Microbiological Control of a Milling Tandem

Milling Seminar - May 11, 2005Milling Seminar - May 11, 2005

Microbes are Everywhere

• Microbes Protect Themselves in Microbes Protect Themselves in nature by:nature by:

• 1. growing as 1. growing as biofilmsbiofilms• Resistant to penetration by Resistant to penetration by

antimicrobials, antimicrobials, important in important in sugar millssugar mills

• Modifying or excluding Modifying or excluding antibacterial agentantibacterial agent

• 2. Forming 2. Forming sporesspores• Most resistant form of bacteria. Most resistant form of bacteria.

Generally found in sugarGenerally found in sugar

Microbial Biofilm(Heat Exchanger)

Commonly Found Genera in Sugar Process Streams• Gum ProducersGum Producers

• L. mesenteroidesL. mesenteroides, , L. dextranicumL. dextranicum• YeastYeast

• Saccharomyces, Torula, PichiaSaccharomyces, Torula, Pichia• Common BacteriaCommon Bacteria

• includes Pseudomonas and Bacillusincludes Pseudomonas and Bacillus• Filamentous FungiFilamentous Fungi

• Aspergillus, Penicillium, StreptomycesAspergillus, Penicillium, Streptomyces

Microorganisms in the Raw House (processing problems)• acid pH and high sugar concentrations in acid pH and high sugar concentrations in

juice favor growth of Streptococci and juice favor growth of Streptococci and LeuconostocLeuconostoc

• Microbial loading of sugar juices reflects Microbial loading of sugar juices reflects the bacteria flora of the source materialsthe bacteria flora of the source materials

• These gum forming microorganisms form These gum forming microorganisms form biofilms on the equipment and secrete biofilms on the equipment and secrete dextran in the process streamdextran in the process stream

Biofilms Bacteria have the ability to colonize process Bacteria have the ability to colonize process

surfacessurfaces this leads to build up of slime materials or this leads to build up of slime materials or

biofilms.biofilms. The biofilm can become an ecosystem with a wide The biofilm can become an ecosystem with a wide

variety of pathogenic and spoilage microorganisms and variety of pathogenic and spoilage microorganisms and a penetration barrier for biocides.a penetration barrier for biocides.

Rod-shaped bacterium

Bacterial Biofilms

SEM image of six day old Pseudomonas aeruginosa biofilm.

Processing Problems due to Polysaccharide Producers• Direct loss of sucrose Direct loss of sucrose • Viscosity increaseViscosity increase• crystal deformationcrystal deformation• sugar loss to molassessugar loss to molasses• penaltiespenalties• analytical interferenceanalytical interference

Economic Implications of Dextran

0

100

200

300

400500

600

700

800

900

1 2 3 4 5 6 7 8 9week

pp

m D

extr

an

363738394041424344454647

TP

Dextran

Sugar Losses

• In Louisiana, molasses purity rise is 2.2 - In Louisiana, molasses purity rise is 2.2 - 2.5 points/ 1000 ppm dextran in juice2.5 points/ 1000 ppm dextran in juice

• a rise in final molasses purity of one point is a rise in final molasses purity of one point is equivalent to losing one pound of sugar to equivalent to losing one pound of sugar to molasses for every ton of cane processedmolasses for every ton of cane processed

Role of a Biocide

• Control Dextran FormationControl Dextran Formation• Microbiocidal activityMicrobiocidal activity

• Minimize Biofilm FormationMinimize Biofilm Formation• Residual ActivityResidual Activity

• Protect Juice from Deterioration in Stagnant Protect Juice from Deterioration in Stagnant RegionsRegions• Residual ActivityResidual Activity

Organic Biocides

• Two classes of compounds approved by Two classes of compounds approved by FDA for use in sugar processingFDA for use in sugar processing• CarbamatesCarbamates• Quaternary Ammonium compoundsQuaternary Ammonium compounds

• ““Quats” may not be present in molasses Quats” may not be present in molasses sold for animal feedsold for animal feed

Some Results:

No Biocide

HgCl2 200ppm

NaN3

500ppm5,10,15,20ppm mDTC

NaN3 100ppmmDTC 15 ppm

Initial Trial: 92.17 hours at 30oCInitial Trial: 92.17 hours at 30oC

Results: Antibody Dextran on Brix

0.00

1.00

2.00

3.00

4.00

5.00

6.00

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

Elapsed time, hr

Ab

Dex

tran

, % b

rix

azide, 500 ppm

HgCl2, 200 ppm

mDTC, 5 ppm

mDTC, 10 ppm

mDTC, 15 ppm

mDTC, 20 ppm

100ppm:15ppm AmDTC

no biocide

Results: HPLC Sucrose on Brix

0.00

20.00

40.00

60.00

80.00

100.00

120.00

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00

Elapsed time, hr

Su

cro

se, %

on

bx

no biocideHgCl2, 200ppmmDTC,5ppmmDTC, 10 ppmmDTC, 15ppmmDTC, 20ppm100ppm:15ppm AmDTCAzide, 500 ppm

The Good

The Bad

The Ugly

Biocide Use (Louisiana 2001)Mills Biocide Location Dose

(ppm)A,B,C,G,

QBleach Knives

Last mill?

D,I,P Busan 881 KnivesLast Mill

0 -18

E,J,O,S

K

Midland6001

Magnicide

Last Mill 0.6 - 15

10H Bleach +

MidlandKnives

Last Mil21 and 10

Control Measures in the Factory

• Strict Sanitation proceduresStrict Sanitation procedures• Biocide application at earliest points where Biocide application at earliest points where

juice can contact surfaces. juice can contact surfaces. • The maintenance of residual biocide until The maintenance of residual biocide until

the juice heaters the juice heaters

Effective Dose Rate

0

1

2

3

4

5

6

7

0 5 10 15 20

ppm Biocide

Lo

g c

fu/m

l

Bleach

Midland

Summary

• Microorganisms are ubiquitousMicroorganisms are ubiquitous• The “environmental” conditions of the sugar The “environmental” conditions of the sugar

mill dictate which organisms will be foundmill dictate which organisms will be found• Microorganisms will consume sugarMicroorganisms will consume sugar• Some microorganisms produce products Some microorganisms produce products

which have processing effects far exceeding which have processing effects far exceeding what would be expected based on their bulk what would be expected based on their bulk compositioncomposition

Summary

• Microbial growth can be controlled at the Microbial growth can be controlled at the mill (but not eliminated) through judicious mill (but not eliminated) through judicious cleaning (steam, hot water) on a routine cleaning (steam, hot water) on a routine basis and by use of a biocide in hard to basis and by use of a biocide in hard to clean areasclean areas

• All areas touched by juice can grow All areas touched by juice can grow biofilms and shed dextran into the biofilms and shed dextran into the process. process.