Filtration method without high temperature sterilization, coffee concentrate preparation process and supply system based thereon

Abstract

The application discloses a high-temperature sterilization-free filtering method and a coffee concentrate preparation process based on the same, and belongs to the technical field of food processing. The coffee concentrate preparation process comprises the following steps: coffee green bean pretreatment; coffee green bean roasting; coffee bean grinding to a specific particle size distribution; 5-7 days of powder aging and exhaust in a nitrogen atmosphere; 9bar or so high-pressure extraction to obtain coffee concentrate raw solution; and coarse filtration through 100 and 400, and then fine filtration through a ceramic membrane system with a pore size of 200-500nm to obtain the coffee concentrate. The application realizes physical sterilization without any heat treatment by specific grinding particle size control, pre-coarse filtration protection and accurate selection of the ceramic membrane pore size, and prepares the concentrated coffee liquid which is safer in low microorganisms and better in flavor than the traditional UHT sterilized coffee concentrate.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a high-temperature sterilization-free filtration method, a coffee concentrate preparation process based thereon, and a supply system. Background Technology

[0002] As one of the world's most consumed beverages, coffee continues to expand its market size. With consumption upgrades and the popularization of specialty coffee culture, consumers have increasingly higher requirements for coffee quality, not only seeking convenient ways to drink it but also placing almost demanding requirements on the flavor, aroma, and taste. Currently, ready-to-drink coffee concentrate products on the market (including room temperature concentrate and refrigerated concentrate) generally suffer from the following core pain points, which seriously restrict the improvement of coffee concentrate product quality and market expansion.

[0003] I. Severe damage to flavor Traditional coffee manufacturing processes, in order to meet the requirements of a long shelf life, generally employ heat treatment processes such as pasteurization (usually 72-85℃, 15-30 minutes) or UHT (usually 135-150℃, 2-8 seconds). Coffee, as a complex natural beverage, has highly volatile aromatic substances and contains abundant oils and proteins. High-temperature processing can lead to a series of negative effects: First, oil oxidation. Coffee oils contain a large amount of unsaturated fatty acids, which are highly susceptible to oxidation under high temperatures, producing oxidation products such as aldehydes and ketones, resulting in an unpleasant rancid taste.

[0004] Second, protein denaturation. The proteins in coffee denature and coagulate at high temperatures, which not only changes the texture and taste of the coffee, but also causes excessive Maillard reactions with sugars, producing burnt and overcooked flavors, causing the coffee to lose its freshness and complexity.

[0005] Third, the loss of aromatic substances due to volatilization. Volatile compounds in coffee, such as aldehydes, ketones, esters, and thiols, will be lost in large quantities during the high-temperature sterilization process, resulting in a weak aroma and monotonous flavor in the finished coffee liquid, completely losing the freshness and complexity that freshly brewed coffee should have.

[0006] Fourth, it produces a sour and astringent taste. High temperatures also cause acidic substances in coffee, such as chlorogenic acid, to decompose and transform, producing more bitter substances such as quinic acid, giving the coffee an unpleasant sour and astringent taste.

[0007] II. Insufficient filtration accuracy Traditional coffee filtration processes typically employ centrifugation or filtration using ordinary filter cloths. Centrifuges have limited effectiveness in removing fine coffee powder, colloidal substances, and suspended particles; ordinary filter cloths, with pore sizes usually between 10-50 μm, can only intercept larger particles and cannot effectively remove micron-sized or smaller fine suspended matter. This results in a large number of microorganisms (including bacteria, yeast, and mold) and fine suspended particles remaining in the coffee liquid. These microorganisms multiply rapidly during subsequent storage, leading to product spoilage. Therefore, traditional processes rely on high-temperature sterilization after filtration to kill microorganisms and extend shelf life; however, high-temperature sterilization reduces coffee flavor, a contradiction that has long plagued the coffee preparation industry.

[0008] III. Limitations of Cold Extraction Process Existing technologies also include cold brew techniques for preparing coffee. Cold brew typically involves steeping coffee grounds at room temperature or low temperature (4-25°C) under normal pressure for an extended period (12-24 hours) to extract flavor compounds. While cold brew avoids the damage caused by high temperatures, its flavor profile differs significantly from high-pressure extraction (such as espresso). Due to its low pressure, low temperature, and long steeping time, cold brew primarily extracts small-molecule flavor compounds and soluble sugars, while failing to adequately extract oils, gums, and some aromatic compounds that require higher pressure. Therefore, cold brew coffee often lacks body, has a thin mouthfeel, and lacks the richness and complexity characteristic of high-pressure extraction; its production cycle is also long. The 12-24 hour steeping time required for cold brew results in extremely low production efficiency, making it unsuitable for large-scale industrial production.

[0009] Third, microbial control is difficult. Prolonged immersion at room temperature provides ample time and suitable conditions for microbial growth. Even if cold sterilization technologies such as HPP are subsequently used, an excessively high initial microbial population can affect the microbial safety of the final product.

[0010] In addition, although existing HPP cold brew coffee products use ultra-high pressure cold sterilization technology, their basic process is still cold brewing rather than high pressure extraction, and they cannot obtain the unique flavor characteristics of high pressure extraction.

[0011] IV. High store costs For B2B coffee shops, providing high-quality freshly brewed coffee requires purchasing expensive semi-automatic espresso machines (typically costing tens of thousands to hundreds of thousands of yuan) and employing professionally trained baristas. The equipment and labor costs are extremely high, and the brewing efficiency is limited by the barista's speed and consistency, making it difficult to meet the large volume of orders during peak hours. Furthermore, differences in the operation by different baristas can lead to inconsistent flavors, impacting the customer experience and brand reputation.

[0012] In summary, existing technologies in coffee preparation suffer from multiple technical defects, including flavor degradation, the contradiction between filtration accuracy and flavor preservation, limitations of cold brew processes, and high store costs. A new technical solution is urgently needed to address these issues. Summary of the Invention

[0013] The first objective of this invention is to provide a high-temperature sterilization-free filtration method. This filtration method uses a stepped filtration process to first filter out coarse coffee powder that affects the fine filtration of the ceramic membrane. Then, in the fine filtration of the ceramic membrane, bacteria and other microorganisms are removed without affecting the passage of large molecular proteins and coffee oils through the filter pores. This filtration method is used in the preparation of coffee concentrate. Compared with the traditional coffee preparation method that requires high-temperature sterilization to destroy the coffee flavor, this method avoids the destruction of coffee flavor by high-temperature sterilization and ensures the microbial safety of the coffee concentrate.

[0014] The second objective of this invention is to propose a coffee concentrate preparation process based on the above-mentioned filtration method. This coffee concentrate preparation process produces concentrated coffee liquid with good flavor retention and low microbial risk without heat treatment to destroy the flavor. The concentrated coffee liquid can be directly transported to the store and then used with a quick-connect system to prepare different coffee drinks, solving the problems of high cost, low cupping efficiency, and difficulty in ensuring flavor consistency due to differences in barista operation in B-end stores.

[0015] To achieve the above objectives, the present invention adopts the following technical solution: A filtration method for preparing coffee concentrate without high-temperature sterilization, characterized by comprising the following steps: Grinding: Grind roasted coffee beans into coffee powder with controlled coarseness, ensuring that the proportion of coffee powder with a particle size of 40-25 mesh reaches more than 50%; Extraction: Extracting coffee powder to obtain concentrated coffee liquid; Pre-filtration: The coffee concentrate is pre-filtered through a pre-filter screen / cartridge to obtain coffee coarse filtrate with a turbidity of 100~200 NTU; the pre-filtration is used to remove large coffee particles to prevent them from clogging the ceramic membrane filter pores in the subsequent ceramic membrane fine filtration step. Ceramic membrane fine filtration: The coarse coffee filtrate is pumped into a ceramic membrane system for fine filtration to obtain coffee concentrate with a turbidity of 0 NTU-10 NTU; The ceramic membrane filtration step includes fine filtration using a ceramic membrane system with a pore size of 200nm-500nm, which is mainly used to filter out harmful microorganisms and ensure that the turbidity of the coffee concentrate is low enough.

[0016] The pre-filtration step involves sequentially passing the filter through a 100-mesh (150μm) and a 400-mesh (38μm) filter. In practice, the filter screens or cartridges with different pore sizes are connected in series. The filter first passes through the larger pore size (100-mesh) filter, followed by the smaller pore size (400-mesh). Between the 100-mesh and 400-mesh filters, intermediate pore sizes (such as 200-mesh or 300-mesh) can also be used. This gradually decreasing pore size prevents clogging of the filter screen or cartridge, ensuring effective filtration.

[0017] A process for preparing coffee concentrate includes steps such as coffee bean pretreatment, coffee bean roasting, grinding to a specific particle size, degassing, high-pressure extraction, pre-filtration, and ceramic membrane filtration.

[0018] Green coffee bean pre-processing: Green coffee beans undergo four pre-processing steps: magnetic separation, air separation, vibrating sieve, and color sorting. Magnetic separation uses 8000Gs magnetic rods to remove magnetic impurities such as metallic substances; air separation removes lighter impurities such as dust and light fruit peels; vibrating sieve removes denser impurities such as small stones and sand; color sorting uses photoelectric detection to remove abnormal beans such as moldy beans, insect-damaged beans, and unripe beans. The combination of these four pre-processing steps ensures the purity of the coffee bean raw materials entering the roasting stage, avoiding the negative impact of impurities on subsequent flavor.

[0019] Roasting of green coffee beans: Pre-treated green coffee beans are roasted; pure hot air roasting equipment is preferred for roasting pre-treated green coffee beans. Compared to traditional drum roasting / roasting equipment, pure hot air roasting equipment has the following technical advantages: faster roasting speed (single-pot roasting time can be reduced to about 8 minutes, while traditional drum equipment usually takes 15 minutes), lower broken bean rate (can be controlled below 0.3%, while traditional drum equipment is usually around 1.3%), and cleaner flavor (no obvious off-flavors). Rapid roasting helps retain the volatile aromatic compounds in coffee beans and reduces the loss of aromatic compounds caused by prolonged heating; the clean flavor lays the foundation for the high quality of the final product.

[0020] Specific particle size grinding: Roasted coffee beans are ground with controlled fineness, requiring that 40-25 mesh coffee powder particles account for more than 50%. Controlling the grinding particle size is one of the key technical aspects of this invention, and its setting is based on the following: When high-pressure extraction is used in subsequent stages, if there is too much ultra-fine coffee grounds (fineer than 40 mesh), a "channeling effect" can easily occur under high water pressure of 7-11 bar. This means that the water flow will break through the dense layer of fine coffee grounds, forming water channels, leading to uneven extraction. Some areas will be over-extracted, resulting in bitterness, while other areas will be under-extracted, resulting in a thin flavor. Conversely, if there is too much coarse coffee grounds (greater than 25 mesh), the contact area between the coffee grounds and water will be insufficient, resulting in incomplete extraction, low extraction rate of flavor compounds, and a thin taste and insufficient aroma in the finished product. Therefore, the particle size range of 40-25 mesh is an experimentally verified "golden range." Combined with high-pressure extraction, it can ensure the full extraction of high-quality flavor compounds while maintaining good uniformity of coffee grounds extraction, achieving a balance between extraction quality and filtration efficiency.

[0021] Preparing and degassing: The ground coffee powder is put into a metal can with a one-way vent valve, and more than 99% of the air in the can is replaced with nitrogen for 5-7 days.

[0022] The purpose of using nitrogen to degas coffee grounds is twofold: first, to prevent oxidation of the coffee grounds, and second, to prevent the gas from interfering with the contact between water and coffee grounds during the extraction process. Freshly roasted coffee beans contain air and a large amount of carbon dioxide, which is a byproduct of the Maillard reaction and caramelization of sugars and amino acids during roasting. If the ground coffee is directly subjected to high-pressure extraction without degassing, the carbon dioxide gas inside the coffee will affect the contact between water and coffee grounds, leading to incomplete extraction. Excessive gas can also easily cause the pressure to rise during extraction. During extraction, the water flow under high pressure is interfered with by carbon dioxide gas, producing fluctuating resistance, resulting in highly unstable extraction, large pressure fluctuations, and an inability to obtain a stable extraction rate and consistent flavor. This is because carbon dioxide molecules are polar and easily dissolve in water under high pressure to form carbonic acid, interfering with extraction stability; while nitrogen is a nonpolar molecule with extremely low solubility in water. Under high-pressure extraction conditions of 7-11 bar, it remains in the gaseous phase in the gaps between the coffee grounds and does not dissolve in the extraction water to produce bubbles that interfere with extraction. Therefore, after 5-7 days of conditioning and degassing, the carbon dioxide content inside the coffee beans is significantly reduced, while the nitrogen atmosphere only plays a protective role in isolating oxygen and preventing oxidation, and will not have a negative impact on the high-pressure extraction process.

[0023] After 5-7 days of curing and degassing, the carbon dioxide in the coffee powder or between the powder particles is removed, the water flow resistance is stable during high-pressure extraction, the extraction process is controllable, and a stable extraction rate can be obtained.

[0024] Meanwhile, using nitrogen purging instead of natural exposure to air effectively prevents coffee grounds from oxidizing due to prolonged contact with oxygen. The oils and aromatic compounds in coffee are highly susceptible to oxidation, leading to flavor degradation and a stale taste. Nitrogen purging maximizes the preservation of the coffee grounds' freshness and flavor potential.

[0025] High-pressure extraction: Extraction is carried out using high-pressure extraction equipment (such as an espresso machine) at a water pressure of 7-11 bar. The coffee-to-liquid ratio is controlled between 1:2 and 1:2.5. The extraction temperature can be selected as ambient temperature (20-30℃) or high temperature (85-95℃). High-pressure extraction can yield coffee concentrate with a Brix (sweetness / concentration) of approximately 10 or higher.

[0026] The optimal water pressure for high-pressure extraction is 9 bar, with each batch extraction lasting 5-10 minutes. 9 bar is a classic pressure parameter for espresso extraction, proven through long-term industry experience to achieve efficient extraction of flavor compounds at this pressure. A coffee-to-liquid ratio of 1:2 to 1:2.5 is the standard range for espresso, yielding a moderately concentrated and flavorful concentrate. A Brix 10 or higher concentration ensures the richness and dilutionability of the filtered concentrate, allowing for dilution with water or milk at a ratio of 1:6 to 1:19 in shops, maintaining sufficient coffee flavor intensity.

[0027] Pre-filtration: The extracted coffee concentrate is cooled to prevent temperature from affecting the filtration effect. Then, it is passed through a pre-filter or filter cartridge with a pore size of 100 mesh and 400 mesh in sequence to obtain coffee coarse filtrate. The purpose of pre-filtration is to remove large coffee particles and prevent them from clogging the ceramic membrane filter pores in the subsequent ceramic membrane fine filtration step.

[0028] Coffee concentrate contains a large amount of coffee powder (depending on the grinding process, over 50% of the coffee powder has a particle size of 40-25 mesh). Without this pre-filter coarse treatment, the micron-sized particles in the coffee concentrate will directly impact the pores of the ultra-fine ceramic membrane in the fine filtration step, causing a filter cake layer to quickly form on the surface of the ceramic membrane, clogging the pores, drastically increasing the frequency of ceramic membrane cleaning, shortening the membrane's lifespan, and increasing production costs. Therefore, in this invention, the pre-filter coarsely filters out most micron-sized particles, extending the operating cycle and lifespan of the core ceramic membrane in the later stages.

[0029] Ceramic membrane filtration: The coarsely filtered coffee liquid is pumped into a ceramic membrane system with a pore size of 200nm-500nm for ultra-microfiltration. The turbidity of the filtered coffee liquid is controlled at 0-10 NTU. Turbidity is mainly used to measure the clarification effect and impurity removal degree before and after ceramic membrane filtration. It is one of the important indicators for judging whether "raw / fresh coffee" has met the requirements of physical sterilization and sensory evaluation. The higher the turbidity value, the more turbid the liquid and the more suspended matter; while the lower the turbidity value, the clearer the liquid and the less suspended matter. In this invention, the turbidity is controlled at 0-10 NTU, indicating that the coffee liquid after ceramic membrane filtration has the characteristics of being clear and clean.

[0030] The principle and technical effect of setting the pore size of the ceramic membrane in this invention are analyzed as follows: This invention employs a stepped filtration protection method, combining pre-filter coarse filtration with ceramic membrane fine filtration. First, large coffee particles in the concentrated coffee liquor are removed to prevent them from clogging the filter pores and hindering filtration during the ceramic membrane fine filtration process. Without pre-filtration, the diameter of the ceramic membrane pores must be smaller than the diameter of the large coffee particles to prevent them from passing through. Large coffee particles would quickly form a filter cake layer on the ceramic membrane, further obstructing filtration. This invention solves the problem in existing technologies where high-quality coffee liquid cannot be directly filtered through a ceramic membrane while simultaneously filtering out microorganisms. After removing large coffee particles through pre-filter coarse filtration, it does not affect the passage of large protein molecules and coffee oils through the filter pores. Coffee oils have a wide particle size distribution, with many oil droplets ranging from 100nm to 500nm. The molecular weight of coffee proteins ranges from several thousand to hundreds of thousands of Daltons, and some proteins also fall within this range. This invention selects a ceramic membrane system with a pore size of 200nm-500nm for fine filtration, ensuring that these key flavor substances can pass smoothly through the membrane pores into the final product, while microorganisms are retained.

[0031] Furthermore, common pathogenic bacteria (such as Escherichia coli and Salmonella) are generally between 500-2000 nm in size, while putrefactive bacteria and yeasts are also in the 500-1000 nm range. If the pore size of the ceramic membrane filter is too large (e.g., 700-900 nm), some microorganisms will penetrate the membrane pores and enter the filtrate, causing the product's shelf life to fall short of requirements (it is difficult to exceed 3 days) without subsequent sterilization treatment, and posing a serious food safety risk. Therefore, this invention achieves physical sterilization through ceramic membrane filtration, completely avoiding the impact of heat treatment on coffee flavor. At the same time, the dual filtration method of coarse and fine filtration ensures that the coffee liquid is clear and clean, resulting in a better visual experience.

[0032] In this invention, the ceramic membrane pore size of 200nm-500nm (0.2-0.5μm) is a "golden ratio" that has been precisely calculated and verified through numerous experiments. Its technical advantages are reflected in the following two aspects: First, it effectively intercepts microorganisms. The lower limit of this pore size range, 0.2 μm, can effectively intercept the vast majority of common microorganisms. Escherichia coli is approximately 2.0 μm long and 0.5 μm wide, but its minimum cross-sectional diameter is still greater than 0.2 μm; yeast spores typically have a diameter of 3-10 μm; and mold spores typically have a diameter of 2-10 μm. A pore size of 0.2 μm can form an effective physical barrier against these microorganisms. Experimental data shows that under refrigerated storage conditions at 3-5℃, the total bacterial count in coffee concentrate rapidly increased from less than 5 per plate (1 day) to over 1000 (14 days) in the extracted coffee concentrate, while the count was undetectable (within 7 days) and below 100 (within 21 days) in coffee filtered through a 0.2-0.5 μm ceramic membrane, and E. coli remained undetectable throughout the 21 days. This fully demonstrates the physical sterilization effect of this pore size range.

[0033] Secondly, it allows flavor compounds to pass through. The upper limit of this pore size range, 0.5 μm, allows most oil droplets and protein molecules in coffee to pass through smoothly. A large proportion of coffee oils have a particle size smaller than 0.5 μm, and these components are key to the body and aroma complexity of coffee. Smaller molecular weight components of proteins (such as some peptides and amino acids) can also pass through smoothly. Therefore, this pore size range achieves physical sterilization while preserving the freshly brewed flavor of the coffee to the greatest extent.

[0034] This invention chooses ceramic membranes (inorganic membranes) instead of organic membranes such as hollow fibers because coffee liquid has an extremely high oil content, which easily adheres to and clogs the membrane pores, necessitating rinsing or replacement of the filter membrane. Organic membranes (such as hollow fiber membranes or flat sheet membranes made of polysulfone, polyethersulfone, polyacrylonitrile, etc.) have poor fouling resistance; once oil adheres, it is difficult to clean, and it is not resistant to strong acids and alkalis, limiting the choice of cleaning agents. More importantly, organic membranes do not support physical high-pressure backwashing; once clogged, they can only be chemically cleaned or the membrane module replaced, resulting in high operating costs and short service life. In contrast, tubular ceramic membranes, prepared using inorganic materials such as alumina, zirconium oxide, or silicon carbide as substrates, possess excellent properties such as high pressure resistance, resistance to strong acids and alkalis, and high temperature resistance. Most importantly, ceramic membranes support physical high-pressure backwashing (backwashing pressure is typically 0.3-0.6 MPa), which can effectively remove contaminants adhering to the membrane surface through reverse water flow, restoring membrane flux. This characteristic enables the ceramic membrane to operate stably for extended periods in the filtration of coffee liquor with high oil content, solving the biggest pain point in industrial mass production: membrane clogging. This significantly improves system throughput and reduces operating costs. The ceramic membrane used in this invention is preferably alumina ceramic membrane, with a membrane tube diameter of 30 mm, a length of 1200 mm, and a 19-channel design. Alumina ceramic membranes possess excellent mechanical strength and chemical stability, exhibiting a throughput attenuation rate of less than 10% / 8h even in high-oil coffee liquor environments.

[0035] (8) Non-heat post-treatment and filling Depending on the target product line, two non-thermal post-treatment routes are adopted: Green Coffee Route (Zero Pasteurization): The clear coffee liquid filtered through a ceramic membrane undergoes no pasteurization process and is directly aseptically / cleanly bottled (using kegs or bag-in-boxes similar to those used for draft beer), and stored and transported via a complete cold chain at 0-4℃. Under refrigeration conditions at 3-5℃, the shelf life is controlled to 14 days. This route preserves the original flavor of the coffee to the greatest extent, and the product is positioned as "green coffee," similar to draft beer compared to pasteurized beer, emphasizing freshness, original flavor, and no processing.

[0036] Fresh Coffee Route (HPP Sterilization): For scenarios requiring a slightly longer shelf life or more stable room temperature tolerance, the filtered coffee liquid is bottled and then subjected to HPP (High Pressure Processing) for non-thermal treatment. HPP treatment pressure is typically 400-600 MPa, and the treatment time is 3-5 minutes. Under ultra-high pressure, the cell membrane structure of microorganisms is disrupted, and proteins denature and coagulate, thus achieving a sterilization effect. Due to the low processing temperature (usually room temperature or slightly below room temperature), there is almost no thermal damage to the coffee's flavor compounds. Furthermore, storage at 3-5℃ can significantly extend the shelf life to 60 days.

[0037] The coffee shop of this invention does not require a coffee machine. Simply connect the container filled with "raw coffee / fresh coffee" to the refrigerated direct output equipment, and push it with nitrogen (N2) or carbon dioxide (CO2) gas pressure to dispense the liquid through a tap (similar to a craft beer brewing column). Then, add water to dilute it to make Americano coffee, or add milk to make latte coffee, without affecting the final type of coffee output.

[0038] The purpose of using nitrogen or carbon dioxide to propel the liquid out of the container is twofold: First, it isolates oxygen, preventing the oils from oxidizing and turning sour. Both nitrogen and carbon dioxide are inert gases, capable of displacing oxygen at the top of the container, creating a protective atmosphere and slowing down the oxidation reaction. Second, nitrogen can create a dense foam (similar to crema) in room temperature / cold drinks, highly replicating the appearance and texture of the crema layer in espresso made by a coffee machine in a store, enhancing both the visual and taste experience.

[0039] The beneficial effects of this invention are summarized as follows: First, it creates a completely new product category. This invention is the first to propose and implement a "green / fresh coffee" preparation method in coffee concentrate preparation that uses physical interception and sterilization. The preparation process does not involve high-temperature treatment, thus preserving flavor compounds, and the coffee concentrate is free of harmful bacteria. Through flavor evaluation and comparison, the green coffee product of this invention far surpasses commercially available UHT concentrates in terms of aroma, cleanliness, aftertaste, and overall evaluation.

[0040] Secondly, it boasts high commercial value, enabling the creation of a low-cost, high-efficiency store model. B-end stores don't need to purchase expensive espresso machines costing tens of thousands to hundreds of thousands of yuan, nor do they need to hire professional baristas. They can simply turn on the "green / fresh coffee" tap to quickly dispense a cup, ensuring 100% consistent taste, significantly reducing the barriers to entry and operating costs for coffee shops. This innovative business model is expected to trigger a channel revolution in the coffee industry, potentially even leading to mobile coffee shops mounted on vehicles or carts, further reducing store costs without compromising coffee quality.

[0041] Third, it achieves a breakthrough in solving the problem of filter clogging. This invention innovatively proposes a combination of "specific grind size (40-25 mesh > 50%) + 100 and 400 mesh pre-filters + 200-500 nm pore size ceramic membrane fine filter," which for the first time solves the industry problem of easy clogging in industrial nanoscale filtration of coffee concentrate with high oil content, while simultaneously achieving sterilization. This combination ensures extraction effect and coffee flavor by controlling the grind size at the front end, intercepts large coffee particles in the middle pre-filter to protect the efficiency of the downstream ceramic membrane fine filter and prevent clogging, and uses a backwashable ceramic membrane at the downstream end to restore flux and filter out microorganisms, forming a method for preparing coffee concentrate with sufficient flavor integrity, low turbidity, and low microbial risk. Attached Figure Description

[0042] Figure 1 This is a comparison chart of the clarification effects before and after filtration in Example 1.

[0043] Figure 2 A comparison chart of flavor evaluation results for different processing methods. Detailed Implementation

[0044] The present invention will be further described in detail below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0045] Example 1: Green Coffee Route (Vietnamese coffee beans, room temperature extraction) (1) Green bean pretreatment: Vietnamese coffee beans are selected as raw materials and are sequentially subjected to magnetic separation (8000Gs magnetic rod), air separation, vibrating sieve (20 mesh), and color sorting to remove metal impurities, dust, small stones and abnormal beans.

[0046] (2) Roasting: A Neuhaus Neotec NEOROAST 30 pure hot air roasting machine was used, with the roasting degree set to 45 and the roasting time per batch being 8 minutes. The broken bean rate was found to be 0.3%.

[0047] (3) Grinding: A commercial coffee grinder was used for grinding, and the grinding parameters were controlled so that the proportion of coffee powder with a particle size of 40-25 mesh reached 55%. After sieving and testing, the proportion of fine powder below 40 mesh was 15%, the proportion of coarse powder above 25 mesh was 30%, and the proportion of medium particle size (40-25 mesh) was 55%. The control of the grinding particle size ensured the smooth extraction of coffee liquid and good flavor.

[0048] (4) Preparing coffee powder and venting: Put the ground coffee powder into a metal can with a one-way venting valve, introduce nitrogen to replace the air in the can, and vent for 5 days under nitrogen protection to replace 99% of the air in the can.

[0049] (5) High-pressure extraction: An Italian flash extraction device was used. The extraction temperature was set to 25℃ (the range of which is 20℃-30℃), and the pressure was set to 9 bar (in actual production, the pressure can be adjusted between 7-11 bar). The coffee-to-liquid ratio was controlled at 1:2.2 (in actual production, the range of which is 1:2-2.5). The extraction time was 7 minutes (in actual production, the range of which is 5-10 minutes). Testing showed that the Brix (sweetness / concentration) of the extracted coffee concentrate was approximately 11.2, indicating that the soluble substances in the coffee powder were effectively "extracted" by the high-pressure water flow. The turbidity of the coffee concentrate was 198 NTU, and the appearance of the coffee concentrate was as follows: Figure 1 As shown in Figure A.

[0050] (6) Pre-filtration: The concentrated coffee liquid is cooled to below 10°C using a plate heat exchanger, and then passed sequentially through a pre-filter or filter cartridge with 100-mesh and 400-mesh pore sizes to obtain coarse coffee filtration. The purpose of pre-filtration is to remove large coffee particles to prevent them from clogging the ceramic membrane pores in the subsequent ceramic membrane filtration step. Pre-filtration is a crucial step in the subsequent ceramic membrane filtration. Only by filtering out large coffee particles in advance can the ceramic membrane filtration proceed smoothly. This is also why ceramic membranes cannot be directly used for coffee filtration and sterilization while maintaining good flavor in current commercial applications.

[0051] (7) Ceramic membrane fine filtration: The coarsely filtered coffee liquid is pumped into an alumina ceramic membrane system with a pore size of 200 nm (in actual production, the pore size of the ceramic membrane filter is adjusted between 200-500 nm) for ultra-micro filtration. The operating temperature is 10-15℃, and the transmembrane pressure difference is controlled at 0.1-0.2 MPa. The turbidity of the filtered coffee liquid is 0 NTU (Leici WZB-172, reaching the lower limit of the detection instrument), and the appearance of the finely filtered coffee liquid is as follows. Figure 1 As shown in B.

[0052] (8) Aseptic filling and cold chain storage and transportation: The coffee liquid filtered through the ceramic membrane is directly aseptically filled into Keg containers, which are pre-filled with nitrogen. After filling, it is quickly transferred to a cold chain storage and transportation system at 0-4℃. According to testing, the product has a shelf life of up to 14 days under refrigeration conditions of 3-5℃.

[0053] The unfiltered and filtered coffee concentrates from Example 1 were stored at 3-5°C for 1-21 days. Escherichia coli and whole colony counts (GB 4789) were performed multiple times on days 1, 7, 14 and 21. The results are shown in Tables 1 and 2.

[0054] Table 1. Detection results of Escherichia coli

[0055] Table 2. Detection results of bacterial colonies

[0056] Table 1 shows that neither the original coffee concentrate nor the coffee concentrate was contaminated with E. coli. Table 2 shows that no bacterial colonies were detected in the filtered coffee concentrate after 14 days, indicating that the coffee concentrate obtained by the filtration method of this invention has a long shelf life and can be stored at 3-5℃ for up to 14 days. This is a method for preparing coffee concentrate without high-temperature sterilization.

[0057] Example 2: Green Coffee Route (Vietnamese Coffee Beans, High-Temperature Extraction) Steps (1)-(4) are the same as in Example 1.

[0058] (5) High-pressure extraction: The extraction temperature was set to a high temperature of 90℃ (the high temperature range was 85-95℃), the pressure was set to 9 bar, and the coffee-to-liquid ratio was controlled at 1:2.0. The extraction time was 6 minutes. The Brix of the extracted coffee concentrate was 10 (ATAGO PAL-1 digital saccharimeter, 20℃, unit: %), and the turbidity was 216 NTU.

[0059] Steps (6)-(8) are the same as in Example 1. The turbidity of the filtered coffee liquid is 8 NTU, and the product has a shelf life of up to 14 days under refrigeration conditions of 3-5℃.

[0060] Compared with Example 1, the product extracted at high temperature has a higher alcohol content and a richer aroma, but some volatile aromatic substances are lost, and the aroma complexity is slightly lower than that of the product extracted at room temperature.

[0061] Example 3: Fresh Coffee Route (HPP Sterilization) Steps (1)-(7) are the same as in Example 1.

[0062] (8) Filling and HPP sterilization: The coffee liquid filtered through the ceramic membrane is cleanly filled into PET bottles. The filled product is then subjected to HPP treatment at a pressure of 500 MPa (in actual production, the pressure range is 400-600 MPa), a treatment time of 4 minutes (in actual production, the treatment time ranges from 3 to 5 minutes), and a treatment temperature of room temperature (25°C).

[0063] Testing showed that the microbiological indicators of the HPP-treated product fully comply with national food safety standards. The product can be stored for 30 days at room temperature (25℃) and has a shelf life of up to 60 days under refrigeration at 3-5℃.

[0064] Compared to the raw coffee route in Example 1, the microorganisms in the coffee liquid of the fresh coffee route are further killed, thus significantly extending the shelf life.

[0065] Example 4: Comparison of different pollen-nourishing times Steps (1)-(3) are the same as in Example 1.

[0066] (4) Pollen cultivation and degassing: Three control groups were set up: no pollen cultivation (0 days), pollen cultivation for 3 days, pollen cultivation for 5 days, and pollen cultivation for 7 days. All were carried out under nitrogen protection.

[0067] (5) High pressure extraction: All groups were extracted under the same conditions (room temperature 25℃, 9 bar, 1:2.2 powder-to-liquid ratio).

[0068] Test results: Unseasoned powder group: The extraction process was subject to large pressure fluctuations and unstable water flow, resulting in an extraction yield of 17%. The flavor was good, but the taste was rather thin.

[0069] 3-day conditioning group: The extraction process was relatively stable, with an extraction yield of 22%, good flavor, and a relatively full-bodied taste.

[0070] 5-day conditioning group: The extraction process is stable, the extraction yield is 26%, the aroma is rich, the flavor is good, and the taste is full-bodied.

[0071] 7-day conditioning group: The extraction process was stable, with an extraction yield of 26.5%. It had a rich aroma, good flavor, and full-bodied taste, with little difference from the 5-day group.

[0072] Conclusion: A 5-7 day conditioning period is the optimal time window for achieving the best flavor and stable extraction results in high-pressure extraction. Less than 5 days results in insufficient carbon dioxide removal and unstable extraction; more than 7 days results in minimal flavor improvement and increases production cycle and inventory costs.

[0073] Example 5: Comparison of different grinding particle sizes Steps (1)-(2) are the same as in Example 1.

[0074] (3) Grinding: Set up three comparison groups: Group A: Mainly fine powder (60% below 40 mesh) Group B: Particle size of this invention (40-25 mesh, 55%) Group C: Mainly coarse powder (60% of the powder is 25 mesh or finer). (4)-(7) Same as Example 1.

[0075] Test results: Group A: Severe channeling effect occurs during extraction, resulting in incomplete extraction of coffee powder and a strong bitter taste in the concentrated coffee liquor.

[0076] Group B: Uniform extraction, balanced and full flavor; Group C: The extraction was sufficient, but the extraction rate of flavor substances was low. The Brix of the finished product was only 8.5, resulting in a thin taste and insufficient aroma.

[0077] Conclusion: A 40-25 mesh ratio of 50% or more is the optimal choice for balancing extraction quality and filtration efficiency.

[0078] Example 6: Comparison of Pore Sizes of Different Ceramic Membranes Steps (1)-(6) are the same as in Example 1.

[0079] (7) Ceramic membrane fine filtration: Four control groups were set up: Group A: 50nm ceramic film (refer to CN103720830A) Group B: 200nm ceramic film Group C: 500nm ceramic film Group D: 0.8μm ceramic membrane (refer to CN115720950A) Each group was filtered under the same operating conditions.

[0080] Test results: Group A (50nm): After filtration through the ceramic membrane, the coffee liquid became clear and transparent, with the Brix dropping from 11.2 to 8.5, indicating that a large amount of oils and proteins were blocked. Flavor assessment showed "heavy wateriness, lack of body, and weak aroma." The membrane flux was extremely low, and filtration was almost impossible after one hour of operation.

[0081] Group B (200nm) ceramic membrane filtration resulted in a clear and transparent coffee liquid. The Brix index decreased slightly from 11.2 to 9.8, but the flavor was well preserved. Microbiological testing showed no detectable total bacterial count within 7 days and no detectable count after 14 days. The membrane flux was moderate, and the operation was stable.

[0082] Group C (500nm): The coffee liquid after ceramic membrane filtration was clear and transparent, with the Brix value decreasing from 11.2 to 10.2, indicating optimal flavor retention. Microbiological testing showed no detectable total bacterial count within 7 days and no detectable count after 14 days. The membrane flux was high, and the operation was stable.

[0083] Group D (800nm): After ceramic membrane filtration, the coffee liquid was clear and transparent, and the Brix dropped from 11.2 to 10.5, with the flavor fully preserved. However, microbial testing showed that the total bacterial count was less than 5 per plate within 1 day and exceeded 500 within 3 days, making it impossible to achieve a 7-day shelf life without sterilization.

[0084] Conclusion: 0.2-0.5μm is the effective pore size range for achieving the dual objectives of "physical sterilization + flavor preservation" in this invention. A pore size of 50nm is too small and will damage the flavor; a pore size of 0.8μm is too large and cannot achieve sufficient sterilization.

[0085] Example 7: Application of Terminal Quick Connect Supply System The raw coffee concentrate prepared in Example 1 was filled into 5L Keg containers, which were pre-filled with nitrogen to 0.3MPa. The Keg containers were then connected to the store's refrigerated direct-outflow equipment (temperature set at 4°C).

[0086] Dispensing procedure: Turn on the tap, and the coffee liquid will flow out at a rate of 15 mL per second under the pressure of nitrogen gas (0.3 MPa). During dispensing, the nitrogen gas mixes with the coffee liquid to form a dense foam layer (similar to the crema of an espresso).

[0087] Comparative Example 1: Traditional UHT pasteurized coffee concentrate The same coffee bean raw materials and extraction process as in Example 1 were used, but after filtration, UHT ultra-high temperature instantaneous sterilization (138°C, 5 seconds) was performed, followed by aseptic filling.

[0088] A 10-person evaluation panel (3 professional baristas, 2 professional beverage mixologists, and 5 ordinary consumers) conducted a flavor evaluation of the green coffee and traditional UHT pasteurized coffee concentrate of Example 1 of this invention. The flavor evaluation results (using the unfiltered coffee concentrate sample as the standard, with the standard sample scored 5 points, and the average value of the results) are shown in Table 3 and... Figure 2 As shown.

[0089] Table 3. Flavor evaluation results of the concentrated coffee liquid of Example 2 of the present invention and the traditional UHT sterilized coffee concentrate.

[0090] The results show that UHT treatment resulted in the loss of a large amount of aromatic substances due to volatilization, and the aroma score was significantly reduced. High temperature caused oil oxidation and protein denaturation, producing a slight cooked taste, which affected the overall flavor evaluation. Since the loss of aromatic substances is small when extracted at room temperature, the comparison is not very meaningful. Therefore, Table 3 shows the results of comparing the raw coffee prepared by high temperature extraction in Example 2 with the UHT concentrate, in order to demonstrate the effect of the coffee concentrate preparation method of the present invention on the preservation of coffee flavor.

[0091] Comparative Example 2: Traditional Pasteurized Coffee Concentrate The same preparation method as in Example 2 was used, but pasteurization (85°C, 15 minutes) was performed after filtration, followed by filling.

[0092] Flavor evaluation results: The overall score was slightly higher than that of the UHT product (overall score 3.8), but still significantly lower than that of the raw coffee prepared in Example 2 of this invention (5.6). The pasteurization temperature was lower, and the degree of flavor degradation was slightly less than that of UHT, but there was still a significant heat damage effect.

[0093] Comparative Example 3: Cold Brew Coffee Liquid The same coffee bean raw material as in Example 1 was used, but it was prepared by cold brewing (25°C, atmospheric pressure, 12-hour soaking), and then subjected to pre-filtration and ceramic membrane filtration as in Example 1 of this invention, and then filled.

[0094] Test results: Extraction yield was 15%, Brix score was 8.5. Flavor assessment showed a refreshing taste but significantly insufficient body (base note 3.2 points). The aroma was predominantly floral and fruity, lacking the rich caramel and nutty aromas characteristic of high-pressure extraction. Although heat damage was avoided, the flavor expression of cold extraction is completely different from that of high-pressure extraction, failing to meet the needs of consumers seeking a richer taste.

[0095] Comparative Example 4: No pre-filter used Steps (1)-(5) are the same as in Example 1.

[0096] Then, the ceramic membrane filtration process in step (7) is carried out directly. Since the coffee concentrate has not undergone pre-filtration, large coffee particles have not been removed in advance. During ceramic membrane filtration, large coffee particles quickly form a filter cake layer on the surface of the ceramic membrane, clogging the membrane pores and directly affecting the passage of coffee flavor substances. High-frequency ceramic membrane rinsing is required to solve the clogging problem. However, if a ceramic membrane with a larger pore diameter is directly replaced, the sterilization effect cannot be achieved. Furthermore, it should be noted that in this invention, the specific grind size of the coffee beans directly determines whether the flavor compounds of the coffee can be fully extracted during the extraction process to ensure the flavor of the coffee liquid. At the same time, the choice of grind size determines the choice of pore size for the subsequent pre-filter. The pore size of the pre-filter needs to ensure that large coffee particles are intercepted as much as possible while allowing flavor compounds to pass through the pores. Finally, the ceramic membrane filtration removes microorganisms and ensures the clarity of the coffee liquid. Obviously, the low-microbial-risk and flavorful coffee liquid of this invention cannot be obtained by simply gradient filtration. Gradient filtration can only ensure that the subsequent ceramic membrane filtration is not affected by large coffee particles. Rather, it is the result of the synergistic effect of "specific grind size (40-25 mesh > 50%) + 100 and 400 mesh pre-filters + 200-500 nm pore size ceramic membrane filtration". Grind size control ensures the flavor of the coffee. Combined with pre-filters and ceramic membrane filtration, the coffee is protected from high-temperature treatment throughout the entire preparation process, thus ensuring the flavor of the coffee. At the same time, the precise control of the pore size ensures the microbial safety of the coffee liquid.

[0097] Therefore, pre-filtration is crucial for subsequent ceramic membrane filtration for sterilization and for preserving flavor compounds in the coffee liquid. The step-by-step filtration method of pre-filtration and ceramic membrane filtration of this invention achieves unpredictable results, solving the problem in existing technologies where good coffee taste and microbial safety are mutually exclusive. In the entire coffee concentrate preparation method of this invention, the specific particle size distribution not only determines the flavor of the extracted coffee but also creates the preconditions for subsequent pre-filtration and membrane filtration; nitrogen conditioning and degassing are not just routine bean awakening but also enhance the stability of high-pressure extraction; two-stage pre-filtration is not just for removing particles but also for protecting the ceramic membrane and stabilizing the flux; 200-500nm ceramic membrane filtration not only ensures the microbial safety of the coffee concentrate but also strikes a balance between flavor preservation and microbial control.

[0098] The above description of the embodiments is provided to enable those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the embodiments described herein, and any improvements and modifications made to the present invention by those skilled in the art based on the disclosure thereof should be within the scope of protection of the present invention.

Claims

1. A filtration method for preparing coffee concentrate without high-temperature sterilization, characterized in that, Includes the following steps: Grinding: Grind roasted coffee beans into coffee powder with controlled coarseness, ensuring that the proportion of coffee powder particles with a size of 40-25 mesh reaches more than 50%; Extraction: Extracting coffee powder to obtain concentrated coffee liquid; Pre-filtration: The coffee concentrate is pre-filtered through a pre-filter screen / filter cartridge to obtain coffee coarse filtrate with a turbidity of 100~200 NTU; Ceramic membrane fine filtration: The coarse coffee filtrate is pumped into a ceramic membrane system for fine filtration to obtain coffee concentrate with a turbidity of 0 NTU-10 NTU; The ceramic membrane filtration step includes fine filtration using a ceramic membrane system with a pore size of 200nm-500nm.

2. The filtration method for preparing coffee concentrate without high-temperature sterilization according to claim 1, characterized in that, The pre-filtration step involves passing the filter through a filter screen / cartridge with a pore size of 100 mesh and 400 mesh in sequence.

3. A process for preparing coffee concentrate, characterized in that, Includes the following steps: (1) Pre-treatment of green coffee beans: Green coffee beans are subjected to magnetic separation, air separation, vibrating sieve and color sorting to remove impurities and abnormal beans respectively; (2) Roasting: Roasting the pre-treated green coffee beans; (3) Grinding: Grind the roasted coffee beans with controlled coarseness, and control the proportion of coffee powder with a particle size of 40-25 mesh to be more than 50%; (4) Preparing and degassing: Put the ground coffee powder into a metal can with a one-way vent valve and degas it with nitrogen for 5-7 days. (5) Extraction: Extract coffee powder to obtain concentrated coffee liquid; (6) Pre-filtration: After cooling the coffee concentrate, it is coarsely filtered through a pre-filter with a pore size of 100 mesh and 400 mesh to obtain coffee coarse filtrate and remove large particles of powder. (7) Ceramic membrane fine filtration: The coarsely filtered coffee liquid is pumped into a ceramic membrane system for fine filtration to obtain coffee concentrate; the ceramic membrane fine filtration step includes fine filtration with a ceramic membrane system with a pore size of 200nm-500nm, and the turbidity of the finely filtered coffee concentrate is controlled at 0 NTU-10 NTU.

4. The preparation process according to claim 3, characterized in that, It also includes step (8) non-thermal post-processing and filling of the coffee liquid: Raw coffee route: The coffee liquid filtered through ceramic membranes is directly aseptically / cleanly bottled and stored and transported through a cold chain at 0-4℃ throughout the process; Fresh Coffee Route: After the coffee liquid is filtered through a ceramic membrane and bottled, it undergoes non-thermal treatment using HPP ultra-high pressure cold sterilization.

5. The preparation process according to claim 3, characterized in that, In step (5), the extraction is high-pressure extraction: a high-pressure extraction device is used to extract coffee at a water pressure of 7-11 bar, and the coffee powder to liquid ratio is controlled between 1:2 and 1:2.5 to obtain concentrated coffee liquid. The extraction temperature is 20-30℃ or 85-95℃.

6. The preparation process according to claim 3, characterized in that, The pressure of the high-pressure extraction in step (5) is controlled at 9 bar, and the extraction time for each batch is 5-10 minutes.

7. The preparation process according to claim 4, characterized in that, The HPP ultra-high pressure cold sterilization process in step (8) has a processing pressure of 400-600 MPa and a processing time of 3-5 minutes.

8. The preparation process according to claim 3, characterized in that, The Agtron value of the ground coffee powder is 45-65.

9. The coffee concentrate prepared according to any one of claims 3-8, characterized in that, The turbidity of the coffee concentrate is 0-10 NTU; Raw coffee has a shelf life of 14 days under refrigeration at 3-5℃. Fresh coffee has a shelf life of 60 days under refrigeration at 3-5℃.

10. A sterile coffee concentrate supply system, characterized in that, include: Filling unit: used to fill the coffee concentrate obtained by the preparation process according to any one of claims 3-8; Storage and transportation unit: A container used for storing and transporting coffee concentrate at a temperature of 0-4℃ throughout the entire cold chain; Terminal output unit: Refrigerated direct output device, which uses nitrogen or carbon dioxide pressure to push the coffee concentrate in the container and dispense it through a tap; In the terminal output unit, the pressure of nitrogen or carbon dioxide is controlled at 0.2-0.4 MPa.

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