Abstract: The microbial status of fermenters has a great impact on the quality of beer. Clean and sterile is the basic requirement for hygiene management in beer production. A good CIP system can effectively clean the fermenter. The problems of cleaning mechanism, cleaning method, cleaning procedure, cleaning agent/sterilizant selection and operation quality of CIP system were discussed.
Foreword
Cleaning and sterilization are the basic work of beer production and the most important technical measure to improve beer quality. The purpose of cleaning and sterilization is to remove as much as possible the dirt generated by the inner wall of pipes and equipment during the production process, and to eliminate the threat of spoilage microorganisms to beer brewing. Among them, the fermentation plant has the highest requirements for microorganisms, and the cleaning and sterilization work accounts for more than 70% of the total work. At present, the volume of the fermenter is getting larger and larger, and the material conveying pipe is getting longer and longer, which brings many difficulties to cleaning and sterilization. How to properly and effectively clean and sterilize the fermenter to meet the current “pure biochemical” needs of beer and meet the consumer’s requirements for product quality should be highly valued by beer brewing workers.
1 cleaning mechanism and related factors affecting cleaning effect
1.1 cleaning mechanism
During the beer production process, the surface of the equipment in contact with the material will deposit some dirt for various reasons. For fermenters, the fouling components are mainly yeast and protein impurities, hops and hop resin compounds, and beer stones. Because of the static electricity and other factors, these dirt have a certain adsorption energy between the surface of the inner wall of the fermenter. Obviously, in order to drive the dirt off the tank wall, a certain amount of energy must be paid. This energy can be mechanical energy, that is, a water flow scrubbing method with a certain impact strength; chemical energy can also be used, such as using an acidic (or alkaline) cleaning agent to loosen, crack or dissolve the dirt, thereby leaving the attached surface; It is thermal energy, that is, by increasing the temperature of the cleaning, speeding up the chemical reaction and speeding up the cleaning process. In fact, the cleaning process is often the result of a combination of mechanical, chemical and temperature effects.
1.2 Factors affecting the cleaning effect
1.2.1 The amount of adsorption between the soil and the metal surface is related to the surface roughness of the metal. The rougher the metal surface, the stronger the adsorption between the dirt and the surface, and the more difficult it is to clean. Equipment used for food production requires Ra<1μm; the characteristics of the surface material of the equipment also affect the adsorption between the dirt and the surface of the equipment. For example, the cleaning of synthetic materials is particularly difficult compared to the cleaning of stainless steel.
1.2.2 The characteristics of the dirt also have a certain relationship with the cleaning effect. Obviously, it is much more difficult to remove the old dirt that has been dried than to remove the new one. Therefore, after a production cycle is completed, the fermenter must be cleaned as soon as possible, which is not convenient, and will be cleaned and sterilized before the next use.
1.2.3 Scour strength is another major factor affecting the cleaning effect. Regardless of the flushing pipe or the tank wall, the cleaning effect is best only when the washing liquid is in a turbulent state. Therefore, it is necessary to effectively control the flushing intensity and flow rate so that the surface of the device is sufficiently wetted to ensure an optimum cleaning effect.
1.2.4 The effectiveness of the cleaning agent itself depends on its type (acid or base), activity and concentration.
1.2.5 In most cases, the cleaning effect increases with increasing temperature. A large number of tests have shown that when the type and concentration of the cleaning agent are determined, the effect of cleaning at 50 ° C for 5 min and washing at 20 ° C for 30 min is the same.
2 fermenter CIP cleaning
2.1CIP operation mode and its effect on cleaning effect
The most common cleaning method used by modern breweries is cleaning in place (CIP), which is a method of cleaning and sterilizing equipment and piping without disassembling the parts or fittings of the equipment under closed conditions.
2.1.1 Large containers such as fermenters cannot be cleaned by means of a cleaning solution. The in-situ cleaning of the fermentor is carried out through a scrubber cycle. The scrubber has two types of fixed ball washing type and rotary jet type. The washing liquid is sprayed onto the inner surface of the tank through the scrubber, and then the washing liquid flows down the tank wall. Under normal circumstances, the washing liquid forms a film attached to the tank. On the wall of the tank. The effect of this mechanical action is small, and the cleaning effect is mainly achieved by the chemical action of the cleaning agent.
2.1.2 The fixed ball washing type scrubber has a working radius of 2 m. For horizontal fermenters, multiple scrubbers must be installed. The pressure of the washing liquid at the outlet of the scrubber nozzle should be 0.2-0.3 MPa; for vertical fermenters And the pressure measurement point at the outlet of the washing pump, not only the pressure loss caused by the resistance of the pipeline, but also the influence of the height on the cleaning pressure.
2.1.3 When the pressure is too low, the action radius of the scrubber is small, the flow rate is not enough, and the sprayed cleaning liquid cannot fill the tank wall; when the pressure is too high, the cleaning liquid will form a mist and cannot form a downward flow along the tank wall. The water film, or the sprayed cleaning liquid, bounces back from the tank wall, reducing the cleaning effect.
2.1.4 When the equipment to be cleaned is dirty and the diameter of the tank is large (d>2m), a rotary jet type scrubber is generally used to increase the washing radius (0.3-0.7 MPa) to increase the washing radius and enhance the washing radius. The mechanical action of the rinse increases the descaling effect.
2.1.5 Rotary jet scrubbers can use a lower purge fluid flow rate than a ball washer. As the rinsing medium passes, the scrubber uses the recoil of the fluid to rotate, flushing and emptying alternately, thereby improving the cleaning effect.
2.2 Estimation of cleaning fluid flow
As mentioned above, the fermenter needs to have a certain flushing intensity and flow rate when cleaning. In order to ensure a sufficient thickness of the fluid flow layer and to form a continuous turbulent flow, it is necessary to pay attention to the flow rate of the cleaning pump.
2.2.1 There are different methods for estimating the flow rate of cleaning fluid for cleaning round cone bottom tanks. The traditional method only considers the circumference of the tank, and it is determined in the range of 1.5 to 3.5 m3/m•h according to the difficulty of cleaning (generally the lower limit of the small tank and the upper limit of the large tank). A circular cone bottom tank with a diameter of 6.5m has a circumference of about 20m. If 3m3/m•h is used, the flow rate of the cleaning fluid is about 60m3/h.
2.2.2 The new estimation method is based on the fact that the amount of metabolites (sediments) precipitated per liter of cooling wort during fermentation is constant. When the diameter of the tank increases, the internal surface area per unit tank capacity decreases. As a result, the amount of dirt load per unit area increases, and the flow rate of the cleaning liquid must be increased accordingly. It is recommended to use 0.2 m3/m2•h. A fermenter with a capacity of 500 m3 and a diameter of 6.5 m has an internal surface area of about 350 m2, and the flow rate of the cleaning liquid is about 70 m3/h.
3 commonly used methods and procedures for cleaning fermenters
3.1 According to the cleaning operation temperature, it can be divided into cold cleaning (normal temperature) and hot cleaning (heating). In order to save time and wash liquid, people often wash at a higher temperature; for the safety of large tank operations, cold cleaning is often used for cleaning large tanks.
3.2 According to the type of cleaning agent used, it can be divided into acidic cleaning and alkaline cleaning. Alkaline washing is especially suitable for removing organic pollutants generated in the system, such as yeast, protein, hop resin, etc.; pickling is mainly to remove inorganic pollutants generated in the system, such as calcium salts, magnesium salts, beer stones, and the like.
Post time: Oct-30-2020