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Sterile beverage filling.

Hermann Kronseder, Krones chairman, offers a perspective on bottle sterilization in filler or rinser

The degree of automation in filling technology has advanced to the point that permits a line efficiency of 90 percent or better. The pasteurizer, however, requires a significant amount of space and energy and it affects the quality of the beer. Existing cost figures associated with beer pasteurization range between $1.50 and $2.00 U.S. per hectoliter. It was our goal to develop a system to replace the pasteurizer. Without question, sterile beer must be filled into sterile bottles. I am referring to returnable bottles; non-returnable or one-way bottles do not pose a problem.

The function of the bottle washer has never been exactly defined and specified. In my opinion, the bottle washer serves to render the bottles internally sterile and clean on the outside. We do not want to talk about the cost of space requirements and operation or about environmental pollution resulting from bottle washing. We just want to study the efficiency of cleaning the interior of the bottle.

Prior to leaving the machine, the bottle is more or less thoroughly sprayed with fresh tap water. As far as we know now, this final spraying process is unsatisfactory.

Laboratory tests have confirmed that in most cases, tap water is by no means free of germs. We all know from experience that depending on the bottle size, the residual water in the bottles is between two or three ml. Microbiologists confirm that one ml. of residual water may contain up to one million germs. And this is the crucial point.

I am not a microbiologist but a machining engineer. I know from discussions with many brewers that new bottles rinsed with fresh water have often caused complaints. Several breweries stopped using rinsers years ago, and fill the brand new bottles without rinsing them. As a result, complaints stopped. Logically, we concluded that the residual water in the bottles was the reason for the complaints.

I would like to point out a less-known fact: 1 ml. of residual water may contain between 0.01 and 0.04 mg of oxygen per liter. This will further affect the beer quality which quality-minded brewers are not willing to accept.

Secondary contamination in the filling area

Prof. Dr. Werner Back, University of Munich-Weihenstephen, supports our efforts to develop a new technology for bottle cleaning and filling with the following statement: "About 50 percent of the complaints are the result of beer contamination with microorganisms in the filling area."

In a mid-size brewery, the bottles were examined after leaving the bottle washer. The University of Munich-Weihenstephen reports: "One bottle per hour was removed from the filler infeed. The content of the bottle (about 1 ml. residual water) was flushed out with sterile water, filtered through a membrane and incubated on agar nutrient at a temperature of 36 degrees Celsius for a period of five days.

Test results after three days:

--The total number of germs ranged between 0 and 400 per bottle

--Entirely sterile bottles were very rare.

--Up to now, five different types of germs were detected.

There was a relatively high number of germs, although five mg. of chlorine per liter was added to the spraying water and allowed to operate on the germs up to seven hours before filtration. (Beer spoilage organisms were not detected; for this purpose different incubation temperatures and nutrients would have been required.)

The relatively low number of samples allows only a rough statement on contamination with beverage spoiling bacteria. Not all of the germs detected were identified. In general, the following can be stated:

1. Under test conditions, the residual water was never completely sterile.

2. The detected "water bacteria," coliforms and mold fungi are not critical to breweries since they will not survive or reproduce in beer.

3. The lactic bacteria Lb. curvatus detected in one of the cases, however, is beer spoiling.

4. The yeast detected is potentially fruit juice or soda spoiling since it effectively ferments glucose. Mold fungi are also potentially beverage spoiling (fruit juices).

5. The detected "water bacteria" are perfectly normal for drinking water; they are not pathogenic but are indicators of water purity. It is possible that the contamination of sterile plain mineral water with these germs deriving from the bottle cleaning process, reduce the shelf life of the water.

6. Note that even chlorination of the water used for fresh water spraying does not always result in satisfactory hygienic conditions.

7. The source of contamination cannot be clearly determined. Probably the origin of mold fungi, yeasts and beer-spoiling bacteria is not from the spraying water, but rather from contaminated condensed water, insufficient bottle cleaning and ambient air.

The test results indicate that the bottles leaving the bottle washer are by no means sterile. The question whether the contamination is harmful must be clarified for each individual case.

A. "Will the germ detected in the bottle spoil my product?"

B. "Will a potentially pathogenic germ survive in my product?"

C. "Are there legal guidelines to determine the maximum permissible number of germs for my product?"

If so, can these germs enter the bottle during the process of cleaning, normal rinsing or bottle transport (airborne bacteria)?

If one of those questions is answered with a "yes," you must subject the bottle to a subsequent sterilization process which can be chemical in nature (|H.sub.2~|O.sub.2~ or similar incl. disadvantages) or a physical (heat in the form of steam or hot water) process.

Beer sterile filtrate is an absolute prerequisite. Steinecker, our subsidiary, created the required pre-conditions with their proven double powder filtration system.

Sterile bottle interior

As machinery manufacturers, we are aiming to render the bottle's interior sterile without the use of chemical substances and at the same time substantially reduce operating costs. Therefore we have chosen the method of bottle steam sterilization prior to filling. The bottles leave the bottle washer at a temperature of 40 degrees Celsius to 50 degrees Celsius and pass through the bottle inspector. The speed is electronically synchronized to the filler. The bottles are fed by means of the filler infeed worm and infeed starwheel. Prior to filling, they are subjected to saturated steam of 105 degrees Celsius for about two or three seconds. The condensed water in the bottle amounts to between one and three ml. depending on bottle shape and temperature. Laboratory tests in Weihenstephan have shown that previously contaminated bottles will become germ-free after steam sterilization.

After the steam sterilization phase, the bottles are filled via short-tube filler of the new VP generation (incl. a pneumatic valve). The process steps are as follows:

1. Bottle sterilization by means of steam.

2. Bottle flushing by C|O.sub.2~.

3. Pressurizing, filling, snifting.

4. Bottle crowning in the filler.

During the process of steam sterilization, the majority of air contained in the bottle is forced out. This results in comparable values to those obtained with the double pre-evacuation (about 0.03 mg of oxygen per liter).

Bottle crowning in filler

A new crowner applies crowns to the bottles and tightly closes them in the filler carousel immediately after the centering bells are raised. The standard fill discharge starwheel is replaced by the crowner. This eliminates potential contamination of the open bottle as it travels from the filler to the crowner.

Bottle steam sterilization may cause 0.1 to 0.2 percent bottle breakage depending on time and temperature. Tests have shown that this is primarily true for bottles with varying wall thicknesses; as a result, faulty bottles are eliminated. What is interesting is the fact that faulty bottles break during the sterilization phase but not when the cold beer contacts the hot inside bottle surface. This phenomenon significantly reduced the beer loss in the filler and in the crowner.

Steam rinser

A second alternative we have also successfully developed is a steam rinser located before the filler. The process: the bottles leave the bottle washer at a temperature of 40 to 50 degrees Celsius, pass by the inspection machine and enter the blocked steam rinser where the bottles are turned upside down and steam sterilized with hot steam at a temperature of 105 degrees Celsius for a period of two or three seconds. Sterile air is then forced into the bottle for approximately one or two seconds. (The steam leaves the nozzles at a temperature of no more than 100 to 105 degrees Celsius). This process removes the residual and condensed water entirely from the bottle. The bottles leave the rinser and are transferred to a VP type or conventional system where they are filled. External bottle sterilization in the filler with hot water at an interval of two hours and continual spraying of the valve area between the starwheels are strongly recommended.

Accurate measurements show that the contaminated bottles were absolutely sterile after this process and that the residual water in the bottles amounted to no more than 0.1 to 0.2 ml. This process is the preferred method in mineral water and milk bottling plants where all residual water must be eliminated prior to the filling process.

The two methods mentioned will ensure absolutely sterile bottles. We have to point out, however, that these methods are not suitable for aseptic filling as required by the pharmaceuticals industry.

In Japan, the fillers were installed in sterile rooms for long range tests. The rooms were charged with sterile overpressure air to create an absolutely sterile filling environment. At the beginning of the filling process, the room was germ free. After two hours of operation, the microbial germination of the filler and the room was equal to the area outside of the sterile room. This test demonstrates that the high cost of a sterile room is not justified since it does not maintain a sterile environment.

What are the alternatives for practical application, considering the fact that a bottling line is supposed to have a service life of at least 10 to 15 years. It is a fact that, worldwide, the quality of drinking water has become worse. And it does not appear that it will improve in the near future. More likely it will become even worse.

Krones offers a complete package for sterile beverage filling including germ-free filtration, bottle steam sterilization in the filler or in a blocked steam rinser. The beverage sterile filling system was developed one year ago and is already in operation in several well-known breweries. It goes without saying that Krones is able to offer lines for sterile can filling as well. The cost for these systems is substantially lower than the cost of a pasteurizer.

The advantage of this new filler generation is that a normal VP filler with single or double pre-evacuation can be changed into a BSF system including bottle steam sterilization. However, if a rinser is to be added to a VP filler at a later date, this must be taken into consideration when placing the order.

Today, hygienic regulations are adhered to more strictly than a few years ago. Note particularly the machine guidelines which are obligatory in the member countries of the European Community. In the Federal Republic of Germany, a law on machine guidelines was also provided to ISO, a committee for worldwide machinery standardization. The Federal Republic will probably soon follow the requirements of the EC machine guidelines worldwide.

Hermann Kronseder is the chairman of the board of Krones A.G., Neutraubling, Germany.
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Title Annotation:bottle sterilization
Author:Kronseder, Hermann
Publication:Modern Brewery Age
Date:Jan 25, 1993
Previous Article:Sales compensation mix.
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