The importance of starch hygiene in starch preparation systems.
Poor starch hygiene results in :-
Molecular breakdown
Loss of binding power
Variations in strength properties
Variations in retention
Variable coating viscosity
Surface sizing problems
Increased microbiological activity stems from :-
- More closed water systems in mills
- Ideal higher temperatures for growth
- Bigger machines / higher production speeds
The microbiological activity of the bacteria can be so fast that one can sometimes measure differences in viscosity within minutes.
Mill example (cationic wet-end starch 3.3% solution).
Viscosity after jet-cooker ~120 mPas.
Viscosity after 15 m3 storage tank ~100 mPas.
Addition point to the machine (150 m pipeline from the storage tank) ~ 1 mPas
i.e. fully degraded (= "water") 1-2 mins. later
This fast degradation by bacteria led to lost filler/fines retention, decreased machine speed, etc..
How to avoid problems :-
Proper design of starch preparation systems
Regular maintenance and cleaning of the starch preparation system
Storage temperature about 60ºC
Biocide use in cooked starch solutions