Monday, February 25, 2008

Mineral pigments and fillers as a hazard to the paper production hygiene?

"Microbial contaminants will decrease the quality of pigments and fillers in paper and board industry. Microbe-caused spoilage of these raw materials as well as indirect deteriorative effects of these spoiled additives on the machine housekeeping, production and hygienic properties of paper products are well-known problems at the mills." (MENTU, J. et al. 1997. Microbiological Control of Pigments and Fillers in Paper Industry. In: Transactions of the 11th Fundamental Research Symposium in held at Cambridge: September 1997. PIRA International, Surrey,UK).

If we start to examine the routes of microbes into the paper manufacturing processes, mineral pigments and fillers have a role as one of the most important agents to contaminate the paper and board production processes.

This is caused by the characteristic features of these additives: they are (excl. Precipitated Calsium Carbonate) all originated from rocks and contain high counts of soil microbes: spore-forming and other bacteria as well as fungi. Depending of the further treatments of the raw minerals, the quality of minerals will get better or worser. A wide variation of colony counts can be detected in mineral slurries, ranging from 0 to over 10 000 000 cfu/ml!

Biocidic treatment of minerals is a challenging tasks for several reasons. Bacterial spores (very common form of bacteria in minerals) tolerate traditional biocides better than vegetative bacteria; minerals have microbe-covering effects; long transportation and storing periods give extended growth time for microbes etc.

Paper machines need minerals day and night. This everlasting input of mineral-borne bacteria acts as a significant contamination route. Control methods to detect spoiled lots and CCP's of the "coating kitchens" should work very fast and give early warnings in emergence situations as well as documentation of the overall quality of different brands of minerals.

How to build up this kind of reliable mb control for mineral pigments and fillers?

Some new alternatives of traditional, long-lasting and labourious colony count analyses really exists today.

1 comment:

Helge V. Keitel said...

Juha, please write more. I like this background better than black and white.

Your content is great. Continue with new postings.