Microbiological Control of a Milling Tandem

1. Microbiological Control of a Milling Tandem Milling Seminar - May 11, 2005

2. Microbes are Everywhere • Microbes Protect Themselves in nature by: • 1. growing as biofilms • Resistant to penetration by antimicrobials, important in sugar mills • Modifying or excluding antibacterial agent • 2. Forming spores • Most resistant form of bacteria. Generally found in sugar

3. Microbial Biofilm(Heat Exchanger)

4. Commonly Found Genera in Sugar Process Streams • Gum Producers • L. mesenteroides, L. dextranicum • Yeast • Saccharomyces, Torula, Pichia • Common Bacteria • includes Pseudomonas and Bacillus • Filamentous Fungi • Aspergillus, Penicillium, Streptomyces

5. Microorganisms in the Raw House (processing problems) • acid pH and high sugar concentrations in juice favor growth of Streptococci and Leuconostoc • Microbial loading of sugar juices reflects the bacteria flora of the source materials • These gum forming microorganisms form biofilms on the equipment and secrete dextran in the process stream

6. Biofilms • Bacteria have the ability to colonize process surfaces • this leads to build up of slime materials or biofilms. • The biofilm can become an ecosystem with a wide variety of pathogenic and spoilage microorganisms and a penetration barrier for biocides. Rod-shaped bacterium

7. Bacterial Biofilms SEM image ofsixday old Pseudomonas aeruginosa biofilm.

8. Processing Problems due to Polysaccharide Producers • Direct loss of sucrose • Viscosity increase • crystal deformation • sugar loss to molasses • penalties • analytical interference

9. 900 47 46 800 45 700 44 600 43 500 42 ppm Dextran 41 400 40 300 39 200 38 100 37 0 36 1 2 3 4 5 6 7 8 9 week Economic Implications of Dextran TP Dextran

10. Sugar Losses • In Louisiana, molasses purity rise is 2.2 - 2.5 points/ 1000 ppm dextran in juice • a rise in final molasses purity of one point is equivalent to losing one pound of sugar to molasses for every ton of cane processed

11. Role of a Biocide • Control Dextran Formation • Microbiocidal activity • Minimize Biofilm Formation • Residual Activity • Protect Juice from Deterioration in Stagnant Regions • Residual Activity

12. Organic Biocides • Two classes of compounds approved by FDA for use in sugar processing • Carbamates • Quaternary Ammonium compounds • “Quats” may not be present in molasses sold for animal feed

13. Some Results: Initial Trial: 92.17 hours at 30oC No Biocide HgCl2 200ppm NaN3 500ppm 5,10,15,20ppm mDTC NaN3 100ppm mDTC 15 ppm

14. Results: Antibody Dextran on Brix

15. Results: HPLC Sucrose on Brix The Good The Bad The Ugly

16. Mills Biocide Location Dose (ppm) A,B,C,G, Bleach Knives ? Q Last mill D,I,P Busan 881 Knives 0 -18 Last Mill E,J,O,S Midland Last Mill 0.6 - 15 6001 K Magnicide 10 H Bleach + Knives 21 and 10 Midland Last Mil Biocide Use (Louisiana 2001)

17. Control Measures in the Factory • Strict Sanitation procedures • Biocide application at earliest points where juice can contact surfaces. • The maintenance of residual biocide until the juice heaters

18. Effective Dose Rate

19. Summary • Microorganisms are ubiquitous • The “environmental” conditions of the sugar mill dictate which organisms will be found • Microorganisms will consume sugar • Some microorganisms produce products which have processing effects far exceeding what would be expected based on their bulk composition

20. Summary • Microbial growth can be controlled at the mill (but not eliminated) through judicious cleaning (steam, hot water) on a routine basis and by use of a biocide in hard to clean areas • All areas touched by juice can grow biofilms and shed dextran into the process.