Công nghệ sản xuất sữa tươi tiệt trùng Cô gái Hà Lan

It may contain Consumer Milk Products non fermented, Cultured Consumer Milk Products, Lactic Acid Drinks, yoghurt, drinking yoghurt, Butter and Butter oil, Cheese, Sterilised Evaporated

Dairy technology

A TRAINING ABOUT THE PRODUCTION

AT FRIESLANDCAMPINA VIETNAM

IN HA NAM

COMMISSIONED BY FRIESLANDCAMPINA

.

Dairy technology

A TRAINING ABOUT THE PRODUCTION

AT FRIESLAND CAMPINA VIETNAM

IN HA NAM

COMMISSIONED BY FRIESLAND CAMPINA

.test

For over 20 years now this training is performed to employees of Friesland Foods It started in the early

‘90's of the last century with a training to workers in Leeuwarden, producing evaporated milk and sweetened condensed milk Gradually, more and more staff became interested, and not only of the supply point Leeuwarden, but of different factories too Of course, its contents are modified since and adapted to new demands, new scientific insights and new target groups, taking the training.

In 2004 I was asked to write a dairy course for the factories outside the Netherlands with the same structure as the courses mentioned before

The first and second part of the course, i.e Milk science (1), Microbiology (2), Checks on raw milk (3), Statistics of filling (4) and Cleaning and Disinfecting (5), Overview (6), Heat (7), Separating the cream (8), Standardisation (9), Homogenisation (10), information about the production of milk powders (11) and Recombination (12) are applicable for most production sites

The third and final part depends on the local production and will be adapted for each factory It may contain Consumer Milk Products (non fermented), Cultured Consumer Milk Products, Lactic Acid Drinks, yoghurt, drinking yoghurt, Butter and Butter oil, Cheese, Sterilised Evaporated Milk and Sweetened Condensed Milk, Milk Powders and compositions, Whey Products, Fruit Juices and Fruit Drinks, Filling and Packing, Quality Control and Quality Requirements

These courses intend to give background information The how question can easily be answered at the production site These courses intend to answer the why question: why do we act like we act during

processing I realize that it may be quite a challenge for you to absorb this course But I really hope that, afterwards, you will say: it was quite a lot of work but it was worth doing it Because: now I really

understand.

Leeuwarden, September ‘08

Fons Michielsen

Ha Nam, Vietnam

.

2.6 measures to control microorganisms in dairy products 171

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7.8 heat management271

9.3 standardising market milk for fat and total solids 319

9.4 standardising on the ratio fat : milk solids non fat 321

9.5 standardising on the ratio fat : milk solids non fat : sugar 323

Ha Nam, Vietnam

20.2 composition of retentate and permeate 623

20.3 construction of cross flow membrane equipment 627

20.6 three examples of cross flow filtration 645

-VI-Ha Nam, Vietnam 14 Pumps and valves

Illustration 14.1 Centrifugal pump

14 PUMPS AND VALVES

Long time ago fluids were transported in wooden buckets or in hog’s bladders One cannotimagine to produce in a dairy factory without piping Among other things we need pumps andvalves for this transport

14.1 Pumps

Although there are many different types of pumps it is possible to classify them The task ofpumps is to transport gasses or liquids by means of pressure (difference)

Rotodynamic pumps

Rotodynamic pumps give fluids a high speed in a certain direction by means of a fan with

blades or screw To explain the word rotodynamic one can imagine to swing around a bucket

of water (vertical) The water in the bucket gets a certain speed and a certain direction Whenyou would stop suddenly swinging around the water may leave the bucket as a result of itsinertia The speed and direction of the water after leaving the bucket determine how high the

water will come This can be compared with the head of the discharge of a pump The amount

of water that can be transported by the pump is referred to as its capacity The capacity isexpressed as litres or m3 per minute or per hour

The same is true for rotodynamic pumps When the diameter of the discharge pipe is reduced,the capacity will be reduced as well, but the head of the discharge increases A different way

to express head of the discharge is the discharge pressure

Two types of rotodynamic pumps can be distinguished: axial flow pumps and centrifugalpumps In a centrifugal pump the liquid is swinged to the outside of the pump case by means

Ha Nam, Vietnam 14 Pumps and valves

Illustration 14.2 Axial flow pump

Illustration 14.3 Some types of centrifugal pumps

of the fan in a spiral casing; an axial flow pump pushes the liquid through a pressure pipe Seeillustration 14.1 and 14.2

The advantages of a rotodynamic pump are the simple construction (driving shaft direct

mounted to rotor), so little maintenance Besides, it is easy to adjust the capacity with a controlvalve on the discharge pipe and they can be build for large capacities And they are cheap But, they also have disadvantages Only low viscous liquids can be pumped, the dischargepressure is very limited and usually the pump is not self priming

Starting from the initial design a lot of adaptations have been made to meet special

requirements For extra pressure a multi stage centrifugal pump is available and for fluids withparticles a pump with withdrawn impeller has been developed The latter is also suitable to usefor high viscous liquids without damaging the viscosity too much See illustration 14.3

Pump suppliers have many types of pumps and even pumps that look similar to us have

different properties Clients are interested in the capacity of a pump under certain

circumstances Specially capacity related to the counter pressure or discharge pressure isimportant to understand or predict the performance of a pump For this suppliers have socalled service data Illustration 14.4 shows service data of some pumps from Tetra Pak

Ha Nam, Vietnam 14 Pumps and valves

Illustration 14.6 Smoothening thedischarge pressure

Illustration 14.5 Principle of a reciprocal pump

Positive (displacements) pumps

Positive pumps or volumetric pumps push liquids (and gasses) from one place to another.They “take” some liquid from a suction pipe and push it into the pressure pipe We distinguishreciprocating pumps and rotary positive pumps

A reciprocating pump is like a syringe or a (manual) bicycle pump A certain amount of liquid

or gas is push out of a cylinder by means of a piston or plunger As soon as the piston orplunger returns to its original position again some liquid is sucked into the pump housing.Because of the reciprocating movement these pumps are known as reciprocating pumps Theadvantages are that very high pressure can be achieved and they can be used for very accuratedosage Besides they are self priming The disadvantages are that they are very expensive,

liquids should not contain particles, they may destroy equipment and they don’t have highcapacities These pumps have a cylinder with a push rod and a piston

Illustration 14.4 Service data of some pumps of Tetra Pak

Ha Nam, Vietnam 14 Pumps and valves

Illustration 14.7 Dual acting disc pump

Illustration 14.8 Two lobe pumps

Illustration 14.9 Worm-type pump

When the push rod has the same diameter as the cylinder, we call this a plunger See

illustration 14.5 Piston pumps can deliver high pressures, plunger pumps can deliver very high pressures, up to 500 or 1000 bar.To reduce pulsating pressure at the pressure side of thepiping several plungers or pistons are placed parallel This is called a multistage plunger orpiston pomp See illustration 14.5 and 14.6

A well known reciprocal pump in the dairy

industry is the homogeniser This is a plunger

pump combined with a very narrow gap, in

which oil droplets or milk fat globules are

reduced in size See illustration 10.21 and

10.23

A very special type of reciprocal pump is the

dual acting disc pump or diaphragm pump

The pump has a reciprocating push rod

connected to two pistons, covered by a

membrane The delivery pressure is lower

than that of a piston or plunger pump, but it is

suitable to transport aggressive liquids See

illustration 14.7

Two examples of rotating positivepumps are the lobe pump or the gearpump and the worm-type pump Lobepumps and gear pumps are similar, justthe number of lobs differ See

illustration 14.8 The worm-type pomp

is different: it has a rubber sealinghousing and a steel rotor Thedimensions of the rotor slightly differfrom the dimensions of the housing So

by rotating there always is some spaceleft somewhere between the housingand the rotor See illustration 14.9

Advantages of rotating positive pumps are that fairly high pressures can be achieved, fairlyviscous fluids can be transported and fluids with solid particles can be transported as well andthey are cheaper that piston or plunger pumps and they hardly damage viscosities

Disadvantages are that wear and slip may occur, transmission is rather complex and capacitiesare limited

Lobe pumps usually are taken to transport

yoghurt When the counter pressure in the

delivery pipe increases, for instance

because of stretching of the yoghurt, these

pumps may slip Slip being defined as the

portion of the pumped product that is

forced back to the suction side of the

pump due to pressure through the

clearances

Ha Nam, Vietnam 14 Pumps and valves

Whether or not slip occurs depends on the

counter pressure, the viscosity and on the

fits and clearances of the lobes and

housing See illustration 14.10

14.2 Valves

It is important to understand how valves

act to know how fluids are running

through the piping

Many types of valves are used in the food

industry They can be classified in

different ways There are manually controlled valves and valves that are controlled with anactuator Apart form that there are shut off valves or stop valves, shuttle valves or multi wayvalves and control valves; there are different designs too: butterfly valves, ball valves, anglevalves and many types of multi way valves

There are many suppliers ofvalves and they all have theirown characteristics But ingeneral the principles aresimilar When you know thecross section you may be able

to see from outside whether avalve is opened or closed Andwhat “opened” or “closed”means

Illustration 14.11 shows abutterfly valve One is manual

controlled, one is with actuator The type of

actuator is discussed below A butterfly valve is

a shut off valve: it is open or it is closed It is a

simple construction but it can start to leak For

the seal of this valve is not very secure At the

place where the seal touches the axis of the

shutter it will be damaged by frequent use

(friction) A second disadvantage of this valve is

that the shutter itself takes quite some space in

the cross section of the pipe, so the flow is

retarded

Illustration 14.10 Slip in a rotary pump

Illustration 14.11 Butterfly valves, left manual controlled,

right with actuator

Illustration 14.12 A ball valve

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Illustration 14.13 Joucomatic

Ball valves are also very popular because of the simple construction and they have the fullvalve area for the flow The only disadvantage is that food residues can stay behind in the falsespace between ball and housing (see illustration 14.12) However, there are suppliers thatclaim to have sanitary ball valves Also a ball valve is a shut off valve and the type shown ismanual controlled

Let us focus on actuators Illustration14.13 shows a Joucomatic valve Mostvalves operate one way with compressedair and the other way with a spring, e.g.open with compressed air and closed with

a spring We say: the valve is monostable,because the valve will always return tothe same position (in this example:

closed) when not controlled In otherwords: if no compressed air is suppliedthe valve will always be closed (in thisexample) The reason to choose formonostable valves is security: if the aircompressor fails, no accidents shouldhappen For that reason valves areconstructed in such a way that they arealways safe When a valve is mounted in

a steam pipe it probably is an air-to-open valve or, in other words, normally closed If the compressed air supply fails, steam supply will

stop and prevent equipment from over heating A valve in a cooling circuit will probably be

air-to-close: if the air compression fails the valve will open to prevent the cooling circuit to

fail Let us have a look at the valve in illustration 14.13

The valve opens when the shutter goes down It is not necessary like this, but it is true in thisillustration The fluid may come from the right or from the left Usually suppliers advise toclose the shutter counter current For this illustration this would mean that the liquid comesfrom the left This is done to prevent water hammer Close counter current is not easy: thismeans that the last part of the operation goes very slowly The flow is slowed down nicely andthe liquid will come to a standstill gently

Closing the shutter in the direction of the flow is very easy The shutter will close very fastand cause a shock in the piping when the fluid comes to a sudden standstill This shock is notgood for the equipment and gives an unpleasant sound in the factory

Illustration 14.13 shows a valve with the compressed air connection on top Immediatelybeneath this a membrane is mounted that will go down when compressed air is supplied Thered coloured spring assembly is impressed and the (blue) shutter stem with shutter goes down.The shutter is released from the shutter seat and the valve is opened

This valve opens with compressed air and closes by means of a spring It is an air-to-open

valve At the outside you can see the spring An impressed spring means an opened valve

Ha Nam, Vietnam 14 Pumps and valves

Illustration 14.14 Angle valve, air-to-open

Illustration 14.17 Shuttle valve,

air-to-open

A different type of valve with the same type of actuator is the angle valve, see illustration

14.14 Also here it is possible to have the actuator air-to-open or air-to-close Illustration 14.14 shows a cross section of an air-to-open or normally closed valve The air connection is

beneath the spring, so without air the spring will push the shutter down and close the valve

But a spring is not necessary

An actuator can also be fitted

with two air connections If the

compressed air supply is

reliable there is no need to use

a spring The application of

springs is partly because of

safety, partly because of

tradition Illustration 14.15

shows a double air actuator

From outside it is easy to see whether the valve isopen or closed, because a piece of the shutter stemcan be seen on top of this valve The most rightvalve in illustration 14.14 is closed, because the stemhardly protrudes from the actuator This angle valve

is a shut off valve

Except these shut off valves there are so calledshuttle valves There are a lot of embodiments, see

illustration 14.16 Image a shows an angle valve, the

others are shuttle valves, all with actuators

Illustration 14.17 shows image c of illustration 14.16

in detail It can not be seen from these images, butthe design nowadays is very hygienic

Illustration 14.15 Angle valve,applied with double air actuator

Illustration 14.16 Overview from different bodies a is anangle valve, the others are shuttle valves

Ha Nam, Vietnam 14 Pumps and valves

Blind angles can easily occur in valves and product residues and microorganisms may

accumulate This is unwanted and it should be taken into account during the design that thisdoesn’t occur, both in the complete line as well as in the individual components Most valves(and pumps and other components) applied in the food industry meet the directions of theEuropean Hygienic Engineering & Design Group (EHEDG)

A special application of shuttle valves isthe valve with leak detection Often it isnecessary to have the opportunity toconnect different flow systems, so shuttlevalves are applied However, it should beassured that no two product flows orproduct and cleaning solution can mix.See illustration 14.18 So to assure this a

so called leak detection valve isdeveloped

Imagine the situation in illustration 14.19 In the upper body flows milk, in the lower bodycleaning solution Both are only divided by one single shutter Leakage is likely to occur onthe long run

To be sure that no mixing of fluids can occur a chamber has been constructed within the

shutter itself Any liquid passing to this chamber will be drained instead of entering the otherfluid This type of valve is called a valve with leak detection or a mix proof valve

This chamber and this drain are of

course blind angles and they have to be

cleaned as well So this type of valve is

rather complicated During cleaning of

the upper body (the line connected to

the upper body) the upper part of the

shutter will be lifted separately,

allowing the cleaning solution to clean

chamber and drain

During cleaning of the (line connected

to the) lower body the lower part of the

shutter will be lowered separately thus

allowing the chamber and drain to be

cleaned See illustration 14.20

To control not only the complete shutter, but also the upper part and the lower part separately (2) more air connections are required to the actuator and a more complicated construction ofthe actuator, as can be seen in illustration 14.20

Illustration 14.18 A manifold with different flows

Illustration 14.19 Shuttle valve without (A) andwith (B) leak detection

Ha Nam, Vietnam 14 Pumps and valves

A second special application of shuttlevalves is the so called aseptic valve Seeillustration 14.21 It replaces a

combination of valves to create a steamlock, to guarantee an aseptic seal in anaseptic line (for instance between aSterideal and a aseptic tank or between

an aseptic tank and a filler) This shuttlevalve has a shutter that acts as a sterilebarrier, since it is filled with saturatedsteam or condensate, creating a sterileseparation of two or three product lines.There are special facilities to ensureproper cleaning of the valve seatsurfaces

Recently suppliers deliver valves with an extra electronic indicator on top of the valve (shutoff valves and multi way valves) to indicate the shutter position See illustration 14.22

Control valves

The valves so far mentioned are intended to shut off a flow or to direct flows But sometimes it

is required to control a flow, to control the quantity of liquid that passes a pipe This can bedone with control valves When a control valve is completely opened, we say that the shutterposition is 100 %, and when the valve is completely closed, we say that the shutter position is

0 % It is good to understand that a control valve never shuts off, but it will always allow someflow to pass at a shutter position of 0 % If it is really necessary to shut off a flow a secondshut off valve (e.g a butterfly valve) is necessary

Illustration 14.21 Aseptic valve

Illustration 14.20 Several positions of the shutter in a mix proof valve

Ha Nam, Vietnam 14 Pumps and valves

Illustration 14.24 Indicatorfor shutter position

Clearly to see is the

deviating shape of the

shutter, compared with

previous valves The shutter

in this type of valve has a

somehow conical shape

The more the shutter is

pushed into the shutter

opening, the more narrow

the gap This type of valves

control best at a shutter

position of 50 %

When a very accurate tuning is required in the process a valve capacity should be chosen that,

at a shutter position of 50 %, allows the regular flow At a shutter position of almost 100 % oralmost 0 % this type of valve cannot control the flow very accurate

As mentioned before, also this type of valve is mounted in a line in such a way, that the fluidcomes from the right (illustration 14.22); the valve closes counter current and this will prevent

water hammer The valve in illustration 14.23 is air-to-close, or normally open An indicator

indicates the shutter position Illustration 14.24shows this magnified

Sometimes the flow of the liquid pushes theshutter more open then desired: the set point ofthe shutter position is not met For this reason acontrol valve may be equipped with a so calledshutter position adjustment: a small electronicdevice on the valve itself; with a sensor it recordsthe real shutter position and it adjusts the shutter to the appropriate position This finetuning isdone by means of a little bit more or less compressed air on the (membrane of the) valve Seeillustration 14.25

14.3 Questions

1 What type of pumps are commonly used in the dairy industry? Explain why

2 Mention a apparatus where a reciprocating pump is used

3 What type of pump is required to transport yoghurt? Why?

4 What do we mean with a service data diagram of a pump?

5 Why may a positive pump be dangerous?

6 Mention three types of shut off valves

Illustration 14.22 Shutter indicator

Illustration 14.23 Control valve

Ha Nam, Vietnam 14 Pumps and valves

Illustration 14.25 Control valve withshutter position adjustment

7 What is an air-to-close valve?What is said to be the disadvantage/risk of an double air

actuator?

8 What is water hammer and how to prevent this?

9 How can be seen from outside whether a shut off valve is opened or closed?

10 What is the use of a shuttle valve?

11 What is the use of a mix proof valve?

12 Explain the principle of an aseptic shuttle valve

13 A flow should be controlled on 6000 l/h on average What should be the maximum

capacity of the control valve? Why?

14 What is the use of an shutter position adjustment? And what type of valve may be

equipped with this device?

Ha Nam, Vietnam 14 Pumps and valves

15 THE PRODUCTION OF YOGHURT

minimum durability If the product is heat treated after fermentation the requirement for viable microorganisms does not apply.

With respect to the cultures, the following is added for yoghurt:

Symbiotic cultures of Streptococcus thermophilus and Lactobacillus delbrueckii subsp.

Table 15.1 Requirements imposed on yoghurt

Further, the Codex specifies that the production of yoghurt must meet the general hygiene rules

as defined in the General Principles of Food Hygiene (CAC/RCP 1-1969, REV 4-2003)

Yoghurt originates from the Balkans and Turkey,

where yoghurt was (and is) produced from buffalo and

donkey milk, but mainly from sheep milk The great

propagandist for yoghurt in western Europe was

professor Elie Metchnikoff (1845 - 1915, illustration

15.1) of the Pasteur institute in Paris (France) He

considered yoghurt to be an effective defence against

infections and intoxications According to this Russian

scientist, the good health and longevity of the Turks

and Bulgarians was due to the regular use of yoghurt

Metchnikoff, who predicted that his discovery would

allow him to live to the age of 100, died of a heart

condition at the age of seventy one

The first yoghurt was imported into the Netherlands around 1920 by a journalist, De Kruyff,who worked in Turkey for his newspaper When he returned to the Netherlands, he

Illustration 15.1 Metchnikoff in hislaboratory in Paris

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brought a few so-called yoghurt cultures These were actually lumps of lactic acid bacteriacolonies This is how the product was introduced in the Netherlands.

Much has changed in the production of yoghurt since it spread across the globe from the

Balkans Nowadays, when yoghurt is made from fresh milk, it is usually done according to thediagram in illustration 15.3 Let us first look at some other topics

15.2 Types of yoghurt

In terms of fermentation temperature, manufacturers have three types of yoghurt: stirred

yoghurt (to be discussed), set yoghurt and short yoghurt Only the first and the second arewidespread and well known around producers In addition, consumers know Bulgarian

yoghurt, fruit and drinking yoghurt and yoghurt with health claims

A short explanation for each of these terms

- From the manufacturers point of view

In short, stirred yoghurt is produced at a fermentation temperature of 31EC during 16 - 20

h The milk is inoculated with 0.12 % fresh starter culture After fermentation the yoghurt

is stirred in a tank, packed and cooled This will be discussed in detail Stirred yoghurt hasonly been known since the fifties Before then, people always made set yoghurt

In the production of set yoghurt, the yoghurt milk is inoculated with 2.5% culture, the milk

is filled into bottles or beakers and the bottles are incubated for 2.5-3 hours at 45EC Inthat short time, the pH drops to below 4.50 The resulting yoghurt has a different viscosity:

no slime has been created, or not to the extent that it tangibly contributes to the viscosity,and the protein coagulum is firmer Usually a gel which breaks into lumps if stirred Theproduct is thicker and lumpier and "stands" in the package: it is difficult to get it out of thepackage One great advantage in the production of set yoghurt is that there is a greaterchoice of cultures than in the production of stirred yoghurt, so set yoghurt and derivativescan be very aromatic

- From the consumers point of view

Bulgarian yoghurt is usually a set yoghurt with an increased total solids content For

example, the requirement for Bulgarian yoghurt is that the fat content is at least 4.40% andthe milk-solids-non-fat content at least 12.6%

In some countries, limitations have been defined for yoghurt with fruit For example, in the

Netherlands, this should consist of at least 70.0% yoghurt and at least 7.0% fruit or fruitpulp Further permitted additives are: sugar (in various forms), a thickening or emulsifyingagent, citric acid, flavours and colouring agents A precise description of the additives isgiven in the Codex

Yoghurt with fruit juice should contain at least 70.0% yoghurt and at least 4.0% fruit juice.

Further additives are the same as yoghurt with fruit

Ha Nam, Vietnam 15 Yoghurt

Sometimes, fruit yoghurt is yoghurt with fruit produced according to the stirred yoghurtprocess The method is as follows: stirred yoghurt is made and once it cools, the yoghurtflows into a mixing chamber just ahead of the filling equipment Here, the yoghurt ismixed in-flow with a precisely measured flow of fruit or fruit pulp and possibly otheradditives In other cases, fruit yoghurt is made using the set yoghurt process: the

inoculated yoghurt milk is filled into beakers that already contain the fruit portion Thebeakers are incubated at 45EC, but the preservatives that may be present in the fruit or fruitpulp can slow the fermentation down somewhat These preservatives may have beenadded by the manufacturer of the fruit (pulp) or be naturally present in the fruit (benzoate

in elderberries and bilberries) In this production method, the fruit sinks to the bottom ofthe package On the other hand, the product - in the case of a one-person package - canhave an attractive appearance: an easy to spoon and somewhat firm consistency that doesnot exhibit structural deficiencies such as lumpiness or inhomogeneity during the shorttime between breaking the coagulum and consumption

Technically speaking, drinking yoghurt is yoghurt with fruit juice that in some cases has

been made long-life by heating The yoghurt (in the case of stirred yoghurt) or yoghurtmilk (in the case of set yoghurt) is mixed with fruit juice to create a homogeneous mass.The yoghurt (milk) is then mixed with sugar and pectin (possibly incubated if set yoghurt

is used), homogenised (200 atm), pasteurised, cooled and filled The result is a thin liquidacidic milk drink As a result of the homogenisation, the casein becomes so unstable thatflakes and whey separation soon occur The addition of a special highly esterified pectin(+ 0,5%) prevents whey separation and creates a stable product

Yoghurts with health claims have to be divided in yoghurts with prebiotics and with

probiotics Prebiotics are additions of non digestible fibres to ordinary yoghurt They

stimulate the action of intestinal flora An examples is FOS (Fructo-Oligo-Saccharides).Among other products they can be found in chicory root and banana

Probiotics are live microbial, dietary supplements or food ingredients that have a

beneficial effect on the host by influencing the composition and or metabolic activity ofthe flora of the gastrointestinal tract Commonly they hardly grow in milk and they hardlyproduce yoghurt So usually not probiotic yoghurt is produced, but yoghurt with addition

of a probiotic culture Bacteria with probiotic properties can be found in the genus

Lactobacillus (L casei and L acidophilus), Propionibacteriaceae and Bifidobacterium (B.bifidum and B longum)

It is good to know that yoghurt thanks its gels structure respectively viscosity to a caseinnetwork resulting from a low pH and - in the case of stirred yoghurt - the effect of extracellularpolysaccharides (EPS) The basic taste and aroma are also the result of the activity of lacticacid bacteria

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