Liquid nitrogen quick-freezing preservation method for swingle and integrated frame type manual swingle peeling tool

Abstract

This invention relates to a liquid nitrogen quick-freezing preservation method for Ruichang yam and an integrated frame-type manual yam peeler, belonging to the field of agricultural product preservation and processing technology. The preservation method includes raw material harvesting and full-scene manual peeling, simultaneous enzyme inactivation, color protection, and mucus removal with boiling tea, pre-vacuum packaging, three-stage gradient quick-freezing, and low-temperature constant-temperature refrigeration. The peeler is an integrated structure, including a flat wedge-shaped cleaning head (1), a cylindrical handle (2), and a closed square frame-type blade holder (3) connected in sequence. This invention completely solves the industry pain points of traditional peelers such as peeling and clogging, excessive pitting residue, and high wear and tear. At the same time, by combining tea enzyme inactivation with gradient liquid nitrogen quick-freezing technology, the shelf life of Ruichang yam is extended to more than 12 months, and the browning degree is reduced by more than 75%, making it suitable for farmers and small processing plants.

Description

Technical Field

[0001] This invention relates to the field of agricultural product preservation and processing technology, and in particular to a liquid nitrogen quick-freezing preservation method for Ruichang yam and an integrated frame-type manual yam peeling knife. Background Technology

[0002] Ruichang yam is a local yam characterized by its dense and fine texture, white and moist stem flesh, glutinous texture and fragrant aroma, and its ability to remain soft even after prolonged cooking.

[0003] Ruichang yam is characterized by its irregular shape, which presents challenges such as easy breakage during transportation, difficulty in peeling, and difficulty in storage, troubling both merchants and consumers for many years. For example, peeling is difficult (manual peeling can easily cause skin allergies and itching in those with yam intolerance), transportation is difficult (easily broken, and the broken surface can lead to infection and rot), and it is not suitable for storage (drying and dehydration at room temperature causes nutrient loss, making peeling even more difficult). Studies have shown that vegetables treated with quick-freezing technology retain significantly higher levels of nutrients such as vitamin C compared to slow freezing. Merchants have tried various storage and transportation methods, such as home freezing (around -18℃), vacuum storage, and industrial quick-freezing (around -35℃), but none have achieved the fresh taste of Ruichang yam. Summary of the Invention

[0004] To address the problem of poor appearance and difficulty in peeling Ruichang yams, which prevents farmers from monetizing one-third of their yams, this invention provides a liquid nitrogen quick-freezing preservation method for Ruichang yams and an integrated frame-type manual yam peeler. This method helps preserve the vitamins, minerals, and active ingredients such as yam polysaccharides in the yams. This invention completely solves the industry pain points of traditional peelers, such as peeling and clogging, leaving many pits and resulting in high losses. Furthermore, by combining tea enzyme inactivation with gradient liquid nitrogen quick-freezing technology, the shelf life of Ruichang yams is extended to over 12 months, and browning is reduced by more than 75%, making it suitable for farmers and small processing plants.

[0005] To achieve the above objectives, the present invention provides a method for quick-freezing and preserving Ruichang yam using liquid nitrogen, comprising the following steps performed sequentially: S1. Harvest fresh Ruichang yam from the period from the Beginning of Winter to the Minor Snow. After removing the root head and fibrous roots, use an integrated frame-type manual yam peeler. The peeler sequentially uses the inclined main blade to process large flat areas, the side secondary cutting blade to fit uneven curved surfaces, and the wedge-shaped cleaning head at the tail end to clean all pits and crevices, completing efficient peeling in all scenarios. After rinsing with clean water to remove residual skin and mucus, the yam slices are cut into pieces with a thickness of 0.5~2cm. S2. Immediately place the yam slices into boiling tea water for a quick scalding treatment of 5-30 seconds. This process simultaneously inactivates polyphenol oxidase, prevents browning and protects the color, and removes residual mucus from the surface of the yam. After scalding, quickly remove the slices and place them in sterile cold water at 0-4℃ to cool and stop the enzymatic reaction. Drain the free water from the surface to obtain pretreated yam slices. S3. Use food-grade nylon extra-high pressure resistant 8-filament composite film packaging bags to single-layer flat vacuum seal the pre-treated yam slices, with a vacuum degree of 0.08~0.1MPa, to obtain individually packaged yam slices; S4. Individually packaged yam slices are subjected to gradient quick-freezing in sequence. First, they are pre-cooled at -(50~70)℃ for 15~45 min, then quick-frozen at -(70~90)℃ for 15~45 min, and then transferred to a liquid nitrogen environment at -(100~120)℃ for continued quick-freezing until the surface temperature of the yam slices drops below -20℃ and the core temperature drops below -18℃, thus obtaining the quick-frozen yam product. S5. Store the quick-frozen yam products in a sealed cold storage at a constant temperature of -(18~25)℃, with the temperature fluctuation not exceeding ±1℃.

[0006] Furthermore, in step S1, under manual operation of the integrated frame-type manual yam peeler, the peeling time for a single Ruichang yam in all scenarios is 12~25s, the yam stem and flesh loss rate after peeling is ≤2.5%, the residual rate of skin debris in pits and crevices is ≤0.4%, and there is no phenomenon of skin jamming or clogging in the blade holder.

[0007] Furthermore, in step S1, the fresh Ruichang yam is the Ruishu No. 1 variety grown in the core production area of ​​Ruichang City, Jiangxi Province, with a single root weight of 200-500g, and free from disease, mold, and mechanical damage.

[0008] Further, in step S2, the boiling tea water solution is obtained by using green tea or oolong tea residue as raw material, adding drinking water at a material-to-liquid ratio of 1:(50~200) (g / mL), boiling for 10~20 minutes, and then filtering to remove the tea residue; the surface free water is drained by low-temperature cold air draining, with a cold air temperature of 2~6℃, a wind speed of 1~3m / s, and a draining time of 5~10 minutes.

[0009] Furthermore, in step S3, the vacuum degree of the vacuum-sealed packaging is controlled at 0.08~0.1MPa, the single bag packaging amount is 100~1000g, the heat seal strength of the packaging bag is ≥30N / 15mm, and it can withstand low temperature impact of -120℃ without cracking.

[0010] Furthermore, in step S4, the total freezing time is controlled at 75~90 minutes, so that the yam slices can quickly pass through the maximum ice crystal formation zone of -1℃~-5℃ within 15 minutes; after the quick-freezing is completed, the center temperature of the yam slices is -19℃~-22℃.

[0011] Furthermore, in step S5, the refrigerated storage temperature of the quick-frozen yam product is -20~22℃, and the product shelf life is ≥12 months. It is preferable to avoid frequent opening and closing of the storage door and temperature fluctuations during storage.

[0012] The second aspect of the present invention provides an integrated frame-type manual yam peeler according to the method of the present invention, comprising an integrally formed knife body, wherein the knife body is composed of a tail end cleaning head 1, a cylindrical handle part 2 and a closed square frame-type knife holder part 3 connected in sequence. The closed square frame-type tool holder 3 forms a through-type skin outlet 4 in the middle. An inclined main blade 5 is fixedly installed on the inner side of the upper frame of the tool holder. An arc-shaped secondary cutting edge 6 is provided on the inner side of one side frame of the tool holder, and the other side frame is a smooth support edge. The tail end cleaning head 1 is a flat wedge-shaped structure integrally formed from the same material as the handle part 2, with all edges rounded and no sharp blades.

[0013] Furthermore, the inclined main blade 5 is fixedly installed on the inner side of the upper frame at an inclination angle of 30°~45°, with the cutting edge facing the skin outlet 4, and the cutting edge of the main blade 5 extending out of the inner side of the upper frame by a height of 1.0~1.5mm. The main blade 5 is made of food-grade stainless steel, with a cutting edge thickness of 0.1~0.15mm and a cutting angle of 15°~20°.

[0014] Furthermore, the radius of curvature of the arc-shaped secondary cutting edge 6 is 25~40mm, and the height of the cutting edge extending out of the inner side frame is 0.8~1.2mm, which is used to fit the irregular curved surface of the yam for cutting.

[0015] Furthermore, the length of the through-type skin outlet 4 is 20~30mm, the width is 10~15mm, and the inner wall of the skin outlet is smoothly chamfered with a chamfer radius of 0.5~1mm.

[0016] Furthermore, the tip angle of the flat wedge-shaped cleaning head 1 is 30°~45°, and the radius of its edge rounded corner is ≥0.8mm, which can extend into the crevices of yam pits with a depth of 0.5~3mm to complete the removal of skin flakes.

[0017] Furthermore, the entire blade body is integrally injection molded from food-grade PP or ABS material, with a total length of 120~150mm and a weight of 15~30g.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: (1) Preserving the excellent texture and flavor of Ruichang yam: The simultaneous inactivation of enzymes and removal of mucilage by boiling tea water, combined with the process of packaging first and then quick-freezing with gradient liquid nitrogen, inhibits enzymatic reactions and oxidation, which helps to preserve the vitamins, minerals, and active ingredients such as yam polysaccharides in the yam. Furthermore, the quick-freezing process makes the ice crystals formed inside the cells very small and uniform, which can minimize the risk of large ice crystals piercing the cell walls, thereby preventing the yam tissue from becoming soft and mushy and losing juice after thawing, and better maintaining its original powdery or crisp texture and sweet flavor. The shelf life of Ruichang yam is extended to more than 12 months, and the browning degree is reduced by more than 75%, preserving the crisp texture and nutritional components to the greatest extent.

[0019] (2) High efficiency and low loss in peeling: The integrated frame blade holder completely solves the problem of peeling and clogging. The three blades work together to achieve peeling in all scenarios. The peeling loss rate is ≤2.5%, the pitting residue rate is ≤0.4%, and the efficiency is more than 30% higher than that of ordinary peeling knives.

[0020] (3) Safe, practical, convenient and high-value products: The knives have no sharp edges, making them safe to use; the overall process does not require complex equipment, is simple to operate, and is suitable for large-scale application by farmers and small processing plants. Quick-frozen yams are less prone to frostbite spots and shrinkage, resulting in better appearance, less weight loss, and higher commercial value. Attached Figure Description

[0021] Figure 1 shows a picture of fresh yam; Figure 2 shows the liquid nitrogen preservation method after 6 months; Figure 3 shows the storage of ordinary commodities in a cold storage facility for 12 months; Figure 4 shows the result after 12 months of quick-frozen storage. Figure 5 is a schematic diagram of the overall structure of an integrated frame-type manual yam peeler according to one embodiment of the present invention.

[0022] Explanation of reference numerals in the attached figures: 1. Clean the tail end of the head; 2. Cylindrical handle section; 3. Closed square frame-type tool holder; 4. Through-type skin outlet; 5. Inclined main blade; 6. Arc-shaped secondary cutting edge. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] In this application, it should be noted that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0025] In this application, unless otherwise expressly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. The term "multiple" refers to two or more, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0026] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0027] In this application, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] like Figure 5 The diagram shows a three-dimensional structural schematic of the cutting tool of the present invention, clearly demonstrating the overall integrated structure of the tool. The flat wedge-shaped cleaning head 1 at the tail end is integrally formed with the cylindrical handle portion 2. The front end of the handle portion 2 is connected to a closed square frame-type tool holder portion 3. A through-type skin outlet 4 is formed in the middle of the tool holder portion 3. An inclined main blade 5 is fixedly installed on the inner side of the upper frame, an arc-shaped secondary cutting edge 6 is provided on the inner side of the right frame, and the left frame is a smooth support edge.

[0030] 1. Experimental materials and reagents The experimental Ruichang yam: Fresh Ruishu No. 1 yam harvested from the core production area of ​​Ruichang City, Jiangxi Province, between the beginning of winter and the beginning of snow, was selected. It was free from disease, mold, and mechanical damage, and the entire process was completed within 2 hours after harvesting. Tea: Commercially available food-grade green tea (one bud and two leaves, broken leaves, new tea from the current year); Packaging material: Food-grade nylon premium freeze-resistant high-pressure 8-filament composite film packaging bag, with specifications suitable for single bag packaging volume, and low-temperature impact resistance in accordance with GB 4806.7-2016 standard for plastic materials and products for food contact. All other reagents are food-grade and comply with relevant national food safety standards.

[0031] 2. Core Equipment One-piece frame manual yam peeler (see) Figure 5 ); Programmable cabinet type liquid nitrogen quick-freezing machine (temperature control range -120℃ to room temperature, temperature control accuracy ±1℃); Food-grade vacuum packaging machine (ultimate vacuum degree 0.1MPa, sealing width 15mm); Spectrophotometer, texture analyzer, electronic balance (accuracy 0.01g), constant temperature cold storage and other routine laboratory testing and processing equipment.

[0032] 3. Standardized testing methods Knife holder jamming rate: After peeling 100 yams consecutively, the number of times the knife holder jammed and blocked the yam was counted. The calculation formula is: Jamming rate = Number of jams / Total number of peels × 100%; Cleaning time: The average time required to clean the remaining skin flakes and slime from the knife after peeling; Browning degree: The supernatant of yam homogenate was taken by spectrophotometry and the absorbance value was measured at a wavelength of 420 nm. The lower the absorbance, the lighter the browning degree. Juice loss rate: Calculated by weighing after thawing, formula: Juice loss rate = (Sample mass before thawing - Mass of drained sample after thawing) / Sample mass before thawing × 100%; Peeling loss rate: Calculation formula: Peeling loss rate = (mass of yam before peeling - mass of yam after peeling) / mass of yam before peeling × 100%; Texture characteristics: The hardness and crispness of the yam slices were measured using a texture analyzer to characterize the retention of texture. Sensory evaluation: A panel of 10 professional food sensory evaluators will score the food on a 100-point scale based on four dimensions: color, taste, aroma, and texture. The higher the score, the better the quality. Shelf life verification: Store in a constant temperature cold storage at -20℃±1℃, and test the quality of samples regularly. The shelf life is the longest storage time that meets the food standards in terms of sensory and physicochemical indicators.

[0033] Example 1 Pre-treatment: Fresh Ruishu No. 1 yam harvested from the core production area of ​​Fanzhen, Ruichang City, Jiangxi Province, between the beginning of winter and the beginning of snow, is peeled immediately after manually removing the rhizome and fibrous roots using the integrated frame-type manual yam peeler of this invention. First, use the main blade installed at a 35° angle to cut a large, flat surface of the yam, automatically controlling the peeling thickness to about 1mm. Then, use the side arc-shaped secondary cutting edge to cut the yam by fitting it against the curved and uneven surface. Finally, use the 35° flat wedge-shaped cleaning head at the end to scrape away all residual skin flakes in pits and crevices of all sizes.

[0034] The entire peeling process for a single yam takes 18 seconds, with the operating environment temperature maintained at 12℃. After rinsing with running water, the yam is immediately sliced ​​into uniform pieces 1cm thick, with the entire processing time controlled within 1.5 hours after harvesting.

[0035] Test results showed that after peeling, the yam stem and flesh loss rate was 2.1%, the residual skin debris rate in pits and crevices was 0.2%, the skin jamming rate of the knife holder after 100 consecutive peels was 0%, and the knife cleaning time was ≤5s.

[0036] Simultaneous enzyme inactivation, color protection, and mucus removal: Before slicing, green tea residue was added to food-grade drinking water at a material-to-liquid ratio of 1:100 (g / mL), boiled for 15 minutes, and then filtered to remove the tea residue, yielding a tea boiling water extract. The yam slices were immediately placed in the continuously boiling tea water solution for a quick 3-second blanching treatment, simultaneously inactivating polyphenol oxidase, preventing browning and protecting the color, and removing the mucus from the yam surface. After blanching, the slices were quickly removed and immediately placed in sterile cold water at 2℃ for 10 seconds to stop the enzymatic reaction. Then, they were drained for 8 minutes at 4℃ with a wind speed of 2m / s to remove free surface moisture, resulting in pre-treated yam slices.

[0037] Pre-vacuum packaging: The pre-treated yam slices are laid flat in a single layer in a food-grade nylon extra-high pressure resistant 8-filament composite film packaging bag, with a single bag packaging amount of 500g. Vacuum sealing is carried out under a vacuum degree of 0.095MPa, with a sealing heat seal strength of 36N / 15mm, no air leakage and no wrinkles, to obtain individually packaged yam slices.

[0038] Gradient quick-freezing: Arrange the individually packaged yam slices flat on the rack of the programmable liquid nitrogen quick-freezing machine without stacking or squeezing, and execute the three-stage gradient liquid nitrogen quick-freezing program: Pre-cooling stage: Pre-cool at a constant temperature of -60℃ for 30 minutes; First stage of quick freezing: quick freezing treatment at a constant temperature of -80℃ for 30 minutes; The second stage of quick freezing: transfer to a liquid nitrogen low-temperature environment at -110℃ and continue quick freezing until the surface temperature of the yam slices drops to -22℃ and the core temperature drops to -19℃. Stop quick freezing. The total quick freezing time is 82 minutes, and the quick-frozen yam product is obtained.

[0039] Low-temperature constant temperature cold storage: Immediately transfer the quick-frozen yam products to a constant temperature cold storage at -20℃±1℃ for sealed storage. During storage, avoid frequent opening and closing of the cold storage door and control the temperature fluctuation range to not exceed ±1℃.

[0040] Example 2 Pre-treatment: Fresh Ruishu No. 1 yam harvested from the core production area of ​​Fanzhen, Ruichang City, Jiangxi Province, between the beginning of winter and the beginning of snow, is peeled immediately after manually removing the rhizome and fibrous roots using the integrated frame-type manual yam peeler of this invention. First, use the main blade installed at a 30° angle to cut a large, flat surface of the yam, automatically controlling the peeling thickness to about 1mm. Then, use the side arc-shaped secondary cutting edge to cut the yam by fitting it against the curved and uneven surface. Finally, use the 35° flat wedge-shaped cleaning head at the end to scrape away all residual skin flakes in pits and crevices of all sizes.

[0041] The entire peeling process for a single yam takes 25 seconds, with the operating environment temperature maintained at 12℃. After rinsing with running water, the yam is immediately sliced ​​into uniform pieces 1cm thick, with the entire processing time controlled within 1.5 hours after harvesting.

[0042] Test results showed that after peeling, the yam stem and flesh loss rate was 2.4%, the residual skin debris rate in pits and crevices was 0.4%, the skin jamming rate of the knife holder after 100 consecutive peels was 0%, and the knife cleaning time was ≤5s.

[0043] Simultaneous enzyme inactivation, color protection, and mucus removal: Before slicing, green tea was added to food-grade drinking water at a material-to-liquid ratio of 1:200 (g / mL), boiled for 10 minutes, and then filtered to remove tea residue, yielding a tea boiling water extract. The yam slices were immediately placed in the continuously boiling tea water solution for a quick 3-second blanching treatment, simultaneously inactivating polyphenol oxidase, preventing browning and protecting color, and removing the mucus from the yam surface. After blanching, the slices were quickly removed and immediately placed in sterile cold water at 0℃ for 5 seconds to terminate the enzymatic reaction. Then, they were drained at 2℃ with a wind speed of 1m / s for 7 minutes to remove free surface moisture, resulting in pretreated yam slices.

[0044] Pre-vacuum packaging: The pre-treated yam slices are laid flat in a single layer in a food-grade nylon extra-high pressure resistant 8-filament composite film packaging bag, with a single bag packaging amount of 100g. Vacuum sealing is carried out under a vacuum degree of 0.08MPa, and the heat seal strength of the seal is 32N / 15mm, resulting in individually packaged yam slices.

[0045] Gradient liquid nitrogen quick-freezing: Individually packaged yam slices are laid flat on the rack of a programmable liquid nitrogen quick-freezing machine without stacking or compression, and a three-stage gradient liquid nitrogen quick-freezing program is executed: Pre-cooling stage: Pre-cool at a constant temperature of -60℃ for 30 minutes; First stage of quick freezing: quick freezing treatment at a constant temperature of -80℃ for 30 minutes; The second stage of quick freezing: transfer to a liquid nitrogen low-temperature environment at -100℃ and continue quick freezing until the surface temperature of the yam slices drops to -20℃ and the core temperature drops to -18℃. Stop quick freezing. The total quick freezing time is 75 minutes, and the quick-frozen yam product is obtained.

[0046] Low-temperature constant-temperature cold storage: The quick-frozen yam products are immediately transferred to a constant-temperature cold storage at -18℃±1℃ and stored in a sealed container, with the temperature fluctuation range controlled to not exceed ±1℃.

[0047] Example 3 Pre-treatment: Fresh Ruishu No. 1 yam harvested from the core production area of ​​Fanzhen, Ruichang City, Jiangxi Province, between the beginning of winter and the beginning of snow, is peeled immediately after manually removing the rhizome and fibrous roots using the integrated frame-type manual yam peeler of this invention. First, use the main blade installed at a 45° angle to cut a large, flat surface of the yam, automatically controlling the peeling thickness to about 1.5mm; Then, use the side arc-shaped secondary cutting edge to cut the yam by fitting it against the curved and uneven surface. Finally, use the 35° flat wedge-shaped cleaning head at the end to scrape away all residual skin flakes in pits and crevices of all sizes.

[0048] The entire peeling process for a single yam takes 14 seconds, with the operating environment temperature maintained at 12℃. After rinsing with running water, the yam is immediately sliced ​​into uniform pieces 1cm thick, with the entire processing time controlled within 1.5 hours after harvesting.

[0049] Test results showed that after peeling, the yam stem and flesh loss rate was 2.3%, the residual skin debris rate in pits and crevices was 0.3%, the skin jamming rate of the knife holder after 100 consecutive peels was 0%, and the knife cleaning time was ≤5s.

[0050] Simultaneous enzyme inactivation, color protection, and mucus removal: Before slicing, add oolong tea residue to food-grade drinking water at a material-to-liquid ratio of 1:50 (g / mL), boil for 20 minutes, and then filter to remove the tea residue, obtaining a tea boiling water extract; immediately place the yam slices into the continuously boiling tea water solution for a brief 5-second blanching treatment, simultaneously completing the inactivation of polyphenol oxidase, preventing browning and protecting the color, and removing the mucus from the surface of the yam; after blanching, quickly remove the slices and immediately place them in sterile cold water at 4℃ for 15 seconds to stop the enzymatic reaction, and then drain them with low-temperature cold air at 6℃ and a wind speed of 3m / s for 8 minutes to remove free surface moisture, obtaining pre-treated yam slices.

[0051] Pre-vacuum packaging: The pre-treated yam slices are laid flat in a single layer in a food-grade nylon extra-high pressure resistant 8-filament composite film packaging bag, with a single bag packaging amount of 1000g. Vacuum sealing is carried out under vacuum conditions of 0.1MPa, and the heat seal strength of the seal is 38N / 15mm, resulting in individually packaged yam slices.

[0052] Gradient liquid nitrogen quick-freezing: Individually packaged yam slices are laid flat on the rack of a programmable liquid nitrogen quick-freezing machine without stacking or compression, and a three-stage gradient liquid nitrogen quick-freezing program is executed: Pre-cooling stage: Pre-cool at a constant temperature of -60℃ for 30 minutes; First stage of quick freezing: quick freezing treatment at a constant temperature of -80℃ for 30 minutes; The second stage of quick freezing: transfer to a liquid nitrogen low-temperature environment at -120℃ and continue quick freezing until the surface temperature of the yam slices drops to -25℃ and the core temperature drops to -22℃. Stop quick freezing. The total quick freezing time is 90 minutes, and the quick-frozen yam product is obtained.

[0053] Low-temperature constant temperature cold storage: Immediately transfer the quick-frozen yam products to a constant temperature cold storage at -25℃±1℃ for sealed storage. During storage, avoid frequent opening and closing of the cold storage door and control the temperature fluctuation range to not exceed ±1℃.

[0054] Comparative Example 1: Conventional color-protecting scheme (without tea leaves, boiling water to inactivate enzymes, or mucus removal steps) The only difference from Example 1 is that the boiling water blanching treatment of tea leaves in step 2 is omitted, and a conventional food color protection process is used instead. The yam slices are soaked in a room temperature color protection solution of 0.5% citric acid + 0.3% ascorbic acid for 20 minutes. The remaining steps and parameters are completely consistent with Example 1.

[0055] Comparative Example 2: Conventional quick-freezing packaging sequence (quick-freezing first, then packaging) The only difference from Example 1 is that the pre-vacuum packaging in step 3 is omitted. The yam slices are first flash-frozen in liquid nitrogen, and then the flash-frozen yam slices are vacuum-packed. The remaining steps and parameters are completely consistent with Example 1.

[0056] Comparative Example 3: Conventional liquid nitrogen quick-freezing process (without three-stage gradient quick-freezing parameters) The only difference from Example 1 is that step 4 omits the three-stage gradient quick-freezing and instead uses direct quick-freezing at a conventional -40℃ environment for 2 hours until the core temperature of the yam drops to -18℃. The remaining steps and parameters are completely consistent with Example 1.

[0057] Comparative Example 4: Conventional manual peeling (without specialized peeling tools) The only difference from Example 1 is that step 1 uses conventional manual harvesting and manual peeling with a scraper. After harvesting, the product is transported to the workshop for further peeling. The entire processing time is 6 hours after harvesting. The remaining steps and parameters are completely consistent with Example 1.

[0058] Performance testing and effect verification The samples from Examples 1-3 and Comparative Examples 1-4 were stored in a constant temperature cold storage for 6 months and 12 months, respectively, and the core indicators were tested. The test results are shown in Table 1 below.

[0059] like Figure 1 The image shown is of freshly picked yam cut into sections; like Figure 2 The figure shown is a preferred embodiment of the present invention, illustrating quick-freezing and storage for 6 months. like Figure 3 The image shown is a graph depicting ordinary commodities stored in a cold storage facility for 12 months. like Figure 4 The figure shown is a diagram of the product after 12 months of quick-freezing storage in a preferred embodiment of the present invention.

[0060] Table 1 Effect verification conclusions The closed-type square frame blade holder brings unexpected technical benefits: it completely solves the industry pain point of traditional Y-type peelers getting stuck and clogging, allowing for 100 consecutive peels without any sticking, reducing blade cleaning time from 32 seconds to 4 seconds, while increasing the blade holder's resistance to deformation by more than 3 times and extending its service life by 2 times. Those skilled in the art have long used Y-type bifurcated structures and never thought of using a closed frame structure to solve the sticking problem, demonstrating its outstanding and substantial advantages.

[0061] The tilting blade achieves a perfect balance between efficiency and wear: the optimized tilt angle of 30°~45° reduces cutting resistance by 40%, making peeling easier; at the same time, it automatically controls the peeling thickness to 1~1.5mm, reducing stem and flesh loss by more than 50% compared to ordinary peeling knives (average peeling thickness 2.5mm). This angle parameter was obtained through extensive experimental optimization and is not a conventional choice in this field.

[0062] The integrated flat wedge-shaped safety cleaning head breaks through the prejudice of existing technology: existing technology generally believes that a sharp metal head must be used to clean pits, while the present invention uses a flat wedge-shaped head made of the same material as the handle, without sharp edges, making it absolutely safe to use, and can reach into tiny gaps of 0.5mm, reducing the pit residue rate to below 0.4%, which is 94% lower than ordinary sharp eye picks. At the same time, it has no dead corners for hygiene, is easy to clean and disinfect, and meets the requirements for food processing safety.

[0063] The instant boiling water blanching process of the present invention can simultaneously achieve the triple effects of enzyme inactivation, color protection, and removal of mucus. Compared with conventional chemical color protection solutions, the browning control effect is improved by more than 2 times, with no chemical reagent residues and higher food safety. The vacuum packaging followed by gradient liquid nitrogen quick-freezing process of this invention allows yam to quickly pass through the zone of maximum ice crystal formation, significantly reducing cell damage. Compared with conventional quick-freezing processes, the juice loss rate is significantly reduced, and the taste retention effect is significantly improved.

[0064] The above description is merely a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that are directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A method for quick-freezing and preserving Ruichang yam using liquid nitrogen, characterized in that, This includes the following steps performed sequentially: S1. Harvest fresh Ruichang yam from the period from the Beginning of Winter to the Minor Snow. After removing the root head and fibrous roots, use an integrated frame-type manual yam peeler. The peeler sequentially uses the inclined main blade to process large flat areas, the side secondary cutting blade to fit uneven curved surfaces, and the wedge-shaped cleaning head at the tail end to clean all pits and crevices, completing efficient peeling in all scenarios. After rinsing with clean water to remove residual skin and mucus, the yam slices are cut into pieces with a thickness of 0.5~2cm. S2. Immediately place the yam slices into boiling tea water for a quick scalding treatment of 5-30 seconds. This process simultaneously inactivates polyphenol oxidase, prevents browning and protects the color, and removes residual mucus from the surface of the yam. After scalding, quickly remove the slices and place them in sterile cold water at 0-4℃ to cool and stop the enzymatic reaction. Drain the free water from the surface to obtain pretreated yam slices. S3. Use food-grade nylon extra-high pressure resistant 8-filament composite film packaging bags to single-layer flat vacuum seal the pre-treated yam slices, with a vacuum degree of 0.08~0.1MPa, to obtain individually packaged yam slices; S4. Individually packaged yam slices are subjected to gradient quick-freezing in sequence. First, they are pre-cooled at -(50~70)℃ for 15~45 min, then quick-frozen at -(70~90)℃ for 15~45 min, and then transferred to a liquid nitrogen environment at -(100~120)℃ for continued quick-freezing until the surface temperature of the yam slices drops below -20℃ and the core temperature drops below -18℃, thus obtaining the quick-frozen yam product. S5. Store the quick-frozen yam products in a sealed cold storage at a constant temperature of -(18~25)℃, with the temperature fluctuation not exceeding ±1℃.

2. The method according to claim 1, characterized in that, In step S1, under manual operation of the integrated frame-type manual yam peeler, the peeling time for a single Ruichang yam in all scenarios is 12~25s, the yam stem and flesh loss rate after peeling is ≤2.5%, the residual rate of skin debris in pits and crevices is ≤0.4%, and there is no phenomenon of skin jamming or clogging in the blade holder.

3. The method according to claim 1, characterized in that, In step S1, the fresh Ruichang yam is the Ruishu No. 1 variety grown in the core production area of ​​Ruichang City, Jiangxi Province, with a single yam weighing 200-500g, and free from disease, mold, and mechanical damage.

4. The method according to claim 1, characterized in that, In step S2, the boiling tea water solution is obtained by adding drinking water at a material-to-liquid ratio of 1:(50~200) (g / mL) using green tea or oolong tea dregs as raw material, boiling for 10~20 minutes, and then filtering to remove the tea dregs. The surface free water is drained by low-temperature cold air draining, with a cold air temperature of 2~6℃, a wind speed of 1~3m / s, and a draining time of 5~10 minutes.

5. The method according to claim 1, characterized in that, In step S3, the vacuum degree of the vacuum-sealed packaging is controlled at 0.08~0.1MPa, the single bag packaging amount is 100~1000g, the heat seal strength of the packaging bag is ≥30N / 15mm, and it can withstand low temperature impact of -120℃ without cracking.

6. The method according to claim 1, characterized in that, In step S4, the total freezing time is controlled at 75~90 minutes, so that the yam slices can quickly pass through the maximum ice crystal formation zone of -1℃~-5℃ within 15 minutes. After quick-freezing, the core temperature of the yam slices is -19℃ to -22℃.

7. The method according to claim 1, characterized in that, In step S5, the refrigerated storage temperature of the quick-frozen yam product is -20~22℃, and the product shelf life is ≥12 months.

8. An integrated frame-type manual yam peeler for use in the method of claim 1, characterized in that, It includes an integrally formed tool body, which is composed of a tail end cleaning head (1), a cylindrical handle part (2) and a closed square frame tool holder part (3) connected in sequence; The closed square frame tool holder (3) forms a through-type skin outlet (4) in the middle. An inclined main blade (5) is fixedly installed on the inner side of the upper frame of the tool holder. An arc-shaped secondary cutting edge (6) is provided on the inner side of one side frame of the tool holder, and the other side frame is a smooth support edge. The tail end cleaning head (1) is a flat wedge-shaped structure integrally formed with the same material as the handle part (2), and all edges are rounded and have no sharp blades.

9. The integrated frame-type manual yam peeler according to claim 8, characterized in that, The inclined main blade (5) is fixedly installed on the inner side of the upper frame at an inclination angle of 30°~45°, with the cutting edge facing the skin outlet (4). The cutting edge of the main blade (5) extends 1.0~1.5mm beyond the inner side of the upper frame. The main blade (5) is made of food-grade stainless steel with a cutting edge thickness of 0.1~0.15mm and a cutting angle of 15°~20°.

10. The integrated frame-type manual yam peeler according to claim 8, characterized in that, The radius of curvature of the arc-shaped secondary cutting edge (6) is 25~40mm, and the height of the cutting edge extending beyond the inner side of the side frame is 0.8~1.2mm, used to cut the irregular curved surface of the yam; and / or The through-type skin outlet (4) has a length of 20-30 mm and a width of 10-15 mm. The inner wall of the skin outlet is smoothly chamfered with a chamfer radius of 0.5-1 mm; and / or The flat wedge-shaped cleaning head (1) has a tip angle of 30°~45° and an edge radius of ≥0.8mm, allowing it to reach into the crevices of yams with a depth of 0.5~3mm to remove dander; and / or The blade body is integrally injection molded from food-grade PP or ABS material, with a total length of 120~150mm and a weight of 15~30g.

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