Tea-flavored fruit freeze-dried tablet and preparation method thereof

Abstract

The invention provides a tea-flavored fruit freeze-dried tablet and a preparation method thereof, and belongs to the technical field of food processing. The preparation method comprises the following steps: slicing fruits to obtain fruit slices, and performing tea flavor treatment on the fruit slices to obtain the tea flavor fruit slices. The preparation method can endow the dried fruit slices with special tea flavor and tea fragrance, and can also form a layer of edible film with a barrier effect on the surface layers of the dried fruit slices, and the film can effectively inhibit oxidation browning of the dried fruit slices, improve the nutritional ingredients and rehydration rate of the tea-flavored freeze-dried fruit slices, and improve the taste of the tea-flavored freeze-dried fruit slices. The water content of the tea-flavored fruit freeze-dried slices meets the requirement that the water content in GB / T 23787-2009 non-fried fruit and vegetable crisp slices is smaller than or equal to 5%, the tea-flavored fruit freeze-dried slices can release flavor, color and aroma components of tea leaves in the brewing process, and the sensory quality is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and in particular relates to a tea-flavored fruit freeze-dried tablet and a preparation method thereof. Background Art

[0002] Dried fruit chips are a snack product made by slicing and drying fruit to remove most of its moisture. Compared to fresh fruit, dried fruit chips are less irritating to the digestive tract, retain the dietary fiber and minerals found in the peel, and are easy to carry and have a long shelf life. They are an increasingly popular healthy snack.

[0003] Currently, processed dried fruit slices undergo oxidative browning, primarily from vitamin C, during storage, and the product gradually darkens and blackens over time. Although sulfite treatment can effectively inhibit browning, its side effects have led many countries to ban its use in certain foods. Therefore, it is important to find a safe and effective process for preventing browning in dried fruit slices, thereby further extending their shelf life and enhancing their commercial value. Furthermore, some dried fruit slices (such as lemons) often have a noticeably unpleasant taste when mixed with water due to the acidic and bitter components contained in their raw materials. Developing a method for preparing dried fruit slices that can improve the product's unique taste and aroma quality from a flavor coordination perspective is a currently pressing technical issue. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a tea-flavored freeze-dried fruit slice and a preparation method thereof. The preparation method of the present invention imparts a unique tea flavor and tea aroma to the dried fruit slice and can also safely and effectively inhibit oxidative browning of the dried fruit slice.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing tea-flavored fruit freeze-dried tablets, comprising the following steps:

[0007] Slicing the fruit to obtain fruit slices, and then subjecting the fruit slices to tea flavoring to obtain tea-flavored fruit slices;

[0008] The tea flavoring treatment includes a tea powder coating treatment method or a tea soup soaking treatment method;

[0009] The tea powder coating processing method comprises the following steps:

[0010] Crush the tea leaves, sieve them, and apply the obtained tea powder on the surface of the fruit slices;

[0011] The tea soaking soup processing method comprises the following steps:

[0012] The tea leaves are soaked in boiling water, filtered, and the collected extract is soaked with fruit slices.

[0013] Preferably, after obtaining the tea-flavored fruit slices, the process further comprises the following steps:

[0014] Freezing the tea-flavored fruit slices to obtain frozen fruit slices;

[0015] The frozen fruit slices are impregnated with a seaweed polysaccharide solution to obtain impregnated tea-flavored fruit slices;

[0016] cross-linking the soaked tea-flavored fruit slices with a metal ion solution to obtain cross-linked tea-flavored fruit slices;

[0017] The cross-linked tea-flavored fruit slices are frozen and then vacuum-freeze-dried to obtain tea-flavored fruit freeze-dried slices.

[0018] Preferably, the thickness of the slices is 3.5 to 4.5 mm; the fruit is lemon; and the tea is oolong tea.

[0019] Preferably, the mesh size of the sieving is 180-240 mesh; the number of extractions is 1-3 times, and the time for each extraction is 20-30 minutes; the mass volume ratio of the tea leaves to boiling water is 1g: (9-15) mL; and the volume mass ratio of the extract to the fruit slices is 150-200 mL: 10-15 g.

[0020] Preferably, the freezing temperature is -25 to -18°C, and the freezing time is 5 to 10 minutes.

[0021] Preferably, the components of the seaweed polysaccharide solution include sodium alginate and gellan gum, and the mass ratio of the sodium alginate to gellan gum is (1-3):(5-8); the volume mass ratio of the seaweed polysaccharide solution to the frozen fruit slices is 100-150 mL:5-10 g; the immersion time is 30-60 s; during the immersion treatment, the temperature of the seaweed polysaccharide solution is 35-45°C.

[0022] Preferably, the metal ion solution includes a CaCl2 solution or a ZnCl2 solution; the mass volume ratio of the soaked tea-flavored fruit slices to the metal ion solution is 5-10 g:120-200 mL; the cross-linking temperature is 25-40° C., and the cross-linking time is 0.5-1 min.

[0023] Preferably, the mass volume percentage of the metal ion solution is 1 to 3%.

[0024] Preferably, the freezing temperature is -50°C to -80°C, and the freezing time is 6 to 8 hours; the vacuum freeze-drying method is segmented vacuum drying: the shelf temperature in the vacuum sublimation drying stage is 35 to 45°C and the vacuum degree is 50 to 150 Pa; the shelf temperature in the vacuum decomposition drying stage is 45 to 55°C and the vacuum degree is 40 to 100 Pa; during the entire vacuum drying period, the cold trap temperature is maintained at -70°C to -50°C.

[0025] The present invention also provides a tea-flavored fruit freeze-dried tablet prepared by the above preparation method.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The invention provides a preparation method of tea-flavored freeze-dried fruit slices. The preparation method can not only impart a unique tea flavor and tea aroma to the dried fruit slices, but also form an edible film with a barrier effect on the surface of the dried fruit slices. The film can effectively inhibit oxidative browning of the dried fruit slices, thereby increasing the nutritional content and rehydration rate of the tea-flavored freeze-dried fruit slices. The moisture content of the tea-flavored freeze-dried fruit slices meets the requirement of ≤5% in GB / T23787-2009 "Non-fried Fruit and Vegetable Crisps". The tea-flavored freeze-dried fruit slices can also release the flavor, color and aroma components of tea during the brewing process, thereby improving the sensory quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a picture of the tea-flavored lemon freeze-dried tablet of Comparative Example 3;

[0029] Figure 2 This is a picture of the tea-flavored lemon freeze-dried tablet of Example 1;

[0030] Figure 3 This is a picture of the tea-flavored lemon freeze-dried tablet of Comparative Example 4;

[0031] Figure 4 This is a picture of the tea-flavored lemon freeze-dried tablet of Example 2;

[0032] Figure 5 The curve results of the change of VC content of different lemon freeze-dried tablets with storage time;

[0033] Figure 6 This is the L* value diagram of different lemon freeze-dried tablets;

[0034] Figure 7 The a* value diagram of different lemon freeze-dried slices;

[0035] Figure 8 The b* value diagram of different lemon freeze-dried slices;

[0036] Figure 9 ΔE* value diagram of different lemon freeze-dried tablets;

[0037] Figure 10 The browning changes of different lemon freeze-dried slices over storage time are shown in the figure. DETAILED DESCRIPTION

[0038] The present invention provides a method for preparing tea-flavored fruit freeze-dried tablets, comprising the following steps:

[0039] Slicing the fruit to obtain fruit slices, and then subjecting the fruit slices to tea flavoring to obtain tea-flavored fruit slices;

[0040] The tea flavoring treatment includes a tea powder coating treatment method or a tea soup soaking treatment method;

[0041] The tea powder coating processing method comprises the following steps:

[0042] Crush the tea leaves, sieve them, and apply the obtained tea powder on the surface of the fruit slices;

[0043] The tea soaking soup processing method comprises the following steps:

[0044] The tea leaves are soaked in boiling water, filtered, and the collected extract is soaked with fruit slices.

[0045] In the present invention, fruit slices are obtained by slicing fruit. The fruit is preferably lemon. Before slicing, the fresh fruit is washed to ensure that the washed fresh fruit is clean. The slices are preferably 3.5 to 4.5 mm thick, more preferably 3.7 to 4.4 mm thick, and even more preferably 4 mm, 4.2 mm, or 4.3 mm thick. The thickness of the slices produced by the present invention ensures that the moisture content of the resulting tea-flavored lemon freeze-dried slices is less than 5%, resulting in strong rehydration and a high vitamin C content.

[0046] In the present invention, after obtaining the fruit slices, the fruit slices are subjected to a tea flavoring treatment to obtain tea-flavored fruit slices. The tea flavoring treatment preferably adopts a tea powder coating treatment method or a tea soup soaking treatment method. When the tea powder coating is used for the tea flavoring treatment, the tea is preferably oolong tea. The mesh number of the sieve is preferably 180-240 mesh, more preferably 200-220 mesh, and more preferably 205, 210, 215 or 220 mesh. After obtaining the tea powder, the tea powder is coated on the surface of the fruit slices. The present invention does not specifically limit the coating method. Methods known in the art are used as long as the tea powder is evenly coated on the surface of the fruit slices. The mass ratio of the tea powder to the fruit slices is preferably 1:30-50, more preferably 1:35-45, and more preferably 1:40. When using tea soup for tea flavoring, the tea leaves are preferably oolong tea; the number of extractions is preferably 1 to 3 times, more preferably 2 times, and the time for each extraction is preferably 20 to 30 minutes, more preferably 22 to 30 minutes, more preferably 20, 23, 25, 27 or 30 minutes; the mass volume ratio of the tea leaves to boiling water is preferably 1g: (9 to 15) mL, more preferably 1g: (9 to 12) mL, more preferably 1g: 9 mL, 1g: 10 mL, 1g: 11 mL or 1g: 12 mL. The filtered and collected extract is soaked with fruit slices. During the soaking, the extract is cooled to room temperature, which is 20 to 25°C, such as 21, 22, 23, 24 or 25°C, that is, the soaking temperature is the above room temperature. The volume mass ratio of the extract to the fruit slices is preferably 150 to 200 mL: 10 to 15 g. The present invention further preferably uses 160-190 mL:10-15 g, more preferably 170 mL:10-15 g, 180 mL:10-15 g or 190 mL:10-15 g, such as 180 mL:10 g. The present invention utilizes a tea powder coating method or a tea soup soaking method to treat the fruit slices with tea flavor, and the resulting tea-flavored fruit freeze-dried slices have good rehydration performance, the moisture content of the tea-flavored fruit freeze-dried slices meets the requirement of moisture content ≤5% in GB / T23787-2009 "Non-fried Fruit and Vegetable Crisps", and can also maximize the VC content of the tea-flavored fruit freeze-dried slices, reduce browning of the tea-flavored fruit freeze-dried slices, extend the storage time, and have high safety. The tea-flavored fruit freeze-dried slices after brewing have a high comprehensive score for soup color, aroma, taste, and mouthfeel. In particular, the tea-flavored fruit freeze-dried slices treated with tea powder have a more obvious effect.

[0047] In the present invention, after obtaining the tea-flavored fruit slices, the following steps are further included:

[0048] Freezing the tea-flavored fruit slices to obtain frozen fruit slices;

[0049] The frozen fruit slices are impregnated with a seaweed polysaccharide solution to obtain impregnated tea-flavored fruit slices;

[0050] cross-linking the soaked tea-flavored fruit slices with a metal ion solution to obtain cross-linked tea-flavored fruit slices;

[0051] The cross-linked tea-flavored fruit slices are frozen and then vacuum-freeze-dried to obtain tea-flavored fruit freeze-dried slices.

[0052] In the present invention, tea-flavored fruit slices are frozen to obtain frozen fruit slices. The freezing temperature is preferably -25 to -18°C, more preferably -24 to -19°C, and more preferably -20°C, -21°C, or -23°C. The freezing time is preferably 5 to 10 minutes, more preferably 6 to 9 minutes, such as 7 or 8 minutes. The present invention first performs tea flavoring treatment and then freezes the tea-flavored fruit slices. The tea-flavored fruit freeze-dried slices finally obtained have good rehydration properties. The moisture content of the tea-flavored fruit freeze-dried slices meets the requirement of moisture content ≤5% in GB / T23787-2009 "Non-fried Fruit and Vegetable Crisps", and can also maximize the VC content of the tea-flavored fruit freeze-dried slices.

[0053] In the present invention, after obtaining the frozen fruit slices, the frozen fruit slices are impregnated with a seaweed polysaccharide solution to obtain impregnated tea-flavored fruit slices. The components of the seaweed polysaccharide solution include sodium alginate and gellan gum, and the mass ratio of the sodium alginate to the gellan gum is preferably (1-3): (5-8), more preferably (1.5-2.5): (5.5-7.5), and more preferably 2:6. Taking the mass ratio of sodium alginate to gellan gum as 2:6 as an example, the preparation method of the seaweed polysaccharide solution is to mix 0.25g of sodium alginate and 0.75g of gellan gum, add 100mL of 60°C distilled water, dissolve in a constant temperature water bath at 65°C with magnetic stirring, and homogenize under high pressure at 28MPa for 7.5min to obtain a seaweed polysaccharide solution. The volume mass ratio of the seaweed polysaccharide solution to the frozen fruit slices is preferably 100-150 mL:5-10 g, more preferably 110-140 mL:5-8 g, and more preferably 120 mL:6 g; the immersion time is preferably 30-60 s, more preferably 35-55 s, and more preferably 40, 45 or 50 s; during the immersion treatment, the temperature of the seaweed polysaccharide solution is preferably 35-45°C.

[0054] In the present invention, after obtaining the impregnated tea-flavored fruit slices, the impregnated tea-flavored fruit slices are cross-linked with a metal ion solution to obtain cross-linked tea-flavored fruit slices. The metal ion solution includes a CaCl2 solution or a ZnCl2 solution; the mass volume percentage of the metal ion solution is preferably 1-3%, more preferably 2%; taking the CaCl2 solution as an example, the preparation method of the CaCl2 solution with a mass volume percentage of 1-3% is to mix 1-3g of CaCl2 with 100mL of distilled water. The mass volume ratio of the impregnated tea-flavored fruit slices to the metal ion solution is preferably 5-10g:120-200mL, more preferably 6-9g:140-180mL, and more preferably 8g:160mL; the cross-linking temperature is preferably 25-40°C, more preferably 28-35°C, such as 30°C, and the cross-linking time is preferably 0.5-1min, more preferably 0.5min, 0.7min or 1min. The present invention utilizes a metal ion solution to cross-link the soaked tea-flavored fruit slices. This, on the one hand, solidifies the fruit slices, better maintaining their plump appearance, thereby ultimately improving the yield of the tea-flavored fruit freeze-dried slices. Furthermore, after cross-linking, a dense outer film is formed on the surface of the tea-flavored fruit freeze-dried slices, effectively delaying the oxidative browning of vitamin C during subsequent processing, storage, transportation, and sales of the fruit slices, thereby improving the nutritional and appearance quality of the product. Furthermore, the film formed on the surface of the tea-flavored fruit freeze-dried slices can better delay the release and diffusion of flavoring and efficacy substances in tea leaves and fruits, such as alkaloids and tea polyphenols, when the product is soaked in water for drinking, thereby increasing the brewing time of the tea-flavored fruit freeze-dried slices to a certain extent.

[0055] In the present invention, after obtaining the cross-linked tea-flavored fruit slices, the cross-linked tea-flavored fruit slices are frozen and then vacuum-freeze-dried to obtain tea-flavored fruit freeze-dried slices. The freezing temperature is preferably -80°C to -50°C, more preferably -70°C to -60°C, more preferably -60, -65, or -70°C. The freezing time is preferably 6 to 8 hours, more preferably 6.5 to 7.5 hours, such as 7 hours. The vacuum freeze-drying method is staged vacuum drying: the shelf temperature in the vacuum sublimation drying stage is 35 to 45°C and the vacuum degree is 50 to 150 Pa; the shelf temperature in the vacuum desorption drying stage is 45 to 55°C and the vacuum degree is 40 to 100 Pa; during the entire vacuum drying period, the cold trap temperature is maintained at -70°C to -50°C. After obtaining the tea-flavored fruit freeze-dried slices, they are packaged, for example, by vacuum-sealing the freeze-dried tea-flavored lemon slices in an aluminum foil bag.

[0056] The present invention also provides a tea-flavored fruit freeze-dried tablet prepared by the above preparation method.

[0057] The tea-flavored fruit freeze-dried tablets prepared by the present invention have a complete appearance, uniform thickness, and no cracks. The tea-flavored fruit water after brewing is orange-yellow, clear, and bright, with a rich and harmonious fruit and tea aroma, an elegant and pure fragrance, a rich and harmonious taste, and a moderate and mellow tea flavor. Therefore, the tea-flavored fruit freeze-dried tablets receive a high comprehensive score in terms of appearance, color, aroma, and taste. Furthermore, the tea-flavored fruit freeze-dried tablets of the present invention form an edible film with a barrier effect, which effectively inhibits oxidative browning of the fruit slices, eliminates the need for sulfite treatment, and is highly safe and prolongs storage time. The moisture content of the tea-flavored fruit freeze-dried tablets meets the moisture content requirement of ≤5% in GB / T 23787-2009, "Non-fried Fruit and Vegetable Crisps," and the vitamin C content of the tea-flavored fruit freeze-dried tablets is maximized, with strong rehydration properties. Therefore, the tea-flavored fruit freeze-dried tablets of the present invention are of high quality.

[0058] In the present invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.

[0059] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0060] Example 1

[0061] A method for preparing tea-flavored lemon freeze-dried tablets, comprising the following steps:

[0062] (1) Raw material pretreatment: fresh lemons were selected, cleaned, and cut into slices with a thickness of 4 mm to obtain lemon slices;

[0063] (2) Tea flavoring treatment: ultrafinely grind oolong tea leaves, pass through a 210-mesh sieve to obtain tea powder, and evenly coat 2.0 g of the tea powder on the surface of 80 g of the lemon slices prepared in step (1) to obtain tea-flavored lemon slices coated with tea powder;

[0064] (3) Low-temperature freezing: Freeze the tea-flavored lemon slices coated with tea powder at -20°C for 8 minutes to obtain frozen lemon slices;

[0065] (4) Immersion treatment with seaweed polysaccharide solution: First, 2.5 g of sodium alginate and 7.5 g of gellan gum were mixed, and 1000 mL of 60°C distilled water was added. The mixture was dissolved by magnetic stirring in a constant temperature water bath at 65°C, and high pressure homogenization was performed at 28 MPa for 7.5 min to obtain a seaweed polysaccharide solution. Then, the frozen 80 g of tea-flavored lemon slices were immersed in 1200 mL of seaweed polysaccharide solution at 40°C for 45 s to obtain the immersed tea-flavored lemon slices.

[0066] (5) Cross-linking treatment: First, 20 g of CaCl2 was mixed with 1000 mL of distilled water to obtain a CaCl2 solution. Then, 80 g of the soaked tea-flavored lemon slices were immersed in 1600 mL of the CaCl2 solution at 30°C for 0.5 min to obtain cross-linked tea-flavored lemon slices.

[0067] (6) Low-temperature freezing: freezing the cross-linked tea-flavored lemon slices at -65°C for 7 hours to obtain frozen tea-flavored lemon slices;

[0068] (7) Vacuum freeze drying: The frozen tea-flavored lemon slices were vacuum freeze-dried. The shelf temperature in the sublimation drying stage was 40°C and the vacuum degree was 100 Pa; the shelf temperature in the desorption drying stage was 50°C and the vacuum degree was 80 Pa; the cold trap temperature during the entire vacuum drying period was -55°C, and freeze drying was performed for 14 hours to obtain tea-flavored lemon freeze-dried slices.

[0069] (8) Packaging: The freeze-dried tea-flavored lemon slices are sealed and packaged in a vacuum-packed aluminum foil bag to obtain the product.

[0070] Example 2

[0071] A method for preparing tea-flavored lemon freeze-dried tablets, comprising the following steps:

[0072] (1) Raw material pretreatment: fresh lemons were selected, cleaned, and cut into slices with a thickness of 4 mm to obtain lemon slices;

[0073] (2) Tea flavoring treatment: 100 g of oolong tea leaves were soaked in 900 mL of boiled water for 25 min, filtered to obtain a first extract and tea leaves after the first extraction; 100 g of the tea leaves after the first extraction were soaked in 1200 mL of boiled water for 30 min, filtered to obtain a second extract; the first extract and the second extract were combined to obtain tea soup, which was then cooled to room temperature; 100 g of lemon slices were soaked in 1800 mL of tea soup for 23 min to obtain tea-flavored lemon slices soaked in tea soup;

[0074] (3) Low-temperature freezing: Freeze the tea-flavored lemon slices coated with tea powder at -20°C for 8 minutes to obtain frozen lemon slices;

[0075] (4) Immersion treatment with seaweed polysaccharide solution: First, 0.25 g of sodium alginate and 0.75 g of gellan gum were mixed, and 100 mL of 60°C distilled water was added. The mixture was dissolved by magnetic stirring in a constant temperature water bath at 65°C, and high pressure homogenization was performed at 28 MPa for 7.5 min to obtain a seaweed polysaccharide solution. Then, the frozen 60 g of tea-flavored lemon slices were immersed in 1200 mL of seaweed polysaccharide solution at 38°C for 45 s to obtain the immersed tea-flavored lemon slices.

[0076] (5) Cross-linking treatment: First, 30 g of CaCl2 was mixed with 1500 mL of distilled water to obtain a CaCl2 solution. Then, 100 g of the soaked tea-flavored lemon slices were immersed in the 1500 mL of CaCl2 solution at 30°C for 0.5 min to obtain cross-linked tea-flavored lemon slices.

[0077] (6) Low-temperature freezing: freezing the cross-linked tea-flavored lemon slices at -65°C for 7 hours to obtain frozen tea-flavored lemon slices;

[0078] (7) Vacuum freeze drying: The frozen tea-flavored lemon slices were vacuum freeze-dried. The shelf temperature in the sublimation drying stage was 42°C and the vacuum degree was 100 Pa; the shelf temperature in the analytical drying stage was 48°C and the vacuum degree was 90 Pa; the cold trap temperature during the entire vacuum drying period was -60°C, and freeze drying was performed for 12 hours to obtain tea-flavored lemon freeze-dried slices.

[0079] (8) Packaging: The tea-flavored lemon freeze-dried tablets are sealed and packaged in a vacuum-packed aluminum foil bag to obtain the product.

[0080] Example 3

[0081] The difference between this embodiment and embodiment 1 is that step (1) of this embodiment is raw material pretreatment: fresh lemons are selected, cleaned, and cut into slices with a thickness of 4.5 mm to obtain lemon slices. The remaining steps are the same as those in embodiment 1.

[0082] Example 4

[0083] A method for preparing tea-flavored lemon freeze-dried tablets, comprising the following steps:

[0084] (1) Raw material pretreatment: fresh lemons were selected, cleaned, and cut into slices with a thickness of 4 mm to obtain lemon slices;

[0085] (2) Tea flavoring treatment: ultrafinely grind oolong tea leaves, pass through a 240-mesh sieve to obtain tea powder, and evenly coat 2.4 g of the tea powder on the surface of 90 g of the lemon slices prepared in step (1) to obtain tea-flavored lemon slices coated with tea powder;

[0086] (3) Low-temperature freezing: Freeze the tea-flavored lemon slices coated with tea powder at -18°C for 10 minutes to obtain frozen lemon slices;

[0087] (4) Seaweed polysaccharide solution immersion treatment: First, 3.0 g of sodium alginate and 12.0 g of gellan gum were mixed, and 1500 mL of 60°C distilled water was added. The mixture was dissolved by magnetic stirring in a constant temperature water bath at 65°C, and high pressure homogenization was performed at 28 MPa for 7.5 min to obtain a seaweed polysaccharide solution. Then, the frozen 90 g of tea-flavored lemon slices were immersed in 1350 mL of seaweed polysaccharide solution at 36°C for 30 s to obtain the immersed tea-flavored lemon slices.

[0088] (5) Cross-linking treatment: First, 20 g of CaCl2 was mixed with 2000 mL of distilled water to obtain a CaCl2 solution. Then, 90 g of the tea-flavored lemon slices after the impregnation were immersed in 1600 mL of the CaCl2 solution and cross-linked at 35°C for 1 min to obtain cross-linked tea-flavored lemon slices.

[0089] (6) Low-temperature freezing: freezing the cross-linked tea-flavored lemon slices at -55°C for 8 hours to obtain frozen tea-flavored lemon slices;

[0090] (7) Vacuum freeze drying: The frozen tea-flavored lemon slices were vacuum freeze-dried. The shelf temperature in the sublimation drying stage was 38°C and the vacuum degree was 90Pa; the shelf temperature in the analytical drying stage was 55°C and the vacuum degree was 80Pa; the cold trap temperature during the entire vacuum drying period was -55°C, and freeze drying was performed for 13 hours to obtain tea-flavored lemon freeze-dried slices.

[0091] (8) Packaging: The freeze-dried tea-flavored lemon slices are sealed and packaged in a vacuum-packed aluminum foil bag to obtain the product.

[0092] Example 5

[0093] A method for preparing tea-flavored lemon freeze-dried tablets, comprising the following steps:

[0094] (1) Raw material pretreatment: fresh lemons were selected, cleaned, and cut into slices with a thickness of 4 mm to obtain lemon slices;

[0095] (2) Tea flavoring treatment: ultrafinely grind oolong tea leaves and pass them through a 180-mesh sieve to obtain tea powder. Evenly coat 2.4 g of the tea powder on the surface of 90 g of the lemon slices prepared in step (1) to obtain tea-flavored lemon slices coated with tea powder.

[0096] (3) Low-temperature freezing: Freeze the tea-flavored lemon slices coated with tea powder at -25°C for 5 minutes to obtain frozen lemon slices;

[0097] (4) Immersion treatment of seaweed polysaccharide solution: First, 4.5 g of sodium alginate and 7.5 g of gellan gum were mixed, and 1500 mL of 60°C distilled water was added. The mixture was dissolved by magnetic stirring in a constant temperature water bath at 65°C, and high pressure homogenization was performed at 28 MPa for 7.5 min to obtain a seaweed polysaccharide solution. Then, the frozen 90 g of tea-flavored lemon slices were immersed in 1350 mL of seaweed polysaccharide solution at 42°C for 60 s to obtain the immersed tea-flavored lemon slices.

[0098] (5) Cross-linking treatment: First, 3 g of CaCl2 was mixed with 100 mL of distilled water to obtain a CaCl2 solution. Then, 90 g of the tea-flavored lemon slices after the impregnation were immersed in 1600 mL of the CaCl2 solution and cross-linked at 35°C for 1 min to obtain cross-linked tea-flavored lemon slices.

[0099] (6) low-temperature freezing: freezing the cross-linked tea-flavored lemon slices at -80°C for 6 hours to obtain frozen tea-flavored lemon slices;

[0100] (7) Vacuum freeze drying: The frozen tea-flavored lemon slices were vacuum freeze-dried. The shelf temperature in the sublimation drying stage was 42°C and the vacuum degree was 120 Pa; the shelf temperature in the analytical drying stage was 52°C and the vacuum degree was 100 Pa; the cold trap temperature during the entire vacuum drying period was -65°C, and freeze drying was performed for 15 hours to obtain tea-flavored lemon freeze-dried slices.

[0101] (8) Packaging: The freeze-dried tea-flavored lemon slices are sealed and packaged in a vacuum-packed aluminum foil bag to obtain the product.

[0102] Comparative Example 1

[0103] The difference between this comparative example and Example 1 is that, in this comparative example, the lemon slices of step (1) of Example 1 are first pre-frozen and then subjected to tea flavor treatment, that is, step (2) of this comparative example is: freezing the lemon slices of step (1) of Example 1 at -20°C for 8 minutes to obtain frozen lemon slices; step (3) is: tea flavor treatment: ultrafine grinding of oolong tea leaves, passing through a 210-mesh sieve to obtain tea powder, and evenly coating 2.0 g of tea powder on the surface of 80 g of frozen lemon slices to obtain tea-flavored lemon slices coated with tea powder; step (4) is: seaweed polysaccharide solution immersion treatment: first, 2.5 g of sodium alginate and 7.5 g of gellan gum are weighed and evenly mixed, and 1000 mL of 60°C distilled water was dissolved in a constant temperature water bath at 65°C with magnetic stirring, and then high pressure homogenized at 28 MPa for 7.5 minutes to obtain a seaweed polysaccharide solution. 80 g of the tea-flavored lemon slices coated with tea powder were then immersed in 1200 mL of the seaweed polysaccharide solution at 40°C for 45 seconds to obtain the soaked tea-flavored lemon slices. The remaining steps (5) to (8) were carried out as described in Example 1.

[0104] Comparative Example 2

[0105] The preparation method of fresh lemon freeze-dried tablets comprises the following steps:

[0106] (1) Raw material pretreatment: Select fresh lemons, clean them, and cut them into slices with a thickness of 4 mm to obtain lemon slices;

[0107] (2) Freezing the lemon slices at -65°C for 7 hours and then performing vacuum freeze drying. The vacuum freeze drying method is a staged vacuum drying method, wherein: the shelf temperature of the vacuum sublimation drying stage is 40°C and the vacuum degree is 100 Pa; the shelf temperature of the vacuum desorption drying stage is 50°C and the vacuum degree is 80 Pa; during the entire vacuum drying period, the cold trap temperature is maintained at -55°C, and freeze drying is performed for 14 hours until the lemon freeze-dried slices are obtained.

[0108] Comparative Example 3

[0109] The difference between this comparative example and Example 1 is that step (1) of this comparative example is raw material pretreatment: fresh lemons are selected, cleaned, and cut into slices with a thickness of 3 mm to obtain lemon slices. The remaining steps are the same as in Example 1.

[0110] Comparative Example 4

[0111] The difference between this comparative example and Example 2 is that step (1) of this comparative example is raw material pretreatment: fresh lemons are selected, cleaned, and cut into slices with a thickness of 3 mm to obtain lemon slices. The remaining steps are the same as in Example 2.

[0112] Comparative Example 5

[0113] The difference between this comparative example and Example 1 is that this comparative example does not perform cross-linking treatment, that is, the tea-flavored lemon slices after being impregnated in step (4) of Example 1 are directly subjected to the low-temperature freezing treatment of step (6): the impregnated tea-flavored lemon slices are frozen at -65°C for 7 hours to obtain frozen tea-flavored lemon slices. The subsequent steps refer to steps (7) to (8) of Example 1.

[0114] Comparative Example 6

[0115] The difference between this comparative example and Example 2 is that this comparative example does not perform cross-linking treatment, that is, the tea-flavored lemon slices after being soaked in step (4) of Example 2 are directly subjected to the low-temperature freezing treatment of step (6): the soaked tea-flavored lemon slices are frozen at -65°C for 7 hours to obtain frozen tea-flavored lemon slices. The subsequent steps refer to steps (7) to (8) of Example 2.

[0116] Comparative Example 7

[0117] The difference between this comparative example and Example 1 is that step (1) of this comparative example is raw material pretreatment: fresh lemons are selected, cleaned, and cut into slices with a thickness of 5 mm to obtain lemon slices. The remaining steps are the same as in Example 1.

[0118] Test Example 1

[0119] 1.1 Effect of tea powder addition order on the quality of freeze-dried tablets

[0120] Tea-flavored lemon freeze-dried tablets were prepared by two different processes: adding tea powder before pre-freezing (i.e., the tea-flavored lemon freeze-dried tablets prepared by Example 1) or adding tea powder after pre-freezing (i.e., the tea-flavored lemon freeze-dried tablets prepared by Comparative Example 1). The fresh lemon freeze-dried tablets of Comparative Example 2 were used as a control. The three physical and chemical indicators of moisture content, rehydration rate, and VC content of the tea-flavored lemon freeze-dried tablets of Example 1, the tea-flavored lemon freeze-dried tablets of Comparative Example 1, and the fresh lemon freeze-dried tablets of Comparative Example 2 were compared and analyzed.

[0121] Among them, moisture content determination: weigh 10.0g of tea-flavored lemon freeze-dried tablets and place them in a material tray. Use a halogen moisture meter to measure the moisture content. The difference in mass before and after drying the lemon slices at 105°C to a constant weight is the moisture content of the sample.

[0122] Rehydration rate determination: Take one tea-flavored lemon freeze-dried tablet, sample m1, place it in a beaker, add 250 mL of 25°C distilled water, and soak for 60 minutes. Remove and drain the surface and surrounding water, then weigh the tablet, recording it as m2. Perform three parallel experiments. The rehydration rate (R) is calculated as follows: R = (m2 - m1) ÷ m2 × 100%.

[0123] Vitamin C (VC) determination: The ascorbic acid in the sample was determined by 2,6-dichloroindophenol titration method. Three sets of parallel experiments were performed on each sample to obtain the average value.

[0124] Table 1 Results of moisture content, rehydration rate and VC content of different lemon freeze-dried tablets

[0125]

[0126] Moisture content is a key indicator of dried product quality. Fruit and vegetable drying involves using controlled techniques to remove moisture from fruits and vegetables, reducing the water activity to a level that makes it difficult for microorganisms to survive and reproduce, thereby ensuring good shelf life. According to GB / T 23787-2009, "Non-fried Fruit and Vegetable Crisps," the moisture content should be ≤5%. The rehydration rate refers to the recovery of water from a vacuum freeze-dried product before consumption. It is the ratio of the weight of the material after rehydration to the weight before rehydration to the weight of the material after rehydration. The rehydration rate is a key indicator for evaluating freeze-dried product quality.

[0127] The results in Table 1 show that, when the order of tea powder addition was controlled and other factors remained constant, the moisture content of the tea-flavored lemon freeze-dried tablets of Comparative Example 1 was higher than that of the tea-flavored lemon freeze-dried tablets of Example 1. However, there was no significant difference between the tea-flavored lemon freeze-dried tablets of Example 1 and those of fresh lemon freeze-dried tablets, and both tablets met the requirement of ≤5% moisture content in GB / T 23787-2009, "Non-fried Fruit and Vegetable Crisps." The VC content of the tea-flavored lemon freeze-dried tablets of Example 1 and Comparative Example 1 was higher than the rehydration rate and VC content of the fresh lemon freeze-dried tablets, with the tea-flavored lemon freeze-dried tablets of Example 1 having the highest rehydration rate and VC content. Therefore, the moisture content of the tea-flavored lemon freeze-dried tablets of the present invention met the requirement of ≤5% moisture content in GB / T 23787-2009, "Non-fried Fruit and Vegetable Crisps," and the tea-flavored lemon freeze-dried tablets were of high quality.

[0128] 1.2 Effect of slice thickness on the quality of tea-flavored lemon freeze-dried tablets

[0129] Slice thickness significantly impacts the freeze-drying time and quality of the freeze-dried product. To determine the optimal slice thickness, lemon slices of varying thicknesses (3 mm, 4 mm, and 5 mm) were studied. A comparative analysis of the three physical and chemical parameters of moisture content, rehydration rate, and vitamin C content was performed on the tea-flavored lemon freeze-dried tablets of Example 1, Comparative Example 7, and Comparative Example 3. The methods for determining moisture content, rehydration rate, and vitamin C content were consistent with those described in Section 1.1.

[0130] Table 2 Water content, rehydration rate and VC content of lemon freeze-dried slices with different slice thicknesses

[0131] Sample source Slice thickness (mm) Moisture content (%) Rehydration rate (%) VC content (mg / 100g) Comparative Example 3 3 4.77 72.19 256.11 Example 1 4 4.96 72.36 326.84 Comparative Example 7 5 9.58 48.96 347.39

[0132] At the same time, the tea-flavored lemon freeze-dried tablets of Examples 1-2 and the tea-flavored lemon freeze-dried tablets of Comparative Examples 3-4 were photographed. Figures 1 to 4 .

[0133] The results in Table 2 show that the thicker the lemon slices, the greater the moisture content of the dried slices. Within the same 30-min soaking time, the thicker the lemon slices, the smaller the rehydration rate of the dried slices, that is, the weaker the rehydration property. The VC content of the 5 mm thick freeze-dried lemon slices is the highest.

[0134] Depend on Figures 1 to 4 The results showed that freeze-dried lemon slices with a slice thickness of 3 mm were severely wrinkled and easily broken, affecting their appearance and packaging and storage. Tea-flavored freeze-dried lemon slices with a thickness of 4 mm had the best sensory quality.

[0135] In summary, the 4 mm thick tea-flavored lemon freeze-dried sheets prepared in Example 1 and Example 2 have the best quality.

[0136] 1.3 Analysis of water content and rehydration rate of different lemon freeze-dried tablets

[0137] The tea-flavored lemon freeze-dried tablets prepared by the methods of Examples 1 and 2 and the fresh lemon freeze-dried tablets prepared by the method described in Comparative Example 2 were tested for moisture content and rehydration rate. The freeze-dried lemon tablets were tested three times for each treatment. The methods for determining moisture content and rehydration rate were the same as those in Section 1.1.

[0138] Table 3 Moisture content and rehydration rate of different lemon freeze-dried slices

[0139] Sample name Moisture content (%) Rehydration rate (%) Tea-flavored lemon freeze-dried tablets of Example 1 4.96±0.32 80.13±3.11 Tea-flavored lemon freeze-dried tablets of Example 2 4.42±0.29 71.08±2.64 Fresh lemon freeze-dried slices of comparative example 2 4.56±0.21 67.09±2.69

[0140] The results in Table 3 indicate that the moisture content of the fresh lemon freeze-dried tablets of Comparative Example 2 and the tea-flavored lemon freeze-dried tablets prepared by the methods of Examples 1-2 met the requirement of ≤5% for moisture content in GB / T 23787-2009, "Non-fried Fruit and Vegetable Crisps." However, compared with the fresh lemon freeze-dried tablets of Comparative Example 2, the tea-flavored lemon freeze-dried tablets prepared by the methods of Examples 1-2 had a higher rehydration rate.

[0141] 1.4 Determination of the yield of products treated with metal ion cross-linking

[0142] This experiment investigated the effect of metal ion cross-linking treatment on the yield of lemon freeze-dried tablets. The yield of the tea-flavored lemon freeze-dried tablets prepared using Examples 1 and 2 and the tea-flavored lemon freeze-dried tablets prepared using Comparative Examples 5 and 6 was measured, and each tea-flavored lemon freeze-dried tablet was measured three times in parallel.

[0143] The lemon slices were weighed m0 respectively, and then prepared according to the method of Examples 1 to 2 (metal ion cross-linking treatment group). At the same time, the method of Comparative Example 5 or 6 was used as a control (no cross-linking treatment group). The tea-flavored lemon freeze-dried slices were weighed m1 respectively, and the product yield was calculated according to the following formula.

[0144] Output rate = m1 ÷ m0 × 100%.

[0145] Table 4 Results of product yield determination in different treatment groups

[0146]

[0147] The results in Table 4 show that the dry sheet product of Example 1 has a higher yield after metal ion crosslinking treatment compared to Comparative Example 5. Similarly, the dry sheet product of Example 2 has a higher yield after metal ion crosslinking treatment compared to Comparative Example 6.

[0148] 1.5 Determination of VC content in different lemon freeze-dried tablets at different storage times

[0149] Tea-flavored lemon freeze-dried tablets were prepared using the methods of Examples 1 and 2, and fresh lemon freeze-dried tablets were prepared using the method of Comparative Example 2. The VC content of the tea-flavored lemon freeze-dried tablets prepared using the methods of Example 1 and Example 2, and the fresh lemon freeze-dried tablets prepared using the method of Comparative Example 2, was measured using the VC content determination method described in Section 1.1 after storage for 82 days. Samples were randomly tested every three days during storage, with three replicates performed for each sample, and the average value was taken. The VC content preservation rate on day 82 was calculated: preservation rate = VC content on day 82 / VC content on day 1 × 100%.

[0150] At the same time, the tea polyphenol content of the tea-flavored lemon freeze-dried tablets prepared by the methods of Example 1 and Example 2 and the fresh lemon freeze-dried tablets prepared by the method of Comparative Example 2 after storage for 82 days were respectively tested, and the method for determining the tea polyphenol content was carried out with reference to the "GB / T8313-2018 Detection Method for Tea Polyphenols and Catechins in Tea".

[0151] Table 5 Results of VC content, preservation rate and tea polyphenol content of different lemon freeze-dried tablets

[0152]

[0153]

[0154] Note: “-” means no or almost undetectable.

[0155] As shown in Table 5, the preservation rate of VC in different lemon freeze-dried tablets has a significant impact. Among them, the preservation rate of lemon freeze-dried tablets coated with tea powder is the highest, reaching 64.10%, followed by lemon freeze-dried tablets for brewing tea, and the fresh lemon freeze-dried tablets have the lowest preservation rate, which is 44.32%.

[0156] Depend on Figure 5As can be seen, the overall VC content curves for the three lemon freeze-dried tablets vacuum-packed in aluminum foil bags all showed a downward trend with extended storage time: tea powder-coated lemon freeze-dried tablets > pure lemon freeze-dried tablets > tea-infused lemon freeze-dried tablets. During the first 34 days of storage, the VC content of both tea-infused and fresh lemon freeze-dried tablets showed a stable and insignificant trend, with minimal fluctuations, and a high VC retention rate. From the 34th to the 40th day of storage, the VC content of both decreased significantly; after the 40th day, the decline in VC content leveled off. Meanwhile, the VC content of the Dancong tea powder lemon freeze-dried tablets showed a stable trend, with minimal fluctuations, and a high VC retention rate during the first 58 days of storage. From the 58th to the 64th day of storage, the VC content decreased significantly; after 64 days of storage, the decline in VC content leveled off. The tea powder lemon freeze-dried tablets had the highest VC content and VC retention rate among the three samples, and the significant downward trend in VC content occurred one month later than the other two samples. This indicates that coating the surface with tea powder can effectively delay the decline of VC content in freeze-dried lemon tablets.

[0157] 1.6 Color difference analysis of different lemon freeze-dried tablets

[0158] Color is one of the important indicators of dried fruit and vegetable products. Freeze-dried lemon slices will undergo physical and chemical changes during storage, among which color change of the slices is a relatively common phenomenon.

[0159] The tea-flavored lemon freeze-dried tablets (also known as lemon freeze-dried tablets with added Dancong tea powder or Dancong tea powder lemon freeze-dried tablets) were prepared using the method of Example 1 and Example 2. At the same time, fresh lemon freeze-dried tablets were prepared using the method of Comparative Example 2. The color difference analysis of each lemon freeze-dried tablet was performed using a colorimeter during the storage period of 3 months, and a white standard color plate (L*=96.50, a*=-0.27, b*=0.40) was used as the standard background for color measurement.

[0160] in,

[0161] Wherein: ΔL*=L*(sample)-L*; Δa*=a*(sample)-a*; Δb*=b*(sample)-b*.

[0162] Figure 6 、 Figure 7 、 Figure 8 and Figure 9The results showed that the color parameters L* and b* values ​​of the freeze-dried lemon tablets containing Dancong tea powder and Dancong tea decoction decreased with storage time, while the a* and ΔE* values ​​increased, indicating that the brightness and yellowness of the freeze-dried lemon tablets with Dancong tea flavor decreased, while the redness increased. The color parameters a* and ΔE* values ​​of the freeze-dried lemon tablets in the control group also increased with storage time, while the L* and b* values ​​decreased, indicating that the redness and yellowness increased, while the brightness decreased.

[0163] The a* values ​​of all three samples increased with extended storage time, indicating a shift in color toward red. The order of redness at the initial stage of storage was: control group fresh lemon freeze-dried slices < single-bush tea powder lemon freeze-dried slices < single-bush tea soup lemon freeze-dried slices. The control group fresh lemon freeze-dried slices showed the fastest change, followed by single-bush tea soup slices, and single-bush tea powder slices were relatively stable. Within 30 days of storage, the a* values ​​of all three samples showed slow and steady changes. After 30 days, the single-bush tea powder and tea soup lemon slices showed relatively steady changes. However, within 30 to 50 days of storage, the a* value of the control group pure lemon freeze-dried slices showed a rapid change, and within 50 to 90 days, the change became more gradual.

[0164] The L* values ​​of all three samples decreased with extended storage, indicating that the color of each dried tablet shifted toward black. The brightness ranking at the beginning of storage was: Dancong tea powder lemon freeze-dried tablets < Dancong tea decoction lemon freeze-dried tablets < control group pure lemon freeze-dried tablets. There were no significant differences in the changing trends among the three samples.

[0165] The b* values ​​of the freeze-dried tablets containing both Dancong tea and Dancong tea powder decreased with storage time, with the change in the Dancong tea soup tablets showing a faster change than that of the Dancong tea powder tablets. In contrast, the b* value of the freeze-dried tablets containing pure lemon in the control group increased with storage time, indicating degradation of the yellow pigment in the tea-flavored lemon freeze-dried tablets. The yellowness ranking at the initial stage of storage was: freeze-dried tablets containing fresh lemon in the control group < freeze-dried tablets containing Dancong tea soup and lemon < freeze-dried tablets containing Dancong tea soup and lemon.

[0166] The ΔE* values ​​of all three products increased with extended storage time, with significant differences. The control group's fresh lemon freeze-dried tablets showed the fastest and greatest increase in total color difference, followed by the Dancong tea decoction lemon freeze-dried tablets. The Dancong tea powder lemon freeze-dried tablets showed the slowest and smallest change in total color difference compared to the other three.

[0167] Comparison of the three color parameters revealed that the freeze-dried lemon slices containing Dancong tea powder exhibited the least color change during the three-month storage period, followed by the freeze-dried lemon slices containing Dancong tea decoction. The control group, consisting of freeze-dried lemon slices, exhibited the most significant color change. This suggests that lemon slices coated with tea powder or dried after being soaked in tea decoction retained their color better. This may be due to the fact that the tea substances in the solution penetrated the lemon tissue after the fresh lemon slices were immersed in tea decoction, or that the tea powder coating created an additional protective film on the surface of the dried lemon slices, allowing the tea substances in the tea powder to penetrate the lemon tissue, thereby protecting the color. Among the four color parameters, the a* value showed the greatest change trend among the three samples, indicating a significant change in the redness of the dried slices, indicating a certain degree of browning during the three-month storage period. The color parameters indicate that the color of the dried slices changed slowly during the first month of storage, but changed significantly after one month. Furthermore, the color of the dried lemon slices coated with tea powder or soaked in tea decoction protected their color.

[0168] 1.7 Browning analysis of different lemon freeze-dried slices

[0169] Browning is a key factor affecting the quality and nutritional value of fruits and vegetables. It is the process by which phenolic substances are oxidized by enzymes to form quinones, which in turn form melanin, causing the browning of fruits and vegetables. The degree of browning can reflect the degree of browning of fruits and vegetables.

[0170] Tea-flavored lemon freeze-dried tablets (also known as Dancong decoction lemon freeze-dried tablets) were prepared using the methods of Example 1 (also known as Dancong powder-added lemon freeze-dried tablets) and Example 2, and the browning degree of each lemon freeze-dried tablet was tested during storage for 2 months.

[0171] Browning degree determination:

[0172] The extinction value method was used: each lemon freeze-dried piece was ground with distilled water at a ratio of 1:100 (weight), and the mixture was evenly ground in an ice bath. The mixture was centrifuged at 40 r / min for 10 min, and then placed at 25°C for 30 min. The supernatant was taken and the A at 420 nm was measured. 420 Absorbance value, expressed as 10×A 420 Indicates the degree of browning. Samples were tested every three days for two months.

[0173] Figure 10 The results showed that the browning degree of lemon freeze-dried tablets from Dancong powder was lower than that from Dancong soup.

[0174] 1.8 Sensory evaluation

[0175] The tea-flavored lemon freeze-dried tablets prepared in Example 2 were mixed with 60° C. water at a mass volume ratio of 1 g:150 mL and brewed for 4, 6, and 8 minutes, respectively. The resulting brewed tea-flavored lemon water was subjected to sensory evaluation.

[0176] The tea-flavored lemon freeze-dried tablets prepared in Example 2 were mixed with 70° C. water at a mass volume ratio of 1 g:150 mL and brewed for 4, 6, and 8 minutes, respectively. The resulting brewed tea-flavored lemon water was subjected to sensory evaluation.

[0177] The tea-flavored lemon freeze-dried tablets prepared in Example 2 were mixed with 80° C. water at a mass volume ratio of 1 g:150 mL and brewed for 4, 6, and 8 minutes, respectively. The resulting brewed tea-flavored lemonades were subjected to sensory evaluation.

[0178] The tea-flavored lemon freeze-dried tablets prepared in Example 2 were mixed with 60° C. water at a mass volume ratio of 1 g:200 mL and brewed for 4, 6, and 8 minutes, respectively. The resulting brewed tea-flavored lemonades were subjected to sensory evaluation.

[0179] The tea-flavored lemon freeze-dried tablets prepared in Example 2 were mixed with 70° C. water at a mass volume ratio of 1 g:200 mL and brewed for 4, 6, and 8 minutes, and the resulting brewed tea-flavored lemonades were subjected to sensory evaluation.

[0180] The tea-flavored lemon freeze-dried tablets prepared in Example 2 were mixed with 80° C. water at a mass volume ratio of 1 g:200 mL and brewed for 4, 6, and 8 minutes, respectively. The resulting brewed tea-flavored lemon water was subjected to sensory evaluation.

[0181] The tea-flavored lemon freeze-dried tablets prepared in Example 2 were mixed with 60° C. water at a mass volume ratio of 1 g:250 mL and brewed for 4, 6, and 8 minutes, respectively. The resulting brewed tea-flavored lemon water was subjected to sensory evaluation.

[0182] The tea-flavored lemon freeze-dried tablets prepared in Example 1 were mixed with 70° C. water at a mass volume ratio of 1 g:250 mL and brewed for 4, 6, and 8 minutes, and the resulting brewed tea-flavored lemonades were subjected to sensory evaluation.

[0183] The tea-flavored lemon freeze-dried tablets prepared in Example 2 were mixed with 80° C. water at a mass volume ratio of 1 g:250 mL and brewed for 4, 6, and 8 minutes, respectively. The resulting brewed tea-flavored lemon water was subjected to sensory evaluation.

[0184] Sensory Evaluation: A sensory evaluation panel of 10 trained professionals was selected to evaluate the frozen-dried Dancong tea-flavored lemon slices under varying ratios of water to lemon slice weight, water temperature, and soaking time. Based on the sensory evaluation criteria set forth in GB / T 14487-2017 Tea Sensory Evaluation Terminology, GB / T 18797-2012 Basic Conditions for Tea Sensory Evaluation Rooms, and GB / T 23776-2018 Tea Sensory Evaluation Methods, the panel evaluated the appearance of the frozen-dried Dancong tea-flavored lemon slices, the color of the tea after soaking, the aroma, and the flavor and taste of the tea. The specific sensory evaluation criteria are shown in Table 6.

[0185] Table 6 Sensory quality evaluation standard of Dancong tea flavored lemon freeze-dried tablets

[0186]

[0187] The results of the sensory evaluation are shown in Table 7.

[0188] Table 7 Sensory quality evaluation results of Dancong tea flavored lemon freeze-dried tablets brewed in different processing methods

[0189]

[0190]

[0191] The results in Table 7 show that when brewing Dancong tea soup lemon freeze-dried tablets, the optimal dry tablets to water weight ratio is 1:150, the optimal brewing time is 8 minutes, and the optimal brewing water temperature is 80℃.

[0192] Table 8 Sensory quality evaluation results of Dancong tea powder lemon freeze-dried slices brewed in different processing methods

[0193]

[0194]

[0195] The results in Table 8 show that when brewing Dancong tea powder lemon freeze-dried tablets, the optimal dry tablets to water weight ratio is 1:200, the optimal brewing time is 8 minutes, and the optimal brewing water temperature is 80°C.

[0196] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing tea-flavored fruit freeze-dried tablets, characterized in that: The following steps are involved: Slicing the fruit to obtain fruit slices, and then subjecting the fruit slices to tea flavoring to obtain tea-flavored fruit slices; The tea flavoring treatment includes a tea powder coating treatment method or a tea soup soaking treatment method; The tea powder coating processing method comprises the following steps: Crush the tea leaves, sieve them, and apply the obtained tea powder on the surface of the fruit slices; The tea soaking soup processing method comprises the following steps: The tea leaves are soaked in boiling water, filtered, and the collected extract is soaked with fruit slices.

2. The preparation method according to claim 1, characterized in that After obtaining the tea-flavored fruit slices, the following steps are also included: Freezing the tea-flavored fruit slices to obtain frozen fruit slices; The frozen fruit slices are impregnated with a seaweed polysaccharide solution to obtain impregnated tea-flavored fruit slices; cross-linking the soaked tea-flavored fruit slices with a metal ion solution to obtain cross-linked tea-flavored fruit slices; The cross-linked tea-flavored fruit slices are frozen and then vacuum-freeze-dried to obtain tea-flavored fruit freeze-dried slices.

3. The preparation method according to claim 1, characterized in that The thickness of the slices is 3.5-4.5 mm; the fruit is lemon; and the tea is oolong tea.

4. The preparation method according to claim 1, characterized in that The mesh size of the sieving is 180-240 meshes; the number of extractions is 1-3 times, and the time for each extraction is 20-30 minutes; the mass volume ratio of the tea leaves to boiling water is 1g: (9-15)mL; and the volume mass ratio of the extract to the fruit slices is 150-200mL: 10-15g.

5. The preparation method according to claim 2, characterized in that The freezing temperature is -25 to -18°C, and the freezing time is 5 to 10 minutes.

6. The preparation method according to claim 2, characterized in that The seaweed polysaccharide solution comprises sodium alginate and gellan gum, wherein the mass ratio of the sodium alginate to the gellan gum is (1-3):(5-8); the volume mass ratio of the seaweed polysaccharide solution to the frozen fruit slices is 100-150 mL:5-10 g; the immersion treatment time is 30-60 s; and during the immersion treatment, the temperature of the seaweed polysaccharide solution is 35-45° C.

7. The preparation method according to claim 2, characterized in that The metal ion solution includes a CaCl2 solution or a ZnCl2 solution; the mass volume ratio of the soaked tea-flavored fruit slices to the metal ion solution is 5-10g:120-200mL; the cross-linking temperature is 25-40°C, and the cross-linking time is 0.5-1min.

8. The preparation method according to claim 7, characterized in that The mass volume percentage of the metal ion solution is 1 to 3%.

9. The preparation method according to claim 2, characterized in that The freezing temperature is -50°C to -80°C, and the freezing time is 6 to 8 hours. The vacuum freeze-drying method is segmented vacuum drying: the shelf temperature in the vacuum sublimation drying stage is 35 to 45°C and the vacuum degree is 50 to 150 Pa; the shelf temperature in the vacuum desorption drying stage is 45 to 55°C and the vacuum degree is 40 to 100 Pa. During the entire vacuum drying period, the cold trap temperature is maintained at -70°C to -50°C.

10. Tea-flavored fruit freeze-dried tablets prepared according to the preparation method according to any one of claims 1 to 9.

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