Transcript Microbiological control of a Milling Tandem

Microbiological Control of a Milling
Tandem
Milling Seminar - May 11, 2005
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
Microbial Biofilm
(Heat Exchanger)
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
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
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
Bacterial Biofilms
SEM image of six day old Pseudomonas aeruginosa biofilm.
Processing Problems due to
Polysaccharide Producers
•
•
•
•
•
•
Direct loss of sucrose
Viscosity increase
crystal deformation
sugar loss to molasses
penalties
analytical interference
ppm Dextran
Economic Implications of
Dextran
900
800
700
600
500
400
300
200
100
0
1
47
46
45
44
43
42
41
40
39
38
37
36
Dextran
2
3
4
5
6
week
7
8
9
TP
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
Role of a Biocide
• Control Dextran Formation
• Microbiocidal activity
• Minimize Biofilm Formation
• Residual Activity
• Protect Juice from Deterioration in Stagnant
Regions
• Residual Activity
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
Some Results:
Initial Trial: 92.17 hours at 30oC
No
HgCl2
NaN3
Biocide 200ppm 500ppm
5,10,15,20ppm
mDTC
NaN3 100ppm
mDTC 15 ppm
Results: Antibody Dextran on Brix
6.00
5.00
Ab Dextran, % brix
4.00
azide, 500 ppm
3.00
HgCl2, 200 ppm
mDTC, 5 ppm
mDTC, 10 ppm
2.00
mDTC, 15 ppm
mDTC, 20 ppm
100ppm:15ppm AmDTC
no biocide
1.00
0.00
0.00
10.00
20.00
30.00
40.00
50.00
Elapsed time, hr
60.00
70.00
80.00
90.00
Results: HPLC Sucrose on Brix
120.00
no biocide
HgCl2, 200ppm
mDTC,5ppm
mDTC, 10 ppm
mDTC, 15ppm
mDTC, 20ppm
100ppm:15ppm AmDTC
Azide, 500 ppm
100.00
Sucrose, % on bx
80.00
60.00
The Good
The Bad
40.00
20.00
The Ugly
0.00
0.00
10.00
20.00
30.00
40.00
50.00
Elapsed time, hr
60.00
70.00
80.00
90.00
Biocide Use (Louisiana 2001)
Mills
Biocide
A,B,C,G,
Q
D,I,P
Bleach
E,J,O,S
K
H
Location
Dose
(ppm)
?
Knives
Last mill
Busan 881 Knives
0 -18
Last Mill
Midland Last Mill 0.6 - 15
6001
Magnicide
10
Bleach +
Knives 21 and 10
Midland Last Mil
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
Effective Dose Rate
7
Log cfu/ml
6
5
4
Bleach
3
Midland
2
1
0
0
5
10
ppm Biocide
15
20
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
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.