A dual-strain white beer production method for optimizing saccharification process

Abstract

The application provides a double-strain white beer production method for optimizing a saccharification process, and relates to the field of beer brewing, and comprises the following steps: S1: adopting a humidity-adjusting crushing process to process malt raw materials to obtain malt mash liquid; S2: discharging the malt mash liquid to a saccharification kettle to perform staged temperature-raising saccharification treatment to obtain saccharified mash; wherein, after the discharging of the malt mash liquid in the saccharification kettle is completed, edible lactic acid, edible gypsum and edible calcium chloride are sequentially added; S3: the saccharified mash is filtered and washed to obtain mixed wort, and the mixed wort is sent to a boiling kettle to complete boiling and shaping, and hops are added in batches during the process; the wort after boiling is subjected to rotary sedimentation, and then cooled to a target temperature, and oxygen is supplied during the cooling process; S4: double-strain fermentation: the wort after cooling is sent to a fermentation tank, and double-strain inoculation fermentation is adopted; the temperature is controlled according to the process stage during the fermentation process, and main fermentation and double-acetyl reduction are sequentially completed. The application adopts malt wort acid-adjusting closed-loop control, adjusts raw materials according to stable pH, and improves brewing stability and quality.

Description

Technical Field

[0001] This invention relates to the field of beer brewing technology, specifically to a method for producing double-strain wheat beer with optimized saccharification process. Background Technology

[0002] Wheat beer is a pale, cloudy beer made primarily from wheat and / or wheat malt, barley malt, and water, with the addition of hops (including hop products). Wheat malt and / or wheat constitute at least 40% of the raw materials for wheat beer. In addition to possessing flavor characteristics such as cloves and esters, it must contain 4-vinylguaiacol (4-VG) ≥1.0 mg / L, and other requirements must comply with the regulations for the corresponding beer type. In beer production, the mashing process is a crucial step affecting wort quality and subsequent fermentation.

[0003] Existing beer production methods, such as the production method of non-alcoholic IPA beer disclosed in CN116355709A, have the following problems: This method adjusts the pH of the mash to 5.0-5.2 with lactic acid in one go after saccharification, without taking into account the actual state of the mash before acid addition (differences in the ionic composition of different batches of malt and brewing water may lead to differences in the actual state of the mash). When the raw materials or water quality fluctuate, the pH adjustment may be over-adjusted or under-adjusted. Summary of the Invention

[0004] This invention provides a dual-strain white beer production method with optimized saccharification process to solve the technical problems mentioned in the background art.

[0005] To address the aforementioned technical problems, this invention discloses a method for producing double-strain white beer with optimized saccharification process, comprising the following steps: S1: Malt raw materials are processed using a moisture-adjusting and pulverizing process to obtain malt mash; S2: The malt mash is fed into the saccharification pot and subjected to segmented heating and saccharification to finally obtain saccharified mash: after the malt mash is fed into the saccharification pot, edible lactic acid, edible gypsum and edible calcium chloride are added in sequence. S3: The mashed mash is filtered and washed to obtain mixed wort. The mixed wort is sent to a boiling kettle to complete the boiling and setting process, during which hops are added in batches. The boiled wort is then swirl-sedied and cooled to the target temperature, with oxygenation during the cooling process. S4: Dual-strain fermentation: The cooled wort is sent into a fermentation tank and fermented using dual-strain inoculation; the temperature is controlled according to the process stage, and the main fermentation and diacetyl reduction are completed in sequence.

[0006] Preferred screening methods for dual-strain microorganisms include: (1) Select multiple candidate brewer's yeast strains as test strains, and conduct fermentation performance tests and ester production ability tests on each strain; (2) Yeast strains that meet the requirements for diacetyl reduction rate and sugar reduction rate are combined with yeast strains that meet the requirements for 4-vinylguaiacol content for mixed fermentation experiments. (3) Based on the data on sugar reduction rate, diacetyl reduction rate and 4-vinylguaiacol content obtained from the mixed fermentation experiment, two yeast strains suitable for brewing white beer were screened.

[0007] Preferably, the fermentation performance test includes: using the CO2 weight loss method, determining the sugar reduction rate by daily weight difference under constant temperature culture conditions of 25℃, and determining the diacetyl reducing capacity; The ester-producing ability test was conducted by measuring the content of 4-vinylguaiacol generated from the decarboxylation of ferulic acid in the fermentation broth to evaluate the ester-producing ability of the strain.

[0008] Preferably, before mass production of S2, a conductivity-pH acidification benchmark strategy is determined, wherein the conductivity-pH acidification benchmark strategy is a three-dimensional correspondence of "conductivity range, pH range, and benchmark lactic acid addition rate range". S2 includes: S21: Add the malt mash to the saccharification pot. After the malt mash in the saccharification pot is added, keep the temperature of the malt mash constant at the first holding temperature. Add edible gypsum and edible calcium chloride in sequence and stir. During the stirring process, periodically check the conductivity of the mixture until the conductivity stabilizes. When the conductivity stabilizes, check and determine the actual stable conductivity and the actual stable pH. S22: Determine the initial lactic acid addition rate based on the actual stable conductivity and actual stable pH and the pH acidification benchmark strategy of conductivity. Keep stirring and start adding edible lactic acid based on the initial lactic acid addition rate until the initial lactic acid addition time. Then, detect the pH at the end of the initial lactic acid addition time to determine the initial pH change rate and detect the conductivity. Based on the initial pH change rate and the conductivity at the end of the initial lactic acid addition time, determine the optimized lactic acid addition rate. Keep stirring and complete the addition of lactic acid based on the optimized lactic acid addition rate. S23: Continue with the segmented temperature-increase saccharification process.

[0009] Preferably, the temperature control strategy for the segmented heating saccharification process is as follows: the initial temperature is 44℃ and held for 30 min, then the temperature is increased sequentially at a rate of 1℃ / min to 55℃ and held for 30 min, 65℃ and held for 60 min, 72℃ and held for 10 min, and then the temperature is increased to 78℃.

[0010] Preferably, a material outlet valve is installed at the bottom of the saccharification pot. The material outlet valve is connected to a circulation pipeline, and then a circulation pump is used to pump the mixture discharged from the material outlet valve back to the material distributor at the top of the saccharification pot to achieve material circulation.

[0011] Preferably, S23 includes: Based on the predetermined material circulation rules for the insulation sections and the actual stable conductivity of the current material, the target circulation flow rate and target circulation time interval corresponding to the 44℃ insulation stage are determined. The preset duration of the 44℃ insulation is one hour, and the material circulation of the saccharification pot is carried out based on the circulation flow rate and circulation time interval corresponding to the 44℃ insulation stage. The 55℃ heat preservation time is preset for two hours. The material circulation of the saccharification pot is carried out based on the circulation flow rate corresponding to 55℃ determined by the material circulation rules of the heat preservation section. The 65℃ heat preservation time is preset to three hours. The material circulation of the saccharification pot is carried out based on the circulation flow rate and circulation time interval corresponding to 65℃, which are determined by the material circulation rules of the heat preservation section. After holding at 72℃ for 10 minutes, the temperature is increased to 78℃. Stop stirring when the material is circulating.

[0012] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. Simultaneously mitigates the impact of fluctuations in water quality and raw materials, providing reliable initial conditions for subsequent acidification: The variety of malt, its solubility, the content of buffer substances, and differences in brewing water all directly affect the conductivity and buffering capacity of the wort. This step, by adding gypsum and calcium chloride and stirring until the conductivity stabilizes, "fixes" the differences brought about by different raw materials and water quality in advance. This ensures that the subsequent acidification stage deals with a wort with a stable ionic composition and a balanced buffer system, avoiding deviations in acidification results caused by fluctuations in water quality or raw materials.

[0014] A stable buffer system provides reliable initial conditions for subsequent acidification: Adding gypsum and calcium chloride allows calcium ions to form buffer pairs with phosphates in the wort, altering its buffering capacity. Measuring pH only after stirring until conductivity is stable ensures that the measured pH and conductivity values ​​accurately reflect the wort's buffering capacity, providing a reliable initial operating condition basis for matching the acidification rate using tables. pH alone cannot fully reflect the wort's buffering capacity; conductivity is a crucial indicator of ionic strength. Simultaneous pH measurement when conductivity is stable allows for the simultaneous acquisition of two key parameters: the wort's acidity / alkalinity and its buffering strength.

[0015] 2. Achieve pre-matching of "raw materials - acid addition rate" to significantly reduce the cost of acid adjustment trial and error: Through the mapping relationship of "conductivity range + pH range → benchmark lactic acid addition rate range" established by the gradient test in the early stage, the corresponding acid addition rate can be obtained directly from the table according to the actual state of the current wort during production. There is no need to rely on the operator's experience to repeatedly add acid, which significantly shortens the acid adjustment time and reduces the acid adjustment error rate caused by insufficient experience.

[0016] Different batches of malt and different water qualities can lead to significant differences in the buffering capacity of wort: wort with strong buffering capacity will have a slower pH drop after acidification; wort with weak buffering capacity will have a rapid pH drop after acidification. The reference rate matched by the lookup table is calibrated for different buffering strengths, thus effectively avoiding overflushing or underacidification problems caused by applying the same rate to all wort.

[0017] 3. Initial pH and conductivity alone cannot fully predict the pH trend after acidification. A short trial acidification period of 2-3 minutes prevents irreversible and significant pH deviations while providing a direct reflection of the wort's actual buffering capacity at the current acidification rate. If issues such as pH electrode drift, metering pump malfunction, or uneven wort mixing exist, these will manifest as abnormal pH change rates during the short trial phase. At this stage, before large-scale acidification, the pH remains within a controllable range, facilitating timely problem detection and shutdown for troubleshooting. This avoids the serious consequences of pH loss of control and mash spoilage during subsequent acidification processes.

[0018] The pH change rate during the trial phase is used as the basis for fine-tuning, achieving dual control of "open-loop prediction + closed-loop correction": the initial rate obtained from the table is based on statistics from previous experiments, while the pH change rate during the trial phase reflects the actual performance of the current batch of wort. By comparing the deviations between the two, the rate is fine-tuned, which is equivalent to adding a closed-loop correction on top of the prediction, further improving the precision of acidification control.

[0019] This invention employs a closed-loop control system of "pre-matching the initial rate by looking up a table + probing acid addition to obtain actual buffering performance + tiered fine-tuning," solving the problem that traditional fixed-rate acidification cannot adapt to fluctuations in raw materials and water quality. Especially when the initial conductivity of the wort is at a critical state, relying solely on table prediction is prone to error. This invention, through feedback on the pH change rate during a 2-3 minute probing phase, can quickly identify the actual buffering capacity and precisely fine-tune the acidification rate by ±5%, ensuring that the final pH of the acidification process remains stable within the target range, thus avoiding over- or under-acidification.

[0020] 3. During the acidification stage, the pH is stably controlled within the target range, providing the optimal pH environment for subsequent key reactions such as protein rest, starch gelatinization, and saccharification and enzymatic hydrolysis. This ensures the activity of proteases and amylases, significantly improves the fermentability and extraction rate of the wort, and avoids interference with the saccharification rhythm caused by repeated adjustments during the acidification process. It also ensures the stable execution of process parameters such as segmented heating and heat preservation, thus guaranteeing the quality of the saccharified mash. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0022] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0023] Furthermore, in this invention, the use of terms such as "first" and "second" is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions and features of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0024] The present invention provides the following embodiments: Example 1: This embodiment of the invention provides a method for producing double-strain white beer with optimized saccharification process, such as... Figure 1 As shown, it includes the following steps: S1: Malt raw materials are processed using a moisture-adjusting and pulverizing process to obtain malt mash. Before S1, the brewing water is treated, achieving a conductivity of 10 μS / cm and a desalination rate of approximately 98%. For the malt raw materials, barley malt is selected based on plump grains, low boiling color, high α-amino nitrogen, and satisfactory physicochemical properties. Wheat malt is selected based on high starch content, low protein content, low saturation value (35-38%), and soft white cortex. The moisture-adjusting and pulverizing process for processing the malt raw materials specifically involves: using a pressure pulverizer with a roller gap of 0.35-0.40 mm; preparing 50 HL of brewing water at 60°C for pre-wetting and soaking the malt; preparing 280 HL of brewing water at 40°C for adjusting the slurry during pulverization to ensure the mash temperature reaches 44°C upon feeding; and preparing 20 HL of water for rinsing the equipment pipelines and rollers after pulverization to recover residual malt flour. 3550kg malt + 3550kg wheat sprouts, total water volume of the pulverizer is 350HL, soaking water volume is 50HL, wet powder water volume is 280HL, rinsing water volume is 20HL, and pulverizing time is 30min.

[0025] S2: The malt mash is fed into the saccharification pot for staged heating and saccharification to obtain saccharified mash (pH 5.4-5.6). After the malt mash is fed into the saccharification pot, edible lactic acid, edible gypsum, and edible calcium chloride are added sequentially. After saccharification, the resulting saccharified mash is divided into two pots for further processing: 3500ml of edible lactic acid, 4kg of edible gypsum, and 4kg of edible calcium chloride. S2 is the saccharification process. S3: The mashed mash is filtered and washed (wash water pH≤5.8) to obtain mixed wort. The mixed wort is sent to a boiling kettle for boiling and setting, during which hops and related additives are added in batches. The boiled wort is then vortexed (the wort in the vortex settling tank is allowed to swirl and stand for 30 minutes), and then cooled to the target temperature. Oxygen is added during the cooling process. The final wort volume is 450 HL. The bitterness value of the finished beer is set at 15 Bu, the α-acid content of Harrard bitters is 6.3%, the α-acid content of Cascade hops is 5.9%, and the hop addition is 30-40 mg / L of α-acid in wort.

[0026] Add 2 kg of edible gypsum and 2 kg of calcium chloride to the boiling pot. Add 10 kg of Halados hops for the first 5 minutes of boiling, and 5 kg of Cascade hops for the last 5 minutes of boiling. Set wort concentration: 11.0-11.2°P.

[0027] Add 50g of zinc sulfate and 7kg of Cascade flowers to the cyclone sedimentation tank 5 minutes before the wort is added. S4: Dual-strain fermentation: The cooled wort is transferred to a fermentation tank and fermented using dual-strain inoculation. The temperature is controlled according to the process stages, and the primary fermentation and diacetyl reduction are completed sequentially. The amount of calcium ions added to the wort transferred to the fermentation tank is 40-80 mg / L, and the amount of zinc ions is 0.2-0.4 mg / L. The hop addition process has been optimized, with hops added in three stages. The first addition is of bitter hops to maximize the utilization of α-acid isomerization. The second and third additions are to fully utilize the aroma of the hops while minimizing the volatilization of essential oils. The first addition of hops is Haraldau bitter hops, 5 minutes after initial boiling; the second addition of hops is Cascade aroma hops, 55 minutes after boiling; and the third addition of hops is Cascade aroma hops, added before entering the wort in the swirl tank.

[0028] The screening methods for dual-strain strains include: (1) Select multiple candidate brewer's yeast strains as test strains, and conduct fermentation performance tests and ester production ability tests on each strain; (2) Yeast strains that meet the requirements for diacetyl reduction rate and sugar reduction rate are combined with yeast strains that meet the requirements for 4-vinylguaiacol content for mixed fermentation experiments. (3) Based on the data on sugar reduction rate, diacetyl reduction rate and 4-vinylguaiacol content obtained from the mixed fermentation experiment, two yeast strains suitable for brewing white beer were screened.

[0029] The fermentation performance test includes: determining the sugar reduction rate (a reflection of fermentation power and fermentation rate) by daily weight difference under constant temperature culture at 25℃, and determining the diacetyl reducing capacity (under constant temperature culture at 25℃, sampling and detecting the diacetyl content in the fermentation broth at regular intervals, and evaluating the diacetyl reducing capacity based on the change in diacetyl concentration over time). The ester-producing ability test was conducted by measuring the content of 4-vinylguaiacol generated from the decarboxylation of ferulic acid in the fermentation broth to evaluate the ester-producing ability of the strain.

[0030] The rate of blood sugar reduction refers to the weight of the bottle and the fermentation liquid after CO2 removal under constant temperature (25℃) culture, and the difference with the previous day, which can reflect the number of grams of blood sugar reduction each day.

[0031] Strain 1 exhibits outstanding fermentation performance, characterized by rapid sugar reduction and strong diacetyl reduction ability, while strain 2 demonstrates strong ester production and a rich ester aroma. Through multiple experiments verifying the synergistic effect of strains 1 and 2, they were ultimately selected as the dual-strain fermentation strains.

[0032] The segmented heating saccharification process includes: initial temperature of 44℃ for 30 min, heating at a rate of 1℃ / min to 55℃ for 30 min, 65℃ for 60 min, 72℃ for 10 min, and then heating to 78℃ before being directly fed into the filter tank.

[0033] The wort cooling and oxygenation rate is 10-12 ppm. The target temperature for the first batch of wort is 18°C, and the target temperature for the second batch of wort is 20°C. When transferring wort to the fermentation tank, oxygenation should be stopped 10 minutes before the fermentation tank is full.

[0034] Two pots of wort filled one fermentation tank; dual-strain fermentation includes: S4a: First, inoculate the yeast culture medium of strain one at 18°C ​​into the fermenter, and then send the first batch of wort cooled to 18°C ​​into the fermenter to complete the first inoculation. S4b: After the first batch of wort has fermented for 20-24 hours, yeast culture solution of strain 2 at 20°C is first added to the same fermentation tank. Then, the second batch of wort, cooled to 20°C, is sent into the fermentation tank to complete the second inoculation. The fermentation tank is filled with both batches of wort. S4c: Main fermentation stage: Main fermentation is carried out by controlling the temperature of the fermenter at 22℃; when the sugar content of the fermentation broth drops to 4-5°P, the tank is sealed for diacetyl reduction, and the tank pressure is controlled at 0.1-0.12MPa. S4d: Diacetyl reduction and cooling: Diacetyl value was measured on the 3rd day of reduction. When the diacetyl content was ≤0.08mg / L, the temperature was reduced to 6℃ at a rate of 0.2℃ / h. S4e: Transferring fermentation broth to a standby fermentation tank at 6℃: Before transferring, the standby fermentation tank is pressurized with CO2 back pressure to 0.02-0.03MPa. After the transfer, the pressure of the standby fermentation tank is controlled to 0.10-0.12MPa. S4f: Storage stage: After racking, the fermentation liquid in the standby fermentation tank is cooled to -1 to 0℃ at a rate of 0.1℃ / h, and the storage time is >14 days; S4g: Pre-filling treatment: Determine whether to centrifuge based on the clarity of the fermentation broth, and then fill.

[0035] The beneficial effects of the above technical solution are as follows: Employing a moisture-conditioning and pulverizing process with roller gaps controlled at 0.35-0.40 mm, combined with staged pre-wetting, slurry conditioning, and rinsing, ensures effective malt crushing and full starch exposure while avoiding filtration difficulties and wort turbidity caused by excessively fine grinding. Precise control of water volume and temperature at different stages ensures a stable mash temperature of 44℃ during feeding, providing stable starting conditions for subsequent staged heating and saccharification.

[0036] Staged temperature-controlled saccharification ensures enzyme activity: the 44℃ holding stage promotes protein rest and increases the low-molecular-weight nitrogen content in the wort; the 55-65℃ stage optimizes starch gelatinization and saccharification, increasing the proportion of fermentable sugars; and the 72℃ holding stage controls dextrin content, balancing the beer's body and fermentation level. The final mash pH is stabilized at 5.4-5.6, providing an ideal base environment for subsequent fermentation and improving the overall quality and consistency of the wort.

[0037] A phased hop addition and boiling process efficiently balances bitterness and aroma. By adding hops in three stages (bitter hops at the initial boil, aroma hops in the middle stage, and aroma hops before swirl settling), it ensures full isomerization of α-acids, efficiently utilizes bitter substances, reduces essential oil volatilization, and maximizes the preservation of hop aroma. During the boiling stage, gypsum and calcium chloride are added to stabilize the wort pH and ionic composition. Combined with the addition of zinc ions, this provides ample trace elements for subsequent yeast fermentation, enhancing the beer's flavor harmony and fermentation stability.

[0038] The dual-strain synergistic fermentation significantly enhances flavor and fermentation efficiency. This method combines the advantages of strain one (rapid sugar reduction and strong diacetyl reduction) with strain two (strong ester production and rich ester aroma): In the early stages, a strain with high sugar-reducing and diacetyl-reducing capabilities rapidly lowers sugar content and controls diacetyl levels, shortening the fermentation cycle; in the later stages, a strain with strong ester production enhances the formation of flavor compounds such as 4-vinylguaiacol, imparting typical ester and clove aromas to the beer. Combined with secondary inoculation and temperature control, this process ensures fermentation efficiency while significantly improving the beer's flavor profile and mouthfeel richness.

[0039] Example 2: Based on Example 1, before mass production of S2, a conductivity-pH acidification benchmark strategy is determined. The conductivity-pH acidification benchmark strategy is a three-dimensional correspondence of "conductivity range, pH range, and benchmark lactic acid addition rate range". S2 includes: S21: Add the malt mash to the saccharification pot. After the malt mash in the saccharification pot is added, keep the temperature of the malt mash constant at the first holding temperature. Add edible gypsum and edible calcium chloride in sequence and stir. During the stirring process, periodically check the conductivity of the mixture until the conductivity stabilizes. When the conductivity stabilizes, check and determine the actual stable conductivity and the actual stable pH. S22: Determine the initial lactic acid addition rate based on the actual stable conductivity and actual stable pH and the pH acidification benchmark strategy of conductivity. Keep stirring and start adding edible lactic acid based on the initial lactic acid addition rate until the initial lactic acid addition time. Then, detect the pH at the end of the initial lactic acid addition time to determine the initial pH change rate and detect the conductivity. Based on the initial pH change rate and the conductivity at the end of the initial lactic acid addition time, determine the optimized lactic acid addition rate. Keep stirring and complete the addition of lactic acid based on the optimized lactic acid addition rate. S23: Continue with the segmented temperature-increase saccharification process.

[0040] This embodiment is executed once when there are large fluctuations in raw materials and water quality (such as when raw materials and water quality are changed batches), and then when the fluctuations in raw materials and water quality are small, the lactic acid addition rate determined for the corresponding batch is used, or it is executed periodically in the same batch of production; 1. The process of determining the conductivity-pH acidification baseline strategy: After selecting representative malts from different sources in actual production and performing a moisture conditioning and pulverizing process, gypsum and calcium chloride were added according to the process and stirred until the conductivity stabilized. The stable conductivity of the wort was then measured, and the wort was divided into several conductivity ranges according to the actual value of the stable conductivity, such as low, medium and high conductivity ranges. Several representative raw materials were selected for each conductivity range to conduct experiments.

[0041] Gradient test: For each group of raw materials, a gradient acidity adjustment test was conducted after saccharification and feeding. After feeding, gypsum and calcium chloride were added according to the process, and stirred until the conductivity stabilized. The actual stable conductivity and actual stable pH were recorded at this time. Lactic acid was added at different lactic acid addition rates until the amount of lactic acid required by the process was reached. The changes in conductivity and pH over time were recorded in real time. The addition rate that met the target conditions was selected as the benchmark lactic acid addition rate range under this condition (i.e., the qualified addition rate of lactic acid).

[0042] For representative raw materials in each of the above stable conductivity ranges, repeat gradient tests, prioritizing the most commonly used conductivity and pH range combinations in production. Other ranges can be calibrated as needed.

[0043] All experimental data were compiled, and a three-dimensional correspondence (mapping table / relationship table) was established for "conductivity range, pH range, and baseline lactic acid addition rate range" as the standard basis for acid adjustment in production.

[0044] The target conditions include: Stable pH change rate: During the acid adjustment process, the actual measured average pH change rate deviates from the target pH change rate within ±10%; Target pH change rate range: The pH at the end of the acid adjustment process can accurately fall into the target pH range of the end of the acid adjustment process, and the total acid adjustment time meets the pH change rate range required by the process. The pH at the acidification endpoint must fall precisely within the target pH range required by the process. The target pH range is a pre-set pH control range for the acidification endpoint based on the requirements of the beer brewing process; a typical target pH range for the acidification endpoint is 5.5-5.7. During mashing, as the proteins and starches in the malt undergo enzymatic hydrolysis, the wort pH will naturally decrease, ultimately meeting the mash pH of 5.4-5.6. A three-dimensional correspondence (mapping table / relationship table) between "conductivity range, pH range, and baseline lactic acid addition rate range", for example: Stable conductivity: After the malt mash in the saccharification pot is fed into the pot, edible gypsum and edible calcium chloride are added in sequence and stirred. During the stirring process, the conductivity of the mixture is periodically measured. When the ratio of the maximum value to the minimum value in the conductivity data obtained from several consecutive measurements (e.g., 3 times) is less than or equal to 1.005, the conductivity is determined to be stable. The conductivity value measured at this time is the actual stable conductivity. When the conductivity is determined to be stable, the pH is measured to obtain the actual stable pH. 2. Determine the initial lactate addition rate based on the actual stable conductivity, actual stable pH, and conductivity-pH acidification benchmark strategy. Specifically, based on the actual stable conductivity and actual stable pH, determine the three-dimensional correspondence of "conductivity range, pH range, and benchmark lactate addition rate range". Find the benchmark lactate addition rate range that matches the current range of actual stable conductivity and actual stable pH. Take the center value of the matching benchmark lactate addition rate range (e.g., the center value of 67-73 is 70) as the initial lactate addition rate.

[0045] 3. The initial lactic acid addition time is 2-3 min; determine the target pH change rate range corresponding to the conductivity at the end of the initial lactic acid addition time; Initial pH change rate = (pH at the end of the initial lactate addition time - pH at the beginning of the initial lactate addition time) ÷ initial lactate addition time; The optimal lactic acid addition rate was determined based on the initial pH change rate and the conductivity at the end of the initial lactic acid addition period. Specifically: When the initial pH change rate meets the corresponding target pH change rate range, the optimized lactic acid addition rate = the initial lactic acid addition rate; When the initial pH change rate is greater than the upper limit of the corresponding target pH change rate range but less than 1.1 times the upper limit of the corresponding target pH change rate range, the optimized lactic acid addition rate is 0.95 times the initial lactic acid addition rate. When the initial pH change rate is less than the lower limit of the corresponding target pH change rate range but greater than 0.9 times the lower limit of the corresponding target pH change rate range, the optimized lactic acid addition rate is 1.05 times the initial lactic acid addition rate. When the initial pH change rate is greater than 1.1 times or less than 0.9 times the target pH change rate range, it is determined to be an abnormal operating condition. An audible and visual alarm is immediately triggered, lactic acid addition is stopped, and abnormal data is recorded for subsequent investigation of equipment, raw materials, or process problems.

[0046] Electrical conductivity is a crucial indicator of the ionic strength of mash and is strongly correlated with the total amount of buffering substances in the mash. This invention establishes a mapping relationship between 'conductivity range + pH range → baseline lactic acid addition rate' through preliminary experiments, using conductivity as an indirect characterization of buffering capacity to predict the acid addition rate. Then, by obtaining the actual pH change rate through short-term trial acid addition, the predicted results are corrected in a closed-loop manner, thereby accurately adapting to the differences in buffering capacity between different batches of mash. The beneficial effects of the above scheme are as follows: 1. Simultaneously mitigates the impact of fluctuations in water quality and raw materials, providing reliable initial conditions for subsequent acidification: The variety of malt, its solubility, the content of buffer substances, and differences in brewing water all directly affect the conductivity and buffering capacity of the wort. This step, by adding gypsum and calcium chloride and stirring until the conductivity stabilizes, "fixes" the differences brought about by different raw materials and water quality in advance. This ensures that the subsequent acidification stage deals with a wort with a stable ionic composition and a balanced buffer system, avoiding deviations in acidification results caused by fluctuations in water quality or raw materials.

[0047] A stable buffer system provides reliable initial conditions for subsequent acidification: Adding gypsum and calcium chloride allows calcium ions to form buffer pairs with phosphates in the wort, altering its buffering capacity. Measuring pH only after stirring until conductivity is stable ensures that the measured pH and conductivity values ​​accurately reflect the wort's buffering capacity, providing a reliable initial operating condition basis for matching the acidification rate using tables. pH alone cannot fully reflect the wort's buffering capacity; conductivity is a crucial indicator of ionic strength. Simultaneous pH measurement when conductivity is stable allows for the simultaneous acquisition of two key parameters: the wort's acidity / alkalinity and its buffering strength.

[0048] 2. Achieve pre-matching of "raw materials - acid addition rate" to significantly reduce the cost of acid adjustment trial and error: Through the mapping relationship of "conductivity range + pH range → benchmark lactic acid addition rate range" established by the gradient test in the early stage, the corresponding acid addition rate can be obtained directly from the table according to the actual state of the current wort during production. There is no need to rely on the operator's experience to repeatedly add acid, which significantly shortens the acid adjustment time and reduces the acid adjustment error rate caused by insufficient experience.

[0049] Different batches of malt and different water qualities can lead to significant differences in the buffering capacity of wort: wort with strong buffering capacity will have a slower pH drop after acidification; wort with weak buffering capacity will have a rapid pH drop after acidification. The reference rate matched by the lookup table is calibrated for different buffering strengths, thus effectively avoiding overflushing or underacidification problems caused by applying the same rate to all wort.

[0050] 3. Initial pH and conductivity alone cannot fully predict the pH trend after acidification. A short trial acidification period of 2-3 minutes prevents irreversible and significant pH deviations while providing a direct reflection of the wort's actual buffering capacity at the current acidification rate. If issues such as pH electrode drift, metering pump malfunction, or uneven wort mixing exist, these will manifest as abnormal pH change rates during the short trial phase. At this stage, before large-scale acidification, the pH remains within a controllable range, facilitating timely problem detection and shutdown for troubleshooting. This avoids the serious consequences of pH loss of control and mash spoilage during subsequent acidification processes.

[0051] The pH change rate during the trial phase is used as the basis for fine-tuning, achieving dual control of "open-loop prediction + closed-loop correction": the initial rate obtained from the table is based on statistics from previous experiments, while the pH change rate during the trial phase reflects the actual performance of the current batch of wort. By comparing the deviations between the two, the rate is fine-tuned, which is equivalent to adding a closed-loop correction on top of the prediction, further improving the precision of acidification control.

[0052] This invention employs a closed-loop control system of "pre-matching the initial rate by looking up a table + probing acid addition to obtain actual buffering performance + tiered fine-tuning," solving the problem that traditional fixed-rate acidification cannot adapt to fluctuations in raw materials and water quality. Especially when the initial conductivity of the wort is at a critical state, relying solely on table prediction is prone to error. This invention, through feedback on the pH change rate during a 2-3 minute probing phase, can quickly identify the actual buffering capacity and precisely fine-tune the acidification rate by ±5%, ensuring that the final pH of the acidification process remains stable within the target range, thus avoiding over- or under-acidification.

[0053] 3. During the acidification stage, the pH is stably controlled within the target range, providing the optimal pH environment for subsequent key reactions such as protein rest, starch gelatinization, and saccharification and enzymatic hydrolysis. This ensures the activity of proteases and amylases, significantly improves the fermentability and extraction rate of the wort, and avoids interference with the saccharification rhythm caused by repeated adjustments during the acidification process. It also ensures the stable execution of process parameters such as segmented heating and heat preservation, thus guaranteeing the quality of the saccharified mash.

[0054] Example 3, based on Example 1 or 2, step S23 includes: S23 includes: Based on the predetermined material circulation rules for the insulation segment and the actual stable conductivity of the current material (for the current batch of material, the actual stable conductivity of S21 determined in the latest execution of Example 2), the target circulation flow rate and target circulation time interval corresponding to the 44℃ insulation stage are determined. The 44℃ insulation is preset for one hour, and the material circulation of the saccharification pot is carried out based on the circulation flow rate and circulation time interval corresponding to the 44℃ insulation stage. The 55℃ heat preservation time is preset for two hours. The material circulation of the saccharification pot is carried out based on the circulation flow rate corresponding to 55℃ determined by the material circulation rules of the heat preservation section. The 65℃ heat preservation time is preset to three hours. The material circulation of the saccharification pot is carried out based on the circulation flow rate and circulation time interval corresponding to 65℃, which are determined by the material circulation rules of the heat preservation section. After holding at 72℃ for 10 minutes, the temperature is increased to 78℃. Stop stirring when the material is circulating.

[0055] 1. The aforementioned material circulation rule for the different insulation sections is a control rule established through experimental verification to address the problem of uneven temperature differences between the upper and lower parts of the saccharification pot during different insulation stages. The specific determination method is as follows: During each heat preservation stage in the saccharification pot, conditions of uneven temperature difference between the upper and lower layers of the mash are artificially created or simulated. Different combinations of circulation flow rates and circulation time intervals are tested. Evaluation indicators include: the absolute value of the temperature difference between the upper and lower layers of the mash ≤ a preset temperature difference threshold (e.g., 0.3℃); and temperature distribution uniformity (defined by the standard deviation σ of the temperature at multiple points within the saccharification pot (e.g., three temperature measuring points evenly distributed in each of the upper, middle, and lower layers) ≤ 0.1℃). Qualified / optimal control parameters (including circulation flow rate, circulation flow rate, and circulation time interval) that meet these evaluation indicators are selected for each stage, forming a phased circulation rule. 44℃ heat preservation stage: In view of the characteristics of weak natural convection and easy temperature difference in mash at low temperature, the corresponding circulation flow rate and circulation time interval are matched, and the temperature difference is eliminated by forced mixing through circulation; the material is circulated intermittently 2 to 3 times. 55℃ Insulation Stage: To address the viscosity changes and potential for localized overheating in the mash during this stage, stable temperature uniformity is maintained by controlling the circulation flow rate; single-cycle material circulation is possible. 65℃ Incubation Stage: To address the increased viscosity of the mash during starch gelatinization, the circulation flow rate is controlled to ensure uniform mixing of the mash during the high-temperature stage and eliminate temperature differences between the top and bottom. Material circulation is performed intermittently 2-4 times. During the production process, material circulation is performed according to preset rules at each heat preservation stage, and stirring is stopped during circulation to avoid mutual interference of the flow field and ensure uniform temperature of the mash.

[0056] 2. Preset duration 1: 10 min; During 44℃ heat preservation: Malt mash is fed and edible gypsum and edible calcium chloride are added within (0 min, 10 min); Several material circulations are performed within (10 min, 20 min), and then edible lactic acid is added; Preset duration 2: 10 min, material circulation at 55℃ within [10 min, 20 min); Preset duration three: 15 min, material circulation at 65℃ within [15 min, 25 min); The duration for each temperature range mentioned above is calculated from the start of the heat preservation period for each temperature range.

[0057] 3.44℃ heat preservation preset time one hour is based on the actual stable conductivity determined by detection: the actual stable conductivity is the conductivity value measured in step S21 after adding edible gypsum and edible calcium chloride to the mash and stirring until it is stable; In the material circulation rules for the heat preservation section, the 44℃ heat preservation stage also marks the benchmark target conductivity range. This range is the target stable conductivity range of the mash in the 44℃ heat preservation stage, which is obtained based on statistics from multiple batches of actual experiments or production data when the rules are constructed. Based on the predetermined material circulation rules for each insulation segment and the actual stable conductivity, the target circulation flow rate and target circulation time interval corresponding to the 44℃ insulation stage are determined, specifically as follows: Retrieve the baseline circulation flow rate and baseline circulation time interval (the target circulation interval) of the 44℃ insulation stage in the material circulation rules of the insulation section. The reference circulating flow rate is corrected based on the actual stable conductivity: when the actual stable conductivity is higher than the upper limit of the actual conductivity range of the reference target, the circulating flow rate is reduced. When the actual conductivity of the target is lower than the upper limit of the target stable conductivity range, the target circulation flow rate during the 44℃ heat preservation stage is equal to the reference circulation flow rate during the 44℃ heat preservation stage. When the actual conductivity of the target is within the range of the target stable conductivity, the target circulation flow rate during the 44℃ heat preservation stage is equal to the reference circulation flow rate during the 44℃ heat preservation stage. The output corrected circulation flow rate is used to perform intermittent material circulation.

[0058] The upper limit overshoot ratio is determined as follows: the absolute difference between the target actual conductivity and the upper limit of the target stable conductivity range ÷ the upper limit of the benchmark target actual conductivity range. When the upper limit exceeds the limit by less than 7%, the target circulation flow rate for the 44℃ insulation stage is equal to the baseline circulation flow rate for the 44℃ insulation stage × 97%. When the upper limit exceeds 7%, the target circulation flow rate for the 44℃ insulation stage is equal to 94% of the baseline circulation flow rate for the 44℃ insulation stage. When the conductivity is too high, reduce the circulation flow rate and extend the interval to reduce the inhibition of protease by local ion enrichment; when the conductivity is too low, use the baseline circulation parameters to achieve a balance between enzyme activity protection and homogenization.

[0059] The beneficial effects of the above scheme are as follows: Traditional saccharification processes generally rely on simple stirring or fixed-flow circulation, which cannot adapt to the differences in the fluidity of mash at different temperature ranges. This can easily lead to "hot at the top and cold at the bottom" or local overheating, resulting in: enzyme activity being destroyed in local high-temperature areas and insufficient reaction in low-temperature areas; ultimately, the composition of fermentable sugars and amino acids in the wort fluctuates greatly, and batch consistency is poor.

[0060] This solution employs customized circulation strategies for different temperature ranges: 44℃ low-temperature range: weak convection in the mash, temperature difference is eliminated through intermittent forced circulation (2-3 times); 55℃ medium-temperature range: moderate viscosity of the mash, uniformity can be maintained with a single circulation; 65℃ heat preservation stage: addressing the issue of increased mash viscosity and easy temperature stratification during starch gelatinization, intermittent material circulation (2-4 times) is used to break down temperature stratification, ensuring uniform mixing of the mash in the high-temperature stage and eliminating temperature differences between the top and bottom. Stirring is stopped during the entire circulation process to avoid mutual interference of the flow fields and ensure uniform temperature of the mash. This solution achieves high-precision control of the absolute value of the temperature difference at multiple points in the saccharification tank ≤0.3℃ and the standard deviation of temperature σ ≤0.1℃. The enzymatic hydrolysis reaction environment of each batch of mash is highly consistent, which greatly improves the stability of wort quality.

[0061] 2.44℃ stage conductivity closed-loop correction achieves a dynamic balance between "ionic environment - enzyme activity protection - homogenization effect": In traditional processes, the addition of gypsum and calcium chloride at 44℃ directly affects the activity and stability of proteases due to fluctuations in mash conductivity. Fixed circulation parameters cannot adapt to different conductivity conditions: when conductivity is too high, local ion enrichment can inhibit protease activity, and excessive circulation can exacerbate uneven ion distribution. This solution uses a real-time conductivity detection + circulation flow rate correction mechanism: based on the deviation between the actual conductivity and the reference range, the circulation flow rate is automatically reduced (3% reduction for deviations <7%, 6% reduction for deviations >7%); when the conductivity is within the reference range, the reference circulation parameters are used to ensure a balance between enzyme activity protection and homogenization effect. This solution avoids excessive inhibition of proteases under high conductivity conditions, ensuring protein decomposition efficiency during the protein resting phase; it maintains stable homogenization effect under low conductivity conditions, avoiding enzyme activity loss caused by local temperature unevenness; and it solves the problem of fixed parameters being unable to adapt due to ionic environment fluctuations caused by batch differences in raw materials.

[0062] Example 4, based on Example 1, involves cooling to the target temperature (wort cooling rate: ≥10 HL / h), with simultaneous oxygenation during the cooling process including: S31: Cool the precipitated wort to 70°C at a cooling rate of 15-18 HL / h, and when the wort is cooled to 80°C, oxygenate to 2-3 ppm at a rate of 0.3-0.6 ppm / min (low rate, small flow rate, to allow oxygen to dissolve slowly, avoid local over-oxygenation, and achieve enzyme pre-activation). S32: Cool the wort to 50°C at a cooling rate of 12-15 HL / h; S33: Cool the wort to “target inoculation temperature + 10°C” at a cooling rate of 10-12 HL / h, and oxygenate to 10-12 ppm at 1.0-1.5 ppm / min; The beneficial effects of the above scheme are as follows: This solution employs a three-stage cooling rate gradient of "rapid cooling - medium cooling - stable cooling" to precisely match the oxygenation rhythm of "pre-oxygenation - oxygenation shutdown - main oxygenation", thereby achieving synergistic optimization of wort dissolved oxygen and oxidation control.

[0063] High-speed cooling of 15-18 HL / h significantly shortens the residence time in the high-temperature section above 80℃. Combined with low-rate, low-flow oxygenation of 0.3-0.6 ppm / min, oxygen dissolves slowly, avoiding local over-oxygenation, and minimizing the oxidation side reactions of polyphenols at high temperatures. At the same time, it consumes easily oxidizable impurities in advance for subsequent low-temperature oxygenation, preventing effective oxygen from being consumed by impurities.

[0064] During the high-risk polyphenol oxidation range of 70℃ to 50℃ when the wort is cooled, a medium-speed cooling rate of 12 to 15 HL / h is used and oxygenation is completely stopped. This avoids thermal shock caused by sudden temperature changes and cuts off the introduction of additional oxygen during this highly sensitive stage, effectively inhibiting the formation of oxidation byproducts and ensuring the flavor stability of the beer.

[0065] A stable cooling rate of 10–12 HL / h is used in the low-temperature section, combined with medium-high speed oxygenation of 1.0–1.5 ppm / min, allowing sufficient time for oxygen to dissolve evenly. This ensures that the dissolved oxygen in the tank is precisely controlled at 10–12 ppm, avoiding foam overflow and uneven dissolved oxygen caused by one-time high-speed oxygenation. It also provides fresh and stable initial oxygen conditions for simultaneous fermentation of two strains, improving the consistency of fermentation and flavor performance.

[0066] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for producing double-strain white beer with optimized saccharification process, characterized in that: Includes the following steps: S1: Malt raw materials are processed using a moisture-adjusting and pulverizing process to obtain malt mash; S2: The malt mash is fed into the saccharification pot and subjected to segmented heating and saccharification to finally obtain saccharified mash: after the malt mash is fed into the saccharification pot, edible lactic acid, edible gypsum and edible calcium chloride are added in sequence. S3: The mashed mash is filtered and washed to obtain mixed wort. The mixed wort is sent to a boiling kettle to complete the boiling and setting process, during which hops are added in batches. The boiled wort is then swirl-sedied and cooled to the target temperature, with oxygenation during the cooling process. S4: Dual-strain fermentation: The cooled wort is sent into a fermentation tank and fermented using dual-strain inoculation; the temperature is controlled according to the process stage, and the main fermentation and diacetyl reduction are completed in sequence.

2. The method for producing double-strain white beer with optimized saccharification process according to claim 1, characterized in that: Screening methods for dual-strain bacteria include: (1) Select multiple candidate brewer's yeast strains as test strains, and conduct fermentation performance tests and ester production ability tests on each strain; (2) Yeast strains that meet the requirements for diacetyl reduction rate and sugar reduction rate are combined with yeast strains that meet the requirements for 4-vinylguaiacol content for mixed fermentation experiments. (3) Based on the data on sugar reduction rate, diacetyl reduction rate and 4-vinylguaiacol content obtained from the mixed fermentation experiment, two yeast strains suitable for brewing white beer were screened.

3. The method for producing double-strain white beer with optimized saccharification process according to claim 2, characterized in that: The fermentation performance test includes: using the CO2 weight loss method, determining the sugar reduction rate by daily weight difference under constant temperature culture conditions of 25℃, and determining the diacetyl reducing capacity.

4. The method for producing double-strain white beer with optimized saccharification process according to claim 2, characterized in that: The ester-producing ability test was conducted by measuring the content of 4-vinylguaiacol generated from the decarboxylation of ferulic acid in the fermentation broth to evaluate the ester-producing ability of the strain.

5. The method for producing double-strain white beer with optimized saccharification process according to claim 1, characterized in that: Before mass production of S2, a conductivity-pH acidification benchmark strategy is determined. The conductivity-pH acidification benchmark strategy is a three-dimensional correspondence of "conductivity range, pH range, and benchmark lactic acid addition rate range". S2 includes: S21: Add the malt mash to the saccharification pot. After the malt mash in the saccharification pot is added, keep the temperature of the malt mash constant at the first holding temperature. Add edible gypsum and edible calcium chloride in sequence and stir. During the stirring process, periodically check the conductivity of the mixture until the conductivity stabilizes. When the conductivity stabilizes, check and determine the actual stable conductivity and the actual stable pH. S22: Determine the initial lactic acid addition rate based on the actual stable conductivity and actual stable pH and the pH acidification benchmark strategy of conductivity. Keep stirring and start adding edible lactic acid based on the initial lactic acid addition rate until the initial lactic acid addition time. Then, detect the pH at the end of the initial lactic acid addition time to determine the initial pH change rate and detect the conductivity. Based on the initial pH change rate and the conductivity at the end of the initial lactic acid addition time, determine the optimized lactic acid addition rate. Keep stirring and complete the addition of lactic acid based on the optimized lactic acid addition rate. S23: Continue with the segmented temperature-increase saccharification process.

6. The method for producing double-strain white beer with optimized saccharification process according to claim 5, characterized in that: The temperature control strategy for the segmented heating saccharification process is as follows: the initial temperature is 44℃ and held for 30 min, then the temperature is increased sequentially at a rate of 1℃ / min to 55℃ and held for 30 min, 65℃ and held for 60 min, 72℃ and held for 10 min, and then the temperature is increased to 78℃.

7. The method for producing double-strain white beer with optimized saccharification process according to claim 6, characterized in that: A material outlet valve is installed at the bottom of the saccharification pot. The material outlet valve is connected to a circulation pipeline, and then a circulation pump returns the mixture discharged from the material outlet valve back to the material distributor at the top of the saccharification pot to achieve material circulation.

8. The method for producing double-strain white beer with optimized saccharification process according to claim 7, characterized in that: S23 includes: Based on the predetermined material circulation rules for the insulation sections and the actual stable conductivity of the current material, the target circulation flow rate and target circulation time interval corresponding to the 44℃ insulation stage are determined. The preset duration of the 44℃ insulation is one hour, and the material circulation of the saccharification pot is carried out based on the circulation flow rate and circulation time interval corresponding to the 44℃ insulation stage. The 55℃ heat preservation time is preset for two hours. The material circulation of the saccharification pot is carried out based on the circulation flow rate corresponding to 55℃ determined by the material circulation rules of the heat preservation section. The 65℃ heat preservation time is preset to three hours. The material circulation of the saccharification pot is carried out based on the circulation flow rate and circulation time interval corresponding to 65℃, which are determined by the material circulation rules of the heat preservation section. After holding at 72℃ for 10 minutes, the temperature is increased to 78℃. Stop stirring when the material is circulating.

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