Presentation by Preben Jørgensen, Principal Application Specialist in Dairy, DuPont Nutrition & Health "Three ways to effective bacteriophage control in fermented dairy production".

1. Top 3 in Bacteriophage Control
PREBEN JØRGENSEN, PRINCIPAL APPLICATION SPECIALIST, DAIRY
NOVEMBER 2016

2. Top 3 in Bacteriophage Control
In this presentation…
Objective
Background
Disinfection
Cleaning
Flipping Valves
Top 3 Summary
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3. Top 3 in Bacteriophage Control
Objective
To focus phage control input on activities with best
results (the 80/20 rule – Pareto)
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Input,
20%
Result,
80%

4. Background
A common problem
acidification, texture, holeformation etc
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CRITICAL LEVEL
Number of fermentations
Level and
complexity of
phages
[
[
[
Starter
A
Starter
B

5. DISINFECTION
Only following works against
bacteriophages – prioritized list:
• Per acetic acid
• Hot water (> 90ºC)
• Chlorine based compounds
• Steam
When used, often too short and too
low concentration or temperature
Disinfection
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Lack of (correct) disinfection is the most common cause of bacteriophage
problems

6. Disinfection – 8 Log Reductions = GMP
IMPORTANT: Requires a clean surface (no biofilm)
Hot water:
• 90ºC/40min-95ºC/20-30min (194-203ºF)
• the time starts WHEN the temperature has been reached
in the return pipe or in the tank
Per Acetic basis:
• 450 ppm (% des. = ppm/(100 x %PA in des.agent))
• 20ºC for 20 minutes (68ºF)
• Concentration in des.agent might decrease during storage
Active Chlorine basis (sodium hypochlorite):
• minimum 200 ppm active chlorine (normally 10-15% act.cl.)
• 30-40ºC for 20 minutes (86-104ºF)
Steam:
• 95ºC for 15-30 minutes (203ºF)
Lack of
disinfection is
the most
frequent cause
of
bacteriophage
problems!
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7. 7
”Lines of equal effect” on thermal
treatment in milk of two selected
Lactococci attacking bacteriophages
P008 (heat labile) and P1532 (heat
stabile)
Mareile Müller-Merbach
University Hohenheim, Stuttgart
March 2007
Thermostability of selected bacteriophages
900=15 min
1800=30 min
9095
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8. Desinfection Agent % Time Log reductions
PAA 0.5% 15 min 8-9
hypo chlorite 0.5% 10 min 7-8
Cloramine 0.2% 10 min 7-8
Formaline 0.6% 2 hours 8
Lye, acids 1-2 hours 1-2
Phenol 2% 1-2 hours 1-2
Hydrogen peroxide 6% 1-2 hours 1-2
8 Log Reductions – Every Day/Every Batch
To avoid an increasing phage load in the factory, it is
recommended to go for a daily log reduction of 8.
Literature:
Lembke, et al:
0.5% PAA, Log
reductions: 5
min: 3-4, 10 min:
6-7, 15 min: 8-9
(One Log
reduction is a
reduction with
a factor 10).
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9. Disinfection requires a clean surface
Disinfection made difficult:
Presence of proteins
Biofilms created by residual live bacteria
Milk stone deposits
Level of residual microbiota
Phage contamination level
Hard water used for cleaning
Important:
Control after cleaning :
• Regular SWAP test of selected
critical points after cleaning
• In case of phage problems –
after every cleaning
• Total plate count or ATP test
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10. CLEANING
Main problems observed:
• Too short time
• Too low temperature
• Acid cleaning only seldom
Cleaning
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Cleaning reduces the phage loads and makes disinfection possible

11. Total cleaning time 45-55
minutes
Water hardness -> demand for
additional chemicals
1. Flush with water
2. Lye (2% NaOH), 70-90°C for
minimum 20 minutes (158-
194F)
3. Flush with water
4. Acid (0.5 % HNO3), 60-70°C
for 10-15 minutes (water
hardness) (140-158F)
5. Final flush with fresh water
Cleaning of Tanks, Pipes, Fittings etc.
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12. Flipping Valves
Tanks and pipes/fittings after pasteurising and up to and including the cheese
tanks/fermentation tanks:
Avoid „flipping“ valves connecting 2 pipe systems – smart but very
demanding in relation to cleaning and disinfection
For each diverted pipe system:
• double time for cleaning and disinfection
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13. 13
Example: Standard Fermentation Tank
Picture from the ”Dairy Handbook” by Tetra Laval 13
During CIP: 50/50 or 99/1 flip?
case 1: standard 20 min
disinfection
10/10 min or 19min48sec/12sec

14. Top 3 Summary
Disinfection: Top 1 problem – seldom done correct
Cleaning: too short time
Flipping valves: common, but no adjustment of CIP procedures

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