable slices is blown for 1-3 minutes using a clean high-speed airflow that has been filtered and sterilized and is controlled at a temperature of 4-10°C and a wind speed of 10-20m / s (the temperature of the airflow must match or be slightly lower than the product temperature. If room temperature or hot air is used, the surface of the fruit and vegetable slices will be blown for 1-3 minutes). Wind will cause the surface temperature of the slices to rise, which will accelerate the deterioration of quality), so as to quickly remove the excess moisture remaining on the surface of the slices, thereby eliminating the risk of providing a breeding ground for microbial growth in the subsequent sealed packaging. After the surface dehydration is completed, the fruit and vegetable slices are quantitatively weighed and quickly packed into a high-barrier packaging bag together with a breathable pouch with a built-in modified atmosphere preservative (the modified atmosphere is pre-sealed in a breathable paper-plastic pouch, allowing gas exchange while preventing direct contact between the contents and the food). The packaging bag is made of a composite polyethylene material with PVDC or EVOH as a barrier layer It is made of (taking EVOH as an example, its barrier properties are excellent, but its disadvantage is that the barrier properties will decrease when the humidity is high. Therefore, the outer layer of composite PE material not only provides heat sealing performance, but also protects the EVOH middle layer from the influence of high humidity environment, ensuring the stable low oxygen permeability of the package throughout the shelf life). Its oxygen permeability is lower than 20cm³ / m²·24h·atm. The packaging bag is immediately vacuumed and filled with a small amount of nitrogen before heat sealing. The modified atmosphere preservative in the bag is a kind of 30%-50% ascorbic acid, 20%-40% sodium bicarbonate and the balance of silica carrier. A solid mixture composed of two bodies, which can actively consume the oxygen in the bag and release carbon dioxide through chemical reactions after sealing, and ultimately dynamically adjust and stabilize the atmosphere inside the package at an ideal fresh-keeping gas ratio of 3%-5% O2 concentration, 5%-15% CO2 concentration, and 80%-92% N2 concentration (the principle is that ascorbic acid, as a strong reducing agent, can quickly undergo oxidation reaction with oxygen in the microenvironment provided by alkaline sodium bicarbonate to generate carbon dioxide. The silica carrier is used to absorb moisture that may be produced by the reaction, maintaining the looseness of the powder system and the reaction efficiency).

[0024] After the final sealing, the product is quickly moved into a cold storage at 1-4°C for storage. The entire storage and subsequent transportation and sales links need to be kept in a cold chain environment at this temperature. At the same time, the relative humidity of the environment must be maintained between 85% and 95% to prevent condensation on the surface of the packaging bag or water loss of the product. Under such low temperature conditions, combined with the stable and suitable gas environment established in the packaging and the enhanced surface treatment of the product itself, the respiration intensity, enzymatic browning reaction and growth and reproduction of various microorganisms of fruit and vegetable slices can be synergistically and effectively inhibited, thereby effectively ensuring the nutritional value and food safety of the product throughout its shelf life and extending the shelf life of the product.

[0025] Furthermore, the present invention provides an embodiment, which illustrates an active atmosphere-controlled preservative: A pre-formulated modified atmosphere preservative (composed of 40% ascorbic acid, 30% sodium bicarbonate, and 30% silica carrier) is sealed in a micro-breathable paper bag and then sealed together with 300 grams of pre-treated and preservative-soaked apple slices in a high-barrier packaging bag with an OTR value of 15 cm³ / m²·24h·atm. In the initial period after sealing, the initial oxygen content in the bag is approximately 21%. Subsequently, the ascorbic acid in the preservative, acting as a strong reducing agent, begins to preferentially undergo an oxidation reaction with the oxygen in the package. At the same time, the sodium bicarbonate decomposes in the acidic environment (produced by fruit and vegetable respiration and ascorbic acid) to release carbon dioxide. This chemical reaction process can last for several to dozens of hours, thereby creating a low-oxygen environment that can effectively inhibit the respiration intensity and enzymatic browning of the apple slices without relying on expensive inflation equipment.

[0026] Furthermore, the present invention provides an embodiment: For soft and juicy kiwifruit slices, a high-concentration preservative solution (2.0% calcium lactate, 1.5% sodium ascorbate) and a short soaking time (2 minutes) combined with gentle airflow (10 m / s, 3 minutes) are used for treatment. This quickly strengthens the cell walls while minimizing mechanical damage and juice loss. For carrot strips, which have a harder texture and brown more slowly, a lower-limit preservative solution concentration (0.5% calcium chloride, 0.5% ascorbic acid) and an upper-limit soaking time (5 minutes) are used in combination with stronger airflow (20 m / s, 1 minute) to ensure full penetration of the active ingredients while achieving efficient dehydration. By controlling the combination of key parameters (concentration, time, and airflow), the present invention can be widely applied to a variety of fruit and vegetable products, and has high flexibility and potential for industrial application.

[0027] The above are merely preferred embodiments of the present invention and do not limit the present invention in any other form. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preserving slices of fruits and vegetables, characterized in that: The following steps are included: S1, wash, peel, core and seed the whole fruits and vegetables, and then slice them using a sterilized knife under low temperature environment; S2, completely immersing the fruit and vegetable slices obtained in step S1 in a composite preservative liquid for treatment; S3, taking out the fruit and vegetable slices processed in step S2, using a high-speed airflow that has been filtered and sterilized to remove excess liquid from the surface, and then sealing the slices together with the modified atmosphere preservative in a high-barrier packaging bag; S4, storing and transporting the fruit and vegetable slices packaged in step S3 in a low temperature environment.

2. A method for preserving slices of fruits and vegetables according to claim 1, characterized in that: The low temperature environment in step S1 is 4-10° C., and the slices are in the form of flakes, blocks or strips with a thickness of 5-15 mm.

3. The method for preserving slices of fruits and vegetables according to claim 1, characterized in that: The composite fresh-keeping solution in step S2 is an aqueous solution prepared by dissolving edible calcium salt, antioxidant and pH regulator in sterile water, and the temperature thereof is 2-8°C.

4. The method for preserving slices of fruits and vegetables according to claim 3, characterized in that: The edible calcium salt is calcium chloride or calcium lactate, and its concentration in the composite fresh-keeping liquid is 0.5%-2.0% w / v. The antioxidant is ascorbic acid, and its concentration in the composite fresh-keeping liquid is 0.5%-1.5% w / v. The pH regulator is citric acid, and its addition amount is used to adjust the pH value of the composite fresh-keeping liquid to 3.0-4.

0.

5. The method for preserving slices of fruits and vegetables according to claim 1, characterized in that: The immersion treatment in step S2 lasts for 2-5 minutes, and slight stirring is required during the treatment to ensure that the preservative liquid is in full contact with the surface of the slices.

6. The method for preserving slices of fruits and vegetables according to claim 1, characterized in that: The temperature of the filtered and sterilized high-speed airflow in step S3 is 4-10° C., the wind speed is 10-20 m / s, and the processing time is 1-3 minutes.

7. The method for preserving slices of fruits and vegetables according to claim 1, characterized in that: The packaging bag in step S3 is a composite polyethylene packaging bag with polyvinylidene chloride or ethylene-vinyl alcohol copolymer as an intermediate barrier layer, and its oxygen permeability is lower than 20 cm³ / m²·24h·atm under the conditions of 23°C and 0% RH.

8. The method for preserving slices of fruits and vegetables according to claim 1, characterized in that: The modified atmosphere preservative in step S3 is a solid mixture pre-sealed in a breathable small bag. The mixture consists of ascorbic acid, sodium bicarbonate, and a carrier. After being sealed together with the fruit and vegetable slices in the packaging bag, the mixture can actively consume the oxygen in the bag and release a small amount of carbon dioxide through a chemical reaction, ultimately adjusting and maintaining the gas composition in the packaging bag to: oxygen concentration of 3%-5%, carbon dioxide concentration of 5%-15%, and nitrogen concentration of 80%-92%.

9. The method for preserving slices of fruits and vegetables according to claim 8, characterized in that: The mass percentages of the components in the modified atmosphere preservative are: 30%-50% ascorbic acid, 20%-40% sodium bicarbonate, and 15%-45% silicon dioxide carrier.

10. The method for preserving slices of fruits and vegetables according to claim 1, characterized in that: The low temperature environment in step S4 is a refrigeration temperature of 1-4° C., and the relative humidity of the environment is maintained at 85%-95%.

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