A low-temperature composite dehydration method for citrus sliced ​​fruits for tea drinking

Abstract

The present invention provides a low-temperature composite dehydration method for citrus sliced ​​fruit for tea drinking, which belongs to the technical field of agricultural product processing. The present invention adopts coating coordinated with ultrasonic vacuum penetration combined with refractive window drying, adopts xanthan gum-zein as a membrane material for coating, then performs ultrasonic vacuum penetration, and finally performs refractive window drying on the osmotic dehydrated citrus fruit slices to obtain a product for tea drinking. Coating, ultrasound, and vacuum can all promote mass transfer during the penetration process, wherein the coating can not only promote dehydration, but also reduce the infiltration of sugar in the permeate, and the coordinated treatment of the three can further accelerate dehydration, and can reduce the infiltration of sugar while accelerating dehydration. The preliminary penetration treatment can reduce the time of subsequent refractive window drying, reduce the loss of quality, and finally obtain citrus sliced ​​fruit for tea drinking. The product can also be eaten as candied fruit after making tea and drinking.

Description

Technical Field

[0001] The invention relates to a low-temperature composite dehydration method for citrus sliced ​​fruits for tea drinking, belonging to the technical field of agricultural product processing. Background Art

[0002] Citrus fruits mainly refer to lemons, grapefruits, mandarins, sweet oranges and bitter oranges. The latter two types of oranges can be added to the human diet as functional ingredients, as an ample supply of many major bioactive compounds, namely alkaloids, polyphenols, carotenoids and limonoids, are widely used in agriculture, food and nutraceutical industries due to their recognized sensory and many health attributes. Despite the perception of fruits and vegetables as green, healthy and nutritious, the consumption of fruits and vegetables by most people in the world still does not meet the World Health Organization's recommendations for a healthy diet. Adding fruits and vegetables to tea can boost daily intake and is an excellent way to deliver nutrients and bioactive compounds to the human body.

[0003] In the current environment, food waste will directly cause resource loss and thus hinder economic development. According to a survey by the Food and Agriculture Organization of the United Nations (FAO), about one-third of the food produced in the world is wasted, including picking on the farm, post-harvest handling, processing, distribution and final user consumption. Each step will have varying degrees of waste, so food protection is imminent. The rise and development of the fruit processing industry is of great significance to avoiding fruit waste and extending the shelf life of fruit. Dried citrus fruits are the most common citrus processed products, with large market demand and simple processing technology. The sugaring and dehydration in the processing process and the subsequent drying steps are key processing steps, which will affect the final product characteristics.

[0004] Osmotic dehydration is widely used as a simple low-temperature process (under mild heat treatment (<50 °C)) before drying to improve the sensory and physicochemical quality of the final product. It involves soaking the food material in a hypertonic solution for several hours (usually sugar solution for fruits and vegetables and salt solution for meats), during which the osmotic pressure difference between the material and its surrounding hypertonic solution drives mass transfer. During osmotic dehydration, mass transfer occurs in the plant cell structure as an imperfect semipermeable membrane: the osmotic agent flows into the product, while water and water-soluble substances are transferred from the cell interior to the surrounding solution. Several methods can be used to enhance mass transfer in the osmotic process, such as stirring or rotation, pulsed vacuum, high pressure, ohmic heating, pulsed electric fields, centrifugation and ultrasound to reduce processing time. Pretreatment techniques such as vacuum or ultrasound are essential to accelerate the dehydration process, thereby improving quality and safety. Such pretreatment techniques are used to increase the mass transfer rate between the sample and its enclosure, thereby accelerating the dehydration process. In addition, when fruits with abundant microscopic channels are coated with edible materials, the coating layer will act as an additional barrier during the osmotic process. Suitable coating materials can effectively inhibit extensive solid absorption during osmosis without much impact on dehydration. Studies have shown that suitable coating materials can effectively inhibit extensive solid absorption without affecting water removal. Xanthan gum (XG) is a widely used polysaccharide produced by the bacterial genus Xanthomonas and has been used in a wide range of technical fields. XG has been used in scaffolds for drug release, cartilage, co-encapsulation of probiotics, intestinal healing and neuronal differentiation due to its high biocompatibility. It is mainly used as a stabilizer, thickener or emulsifier in food. Due to its unique resistance to enzymatic degradation, its coating provides a long-lasting effect on fresh cut pieces and whole fruits. Zein is a proline and the main storage protein of corn, accounting for about 45-50% of the protein content of corn. Because zein is one of the most hydrophobic proteins, due to the presence of polar amino acids (such as leucine, praline and alanine), it is used as a coating material for candy, rice, fruits and nuts in the food industry. This biomaterial is a completely amorphous polymer that can be processed as a thermoplastic in the presence of high-boiling plasticizers such as triethylene glycol, glycerol, and oleic acid. Zein is a common ingredient used in the manufacture of plastics, paper coatings, adhesives, shellac substitutes, laminates, and solid color printed films. It is also used in the pharmaceutical industry for capsule coatings, allowing for protection, controlled release, and masking of flavors and aromas. Zein has also been studied for use as a structural material in packaging applications due to its film-forming properties. In particular, zein forms tough, smooth, abrasion-resistant, grease-resistant films or coatings that are resistant to attack by microorganisms. There have been no studies on xanthan gum and zein composite films for osmotic dehydration of fruits.

[0005] Refractive window drying is an emerging non-thermal technology for drying heat-sensitive purees, fruit and vegetable slices. The material is deposited uniformly in the form of a thin layer on a conveyor belt made of infrared transparent material or plastic film, which is located on the surface of circulating water as a heat source. The evaporated water in the material is discharged by an exhaust system above the conveyor belt, and the material is scraped off the conveyor belt after passing through a cold bath. The main advantages associated with this technology are the avoidance of cross contamination due to indirect contact of the material with the heat source, low cost due to short drying time, relatively low temperature and atmospheric pressure, and better retention of physicochemical properties due to temperatures as low as 30°C caused by simultaneous convective heat transfer and evaporative cooling. In recent years, refractive window drying has been applied to the commercial production of dried herbs, fruits and vegetables, nutritional supplements and high-value-added foods rich in antioxidants.

[0006] Cheng Shasha et al. (patent application number: CN202110894866.1) provide a method for preparing dried kiwifruit by ultrasonic osmotic dehydration combined with hot air drying, and the specific steps are as follows: after the kiwifruit is selected, peeled and sliced, it is first vacuum treated at 30-50kPa for 5-15min, then ultrasonic-assisted osmotic dehydration is performed, and then hot air drying is performed. The invention uses a method for preparing dried kiwifruit by ultrasonic osmotic dehydration combined with hot air drying, which adds sweetness and flavor to the dried kiwifruit, and the color and texture are well maintained, and the nutritional content and antioxidant capacity are improved. The synergistic effect of ultrasound and hypertonic solution improves the mass transfer efficiency during osmotic dehydration, resulting in more water loss and sugar gain, while accelerating the subsequent hot air drying process and improving product quality. Tang Youcheng (patent application number: CN201711465132.1) provides a method for preparing dried apples by ultrasonic osmotic dehydration combined with microwave drying, which belongs to the field of fruit and vegetable product processing technology, including pretreatment, sterilization and enzyme inactivation, ultrasonic osmotic dehydration, microwave drying and other steps. The method of drying apples by microwaves has a low processing temperature, a small amount of additives, a high degree of fruit flavor retention, a low nutrient loss, and a storage resistance, which meets the needs of healthy food. Lin Xian et al. (patent application number: CN201610080124.4) provide a high-efficiency osmotic dehydration method for preserved fruits, which includes the following steps: 1) pre-treating the fruit raw materials; 2) preparing a permeate; 3) adding the fruit raw materials and the permeate to an ultrasonic device for ultrasonic treatment; 4) adding the material in step 3) to a vacuum permeation device, vacuuming, vacuum treatment, and then normal pressure permeation. The treatment methods of the invention are all physical methods, which basically do not change the structure of the chemical components in the food, avoid the loss of nutrient components in the pulp, improve the quality of preserved fruit products, and the products are safe and reliable. Liu Yunhong et al. (patent application number: CN201510163222.X) announced a method of ultrasonic osmotic dehydration and color protection combined with vacuum drying. The method combines the color protection process with osmotic dehydration pretreatment, removes part of the moisture in the material through osmotic dehydration, uses ultrasound to strengthen the osmotic dehydration process, and simultaneously protects the color during the ultrasonic osmotic dehydration process. The color protection and osmotic dehydration are organically combined, and a reasonable osmotic fluid is prepared to achieve simultaneous color protection and osmotic dehydration. Not only does it protect the product quality through color protection, but it also achieves partial dehydration of the material moisture through osmotic dehydration. At the same time, ultrasound is used to strengthen the osmotic dehydration process, which is beneficial to improve the quality of the dried product and shorten the drying process time. Sheng Jinfeng et al. (patent application number: 201811124868.7) provided a method for processing persimmon slice preserved fruit, which includes the following steps: S1, fruit selection and astringency removal; S2, color protection;

[0007] S3, differential pressure osmotic dehydration; S4, heat pump # microwave combined drying; S5, packaging; S6, irradiation sterilization. The preserved persimmon slices obtained by the invention are golden yellow, non-astringent, sweet in taste, and have a shelf life of up to 18 months. The present invention provides a method for preparing citrus slice products by film coating, ultrasonic vacuum osmotic dehydration and refractive window drying. On the basis of ultrasonic osmotic dehydration, film coating and vacuum treatment are added synergistically, which greatly promotes the removal of moisture compared with single film coating, ultrasonic and vacuum osmotic dehydration, reduces the infiltration of sugars compared with ultrasonic and vacuum osmotic dehydration, and accelerates the subsequent refractive window drying process, thereby improving product quality. Summary of the invention

[0008] The purpose of the present invention is to provide a low-temperature composite dehydration method for citrus sliced ​​fruits for tea drinking, which simultaneously achieves the effect of reducing sugar, reduces the time required for the subsequent low-temperature drying process, and protects the quality of the dried product to the greatest extent.

[0009] The technical solution of the present invention:

[0010] A low-temperature composite dehydration method for citrus sliced ​​fruits for tea drinking, the main steps are as follows:

[0011] (1) Wash the citrus fruits and slice them into 2-5 mm slices;

[0012] (2) Sliced ​​citrus fruits are coated with xanthan gum-zein;

[0013] (3) subjecting the coated fruit to ultrasonic vacuum penetration treatment in a sucrose solution;

[0014] (4) Refraction window drying of citrus fruits after osmotic dehydration.

[0015] The citrus fruits selected in step (1) have a diameter of 70-75 mm, a maturity of 80-90%, and no mechanical damage or insect damage.

[0016] The coating steps of the xanthan gum-zein film in step (2) are as follows:

[0017] (1) mixing 1-3% xanthan gum aqueous solution and 5-8% zein ethanol solution in a mass ratio of 1:1-1:5 to prepare a mixed film solution;

[0018] (2) adding 25% to 35% by weight of glycerol as a plasticizer to the mixed membrane solution;

[0019] (3) Magnetic stirring at 50-80°C for 12-18h to obtain a homogeneous membrane solution;

[0020] (4) Soaking the sliced ​​citrus fruits in the homogenized membrane solution for 5-10 minutes;

[0021] (5) taking out the soaked citrus fruits and cross-linking them in a CaCl2 solution with a concentration of 1-3% for 5-10 minutes;

[0022] (6) The cross-linked citrus fruit is placed in a mold covered with plastic wrap and dried at 30-50° C. for 10-20 min to allow the film to be stably coated on the surface of the fruit.

[0023] The sucrose concentration of the sucrose solution in the osmotic treatment of step (3) is 40-70° Brix, and the solid-liquid ratio is 1:4-1:10.

[0024] The vacuum degree of the vacuum treatment in step (3) is 0.01-0.05 MPa, and the treatment time is 10-20 min.

[0025] In the step (3), the power of ultrasound is 100-300W, and the treatment time is 10-20min.

[0026] In the step (3), the ultrasonic treatment and the vacuum treatment start and end at the same time, and the treatment time is 10-20 minutes.

[0027] After the ultrasonic vacuum infiltration treatment in step (3) is completed, it is continued at room temperature and atmospheric pressure for 60-180 minutes.

[0028] After step (3) is completed, the sliced ​​citrus fruits are soaked in distilled water for 3-5 seconds and then drained.

[0029] In the step (4), the conveyor belt length for drying the refractive window is 1.5-2m, the conveyor belt thickness is 0.1-0.3mm, the conveyor belt speed is 0.5-3m / min, the circulating hot water temperature is 94-98°C, the drying temperature is 30-60°C, and the drying is performed until the moisture content is 25-30%.

[0030] The beneficial effects of the present invention are:

[0031] (1) The coating and ultrasonic vacuum accelerated the water removal of citrus fruit slices during the osmotic dehydration process, removing about 42% of the water in the fresh sample. In the same period of time, it removed about 14% more water in the fresh sample than ordinary osmotic dehydration, and removed about 7% more water in the fresh sample than single coating, ultrasonic, and vacuum osmotic dehydration.

[0032] (2) The synergistic effect of coating and ultrasonic vacuum penetration dehydration reduces the time required for subsequent drying, saving 50% of the time compared with direct drying of fresh samples, 43% of the time compared with ordinary penetration dehydration, and 33% of the time compared with single coating, ultrasonic, and vacuum penetration dehydration.

[0033] (3) The coating synergistically combined with ultrasonic vacuum osmotic dehydration not only accelerated the removal of water, but also effectively reduced the infiltration of sugars during the osmotic process. Compared with ordinary osmotic dehydration, the sugar content was reduced by about 20%, and compared with single ultrasonic and vacuum osmotic dehydration, the sugar content was reduced by about 35%. There was no significant difference compared with single coating osmotic dehydration.

[0034] (4) The coating film synergistically with ultrasonic vacuum penetration dehydration can maintain the quality well after drying, with a color change of 5-6, a hardness of 51-53g, and an ascorbic acid content of 25-28mg / 100g. At the same time, it achieves the effect of reducing sugar content, reduces the time required for the subsequent low-temperature drying process, and retains the product quality to a large extent. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] Example 1 Comparison of Xanthan Gum-Zein and Other Membranes in Osmotic Dehydration of Orange Slices

[0037] Steps for osmotic dehydration of orange slices:

[0038] (1) Wash the orange and slice it into 3 mm slices;

[0039] (2) Sliced ​​oranges are coated;

[0040] (3) The coated orange slices were subjected to an infiltration treatment in a sucrose solution with a concentration of 50° Brix. The solid-liquid ratio was 1:4 and the treatment lasted for 180 min under atmospheric pressure.

[0041] The preparation method of the xanthan gum-zein film in step (2) is as follows:

[0042] 1) mixing 1% xanthan gum aqueous solution and 5% zein ethanol solution in a mass ratio of 1:1 to prepare a membrane solution;

[0043] 2) adding glycerol in an amount of 25% by mass of the mixed membrane solution in (1) as a plasticizer;

[0044] 3) Magnetic stirring was performed at 60°C for 12 h to obtain a membrane solution, which was then poured into a glass culture dish;

[0045] 4) Dry at 45°C, then pour 1% CaCl2 solution as a cross-linking agent, continue drying at 45°C and then remove the film;

[0046] 5) Equilibrate in a desiccator for 36 hours.

[0047] The xanthan gum-zein film coating process described in step (2) is as follows:

[0048] 1) Soak the orange slices in the membrane solution for 5 minutes;

[0049] 2) After removal, cross-link in a 1-3% CaCl2 solution for 5 minutes;

[0050] 3) Place the fruit in a petri dish covered with plastic wrap and dry at 45°C for 10 min to allow the film to stably coat the fruit surface.

[0051] The moisture content and total sugar content of orange slices treated with different coatings after osmotic dehydration are shown in Table 1. The orange slices coated with xanthan gum-zein have the lowest moisture content and the least sugar content, indicating that the xanthan gum and zein composite membrane can promote the removal of water better than the xanthan gum and zein single membrane and other composite membranes in osmotic dehydration, and at the same time can more effectively prevent the entry of sugar molecules in the osmotic solution, thereby achieving the effect of reducing sugar.

[0052] Table 1 Comparison of xanthan gum-zein and other membranes in osmotic dehydration

[0053]

[0054] Example 2 A low-temperature composite dehydration method for orange slices for tea drinking

[0055] A low-temperature composite drying method for orange slices for tea drinking, the main production steps are as follows:

[0056] (1) Wash the oranges and slice them into 3 mm slices.

[0057] (2) Sliced ​​oranges are coated with xanthan gum-zein.

[0058] (3) The coated orange slices were subjected to ultrasonic vacuum penetration treatment in a sucrose solution with a concentration of 50° Brix. The solid-liquid ratio was 1:4, the vacuum degree was 0.01 MPa, the ultrasonic power was 300 W, and the treatment time was 20 min. The treatment was then continued for 180 min at room temperature and atmospheric pressure.

[0059] (4) The osmotic dehydration citrus fruits were subjected to refractive window drying at a temperature of 30° C. until the moisture content was 30%.

[0060] The preparation method of the xanthan gum-zein film described in step (2) is as follows:

[0061] 1) mixing 1% xanthan gum aqueous solution and 5% zein ethanol solution in a mass ratio of 1:1 to prepare a membrane solution;

[0062] 2) adding glycerol in an amount of 25% by mass of the mixed membrane solution in (1) as a plasticizer;

[0063] 3) Magnetic stirring was performed at 60°C for 12 h to obtain a membrane solution, which was then poured into a glass culture dish;

[0064] 4) Dry at 45°C, then pour 1% CaCl2 solution as a cross-linking agent, continue drying at 45°C and then remove the film;

[0065] 5) Equilibrate in a desiccator for 36 hours.

[0066] The xanthan gum-zein film coating process described in step (2) is as follows:

[0067] 1) Soak the orange slices in the membrane solution for 5 minutes;

[0068] 2) After removal, cross-link in a 1-3% CaCl2 solution for 5 minutes;

[0069] 3) Place the fruit in a petri dish covered with plastic wrap and dry at 45°C for 10 min to allow the film to stably coat the fruit surface.

[0070] The physicochemical properties of orange slices prepared by different treatments of osmotic dehydration and osmotic dehydration-refractive window drying are shown in Table 1. The orange slices prepared by coating-ultrasonic vacuum penetration had the lowest moisture content and the least sugar content, and the corresponding physicochemical properties of the dried orange slices were also best preserved.

[0071] Table 2 Physicochemical properties of osmotic dehydration and osmotic dehydration-refractive window dried orange slices

[0072]

[0073] Example 3 A low-temperature composite dehydration method for lemon slices for tea drinking

[0074] A low-temperature composite dehydration method for lemon slices for tea drinking, the main production steps are as follows:

[0075] (1) Wash the lemon and slice it into 4 mm slices.

[0076] (2) Sliced ​​lemons are coated with xanthan gum-zein.

[0077] (3) The coated lemon slices were subjected to ultrasonic vacuum penetration treatment in a sucrose solution with a concentration of 40° Brix. The solid-liquid ratio was 1:5, the vacuum degree was 0.02 MPa, the ultrasonic power was 150 W, and the treatment time was 20 min. The treatment was then continued for 180 min at room temperature and atmospheric pressure.

[0078] (4) The lemon slices after osmotic dehydration are subjected to refraction window drying at a temperature of 30° C. until the moisture content is 25%.

[0079] The preparation method of the xanthan gum-zein film described in step (2) is as follows:

[0080] 1) mixing 1% xanthan gum aqueous solution and 6% zein ethanol solution in a mass ratio of 1:2 to prepare a membrane solution;

[0081] 2) adding 30% of the mass of the mixed membrane solution in (1) glycerol as a plasticizer;

[0082] 3) Magnetic stirring was performed at 60°C for 12 h to obtain a membrane solution, which was then poured into a glass culture dish;

[0083] 4) Dry at 40°C, then pour 1% CaCl2 solution as a cross-linking agent, continue drying at 40°C and then remove the film;

[0084] 5) Equilibrate in a desiccator for 30 hours.

[0085] The xanthan gum-zein film coating process described in step (2) is as follows:

[0086] 1) Soak the lemon slices in the membrane solution for 8 minutes;

[0087] 2) After removal, cross-link in 1% CaCl2 solution for 8 minutes;

[0088] 3) Place the fruit in a petri dish covered with plastic wrap and dry at 45°C for 10 min to allow the film to stably coat the fruit surface.

[0089] The physicochemical properties of lemon slices prepared by different treatments of osmotic dehydration and osmotic dehydration-refractive window drying are shown in Table 1. The lemon slices prepared by coating-ultrasonic vacuum penetration had the lowest moisture content and the least sugar content, and the corresponding physicochemical properties of the dried orange slices were also best preserved.

[0090] Table 3 Physicochemical properties of osmotic dehydration and dried lemon slices

[0091]

[0092]

[0093] Example 4 A low-temperature composite dehydration method for grapefruit slices for tea drinking

[0094] A low-temperature composite drying method for grapefruit slices for tea drinking, the main production steps are as follows:

[0095] (1) Wash the grapefruit and slice it into 5 mm slices.

[0096] (2) Sliced ​​grapefruit is coated with xanthan gum-zein.

[0097] (3) The coated grapefruit slices were subjected to ultrasonic vacuum penetration treatment in a sucrose solution with a concentration of 70° Brix. The solid-liquid ratio was 1:10, the vacuum degree was 0.04 MPa, the ultrasonic power was 200 W, and the treatment time was 20 min. The treatment was then continued for 180 min at room temperature and atmospheric pressure.

[0098] (4) The osmotic dehydration citrus fruits were subjected to refractive window drying at a temperature of 30° C. until the moisture content was 30%.

[0099] The preparation method of the xanthan gum-zein film described in step (2) is as follows:

[0100] 1) mixing 1% xanthan gum aqueous solution and 8% zein ethanol solution in a mass ratio of 1:4 to prepare a membrane solution;

[0101] 2) adding 30% of the mass of the mixed membrane solution in (1) glycerol as a plasticizer;

[0102] 3) Magnetic stirring was performed at 60°C for 12 h to obtain a membrane solution, which was then poured into a glass culture dish;

[0103] 4) Dry at 50°C, then pour 3% CaCl2 solution as a cross-linking agent, continue drying at 50°C and then remove the film;

[0104] 5) Equilibrate in a desiccator for 48 hours.

[0105] The xanthan gum-zein film coating process described in step (2) is as follows:

[0106] 1) Soak the grapefruit slices in the membrane solution for 10 minutes;

[0107] 2) After taking out, cross-link in 3% CaCl2 solution for 10 min;

[0108] 3) Place the fruit in a petri dish covered with plastic wrap and dry at 50°C for 10 min to allow the film to stably coat the fruit surface.

[0109] The physicochemical properties of grapefruit slices prepared by osmotic dehydration and osmotic dehydration-refractive window drying with different treatments are shown in Table 1. The grapefruit slices prepared by coating-ultrasonic vacuum penetration had the lowest moisture content and the least sugar content, and the corresponding physicochemical properties of the dried grapefruit slices were also best preserved.

[0110] Table 4 Physicochemical properties of grapefruit slices dried by osmotic dehydration and osmotic dehydration-refractive window

[0111]

Claims

1. A low-temperature composite dehydration method for citrus sliced ​​fruits for tea drinking, characterized in that: The main steps are as follows: (1) Wash the citrus fruits and slice them into 2-5 mm slices; (2) Sliced ​​citrus fruits are coated with xanthan gum-zein film; the coating steps of the xanthan gum-zein film are as follows: ① Mixing 1-3% xanthan gum aqueous solution and 5-8% zein ethanol solution in a mass ratio of 1:1-1:5 to prepare a mixed film solution; ② Add 25%-35% by weight of glycerin as a plasticizer to the mixed membrane solution; ③50-80℃ magnetic stirring for 12-18h to obtain a homogeneous membrane liquid; ④ Soak the sliced ​​citrus fruits in the homogenized membrane solution for 5-10 minutes; ⑤ Take out the soaked citrus fruits and cross-link them in a 1-3% CaCl2 solution for 5-10 minutes; ⑥ Place the cross-linked citrus fruit in a mold covered with plastic wrap and dry at 30-50°C for 10-20 minutes to allow the film to be stably coated on the surface of the fruit; (3) subjecting the coated fruit to ultrasonic vacuum penetration treatment in a sucrose solution; the power of the ultrasound is 100-300 W, and the treatment time is 10-20 min; the vacuum degree of the vacuum treatment is 0.01-0.05 MPa, and the treatment time is 10-20 min; the ultrasound and vacuum treatment start and end at the same time, and the treatment time is 10-20 min; (4) Refraction window drying of citrus fruits after osmotic dehydration.

2. The low-temperature composite dehydration method for citrus sliced ​​fruits for tea drinking according to claim 1, characterized in that: The citrus fruits selected in step (1) have a diameter of 70-75 mm, a maturity of 80-90%, and no mechanical damage or insect infestation.

3. The low-temperature composite dehydration method for citrus sliced ​​fruits for tea drinking according to claim 1, characterized in that: The sucrose concentration of the sucrose solution in the osmotic treatment in step (3) is 40-70 °Brix, and the solid-liquid ratio is 1:4-1:

10.

4. The low-temperature composite dehydration method for citrus sliced ​​fruits for tea drinking according to claim 1, characterized in that: After the ultrasonic vacuum infiltration treatment in step (3) is completed, it is continued at room temperature and atmospheric pressure for 60-180 minutes.

5. The low-temperature composite dehydration method for citrus sliced ​​fruits for tea drinking according to claim 1, characterized in that: After step (3), soak the sliced ​​citrus fruits in distilled water for 3-5 seconds and then drain.

6. The low-temperature composite dehydration method for citrus sliced ​​fruits for tea drinking according to claim 1, characterized in that: In step (4), the conveyor belt length of the refractive window drying is 1.5-2m, the conveyor belt thickness is 0.1-0.3mm, the conveyor belt speed is 0.5-3m / min, the circulating hot water temperature is 94-98°C, the drying temperature is 30-60°C, and the drying is performed until the moisture content is 25-30%.

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