Method for processing corn by means of low-temperature immersion and steam explosion

Abstract

The present invention relates to a corn processing method, comprising: adding, continuously or in batches, corn, water and an optional chemical additive to a low-temperature immersion and steam explosion reactor; and in the low-temperature immersion and steam explosion reactor, performing an immersion reaction at a reaction temperature of 20-65°C and a gauge pressure of 0.1 MPa or higher for 0.5-9 h, then using a steam explosion pipeline for rapid steam explosion and performing discharging to obtain an aqueous corn slurry. The present invention further relates to the obtained corn slurry and the use thereof for the production of starch, sugar, alcohol, amino acids, vitamins, antibiotics and / or organic acids, etc., and the by-production of germs, fibers and proteins. In the method of the present invention, sulfurous acid is not used, and no immersion sewage or waste gas is generated; and the process equipment is simple, and the investment and the production cost are low.

Description

Method for processing corn by low temperature soaking and steam explosion Technical Field

[0001] The invention relates to the technical field of corn deep processing, in particular to a new method of replacing wet corn soaking with a low-temperature corn soaking and steam explosion method. Background Art

[0002] Using a highly efficient and cost-effective process to ensure that the moisture content of corn meets the requirements of wet corn processing technology, high-quality starch, dextrin, sugar, ethanol, amino acids, vitamins, organic acids and other high-value products can be produced, while high-quality germ, protein and fiber are produced as by-products without the generation of wastewater or "odor". This has been the long-term pursuit in the field of corn deep processing technology.

[0003] The traditional wet process uses a 0.20-0.25% by weight dilute sulfite solution, using an 8- or 10-tank process at 48-53°C for 48-65 hours in reverse order, to raise the corn's moisture content to above 40% by weight. The 0.7-0.9 tons of dilute corn steep liquor produced with each ton of corn soaked requires evaporation and concentration. The odor associated with this soaking process is a major environmental concern. Scientists and engineers have been working tirelessly to reduce or eliminate the use of sulfite soaking.

[0004] CN102464723A discloses a composite wet corn soaking method for producing corn starch. The method comprises the following steps: first, adding a 0.15%-0.20% sulfurous acid solution to the corn to be soaked, covering the corn by 20-30 cm; second, adjusting the pH of the soaking solution to a range of 4.5-5.0 using a 15% sodium hydroxide solution; and third, heating the soaking solution to 50°C, adding a cellulase enzyme with an enzyme activity of 40,000 U at a concentration of 1 / 100,000 of the corn dry matter, and soaking the corn at 50°C for 24 hours. While this patent reduces the amount of sulfurous acid used and the soaking time from 48 hours to 24 hours, it does not fundamentally address the waste gas and wastewater issues; the soaking time is still too long, and the efficiency remains low.

[0005] CN101372702A discloses a method for shortening the soaking time of corn for starch production, which is characterized by: 1. Pre-treating before soaking: selecting corn with full grains, no insect infestation, and no mildew, washing it with water three times, draining it, leaving it overnight, and placing it in a reactor; 2. Soaking: adding water, 450-1350 IU / g corn protease, and 15-80 IU / g corn cellulase in a ratio of 1-3 / 1 by mass of corn; 3. Pressurizing: connecting compressed air to 0.1-0.5 MPa, heating the reactor jacket with steam at 30-60°C for 10-20 hours, then releasing the pressure and opening the reactor. This method uses protease and cellulase instead of sulfurous acid, solving the problems of sewage and waste gas. However, the use of protease and cellulase increases costs, produces a large amount of water-soluble protein in the system, which increases the burden on subsequent starch or sugar refining, and the 10-12 hour soaking time is still too low.

[0006] CN106749691A discloses a corn soaking method in a corn starch production process, which is characterized by comprising the following steps: step 1: screening, selecting corn kernels with full grains; step 2: initial soaking, placing the corn in a constant temperature water bath at 30-50°C and soaking for 1-2 hours; step 3: crushing, filtering the soaked corn through a sieve to remove water, and drying it for 20-30 minutes, and crushing the corn through a crusher to allow the enzyme to enter the corn endosperm layer and react with protein; step 4: adding enzyme soaking, In step 3, the crushed corn is added with 10,000 to 20,000 U / L of enzyme, and then a cell permeation solution and 8 to 10% dilute hydrochloric acid are added and the corn is placed in a water bath shaker for 1 to 2 hours. In step 5, the pH value is adjusted by adding 16% sodium hydroxide solution to adjust the pH value of the soaking solution to control the pH value within the range of 4.5 to 5.5. In step 6, high-pressure soaking is performed by placing the corn and the soaking solution in a high-pressure constant temperature device, adjusting the pressure to 8.5 to 10.5 MPa and the temperature to 30 to 40°C, and soaking for 2 to 3 hours. This method is complex and requires large equipment investment and high cost. It requires not only soaking first, but also adding enzymes, hydrochloric acid, and cell permeation agents after crushing and soaking. It also requires high-pressure soaking at 8.5 to 10.5 MPa, adding enzymes and cell permeation agents, and frequently adjusting the pH value with acid and alkali.

[0007] CN115666258A discloses corn sweetening steeping, which is characterized by: a method for producing a soluble starch hydrolysate or hydrolyzed starch syrup from corn kernels, the method comprising soaking substantially intact corn kernels in water at a temperature at or above the gelatinization temperature of the starch in the corn kernels, wherein the soaking is carried out in the presence of an exogenous heat-stable α-amylase, which produces a soluble starch hydrolysate or hydrolyzed starch syrup from the starch present in the corn kernels, and the soaking temperature inactivates endogenous corn proteases and carbohydrate hydrolases present in the corn kernels; and subsequently fractionating the soaked corn kernels to obtain a soluble starch hydrolysate or hydrolyzed starch syrup portion and a substantially intact, starch-depleted, protein- and oil-enriched corn kernel residue, wherein the process has a low starch or starch sugar yield, requires special equipment for the production process, and is difficult to industrialize.

[0008] CN101607218A discloses a method for separating corn germ and endosperm using steam explosion technology: 1. Soak wet corn until it contains 30% water. 2. Steam explosion is performed at a pressure of 1.0-1.5 MPa for 3-6 minutes. This method denatures the germ and gelatinizes the endosperm using 1.0-1.5 MPa steam. This method requires the development of specialized equipment to further process the denatured germ and gelatinized endosperm.

[0009] CN110200149A discloses a method for preparing whole-plant silage corn feed, which is characterized by comprising the following steps: S1, cutting fresh whole-plant corn into sections, placing the sections in a steam explosion tank, and steam-exploding the sections at 0.7-1.5 MPa and 60-80°C for 5 minutes to obtain whole-plant corn pulp; S2, pouring the whole-plant corn pulp into a mixing tank, adding appropriate amounts of beet sugar processing residues and stevia leaf residue after extraction, stirring evenly, adding 0.33-0.44% formic acid and 0.33-0.44% propionic acid by weight of the mixture, stirring evenly, adding 1.4%-1.7% lactic acid bacteria silage starter, mixing evenly, and conveying the sections to an above-ground kiln by a belt conveyor for compaction and sealing. After fermentation at 25-35°C for 40-50 days, the sections can be opened for use. Although this method uses the concept of low-temperature steam explosion, on the one hand, the application processes whole-plant silage corn, which includes corn, corn stalks, corn leaves, and corn cobs. The purpose is to loosen the fiber structure of the corn stalks, leaves, and cobs, improve the fermentation efficiency of the fiber, and make silage feed; on the other hand, the moisture content of the whole-plant silage corn is 66.5% to 69.5%, and there is no low-temperature soaking and steam explosion process of this application.

[0010] CN1212377C discloses an improved wet process for producing fuel ethanol. The process involves soaking purified corn in a soaking tank at a temperature of 60-65°C for 4-12 hours. The soaking liquid is the same centrifugal supernatant used in the ethanol production process. The soaked corn pulp is then returned to the ethanol production process to produce DDGS. The soaked corn undergoes two crushing steps, followed by two-stage germ separation to produce corn starch. This is then saccharified, fermented, distilled, and dehydrated to produce anhydrous ethanol. The separated wet germ is washed, dried, and then used for oil extraction. This method uses acidic centrifugal supernatant to soak the corn, replacing the traditional sulfur dioxide wet soaking method. The soaking effect is unknown. While the germ is separated, the germ yield is low. High-value-added products such as protein are not separated, resulting in a low overall efficiency.

[0011] To reduce investment and meet environmental requirements, the dry corn ethanol process eliminates the corn soaking step and directly dry-grinds the corn, controlling the particle size to 1-3 mm before liquefaction and fermentation. This process fails to separate high-value germ and protein, and starch residues as high as 3-5%. It also consumes large amounts of enzymes, high electricity consumption for dry-grinding the corn, and severe equipment wear, resulting in low economic returns.

[0012] CN103146768B discloses a method for preparing citric acid. The method is characterized in that the method comprises the following steps: (1) preparing an aqueous solution containing a thermostable amylase, mixing the aqueous solution containing the thermostable amylase with starchy raw material powder to obtain a mixture, wherein the mixing conditions include a temperature of 70-85°C; (2) spraying the mixture obtained in step (1) once to 90-100°C and maintaining the temperature; and then spraying the product obtained by the once spraying twice to 120-140°C and maintaining the temperature; (3) mixing the product obtained in step (2) with an amylase under enzymatic hydrolysis conditions, performing enzymatic hydrolysis, and obtaining a liquefied liquid containing oligosaccharides; (4) preparing a fermentation medium using the liquefied liquid, and inoculating Aspergillus niger into the fermentation medium under conditions that can generate citric acid for fermentation, wherein in step (3), the amylase is a thermostable amylase, and the enzymatic hydrolysis conditions include an enzymatic hydrolysis temperature of 90-100°C, an enzymatic hydrolysis time of 12-60 min, and an amount of the amylase used is 30-40% by weight of the amount of the thermostable amylase used in the aqueous solution containing the thermostable amylase prepared in step (1). This method cannot separate high-value germ and protein, and the starch residue is as high as 3-5%. It consumes a lot of enzymes, consumes a lot of electricity for corn dry grinding, and causes serious equipment wear and tear, resulting in low economic benefits.

[0013] Therefore, the field of corn deep processing urgently needs to develop a new process with high efficiency and cost-effectiveness to replace the existing wet corn soaking process, so that the moisture content of corn can meet the requirements of the wet corn processing process. It can borrow part of the wet corn production process to produce high-quality starch, sugar, alcohol, amino acids, vitamins, antibiotics and / or organic acids and other high-value products, while producing high-quality germ, protein and / or fiber as by-products, but without the accompanying wastewater and "odor", so it has a simpler process flow, less investment and land occupation, lower energy consumption and operating costs. Summary of the Invention

[0014] The present invention aims to provide a novel corn processing method that replaces the conventional wet corn soaking method with a low-temperature soaking and steam explosion method. This method allows the corn to rapidly absorb water and swell, meeting the requirements of conventional wet corn processing, without compromising the quality of the germ and endosperm and without emitting wastewater or exhaust gas from soaking. This novel method utilizes some of the processes and equipment of wet corn processing to produce high-value-added products such as high-quality starch, dextrin, sugar, alcohol, amino acids, vitamins, antibiotics, and / or organic acids, while also producing high-quality germ, protein, and / or fiber as byproducts.

[0015] Specifically, the present invention provides a new method for corn processing, wherein corn, water and optional chemical additives are continuously or batchwise added to a low-temperature soaking steam explosion reactor; in the low-temperature soaking steam explosion reactor, the soaking reaction is carried out at a reaction temperature of 20-65°C and a gauge pressure of more than 0.1 MPa for 0.5-9 hours, and the material is rapidly steam-exploded and discharged continuously or batchwise through a steam explosion pipeline to obtain a water-containing corn slurry.

[0016] "Low-temperature steam explosion" as used herein refers to a process in which pressure is rapidly reduced at temperatures below 100°C. The temperature is preferably below 65°C, and more preferably below 63°C. In the art, low-temperature steam explosion is distinct from steam explosion, which occurs above 100°C.

[0017] Preferably, the moisture content of the corn in the obtained corn slurry is greater than or equal to 35 weight %, more preferably greater than or equal to 38 weight %, and even more preferably greater than or equal to 40 weight %.

[0018] In one embodiment, the corn is first washed with water to remove impurities on the surface of the corn, such as dust, and optionally to separate and remove empty kernels and large and small corn debris in the corn, such as corn cobs, corn stalks, stones, etc., as well as gloves, bricks, iron blocks, etc., and preferably drain the water.

[0019] The water is, for example, selected from drinking water, deionized water, or process circulating water. Preferably, the amount of water added is 100-300 wt %, more preferably 100-250 wt %, even more preferably 100-200 wt %, further more preferably 100-150 wt %, for example 100 wt %, 110 wt % and 120 wt %, based on the dry weight of the corn.

[0020] Preferably, in the low-temperature immersion steam explosion reactor, the immersion reaction temperature is 40-65°C, more preferably 45-65°C, such as 50°C, 60°C and 63°C.

[0021] Preferably, in the low-temperature immersion steam explosion reactor, the gauge pressure of the immersion reaction is 0.1-10 MPa, more preferably 0.5-8 MPa, and even more preferably 0.5-6 MPa, such as 1 MPa, 1.2 MPa, 2 MPa and 6 MPa.

[0022] Preferably, in the low-temperature immersion steam explosion reactor, the immersion reaction time is 0.5-8 hours, and more preferably 0.5-6 hours, such as 1, 2, 3 and 4 hours.

[0023] In one embodiment, a suitable gas or water that does not affect the reaction, such as air, nitrogen, oxygen and / or water, is introduced into the low-temperature immersion steam explosion reactor to increase the pressure of the reactor, while water vapor is not a suitable gas.

[0024] In one embodiment, the linear velocity is increased continuously or in batches through a steam explosion pipeline, and the material is discharged into a normal pressure tank by rapid impact explosion.

[0025] In one embodiment, in addition to corn and water, a chemical additive is added to the low-temperature immersion steam explosion reactor. The chemical additive may be an acid, a base (including a Lewis acid or a base), or an enzyme, such as citric acid, acetic acid, oxalic acid, sulfuric acid, hydrochloric acid, sodium sulfite, etc. Preferably, the amount of the chemical additive is 0-10% by weight, more preferably 0-1.5% by weight, and even more preferably 0-1% by weight, based on the dry weight of the corn, such as 0 (neutral steam explosion), 0.5% by weight, and 1% by weight.

[0026] The low-temperature immersion steam explosion reactor can be one or more pressure vessels or reactors (kettles or towers) such as a pressure kettle, a pressure tank, a tubular reactor, a digester (pot), a pressure screw conveyor, a tower, a steam ball, an autoclave, a decomposition pot, and a vulcanizing tank, and can be used alone or in series or in parallel.

[0027] In one embodiment, the rapid steam explosion is performed by, for example, continuously or intermittently opening the reactor valve rapidly, increasing the linear velocity of the steam-exploded corn through the steam explosion pipe, and impacting the atmospheric pressure tank.

[0028] For example, one embodiment of the corn processing method of the present invention includes the following steps:

[0029] (1) washing the corn with water to remove dust from the surface of the corn, separating and removing the empty kernels and large and small corn debris from the corn, and draining the water;

[0030] (2) Weighing the corn treated in step (1) and 100-300 wt% of water based on the dry weight of the corn, and adding them continuously or in batches to a low-temperature soaking steam explosion reactor, soaking and reacting them in the low-temperature soaking steam explosion reactor at 20-65° C. and 0.1-10 MPa for 0.5-9 hours, continuously or intermittently increasing the linear speed through the steam explosion pipeline, and rapidly steam-exploding and impacting them into the atmospheric pressure tank.

[0031] Another object of the present invention is to provide a corn slurry obtained by the method of the present invention.

[0032] The corn slurry after the low-temperature soaking steam explosion of the present invention, for example, adopts traditional wet corn processing technology to produce starch, dextrin, sugar, alcohol, amino acid, vitamin, antibiotic and / or organic acid, and by-products germ, protein and / or fiber. The corn slurry after the low-temperature soaking steam explosion is further processed to obtain the primary starch milk sizing, enzyme addition and injection liquefaction, and the liquefied liquid is, for example, filtered using a vacuum drum filter to obtain a clarified liquefied liquid, the clarified liquefied liquid DE value of which is 14-18, and the obtained filter cake iodine test is qualified. The clarified liquefied liquid is further saccharified, and the saccharification DE value is 95.5-98.1.

[0033] The content in this application is determined as follows:

[0034] (1) Determination of moisture content of corn after soaking

[0035] Take the soaked corn and wipe off any surface moisture with absorbent paper. Weigh 3-5g of the corn and place it in a METTLER TOLEDO halogen moisture analyzer to quickly measure the moisture content.

[0036] (2) Determination of soluble organic matter content in clarified soaking water

[0037] 20ul of clarified soaking water was extracted and injected into a Waters 1515 liquid chromatograph to measure the water-soluble sugar of each component; another 20ul of clarified soaking water was injected into a TOC-L total carbon / total nitrogen analyzer to analyze the total nitrogen and convert the protein content. The sugar content of each component was added together with the protein content to obtain the soluble organic matter content.

[0038] (3) Determination of protein content in organic matter in clarified liquid

[0039] Extract 20ul of clarified soaking water and inject it into TOC-L total carbon / total nitrogen analyzer to analyze the total nitrogen, which is multiplied by a fixed coefficient of 6.25 to obtain the protein content.

[0040] Advantages of the present invention:

[0041] The corn low-temperature soaking and steam explosion method of the present invention is used to replace the traditional wet corn soaking method, which can shorten the soaking time from the original 36-48 hours to 0.5-9 hours. For example, based on an annual processing capacity of 500,000 tons of corn, the volume of the soaking tank is reduced from 10*350m 3 Reduced to 2*300m 3 , the investment in soaking equipment is saved by at least 80% or more (for example, in one embodiment, the equipment investment is reduced from 19 million yuan to 3 million yuan, saving about 84% of the construction investment); the soaking of the present invention does not use sulfurous acid, so no wastewater or odor is generated; the soluble organic matter content of the soaking water is reduced from 6-10 weight%, and the soluble protein content in the organic matter is reduced from 3-5 weight% to 0.05-1.5 weight% and 0.15-0.35 weight%, respectively; after the soaking water is desanded by cyclone, it enters the crushing process with the corn, eliminating the concentration and evaporation process of the soaking water, saving a large amount of steam, and saving at least 70% of the operating cost, for example, about 72%. The product produced using the inventive method, the quality of starch (or dextrin), sugar or alcohol and by-product protein, germ, and fiber are better than wet grinding process, wherein the protein content is increased from 55-60 weight % of wet grinding process to 62-70 weight %; the product yield (dry basis) of unit corn deep processing is higher, wherein the yield of starch (or dextrin) is increased from 70 weight % of wet grinding process to 73-74 weight %, the protein yield is increased from 5.5 weight % to 7.0-7.5 weight %, the germ yield is slightly increased, and the fiber yield is basically the same as wet grinding process. Since the starch yield has increased by about 4 weight % and the protein yield has increased by about 1.8 weight %, the income of corn per ton of dry basis increased by 236 yuan. Therefore, the present invention is not only safe and environmentally friendly, but also has lower investment and cost, and the unit dry basis corn income is also higher. DETAILED DESCRIPTION

[0042] Example

[0043] The technical solution of the present invention will be further described below in conjunction with the embodiments. The embodiments of the present invention should not be interpreted as limiting the present invention.

[0044] Example 1

[0045] Step 1: Wash corn (northeastern corn, with a moisture content of 10.44% by weight) with water to remove dust from the surface of the corn, separate and remove the empty kernels and large and small corn debris from the corn, and drain the water;

[0046] Step 2: Weigh 2 kg of corn treated in step 1 and add it to a 10-liter high-pressure soaking reactor. Add 2.4 kg of water and 10 g of commercially available citric acid. The temperature is raised to 60-63° C., the input air pressure is increased to 1 MPa gauge pressure, and the reaction is soaked for 1 hour. The corn is then accelerated through a steam explosion pipeline and discharged into a normal pressure tank by steam explosion impact to obtain a corn slurry. The water content of the corn in the corn slurry is measured to be 40.05% by weight, and the soluble organic matter content in the clarified soaking water is 1.05% by weight, wherein the protein content in the organic matter is 0.32% by weight. The corn slurry is subjected to the steps of removing the germ, peeling, sizing, and liquefaction to obtain dextrin with a dextrin DE value of 17.23. The product (dry basis) yields are: 73.67% by weight of dextrin, 7.23% by weight of protein, 7.96% by weight of germ, and 11.04% by weight of fiber.

[0047] Example 2

[0048] Step 1: Wash corn (northeastern corn, with a moisture content of 15.15% by weight) with water to remove dust from the surface of the corn, separate and remove the empty kernels and large and small corn debris from the corn, and drain the water;

[0049] Step 2: Weigh 5.0 kg of corn and 6.0 kg of water after the treatment in step 1, and continuously add them to a 10-liter high-pressure tubular soaking reactor. The temperature is raised to 60° C., the input air pressure is increased to 1 MPa gauge pressure, and the soaking reaction is carried out for 2 hours. The corn is continuously accelerated through a steam explosion pipeline, and the steam explosion impact discharge is discharged into an atmospheric tank to obtain a corn slurry. The water content of the corn in the corn slurry is measured to be 41.57% by weight, and the clarified soaking water contains 1.07% by weight of soluble organic matter, wherein the organic matter contains 0.28% by weight of protein. The corn slurry is subjected to the steps of removing the embryo, peeling, sizing, liquefaction, and saccharification to obtain a syrup with a syrup DE value of 97.13 and a product (dry basis) yield of 78.24% by weight of sugar, 7.34% by weight of protein, 8.02% by weight of germ, and 10.64% by weight of fiber.

[0050] Example 3

[0051] Step 1: Wash corn (northeastern corn, with a moisture content of 15.15% by weight) with water to remove dust from the surface of the corn; separate and remove the empty kernels and large and small corn debris from the corn, and drain the water;

[0052] Step 2: Weigh 5.0 kg of corn and 6.0 kg of water after the treatment in step 1, and continuously add them to a 10-liter high-pressure tubular soaking reactor. The temperature is raised to 62° C., the water pressure is increased to 1 MPa gauge pressure with a pump, and the soaking reaction is continued under 1 MPa gauge pressure for 2 hours. The corn is continuously accelerated through a steam explosion pipeline, and the rapid steam explosion impact discharge is discharged into an atmospheric tank to obtain a corn slurry. The water content of the corn in the corn slurry is measured to be 40.12% by weight, and the soluble organic matter content in the clarified soaking water is 1.14% by weight, wherein the organic matter contains 0.28% by weight of protein. The corn slurry is subjected to the steps of removing the embryo, peeling, sizing, liquefaction, and saccharification to obtain a syrup with a syrup DE value of 97.22 and a product (dry basis) yield of 78.12% by weight of sugar, 7.38% by weight of protein, 8.06% by weight of germ, and 10.51% by weight of fiber.

[0053] Example 4

[0054] Step 1: Wash corn (northeastern corn, with a moisture content of 10.44% by weight) with water to remove dust from the surface of the corn, separate and remove the empty kernels and large and small corn debris from the corn, and drain the water;

[0055] Step 2: Weigh 60g of corn treated in step 1 and add it to a 0.5L high-pressure tubular soaking reactor. Then, add 60g of water and 0.6g of citric acid. The temperature is raised to 60°C, the input air pressure is raised to 1.2MPa gauge pressure, and the reaction is soaked for 2 hours. Then, the corn linear velocity is increased through a steam explosion pipeline, and the steam explosion impact is discharged into an atmospheric pressure tank to obtain a corn slurry. The water content of the corn in the corn slurry is measured to be 40.16% by weight, and the soluble organic matter content in the clarified soaking water is 1.11% by weight, wherein the organic matter contains 0.35% by weight of protein. The corn slurry is subjected to the steps of removing the embryo, peeling, sizing, liquefaction, and saccharification to obtain a syrup with a syrup DE value of 96.93 and product (dry basis) yields of 78.42% by weight of sugar, 7.14% by weight of protein, 8.26% by weight of germ, and 10.91% by weight of fiber.

[0056] Example 5

[0057] Step 1: Wash the corn (northeastern corn, with a water content of 13.45% by weight) with water to remove dust from the surface of the corn, separate and remove the empty kernels and large and small corn debris from the corn, and drain the water.

[0058] Step 2: Weigh 5.0 kg of corn and 6.0 kg of water after the treatment in step 1, and continuously add them to a 10-liter high-pressure tubular soaking reactor. The temperature is raised to 50° C., the input air pressure is increased to 2 MPa gauge pressure, and the soaking reaction is continued for 2 hours. The corn linear speed is continuously increased through a steam explosion pipeline, and the corn is quickly steam-exploded and impact-discharged into a normal pressure tank to obtain a corn slurry. The water content of the corn in the corn slurry is measured to be 41.91% by weight, and the soluble organic matter content in the clarified soaking water is 1.13% by weight, of which the organic matter contains 0.21% by weight of protein. The corn slurry is subjected to the steps of removing the germ, peeling, sizing, and liquefaction to obtain dextrin with a dextrin DE value of 16.17. The product (dry basis) yields are: 73.54% by weight of dextrin, 7.42% by weight of protein, 7.83% by weight of germ, and 11.37% by weight of fiber.

[0059] Example 6

[0060] Step 1: Wash corn (northeastern corn, with a moisture content of 10.44% by weight) with water to remove dust from the surface of the corn, separate and remove the empty kernels and large and small corn debris from the corn, and drain the water;

[0061] Step 2: Weigh 5.0 kg of corn and 6.0 kg of water treated in Step 1 and add them continuously to a 10-liter high-pressure tubular soaking reactor. The temperature is raised to 60°C and the pressure is increased to 1.0 MPa gauge using a pump for soaking for 2 hours. The corn is then discharged into a normal pressure tank by steam explosion impact to obtain a corn slurry. The water content of the corn in the corn slurry is determined to be 40.37% by weight, and the soluble organic matter content in the clarified soaking water is 1.27% by weight, of which the organic matter contains 0.31% by weight of protein. The corn slurry is subjected to the following steps: germ removal, hull removal, slurry preparation, liquefaction, and simultaneous saccharification and fermentation to produce fuel ethanol, thereby obtaining fuel ethanol. The product yields (on a dry basis) are: 36.9% by weight of fuel ethanol, 7.14% by weight of protein, 8.26% by weight of germ, and 10.91% by weight of fiber.

[0062] Comparative Example 1

[0063] Step 1: Wash the corn (northeastern corn, with a water content of 13.45% by weight) with water to remove dust from the surface of the corn, separate and remove the empty kernels and large and small corn debris from the corn, and drain the water.

[0064] Corn 5.0kg after processing in step 2, weighing step 1, join in the corn soaking tank, add the water of 6.0kg, be warming up to 50 ℃, normal pressure soak 43 hours, then unload in the normal pressure tank by pipeline, obtain corn slurry, measuring the water content of corn in this corn slurry is 27.08 % by weight, the soluble organic matter content in the clarification soaking water is 0.25 % by weight, wherein organic matter is 0.09 % by weight containing protein, and corn is moisture-containing and can not reach the technological requirement of wet-milling corn. With this corn slurry, through operations such as getting embryo, peeling, sizing, liquefaction, obtain dextrin, dextrin DE value 14.23, product (butt basis) yield is respectively: dextrin 65.64 % by weight, protein 4.15 % by weight, germ 4.53 % by weight, fiber 24.96 % by weight. The dextrin yield of this comparative example is too low, and protein, germ yield are also too low, and economic benefit is poor.

[0065] Comparative Example 2

[0066] Step 1: Wash corn (northeastern corn, with a moisture content of 15.15% by weight) with water to remove dust from the surface of the corn, separate and remove the empty kernels and large and small corn debris in the corn, and drain the water;

[0067] Step 2: Weigh 5.0 kg of corn after the treatment in step 1 and add it to a 10-liter tubular soaking reactor. Then, add 6.0 kg of water and 11.25 g of sulfurous acid. The mixture is heated to 60° C. and soaked at normal pressure for 48 hours. The mixture is then unloaded into a normal pressure tank via a pipeline to obtain a corn slurry. The water content of the corn in the corn slurry is 42.34% by weight, while the clarified soaking water contains 8.62% by weight of soluble organic matter, of which the organic protein content is 4.21% by weight. The corn moisture content meets the process requirements for wet-milling corn. The corn slurry is subjected to processes such as embryo removal, peeling, sizing, and liquefaction to obtain dextrin. The dextrin DE value is 16.47, and the product (dry basis) yields are: 69.83% by weight of dextrin, 5.47% by weight of protein, 6.84% by weight of germ, and 10.24% by weight of fiber. The soaking water is evaporated and concentrated to obtain about 17.5% by weight (50% dry basis) of low-value corn steep liquor. The yield of the main product dextrin and the by-product protein in Comparative Example 2 is not high. In addition, the sulfur dioxide odor volatilized during the soaking and treatment process pollutes the air.

[0068] Comparative Example 3

[0069] Step 1: Wash corn (northeastern corn, with a moisture content of 15.15% by weight) with water to remove dust from the surface of the corn, separate and remove the empty kernels and large and small corn debris from the corn, and drain the water;

[0070] Step 2: Weigh 5.0 kg of corn treated in step 1 and add it to a 10-liter tubular soaking reactor. 6.0 kg of water and 12.5 g of sulfurous acid are added, and the mixture is heated to 60° C. and soaked at normal pressure for 48 hours. The mixture is then unloaded into a normal pressure tank via a pipeline to obtain a corn slurry. The water content of the corn in the corn slurry is determined to be 44.83% by weight, while the clarified soaking water contains 9.47% by weight of soluble organic matter, including 4.92% by weight of organic protein. The corn moisture content meets the process requirements for wet-milling corn. The corn slurry is subjected to processes such as embryo removal, peeling, sizing, liquefaction, and saccharification to obtain a syrup with a DE value of 97.12. The product (on a dry basis) yields are: 73.13% sugar, 5.21% protein, 8.02% germ, and 9.98% fiber. The soaking water is concentrated by evaporation to obtain a low-value corn steep liquor of approximately 19% by weight (50% on dry basis). The yields of sugar and protein in Comparative Example 3 were not high, and the economic benefits were poor. In addition, the sulfur dioxide odor volatilized during the soaking and treatment process polluted the air.

Claims

1. A method for processing corn, wherein corn, water and optional chemical additives are continuously or batchwise added to a low-temperature soaking steam explosion reactor; in the low-temperature soaking steam explosion reactor, the soaking reaction is carried out at a reaction temperature of 20-65°C and a gauge pressure of 0.1 MPa or above for 0.5-9 hours, and then the material is discharged continuously or batchwise through a steam explosion pipe by rapid steam explosion to obtain a water-containing corn slurry.

2. The method according to claim 1, wherein The corn is first washed with water to remove impurities on the surface of the corn, and optionally separated to remove empty kernels and large and small corn debris, such as corn cobs, corn stalks, stones, etc., as well as gloves, bricks, iron blocks, etc., and preferably drained.

3. The method of claim 1 or 2, wherein The moisture content of the corn in the obtained corn slurry is greater than or equal to 35 weight %, more preferably greater than or equal to 38 weight %, and more preferably greater than or equal to 40 weight %, and / or The amount of water added is 100-300 wt %, more preferably 100-250 wt %, still more preferably 100-200 wt %, further more preferably 100-150 wt %, based on the dry weight of the corn, and / or In the low-temperature immersion steam explosion reactor, the immersion reaction temperature is 40-65°C, more preferably 45-65°C, and / or In the low-temperature immersion steam explosion reactor, the gauge pressure of the immersion reaction is 0.1-10 MPa, more preferably 0.5-8 MPa, and even more preferably 0.5-6 MPa, and / or In the low-temperature immersion steam explosion reactor, the immersion reaction time is 0.5-8 hours, and more preferably 0.5-6 hours.

4. The method according to any one of claims 1 to 3, wherein Introducing a suitable gas or water that does not affect the reaction, such as air, nitrogen, oxygen and / or water, into the low-temperature immersion steam explosion reactor to increase the pressure of the reactor, and / or The material is discharged continuously or in batches into the atmospheric pressure tank through the steam explosion pipe.

5. The method according to any one of claims 1 to 4, wherein the chemical additive is an acid, a base (including a Lewis acid or a base) or an enzyme, such as citric acid, acetic acid, oxalic acid, sulfuric acid, hydrochloric acid, sodium sulfite, etc.; preferably, the amount of the chemical additive is 0-10 weight %, more preferably 0-1.5 weight %, and even more preferably 0-1 weight % based on the dry weight of the corn.

6. The method according to any one of claims 1 to 5, wherein the low-temperature immersion steam explosion reactor is one or more pressure vessels or reactors (kettles or towers) such as a pressure autoclave, a pressure tank, a tubular reactor, a digester (pot), a pressure screw conveyor, a tower, a steam ball, an autoclave, a decomposition pot, and a vulcanizing tank, which can be used alone or in series or in parallel.

7. The method according to any one of claims 1 to 6, wherein the rapid steam explosion is carried out continuously or intermittently by quickly opening the valve of the low-temperature soaking steam explosion reactor, increasing the linear velocity of the steam-exploded corn through the steam explosion pipeline, and impacting the atmospheric pressure tank.

8. The method according to any one of claims 1 to 7, comprising the steps of: (1) washing the corn with water to remove dust from the surface of the corn, separating and removing the empty kernels and large and small corn debris from the corn, and draining the water; (2) The corn treated in step (1) and 100-300 wt% of water based on the dry weight of the corn are weighed and added continuously or in batches to a low-temperature soaking steam explosion reactor. In the low-temperature soaking steam explosion reactor, the corn is soaked and reacted at 20-65° C. and 0.1-10 MPa for 0.5-9 hours. The corn is then continuously or intermittently steam-exploded into a normal pressure tank by increasing the linear velocity through a steam explosion pipe.

9. The corn slurry obtained according to the method described in any one of claims 1 to 8.

10. Use of the corn slurry according to claim 9 for producing starch, dextrin, sugar, alcohol, amino acids, vitamins, antibiotics and / or organic acids, and producing germ, protein and / or fiber as by-products.