Preparation method of low-bitterness high-aroma yellow peach craft beer

Abstract

The invention discloses a preparation method of low-bitterness high-aroma yellow peach craft beer, and belongs to the technical field of beer brewage, and the preparation method comprises the following steps: yellow peach pretreatment: yellow peach pulp is subjected to liquid nitrogen freezing and micro-explosion, and then is centrifuged to obtain yellow peach juice; malt saccharification: crushing barley malt and wheat malt, adding water, mixing, carrying out gradient variable temperature saccharification, filtering to obtain wort and hops, boiling, adding bitter hops and fragrant hops into the wort by stages, adding water, boiling, and cooling to room temperature; dynamic dissolved oxygen fermentation: inoculating saccharomyces cerevisiae into the wort for main fermentation, and then adding yellow peach juice and lactobacillus plantarum for co-fermentation to obtain fermentation liquor; post-treatment: carrying out ultrahigh pressure homogenization and ceramic membrane cold filtration treatment on the fermentation liquid to obtain the yellow peach craft beer. Through liquid nitrogen freezing micro-explosion pretreatment, gradient variable-temperature saccharification and hops staged adding technologies, the problems that traditional fruit beer is abrupt in bitter taste, insufficient in fruity flavor, prone to inactivation of active ingredients and the like are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of beer brewing, and specifically relates to a method for preparing low-bitter and high-fragrant yellow peach craft beer. Background Art

[0002] In recent years, as consumers' demand for healthier diets and more diverse flavors increases, the market for fruit beer, a beverage that combines the taste of beer with the flavor of fruit, has continued to expand. However, traditional fruit beer production still faces many technical bottlenecks, which seriously restrict product quality and market competitiveness. The main limitations of traditional fruit beer production technology are as follows:

[0003] Single flavor: Adding juice at one time results in poor fusion of fruity and malty aromas, and insufficient formation of esters;

[0004] Loss of active ingredients: The hot juicing process destroys heat-sensitive ingredients such as yellow peach polyphenols and vitamin C;

[0005] Short shelf life: Pulp sedimentation and microbial contamination result in high turbidity and a short shelf life (usually ≤ 6 months);

[0006] Abrupt bitterness: The hops are added in a single way, the bitterness value (IBU) is high, the bitterness and fruity aroma are unbalanced, and the taste is not harmonious.

[0007] Existing technologies, such as CN109439478A, propose the concept of yellow peach beer, but they use conventional enzymatic hydrolysis and single-stage fermentation, resulting in low polyphenol extraction rates (≤90 mg / 100 mL), high diacetyl residues (0.06 mg / L), a lack of control over the balance between bitterness and fruity aroma, and reliance on traditional filtration techniques. Turbidity levels are ≥0.7 EBC, and shelf life is ≤6 months. Therefore, an innovative process is urgently needed that can simultaneously increase the active ingredient content, improve flavor profile, and extend shelf life. Summary of the Invention

[0008] In response to the above problems, the present invention provides a method for preparing low-bitter and high-aroma yellow peach craft beer. Through liquid nitrogen freezing micro-explosion pretreatment, gradient temperature saccharification and staged hop addition technology, the problems of traditional fruit beer such as abrupt bitterness, insufficient fruit aroma, and easy inactivation of active ingredients are solved.

[0009] To achieve the above object, the technical solution adopted by the present invention is:

[0010] A method for preparing low-bitter and high-flavor yellow peach craft beer comprises the following steps:

[0011] Step 1, yellow peach pretreatment: the yellow peach pulp is frozen and slightly exploded with liquid nitrogen, and then centrifuged to obtain yellow peach juice;

[0012] Step 2, malt saccharification: crush barley malt and wheat malt, add water and mix, perform gradient temperature saccharification and filter to obtain wort;

[0013] Step 3, hop boiling: add bitter hops and aroma hops to the wort in stages, add water and boil for 50-60 minutes, then cool to room temperature;

[0014] Step 4, dynamic dissolved oxygen fermentation: inoculating brewer's yeast into the wort treated in step 3 for main fermentation, fermenting for 4-5 days at a temperature of 12-15° C., with dissolved oxygen ≤ 0.3 mg / L in the first 48 hours and increasing the dissolved oxygen to 0.8-1.0 mg / L in the later period, then adding the yellow peach juice obtained in step 1 and Lactobacillus plantarum for co-fermentation to obtain a fermentation broth;

[0015] Step 5, post-processing: the fermentation liquid obtained in step 4 is subjected to ultra-high pressure homogenization and ceramic membrane cold filtration to obtain yellow peach craft beer.

[0016] In the above technical scheme, the extremely rapid freezing in liquid nitrogen micro-explosion causes the cell walls of yellow peaches to rupture due to the expansion of ice crystals, and the cell contents are easier to release after thawing. Gradient temperature saccharification is adopted to optimize the action conditions of amylase and saccharifying enzyme, increase the fermentable sugar ratio of wort, and add hops in stages to release bitter α-acids and aromatic essential oil components at different stages of boiling. In dynamic dissolved oxygen fermentation, low dissolved oxygen in the early stage of main fermentation promotes yeast esterase activity, and high dissolved oxygen in the later stage accelerates diacetyl reduction. Co-fermentation regulation is also adopted. The acid production of Lactobacillus plantarum reduces the pH to 3.6-3.8, inhibits miscellaneous bacteria and produces fruity substances such as ethyl acetate. Ultra-high pressure homogenization is used to destroy the yeast cell wall and polysaccharide network structure, and ceramic membrane cold filtration removes impurities and retains active ingredients.

[0017] In a preferred embodiment, the liquid nitrogen freezing micro-explosion process in step 1 is as follows: fresh yellow peach pulp is first quickly frozen in liquid nitrogen at -196-190°C for 5-10 minutes, and then rapidly heated to 20-25°C for thawing. In this technical solution, during the quick-freezing stage, the ultra-low temperature of liquid nitrogen causes the water in the cells to instantly crystallize, forming micron-sized ice crystals that pierce the cell walls. After the ice crystals melt, the osmotic pressure inside and outside the cells is unbalanced, and the contents (polyphenols, pectin) are quickly released.

[0018] In a preferred embodiment, the yellow peach juice obtained in step 1 is further subjected to an enzymatic hydrolysis treatment, first adding 0.5-1.0 U / g laccase, controlling the pH value to 5.0-5.3, and reacting at 35-40°C for 30-35 minutes, and then adding 1.5-2.5 U / g xylanase, controlling the pH value to 6.0-6.5, and reacting at 50-55°C for 1.5-2.0 hours. This technical solution first adds laccase treatment to oxidatively decompose the lignin-polyphenol complex in the yellow peach cell wall, severing covalent bonds to release bound polyphenols, and then adding xylanase to specifically hydrolyze the xylan in the hemicellulose, destroying the cell wall network structure, and synergistically releasing soluble sugars and pectin.

[0019] In a preferred embodiment, the gradient temperature saccharification in step 2 is carried out in three stages: 40-45°C, 60-63°C, and 72-75°C, with each stage maintained for 20 minutes. This technical solution activates β-glucanase to decompose malt colloids and reduce wort viscosity at 40-45°C, promotes α-starch to hydrolyze long-chain starch into dextrins at 60-63°C, and strengthens saccharifying enzymes (β-amylase and limit dextrinase) to produce maltose and glucose at 72-75°C.

[0020] In a preferred embodiment, the phased addition of bitter and flavor hops in step 3 means that 70% of the bitter hops are added 45 minutes before the end of boiling, and 30% of the flavor hops are added 15 minutes before the end of boiling. This technical solution allows the bitter hops to be boiled for a longer period of time, allowing the α-acids in the hops to be fully isomerized into iso-α-acids, which contribute to the bitterness and are the main source of beer bitterness. Boiling the flavor hops for a shorter period of time reduces the volatilization of aroma components (such as terpenes and esters), preserving the unique floral and fruity aroma of the hops.

[0021] In a preferred embodiment, the inoculum amount of Lactobacillus plantarum in step 4 is 5-10% of the yeast mass, and fermentation is carried out at 18-20°C for 3-4 days until the pH drops to 3.6-3.8. This technical solution utilizes Lactobacillus plantarum to metabolize maltose to produce lactic acid, which lowers the pH and inhibits spoilage bacteria. This creates a suitably acidic environment that promotes yeast maltase activity and increases fermentation. Furthermore, the lactic acid bacteria metabolites and yellow peach aroma compounds create a synergistic flavor effect.

[0022] In a preferred embodiment, the ultrahigh pressure homogenization pressure in step 5 is 200 MPa, and the ceramic membrane filtration process is performed using a 0.45 μm ceramic membrane at 2-4°C for cold filtration. This technical solution utilizes cavitation and shear forces to break up macromolecular aggregates, while the ceramic membrane traps microorganisms and suspended particles, and the low-temperature operation preserves vitamin C and polyphenols.

[0023] In a preferred embodiment, the yellow peach juice, barley malt, wheat malt, bitter hops, aromatic hops, water, and brewer's yeast are calculated in parts by weight: 2-3 parts, 100-200 parts, 40-60 parts, 0.4-0.6 parts, 0.1-0.3 parts, 500-600 parts, and 0.4-0.6 parts.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) the present invention significantly improves the extraction rate of active ingredients in yellow peach, optimizes the balance between bitterness and fruity aroma, and prolongs the shelf life through liquid nitrogen freezing micro-explosion, gradient temperature saccharification, and staged hop addition processes;

[0025] (2) The present invention uses liquid nitrogen freezing micro-explosion pretreatment to quickly release active ingredients such as polyphenols and pectin in yellow peach cells. Compared with the traditional hot juicing process, this extremely rapid freezing and thawing process can effectively avoid the destruction of heat-sensitive ingredients such as vitamin C and yellow peach polyphenols, and significantly improve the extraction rate of active ingredients.

[0026] (3) During the processing of yellow peach juice, the present invention first adds laccase, which can oxidize and decompose the lignin-polyphenol complex in the yellow peach cell wall, cut the covalent bonds, and release the bound polyphenols. Then, xylanase is added. Xylanase specifically hydrolyzes xylan in hemicellulose and destroys the network structure of the cell wall. The synergistic effect of these two enzymes further releases active ingredients such as soluble sugars and pectin, thereby significantly increasing the content of active ingredients in the yellow peach juice and providing rich nutrients and flavor precursors for the subsequent brewing of beer.

[0027] (4) The present invention adopts a three-stage temperature-variable saccharification process during malt saccharification. This gradient temperature-variable saccharification method optimizes the action conditions of amylase and saccharifying enzyme, increases the proportion of fermentable sugars in the wort, provides a richer substrate for yeast fermentation, is conducive to the production of more flavor substances, and makes the malt aroma of beer more intense;

[0028] (5) The present invention adds bitter hops and aromatic hops in stages during the wort boiling process; this staged addition method achieves a better balance between the bitterness and fruity aroma of the beer, enriches the flavor layering, and avoids the problems of traditional fruit beer with abrupt bitterness and insufficient fruity aroma;

[0029] (6) During the fermentation process, the present invention first inoculates brewer's yeast for main fermentation and adopts a dynamic dissolved oxygen fermentation method. In the early stage, low dissolved oxygen promotes yeast esterase activity, which is conducive to the production of more ester aroma substances; in the later stage, high dissolved oxygen accelerates diacetyl reduction and reduces the residual undesirable flavor substances. Then, yellow peach juice and plant lactobacillus are added for co-fermentation. While inhibiting miscellaneous bacteria, fruity aroma substances such as ethyl acetate are produced, which form a synergistic flavor effect with the yellow peach aroma substances, further enriching the flavor level of the beer, so that the beer has both rich malt and hop aromas and unique fruity aromas, and the flavor is more coordinated;

[0030] (7) In the post-processing stage, the present invention adopts ultra-high pressure homogenization treatment to break up macromolecular aggregates through cavitation effect and shear force, destroy yeast cell walls and polysaccharide network structure, and prevent the formation of precipitation. Subsequently, ceramic membrane cold filtration is adopted. The ceramic membrane can intercept microorganisms and suspended particles and effectively remove impurities. At the same time, low temperature operation retains active ingredients such as vitamin C and polyphenols. This treatment method not only ensures the clarity and stability of beer, but also retains rich nutrients, extends the shelf life of beer, and solves the problem of high turbidity and short shelf life (usually ≤ 6 months) of traditional fruit beer due to pulp precipitation and microbial contamination;

[0031] (8) The brewer's yeast used in the present invention has excellent osmotic pressure tolerance and alcohol tolerance, and can ferment normally in a high-sugar, high-alcohol environment. It also has good low-temperature adaptability and maintains membrane fluidity at low temperatures, ensuring the smooth progress of the fermentation process. The use of this yeast strain for fermentation can efficiently utilize fermentable sugars such as maltose to produce ethanol and carbon dioxide, while also producing rich ester substances, giving the beer a rich fruity and floral aroma. It can also effectively reduce bacterial contamination during the fermentation process, improve the quality stability of the beer, and thus help to extend the shelf life of the beer;

[0032] (9) In the pretreatment of yellow peaches, the present invention not only uses liquid nitrogen freezing micro-explosion, but also uses laccase-xylanase synergistic enzymatic hydrolysis. The traditional enzymatic hydrolysis process is limited by the dense structure of the yellow peach cell wall, which makes it difficult to fully release the active ingredients (such as polyphenols and flavonoids), and the extraction efficiency is limited. However, by extremely rapid freezing and thawing, the macroscopic structure of the cell wall is destroyed, making the contents easier to expose, and further decomposing the lignin and hemicellulose in the cell wall to release the bound active ingredients. The synergistic effect of the two significantly improves the extraction rate of the active ingredients. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solution, the present invention is described in detail below in conjunction with embodiments. The description in this section is only exemplary and explanatory and should not have any limiting effect on the scope of protection of the present invention.

[0034] The source of the brewer's yeast in the following examples is: China Industrial Culture Collection Center (CICC), No.: CICC 1001.

[0035] The strain of Lactobacillus plantarum was obtained from China Industrial Culture Collection Center (CICC), number CICC 23120.

[0036] Example 1:

[0037] A method for preparing low-bitter and high-flavor yellow peach craft beer comprises the following steps:

[0038] Step 1, yellow peach pretreatment: the yellow peach pulp is subjected to liquid nitrogen freezing and micro-explosion, and then the juice is centrifuged to obtain yellow peach juice, wherein the liquid nitrogen freezing and micro-explosion process is as follows: the fresh yellow peach pulp is firstly quick-frozen in -196- liquid nitrogen for 10 minutes, and then rapidly heated to 25°C for thawing, and the yellow peach juice is further subjected to enzymatic hydrolysis treatment, firstly 0.5U / g laccase is added, the pH value is controlled at 5.3, and the reaction is carried out at 35°C for 35 minutes, and then 1.5U / g xylanase is added, the pH value is controlled at 6.0, and the reaction is carried out at 55°C for 1.5 hours;

[0039] Step 2, malt saccharification: 100 kg of barley malt and 52 kg of wheat malt were crushed and mixed with water, and then subjected to gradient temperature saccharification and filtered to obtain the wort. The gradient temperature saccharification was carried out in three stages: 40°C, 63°C, and 72°C, with each stage maintained for 20 minutes.

[0040] Step 3, hop boiling: adding 0.4 kg of bitter hops and 0.3 kg of aroma hops to the wort in stages, adding water and boiling for 50 minutes, and then cooling to room temperature. The staged addition of bitter hops and aroma hops means that 70% of the bitter hops are added 45 minutes after the end of boiling, and 30% of the aroma hops are added 15 minutes after the end of boiling;

[0041] Step 4, dynamic dissolved oxygen fermentation: inoculating 0.4 kg of brewer's yeast into the wort treated in step 3 for main fermentation, fermenting for 5 days at a temperature of 12° C., with a dissolved oxygen concentration of 0.3 mg / L in the first 48 hours, and increasing the dissolved oxygen concentration to 1.0 mg / L in the later period, then adding 2 kg of yellow peach juice obtained in step 1 and 0.04 kg of Lactobacillus plantarum for co-fermentation to obtain a fermentation broth, and fermenting at 18° C. for 4 days until the pH drops to 3.6;

[0042] Step 5, post-processing: the fermentation liquid obtained in step 4 is subjected to ultra-high pressure homogenization and ceramic membrane cold filtration to obtain yellow peach craft beer, the ultra-high pressure homogenization pressure is 200 MPa, and the ceramic membrane filtration treatment is cold filtration at 2°C using a 0.45 μm ceramic membrane.

[0043] Example 2:

[0044] A method for preparing low-bitter and high-flavor yellow peach craft beer comprises the following steps:

[0045] Step 1, yellow peach pretreatment: the yellow peach pulp is subjected to liquid nitrogen freezing and micro-explosion, and then the juice is centrifuged to obtain yellow peach juice, wherein the liquid nitrogen freezing and micro-explosion process is as follows: the fresh yellow peach pulp is firstly quick-frozen in liquid nitrogen at -190°C for 5 minutes, and then rapidly heated to 20°C for thawing, and the yellow peach juice is further subjected to enzymatic hydrolysis treatment, firstly 1.0U / g laccase is added, the pH value is controlled at 5.0, and the reaction is carried out at 40°C for 30 minutes, and then 2.5U / g xylanase is added, the pH value is controlled at 6.5, and the reaction is carried out at 50°C for 2.0 hours;

[0046] Step 2, malt saccharification: 200 kg of barley malt and 40 kg of wheat malt were crushed and mixed with water, and then subjected to gradient temperature saccharification and filtered to obtain the wort. The gradient temperature saccharification was carried out in three stages: 45°C, 60°C, and 75°C, with each stage maintained for 20 minutes.

[0047] Step 3, hop boiling: adding 0.6 kg of bitter hops and 0.1 kg of aroma hops to the wort in stages, adding water and boiling for 60 minutes, and then cooling to room temperature, wherein the staged addition of bitter hops and aroma hops means that 70% of the bitter hops are added 45 minutes after the end of boiling, and 30% of the aroma hops are added 15 minutes after the end of boiling;

[0048] Step 4, dynamic dissolved oxygen fermentation: inoculating 0.6 kg of brewer's yeast into the wort treated in step 3 for main fermentation, fermenting for 4 days at a temperature of 15° C., with a dissolved oxygen concentration of 0.2 mg / L in the first 48 hours, and increasing the dissolved oxygen concentration to 0.8 mg / L in the later period, then adding 3 kg of yellow peach juice obtained in step 1 and 0.06 kg of Lactobacillus plantarum for co-fermentation to obtain a fermentation broth, and co-fermenting at 20° C. for 3 days until the pH drops to 3.8;

[0049] Step 5, post-processing: the fermentation liquid obtained in step 4 is subjected to ultra-high pressure homogenization and ceramic membrane cold filtration to obtain yellow peach craft beer, the ultra-high pressure homogenization pressure is 200 MPa, and the ceramic membrane filtration treatment is cold filtration at 4°C using a 0.45 μm ceramic membrane.

[0050] Example 3:

[0051] A method for preparing low-bitter and high-flavor yellow peach craft beer comprises the following steps:

[0052] Step 1, yellow peach pretreatment: the yellow peach pulp is subjected to liquid nitrogen freezing and micro-explosion, and then the juice is centrifuged to obtain yellow peach juice, wherein the liquid nitrogen freezing and micro-explosion process is as follows: the fresh yellow peach pulp is firstly quick-frozen in liquid nitrogen at -193°C for 6 minutes, and then rapidly heated to 24°C for thawing, and the yellow peach juice is further subjected to enzymatic hydrolysis treatment, firstly adding 0.8U / g laccase, controlling the pH value to 5.2, reacting at 37°C for 32 minutes, then adding 2.0U / g xylanase, controlling the pH value to 6.3, and reacting at 53°C for 1.8 hours;

[0053] Step 2, malt saccharification: 140 kg of barley malt and 50 kg of wheat malt were crushed and mixed with water, and then subjected to gradient temperature saccharification and filtered to obtain the wort. The gradient temperature saccharification was carried out in three stages, 42°C, 61°C, and 74°C, with each stage maintained for 20 minutes.

[0054] Step 3, hop boiling: adding 0.5 kg of bitter hops and 0.2 kg of aroma hops to the wort in stages, adding water and boiling for 55 minutes, and then cooling to room temperature. The staged addition of bitter hops and aroma hops means that 70% of the bitter hops are added 45 minutes after the end of boiling, and 30% of the aroma hops are added 15 minutes after the end of boiling;

[0055] Step 4, dynamic dissolved oxygen fermentation: inoculating 0.5 kg of brewer's yeast into the wort treated in step 3 for main fermentation, fermenting for 5 days at a temperature of 13° C., with a dissolved oxygen concentration of 0.3 mg / L in the first 48 hours, and increasing the dissolved oxygen concentration to 0.9 mg / L in the later period, then adding 2.5 kg of yellow peach juice obtained in step 1 and 0.025 kg of Lactobacillus plantarum for co-fermentation to obtain a fermentation broth, and fermenting at 19° C. for 3 days until the pH drops to 3.7;

[0056] Step 5, post-processing: the fermentation liquid obtained in step 4 is subjected to ultra-high pressure homogenization and ceramic membrane cold filtration to obtain yellow peach craft beer, the ultra-high pressure homogenization pressure is 200 MPa, and the ceramic membrane filtration treatment is cold filtration at 3°C using a 0.45 μm ceramic membrane.

[0057] Comparative Example 1:

[0058] The difference between this comparative example and Example 1 is that the traditional hot juicing process is used in the pretreatment of yellow peaches in step 1. The specific steps are: hot pressing the yellow peach pulp at 80°C for 30 minutes, and centrifuging the juice to obtain yellow peach juice. The other steps are the same as those in Example 1.

[0059] Comparative Example 2:

[0060] The difference between this comparative example and Example 1 is that after obtaining the yellow peach juice, enzymatic hydrolysis is no longer used, and the yellow peach juice is directly used for subsequent co-fermentation. The other steps are the same as those in Example 1.

[0061] Comparative Example 3:

[0062] The difference between this comparative example and Example 1 is that after obtaining the yellow peach juice, enzymatic hydrolysis is carried out using a composite enzymatic hydrolysis of pectinase and cellulase, and pectinase (50°C / 1h) and cellulase (55°C / 2h) are added in sequence, with pectinase:cellulase=1:2. The other steps are the same as those in Example 1.

[0063] Comparative Example 4:

[0064] The difference between this comparative example and Example 1 is that, after obtaining the yellow peach juice, only xylanase is used for enzymatic hydrolysis, and the other steps are the same as those in Example 1.

[0065] Comparative Example 5:

[0066] The difference between this comparative example and Example 1 is that hops are added at one time in step 3, and 0.4 parts of bitter hops and 0.3 parts of aroma hops are both added 50 minutes after the end of boiling. The other steps are the same as those in Example 1.

[0067] Comparative Example 6:

[0068] The difference between this comparative example and Example 1 is that in step 4, common yeast is inoculated, and brewer's yeast freeze-dried powder purchased from Nanjing Convenience Clinic Company, product number BGWW23105, is used to replace the brewer's yeast in Example 1 for fermentation. The other steps are the same as those in Example 1.

[0069] Comparative Example 7:

[0070] The difference between this comparative example and Example 1 is that in step 2, malt saccharification adopts single-stage saccharification without gradient temperature change. Specifically, barley malt and wheat malt are crushed, mixed with water, and then saccharified at a constant temperature of 63°C for 60 minutes, and the wort is filtered. The other steps are the same as in Example 1.

[0071] The craft yellow peach beer obtained above was subjected to chemical testing, and multiple contents were detected by the Folin-Ciocalteu method, bitterness value was detected by spectrophotometry, ester substances were detected by gas chromatography-mass spectrometry, turbidity was detected by EBC turbidimeter method, diacetyl content was detected by catechol method, alcohol content was detected by distillation-density method, and vitamin C retention rate was detected by high performance liquid chromatography. Sensory scoring was performed by standardized sensory evaluation (GB / T 16291-2012 General Rules for Sensory Analysis of Foods) with reference to GB 5009.86-2016 Determination of Ascorbic Acid in Foods, and shelf life was detected by accelerated aging test. The test results are shown in the following table.

[0072] Table 1

[0073]

[0074]

[0075] By comparing the examples with the comparative examples, the liquid nitrogen freezing micro-explosion, enzymatic hydrolysis, gradient saccharification, staged hop addition and the application of preferred brewer's yeast of the present invention significantly improve the active ingredient content, flavor balance and shelf life of yellow peach beer, and the technical effect far exceeds the traditional process.

[0076] It should be noted that, in this article, the terms: include, contain and any other variations are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also includes elements that are inherent to such process, method, article or device. Specific examples are used herein to illustrate the principles and implementation methods of the technical solution of the present invention. The above examples are only used to help understand the method of the present invention and its core idea. The above is only a preferred embodiment of the present invention. It should be pointed out that due to the limitations of textual expression, there are objectively infinite specific structures. For ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements, modifications or changes can be made, and the above technical features can be combined in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the concept and technical solution of the present invention to other occasions without improvement, should be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing low-bitter and high-flavor yellow peach craft beer, characterized in that: The following steps are involved: Step 1, yellow peach pretreatment: the yellow peach pulp is frozen and slightly exploded with liquid nitrogen, and then centrifuged to obtain yellow peach juice; Step 2, malt saccharification: crush barley malt and wheat malt, add water and mix, perform gradient temperature saccharification and filter to obtain wort; Step 3, hop boiling: add bitter hops and aroma hops to the wort in stages, add water and boil for 50-60 minutes, then cool to room temperature; Step 4, dynamic dissolved oxygen fermentation: inoculating brewer's yeast into the wort treated in step 3 for main fermentation, fermenting for 4-5 days at a temperature of 12-15° C., with dissolved oxygen ≤ 0.3 mg / L in the first 48 hours and increasing the dissolved oxygen to 0.8-1.0 mg / L in the later period, then adding the yellow peach juice obtained in step 1 and Lactobacillus plantarum for co-fermentation to obtain a fermentation broth; Step 5, post-processing: the fermentation liquid obtained in step 4 is subjected to ultra-high pressure homogenization and ceramic membrane cold filtration to obtain yellow peach craft beer.

2. The method for preparing a low-bitter and high-flavor yellow peach craft beer according to claim 1, characterized in that: The liquid nitrogen freezing micro-explosion process in step 1 is: firstly, the fresh yellow peach pulp is quickly frozen in liquid nitrogen at -196--190°C for 5-10 minutes, and then quickly heated to 20-25°C for thawing.

3. The method for preparing a low-bitter and high-flavor yellow peach craft beer according to claim 1, characterized in that: The yellow peach juice obtained in the step 1 is further subjected to enzymatic hydrolysis treatment, first adding 0.5-1.0 U / g laccase, controlling the pH value to 5.0-5.3, and reacting at 35-40° C. for 30-35 minutes, then adding 1.5-2.5 U / g xylanase, controlling the pH value to 6.0-6.5, and reacting at 50-55° C. for 1.5-2.0 hours.

4. The method for preparing a low-bitter and high-flavor yellow peach craft beer according to claim 1, characterized in that: The gradient temperature saccharification in step 2 is carried out in three stages: 40-45° C., 60-63° C., and 72-75° C., with each stage maintained for 20 minutes.

5. The method for preparing low-bitterness and high-flavor yellow peach craft beer according to claim 1, characterized in that: In step 3, adding bitter hops and aroma hops in stages means that 70% of the bitter hops are added 45 minutes after the end of boiling, and 30% of the aroma hops are added 15 minutes after the end of boiling.

6. The method for preparing low-bitter and high-flavor yellow peach craft beer according to claim 1, characterized in that: In step 4, the inoculation amount of Lactobacillus plantarum is 5-10% of the yeast mass, and the fermentation is carried out at 18-20° C. for 3-4 days until the pH drops to 3.6-3.

8.

7. The method for preparing low-bitterness and high-flavor yellow peach craft beer according to claim 1, characterized in that: In the step 5, the ultrahigh pressure homogenization pressure is 200 MPa, and the ceramic membrane filtration treatment is performed by cold filtration at 2-4°C using a 0.45 μm ceramic membrane.

8. The method for preparing low-bitterness and high-flavor yellow peach craft beer according to claim 1, characterized in that: The yellow peach juice, barley malt, wheat malt, bitter hops, aromatic hops, water and brewer's yeast are calculated in parts by weight: 2-3 parts, 100-200 parts, 40-60 parts, 0.4-0.6 parts, 0.1-0.3 parts, 500-600 parts and 0.4-0.6 parts.

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