contamin.pdf (application/pdf-tiedosto)
Papermaking, production and handling of modified starches, and dairy and some other food processes share the sensitivity of the raw materials and process conditions often favourable for microbial growth. Process equipment has large surfaces for microbes to settle and to form biofilms.
Helge: I see that Juha Mentu has been involved in this.
Heat in the dry end of the paper machine or during the ‘cooking’ of industrial starches inactivate fungi and vegetative bacteria whereas heat resistant bacterial spores not only survive but may become activated. Similar selection for heat resistant contaminants occurs by the
pasteurization of liquid foods. Effective cleaning and preservation techniques and good manufacturing practices are required in these processes to maintain high hygienic quality in the end product.
Helge: Keep it clean!
Aerobic endospore forming bacteria are widely distributed in nature. The spores are resistant to heat, desiccation, disinfectants, ionizing radiation and UV light. Bacilli are frequent contaminants in biomaterial-based industrial processes. They represent the major hygienic problem in processes where heat or other treatments kill the competing, non-sporeforming microflora.
Helge: Ok.
The significance of bacilli in foods such as milk products has been studied intensively, but little information is available on their role in industrial processes, e.g. in the production of food packaging materials.
Helge: I see.
Paper and paperboard is produced in large volumes worldwide: in 1999 the production was 12.6 million tons in Finland and 79.5 million tons in Europe. Biocides are used to reduce accumulation of slimes and the subsequent production downtime and deterioration of the technical and hygienic quality of paper and board. One kg of each (effective substance) ton-1 of paper is commonly dispensed into the process at the different stages of production.
Helge: Biocides, yes.
Considering the economic importance of paper and paperboard manufacture, surprisingly little published information is available on the microbes contaminating these processes and the products. This study focuses on the production of food packaging paper and board and a dairy process bringing new knowledge on diverse bacterial contaminants in these biomaterial-based industries.
Helge: Why?
Aerobic bacteria producing heat-tolerant spores (named bacilli in this thesis), are the main contaminant group. The properties of these bacteria relevant to hygiene, food spoilage and food poisoning were studied in this work. The most prevalent pathogenic bacillus in industrial
processes is Bacillus cereus, classified to hazard category 2 (Anon., 1995; European Commission, 1993). An industrially applicable method for differentiating the potentially dangerous, emetic toxin producing strains of B. cereus from the non-producing strains, did not exist when this work was initiated.
Helge: Heat-tolerant...
Strains of B. cereus isolated from food poisoning incidents, from the products and process of food packaging paper and board manufacture and from dairy processes were characterized chemically, biochemically and genotypically. Starch constitutes one to two percent of the dry weight of paper products other than newsprint and some brands of grease proof paper.
Helge: Food poisoning?
Paper industry is thus a major user of modified starches. Over 90 % of the starches used in Finland are used by paper industry, 250 000 tons in 1999. Preservation of industrial starches against microbial deterioration is difficult. The organisms responsible for spoilage have seldom been identified. This gap of knowledge hampered the design of rational strategies for preserving industrial starches against microbial spoilage. Good novel preservation methods with minimal usage of toxic or sensitising chemicals are needed.
Helge: Starches and microbial deterioration.
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Showing posts with label biocides. Show all posts
Showing posts with label biocides. Show all posts
Saturday, February 23, 2008
Monday, December 17, 2007
Paper machine biocides control with PMEU
We are able to control real-world events with a portable PMEU enrichment unit and simulate the microbiological events taking place in a paper machine.
The information is available for analyzis two to three days faster compared to traditional methods. As a result, we can control biocides in a much better way and ensure microbiological activities and non-wanted growth of slime and biofilms.
Chemical companies are providing biociedes supply and effects control services to pulp, paper and board manufacturers. This includes the control of microbiological growth in materials added to the process.
The quality of water to the process does have a vital importance in the packaging industry. The same applies to the beer manufacturing. The beer plant in Nokia has to wait for weeks before they can resume production after the water catastrophe in the city of Nokia in the beginning of December 2007.
The information is available for analyzis two to three days faster compared to traditional methods. As a result, we can control biocides in a much better way and ensure microbiological activities and non-wanted growth of slime and biofilms.
Chemical companies are providing biociedes supply and effects control services to pulp, paper and board manufacturers. This includes the control of microbiological growth in materials added to the process.
The quality of water to the process does have a vital importance in the packaging industry. The same applies to the beer manufacturing. The beer plant in Nokia has to wait for weeks before they can resume production after the water catastrophe in the city of Nokia in the beginning of December 2007.
Tuesday, October 30, 2007
Reducing spending on biocided programs
Paper mills are under enormous pressure to cut costs in order to stay competitive. Mills have responded by undergoing water system closure, reducing spending on biocide programs, and, in some cases, lowering water system temperatures to save energy.
Has this, in turn, lead to worker safety issues and even the longevity of equipment and materials on the paper machine?
How do all of these factors
affect the microbes growing
on the machines?
Has this, in turn, lead to worker safety issues and even the longevity of equipment and materials on the paper machine?
Sunday, October 14, 2007
Biocides
Biocides: "Mini-Encyclopedia of Papermaking Wet-End Chemistry Additives and Ingredients, their Composition, Functions, Strategies for Use BIOCIDES Composition: There are at least two main classes of biocide.
These happen to be the same chemicals that are also widely used for pulp bleaching. Therefore it is convenient for facilities employing these bleaching agents to add small amounts to the paper machine system as well.
The oxidizing action either kills the bacteria and fungi outright, or it weakens the cell walls so that they are more susceptible to the other main class of biocides.
The other class involves highly toxic organic chemicals.
As the names imply, many of them contain sulfur ('thio'-). A possible third category consists of materials that have an ability to inhibit biological film formation, e.g. surfactants such as alkylsulfosuccinates.
On the one hand there are oxidizing agents such as chlorine dioxide and hydrogen peroxide.
These happen to be the same chemicals that are also widely used for pulp bleaching. Therefore it is convenient for facilities employing these bleaching agents to add small amounts to the paper machine system as well.
The oxidizing action either kills the bacteria and fungi outright, or it weakens the cell walls so that they are more susceptible to the other main class of biocides.
The other class involves highly toxic organic chemicals.
Subclasses of toxic biocides go by such names as thiazoles, thiocyanates, isothiazolins, cyanobutane, dithiocarbamate, thione, and bromo-compounds.
As the names imply, many of them contain sulfur ('thio'-). A possible third category consists of materials that have an ability to inhibit biological film formation, e.g. surfactants such as alkylsulfosuccinates.
Function: One has to keep in mind that the main goal is to limit the growth of sessile bacteria, i.e. those that are attached to surfaces. These are the bacteria that tend to build up, cause slime deposits and holes, hurt productivity, and hurt product quality.
Strategies for Use: Grades composed of bleached pulps very often involve a combination of treatments with oxidizing biocides, supplemented by toxic organic biocides. The usual recommendation is to treat each of the incoming streams, including the fresh water, filler slurries, chemical additives and makedown streams, etc.
Special attention has to be paid to the starch preparation area, since starch is such a favored food for slime growth. The level of oxidizing agent (e.g. chlorine dioxide) has to be maintained at a sufficiently low level that there are not any problems with bleaching of dyes or decomposition of starch, etc.
A possible starting level to consider is a residual of 1 ppm of active oxidizing agent in the paper machine system. Hydrogen peroxide, when used as a biocide, is slower to act but longer lasting. As a consequence it needs to be controlled at a higher level of residual activity in the system.
The toxic organic biocides can be selected based on the temperature of the system and on the relative needs to control either bacteria or fungal growth.
It is common to cycle the toxic biocide on and off over periods from several minutes to several hours; by this means it is possible to reach a required threshold of activity and also minimize the cost of chemicals.
Such practices of intermittent addition need to be checked to make sure that they do not cause excessive swings in first-pass retention or other problems. Certain biocides are known to contain anionic dispersants that interfere with retention.
The residual level of oxidizing chemicals is most conveniently estimated by measuring the redox potential of the furnish with a Pt electrode relative to a standard reference electrode.
The effectiveness of a biocide program is best evaluated with a combination of measurements, including petri-dish cultures of water, tests for the presence of biological deposits on surfaces, the slipperiness of wetted surfaces, and the level of smells within the facility.
Cautions: Biocides are probably the most toxic materials present in a paper mill and they need to be treated with great respect.
Biocide addition systems should be installed and adjusted only by highly qualified and authorized people.
Anaerobic conditions under deposits can cause release of hydrogen sulfide, which can build up in such locations as tanks.
Never enter a tank until procedures are followed to make sure that the air is safe.
Ineffective biocide programs jeopardize worker safety, damage mill equipment Pulp & Paper - Find Articles
Ineffective biocide programs jeopardize worker safety, damage mill equipment Pulp & Paper - Find Articles: "Ineffective biocide programs jeopardize worker safety, damage mill equipment Pulp & Paper, Nov 2003 by Robertson, Linda Scrimping :
Mills have responded by undergoing water system closure, reducing spending on biocide programs, and, in some cases, lowering water system temperatures to save energy. How do all of these factors affect the microbes growing on the machines?
Has this, in turn, lead to worker safety issues and even the longevity of equipment and materials on the paper machine?
And, if so, how? The additives and fibers used in the papermaking process support the growth of a wide variety of microorganisms.
Papermakers' concern with microbial contamination usually focuses on visible machine microbial deposits that form holes or sheet defects and lead to runnability problems.
These can cause sheet breaks that force the machine to shut down for unscheduled washups or boilouts.
For example, a drop in pH For example, a drop in pH may signal spoilage of additives or pulp and the potential for foul odors. This article explores the impacts of microbial contamination beyond those that impact paper quality and runnability."
Biocides can cause off-spec production and even contribute to human fatality, but proper testing, such as a rigorous anaerobic audit, can decrease risks and pinpoint problems Paper mills are under enormous pressure to cut costs in order to stay competitive.
Mills have responded by undergoing water system closure, reducing spending on biocide programs, and, in some cases, lowering water system temperatures to save energy. How do all of these factors affect the microbes growing on the machines?
Has this, in turn, lead to worker safety issues and even the longevity of equipment and materials on the paper machine?
And, if so, how? The additives and fibers used in the papermaking process support the growth of a wide variety of microorganisms.
Papermakers' concern with microbial contamination usually focuses on visible machine microbial deposits that form holes or sheet defects and lead to runnability problems.
These can cause sheet breaks that force the machine to shut down for unscheduled washups or boilouts.
Other costly problems
caused by microbes are overlooked
because they tend to be
difficult to identify.
For example, a drop in pH For example, a drop in pH may signal spoilage of additives or pulp and the potential for foul odors. This article explores the impacts of microbial contamination beyond those that impact paper quality and runnability."
- The Tekes CACTUS report in Finnish.
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