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How to prevent Thermophile growth in Milk Evaporators
Karl Kieffer Tetra Pak Inc. February 20, 2013
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How to create low spore powder
►Minimize growth
►Remove spores/spore formers
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Temperature
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Growth of thermophilic microorganisms during 17 hours of production
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1
10
100
1000
10000
0 2 4 6 8 10 12 14 16 18
cfu/
ml
Time hour
Comparison thermophilic count from raw milk to final product
B1-B7 Raw milk thermodures Separator exit
B1 -B7 Cooler exit After HEX
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Best Practices
►Minimize size of heat exchangers in critical range ►Keep separation out of critical range ►Allow cleaning of critical areas
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Cold Milk Separation ► Application:
− Good quality cream − avoid heat treatment − No thermophiles
► Sensitive operation ► Define Temperature
− 40-42 vs 55-60 Deg F
► Lower capacities ► Skimming efficiency
− Very temperature dependent
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Separation Temp vs Skimming
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
40 60 80 100 120 140 160
Ski
mm
ing
Temperature DegF
Temperature not recommended: partially crystallized fat globules
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Line concept with cold RO concentration
Cold separation
Cold RO concentration 25-30% solids
Pasteurization
Evaporation
Drying
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General benefits of solution
Ensuring bacteriological quality ►Keeping temperature low as much as possible
− Eliminate possibility of bacteria growth
►Reduce size of PHE − Less residence time
► Increased solids into evaporator − Higher operating temperature = eliminate possibility for
growth
= Ensuring low count powders
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►Good quality of milk!!!
….And we need
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Spore Removal
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Removing Spores
• Destroy spores
• Bactofugation
• Microfiltration
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Bacteria
• Sensitive to temperature (+161 F) • Sensitive to moisture content • Some cells revert to spore when conditions are unfavorable
Spores
• Resistant to temperature (+250 F)
• Resistant to pH/UV/Pressure
• Resistant to moisture content
• Spore will revert to vegitative cell when conditions improve (time and conditions vary)
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Bacteria vs Spores
0
5
10
15
20
25
30
35
40
45
50
160 200 240 280
Streptococcus Thermophilus
Thermophilic Spores
Sec
onds
Degrees F
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SNF 15–20% Skim Milk
Bactofugated Milk
Bactofugate
Bactofugation ®
SNF 9.1%
SNF 9.1%
•Up to 98% spore removal
•Can install in series
•0.1-0.3% discharge
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• Ceramic membranes for optimum accuracy • Concentration factor 200 on skimmed milk • 99.99% reduction of Spores
Tetra Alcross Bactocatch ►Unit design
Membrane Support
Retentate
Support
Channel
Feed Permeate
kk - 2/20/13
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Summary
• Spore Formers are present in all milk • Heat treatment allows these to multiply • Difficult to destroy • Preventing growth is the surest path to success • Can be removed with separation technology