Kiwi fruit slice radio frequency vacuum drying energy consumption-quality cooperative regulation and control method based on maturity classification
By using radio frequency vacuum drying technology based on maturity grading and adjusting drying parameters, the problems of uneven heating and high energy consumption of kiwifruit at different maturity levels were solved, achieving a high-quality and low-energy drying effect.
Patent Information
- Application Number
- CN202511931817.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-19
- Publication Date
- 2026-01-23
AI Technical Summary
Existing radio frequency vacuum drying technology lacks optimized design for drying processes of kiwifruit at different stages of ripeness, resulting in uneven heating, localized overheating, loss of nutrients, unstable product quality, and high energy consumption.
Based on the maturity grade of kiwifruit, a differentiated drying strategy is adopted, including adjusting the drying temperature, vacuum degree and electrode spacing, combined with fiber optic temperature sensors and real-time monitoring to achieve precise control.
This technology enables rapid, low-temperature, and uniform dehydration of kiwi slices, significantly reducing the loss of nutrients and color quality, lowering drying energy consumption, and improving product quality and energy efficiency.
Smart Images
Figure CN121383583A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fruit and vegetable drying and processing technology, and in particular to a method for coordinated control of energy consumption and quality in radio frequency vacuum drying of kiwifruit slices based on maturity grading. Background Technology
[0002] Kiwifruit is rich in vitamins and dietary fiber, making it highly nutritious. However, fresh kiwifruit has a high water content (85-90%) and vigorous respiration metabolism, making it extremely susceptible to quality deterioration and spoilage during storage and transportation, severely impacting its commercial value. Processing kiwifruit into dried products can extend its shelf life and increase its added value. Radiofrequency vacuum drying technology, with its volumetric heating characteristics, can achieve rapid heat and mass transfer, reduce oxidation loss, and effectively maintain the integrity of the fruit pulp structure, making it a research hotspot in the field of fruit and vegetable drying in recent years. However, due to the coupling effect of electromagnetic field distribution and material dielectric properties, its drying quality is highly sensitive to changes in raw material properties. Samples at different maturity levels show significant differences in dielectric loss and drying behavior. Using uniform process parameters can easily lead to uneven heating, localized overheating, and loss of nutrients, resulting in unstable product quality. Currently, radiofrequency vacuum drying technology generally lacks optimized drying process designs for kiwifruit at different maturity levels. Summary of the Invention
[0003] Purpose of the invention: The purpose of this invention is to provide a method for coordinated control of energy consumption and quality in radio frequency vacuum drying of kiwifruit slices based on maturity grading; this method can solve the problem that current radio frequency vacuum drying technology generally lacks optimized design of drying process for kiwifruit at different maturity levels.
[0004] Technical Solution: To solve the above-mentioned technical problems, according to one aspect of the present invention, more specifically, a method for coordinated control of energy consumption and quality in radio frequency vacuum drying of kiwifruit slices based on maturity grading, comprising the following steps: S1. Fresh kiwifruit were classified into low maturity, medium maturity, and high maturity according to their soluble solids content (SSC). The kiwifruit were peeled and sliced to produce kiwifruit slices with a thickness of 8.00 ± 0.34 mm, a longitudinal diameter of 51.53 ± 2.41 mm, and a transverse diameter of 44.28 ± 2.15 mm. Among them, the SSC for low maturity was 7-10 °Brix, the SSC for medium maturity was 10-13 °Brix, and the SSC for high maturity was 13-16 °Brix. S2. Arrange 24 slices of kiwifruit in a longitudinal manner on a tray of an RF vacuum drying equipment, with a spacing of 65 mm between slices and a tray size of 400 mm × 270 mm × 20 mm; wherein the weight of the kiwifruit slices is 300-400g. S3. Place the tray at the center of the electrode plate of the radio frequency vacuum drying equipment, and insert fiber optic temperature sensors at the corners, edges and the center of the kiwi slices near the center of the tray. The probes are inserted to a depth of 23 mm and are parallel to the radial direction of the kiwi slices. The moisture content and temperature are monitored in real time through the built-in weighing module. S4. Select a drying strategy based on maturity: S4-1, Low-ripe kiwifruit: Drying temperature 65-68 °C, vacuum degree 0.020-0.023 MPa, electrode spacing 72-74 mm; S4-2, Medium-maturity kiwifruit: Drying temperature 58-60 °C, vacuum degree 0.023-0.025 MPa, electrode spacing 74-76 mm; S4-3, High-maturity kiwifruit: Drying temperature 55-58 °C, vacuum degree 0.025-0.028 MPa, electrode spacing 76-78 mm; S5. Stop drying when the moisture content of the kiwi slices is 14-15%. After the product has been refrigerated at room temperature, seal and store it.
[0005] Furthermore, in S1, the maturity grading is performed using a handheld refractometer to determine the soluble solids content, with a measurement accuracy of ± 0.2 °Brix.
[0006] Furthermore, the moisture content of the fresh kiwi slices in S1 is 84-85%.
[0007] Furthermore, the tray in S2 is made of polypropylene, and the side and bottom walls of the tray are provided with ventilation holes with a diameter of 10 mm.
[0008] Furthermore, the output power of the radio frequency vacuum drying device in S3 is 3 kW, and the frequency is 27.12 MHz.
[0009] Beneficial Effects: The radio frequency vacuum drying mode of this invention enhances heating efficiency and moisture migration rate through the synergistic effect of radio frequency volume heating and vacuum negative pressure environment, enabling rapid, low-temperature, and uniform dehydration of kiwifruit slices, significantly reducing the loss of nutrients and color quality. Furthermore, based on the differences in tissue structure and other aspects of kiwifruit at different maturity levels, a maturity-graded drying strategy is proposed, thereby achieving high-quality, low-energy drying results. Details are as follows: 1. Improving the quality of kiwifruit slices: Low-ripe kiwifruit has firm flesh, intact cell walls, a high proportion of bound water, and significant resistance to water migration, making it difficult to dehydrate quickly in the initial drying stage. Therefore, this invention uses a higher drying temperature, lower vacuum, and smaller electrode spacing at this stage to enhance water removal capacity, shorten the constant-rate period, and avoid cumulative quality damage from prolonged drying. Medium-ripe kiwifruit has moderate cell permeability and dielectric loss, requiring a balance between dehydration efficiency and the risk of heat damage. This invention uses a moderate temperature, moderate vacuum, and electrode spacing to improve heat distribution and maintain tissue structure. High-ripe kiwifruit has significantly softened flesh, an increased proportion of free water, and is prone to heating. Adjusting the equipment's process parameters—lowering the temperature, increasing the vacuum, and increasing the electrode spacing—slows down the dehydration rate and prevents surface overheating and thermal degradation of vitamin C.
[0010] 2. Reduced Drying Energy Consumption: Traditional radio frequency vacuum drying often uses fixed process parameters, failing to consider the differences in tissue structure of kiwifruit at different maturity levels, leading to energy mismatch. This invention achieves dynamic matching of radio frequency power, temperature, and vacuum degree through differentiated parameter control based on maturity level, allowing energy supply and dehydration demand to change synchronously, effectively reducing drying energy consumption. Attached Figure Description
[0011] Figure 1 This is a flowchart of a differentiated drying strategy for kiwi fruit slices using radio frequency vacuum drying. Figure 2 This is a schematic diagram showing the arrangement of kiwi slice samples on a tray. Detailed Implementation
[0012] To make the technical solution of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0013] Example 1 S1. Kiwifruit (7-10 °Brix) classified as low-ripe according to soluble solids content is peeled and then sliced into slices with a thickness of 8.0 ± 0.3 mm, a longitudinal diameter of 51.5 ± 2.4 mm, and a transverse diameter of 44.3 ± 2.1 mm. S2. Arrange 24 kiwi fruit samples (total mass 384.7 ± 1.6 g) longitudinally in a rectangular tray with a sample spacing of 65 mm and a tray size of 400 mm × 270 mm × 20 mm. S3. Place the tray at the center of the lower electrode plate of the radio frequency vacuum drying chamber, and insert three fiber optic temperature sensors into the kiwi slices in the corners, edges and near the center of the tray. The probe insertion depth is 23 mm. The temperature and moisture content are monitored in real time through the built-in weighing module of the device. S4. Dry the kiwi slices at a drying temperature of 60 °C, a vacuum degree of 0.024 MPa, and an electrode spacing of 75 mm until the final moisture content of the kiwi slices reaches 14-15%. Example 2 A method similar to Example 1, except that "S1" uses kiwifruit samples (10-13 °Brix) classified as medium-maturity based on soluble solids content.
[0014] Example 3 A method similar to Example 1, except that in "S1", samples of kiwifruit (13-16 °Brix) classified as high-maturity based on soluble solids content are used.
[0015] Example 4 A method similar to Example 1, except that in "S4", the drying temperature is increased to 68 °C, the vacuum degree is reduced to 0.021 MPa, and the electrode spacing is reduced to 74 mm.
[0016] Example 5 A method similar to Example 3, except that in "S4", the drying temperature is reduced to 56 °C, the vacuum degree is increased to 0.025 MPa, and the electrode spacing is increased to 77 mm.
[0017] Test case The ascorbic acid content, antioxidant capacity, color, and energy consumption of the kiwifruit slices prepared in Examples 1-5 and the comparative examples were determined.
[0018] Ascorbic acid content: 5.0 g of dried kiwifruit sample was placed in a mortar, and 50 g / L trichloroacetic acid solution was added. The mixture was ground into a paste under ice bath conditions, transferred to a 50 mL volumetric flask, and diluted to the mark. After extraction for 10 min, the sample was centrifuged, and the supernatant was used as the extract. 1.0 mL of the extract was placed in a test tube, and 1.0 mL of 50 g / L trichloroacetic acid solution was added, followed by 1.0 mL of anhydrous ethanol. The mixture was shaken well, and then 0.5 mL of 0.4% phosphoric acid-ethanol solution, 1.0 mL of 5 g / L phenanthroline-ethanol solution, and 0.5 mL of 0.3 g / L ferric chloride-ethanol solution were added. The absorbance of the reaction system at 534 nm was recorded. The ascorbic acid content is expressed in mg / 100g.
[0019] Antioxidant capacity: 1.0 g of dried kiwi fruit sample was dissolved in 50 mL of 70% ethanol solution. The extraction conditions were set as follows: ethanol concentration 70%, solid-liquid ratio 1:50 (w / v), ultrasonic power 420 W, and extraction temperature 50°C. oC. Ultrasonic extraction for 90 min. After extraction, centrifuge at 8000 r / min for 15 min, and collect the supernatant as the extract. Mix 1 mL of the extract with 2 mL of DPPH solution, and incubate in the dark for 30 min. Using distilled water as a blank, measure the absorbance at 517 nm. The antioxidant capacity is expressed as a percentage.
[0020] Color measurement: Direct measurement was performed using a colorimeter. The overall color parameters of the dried kiwifruit were measured using a 30mm aperture. Color gradation was based on the L-axis of the CIELab color space. * a * and b * Value description. L * Indicates brightness (0 = black to 100 = white), a * Represents the red-green spectrum (negative values = green, positive values = red); b * This represents the yellow-blue spectrum (negative values = blue, positive values = yellow).
[0021] Energy consumption measurement: The radio frequency vacuum equipment is equipped with an energy meter, and the vacuum pump is equipped with a power meter. The total energy consumption (kWh) of the drying process is measured by the energy meter and the power meter.
[0022] The results are shown in Tables 1-3.
[0023] Table 1. Comparison of ascorbic acid content and antioxidant capacity index Example 1 Example 2 Example 3 Example 4 Example 5 Ascorbic acid content, mg / 100g 114.66 127.51 115.76 110.29 119.89 Antioxidant capacity, % 93.10 96.42 93.76 91.55 94.18 Table 2 Color Comparison Results index Example 1 Example 2 Example 3 Example 4 Example 5 <![CDATA[L * ]]> 75.77 73.07 66.95 74.89 71.85 <![CDATA[a * ]]> -1.02 -1.65 -1.09 -0.96 -1.26 <![CDATA[b * ]]> 24.74 23.48 27.90 23.64 26.59 Table 3 Energy Consumption Comparison Results index Example 1 Example 2 Example 3 Example 4 Example 5 Energy consumption, kWh 23.44 21.69 25.80 20.61 25.98 Time consumed, h 7.67 6.83 7.83 6.50 8.00 As shown in Tables 1-3, for low-ripe kiwifruit, compared to the fixed process (Example 1), the optimized process (Example 4) with higher temperature, lower vacuum, and lower electrode spacing reduced energy consumption and drying time by 12.1% and 15.3%, respectively. There was no significant difference in ascorbic acid content and antioxidant capacity, the color remained good, and key quality indicators did not deteriorate significantly. This indicates that the optimization strategy effectively balanced dehydration efficiency and quality maintenance for low-ripe raw materials. For high-ripe kiwifruit, compared to the fixed process (Example 3), the optimized process (Example 5) with lower temperature, higher vacuum, and higher electrode spacing slightly increased energy consumption and drying time, but the kiwifruit brightness value improved, and the color and nutritional quality remained good. Under the same drying process conditions (Examples 1-3), the ascorbic acid content of medium maturity (Example 2) increased by 10.2-11.2%, while energy consumption and drying time decreased by 7.5-15.9% and 11-17%, respectively, demonstrating that differentiated regulation is crucial for maintaining the sensory and nutritional quality of products at different maturity levels.
[0024] In summary, the energy consumption and quality synergistic control method for radio frequency vacuum drying of kiwifruit slices based on maturity grading of the present invention can achieve precise processing for different raw material characteristics, and provides an effective solution for systematically solving the problems of unstable quality and high energy consumption of dried kiwifruit products.
[0025] 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 present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.
Claims
1. A method for coordinated control of energy consumption and quality in radio frequency vacuum drying of kiwifruit slices based on maturity grading, characterized in that, Includes the following steps: S1. Fresh kiwifruit were classified into low maturity, medium maturity, and high maturity according to their soluble solids content (SSC). The kiwifruit were peeled and sliced to produce kiwifruit slices with a thickness of 8.00 ± 0.34 mm, a longitudinal diameter of 51.53 ± 2.41 mm, and a transverse diameter of 44.28 ± 2.15 mm. Among them, the SSC for low maturity was 7-10 °Brix, the SSC for medium maturity was 10-13 °Brix, and the SSC for high maturity was 13-16 °Brix. S2. Arrange 24 slices of kiwifruit in a longitudinal manner on a tray of an RF vacuum drying equipment, with a spacing of 65 mm between slices and a tray size of 400 mm × 270 mm × 20 mm; wherein the weight of the kiwifruit slices is 300-400g. S3. Place the tray at the center of the electrode plate of the radio frequency vacuum drying equipment, and insert fiber optic temperature sensors at the corners, edges and the center of the kiwi slices near the center of the tray. The probes are inserted to a depth of 23 mm and are parallel to the radial direction of the kiwi slices. The moisture content and temperature are monitored in real time through the built-in weighing module. S4. Select a drying strategy based on maturity: S4-1, Low-ripe kiwifruit: Drying temperature 65-68 °C, vacuum degree 0.020-0.023 MPa, electrode spacing 72-74 mm; S4-2, Medium-maturity kiwifruit: Drying temperature 58-60 °C, vacuum degree 0.023-0.025 MPa, electrode spacing 74-76 mm; S4-3, High-maturity kiwifruit: Drying temperature 55-58 °C, vacuum degree 0.025-0.028 MPa, electrode spacing 76-78 mm; S5. Stop drying when the moisture content of the kiwi slices is 14-15%. After the product has been refrigerated at room temperature, seal and store it.
2. The method for coordinated control of energy consumption and quality in radio frequency vacuum drying of kiwifruit slices based on maturity grading according to claim 1, characterized in that: The maturity grading in S1 was performed using a handheld refractometer to determine the soluble solids content, with a measurement accuracy of ± 0.2 °Brix.
3. The method for coordinated control of energy consumption and quality in radio frequency vacuum drying of kiwifruit slices based on maturity grading according to claim 1, characterized in that: The moisture content of the fresh kiwi slices in S1 is 84-85%.
4. The method for coordinated control of energy consumption and quality in radio frequency vacuum drying of kiwifruit slices based on maturity grading according to claim 1, characterized in that: The tray in S2 is made of polypropylene, and the side and bottom walls of the tray are provided with ventilation holes with a diameter of 10mm.
5. The method for coordinated control of energy consumption and quality in radio frequency vacuum drying of kiwifruit slices based on maturity grading according to claim 1, characterized in that: The output power of the radio frequency vacuum drying equipment in S3 is 3 kW, and the frequency is 27.12 MHz.