UHT Milk spoiled problem

Can anybody help me to find the solution ?

We use direct injection uht systeam and sterilized the milk @145 ^oC with 2 seconds.

While production; there are no problems that we can see in uht system and tetrapak packaging machines and also packages integrity. But after the incubated packages, results are ;

• at the first incubated packages there are no spoilage, everything is OK,
• spoilage packages starts nearly the middle of production till the end of production.
• spoilages; Some of packages "clearly coagulated" some of packages "no coagulation but dropped pH is 5.40-6.00"
• the spoilage packages starts nearly same time with two machines
• a previous production incubated packages results are OK. (same UHT system and same packaging machines)
• a next production incubated packages results are OK. (same UHT system and same packaging machines)
• interestingly some samples which is in trouble time interval, there is nothing change, no spoilage, package is OK.
• We checked the sterilization PLC systeam memory; the desired temperature was maintained during the process.(between 144.9 - 145.8 ^oC)

Production systeam ==> Two machine(TBA/8, 1000cc slim re-cap) installation without aseptic tank.

I am looking for your precious opinions...

Thanks...

Can anybody help me to find the solution ?

We use direct injection uht systeam and sterilized the milk @145 ^oC with 2 seconds.

While production; there are no problems that we can see in uht system and tetrapak packaging machines and also packages integrity. But after the incubated packages, results are ;

• at the first incubated packages there are no spoilage, everything is OK,
• spoilage packages starts nearly the middle of production till the end of production.
• spoilages; Some of packages "clearly coagulated" some of packages "no coagulation but dropped pH is 5.40-6.00"
• the spoilage packages starts nearly same time with two machines
• a previous production incubated packages results are OK. (same UHT system and same packaging machines)
• a next production incubated packages results are OK. (same UHT system and same packaging machines)
• interestingly some samples which is in trouble time interval, there is nothing change, no spoilage, package is OK.
• We checked the sterilization PLC systeam memory; the desired temperature was maintained during the process.(between 144.9 - 145.8 ^oC)

Production systeam ==> Two machine(TBA/8, 1000cc slim re-cap) installation without aseptic tank.

 

I am looking for your precious opinions...

 

Thanks...

Dear jhonrobust,

I know nothing about yr process so my input is limited but I will introduce one or two generic initial queries which may asssist other more technically familiar people.

IMEX, “random” problems within a batch are often difficult to pinpoint.

Exactly what do you mean by “spoilage” ? eg (a) coagulated, (b) incorrect pH, © ???  what kind of percentage defect level / batch, eg 1%, 10%, 50% ?

Is this a system which has previously been operating with no problem for a substantial time or a new project ?

If  the former, the (obvious) typical approach is to look for “modifications” / changes in the process, eg new equipment, raw material, operator (!), process conditions, etc.

If the latter may be this problem is well-known and there is a  common cause for the occurrrence, hopefuly which will be forthcoming from other milk people here.

Rgds / Charles.C

PS - this thread might also be of some interest -

http://www.ifsqn.com...est/#entry66877

Dear jhonrobust,

 

I know nothing about yr process so my input is limited but I will introduce one or two generic initial queries which may asssist other more technically familiar people.

 

IMEX, “random” problems within a batch are often difficult to pinpoint.

 

Exactly what do you mean by “spoilage” ? eg (a) coagulated, (b) incorrect pH, © ???  what kind of percentage defect level / batch, eg 1%, 10%, 50% ?

 

Is this a system which has previously been operating with no problem for a substantial time or a new project ?

If  the former, the (obvious) typical approach is to look for “modifications” / changes in the process, eg new equipment, raw material, operator (!), process conditions, etc.

If the latter may be this problem is well-known and there is a  common cause for the occurrrence, hopefuly which will be forthcoming from other milk people here.

 

Rgds / Charles.C

 

PS - this thread might also be of some interest -

http://www.ifsqn.com...est/#entry66877

Dear Charles.C

First of all Thank for your opinions...

Defect level of batch is greater than 50%, spoilage packages mean; some of packages "clearly coagulated" some of packages "incorrect pH" is between 5.40-6.00".

By the way, we checked packages in ware house, which are the same packaging time with defects, there are nothing occurs and normal pH value, but we took samples these pallets, and incubated @40 ^oC in 2 days. And then we get the as like defects as the beginning incubated packages. So we think about it is thermofilic spores...

Our UHT system has previosuly operating with no problem for a substantial time.

There were some modification in our process, For UHT system; there was a problem for the sterilizer temperature, which is not same with analog and digital(onPLC) temperature values. (we set the low sterilizer temp. 144^oC, the analog temperature is 145^oC, but on PLC digital temperature is 140^oC, so the system stop itself. We changed the heat card of sytem, and the calbirated the temperatures and checked it; now there is no problem for temperatures. (it is about 1 month ago).

For packaging system; for 3 months, we have a problem about gaskets(pipe seals); sometimes when we starting the production, while we are controlling the pipes and its connections at the beginning we see the lekage. So that we stop production, cleaning again. we change the gaskets before production. These gaskets is Tetra Pak recomendation, and tetra pak produce it.

Another important point; Defects are not begin with two machines within the same time, for example they were beginning @09:00(am)

first the defects began @16:00(pm) with machine A packages, and going on... At the machine B first defect began @17:20(pm) and going on... (there isn't any problem before 16:00(pm), no short stop or trouble... etc.)

Process line as like;

UHT system ==> plate ==> Machine A ==> Machine B ==> intermediate product tank ==> UHT system

I am looking for your precious opinions...

best regards, / John

Hi jhonrobust,

Difficult to give you clear directions on a possible cause. However what stands out in your account of the issue is the fact that the defects are from production which occurs later and not following start up. This should be easier to solve than an intermittent issue and more difficult than one affecting all production. At a very simple level it would appear that something is changing at circa 16.00pm which you are not aware of. Could there be a shift change around this time? Is there tank change over? Is there something that could result in a drift in the thermal treatment e.g. boiler?

Also have you conducted any micro analysis to identify which spoilage microorganisms are causing the issue?

George 

Hello John,

 Is your spoilage microbiological  or physical.

(The heat-resistant thermophiles, such as B. stearothermophilus and B. licheniformis. They can cause the ‘flat sour’ defect in UHT milk, which is characterised by acid production, but no gas production, could be an issue with non-gas forming thermoduric  spore-formers.)

"If these microorganisms are producing slight levels of acid but more importantly some levels of proteolysis this could cause sufficient destabilization of the casein micelle such that on heating the product further exposure to the inversely soluble ionic calcium might result in coagulation"

It is very likely that this issue is not directly a result of the process or the packaging. It is most likely to be traced back to the initial milk supply. Some sampling of the milk supply to identify the potential source of the thermoduric spore-formers is the most likely avenue towards finding a resolution to this quality issue.

Good quality raw milk is essential for producing UHT milk with a long shelf life. In general, milk destined for UHT processing should be stored refrigerated (<5◦C) for no more than 24 h. Storage at higher temperatures and/or for longer times promotes the growth of psychrotrophic bacteria, which cause the production of lactic acid, reduction of the pH of the milk and also production of enzymes, notably proteases and lipases that can have considerable heat stability.

When the pH is reduced to ≤6.5, milk becomes unstable to heat. The UHT process destroys all vegetative bacteria and most sporeformers but does not inactivate some of the enzymes produced by psychrotrophic bacteria, such as Pseudomonas species, i.e. the most common bacterial contaminants of raw milk. Such enzymes are typically produced when the bacterial count exceeds106 cfu mL−1. If milk with such bacterial counts is UHT processed, these enzymes, particularly proteinases and lipases, can remain active in the UHT milk. Since UHT milk is usually kept at room temperature and may be stored for several months, even traces of these enzymes can produce noticeable changes, and result in bitter flavour and gelation (due to proteinases) .

Most likely the source of the high resistant spores (HRS) is the raw milk. However, biofilm formation by HRS on heat exchangers, pasteurizers, and gaskets is also very common. 

Visual inspection of the production line for formation of deposits/biofilm should be checked. 

Swabs should be taken from the production line to identify/exclude sources of contamination other than raw milk. 

Bacteriological analysis of milk samples at all production steps especially the intermediate tank /aseptic tank prior to filling.

Milk should be held for at least 10 days after manufacturing. Samples should be stored at 30 and 55 C. During this period, any slight drop in pH (even 0.1 unit) or change in taste will indicate microbial growth.

Sushil,

Great assessment!

Hi

I suggest that  you look at the following points:

1. Quality of steam production

2. Package Integrity test frequency and the reports

3. Milk quality

The exact point of steility break should be identified to solve the problem.  The frequency of the tests may be increased to get a solution.

Hope I am able to give a guidance for solving the problem.  All the best.

Krishnan, R

Goa. India

Hello John,

 Is your spoilage microbiological  or physical.

(The heat-resistant thermophiles, such as B. stearothermophilus and B. licheniformis. They can cause the ‘flat sour’ defect in UHT milk, which is characterised by acid production, but no gas production, could be an issue with non-gas forming thermoduric  spore-formers.)

"If these microorganisms are producing slight levels of acid but more importantly some levels of proteolysis this could cause sufficient destabilization of the casein micelle such that on heating the product further exposure to the inversely soluble ionic calcium might result in coagulation"

It is very likely that this issue is not directly a result of the process or the packaging. It is most likely to be traced back to the initial milk supply. Some sampling of the milk supply to identify the potential source of the thermoduric spore-formers is the most likely avenue towards finding a resolution to this quality issue.

 

Most likely the source of the high resistant spores (HRS) is the raw milk. However, biofilm formation by HRS on heat exchangers, pasteurizers, and gaskets is also very common.

If it was raw milk I would expect to see sporadic sterility failures throughout production.

If it was a film building up during production I would expect to see a gradual increase in insterility not a sudden appearance of insterility.

Regards,

Tony

Dear Charles.C

 

First of all Thank for your opinions...

 

Another important point; Defects are not begin with two machines within the same time, for example they were beginning @09:00(am)

first the defects began @16:00(pm) with machine A packages, and going on... At the machine B first defect began @17:20(pm) and going on... (there isn't any problem before 16:00(pm), no short stop or trouble... etc.)

 

Process line as like;

 

UHT system ==> plate ==> Machine A ==> Machine B ==> intermediate product tank ==> UHT system

 

I am looking for your precious opinions...

 

best regards, / John

Hi John,

I suggest that you refer to Tetra Guidance, I am posting some edited extracts:

I suggest that you investigate by writing a time axis which represents the total production run, starting from sterilisation of the equipment to the end of production. For each individual filling machine occurrences, such as changing the packaging material blanks or reels ® or longitudinal strip (L), stops (St) and re-starts (P), etc., are entered. All the relevant changes in production conditions are included, such as changing from a steriliser to a sterile tank and back, etc. In the list, the incidence of unsterile packages is recorded as well. Often there is a correlation between an event and unsterility that indicates that the event may have caused the problem.

Failure of the UHT process as such is less frequent than high bacterial spore counts in the intermediate product. Reinfection is the most common cause of unsterility and results in a more complex picture. In an UHT-line, the number of possibilities for re-infection of the properly sterilised product is large :
Cooling sections of the heat exchanger
Aseptic pump and homogeniser
Piping/seals
Aseptic filling equipment
Packages or containers
Cleaning and sterilisation of the entire plant
Operational faults
Internal and external handling of packaging
Peroxide strength/temperature
Other

In addition, it is necessary to gather information on the:
Tightness of the packages
Size of the problem
Type of product spoilage
Type of spoilage flora
Distribution of spoiled packages over the production run
History of the problem

When bacteriological problems occur in long life milk, the cause can be either:
The survival of heat-resistant spores or
A secondary contamination (re-infection)

A re-infection with spore-forming and other bacteria is indicated when there are incidents of mixed infections.

Reinfection often results in a mixed flora dominated by vegetative, non-sporeforming microorganisms, mainly Pseudomonas, Streptococcus and Enterobacteriaceae.

However, pure re-infections with spore-forming microorganisms is also possible, particularly as a consequence of inadequate cleaning and equipment sterilisation as well as by leakage in heat exchangers and other equipment operating at a temperature above ~ 80°C.

The most often isolated species from microbiologically spoiled products are Bacillus stearothermophilus, B. licheniformis, B. subtilis, B. cereus, B. badius and B. polymyxa.

Indicator Organism/Effective Killing Temperature/Process Survivors/Reinfection Source
Bacillus > 100° C Process Survivors Intermediate Product, Equipment, Packaging Material
Actinomyces > 90 C Both Air, Dust
Lactobacillus > 80 C Reinfection Milk, Aerosols, Human
Streptococcus > 80° C Reinfection Milk, Aerosols, Human
Micrococcus > 80° C Reinfection Milk, Aerosols, Human
Enterobact. > 75° C always Reinfection Milk, Human
Pseudomonas > 65 C always Reinfection Water, Milk, Aerosol

Bacillus does not multiply in high-acid products. In low acid products, typically they are proteolytic causing a bitter flavour and a soft coagulum. In milk, gas is produced only rarely. A slight drop in pH (down to ~ 6.0) is encountered. Lactobacillus, Streptococcus and Enterobacteriaceae attack carbohydrates rapidly, forming acid and often gas. The pH usually drops well below 5. In milk, Actinomyces, Micrococcus and Pseudomonas cause limited product changes only. Pseudomonas may temporarily even raise the pH (to ~7.0) and develop a fruity, fishy off-flavour due to the formation of short chain fatty acid esters such as ethylbutyrae and ethylhexanoate.

When the first part of production is sterile followed by a sudden or a slow increase in unsterility, operative errors or machine faults may cause such a pattern. The change to a new batch of intermediate product should also be considered as a possible cause. A change of packaging material in combination with a lack of personal hygiene, as well as other sporadic failures, can
explain such a pattern.

Also consider what intermediate cleans have been carried out.

Regards,

Tony

Hi my dear friends,

Unfortunately we couldn't find that spoilage microbiological  or physical. We took the samples which are produced by the same time of defects and incubated @30^oC for five days. After incubation, we opened some samples and testing pH-Organoleptic analysis etc... Results are; pH: 6.73(@20^oC), normal odor and no coagulation. we inoculated other samples (which are incubated) in PCA @30^oC for 3 days, results were negative.

Production starts with intermediate tank-8 (Ph: 6,70) @22:50(pm),

we passed through the tanks;

• Tank-10 (Ph:6,70) @00:40(am), ==> Tank-17 (Ph:6,73) @07:55(am), ==> Tank-13 (Ph:6,70) @09:40(am),

We controlled all the steps;

• Cooling sections of the tubular heat exchanger, we gave the 4 bar air through the tubes and we checked the pressure drops, but after 12 hours there is %0,5 dropping, we think that it is normal.
• we checked sterile milk pump and homogeniser there isn't anything unusual.
• we checked again and again the package integrity,
• we checked, there aren't any operational faults...
• the other steps...

We are confused about this problem, please help us... :secret:

I am looking for your precious opinions...

Thanks...

Hi John,

Did you investigate by writing a time axis which represents the total production run, starting from sterilisation of the equipment to the end of production with all the events and failures marked?

Did you try incubating samples at 55 ^oC to test for thermophilic bacteria?

Regards,

Tony

Hi,

We investigated total process from the sterilization equipment to the end of production, we couldn't find any failure.

Today, we got the some results; Yesterday; when we incubated some packages(which are the same time with defects) at 30 degrees 3 days, we found the spoilage package which is semi coagulated, then we took sample for microbiolgy analysis. We get colony and after gram staining, we get result as Gram Positive, catalase positive. we think that it is corynebacterium isn't it ?

I couldn't paste the microscop view because system didn't allowed it.

I am looking for your precious opinions...

Thanks...

Thanks.

Hi John,

You haven't given enough information to identify, this should help:

Identification of Gram Positive Bacteria.pdf   380.51KB   120 downloads

Once you have identification you should be sampling and swabbing to try and identify the source.

Regards,

Tony

Hi John,

 

You haven't given enough information to identify, this should help:

 

Identification of Gram Positive Bacteria.pdf

 

Once you have identification you should be sampling and swabbing to try and identify the source.

 

Regards,

 

Tony

Hi Tony,

We checked again the analysis and we determined the bacteria; it is lactobacillus

regards.

Jhon

Hi Tony,

 

We checked again the analysis and we determined the bacteria; it is lactobacillus

 

regards.

 

Jhon

Hi John,

Now you have identification you should be sampling and swabbing to try and identify the source.

Lactobacillus are not normally heat resistant but still, check the loading on your raw milk before use plus your storage conditions and any rework being added. Also do you produce yoghurt?

You should also follow the investigation plan as per my previous post

Regards,

Tony

Consider backflow,surges and eddies.

Hai Jhonrobust, 

As i read your case, you have machine TB 8/1000 cc, it same with our machine.

would you like to guide me, i don't have experience about this.

can you share abaout sampling plan, how to check for packaging integrity and test in Laboratory ?

please to response

Thanks

Faradilla