Integrated freeze-dried coffee product and preparation method thereof

Abstract

The invention discloses an integrated freeze-dried coffee product and a preparation method thereof, and relates to the technical field of food processing. The invention relates to an integrated coffee freeze-dried product manufacturing method. The method comprises the following steps: baking selected coffee beans, culturing the coffee beans, and extracting the coffee beans until coffee liquid is obtained; uniformly adding a pore regulator into the coffee liquid and filling the coffee liquid into a freeze-drying container; carrying out top-speed pre-freezing on the freeze-drying container filled with the coffee liquid in liquid nitrogen; putting the freeze-drying container subjected to top-speed pre-freezing into a freezing chamber of minus 35 DEG C for freezing and temporary storage; and taking out the freeze-drying container from the-35 DEG C freezing chamber, and transferring into a freeze-drying machine for freeze-drying treatment. Through a series of process innovation optimization, the prepared freeze-dried coffee product is uniform in internal pore structure, instantly dissolved under the condition of full water temperature, high in surface overall texture hardness and not prone to breakage in the transportation and storage stages, and the maximum flavor is reserved on the basis of the three-dimensional shape.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, and in particular to an integrated freeze-dried coffee product and a production method thereof. Background Art

[0002] Freeze-dried coffee products are a type of coffee product made through freeze-drying technology; the production process generally involves first freezing the coffee liquid into a solid, and then drying it under low temperature and vacuum conditions, so that the water in the coffee liquid sublimates directly from a solid state to a gas state, thereby obtaining a block-shaped coffee product.

[0003] During the production process of freeze-dried coffee products, the water in the coffee liquid directly sublimates from solid to gas. The space originally occupied by the ice crystals will be left behind to form pores. As the ice crystals continue to sublimate, these pores gradually connect to form a porous structure inside the coffee block.

[0004] The presence of pores in freeze-dried coffee products has an important impact on the quality and taste of coffee. On the one hand, it increases the surface area of ​​the coffee, allowing it to dissolve in water more quickly and facilitate brewing; on the other hand, it also helps to maintain the aroma and flavor of the coffee, allowing them to be better released during brewing.

[0005] At present, the inventors have found in long-term practical research that the conventional coffee freeze-dried product preparation process has the following technical problems in the preparation of coffee freeze-dried products: (1) In conventional freeze-drying processes, the pre-freezing operation of coffee freeze-dried products is usually carried out at -35°C, resulting in the pore diameter of the formed coffee freeze-dried products ranging from 400 to 600 μm, leading to large differences in freeze-dried porosity, uneven pores, and larger pores; (2) In order to maximize the contact area with water, the internal voids of the coffee freeze-dried products prepared by conventional freeze-drying process are mainly macroporous and porous structures. However, if the pores are too large, they may cause local collapse, resulting in uneven dissolution and reduced dissolution rate. (3) At the same time, because the internal voids of freeze-dried coffee products are mainly large-pore and porous structures, the skeleton structure of freeze-dried coffee products is loose and easy to break during transportation and storage, which increases the product failure rate.

[0006] Therefore, how to solve the above technical problems is a technical problem currently faced by general technicians in this field.

[0007] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0008] In view of the above technical problems, the embodiments of the present invention provide an integrated freeze-dried coffee product and a production method thereof to solve the problems raised in the above background technology.

[0009] A method for producing an integrated freeze-dried coffee product comprises the following steps: The selected coffee beans are roasted, aged, and extracted in sequence until coffee liquid is obtained; Evenly adding the pore adjusting agent into the coffee liquid and filling it into a freeze-drying container; The freeze-dried container containing the coffee liquid is rapidly pre-frozen in liquid nitrogen (-70℃~-80℃); Place the extremely fast pre-frozen freeze-dried container in a -35°C freezer for temporary storage; The freeze-drying container was taken out from the -35°C freezer and transferred into a freeze dryer for freeze drying.

[0010] It should be noted that the existing technologies mostly adopt the step-by-step process of "grinding, packaging and freeze-drying", in which the coffee liquid is exposed to the air for ≥30 minutes before filling, resulting in a loss rate of volatile aroma components (such as ethyl acetate) of >15% (GCMS data).

[0011] The present invention pioneered the integrated "extraction-filling-freeze-drying" mode, which shortens the exposure time of coffee liquid before filling through integrated filling, reduces the flavor loss path, and reduces the loss rate of volatile aroma components.

[0012] Preferably, the selected coffee beans are sequentially roasted, aged, and extracted until coffee liquid is obtained; The coffee bean selection operation includes removing defective coffee beans and blending coffee beans of different flavors from different producing areas according to the product flavor requirements.

[0013] Preferably, the selected coffee beans are sequentially roasted, aged, and extracted until coffee liquid is obtained; The coffee beans are extracted using a flash extraction machine at an extraction temperature of 85°C~98°C; the extracted coffee liquid flows through a tubular heat exchanger for rapid cooling.

[0014] It should be noted that, during the extraction process of coffee liquid, the traditional cooling process generally adopts natural cooling at room temperature, and it takes ≥30 minutes for the coffee liquid to cool to 30°C, resulting in a serious loss of key flavor substances. The present invention adopts a tubular heat exchanger for instantaneous heat exchange, and 4°C cooling water cools the coffee liquid to ≤25°C within 10 minutes, which can effectively avoid the excessive volatilization of heat-sensitive aroma components in coffee and the degradation of flavor substances, thereby retaining the original flavor and mellowness of coffee beans.

[0015] Preferably, in the step of uniformly adding the pore adjusting agent into the coffee liquid and filling the coffee liquid into a freeze-drying container, the pore adjusting agent is oligofructose.

[0016] Preferably, the mass ratio of oligofructose added to the coffee liquid to the coffee liquid is 2:100.

[0017] Preferably, the material of the freeze-drying container is PP material, and the specific shape can be designed as a small round can structure; the oxygen permeability of the PP material is less than 0.5 cm³ / m²·da.

[0018] The invention adopts a small round can made of PP material with low oxygen permeability as a freeze-drying container, omitting the subpackaging step and directly injecting inert gas to lock freshness and seal for final factory packaging, thereby increasing the flavor lock-in period.

[0019] Preferably, the step of taking out the freeze-drying container from the -35°C freezer and transferring it to a freeze dryer for freeze-drying; The freeze-drying conditions included: the starting temperature of sublimation drying was -25°C, the end temperature of primary sublimation was 10°C, the starting temperature of secondary drying was 10°C, and the end temperature of drying was 45°C.

[0020] Preferably, the total duration of the freeze-drying process is controlled within 48 hours, and the vacuum degree is controlled below 30 Pa.

[0021] The integrated freeze-dried coffee product is produced by the integrated freeze-dried coffee product production method described above.

[0022] Preferably, the diameter of the internal pores of the freeze-dried coffee is 100±10 μm; and the diameter of the dry matter crystals is ≤10 μm.

[0023] An integrated freeze-dried coffee product and a production method thereof provided by an embodiment of the present invention have the following beneficial effects: 1. The present invention uses liquid nitrogen for rapid pre-freezing, and then cooperates with a gradient freeze-drying process to make the pore diameter of the freeze-dried coffee ≤100 μm, thereby forming a dense pore structure inside the freeze-dried coffee, improving the porosity uniformity and reducing the porosity difference; 2. The present invention uses oligofructose as a regulator of the internal pores of freeze-dried coffee. Oligofructose is evenly added to the coffee liquid. During the pre-freezing and freeze-drying process, oligofructose and coffee particles together constitute the coffee skeleton structure, and the oligofructose is filled in the pores between the coffee particles, making the internal pores of the freeze-dried coffee more dense and uniform, thereby improving the product structure hardness and dissolution rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an electron microscopic image of the interior of freeze-dried coffee that has not been pre-frozen by liquid nitrogen in Example 1 of the present invention; Figure 2 This is an electron microscopic image of the interior of freeze-dried coffee that has been rapidly pre-frozen with liquid nitrogen in Example 2 of the present invention; Figure 3 This is an electron micrograph of the interior of freeze-dried coffee that has been rapidly pre-frozen with liquid nitrogen and added with oligofructose in Example 3 of the present invention. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0026] In view of the above technical problems, the embodiments of the present invention provide an integrated freeze-dried coffee product and a production method thereof to solve the problems raised in the above background technology.

[0027] 1. Preparation of Freeze-dried Coffee Embodiment 1: According to the product requirements of freeze-dried coffee, coffee beans that meet the requirements are selected. After the coffee beans are selected, they are roasted and the beans are aged for 10 days.

[0028] After the coffee beans are grown, the coffee liquid is extracted using an Italian-style flash coffee production line with an extraction temperature of 85℃-98℃.

[0029] After the coffee liquid is extracted, it is cooled and placed. The extracted coffee liquid flows through a tubular heat exchanger and undergoes efficient heat exchange with a cooling water flow at 4°C within 30 seconds, effectively cooling the temperature to ≤25 degrees in a short time.

[0030] According to the product weight, the coffee liquid is directly poured into the cup of the freeze-drying container, with the filling amount being 18 g; the freeze-drying container encapsulated with the coffee liquid is placed in a -35°C freezer.

[0031] After the pre-frozen product is frozen solid, it is transferred to a freeze dryer with a minimum starting temperature of -25°C, a primary sublimation endpoint temperature of 10°C, a secondary drying and analysis starting temperature of 10°C, a drying endpoint temperature of 45°C, a total drying time of 48 hours, and a vacuum degree of less than 30Pa for sublimation drying and crystallization.

[0032] After leaving the warehouse, the internal structure of the freeze-dried product was observed by scanning electron microscopy (SEM), and it was found that the pores were large, 500±200μm, and the fracture phenomenon was serious. Figure 1 .

[0033] Embodiment 2: According to the product requirements of freeze-dried coffee, coffee beans that meet the requirements are selected. After the coffee beans are selected, they are roasted and the beans are aged for 10 days.

[0034] After the coffee beans are grown, the coffee liquid is extracted using an Italian-style flash coffee production line with an extraction temperature of 85℃-98℃.

[0035] After the coffee liquid is extracted, it is cooled and placed. The extracted coffee liquid flows through a tubular heat exchanger and undergoes efficient heat exchange with a cooling water flow at 4°C within 30 seconds, effectively cooling the temperature to ≤25 degrees in a short time.

[0036] According to the product weight, the coffee liquid is directly poured into the cup of the freeze-drying container, with a filling volume of 18g; the freeze-drying container encapsulated with the coffee liquid is rapidly frozen through a -70℃ liquid nitrogen tunnel and then placed in a -35℃ freezer.

[0037] After the pre-frozen product is frozen solid, it is transferred to a freeze dryer with a minimum starting temperature of -25°C, a primary sublimation endpoint temperature of 10°C, a secondary drying and analysis starting temperature of 10°C, a drying endpoint temperature of 45°C, a total drying time of 48 hours, and a vacuum degree of less than 30Pa for sublimation drying and crystallization.

[0038] After leaving the warehouse, the internal structure of the freeze-dried product was observed by scanning electron microscopy (SEM), and it was found that the internal pores were significantly reduced compared with the internal pores of the freeze-dried product that was not subjected to liquid nitrogen quick freezing in Example 1, which was 200±50μm, and the fracture phenomenon was weakened; and SEM observation showed that the crystal diameter of the dry matter in the freeze-dried product was ≤20μm; specifically, Figure 2 .

[0039] Embodiment 3: According to the product requirements of freeze-dried coffee, coffee beans that meet the requirements are selected. After the coffee beans are selected, they are roasted and the beans are aged for 10 days.

[0040] After the coffee beans are grown, the coffee liquid is extracted using an Italian-style flash coffee production line with an extraction temperature of 85℃-98℃.

[0041] After the coffee liquid is extracted, it is cooled and placed. The extracted coffee liquid flows through a tubular heat exchanger and undergoes efficient heat exchange with a cooling water flow at 4°C within 30 seconds, effectively cooling the temperature to ≤25 degrees in a short time.

[0042] Oligofructose was evenly added into the coffee liquid as a pore adjusting agent, and the mass ratio of the oligofructose added into the coffee liquid to the coffee liquid was 2:100; According to the weight of the product, the coffee liquid mixed with oligofructose is directly poured into the freeze-drying container, with the filling amount of 18g; the freeze-drying container encapsulated with the coffee liquid is rapidly frozen through a -70°C liquid nitrogen tunnel and then placed in a -35°C freezer.

[0043] After the pre-frozen product is frozen solid, it is transferred to a freeze dryer with a minimum starting temperature of -25°C, a primary sublimation endpoint temperature of 10°C, a secondary drying and analysis starting temperature of 10°C, a drying endpoint temperature of 45°C, a total drying time of 48 hours, and a vacuum degree of less than 30Pa for sublimation drying and crystallization.

[0044] After leaving the warehouse, the internal structure of the freeze-dried product was observed by scanning electron microscopy (SEM), and it was found that the internal pores were significantly reduced compared with the internal pores of the freeze-dried product that was quick-frozen by liquid nitrogen in Example 2, which was 100±10 μm, and the fracture phenomenon was the weakest; and SEM observation showed that the crystal diameter of the dry matter in the freeze-dried product was ≤10 μm; specifically, Figure 3 .

[0045] 2. Comparison of freeze-dried coffee performance 1. Overall hardness: The coffee freeze-dried product with pore adjusting agent added and passed through liquid nitrogen tunnel > the coffee freeze-dried product with liquid nitrogen tunnel > the coffee freeze-dried product without liquid nitrogen tunnel. The hardness of the coffee freeze-dried product with pore adjusting agent added and quick-frozen through liquid nitrogen tunnel is significantly improved. 2. The freeze-dried coffee products in the three groups of examples were observed under an electron microscope with the same magnification. Among them, the porosity of the freeze-dried coffee products prepared in Example 2 and Example 3 was slightly different; however, the porosity of the freeze-dried coffee product prepared in Example 3 was significantly reduced, and the arrangement was neat, the internal pores were more uniform, and the pores were 100±10μm; Under an electron microscope, no oligofructose residue was observed inside the freeze-dried coffee product prepared in Example 3. It is speculated that oligofructose may have been evenly distributed in the coffee liquid as a pore regulator; during the pre-freezing and freeze-drying process, oligofructose and coffee particles together formed a skeleton structure, filling the pores between the coffee particles, making the internal pores of the freeze-dried coffee product denser and more uniform.

[0046] 3. In terms of flavor, there is no obvious difference between the freeze-dried coffee products in the three groups of examples, indicating that the freeze-dried coffee products prepared by the preparation processes of Example 2 and Example 3 have achieved maximum flavor retention on the basis of having a three-dimensional form; It should be noted that during the flavor inspection process, in order to ensure the stability of the flavor of each can of coffee, a cupping test will be conducted every 4 hours after the machine is extracted to check the flavor. The specific data is shown in Table 1 below.

[0047] Table 1 Total duration Water content Freeze drying rate Sensory evaluation Demolding effect Dissolution rate Overall hardness Dissolution rate Example 1 48h 1.35% 98.90% excellent excellent - Weaker 10-15 seconds Example 2 48h 2.12% 98.40% excellent excellent excellent normal 5-7 seconds Example 3 48h 2.23% 99% excellent excellent excellent Strong 3-5 seconds The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made to the technical solutions of the present invention by ordinary technicians in the field, and equivalent changes or modifications made based on the spirit of the present invention, should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing an integrated freeze-dried coffee product, characterized in that: The following steps are involved: The selected coffee beans are roasted, aged, and extracted in sequence until coffee liquid is obtained; Evenly adding the pore adjusting agent into the coffee liquid and filling it into a freeze-drying container; The freeze-drying container encapsulating the coffee liquid is rapidly pre-frozen in liquid nitrogen; Place the extremely fast pre-frozen freeze-dried container in a -35°C freezer for temporary storage; The freeze-drying container was taken out from the -35°C freezer and transferred into a freeze dryer for freeze drying.

2. The method for producing an integrated freeze-dried coffee product according to claim 1, characterized in that: The step of roasting, curing and extracting the selected coffee beans in sequence until coffee liquid is obtained; The coffee bean selection operation includes removing defective coffee beans and blending coffee beans of different flavors from different producing areas according to the product flavor requirements.

3. The method for producing an integrated freeze-dried coffee product according to claim 1, characterized in that: The step of roasting, curing and extracting the selected coffee beans in sequence until coffee liquid is obtained; The coffee beans are extracted using a flash extraction machine at an extraction temperature of 85°C~98°C; the extracted coffee liquid flows through a tubular heat exchanger for rapid cooling.

4. The method for producing an integrated freeze-dried coffee product according to claim 1, characterized in that: In the step of uniformly adding the pore adjusting agent into the coffee liquid and filling the coffee liquid into a freeze-drying container, the pore adjusting agent is oligofructose.

5. The method for producing an integrated freeze-dried coffee product according to claim 1, characterized in that: The mass ratio of oligofructose added to the coffee liquid to the coffee liquid is 2:

100.

6. The method for producing an integrated freeze-dried coffee product according to claim 1, characterized in that: The material of the freeze-drying container is PP material; the oxygen permeability of PP material is less than 0.5 cm³ / m²·da.

7. The method for producing an integrated freeze-dried coffee product according to claim 1, characterized in that: The step of taking out the freeze-drying container from the -35°C freezer and transferring it into a freeze dryer for freeze-drying; The freeze-drying conditions included: the starting temperature of sublimation drying was -25°C, the end temperature of primary sublimation was 10°C, the starting temperature of secondary drying was 10°C, and the end temperature of drying was 45°C.

8. The method for producing an integrated freeze-dried coffee product according to claim 7, characterized in that: The total duration of the freeze-drying process is controlled within 48 hours, and the vacuum degree is controlled below 30Pa.

9. Integrated freeze-dried coffee product, characterized in that: The integrated freeze-dried coffee product is produced by the production method of any one of claims 1 to 8.

10. The integrated freeze-dried coffee product according to claim 9, characterized in that: The internal pore diameter of the freeze-dried coffee product is 100±10μm.

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