Brewing process for producing white spirit by fermenting grains with plant probiotics

Abstract

The invention belongs to the technical field of white spirit brewing, and particularly relates to a brewing process for producing white spirit by fermenting grains with plant probiotics, which comprises the following steps: S1, grain pretreatment: soaking, cooking and cooling grain raw materials; s2, main fermentation: inoculating the pretreated grains with distiller's yeast, and performing solid-state or semi-solid-state fermentation in a main fermentation tank; s3, external circulation catalysis: S3.1, signal triggering: monitoring the alcohol concentration of fermented grains in the main fermentation tank in real time, and starting an external circulation catalysis program when the alcohol concentration reaches a triggering threshold value; according to the novel white spirit brewing process based on the HOF material and external circulating catalysis, the fermentation process is intelligently sensed, an optimal catalytic microenvironment is constructed for probiotic enzyme in an in-vitro reactor, the problems of poor alcohol tolerance, uncontrollable flavor and accumulation of defective substances are solved, and the white spirit brewing quality is improved. And the high-quality white spirit with high ester content, low aldehyde content and excellent flavor is successfully brewed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of liquor brewing, and in particular to a brewing process for producing liquor by fermenting grains with plant probiotics. BACKGROUND

[0002] As one of the world's famous distilled liquors, the unique flavor of liquor is mainly derived from the rich esters and other flavor substances produced by microbial metabolism during the fermentation process. In recent years, in order to enrich and optimize the flavor profile of liquor, researchers have attempted to introduce exogenous plant probiotics (such as Lactobacillus plantarum, Staphylococcus yeast, etc.) in addition to traditional koji. These probiotics can produce unique enzymes that catalyze the synthesis of flavor esters that traditional yeast cannot or can produce less, thereby imparting more complex aromas to liquor.

[0003] However, the direct application of plant probiotics in liquor brewing faces a series of fundamental technical bottlenecks, which seriously restricts their effective contribution to flavor:

[0004] 1. The main contradiction is the limitation of alcohol tolerance of plant probiotics. During the main fermentation process, the alcohol content will rapidly increase and exceed 10%vol, which severely inhibits the growth and metabolic activity of most plant probiotics, making it difficult for their unique aroma-producing function to be effectively exerted in the middle and late stages of fermentation.

[0005] 2. The second problem is the uncontrollable generation of flavor. Even if the probiotics survive, their metabolism in the complex main fermentation environment is extremely unstable, resulting in low synthesis efficiency and unpredictability of target flavor substances (especially esters), which cannot stably enhance and shape the product flavor.

[0006] 3. Finally, there is a problem of accumulation of defective flavor substances. Traditional processes lack means to selectively remove impurities during fermentation, resulting in the production of defective substances such as acetaldehyde and higher alcohols that affect taste and post-drinking comfort, affecting the final liquor quality.

[0007] To address the above problems, existing technologies mainly focus on two paths:

[0008] 1. Through strain selection, natural alcohol-tolerant strains are selected or high-tolerance strains are cultivated through adaptive evolution, but this method has a long cycle, high cost, and limited tolerance improvement, and cannot solve the problems of flavor controllability and accumulation of defective substances.

[0009] 2. Through process optimization, such as using segmented fermentation, inoculating probiotics after the main fermentation is completed, but at this time the fermentation system is already under high alcohol and low pH stress, the viability of probiotics is still low, the flavor contribution is minimal, and precise intervention in the flavor synthesis process and in-situ purification of the liquor body cannot be achieved.

[0010] Therefore, there is an urgent need in the art for an innovative brewing process that not only fundamentally circumvents the alcohol tolerance limit, but also enables precise and efficient control over the flavor synthesis pathway, while simultaneously improving the purity of the liquor body, thereby ensuring that the excellent functions of plant probiotics are stably and efficiently exerted, and producing white liquor products with outstanding flavor and top-notch quality. SUMMARY

[0011] To make up for the shortcomings of the prior art, the present application aims to provide a brewing process for producing white liquor by fermenting grains with plant probiotics; the core purpose of this process is to completely circumvent the inhibition of plant probiotic activity in high-alcohol environments through a completely new system design, thereby stably and efficiently utilizing its flavor metabolism function to produce white liquor products with rich flavor and excellent quality.

[0012] The technical solution adopted by the present application to solve its technical problems is: the brewing process for producing white liquor by fermenting grains with plant probiotics, which comprises the following steps:

[0013] S1. Grain pretreatment: soaking, cooking, and cooling the grain raw materials;

[0014] S2. Main fermentation: introducing the pretreated grains into the starter and placing them in the main fermentation tank for solid or semi-solid fermentation;

[0015] S3. External circulation catalysis:

[0016] S3.1 Signal triggering: real-time monitoring of the alcohol concentration of the fermentation grains in the main fermentation tank, and starting the external circulation catalysis program when the alcohol concentration reaches the triggering threshold;

[0017] S3.2 Microenvironment reconstruction and dual-function synergistic treatment: pumping part of the fermentation grains into an external circulation reactor, and maintaining the internal microenvironment of the reactor at a condition suitable for catalysis through a regulation unit; under this condition, using the hydrogen-bonded organic framework-based dual-function synergist loaded in the reactor to simultaneously catalyze flavor substance synthesis and adsorb carbonyl compounds and higher alcohols in the fermentation grains;

[0018] S3.3 Material reflux: returning the catalyzed and adsorbed fermentation grains to the main fermentation tank;

[0019] S4. Post-treatment: after the main fermentation is completed, distilling, aging, and blending the fermentation grains to obtain the finished white liquor.

[0020] In the present application, in step S3.1, the real-time monitoring is realized by an online alcohol concentration sensor, and the monitoring data is transmitted to a PLC (programmable logic controller) in real time, and the PLC is used to determine whether the trigger threshold is reached and automatically start the control system of the circulating pump and the external reactor.

[0021] Preferably, the trigger threshold is 8%vol to 12%vol of alcohol concentration.

[0022] Preferably, the trigger threshold is 10%vol in the present application.

[0023] Preferably, in step S3.2, the control unit comprises: maintaining the alcohol concentration in the circulating reactor at ≤8%vol by injecting sterile cooled grain lees.

[0024] In the present application, the volume ratio of the injected sterile cooled grain lees to the pumped fermented grain is 5% to 10%.

[0025] Preferably, in step S3.2, the control unit comprises: passing a mixed gas composed of 96%N2 and 4%H2, and using a palladium / carbon catalyst to stabilize the internal ORP (oxidation-reduction potential) of the circulating reactor in the range of -100mV to -250mV.

[0026] In the present application, an ORP sensor and a gas flow meter are arranged in the circulating reactor to form a closed-loop control circuit to maintain the stability of the ORP value.

[0027] Preferably, the hydrogen-bonded organic framework-based bifunctional synergist is HOF-NKU-1-based enzyme-adsorption bifunctional synergist; the plant probiotic key metabolic enzyme is composed of esterase and alcohol dehydrogenase, and the activity unit ratio of esterase to alcohol dehydrogenase is (1.5:1) to (4:1).

[0028] In the present application, the plant probiotic key metabolic enzyme is fixed in the inner pore of the HOF-NKU-1-based bifunctional synergist through hydrogen bonding.

[0029] Preferably, the surface of the HOF-NKU-1-based enzyme-adsorption bifunctional synergist is modified with cell wall polysaccharide derived from Lactobacillus plantarum, and the modification amount is 0.3%-0.5% of the mass of the HOF-NKU-1 carrier.

[0030] In the present application, the surface modification is realized by covalent coupling method.

[0031] Preferably, the circulating reactor is a jacketed temperature-controlled stainless steel container, which is internally provided with multiple layers of supports to fill the HOF-NKU-1-based enzyme-adsorption bifunctional synergist, and the internal temperature of the circulating reactor is maintained at 33°C to 37°C during operation.

[0032] In the present application, the distance between the position where the material flows back to the main fermentation tank and the position where the fermented grains are pumped out is greater than 2 / 3 of the diameter of the main fermentation tank.

[0033] Preferably, the enzyme activity retention rate of the HOF-NKU-1-based enzyme-adsorption bifunctional synergist is ≥95%, and the adsorption capacity for acetaldehyde is ≥30 mg / g; and / or, after the step S3.2 treatment, the concentration of acetaldehyde in the fermented grains is ≤30 mg / L.

[0034] In the present application, the inner layer pore diameter of the HOF-NKU-1-based bifunctional synergist is 2-5 nm, and the surface layer pore diameter is 0.5-1 nm. The surface layer micropores utilize size exclusion effect to effectively block the contact of larger ester molecules with the adsorption sites while adsorbing acetaldehyde, thereby avoiding the loss of target flavor substances.

[0035] Preferably, in step S4, the distillation process controls the temperature to be 78-85℃, and discards the first 5% of the initial distillate and the last 10% of the tail distillate, and collects the middle fraction with an alcohol content of 50-60%vol as base liquor.

[0036] In the present application, the base liquor needs to be aged in a pottery jar in a cool place for at least 3 months to promote the fusion and mellowing of flavor substances.

[0037] Preferably, a white liquor is prepared by the above-mentioned any one of the brewing processes, and the total content of ethyl acetate and ethyl lactate in the white liquor is not less than 2200 mg / L, the ester alcohol ratio is greater than 1.8, and the acetaldehyde content is less than 20 mg / L.

[0038] In the present application, the total amount of higher alcohols in the white liquor is less than 350 mg / L, and the liquor body has a unique aroma profile that can be recognized as originating from the specific plant probiotic.

[0039] The beneficial effects of the present application are as follows:

[0040] 1. The brewing process for producing white liquor by fermenting grains with plant probiotics according to the present application completely solves the industry problem that probiotic live bacteria cannot survive in a high-alcohol main fermentation environment by providing a physical isolation and controllable low-alcohol-concentration in-vitro reactor for the aroma-producing function of probiotics.

[0041] 2. The brewing process for producing white liquor by fermenting grains with plant probiotics according to the present application provides a stable and optimal catalytic microenvironment (optimal pH, ORP, temperature) in the in-vitro reactor, which makes the catalytic efficiency of immobilized enzymes much higher than that in the fluctuating environment of the main tank, and enables precise control of the flavor synthesis pathway by controlling the parameters of the reactor.

[0042] 3. The brewing process for producing liquor by fermenting grains with plant probiotics according to the present application, the HOF bifunctional material can catalyze the production of aroma while adsorbing and removing acetaldehyde, furfural and other defect flavor substances and part of fusel oil in situ, thereby improving the purity and drinking comfort of the liquor from the source and realizing the synergy of aroma enhancement and harm reduction.

[0043] 4. The brewing process for producing liquor by fermenting grains with plant probiotics according to the present application, which does not depend on screening specific alcohol-tolerant strains and can be widely applied to various plant probiotics with excellent aroma-producing characteristics but poor alcohol tolerance, thereby developing diversified flavor liquor. BRIEF DESCRIPTION OF DRAWINGS

[0044] The present application will be further described below in conjunction with the drawings.

[0045] Figure 1 is the overall flow chart of the brewing process according to the present application. DETAILED DESCRIPTION

[0046] In order to make the technical means, creative features, purposes and effects achieved by the present application easy to understand, the present application will be further described below in conjunction with specific embodiments.

[0047] Common conditions:

[0048] The same batch of sorghum and rice (mass ratio 7:3) was used in all experiments, and the same conditions were used for soaking, cooking and cooling pretreatment. The main fermentation was carried out in the same size fermenter, and the same batch of Qingxiang Daqu was used. The distillation conditions for post-treatment were unified at 80°C, and the first 5% of the distillate and the last 10% of the distillate were discarded. The 55-60% vol middle fraction was collected as base liquor for detection.

[0049] Test items and methods:

[0050] Total ester content (mg / L): chemical titration method (national standard GB / T10345-2007) was used.

[0051] Ester alcohol ratio: the mass ratio of total ester content to total higher alcohol content (including isopentyl alcohol, isobutyl alcohol, etc.) was calculated.

[0052] Acetaldehyde content (mg / L): gas chromatography method (headspace sampling) was used.

[0053] Total amount of higher alcohols (mg / L): gas chromatography method was used to add the main higher alcohol components.

[0054] Sensory evaluation: a sensory evaluation team consisting of 5 experienced wine tasters was formed to conduct blind evaluation and scoring (full score 10) on the aroma purity, taste and overall quality of the base liquor.

[0055] Examples, comparative examples and results

[0056] Example 1: The best scheme of the present application

[0057] Process: Complete process of the present application. External circulation triggered when alcohol concentration reaches 10%vol. HOF-NKU-1 bifunctional synergist (fixed esterase and alcohol dehydrogenase, activity ratio 2:1) used. Control in circulating reactor: alcohol ≤6%vol, ORP=-200mV, temperature 35℃.

[0058] Results:

[0059] Total ester content: 2450mg / L

[0060] Ester alcohol ratio: 2.1

[0061] Acetaldehyde content: 15mg / L

[0062] Total amount of higher alcohols: 320mg / L

[0063] Sensory evaluation score: 9.2 points (aroma rich, strong layers, clean sweet taste)

[0064] Comparative Example 1: Without any optimization (traditional process control)

[0065] Process: Only main fermentation, without adding any exogenous enzyme or adsorbent, without external circulation.

[0066] Results:

[0067] Total ester content: 720mg / L

[0068] Ester alcohol ratio: 0.6

[0069] Acetaldehyde content: 75mg / L

[0070] Total amount of higher alcohols: 480mg / L

[0071] Sensory evaluation score: 6.5 points (single aroma, obvious spicy and impurity)

[0072] Comparative Example 2: Only adding free enzymes (simulating the simplest enhanced process)

[0073] Process: At the beginning of the main fermentation, an equal amount of free esterase and alcohol dehydrogenase is directly added to the main fermentation tank. No circulation, no immobilization, no adsorption.

[0074] Results:

[0075] Total ester content: 850mg / L

[0076] Ester alcohol ratio: 0.7

[0077] Acetaldehyde content: 65mg / L

[0078] Total higher alcohols: 460 mg / L

[0079] Sensory evaluation score: 6.8 (slightly improved compared with traditional process, still obvious defects)

[0080] Comparative Example Three: external circulation system, but using ordinary immobilized enzyme (no adsorption function)

[0081] Process: external circulation system, trigger conditions same as Example One. But the circulating reactor is loaded with the same enzyme preparation fixed on ordinary porous silica gel.

[0082] Results:

[0083] Total ester content: 2100 mg / L

[0084] Ester alcohol ratio: 1.9

[0085] Acetaldehyde content: 55 mg / L

[0086] Total higher alcohols: 350 mg / L

[0087] Sensory evaluation score: 7.8 (fragrance is acceptable, but roughness and irritation can be perceived)

[0088] Comparative Example Four: external circulation system, but using ordinary adsorbent (no catalytic function)

[0089] Process: external circulation system, trigger conditions same as Example One. But the circulating reactor is loaded with ordinary activated carbon.

[0090] Results:

[0091] Total ester content: 780 mg / L

[0092] Ester alcohol ratio: 0.65

[0093] Acetaldehyde content: 35 mg / L

[0094] Total higher alcohols: 340 mg / L

[0095] Sensory evaluation score: 7.0 (although the wine body is clean, the fragrance is weak and the flavor is flat)

[0096] Example Two: change trigger point (8% vol)

[0097] Process: same as Example One, only change the trigger alcohol concentration to 8% vol.

[0098] Results:

[0099] Total ester content: 2300 mg / L

[0100] Ester alcohol ratio: 2.0

[0101] Acetaldehyde content: 18 mg / L

[0102] Total higher alcohols: 330 mg / L

[0103] Sensory evaluation score: 9.0

[0104] Example Three: Change in enzyme source

[0105] Process: same as Example One, but the plant probiotic enzyme source was changed to grape skin yeast, with a ratio of esterase to alcohol dehydrogenase activity units of 3:1.

[0106] Results:

[0107] Total ester content: 2150 mg / L

[0108] Ester to alcohol ratio: 1.85

[0109] Acetaldehyde content: 17 mg / L

[0110] Total higher alcohols: 325 mg / L

[0111] Sensory evaluation score: 8.9 (with a pleasant fruity aroma)

[0112] Conclusion:

[0113] 1. Only the complete technical solution of the present application (Example One) can simultaneously and synergistically achieve high esters, high ester to alcohol ratio, low acetaldehyde, low higher alcohols, and the highest sensory evaluation score.

[0114] 2. Any solution that separates the "external circulation system" from the "HOF dual-function material" (Comparative Examples Three and Four) has obvious shortfalls, proving that the two are an organic whole that cannot be separated and promote each other.

[0115] 3. The solution of the present application is significantly better than the traditional process (Comparative Example One) and the simple enhanced process (Comparative Example Two).

[0116] 4. The present application can maintain excellent and stable results within a certain parameter range (Example Two) and with different sources of bacteria (Example Three), proving its robustness and universality.

[0117] Finally, it should be noted that the above examples are used to illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced with equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A brewing process for producing baijiu by fermenting grains with plant probiotics, characterized in that, The method comprises the following steps: S1. Grain pretreatment: soaking, cooking, and cooling the grain raw material; S2. Main fermentation: introducing the pretreated grain into the starter and placing it in a main fermentation tank for solid or semi-solid fermentation; S3. External circulation catalysis: S3.1 Signal triggering: real-time monitoring of the alcohol concentration of the fermentation starter in the main fermentation tank, and when the alcohol concentration reaches the triggering threshold, the external circulation catalysis program is started; S3.2 Microenvironment reconstruction and dual-function synergistic treatment: pumping part of the fermentation starter into an external circulation reactor, and maintaining the internal microenvironment of the circulation reactor at a condition suitable for catalysis through a regulation unit; under this condition, a hydrogen-bonded organic framework-based dual-function synergist loaded in the circulation reactor is used to simultaneously catalyze the synthesis of flavor substances and adsorb carbonyl compounds and higher alcohols in the fermentation starter; S3.3 Material reflux: returning the fermentation starter treated by catalysis and adsorption to the main fermentation tank; S4. Post-treatment: after the main fermentation is completed, the fermentation starter is distilled, aged, and blended to obtain the finished liquor.

2. The brewing process for producing Baijiu from fermented grains with plant probiotics according to claim 1, characterized in that, The triggering threshold is an alcohol concentration of 8%vol to 12%vol.

3. The brewing process for producing liquor from fermented grains with plant probiotics according to claim 1, characterized in that, In step S3.2, the regulation unit comprises maintaining the alcohol concentration in the circulation reactor at ≤8%vol by injecting sterile cooled grain starter.

4. The brewing process for producing Baijiu from fermented grains with plant probiotics according to claim 3, characterized in that, In step S3.2, the regulation unit comprises stabilizing the internal redox potential of the circulation reactor at the interval of -100mV to -250mV by introducing a mixed gas composed of 96%N2 and 4%H2 and using a palladium / carbon catalyst.

5. The brewing process for producing Baijiu from fermented grains with plant probiotics according to claim 1, characterized in that, The hydrogen-bonded organic framework-based dual-function synergist is HOF-NKU-1-based enzyme-adsorption dual-function synergist; the key metabolic enzymes of the plant probiotic bacteria are composed of esterase and alcohol dehydrogenase, and the activity unit ratio of esterase to alcohol dehydrogenase is (1.5:1) to (4:1).

6. The brewing process for producing liquor from fermented grains with plant probiotics according to claim 5, characterized in that, The surface of the HOF-NKU-1-based enzyme-adsorption dual-function synergist is modified with cell wall polysaccharide derived from Lactobacillus plantarum, and the modification amount is 0.3%-0.5% of the mass of the HOF-NKU-1 carrier.

7. The brewing process for producing liquor from fermented grains with plant probiotics according to claim 6, characterized in that, The circulation reactor is a jacketed temperature-controlled stainless steel container, which is internally provided with multiple layers of supports to fill the HOF-NKU-1-based enzyme-adsorption dual-function synergist, and the internal temperature of the circulation reactor is maintained at 33°C to 37°C when it is working.

8. The brewing process for producing liquor from fermented grains with plant probiotics according to claim 7, characterized in that, The enzyme activity retention rate of the HOF-NKU-1-based enzyme-adsorption dual-function synergist is ≥95%, and the adsorption capacity for acetaldehyde is ≥30mg / g; and / or, after step S3.2, the concentration of acetaldehyde in the fermentation starter is ≤30mg / L.

9. The brewing process for producing Baijiu from fermented grains with plant probiotics according to claim 1, characterized in that, In step S4, the distillation process controls the temperature at 78-85°C, and the first 5% of the initial distillate and the last 10% of the tail distillate are discarded, and the middle fraction with an alcohol content of 50-60%vol is collected as base liquor.

10. A distilled spirit, characterized by, The liquor is prepared by the brewing process of fermenting grain with plant probiotic bacteria according to any one of claims 1 to 9, and the total content of ethyl acetate and ethyl lactate in the liquor is not less than 2200mg / L, the ester / alcohol ratio is greater than 1.8, and the acetaldehyde content is less than 20mg / L.

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