Processing method of dried kiwi fruit product

Abstract

The invention belongs to the technical field of food processing, and discloses a processing method of a dried kiwi fruit product. According to the invention, cold plasma pretreatment, composite enzymatic hydrolysis and segmented microwave vacuum drying processes are cooperated, so that the obtained dried kiwi fruit product is less in nutrient loss, high in vitamin C retention rate and long in preservation time, and has good sensory quality. Firstly, plasmas are generated under the action of a high-frequency electric field, isoactive particles in the plasmas can penetrate through microbial cell membranes to destroy DNA structures of the microbial cell membranes, efficient sterilization is achieved, and the shelf life is prolonged; meanwhile, micro holes are formed in the surfaces of the kiwi fruit slices through the plasma etching effect, the cell permeability is improved, more acting sites are provided for subsequent enzymolysis, and the enzymolysis efficiency is improved. The surface microstructure of the fruit slice is changed, and the compound enzyme permeates into intercellular substances, so that the cell structure is loosened, and drying is facilitated. The two-stage microwave vacuum drying is matched with the micro-hole structure formed by the cold plasma, so that the drying time can be shortened, and the degradation of nutritional ingredients is avoided.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, and more specifically relates to a processing method for dried kiwifruit products. Background Technology

[0002] Kiwifruit is a special berry belonging to the Actinidiaceae family and the Actinidis genus. It is rich in minerals such as calcium, phosphorus, and iron, as well as functional components beneficial to the human body, including flavonoids, dietary fiber, polysaccharides, vitamins, and polyphenols, playing an important role in maintaining human health. Kiwifruit is juicy and has high nutritional, medicinal, health-promoting, and cosmetic value, earning it the title of "King of Fruits." However, under normal temperature conditions, kiwifruit is prone to softening and rotting after harvesting; therefore, researching post-harvest storage techniques is particularly important.

[0003] In the processing of dried kiwifruit, microbial contamination, nutrient loss, and hardening are key issues restricting product quality. Drying is an effective method to extend the shelf life of fruit, and current kiwifruit drying processes mostly employ hot air drying or vacuum freeze-drying. However, hot air drying is time-consuming and involves high temperatures, easily leading to significant losses of nutrients such as vitamin C, severe browning, hardening, and poor rehydration. Vacuum freeze-drying is inefficient and has a long production cycle. Microwave drying is difficult to control; overheating can damage product quality, causing scorching, gelatinization, and surface hardening. Therefore, existing drying technologies struggle to balance efficiency and quality. Furthermore, traditional kiwifruit drying methods often rely on high-temperature sterilization, which can easily destroy nutrients.

[0004] Therefore, how to provide a processing method for dried kiwifruit products is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the present invention provides a processing method for dried kiwifruit products.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for processing dried kiwifruit products includes the following steps:

[0008] (1) Select fresh kiwifruit, wash, peel and cut into slices;

[0009] (2) Place the fruit slices in a cold plasma treatment device, fill it with working gas, and perform cold plasma treatment;

[0010] (3) Add the fruit slices treated with cold plasma to the compound enzyme solution, adjust the pH value, carry out enzymatic hydrolysis, and inactivate the enzyme by water bath after the enzymatic hydrolysis is completed.

[0011] (4) Drain the enzymatically hydrolyzed fruit slices, perform two-stage microwave vacuum drying, then cool to room temperature, package, and obtain dried kiwi fruit products.

[0012] Preferably, the thickness of the fruit slices in step (1) is 4-6 mm.

[0013] Preferably, the working gas in step (2) is air.

[0014] Preferably, the process parameters for the cold plasma treatment in step (2) include: power 150-300W, frequency 10-20kHz, and treatment time 1-3min.

[0015] The beneficial effects of the above technical solution are as follows: the sterilization effect of cold plasma reduces the initial bacterial count, reduces the risk of microbial proliferation during subsequent processing, and extends the shelf life. The process parameters can ensure the sterilization effect while avoiding damage to the fruit slices due to over-processing.

[0016] Preferably, the complex enzyme solution in step (3) comprises, by mass fraction: 0.15% pectinase, 0.1% cellulase, and 0.05% hemicellulase.

[0017] The beneficial effects of the above technical solution are as follows: In the compound enzyme solution, pectinase can decompose pectin substances and destroy intercellular connections; cellulase and hemicellulase work synergistically on cell wall cellulose and hemicellulose, making the cell structure loose.

[0018] Preferably, the pH value is adjusted to 4-5 in step (3).

[0019] Preferably, the enzymatic hydrolysis in step (3) is carried out at 35-38°C for 30-40 minutes.

[0020] Preferably, the temperature for inactivating the enzyme in the water bath in step (3) is 85°C and the time is 5 min.

[0021] The beneficial effects of the above technical solution are as follows: 35-38℃ is the optimal operating temperature for the compound enzyme, providing a mild operating condition. The pH value is closer to simulating the acidic environment of kiwifruit, further activating enzyme activity and enabling efficient decomposition of cell wall components. This improves the looseness of the fruit slices, creating favorable conditions for moisture migration during subsequent drying. Enzymatic hydrolysis at 85℃ terminates the reaction, preventing excessive softening and rotting of the fruit slices. Enzymatic hydrolysis improves the permeability of the fruit, accelerating subsequent drying and making it easier to retain nutrients within the cells.

[0022] Preferably, the specific operation of the two-stage microwave vacuum drying in step (4) includes:

[0023] First stage: Vacuum degree 0.08MPa, microwave power 300-400W, dry to moisture content 15-25%;

[0024] Second stage: Vacuum degree 0.09MPa, microwave power 150-200W, dry until moisture content ≤5%.

[0025] The beneficial effects of the above technical solution are as follows: the first stage uses high power to rapidly evaporate surface moisture, and the second stage uses low power to slowly remove internal moisture. Combined with the microporous structure formed by cold plasma, the drying effect is improved while the drying time is significantly reduced.

[0026] As can be seen from the above technical solution, compared with the prior art, the present invention provides a processing method for dried kiwifruit products, which has the following beneficial effects:

[0027] (1) This invention combines cold plasma pretreatment, compound enzymatic hydrolysis, and segmented microwave vacuum drying processes to produce dried kiwifruit with minimal nutrient loss, high vitamin C retention, long shelf life, and excellent sensory quality. First, plasma is generated under a high-frequency electric field. The highly active particles in plasma can penetrate microbial cell membranes, destroying their DNA structure and achieving efficient sterilization, thus extending shelf life. Simultaneously, plasma etching creates micropores on the surface of the kiwifruit slices, increasing cell permeability and providing more sites for subsequent enzymatic hydrolysis, thereby improving hydrolysis efficiency. The altered microstructure on the fruit slice surface allows the compound enzyme to penetrate the intercellular matrix, loosening the cell structure and facilitating drying. The two-stage microwave vacuum drying combined with the microporous structure formed by cold plasma reduces drying time and prevents nutrient degradation due to prolonged heating.

[0028] (2) This invention significantly reduces preparation time, improves production efficiency, and is suitable for large-scale factory applications. The method is mild, has little impact on nutritional components, and avoids the addition of large amounts of additives, making it more beneficial to health. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0030] Example 1

[0031] A method for processing dried kiwifruit products includes the following steps:

[0032] (1) Select fresh kiwifruit, wash, peel and cut into slices;

[0033] (2) Place the fruit slices in a cold plasma treatment device, fill it with working gas, and perform cold plasma treatment;

[0034] (3) Add the fruit slices treated with cold plasma to the compound enzyme solution, adjust the pH value, carry out enzymatic hydrolysis, and inactivate the enzyme by water bath after the enzymatic hydrolysis is completed.

[0035] (4) Drain the enzymatically hydrolyzed fruit slices, perform two-stage microwave vacuum drying, then cool to room temperature, package, and obtain dried kiwi fruit products.

[0036] The thickness of the fruit slices mentioned in step (1) is 4 mm;

[0037] The working gas mentioned in step (2) is air;

[0038] The process parameters for the cold plasma treatment in step (2) include: power 150W, frequency 10kHz, and treatment time 1min;

[0039] The complex enzyme solution mentioned in step (3) comprises, by mass fraction: 0.15% pectinase, 0.1% cellulase, and 0.05% hemicellulase;

[0040] The pH value is adjusted to 4 as described in step (3);

[0041] The enzymatic hydrolysis in step (3) is carried out at 35°C for 30 minutes.

[0042] The temperature for enzyme inactivation in step (3) is 85℃ and the time is 5 minutes.

[0043] The specific operations of the two-stage microwave vacuum drying described in step (4) include:

[0044] First stage: Vacuum degree 0.08MPa, microwave power 300W, dry to moisture content 20%;

[0045] Second stage: Vacuum degree 0.09MPa, microwave power 150W, dry to moisture content 5%.

[0046] Example 2

[0047] A method for processing dried kiwifruit products includes the following steps:

[0048] (1) Select fresh kiwifruit, wash, peel and cut into slices;

[0049] (2) Place the fruit slices in a cold plasma treatment device, fill it with working gas, and perform cold plasma treatment;

[0050] (3) Add the fruit slices treated with cold plasma to the compound enzyme solution, adjust the pH value, carry out enzymatic hydrolysis, and inactivate the enzyme by water bath after the enzymatic hydrolysis is completed.

[0051] (4) Drain the enzymatically hydrolyzed fruit slices, perform two-stage microwave vacuum drying, then cool to room temperature, package, and obtain dried kiwi fruit products.

[0052] The thickness of the fruit slices mentioned in step (1) is 6 mm;

[0053] The working gas mentioned in step (2) is air;

[0054] The process parameters for the cold plasma treatment in step (2) include: power 300W, frequency 20kHz, and treatment time 3min;

[0055] The complex enzyme solution mentioned in step (3) comprises, by mass fraction: 0.15% pectinase, 0.1% cellulase, and 0.05% hemicellulase;

[0056] The pH value is adjusted to 5 as described in step (3);

[0057] The enzymatic hydrolysis in step (3) is carried out at 38°C for 40 minutes.

[0058] The temperature for enzyme inactivation in step (3) is 85℃ and the time is 5 minutes.

[0059] The specific operations of the two-stage microwave vacuum drying described in step (4) include:

[0060] First stage: Vacuum degree 0.08MPa, microwave power 400W, dry to moisture content 20%;

[0061] Second stage: Vacuum degree 0.09MPa, microwave power 200W, dry to moisture content 5%.

[0062] Example 3

[0063] A method for processing dried kiwifruit products, characterized by comprising the following steps:

[0064] (1) Select fresh kiwifruit, wash, peel and cut into slices;

[0065] (2) Place the fruit slices in a cold plasma treatment device, fill it with working gas, and perform cold plasma treatment;

[0066] (3) Add the fruit slices treated with cold plasma to the compound enzyme solution, adjust the pH value, carry out enzymatic hydrolysis, and inactivate the enzyme by water bath after the enzymatic hydrolysis is completed.

[0067] (4) Drain the enzymatically hydrolyzed fruit slices, perform two-stage microwave vacuum drying, then cool to room temperature, package, and obtain dried kiwi fruit products.

[0068] The thickness of the fruit slices mentioned in step (1) is 5 mm;

[0069] The working gas mentioned in step (2) is air;

[0070] The process parameters for the cold plasma treatment in step (2) include: power 200W, frequency 15kHz, and treatment time 2min;

[0071] The complex enzyme solution mentioned in step (3) comprises, by mass fraction: 0.15% pectinase, 0.1% cellulase, and 0.05% hemicellulase;

[0072] The pH value is adjusted to 5 as described in step (3);

[0073] The enzymatic hydrolysis in step (3) is carried out at 37°C for 35 minutes.

[0074] The temperature for enzyme inactivation in step (3) is 85℃ and the time is 5 minutes.

[0075] The specific operations of the two-stage microwave vacuum drying described in step (4) include:

[0076] First stage: Vacuum degree 0.08MPa, microwave power 350W, drying to a moisture content of 20%;

[0077] Second stage: Vacuum degree 0.09MPa, microwave power 180W, dry to moisture content 5%.

[0078] Comparative Example 1

[0079] The difference from Example 3 is that step (2) is omitted and cold plasma treatment is not performed; the rest are the same.

[0080] Comparative Example 2

[0081] The difference from Example 3 is that step (3) is omitted and enzymatic hydrolysis is not performed; the rest are the same.

[0082] Comparative Example 3

[0083] Kiwi fruit slices are directly dried with hot air at 70℃ until the moisture content is 5%.

[0084] The dried fruits obtained from each embodiment and comparative example were tested, and the results are shown in Table 1. The sensory evaluation score was out of 10 points, including: color (3 points), taste (4 points), and flavor (3 points). The scores were given by a blind review panel of 10 people, and the average score was taken. As shown in Table 1, the method of this invention can achieve efficient sterilization, extend shelf life, retain nutrients, and also possess good sensory quality.

[0085] Table 1

[0086] Group Total bacterial count (CFU / g) Vitamin C retention rate (%) Sensory rating Example 1 88 91.5 9.0 Example 2 83 91.3 9.2 Example 3 72 92.7 9.3 Comparative Example 1 1200 82.1 7.5 Comparative Example 2 400 68.4 7.8 Comparative Example 3 2500 42.5 6.3

[0087] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The solutions disclosed in the embodiments are described simply because they correspond to the methods disclosed in the embodiments; relevant parts can be found in the method section.

[0088] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A processing method for dried kiwifruit products, characterized in that, Includes the following steps: (1) Select fresh kiwifruit, wash, peel and cut into slices; (2) Place the fruit slices in a cold plasma treatment device, fill it with working gas, and perform cold plasma treatment; (3) Add the fruit slices treated with cold plasma to the compound enzyme solution, adjust the pH value, carry out enzymatic hydrolysis, and inactivate the enzyme by water bath after the enzymatic hydrolysis is completed. (4) Drain the enzymatically hydrolyzed fruit slices, perform two-stage microwave vacuum drying, then cool to room temperature, package, and obtain dried kiwi fruit products.

2. The processing method for dried kiwifruit products according to claim 1, characterized in that, The thickness of the fruit slices mentioned in step (1) is 4-6 mm.

3. The processing method for dried kiwifruit products according to claim 1, characterized in that, The working gas mentioned in step (2) is air.

4. The processing method for dried kiwifruit products according to claim 1, characterized in that, The process parameters for the cold plasma treatment in step (2) include: power 150-300W, frequency 10-20kHz, and treatment time 1-3min.

5. The processing method for dried kiwifruit products according to claim 1, characterized in that, The complex enzyme solution in step (3) comprises, by mass fraction: 0.15% pectinase, 0.1% cellulase, and 0.05% hemicellulase.

6. The processing method for dried kiwifruit products according to claim 1, characterized in that, The pH value is adjusted to 4-5 as described in step (3).

7. The processing method for dried kiwifruit products according to claim 1, characterized in that, The enzymatic hydrolysis in step (3) is carried out at 35-38°C for 30-40 minutes.

8. The processing method for dried kiwifruit products according to claim 1, characterized in that, The temperature for inactivating the enzyme in the water bath in step (3) is 85°C and the time is 5 min.

9. A processing method for dried kiwifruit products according to claim 1, characterized in that, The specific operations of the two-stage microwave vacuum drying described in step (4) include: First stage: Vacuum degree 0.08MPa, microwave power 300-400W, dry to moisture content 15-25%; Second stage: Vacuum degree 0.09MPa, microwave power 150-200W, dry until moisture content ≤5%.