CN111481700A - Sterilization method for reducing microbial level in corn starch production system - Google Patents

Abstract

A sterilization method for reducing the level of microorganisms in a corn starch production system, belonging to the technical field of corn deep processing. Aiming at the problem that the existing disinfection method for the corn starch production system has poor effect of inhibiting the growth of microorganisms, the invention provides a sterilization method for reducing the level of microorganisms in the corn starch production system, which uses nisin aqueous solution as sterilization liquid to sterilize equipment used in the corn starch production process. The working concentration of the nisin aqueous solution is 20-200 ppm. The invention can effectively inhibit the growth and the propagation of microorganisms in the system, keeps the microorganisms of the starch finished product at a very low level, and can prolong the low microorganism level in the system by about 1 month compared with the traditional liquid caustic soda disinfection mode. The frequency of cleaning and disinfecting the system is reduced, and the energy consumption is saved; has no corrosion effect on production equipment, and is a clean and efficient sterilizing agent.

Description

Sterilization method for reducing microbial level in corn starch production system

Technical Field

The invention belongs to the technical field of corn deep processing, and particularly relates to a sterilization method for reducing the level of microorganisms in a corn starch production system.

Background

The starch washing section in the corn starch production system is very suitable for the growth and reproduction of microorganisms due to the characteristics of large moisture content, proper temperature and pH and the like, which directly causes the overproof microorganisms in the produced starch finished products, and the disinfection and sterilization mode of the existing corn starch production system mainly takes liquid alkali disinfection and sterilization as the main mode. The specific implementation method is that the sodium hydroxide solution with a certain concentration (2% -3%) is prepared by using clear water, and the sodium hydroxide solution can hydrolyze protein and nucleic acid of pathogenic bacteria, destroy the normal metabolic function of bacteria, kill the bacteria and has a good sterilization effect. Sterilizing and disinfecting the tank body and the pipeline by using a sodium hydroxide solution with a certain concentration, and then removing the solution; and cleaning the residual solution in the system by using clear water, and discharging the waste water after cleaning, thereby completing the disinfection and sterilization process of the corn starch production system.

Although the sodium hydroxide solution has a disinfecting and sterilizing effect to some extent. However, the method cannot play a role in inhibiting the growth of microorganisms, and along with the operation of a production system, the microorganisms in the system quickly begin to grow, so that the microorganisms of the finally produced corn starch finished products exceed the standard, and therefore, in order to solve the problem that the microorganisms of the production system and the starch finished products exceed the standard, a more effective system disinfection and sterilization method needs to be found.

Disclosure of Invention

Aiming at the problem that the existing disinfection method for the corn starch production system has poor effect of inhibiting the growth of microorganisms, the invention provides a sterilization method for reducing the level of microorganisms in the corn starch production system, which uses nisin aqueous solution as sterilization liquid to sterilize equipment used in the corn starch production system.

Further defined, the working concentration of the nisin aqueous solution is between 20 and 200 ppm.

Preferably, the working concentration of the nisin aqueous solution is between 70 and 160 ppm.

Preferably, the working concentration of the aqueous solution of nisin is 120 ppm.

More particularly, the sterilization method comprises the following steps:

(1) Rinsing with clear water: washing equipment used in a corn starch production system with clear water, cleaning materials remained in the equipment and pipelines, and washing the cleaned materials with the clear water;

(2) Preparing the cecidin: mixing nisin with process water to prepare a sterilizing solution with the solution concentration of 20-200 ppm;

(3) And (3) system disinfection and sterilization: and (3) pumping the sterilizing liquid prepared in the step (2) into equipment used in a corn starch washing process and equipment used in a dehydration drying process in sequence by using a pump body, and enabling the sterilizing liquid to flow through each equipment to finish sterilization.

Preferably, the dosage of the sterilizing liquid in the step (3) is 1/3-1/2 of the volume of the equipment to be sterilized.

Advantageous effects

compared with the traditional liquid alkali sterilization method, the method has the advantages that the nisin is used as a bactericide to sterilize a corn starch production system, so that the growth and the propagation of microorganisms in the system can be effectively inhibited, and further, the microorganisms of a starch finished product are kept at a very low level, and experimental results show that after nisin is used for sterilization, the total number of starch milk colonies in the system is reduced from 10 to 6 CFU/m L and 10 to 3 CFU/m L, the total number of the starch finished product colonies is reduced from more than 10000CFU/g to about 2000CFU/g, and compared with the traditional liquid alkali sterilization method, the method can prolong the low microorganism level in the system by about 1 month (6 months are prolonged to 7 months), reduce the frequency of cleaning and sterilization of the system, save energy consumption, reduce the usage amount of nisin (dozens to hundreds of ppm), reduce the usage cost, simplify the solution preparation, facilitate operation, and have no corrosion effect on production equipment compared with liquid alkali, so that the nisin is a clean and efficient sterilization reagent.

Detailed Description

The method for sterilizing a corn starch production system using nisin according to the present invention will be described below by way of example.

The noun explains:

Twelve-grade washing system of starch: the starch washing system is a cyclone group consisting of ten groups of cyclones, which are collectively called twelve stages, and the whole system is operated as a unified countercurrent washing mechanism. Its functions are to reduce protein content in starch milk, wash out fat, fibre and soluble substances in starch milk, and provide refined starch milk for dewatering and drying starch.

Process water: refers to the recycled water present in the system during the production of corn starch, rather than the fresh, pure water introduced.

Example 1. Sterilization method to reduce microbial levels in a corn starch production system.

The corn starch production system described in this embodiment adopts the american dalton production process, which is also a production system commonly used in the field at present, and the basic principle is to extract starch by using different specific gravities of starch, protein, germ and fiber in corn, and adopting a physical separation method, and completely separating the protein, germ and fiber, and evaporating and concentrating corn steep liquor to be used as a byproduct in a starch workshop. The corn production system mainly comprises a wet corn storage tank, a scraper conveyor, a bucket elevator, a sulfur melting tank, a combustion chamber, a sulfur dioxide absorption tower, a sulfurous acid delivery pump, a corn soaking tank, a soaking liquid circulating pump, a soaking liquid circulating heater, a wet corn delivery pump, a sulfurous acid storage tank, a first mill, a germ separator, a second mill, fine grinding, a coarse starch milk tank, a germ washing water tank, a process water tank, a pre-concentration centrifuge, a main centrifuge, a twelve-stage washing system, a fine starch milk storage tank, a scraper type centrifuge, a scraper overflow liquid tank, a filtrate concentration feeding tank, a horizontal spiral concentrator, a starch airflow dryer, an air heating system, a cyclone separator, a tube bundle dryer and a multi-effect evaporator according to the processing technology. The above-mentioned equipment is conventional in the art.

The process flow mainly comprises the following steps: 1. storing and purifying raw material corn; 2. feeding and soaking corns; 3. crushing the corn; 4. finely grinding the corn; 5. separating and washing fibers; 6. separating starch and washing the starch; 7. dehydrating and drying starch; 8. separating and drying protein; 9. washing and drying the germ; 10. evaporating the corn soaking solution; 11. and (4) drying the fiber. The above process flows are all carried out according to corresponding equipment using methods, and are conventional in the field.

The application is to carry out disinfection and sterilization in starch washing and starch dehydration drying procedures in a corn starch processing technology. The equipment related to the production process comprises a process water tank, a main centrifuge, a twelve-stage washing system, a scraper centrifuge, a refined starch milk storage tank, a scraper overflow liquid tank, a filtrate concentration feeding tank and a horizontal spiral concentrator (manufacturers with different equipment names may have slight differences, but do not influence the sterilization treatment scheme of the application).

The following describes the disinfection and sterilization method of the corn starch production system in detail:

(1) Rinsing with clear water: the whole production system (namely the tank body and other equipment) is firstly washed by clean water, the system is manually cleaned after being washed, the materials remained in the equipment and the pipeline are cleaned, and the cleaned materials are washed by the clean water.

(2) Preparing the cecidin: the method is characterized in that a water solution of the spinosad-nisin is prepared in a process water tank as a sterilization solution, wherein the volume of the process water tank is 60 cubic meters, the volume of the preparation solution accounts for one half of the total volume of a tank body, namely 30 cubic meters, and the concentration of the sterilization solution is 20ppm, so that the sterilization of the system is carried out once, and the dosage of the streptococcus lactis is 0.6 kg.

(3) And (3) a system disinfection and sterilization process: after the nisin solution is prepared, the sterilizing liquid in the process water tank is pumped into a main centrifuge by a pump, the feeding amount is 180 cubic meters per hour, the main centrifuge is started, the rotating speed is 3000 revolutions per minute, so that the sterilizing liquid starts to run in the main centrifuge, and under the action of the pump, the sterilizing liquid sequentially enters a twelve-stage washing system, a scraper centrifuge, a refined starch milk storage tank, a scraper overflow liquid tank, a filtrate concentration feeding tank and a horizontal spiral concentrator through pipelines. Wherein the feeding amount of the twelve-stage washing system is 180 cubic meters per hour, and the rotating speed of the scraper type centrifuge is 3000 revolutions per minute; the volumes of the refined starch milk storage tank, the scraper overflow liquid tank and the filtrate concentration feeding tank are all 60 cubic meters. And the sterilizing liquid enters a process water tank after passing through the horizontal spiral concentrator of the last device, and the sterilized sterilizing liquid is discharged to a sewage treatment station by the process water tank. And finally, cleaning the system by using clean water to complete the whole set of disinfection and sterilization process.

Example 2. example 1 was repeated, except that the concentration of the aqueous solution of nisin in step 2) of the sterilization method for a corn starch production system in this example was 70ppm and the amount of streptococcus lactis was 2.1 kg.

Example 3. example 1 was repeated, except that in this example the concentration of the aqueous solution of nisin in step 2) of the method for the sanitization of a corn starch production system was 120ppm and the amount of streptococcus lactis was 3.6 kg.

Example 4. example 1 was repeated, except that in this example, the concentration of the nisin aqueous solution in step 2) of the sterilization method for a corn starch production system was 160ppm, and the system was sterilized once, and the amount of streptococcus lactis was 4.8 kg.

Example 5. example 1 was repeated, except that in this example, the concentration of the aqueous solution of nisin in step 2) of the sterilization method for a corn starch production system was 200ppm, and the system was sterilized once, and the amount of streptococcus lactis was 6 kg.

Comparative example 1 was repeated, differing from example 1 in that a corn production system was sterilized with a 2% (mass fraction) sodium hydroxide solution as a sterilizing liquid in this comparative example.

Comparative example 2. example 1 was repeated, differing from example 1 in that the corn production system was sterilized in this comparative example using a 3% (mass fraction) sodium hydroxide solution as a sterilizing liquid.

Investigation of antibacterial effect:

The bacteriostatic effect of the sterilization method is determined according to the total colony number determination method in GB4789.2-2016 food microbiology inspection.

TABLE 1 bacteriostatic effect of the method of sterilization according to the invention

The antibacterial effect of the corn starch production system is detected after one month of sterilization, and the result shows that the total number of bacterial colonies in the produced starch milk is still 10 ⁴CFU/m L level, and the total number of colonies in the finished starch product was 6000 CFU/g.

Claims (6)

1. A sterilization method for reducing the level of microorganisms in a corn starch production system is characterized in that nisin aqueous solution is used as sterilization liquid to sterilize equipment used in the corn starch production system.

2. The sterilization method according to claim 1, wherein the working concentration of the nisin aqueous solution is 20 to 200 ppm.

3. The sterilization method according to claim 2, wherein the working concentration of the nisin aqueous solution is 70 to 160 ppm.

4. The sterilization method according to claim 2, wherein the working concentration of the nisin aqueous solution is 120 ppm.

5. The sterilization method according to any one of claims 1 to 4, characterized by comprising the steps of:

(1) Rinsing with clear water: washing equipment used in a corn starch production system with clear water, cleaning materials remained in the equipment and pipelines, and washing the cleaned materials with the clear water;

(2) Preparing the cecidin: mixing nisin with process water to prepare a sterilizing solution with the solution concentration of 20-200 ppm;

(3) And (3) system disinfection and sterilization: and (3) pumping the sterilizing liquid prepared in the step (2) into equipment used in a corn starch washing process and equipment used in a dehydration drying process in sequence by using a pump body, and enabling the sterilizing liquid to flow through each equipment to finish sterilization.

6. The sterilization method according to claim 5, wherein the sterilizing liquid is used in an amount of 1/3 to 1/2 of the volume of the apparatus to be sterilized in step (3).