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Top 3 in Bacteriophage Control

PREBEN JØRGENSEN, PRINCIPAL APPLICATION SPECIALIST, DAIRY

NOVEMBER 2016

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Top 3 in Bacteriophage Control

In this presentation…

Objective

Background

Disinfection

Cleaning

Flipping Valves

Top 3 Summary

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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%

Background

A common problem

acidification, texture, holeformation etc

4

CRITICAL LEVEL

Number of fermentations

Level and

complexity of

phages

[[[

Starter

A

Starter

B

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

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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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”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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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).

8

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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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CLEANING

Main problems observed:

• Too short time

• Too low temperature

• Acid cleaning only seldom

Cleaning

10

Cleaning reduces the phage loads and makes disinfection possible

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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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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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

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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