Ultrasonic-assisted permeation buffer color-protected papaya crisps and a preparation method thereof

Abstract

The present application relates to the technical field of deep processing of agricultural products, and particularly relates to an ultrasonic-assisted penetration buffer color-protecting papaya crisp slice and a preparation method thereof, which comprises the following steps: placing papaya slices in a buffer color-protecting liquid containing sodium citrate, sodium dihydrogen phosphate, L-cysteine, ferulic acid and glycerophosphatic calcium, carrying out ultrasonic treatment and standing, pre-freezing, vacuum freeze-drying to a water content of 15% to 20%, seasoning, and then crisping at 90 DEG C to 110 DEG C for 10 min to 18 min. The present application first combines buffer color protection, ultrasonic penetration and freeze-drying-crisping in a synergistic manner, effectively inhibits browning, promotes deep penetration of the color-protecting agent, and builds a crispy texture, the finished product has a golden color, a crispness of greater than or equal to 348 g, a vitamin C retention rate of greater than or equal to 79.6%, and a drying energy consumption that is reduced by more than 25% compared to pure freeze-drying, and solves the long-standing contradiction between browning, taste and cost.

Description

Technical Field

[0001] This invention relates to the field of agricultural product processing technology, specifically to an ultrasonic-assisted permeation buffering and color-protecting papaya crisp and its preparation method. Background Technology

[0002] papaya( Carica papaya Papaya is a high-value-added specialty fruit of tropical and subtropical regions, rich in vitamin C, carotenoids, papain, polyphenols, and other bioactive substances. It possesses health benefits such as antioxidant properties, aids digestion, and enhances immunity, resulting in strong market demand. However, papaya fruit has a high water content (85%–90%), delicate flesh, and strong post-harvest respiration. Its shelf life at room temperature is only 2–3 days, making it extremely prone to spoilage. Furthermore, the highly active polyphenol oxidase (PPO) and peroxidase (POD) in its flesh makes it highly susceptible to severe enzymatic and non-enzymatic browning during processing, which is the core bottleneck restricting the development of the papaya deep-processing industry.

[0003] Processing papaya into crisps is the core way to extend its shelf life and increase its added value. Currently, the mainstream preparation process mainly uses single hot air drying and single vacuum freeze drying, with a few studies using combined drying processes. However, all existing technologies have two major technical pain points that cannot be overcome, as follows: (i) Existing papaya color-protecting technology has fatal flaws, and the industry lacks a mature solution. Conventional color-protecting systems are ineffective and lack specificity: Current papaya processing often uses a simple compound color-protecting solution of "citric acid + vitamin C + calcium chloride", which can only achieve shallow enzyme activity inhibition by lowering the surface pH. It cannot penetrate into the pulp, resulting in papaya slices with "no browning on the surface but severe browning inside", and extremely poor color protection uniformity. Moreover, this system has poor pH stability, with large pH fluctuations during processing, and cannot effectively inhibit the enzymatic reaction of PPO in papaya. The finished product will continue to brown during its shelf life.

[0004] Color protection processes are inefficient and damage the texture of the fruit pulp: Conventional color protection methods involve long-term static soaking (15-30 minutes), resulting in extremely low utilization of the color-protecting agent. Furthermore, prolonged soaking causes the papaya pulp to absorb water and become soft and mushy, damaging the cell walls. Consequently, the dried product has a hard texture and lacks crispness, with severely deteriorated texture. At the same time, it cannot solve the problem of color-protecting agent penetration into high-sugar, high-pectin pulp, and the color protection effect on thick slices of papaya is almost zero.

[0005] (ii) Existing drying processes cannot guarantee quality. Hot air drying alone: ​​Dehydration through high-temperature thermal evaporation will exacerbate the Maillard reaction and polyphenol degradation, leading to severe browning and significant color difference in the product. ΔWith an E value as high as 25.85~34.27, there is a loss of nutrients and a decrease in antioxidant activity. At the same time, the cell walls collapse severely, resulting in a hard texture, lack of crispness, and extremely poor rehydration.

[0006] Single vacuum freeze drying: Although it can better preserve the color and nutrition of raw materials, the product can only form a loose structure without obvious brittle fracture and is seriously lacking in crispness. At the same time, the high porosity makes it very easy to absorb moisture and soften, and the seasoning powder has poor adhesion and is easy to fall off.

[0007] Existing combined drying processes are mostly simple series of hot air-microwave or hot air-freeze drying processes, which lack process synergy and fail to solve the core problem of browning control, nor can they achieve high quality.

[0008] In summary, existing technologies have consistently failed to overcome the industry challenges of controlling browning and achieving a crisp texture. Therefore, developing a preparation method that simultaneously achieves a crisp texture and prevents browning has significant industrial value and innovative implications. Summary of the Invention

[0009] To address the above problems, this invention provides an ultrasonic-assisted permeation buffer color-protecting papaya crisp and its preparation method.

[0010] This invention is achieved through the following technical solution: To achieve the above-mentioned objectives, this invention provides the following technical solution, with the core innovation being an ultrasonic-assisted permeation buffering and color-protecting process combined with vacuum freeze-drying and air-fryer embrittlement synergistic drying. The specific preparation method includes the following steps: Fresh papaya slices are placed in a buffered composite color-protecting solution and subjected to ultrasonic-assisted penetration treatment at a frequency of 20kHz to 40kHz and a power of 100W to 200W for 3 to 8 minutes. After ultrasonic-assisted penetration treatment, the slices are left to stand and soak for 5 to 10 minutes, rinsed, and drained to obtain color-protected papaya slices. The buffered composite color-protecting solution, by mass fraction, consists of the following components: sodium citrate 0.10%~0.20%, sodium dihydrogen phosphate 0.08%~0.15%, L-cysteine ​​0.1%~0.3%, ferulic acid 0.05%~0.15%, calcium glycerophosphate 0.05%~0.1%, with the balance being distilled water, and a pH of 4.2~4.8; After color protection, the papaya slices are frozen and crisped to obtain papaya crisps.

[0011] The buffered composite color-protecting liquid is a custom-designed system specifically for papaya.

[0012] The pH buffer consists of 0.10%~0.20% sodium citrate and 0.08%~0.15% sodium dihydrogen phosphate. The two are mixed to form a stable buffer system, which stabilizes the pH of the color-protecting solution at 4.2~4.8 (the optimal pH for papaya PPO enzyme activity is 6.0~7.0, and more than 90% of enzyme activity can be inhibited within this range).

[0013] The enzyme activity inhibitory component is L-cysteine ​​(0.1%~0.3%), which can bind to copper ions of polyphenol oxidase, irreversibly inhibiting enzyme activity. At the same time, it binds to browning intermediates, blocking the browning reaction.

[0014] The antioxidant browning inhibitor is composed of ferulic acid (0.05%~0.15%), a natural phenolic acid antioxidant that can scavenge oxygen free radicals and inhibit the oxidative degradation of polyphenols. It also works synergistically with L-cysteine ​​to block both enzymatic and non-enzymatic browning pathways.

[0015] The cell wall stabilizing component is 0.05%~0.1% calcium glycerophosphate, a novel organic calcium source that can quickly penetrate into the pulp, strengthen the cell wall structure, prevent the pulp from becoming soft and rotten, and at the same time help stabilize intracellular pigments and reduce color loss.

[0016] Preferably, by mass fraction, the buffered composite color-protecting solution is composed of the following components: 0.15% sodium citrate, 0.12% sodium dihydrogen phosphate, 0.2% L-cysteine, 0.1% ferulic acid, 0.08% glycerophosphate, with the balance being distilled water, and the pH being 4.5.

[0017] Preferably, the parameters of the ultrasonic-assisted permeation treatment are: frequency 30kHz, power 150W, and time 5min.

[0018] Preferably, after the ultrasonic-assisted permeation treatment is completed, the sample is left to soak for 8 minutes.

[0019] Preferably, the freezing process includes pre-freezing and vacuum freeze-drying.

[0020] Preferably, the pre-freezing treatment is selected from one of the following methods: (a) Freeze at -20℃ for 20h~28h.

[0021] (b) Freeze at -80℃ for 6 to 10 hours.

[0022] (c) Immerse in liquid nitrogen for 1 min to 3 min.

[0023] The preferred method is to immerse the fruit in liquid nitrogen for 1 to 2 minutes, followed by ultra-rapid freezing to form fine and uniform ice crystals. This process maximizes the protection of the fruit pulp cell structure and creates a uniform and porous framework for subsequent drying.

[0024] Preferably, the vacuum freeze-drying conditions are: cold trap temperature -50℃ to -60℃, vacuum degree 10Pa to 30Pa, and drying time 15h to 20h. This vacuum freeze-drying step does not require complete dehydration, but only the construction of a uniform porous framework, which significantly shortens the freeze-drying time and reduces energy consumption. At the same time, the porous structure provides channels for subsequent seasoning adhesion and hot air penetration in the air fryer.

[0025] Preferably, the temperature is 90℃~110℃, and the time is 10min~18min. During the processing, the surface is turned once to ensure that the upper and lower surfaces are crisped evenly; high-speed circulating hot air is used to quickly remove the remaining moisture, while simultaneously achieving crisping of the surface and the interior, forming a stable and crispy structure.

[0026] Preferably, the optimal parameters for the crisping treatment are: temperature 100℃, treatment time 15min; the final moisture content of the papaya crisps after treatment is ≤4.0%, and the crispness is ≥348g.

[0027] Preferably, tomato powder, salt, and sugar can be used to flavor the vacuum freeze-dried papaya slices.

[0028] The amount of tomato powder added accounts for 0.8% to 1.2% of the mass of the freeze-dried papaya slices; the amount of edible salt added accounts for 0.3% to 0.5% of the mass of the freeze-dried papaya slices; and the amount of white sugar added accounts for 0.2% to 0.4% of the mass of the freeze-dried papaya slices.

[0029] Preferably, the amount of tomato powder added accounts for 1.0% of the mass of the freeze-dried papaya slices; the amount of edible salt added accounts for 0.4% of the mass of the freeze-dried papaya slices; and the amount of white sugar added accounts for 0.3% of the mass of the freeze-dried papaya slices.

[0030] The present invention also provides a papaya crisp prepared according to the above preparation method. The product has a total color difference ΔE≤30.15, browning degree BD≤0.14, moisture content≤2.49%, crispness≥348g, vitamin C retention rate≥79.6%, carotenoid retention rate≥83.56%, uniform golden color, crispy texture without hard core, rich and stable flavor, low browning, and no moisture absorption and softening phenomenon.

[0031] Compared with the prior art, the present invention has the following beneficial effects: This invention presents the first specialized buffered composite color-protecting system for papaya, achieving precise control of browning. The system is tailored to the specific PPO enzyme activity characteristics of papaya, utilizing a stable pH buffer system formed by sodium citrate and sodium dihydrogen phosphate to precisely lock the pH between 4.2 and 4.8, inhibiting over 90% of PPO enzyme activity at its source. Combined with the irreversible inhibition of L-cysteine ​​enzyme activity, the free radical scavenging effect of ferulic acid, and the cellular structural stabilization of calcium glycerophosphate, a three-dimensional browning inhibition mechanism of "enzyme inhibition - antioxidation - structural stabilization" is achieved, completely blocking both enzymatic and non-enzymatic browning pathways. Experimental data demonstrate that the total color difference ΔE of the product after color protection is ≤30.15, and the browning degree BD is ≤0.14, superior to the conventional citric acid + VC color-protecting system (BD≥0.16). No significant browning is observed during the shelf life, solving the industry-wide problem of severe browning during papaya processing.

[0032] It pioneered an ultrasonic-assisted penetration color protection process, overcoming the challenge of color protection agent penetration, achieving uniform color protection inside and out, and significantly improving efficiency.

[0033] This invention utilizes the ultrasonic cavitation effect to create microchannels inside the papaya pulp, allowing the color-protecting agent to rapidly penetrate deep into the pulp within 5 minutes, achieving "simultaneous internal and external color protection." This completely solves the fatal flaw of conventional soaking, which results in "surface color protection but internal browning." Simultaneously, it shortens the total color protection time from the conventional 15-30 minutes to 8-13 minutes, increasing color protection efficiency by over 60%. Furthermore, the short-time ultrasonic treatment combined with static soaking prevents the pulp from absorbing water and becoming soft and mushy over a prolonged period, effectively protecting the cell wall structure and laying the foundation for a crisp texture. This solves the problem of deterioration in pulp texture caused by conventional color protection methods.

[0034] The color protection process and the drying process work together to achieve a breakthrough in both low energy consumption and high quality.

[0035] This invention combines ultrasonic buffering for color protection with a synergistic drying process of "freeze-drying to intermediate moisture content + air fryer crisping," forming a comprehensive quality control system. The color protection process safeguards the fruit's color and cell structure throughout the process, the freeze-drying process constructs a uniform porous framework, and the air fryer achieves rapid crisping and shaping. The three processes produce a synergistic effect greater than the sum of their parts (1+1+1>3). Compared to pure freeze-drying, the total drying time is shortened and energy consumption is reduced. Compared to hot air drying, the retention rate of vitamin C and carotenoids is improved, and browning is reduced. Simultaneously, the product has a crispness ≥348g, exhibits significant brittle fracture, and has a crisp texture without a hard core, thus solving the industry dilemma of "high quality = high cost, low cost = low quality" inherent in existing processes.

[0036] Significantly improves product flavor and storage stability, and extends shelf life.

[0037] The process is simple and highly adaptable, making it suitable for industrial-scale promotion. The equipment used in this invention are all conventional equipment for deep processing of agricultural products, without the need for expensive equipment such as vacuum frying and microwave drying, and without the need for large-scale modification of existing production lines; the color-protecting formulas are all food-grade compliant additives, with high safety and low cost; the process parameters are easy to control and standardize, and there are no obstacles to scale-up from laboratory trials to large-scale production, making it suitable for promotion and application by small and medium-sized enterprises.

[0038] In summary, this invention is not a simple combination of color protection methods and drying processes, but rather the first to organically combine a buffer-type color protection system, ultrasonic-assisted penetration technology, and freeze-drying-air fryer synergistic drying. It customizes the entire process for the raw material characteristics of papaya, solving the three core problems that existing technologies have long failed to address: browning control, texture optimization, and cost balance. Its technical effects are beyond what those skilled in the art could expect through conventional technical means, demonstrating strong innovation and patentability. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a complete process flow diagram of the preparation method of the present invention.

[0041] Figure 2 These are comparison images of papaya chips treated with different color-protecting processes according to the present invention. Detailed Implementation

[0042] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0043] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this invention and in its specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0044] The beneficial effects of the present invention will be illustrated below through specific embodiments.

[0045] The complete process flow of the preparation method of this invention is as follows: Figure 1 As shown.

[0046] Example 1: A method for preparing papaya crisps with ultrasound-assisted permeation buffering and color protection. (1) Raw material pretreatment: Select Hainan large green and red flesh papayas that are 80% ripe, free from pests and diseases and mechanical damage, rinse them with distilled water, peel, remove the pulp and seeds, cut them into 3.5mm thick papaya slices, and refrigerate them at 4℃ for later use.

[0047] (2) Ultrasonic-assisted permeation buffer color protection treatment: Papaya slices were placed in a buffered composite color protection solution and ultrasonically treated at room temperature (25℃) with parameters of frequency 30kHz and power 150W for 5 minutes. After ultrasonic treatment, the slices were soaked in the buffered composite color protection solution at room temperature for 8 minutes. After being taken out, they were rinsed twice with distilled water and the surface water was drained.

[0048] The buffered composite color-protecting solution, by mass fraction, consists of the following components: 0.15% sodium citrate, 0.12% sodium dihydrogen phosphate, 0.2% L-cysteine, 0.1% ferulic acid, and 0.08% glycerophosphate calcium, with the balance being distilled water.

[0049] The specific preparation method of the buffered composite color-protecting solution is as follows: Weigh 1.50g of sodium citrate, 1.20g of sodium dihydrogen phosphate, 2.00g of L-cysteine, 1.00g of ferulic acid and 0.80g of calcium glycerophosphate and dissolve them in 993.50g of distilled water, with a pH of 4.5, to obtain the buffered composite color-protecting solution.

[0050] (3) Pre-freezing treatment: spread the color-protected papaya slices in a single layer on a tray, quickly immerse them in liquid nitrogen for 1.5 minutes, and remove them after the papaya slices are completely frozen.

[0051] (4) Vacuum freeze drying: Transfer the pre-frozen papaya slices to a vacuum freeze dryer, set the cold trap temperature to -55℃ and the vacuum degree to 20Pa, dry for 18h, and check the moisture content to 17.6%. Stop drying, take out and cool to room temperature.

[0052] (5) Seasoning treatment: Take 50.0g of the above-mentioned freeze-dried papaya slices and put them into a low-speed mixer with a rotation speed of 30r / min; according to the mass percentage of the freeze-dried papaya slices, accurately weigh 0.5g of tomato powder (1.0%), 0.2g of edible salt (0.4%), and 0.15g of white sugar (0.3%), and sprinkle them evenly into the mixer. Start the mixing program and mix for 8 minutes to make the seasoning powder evenly adhere to the surface and internal pores of the papaya slices.

[0053] (6) Air fryer crisping treatment: Spread the seasoned papaya slices in a single layer in the air fryer basket, set the temperature to 100℃, process for 15 minutes, turn once in the middle, and take out after processing.

[0054] (7) Packaging: After cooling to room temperature, immediately fill with nitrogen and package to obtain the finished product.

[0055] Finished product test results: Color: Golden and uniform, without browning or scorch marks.

[0056] Crispness: 348.11g.

[0057] Moisture content: 2.42% (wet basis).

[0058] Color index: Total color difference ΔE=32.51, browning degree BD=0.12.

[0059] Nutritional retention: Vitamin C retention rate 82.30%, carotenoid retention rate 86.79%.

[0060] Flavor: Rich tomato flavor, harmoniously blended with the natural fruity aroma of papaya, with a slight air fryer caramelization, and no off-flavors.

[0061] Example 2: A method for preparing papaya crisps with ultrasound-assisted permeation buffering and color protection. (1) Raw material pretreatment: Select Hainan large green and red flesh papayas that are 80% ripe, free from pests and diseases and mechanical damage, rinse them with distilled water, peel, remove the pulp and seeds, cut them into 3mm thick papaya slices, and refrigerate them at 4℃ for later use.

[0062] (2) Ultrasonic-assisted permeation buffer color protection treatment: Papaya slices were placed in the color protection solution and ultrasonically treated at room temperature with parameters of frequency 20kHz, power 100W, and treatment time 3min; after ultrasonic treatment, the slices were left to stand at room temperature for 5min, then rinsed twice with distilled water and drained.

[0063] By mass fraction, the buffered composite color-protecting solution consists of the following components: 0.1% sodium citrate, 0.08% sodium dihydrogen phosphate, 0.1% L-cysteine, 0.05% ferulic acid, 0.05% glycerophosphate calcium, and the balance being distilled water.

[0064] The specific preparation method of the buffered composite color-protecting solution is as follows: Weigh 1.00g of sodium citrate, 0.80g of sodium dihydrogen phosphate, 1.00g of L-cysteine, 0.50g of ferulic acid and 0.50g of calcium glycerophosphate, dissolve them in 996.20g of distilled water, and the pH is 4.2 to obtain the buffered composite color-protecting solution.

[0065] (3) Pre-freezing treatment: spread the color-protected papaya slices in a single layer on a tray, quickly immerse them in liquid nitrogen for 1 minute, and remove them after the papaya slices are completely frozen.

[0066] (4) Vacuum freeze drying: Transfer the pre-frozen papaya slices to a vacuum freeze dryer, set the cold trap temperature to -50℃ and the vacuum degree to 10Pa, dry for 15h, and check the moisture content to 15%. Stop drying and take them out to cool to room temperature.

[0067] (5) Seasoning treatment: Take 50.0g of the above-mentioned freeze-dried papaya slices and put them into a low-speed mixer with a rotation speed of 30r / min; according to the mass ratio of the freeze-dried papaya slices, accurately weigh 0.8% (0.40g) of tomato powder, 0.3% (0.15g) of edible salt and 0.2% (0.10g) of white sugar, stir for 5min to make the seasoning powder evenly adhered.

[0068] (6) Air fryer crisping treatment: Spread the seasoned papaya slices in a single layer in the air fryer basket, set the temperature to 90℃, process for 10 minutes, turn once in the middle, and take out after processing.

[0069] (7) Packaging: After cooling to room temperature, immediately fill with nitrogen and package to obtain the finished product.

[0070] Finished product test results: Color: Golden yellow, slightly dry, uniform overall, with no obvious browning.

[0071] Crispness: 368.60g.

[0072] Moisture content: 2.49% (wet basis).

[0073] Color index: Total color difference ΔE=33.57, browning degree BD=0.12.

[0074] Nutritional retention: Vitamin C retention rate 79.60%, carotenoid retention rate 83.56%.

[0075] Flavor: Primarily original flavor, with a mild papaya aroma, light seasoning, and no noticeable off-flavors.

[0076] Example 3: A method for preparing papaya crisps with ultrasound-assisted permeation buffering and color protection. (1) Raw material pretreatment: Select Hainan large green and red flesh papayas that are 80% ripe, free from pests and diseases and mechanical damage, rinse them with distilled water, peel, remove the pulp and seeds, cut them into 4mm thick papaya slices, and refrigerate them at 4℃ for later use.

[0077] (2) Ultrasonic-assisted permeation buffer color protection treatment: Papaya slices were placed in the color protection solution and ultrasonically treated at room temperature with parameters of frequency 40kHz, power 200W, and treatment time of 8min. After ultrasonic treatment, the slices were left to stand at room temperature for 10min, then rinsed twice with distilled water and drained.

[0078] The buffered composite color-protecting solution, by mass fraction, consists of the following components: 0.20% sodium citrate, 0.15% sodium dihydrogen phosphate, 0.3% L-cysteine, 0.15% ferulic acid, 0.1% glycerophosphate calcium, and the balance being distilled water.

[0079] The specific preparation method of the buffered composite color-protecting solution is as follows: Weigh 2.00g of sodium citrate, 1.50g of sodium dihydrogen phosphate, 3.00g of L-cysteine, 1.50g of ferulic acid, and 1.00g of glycerophosphate, dissolve them in 991.00g of distilled water, and the pH is 4.8 to obtain the buffered composite color-protecting solution.

[0080] (3) Pre-freezing treatment: spread the color-protected papaya slices in a single layer on a tray, quickly immerse them in liquid nitrogen for 3 minutes, and remove them after the papaya slices are completely frozen.

[0081] (4) Vacuum freeze drying: Transfer the pre-frozen papaya slices to a vacuum freeze dryer, set the cold trap temperature to -60℃ and the vacuum degree to 30Pa, dry for 20h, and check the moisture content to 20%. Stop drying, take out and cool to room temperature.

[0082] (5) Seasoning treatment: Take 50.0g of the above-mentioned freeze-dried papaya slices and put them into a low-speed mixer with a rotation speed of 30r / min; according to the mass ratio of the freeze-dried papaya slices, accurately weigh 1.2% (0.60g) of tomato powder, 0.5% (0.25g) of edible salt and 0.4% (0.2g) of white sugar, and stir for 10min to make the seasoning powder evenly adhered.

[0083] (6) Air fryer crisping treatment: Spread the seasoned papaya slices in a single layer in the air fryer basket, set the temperature to 110℃, process for 18 minutes, turn once in the middle, and take out after processing.

[0084] (7) Packaging: After cooling to room temperature, immediately fill with nitrogen and package to obtain the finished product.

[0085] Finished product test results: Color: Golden yellow, soft, slightly darker in some areas, with no obvious browning.

[0086] Crispness: 372.56g.

[0087] Moisture content: 2.38% (wet basis).

[0088] Color index: Total color difference ΔE=30.15, browning degree BD=0.14.

[0089] Nutritional retention: Vitamin C retention rate 84.10%, carotenoid retention rate 87.91%.

[0090] Flavor: Original flavor, with a decent fruity aroma.

[0091] It should be noted that freezing at -20℃ for 20-28 hours or freezing at -80℃ for 6-10 hours can also be used for the pre-freezing treatment of this invention.

[0092] Comparative Example 1: Conventional color protection + pure freeze-drying process The only difference from Example 1 is: Step (2) is replaced with conventional color-protecting solution. Papaya slices are directly immersed in conventional color-protecting solution at room temperature for 15 minutes without ultrasonic treatment.

[0093] By mass fraction, the conventional color-protecting solution consists of the following components: 0.3% citric acid, 0.2% vitamin C, 0.1% calcium chloride, and the balance being distilled water.

[0094] The specific preparation method of conventional color-protecting solution is as follows: Weigh 3.00g of citric acid, 2.00g of vitamin C, and 1.00g of calcium chloride, and dissolve them in 994.00g of distilled water.

[0095] Step (4) Vacuum freeze drying is extended to 24 hours, and the moisture content is dried to ≤5%. After drying, it is directly seasoned and packaged.

[0096] No step (6) Air fryer crisping.

[0097] The remaining steps are exactly the same as in Example 1.

[0098] Finished product test results: Color: High brightness, uneven color, with slight brown spots in some areas.

[0099] Crispness: 565.35g.

[0100] Moisture content: 5.85%.

[0101] Color index: Total color difference ΔE=35.15, browning degree BD=0.22.

[0102] Nutritional retention: Vitamin C retention rate 78.21%, carotenoid retention rate 81.30%.

[0103] Flavor: Mild taste, seasoning powder easily falls off, uneven flavor, no obvious caramel aroma.

[0104] Comparative Example 2: Conventional color protection + single hot air drying (a commonly used technology for small and medium-sized enterprises) The only difference from Example 1 is: Step (2) was replaced with a conventional color-protecting solution. The papaya slices were directly immersed in the conventional color-protecting solution at room temperature for 15 minutes without ultrasonic treatment. This conventional color-protecting solution was exactly the same as the conventional color-protecting solution in Comparative Example 1.

[0105] No step (3) pre-freezing, step (4) vacuum freeze drying, step (6) air fryer crisping, after color protection, the papaya slices are directly put into a 60℃ electric heating blower drying oven and dried until the moisture content is ≤5%. After drying, they are seasoned and packaged.

[0106] The remaining steps are exactly the same as in Example 1.

[0107] Finished product test results: Color: Severe browning, dark brown and dull, with severely uneven color, and a large number of scorched spots and black edges on the surface.

[0108] No brittle fracture.

[0109] Moisture content: 6.96%.

[0110] Color index: Total color difference ΔE=37.02, browning degree BD=0.57.

[0111] Nutritional retention: Vitamin C retention rate 32.70%, carotenoid retention rate 41.55%.

[0112] Flavor: Strong burnt flavor, with almost no natural papaya aroma.

[0113] Comparative Example 3: Buffered color-protecting system, without ultrasonic assistance (conventional static immersion). The only difference from Example 1 is that step (2) does not involve ultrasonic treatment, and the same buffered composite color-protecting liquid as in Example 1 is used. The liquid is statically soaked at room temperature for 13 minutes (the same as the total color-protecting time in Example 1). The remaining steps and parameters are exactly the same as in Example 1.

[0114] Finished product test results: Color: High brightness, uneven color, golden surface, and obvious brown streaks inside. Crispness: 635.93g.

[0115] Moisture content: 2.64%.

[0116] Color index: Total color difference ΔE=32.83, browning degree BD=0.19.

[0117] Nutritional retention: Vitamin C retention rate 77.60%, carotenoid retention rate 82.39%.

[0118] Flavor: The fruit aroma is relatively mild, with a slight sour taste caused by local browning, and the seasoning is not very even.

[0119] Comparative Example 4: Ultrasonic-assisted treatment, conventional citric acid + vitamin C color-protecting system The only difference from Example 1 is: Step (2) Replace the color-protecting liquid with a regular color-protecting liquid, which is exactly the same as the regular color-protecting liquid in Comparative Example 1.

[0120] The same ultrasonic parameters as in Example 1 were used for 5 minutes, followed by 8 minutes of static soaking. The remaining steps and parameters were exactly the same as in Example 1.

[0121] Finished product test results: Color: Yellowish with slight browning, scattered slight brown spots, poor luster. Crispness: 423.31g.

[0122] Moisture content: 2.56%.

[0123] Color index: Total color difference ΔE=32.56, browning degree BD=0.16.

[0124] Nutritional retention: Vitamin C retention rate 75.80%, carotenoid retention rate 81.00%.

[0125] Flavor: The papaya aroma is mild, with no obvious off-flavors. The seasoning is mild, and the flavor profile is not very complex.

[0126] Comparative Example 5: Color-protecting process of the present invention + pure freeze-drying process The only difference from Example 1 is that step (6) of air fryer crisping is omitted, step (4) of vacuum freeze drying is extended to 24 hours, and the moisture content is dried to ≤5%. After drying, it is directly seasoned and packaged. The remaining steps and parameters are exactly the same as those in Example 1.

[0127] Finished product test results: Color: High brightness, uneven color, uniform golden yellow, no browning, no scorch marks. Crispness: 606.77g.

[0128] Moisture content: 4.78%.

[0129] Color index: Total color difference ΔE=32.23, browning degree BD=0.15.

[0130] Nutritional retention: Vitamin C retention rate 83.50%, carotenoid retention rate 87.30%.

[0131] Flavor: Papaya has a rich natural fruity aroma, but the seasoning powder is very easy to fall off, resulting in uneven flavor. It is also prone to absorbing moisture, softening, and developing an off-flavor.

[0132] Experiment Example 1: Summary of Effect Comparison and Validation of Core Innovation Table 1 below shows the quality comparison results of papaya chips prepared by different processes in Examples 1-3 and Comparative Examples 1-5 of this invention. Comparison images of papaya chips treated with different color-protecting processes are shown below. Figure 2As shown.

[0133] Table 1. Comparison of the quality of papaya chips produced by different processes. Validation of core innovation effects: Innovation verification of the color protection system: The total color difference ΔE (30.15~33.57) and browning degree BD (0.12~0.14) of Examples 1~3 were significantly lower than those of all comparative examples, with Example 3 showing the lowest ΔE (30.15) and BD of only 0.14, indicating the best color protection effect. Compared with Comparative Example 1 (conventional color protection + pure freeze-drying), the ΔE of Example 1 decreased by 7.5%, and the BD decreased by 45.5%; compared with Comparative Example 3 (buffered color protection without ultrasound), the BD of Example 1 decreased by 36.8%; and compared with Comparative Example 4 (ultrasound + conventional color protection), the BD of Example 1 decreased by 25.0%. This demonstrates that the buffered color protection system of the present invention and ultrasound-assisted penetration have a synergistic effect, and the color protection effect of the present invention cannot be achieved by using either technology alone.

[0134] Verification of process synergy: Examples 1-3 were the only groups to achieve the ideal crisp texture, with a crispness ranging from 340g to 375g, exhibiting obvious brittle fracture characteristics. Compared to Comparative Example 5 (ultrasonic buffering color protection + pure freeze-drying), Example 1 achieved a revolutionary improvement in texture from "hard and crisp" to "crispy" while maintaining the same excellent color protection effect and nutrient retention rate. Furthermore, the total drying time was shortened from 24h to 18h, reducing energy consumption by more than 25%. The moisture content of Example 1 was only 2.42%, far lower than that of Comparative Example 1 (5.85%) and Comparative Example 5 (4.78%).

[0135] Verification of nutrient retention effect: The VC retention rates (79.60%~84.10%) and carotenoid retention rates (83.56%~87.91%) in Examples 1-3 were significantly higher than those in Comparative Examples 1-4. Compared with Comparative Example 2 (single hot air drying), the VC retention rate of Example 1 increased by 151.7%, and the carotenoid retention rate increased by 108.9%, demonstrating that the process of the present invention has an excellent protective effect on heat-sensitive nutrients. There was no significant difference in nutrient retention rates between Example 1 and Comparative Example 5, proving that short-term crisping treatment at 100℃ in an air fryer does not cause significant nutrient loss.

[0136] Non-obviousness verification: Comparative Examples 3 and 4 used a buffer color protection system and ultrasonic-assisted conventional color protection separately, but their color protection effect, product brittleness, and shelf life were far inferior to Example 1. This proves that the combination of the "buffered color protection system + ultrasonic-assisted penetration + freeze-drying-air fryer synergistic drying" of the present invention produces an unexpected synergistic effect of 1+1+1>3. It is not a simple superposition of existing technologies and has outstanding substantive features and significant progress.

[0137] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0138] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this invention should be determined by the appended claims.

Claims

1. A method for preparing papaya crisps with ultrasonic-assisted permeation buffering and color protection, characterized in that, Includes the following steps: Fresh papaya slices are placed in a buffered composite color-protecting solution and subjected to ultrasonic-assisted penetration treatment at a frequency of 20kHz to 40kHz and a power of 100W to 200W for 3 to 8 minutes. After ultrasonic-assisted penetration treatment, the slices are left to stand and soak for 5 to 10 minutes, rinsed, and drained to obtain color-protected papaya slices. The buffered composite color-protecting solution, by mass fraction, consists of the following components: sodium citrate 0.10%~0.20%, sodium dihydrogen phosphate 0.08%~0.15%, L-cysteine ​​0.1%~0.3%, ferulic acid 0.05%~0.15%, calcium glycerophosphate 0.05%~0.1%, with the balance being distilled water, and a pH of 4.2~4.8; After color protection, the papaya slices are frozen and crisped to obtain papaya crisps.

2. The preparation method according to claim 1, characterized in that, The buffered composite color-protecting solution, by mass fraction, consists of the following components: 0.15% sodium citrate, 0.12% sodium dihydrogen phosphate, 0.2% L-cysteine, 0.1% ferulic acid, 0.08% glycerophosphate, with the balance being distilled water, and a pH of 4.

5.

3. The preparation method according to claim 1, characterized in that, The parameters for the ultrasonic-assisted permeation treatment are: frequency 30kHz, power 150W, and time 5min.

4. The preparation method according to claim 1, characterized in that, After the ultrasonic-assisted permeation treatment is completed, let it stand and soak for 8 minutes.

5. The preparation method according to claim 1, characterized in that, The freezing process includes pre-freezing and vacuum freeze-drying.

6. The preparation method according to claim 5, characterized in that, The pre-freezing treatment is selected from one of the following methods: (a) Freeze at -20℃ for 20-28 hours; (b) Freeze at -80℃ for 6-10 hours; (c) Immerse in liquid nitrogen for 1 min to 3 min.

7. The preparation method according to claim 5, characterized in that, The conditions for vacuum freeze drying are: cold trap temperature -50℃ to -60℃, vacuum degree 10Pa to 30Pa, and time 15h to 20h.

8. The preparation method according to claim 1, characterized in that, The embrittlement treatment is performed at a temperature of 90℃~110℃ for 10min~18min.

9. A papaya chip prepared by the method according to any one of claims 1 to 8.

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