Thermal Control of
Dairy Bacteriophage
White Paper
Thermal Control of Dairy Bacteriophage
TABLE OF CONTENTS
EXECUTIVE SUMMARY......................................................................................................3
INTRODUCTION TO SPX FLOW TECHNOLOGY ..................................................3
Vision and commitment...................................................................................................... 3
Customer focus .................................................................................................................. 3
INTRODUCTION TO BACTERIOPHAGE ...................................................................4
MORPHOLOGY AND TAXONOMY.................................................................................4
LIFE CYCLES.............................................................................................................................6
BACTERIOPHAGE IN THE DAIRY................................................................................8
CONTROLLING BACTERIOPHAGE IN THE DAIRY ENVIRONMENT........8
GENERAL RECOMMENDATIONS................................................................................8
KILLING PHAGE BY HEAT TREATMENT...................................................................8
LOGARITHMIC REDUCTION............................................................................................8
PHAGE LETHAL TIME AND TEMPERATURE COMBINATIONS
ACHIEVED WITH SPX FLOW TECHNOLOGIES....................................................9
THERMAL TREATMENT OF WHEY PROTEIN CONCENTRATES
AND CONTROL OF BACTERIOPHAGE USING APV LEANCREME™
TECHNOLOGY....................................................................................................................... 11
REFERENCES....................................................................................................................... 12
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Thermal Control of Dairy Bacteriophage
Executive Summary
Introduction to SPX Flow
Technology
The APV LeanCreme™ technology involves the addition of
VI S ION AN D COM M ITM E NT
microparticulated whey protein concentrate to be added to
SPX's Flow Technology segment designs, manufactures
cheese milk as a means of increasing cheese yield and/or
and markets process engineering and automation
to reduce the fat content of the cheese whithout comprim-
solutions to the dairy, food, beverage, marine,
ising product taste, flavour and texture.
pharmaceutical and personal care industries through its
This white paper describes bacteriophage and explains
global operations.
how to reduce the possibility of phage attack on the cheese
We are committed to helping our customers all over the
starter culture whilst maintaining the essential functional-
world to improve the performance and profitability of
ity of APV LeanCreme™. It is demonstrated that the time/
their manufacturing plant and processes. We achieve this
temperature conditions applied during the microparticula-
by offering a wide range of products and solutions from
tion process are sufficient to destroy most of the less heat
engineered components to design of complete process
resistant bacteriophage encountered in dairies. However,
plants supported by world leading applications and
some high heat resistant strains being able to survive tem-
development expertise.
peratures of 115°C. If there is a concern for these specific
strains then LeanCreme has to be combined with non-heated based methods to prevent phage contamination.
We continue to help our customers optimise the
performance and profitability of their plant throughout its
service life with support services tailored to their individual
As a matter of fact, it is not recommended to apply
needs through a coordinated customer service and spare
temperatures above 85ºC to 90ºC in order to destroy all
parts network.
phage as it will cause excessive denaturation of the microparticulated whey protein with the result that less protein
will be incorporated into the cheese.
Whatever heat treatment is applied it is a general recommandation to combine the heat treatment with e.g. culture
rotation and chemical cleaning to limit the presence of
phage. It is not just a matter of heat treatment. By having a
low growth of phage as a starting point for a stream means
C U S TO M E R F O C U S
Founded in 1910, APV, an SPX Brand, has pioneered
groundbreaking technologies over more than a century,
setting the standards of the modern processing industry.
Continuous research and development based on
customer needs and an ability to visualise future process
requirements drives continued mutual growth.
that a gentler heat treatment is required (lower logarithmic
reduction). The quality of the final product in terms of microbiology, taste and texture can hereby be preserved.
3
Thermal Control of Dairy Bacteriophage
Introduction to bacteriophage
Fermentation defects or failures in products like cheese and
fermented milk products can result in changes in texture, gas
formation and flavour of the products. Fermentation failures can,
among others issues, be caused by bacteriophage contamination and therefore understanding the role of bacteriophage
and what can be done to avoid them, is important. One way of
controlling bacteriophage is by thermal treatment.
M O R P H O L O GY A N D TA XO N O M Y
Bakthrion (bakterion) = bacteria
Fagoz (phágos) = to eat
Bacteriophage is a virus that replicates itself using hosting bacteria. The term is commonly used in its shortened form, phage.
Phage comes from the Greek work “phagein” and means “to
Bacteriophage are a natural part of our surroundings and are
eat” - bacteriophage can literally be translated to “to eat bacte-
amongst the most common organisms on Earth, e.g. 10 million
ria” (http://en.wikipedia.org/wiki/Bacteriophage).
bacteriophage exist in one single millilitre of sea water and exist
in general in the biosphere and therefore also in the air (http://
en.Wikipedia.org/wiki/Bacteriophage). This partly explains why
bacteriophage cannot be fully avoided. In the case of dairies
some species of bacteriophage are not wanted due to risk of
fermentation failures. However, a lot can be done to limit the
occurrence.
Below is an electron micrograph showing a number of bacteriophage invading a bacterium.
F I G . 2 A : A N E L E CT R O N M I C R O G R A P H ( H T T P : / / W W W. M A N S F I E L D .
O H I O - S TAT E . E D U / ~ S A B E D O N / B E G _ P H A G E _ I M A G E S . H T M A N D H T T P : / /
E N.W I K I P E D IA.O R G /W I K I / BACTE R I O P HAG E)
H EAD CONTA I N I N G D N A
COLLAR
S H E AT H
B AS E P L AT E
TA I L F I B R E S
F I G . 1 : E L E C T R O N M I C R O G R A P H S H OW I N G B ACT E R I O P H AG E I N VA D -
F I G . 2 B : A S C H E M AT I C I L L U ST R AT I O N O F B A CT E R I O P H A G E , ( H T T P : / /
I N G A B ACT E R I U M , ( H T T P : / / E N . W I K I P E D I A . O R G / W I K I / B ACT E R I O -
W W W. M A N S F I E L D . O H I O - S TAT E . E D U / ~ S A B E D O N / B E G _ P H A G E _ I M A G -
P HAG E)
E S.HTM AN D HTTP:// E N.W I K I P E D IA.O R G /W I K I / BACTE R I O P HAG E)
4
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Thermal Control of Dairy Bacteriophage
Phage infect bacteria and the properties of the bacteria can
All phage have a head which contains the DNA or RNA genetic
be changed or even destroyed. These changes are often not
material. Many but not all phage have tails. The base plate and
harmful and may even be beneficial. However, in fermented
tail fibres are involved in binding of the phage to the bacterial
dairy products like cheese and yoghurt where starter cultures
cell. Bacteriophage are often much smaller than bacteria – usu-
are used, such changes are not wanted since the fermentation
ally between 20 to 200 nm (Madigan et al., 2000).
process can be retarded or completely stopped.
For practical reasons, bacteriophage are classified according to
Bacteriophage come in many different sizes and shapes. The
the International Committee on Taxonomy of Viruses (ICTV). As
basic structure is illustrated in the electron micrograph and
can be seen in Table 1 below, the morphology determines the
schematic drawing on figs. 2a and 2b.
classification, e.g. if a phage has tail or not.
B R A D L E Y ( 19 67 )
NAM E
M O R P H O LO GY
A C K E R M A N N & D U B OW ( 19 87 )
NAM E
M O R P H O LO GY
I C T V ( 19 8 2 )
FA M I LY
GENUS
A
A1, A2, A3
M YOV I R I D A E
-
B
B1, B2, B3
S I P H OV I R I D A E
-
C
C1, C2, C3
P O D OVI R I DAE
-
D1
M I C R OV I R I D A E
M I C R OVI R U S
D2
N OT C L A S S I F I E D
-
D3
C O RTI C IVI R I DAE
C O RTI C OVI R U S
D4
T E CT I V I R I D A E
T E CT I V I R U S
E1
LEVIVI R I DAE
LEVIVI R US
E2
CYST I V I R I D A E
CYSTO V I R U S
D
E
F1
F
I N OVI R U S
I N OV I R I D A E
F2
-
G
P L E C TO V I R U S
P L A S M AV I R I D A E
P L A S M AV I R U S
TA B L E 1 : C O M PA R I S O N O F P H AG E C L AS S I F I CAT I O N BY B R A D L E Y ( 1 9 67 ) , BY A C K E R M A N N A N D D U B O W ( 1 9 87 ) A N D BY T H E I N T E R N AT I O N A L C O M M I T T E E O N TA X O N O M Y O F V I R U S E S ( I CT V, 1 9 8 2 )
2 2 0 0 6 - 0 3 - 1 1 - 2 01 2 - G B
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Thermal Control of Dairy Bacteriophage
F I G 4 : . S C H E M AT I C S H O W I N G T H E P R O C E S S O F B A C T E R I O P H A G E
H O ST I N G B A CT E R I A ,
H T T P : / / W W W. M A N S F I E L D . O H I O - S TAT E . E D U / ~ S A B E D O N / B E G _ P H A G E _
I MAG E S.HTM
F I G . 3 . LY T I C A N D LYS O G E N I C B ACT E R I O P H AG E I N F E CT I O N .
H T T P : / / E N . W I K I P E D I A . O R G / W I K I / LY T I C _ CYC L E
L I F E CYC L E S
(attaching) before it penetrates the tail into the host cell. Finally
The process of “infection” is where a virus genome (e.g. DNA)
the DNA of the phage is injected into the cell.
is introduced into a host cell and reproduces (Madigan et al.,
2000).
Some bacteriophage can propagate by both the lytic and the
lysogenic cycle, and are normally referred to as “temperate”
Phage can reproduce via two different life cycles - the lytic and
phage. In the lysogenic cycle, the host and phage form a
the lysogenic cycle. See fig. 3.
symbiosis. The phage genome is integrated into the host
Some phage replicate via the lytic cycle and are normally
referred to as “virulent ”. In the lytic life cycle, the phage open
(lyse) the bacterial cell resulting in destruction.
When virulent bacteriophage infect bacteria, sub-units of phage
are synthesised, assemble and finally mature phage is released.
The host cell is killed. The released phage are now ready to
infect a new bacterium.
Fig. 4 illustrates the process of the DNA injection in detail. First
step is the landing of the phage onto the living cell. The landing
can only occur if specific bacteria cell surface components,
called receptors, match the tail fibres of the phage. There is a
high specificity in this landing step like the match of a key and
lock.
One way for the bacteria to defend it self is to have no recep-
genome and replicated with it. At some point in time, phage
is released and enters into the lytic phase. The majority of
Lactococcus lactis phage strains are lysogenic.
The period from landing of phage to assembly and release of
phage is called the latent period. The burst size is the number
of phage released from each bacterium. This number can vary
from 200 to less than 10 and is phage specific.
The consequence of infected bacteria in a fermentation process
can be slow acidification or stagnancy. In practice, the fermentation period has to be extended to reach the normal fermentation
pH. The fermentation curves differ greatly if the burst size is
high. On the other hand, if the burst size is low the fermentation
curve may not differ significantly at first sight. Schematic illustration of the influence of burst size on the fermentation curve
can be seen in the graphs.
tors. If the receptors exist, the second step is the phage pinning
6
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Thermal Control of Dairy Bacteriophage
F I G . 5 . E X A M P L E S O F C O M P U T E R S I M U L AT E D F E R M E N TAT I O N C U R V E S W I T H B A C T E R I A I N F E C T E D BY P H A G E W I T H B U R S T S I Z E S O F 2 0 A N D 10 0
(I DF NO. 308, 1995)
As can be seen the number of bacteria decreases as the
the starting number of phage is higher with the result that the
number of bacteriophage increases. In these examples a burst
fermentation curve stagnates.
size of 20 results in prolonged fermentation time and burst size
of 100 results in stagnation of pH.
In the graphs in fig. 6, the burst size is just 7, which is low. At
Bacteriophage tend to mutate spontaneously in response to
changes in environment which can make them aggressive e.g. if
starter culture rotation is not done.
day 1, the fermentation seems normal. However, at day two
F I G . 6 . C O M P U T E R S I M U L AT E D E F F E CT O F T I M E O N F E R M E N TAT I O N C U R V E S W I T H B A C T E R I A I N F E C T E D BY P H A G E W I T H A B U R S T S I Z E O F 7 ( I D F
NO. 308, 1995)
2 2 0 0 6 - 0 3 - 1 1 - 2 01 2 - G B
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Thermal Control of Dairy Bacteriophage
BAC T E R I O P H AG E I N T H E DA I RY
The presence of phage cannot be avoided but a lot can be done
It has been estimated that dairies experience phage-induced
to limit their presence. Below are general recommendations as
fermentation failure in 0.1. – 10% of the batches. 95% of the
to how to avoid bacteriophage contamination.
phage problems in dairies are caused by the phage species of
936, P335 and C2.
The most important and most widespread phage to Lactococcus
lactis is P008. It is therefore the most investigated phage for
this bacterium. The latency period and burst size are dependant
on the incubation conditions. It has been found that under optimal conditions, the latency period is 24 to 37 min and the burst
size is 7 to 22. In other words one P008 phage usually takes
30 minutes to replicate it self to 7 to 22 phage. This is a rather
quick replication and is even faster than the host bacterium itself
(Müller-Merbach 2007).
Phage P008 is accepted as the official type phage for Lactococcus lactis phage species 936 representing the Siphoviridae
G E N E R A L R E C O M M E N D AT I O N S
• Culture rotation and use of highly concentrated direct starters
(deep frozen or spray dried)
• Apply an efficient heat treatment to the whey
• Hygienic design of plant, e.g. avoid dead ends and reflux
• Handling of whey and whey plant. Personnel working with
whey should preferably not work with the starter culture and
should not be in contact with the fermentation process. The
fermentation process should, as far as possible be a closed
process
• Sufficient and regular cleaning, and disinfection with
appropriate agents
• Handling of air with use of high efficiency particulate air
family of morphotype B1. P008 is approved by the Lactococcal
filtration of incoming air and slight overpressure in processing
and Streptococcal Phage Study Group, Bacterial Virus Subcom-
rooms
mittee, ICTV as the test phage in the European standard CEN/
TC 216/WG3 N 42: "Chemical disinfectants and antiseptics
- Quantitative suspension test for the evaluation of virucidal
activity of chemical disinfectants and antiseptics used in food,
industrial, domestic, and institutional areas.
• Break the reincorporation of by products into the milk
regularly (e.g. whey and whey cream)
K I L L I N G P H AG E BY H E AT T R E AT M E N T
Killing and inactivation of bacteriophage infecting lactic acid
bacteria has been of interest ever since phage were observed
P1532 and P680 are the most heat resistant Lactococcal bac-
and caused fermentation failures in milk. Literature information
teriophage in milk systems investigated until now. Both of them
has been controversial. However, newly extensive investigations
belong to the Lactococcus lactis phage and the 936 species
provide data to calculate process conditions that assure adequate
(Müller-Merbach 2007). P1532 is extremely heat stable but also
phage destruction to prevent fermentation failure. Whey can carry
very rare. P1532 was detected in 0.7 % of investigated dairies
up to 107 to 109 PFU/ml (Atamer el., 2009). Plaque Forming
and is therefore extremely rare (Dogan et al., 2008).
Units is a measure of the number of particles capable of forming
Phage of the host Lactococcus lactis and Lactobacillus helveticus bacteria is known to be relatively stable compared to Lactobacillus delbrueckii and Streptococcus thermophilus phage.
C O N T R O L L I N G BACT E R I O P H A G E I N T H E
DA I RY E N V I R O N M E N T
plaques per unit volume. It is a functional measurement rather
than a measurement of the absolute quantity of phage.
LOGAR ITH M I C R E D U CTI ON
When micro-organisms are exposed to heat treatment, not all of
them are killed at once.
Phage enter the dairy via raw milk and whey. Some phage may
However, in a given period of time a certain number are killed
survive normal pasteurisation. Inside the dairy they are mainly
whilst the remainder survives. If the surviving micro-organisms
spread in the whey and recirculation of whey cream can poten-
are once more exposed to the temperature treatment for the
tially accelerate phage contamination problems. Reincorporation
same period of time an equal proportion will be killed. On this
of milk components must therefore, be handled under carefully
basis, the lethal effect of sterilisation can be expressed math-
controlled conditions.
ematically as a logarithmic function having a first order kinetic.
8
2 2 0 0 6 - 0 3 - 1 1 - 2 01 2 - G B
Thermal Control of Dairy Bacteriophage
K*t = log N/Nt
P H AG E L E T H A L T I M E A N D T E M P E R AT U R E
C O M B I N AT I O N S AC H I E V E D W I T H S P X F LOW
Where TE CH N OLOG I E S
N = number of micro-organisms/bacteriophage
In terms of phage risk, thermal treatment has the potential
Nt = number of micro-organisms/bacteriophage present after a
given time of treatment (t)
to increase the safety of fermentation process. To determine
optimal thermal treatment for a specific case it should be more
effective than a normal pasteurisation but less destructive than
K = constant
that required for heat sterilisation.
t = time of treatment
The time temperature graph on the next page shows the so
A logarithmic function can never reach zero, which means that
called “lines of equal effect”. Lines of equal effect indicate
100 % elimination is impossible to achieve. Therefore the more
combinations of time and temperature which lead to an equal
workable concept of “sterilising effect” or “commercial sterility”
effect of a reaction, e.g. an equal degree of phage inactivation
is commonly applied. Table 2 shows an example of the influence
or destruction of vitamin B1 (thiamine). Lines for the widespread
of log reductions on survivors and killed phage. In this case the
phage P008 and for the rare and extremely heat stable phage
starting point is 100,000,000 (108) of phage. Raw milk might
P1532 are given for log 9 reductions. In an investigation 0.7
have up to 103 PFU/ml.
of samples from dairies were infected by P1532, so this is an
Having a log reduction of 8 in this example gives 1 surviving
phage out of 100,000,000.
LO G
R E D UCTION
extremely rare phage (Dogan et al., 2008). Log 9 reduction is
usually sufficient for concentrated milk components like whey
protein concentrates (WPC’s) as WPC often has a higher
S U R V I VO R S
K I L L E D P H AG E
U N IT
OF
TI M E
level of bacteriophage than raw milk. Referring to table of log
reduction it can be seen that the initial level of bacteriophage is
important in determining the heat treatment that is given.
0
100.000.000
0
0
1
10.000.000
90.000.000
1
A general rule is to aim for a threshold of 1 PFU/ml on the basis
2
1.000.000
99.000.000
2
3
100.000
99.900.000
3
of the rate of phage reproduction. Assuming a reproduction
4
10.000
99.990.000
4
5
1.000
99.999.000
5
6
100
99.999.900
6
7
10
99.999.990
7
8
1
99.999.999
8
According to fig. 7, a 9-log reduction of the commonly found
9
0,1
99.999.999,9
9
10
0,01
99.999.999,99
10
phage P008 can be reached with temperature and time com-
11
0,001
99.999.999,999
11
12
0,0001
99.999.999,9999
12
13
0,00001
99.999.999,99999
13
TA B L E 2 . OV E R V I E W O F L I N K B E T W E E N LO G R E D U CT I O N , S U R V I V -
according to phage P008 and optimum growth conditions, the
phage titre will increase from 1 PFU/ml to a maximum of 107
PFU/ml during a 4 hour long fermentation. This should not put
the fermentation at risk yet (Müller-Merbach, 2007).
bination ranging from 70°C for 20 min to 90°C for 1 sec. and
therefore pasteurisation is normally not sufficient. A log reduction of 9 is a high reduction
Other milk components are also affected by a given temperature
I N G P H AG E , K I L L E D P H AG E A N D U N I T O F T I M E F O R A C O N S TA N T
and time as can be seen in the temperature time graph. The
H E AT T R E AT M E N T T E M P E R AT U R E .
challenge is to find the optimal time and temperature for a given
process without destroying the end product taste and texture.
As an example, the loss of vitamin B1 and denaturation of whey
proteins can be mentioned. Vitamin B1 is normally not wanted to
2 2 0 0 6 - 0 3 - 1 1 - 2 01 2 - G B
9
Thermal Control of Dairy Bacteriophage
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F I G . 7. T E M P E R AT U R E T I M E G R A P H S O F M I L K I N D I CAT I N G L I N E S O F E Q U A L E F F E C T I N C L U D I N G I N A C T I VAT I O N O F T H E M O S T C O M M O N B A C T E R I O P H A G E P 0 0 8 , T H E E X T R E M E LY R A R E A N D H E AT R E S I STA N T B ACT E R I O P H A G E P 1 5 3 2 . R E G I O N O F T Y P I CA L L E A N C R E M E T E M P E R AT U R E A N D T I M E
C O M B I N AT I O N S A R E S H O W E D . ( K E S S L E R , 2 0 0 2 A N D ATA M E R E L A L . , 2 0 0 9 , M O D I F I E D )
10
2 2 0 0 6 - 0 3 - 1 1 - 2 01 2 - G B
Thermal Control of Dairy Bacteriophage
be lost, since it is an important vitamin. In general, short time and
cheese, yoghurt, ice crème among others). This high function-
higher temperature is most gentle to the product compared to
ality is indeed based on a loose and open structure enabling
long time and lower temperature.
active sites of the protein to interact with the components in the
T H E R M A L T R E AT M E N T O F W H E Y P R OT E I N
milk (Spiegel, 1999).
C O N C E N T R AT E S A N D C O N T R O L O F
In conclusion the optimal heat treatment and shear can create
BACT E R I O P H AG E U S I N G A P V L E A N C R E M E ™
an extremely high quality of microparticulate can be produced to
T E C H N O LO GY
boost the sensory and structural quality of the end product, while
The APV LeanCreme™ process is a thermal treatment of WPC
at the same time preventing contamination of the most common
(whey protein concentrate) with scrape surface heat exchang-
bacteriophage encountered in dairy.
ers realising the denaturation and the microparticulation of the
whey proteins in the very same steps. The microparticles formed
with LeanCream have an exceptionally high functionality, water
Raw milk
binding ability and when added back to the cheese milk they will
stay trapped in the cheese curd (Steffl, 1999; Spiegel, 1999).
Risk of bacteriophage
However, since whey protein concentrate can potentially contain
bacteriophage, it is important to control the phage by thermal
treatment before adding it to the cheese milk in addition to the
Whey protein particles
Cheese milk
general recommendations previously mentioned . The block flow
Starter culture
diagram of a typical cheese manufacturing plant Fig. 8 shows
examples of the flow of whey in a typical facility.
Thermal control
The combination of time and temperature of the APV LeanCre-
processing
me™ technology is flexible and can easily be changed. Typical
optimal holding time is 60 to 120 seconds and typical optimal
Cheese
Whey concentrate
temperatures are in the range of 82°C to 88°C.
As can be seen from fig. 7, the P008 phage are killed with a
high log reduction under these heat treatment conditions. This
Concentration
Risk of bacteriophage
complies fully with practical experience as SPX Flow Technology
has no recorded cases of bacteriophage issues from microparticulated whey protein produced using APV LeanCreme™
Whey drainage
Pasteurisation
technology.
It is not recommended to apply higher combination tempera-
Whey
Brining
Risk of bacteriophage
Risk of bacteriophage
ture/time of denaturation as it it is known that the application of
higher temperatures with the same range of holding time creates a different more compact structure of the microparticulated
whey to the extent that less is incorporated into the cheese
Cheese
matrix.
F I G . 8 . F LO W C H A R T O F A C H E E S E P R O C E S S I N W H I C H C O N C E N -
Higher temperature would dramatically and irreversibly alter
the whey microparticles high level of functional properties are
T R AT E D W H E Y P R OT E I N S A R E B E I N G R E I N C O R P O R AT E D I N TO T H E
C H E E S E M I L K T H E R M A L C O N T R O L O F W P C I S E S S E N T I A L TO AV O I D
F E R M E N TAT I O N FA I L U R E S CA U S E D BY B A CT E R I O P H A G E .
formed, e.g. high water binding ability, high creaminess perception and high level of incorporation in the dairy matrix (e.g.
2 2 0 0 6 - 0 3 - 1 1 - 2 01 2 - G B
11
R E FE R E NCE S
Ackermann, H.-W. & DuBow, M. (1987), Viruses of Prokaryotes.
IDF No. 308 (1995), Introduction to the theoretical and empiri-
Boca Raton, Florida, CRC Press
cal basis of the Danish cheese simulator (DCS)”, Bulletin of the
Atamer et al. (2009), Screening for and characterization of
International Dairy Federation
Lactococcus lactis bacteriophage with high thermal resistance,
Kessler, H. G. (2002), Food and Bio Process Engineering, Dairy
Internattional Dairy Journal
Technology, Verlag A.Kessler
Bradley, D. E. (1967), Ultrastructure of and bacteriocins. Bacte-
Madigan et al. (2000), Brock Biology of Microorganisms, ninth
rial. Rev 31, p. 230-314
edition, published by Library of Congress Cataloging-in-Publica-
Dogan et al., Food Micro (2008), Screening for new heat-re-
tion Data
sistant Lactococcal Bacteriphages in milk systems and determi-
Müller-Merbach (2009), Lactococcus lactis bacteriophages in
nation of the kinetics of inactivation.
milk systems: Thermal-hydrostatic inactivation and proliteration
http://en.wikipedia.org/wiki/Bacteriophage (28th April, 2010)
http://en.wikipedia.org/wiki/Lytic_cycle (28th April, 2010)
by means of propagation and diffusion VDI Verlag.
Spiegel, T. (1999), Thermische Denaturierung und Aggregation von Milkenproteinen in Ultrafiltrationsmilkenkoncentraten
http://www.mansfield.ohio-state.edu/~sabedon/beg_phage_
– Reaktionskinetik und Partikulieren im Schabewämetauscher.
images.htm (28th April, 2010)
Dissertation TU München-Weihenstephan, Freising
ICTV (1982), The universal database of the International Com-
Steffl, A. (1999), Integration von denaturierten Milkenproteinen
mittee on Taxonomy and Viruses: http://www.ncbi.nlm.nih.gov.
in die Matrix von Weichkäse. Dissertation, TU München-Weihen-
ICTVdb/index.htm
stephan Freising
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