24 replies to this topic

[hygienic]

I have a question came to my mind, if I have a food and this food is cooked thoroughly to a level that grantee that bacteria killed ,then this food is kept in the danger zone for a time that make the food spoiled , the question here if the Bacteria already killed , how its reform and germinate again in the food ,meaning how it came to food again ? from where?  

Is it like a cell from the food itself which can be more cells? 

 

I Know and all know that because of the time and temperature bacteria has grown but the question from where its initiated (Origin) . 

 

If you have a scientific answer, please share it 

 

Regards

 

[SHQuality]

Bacteria are all over our environment: on surface, on dust in the air and pretty much anywhere else you can think of.

Unless you protect the cooked food by hermetically sealing it away from outside influence, it is recontaminated pretty much instantly.

 

(There are some heat-resistant bacteria that can survive regular heating and you need to account for organisms and mycotoxins that can't be killed.)

[hygienic]

Bacteria are all over our environment: on surface, on dust in the air and pretty much anywhere else you can think of.
Unless you protect the cooked food by hermetically sealing it away from outside influence, it is recontaminated pretty much instantly.
 
(There are some heat-resistant bacteria that can survive regular heating and you need to account for organisms and mycotoxins that can't be killed.)

I do agree with you .but I mean in my question the life cycle of bacteria is a role in how it can be formed in a food ? Consider a dish of salad which the plate been washed and sanitized and all other things involved in making the salad been washed and sanitised and then you kept the dish covered at ambient tempreture for long time .how bacteria started to form and germinated in the plate ? What is the mechanism for it to grow?

[kfromNE]

I have a question came to my mind, if I have a food and this food is cooked thoroughly to a level that grantee that bacteria killed ,then this food is kept in the danger zone for a time that make the food spoiled , the question here if the Bacteria already killed , how its reform and germinate again in the food ,meaning how it came to food again ? from where?  

Is it like a cell from the food itself which can be more cells? 

 

I Know and all know that because of the time and temperature bacteria has grown but the question from where its initiated (Origin) . 

 

If you have a scientific answer, please share it 

 

Regards

Spores. That's why certain foods need to be pasteurized. Yeast and mold too. They are very heat and cold resistant.

[Sayed M Naim Khalid]

Check the following places for bacteria: 

1. Air (mainly your facility ventilation system)
2. Food Contact surface
3. Contaminated packages/dish or whatever is used to hold food
4. Contaminated water
5. Contaminated utensils
6. Contaminated equipment

You can experiment two things to see if it works: 

1. Remove air by vacuuming the package. 
2. Use preservative to extend shelf life. 

[SHQuality]

how bacteria started to form and germinated in the plate ? What is the mechanism for it to grow?

Bacterial growth only starts when the plate is contaminated. If the entire thing is sterile, it's impossible for bacteria to grow.

Bacterial cells can't form without prior bacterial cells duplicating.

[hygienic]

Bacterial growth only starts when the plate is contaminated. If the entire thing is sterile, it's impossible for bacteria to grow.

Bacterial cells can't form without prior bacterial cells duplicating.

I thought bacteria naturally in food as a cell without dividing , so when there is a favourable circumstances (Time,tempreture,moisture for bacteria .cells start to form and multiply.

[SHQuality]

I thought bacteria naturally in food as a cell without dividing , so when there is a favourable circumstances (Time,tempreture,moisture for bacteria .cells start to form and multiply.

 

Food usually isn't sterile, so when you put food in favorable conditions, the bacteria that are already present will divide, but they won't "form" out of nothing.

[hygienic]

Food usually isn't sterile, so when you put food in favorable conditions, the bacteria that are already present will divide, but they won't "form" out of nothing.

That's nice debate thanks alot .Food you tested in lab against example Salmonella and result was not detected. After that you store it improperly this food later contaminated with Salmonella, that means even not detected in the test but its in a lag stage this is what I can deduced.

[Charles.C]

I have a question came to my mind, if I have a food and this food is cooked thoroughly to a level that grantee that bacteria killed ,then this food is kept in the danger zone for a time that make the food spoiled , the question here if the Bacteria already killed , how its reform and germinate again in the food ,meaning how it came to food again ? from where?  

Is it like a cell from the food itself which can be more cells? 

 

I Know and all know that because of the time and temperature bacteria has grown but the question from where its initiated (Origin) . 

 

If you have a scientific answer, please share it 

 

Regards

Hi hygienic,

 

You probably also need to do a little reading as to the difference between Pasteurisation and Sterilisation.

[hygienic]

Hi hygienic,
 
You probably also need to do a little reading as to the difference between Pasteurisation and Sterilisation.

Thanks Charles .it's well known already .my question is just to understand the exact life cycle of bacteria in a scientific way

[Kara S.]

I have a question came to my mind, if I have a food and this food is cooked thoroughly to a level that grantee that bacteria killed ,then this food is kept in the danger zone for a time that make the food spoiled , the question here if the Bacteria already killed , how its reform and germinate again in the food ,meaning how it came to food again ? from where?  

Is it like a cell from the food itself which can be more cells? 

 

I Know and all know that because of the time and temperature bacteria has grown but the question from where its initiated (Origin) . 

 

If you have a scientific answer, please share it 

 

Regards

 

 

 

Check the following places for bacteria: 

1. Air (mainly your facility ventilation system)
2. Food Contact surface
3. Contaminated packages/dish or whatever is used to hold food
4. Contaminated water
5. Contaminated utensils
6. Contaminated equipment

You can experiment two things to see if it works: 

1. Remove air by vacuuming the package. 
2. Use preservative to extend shelf life. 

 

 

Great question! This was just the type of question I would ask when I first got into science. 

 

I wanted build upon Sayed's response since that touches upon all contributing factors. 

 

There are many types of bacteria that live and survive in different conditions (temperature, oxygen, water levels, pH, and so on). Bacteria grows in a logarithmic pattern. https://easysciencef...le-of-bacteria/

• A lag phase - where the bacteria is living dormant
• A growth phase - where bacteria is placed in an optimal environment and starts rapidly multiplying
• A stationary phase - where bacteria has used up most of the nutrients in the environment and the growth/death rates are about equal
• Death phase - where the bacteria uses up all the nutrients and can no longer multiply "grow" they start to die off, and some go into dormant stages.

When we cook/ treat product, we are not removing all bacteria from it. We are just reducing its presence by log reductions. This is a good resource for understanding life-cycle and log reductions https://foodtechsimp...lue-simplified/. So when you cook something, it has killed off most bacteria, but the food is also food for bacteria. Also in industry, we are looking for treatments against pathogens, not every bacteria known to man. Spoilage organisms may be floating in the air, air provides oxygen for growth, there is humidity (water) in air, and water (aw) in the food you just cooked. You mentioned leaving it at room temperature, so all of these factors are favorable for bacterial growth. Even when we remove oxygen, we have to consider bacteria that can grow in low oxygen environments like C.botulism.

 

Unless you are working in a ESL/ commercially sterile processes like others in this thread have mentioned. That process kills more bacteria and provides a modified storage environment that doesn't allow anything to grow. It maintains conditions to keep any bacteria that may have survived cannot grow. That is why when you get these types of shelf stable beverages, sauces, vacuum packed meats, they say to refrigerate after opening because the environment is no longer controlled. 

[Ryan M.]

Just because you cook something does not mean it is sterilized, or the food is sterile.  In most cases it is not sterile.  Really, the few processes for sterilizing food include retort (canning) or ultra-high temperature processing.  To sterilize mean you destroy all bacteria including spore forming bacteria.  Most heating methods do not eliminate spores, and additionally only give a 3 to 6 log reduction.

 

Additionally, most packaging is not a complete barrier against outside bacteria, meaning hermetically sealed.  So you have leftover bacteria in the food and you have bacteria that can migrate in and out of the package.

[liberator]

That's nice debate thanks alot .Food you tested in lab against example Salmonella and result was not detected. After that you store it improperly this food later contaminated with Salmonella, that means even not detected in the test but its in a lag stage this is what I can deduced.

For your example of salmonella the result of "Not Detected" does not mean it's not there in the food. That's why we should never say absent for a microbial result as we cannot with 100% confidence say it's absent, or not present. Not detected means we didn't find it, not that it's not there. Providing your manufacturing process is robust and verified (regular heat processing, pasteurisation/drying etc) it's quite possible there is no salmonella in the product, but we cannot say it's absent, just we didn't detect it (You'd hope it is actually not there though cause that's a bigger issue.)

 

If we were to increase the sample size and the number of samples we test we could find it. When you sample a product you have say 1 kg, you take 10gs from that main sample, but no salmonella was in that 10g sample, but you take another 10g sample it could be there in that sample. we're talking about microorganisms where thousands of cells can fit on a pin head, it's like looking for a needle in a haystack.

[hygienic]

For your example of salmonella the result of "Not Detected" does not mean it's not there in the food. That's why we should never say absent for a microbial result as we cannot with 100% confidence say it's absent, or not present. Not detected means we didn't find it, not that it's not there. Providing your manufacturing process is robust and verified (regular heat processing, pasteurisation/drying etc) it's quite possible there is no salmonella in the product, but we cannot say it's absent, just we didn't detect it (You'd hope it is actually not there though cause that's a bigger issue.)
 
If we were to increase the sample size and the number of samples we test we could find it. When you sample a product you have say 1 kg, you take 10gs from that main sample, but no salmonella was in that 10g sample, but you take another 10g sample it could be there in that sample. we're talking about microorganisms where thousands of cells can fit on a pin head, it's like looking for a needle in a haystack.

I am totally agree with you .its a good explanation to distinguish between absence and not detected. After read some articles posted here .bacteria in phase 1(Lag phase) here it's there but not growing. Since it's not growing so can't be detected through the lab analysis.

[hygienic]

Great question! This was just the type of question I would ask when I first got into science. 

 
I wanted build upon Sayed's response since that touches upon all contributing factors. 
 
There are many types of bacteria that live and survive in different conditions (temperature, oxygen, water levels, pH, and so on). Bacteria grows in a logarithmic pattern. https://easysciencef...le-of-bacteria/

• A lag phase - where the bacteria is living dormant
• A growth phase - where bacteria is placed in an optimal environment and starts rapidly multiplying
• A stationary phase - where bacteria has used up most of the nutrients in the environment and the growth/death rates are about equal
• Death phase - where the bacteria uses up all the nutrients and can no longer multiply "grow" they start to die off, and some go into dormant stages.

When we cook/ treat product, we are not removing all bacteria from it. We are just reducing its presence by log reductions. This is a good resource for understanding life-cycle and log reductions https://foodtechsimp...lue-simplified/. So when you cook something, it has killed off most bacteria, but the food is also food for bacteria. Also in industry, we are looking for treatments against pathogens, not every bacteria known to man. Spoilage organisms may be floating in the air, air provides oxygen for growth, there is humidity (water) in air, and water (aw) in the food you just cooked. You mentioned leaving it at room temperature, so all of these factors are favorable for bacterial growth. Even when we remove oxygen, we have to consider bacteria that can grow in low oxygen environments like C.botulism.
 
Unless you are working in a ESL/ commercially sterile processes like others in this thread have mentioned. That process kills more bacteria and provides a modified storage environment that doesn't allow anything to grow. It maintains conditions to keep any bacteria that may have survived cannot grow. That is why when you get these types of shelf stable beverages, sauces, vacuum packed meats, they say to refrigerate after opening because the environment is no longer controlled.

Got it Kara ,many thanks, well explained.

[Gelato Quality Lead]

One thing that has not been mentioned yet is that some methods of reducing bacteria may lead to some colonies only being injured, therefore not detected. 

 

If the bacteria is injured, under the right conditions, it can recover and cause spoilage or illness.

[hygienic]

One thing that has not been mentioned yet is that some methods of reducing bacteria may lead to some colonies only being injured, therefore not detected. 

 

If the bacteria is injured, under the right conditions, it can recover and cause spoilage or illness.

I think you would like to say , Freezing ,preservation ,Irradiation all of these methods are injuring bacteria only .

[Charles.C]

Thanks Charles .it's well known already .my question is just to understand the exact life cycle of bacteria in a scientific way

With all due respect, the first line of your OP immediately proved otherwise.

 

And this, regardless of contamination, answered yr OP.

 

To put it another way, do you understand the difference between "cooked thoroughly" and canning ?

 

And similarly for typical chemical sanitisers.

 

The "long" answer was subsequently given by Kara although not including some, almost perfect, shelf-stable, exceptions..

[hygienic]

With all due respect, the first line of your OP immediately proved otherwise.

 
And this, regardless of contamination, answered yr OP.
 
To put it another way, do you understand the difference between "cooked thoroughly" and canning ?
 
And similarly for typical chemical sanitisers.
 
The "long" answer was subsequently given by Kara although not including some, almost perfect, shelf-stable, exceptions..

Yes agreed , it seemed that I don't have even the basic information, but it has been understood later by fellows here who gave good answer .
As of cooking its destroy the pathogens but in canning process all spores ,toxins,and microorganisms are being destroyed.But note also canning also not enough to keep the product for one year expiration unless preservation added and this is in many canned food .

[Charles.C]

Yes agreed , it seemed that I don't have even the basic information, but it has been understood later by fellows here who gave good answer .
As of cooking its destroy the pathogens but in canning process all spores ,toxins,and microorganisms are being destroyed.But note also canning also not enough to keep the product for one year expiration unless preservation added and this is in many canned food .

Hi hygienic,

 

Re-^^^(red). Sorry but afaik, this is simply incorrect, both theoretically and in practice.

 

Can try this link -

 

https://www.goodhous...nned-food-last/

[EagleEye]

Hi hygienic,

 

The world of bacterial is too dynamic to comprehend with certain general rules how it acts and reacts. It is highly unpredictable how it will act and react even a single change in any parameter we are that affects it.

 

To your specific scenario, knowing bacteria is ubiquitous and many of them we believe out there but not able to manifest into a colony or in any kind of forms by which we can understand it, (Some understandings we have through metagenomics data analysis and assumptions). Your food could have retained spores, even though your degree of guarantee that temperature has "killed" bacteria as per your assumption, not be true. As mentioned above, bacterial cell repair from a damaged cell is highly possible. Spores or viable cells suspended in surrounding air could have enter the food after your cooking is another possibility. 

 

There are hundreds of possibilities to have bacteria generate inside your food owing even to the minute events that happen surrounding to the system where your food stands.

 

It's complicated!

[hygienic]

Hi hygienic,
 
Re-^^^(red). Sorry but afaik, this is simply incorrect, both theoretically and in practice.
 
Can try this link -
 
https://www.goodhous...nned-food-last/

I just simply read the ingredients in canned foods labels , it's include a preservor regardless the type of food. I believe that the process will render the food stable for years.

[hygienic]

Hi hygienic,
 
The world of bacterial is too dynamic to comprehend with certain general rules how it acts and reacts. It is highly unpredictable how it will act and react even a single change in any parameter we are that affects it.
 
To your specific scenario, knowing bacteria is ubiquitous and many of them we believe out there but not able to manifest into a colony or in any kind of forms by which we can understand it, (Some understandings we have through metagenomics data analysis and assumptions). Your food could have retained spores, even though your degree of guarantee that temperature has "killed" bacteria as per your assumption, not be true. As mentioned above, bacterial cell repair from a damaged cell is highly possible. Spores or viable cells suspended in surrounding air could have enter the food after your cooking is another possibility. 
 
There are hundreds of possibilities to have bacteria generate inside your food owing even to the minute events that happen surrounding to the system where your food stands.
 
It's complicated!

It's a very logical illustrations, thanks alot , and that will ask our self direct questions if we open a food can or a sterilised food it has to be consumed within three days for example that mean its possible for bacteria to regenerate and form .

[Charles.C]

Hi hygienic,

 

The world of bacterial is too dynamic to comprehend with certain general rules how it acts and reacts. It is highly unpredictable how it will act and react even a single change in any parameter we are that affects it.

 

To your specific scenario, knowing bacteria is ubiquitous and many of them we believe out there but not able to manifest into a colony or in any kind of forms by which we can understand it, (Some understandings we have through metagenomics data analysis and assumptions). Your food could have retained spores, even though your degree of guarantee that temperature has "killed" bacteria as per your assumption, not be true. As mentioned above, bacterial cell repair from a damaged cell is highly possible. Spores or viable cells suspended in surrounding air could have enter the food after your cooking is another possibility. 

 

There are hundreds of possibilities to have bacteria generate inside your food owing even to the minute events that happen surrounding to the system where your food stands.

 

It's complicated!

Hi Eagle Eye,

 

As you say, Ecology, microbiological or otherwise, is complicated.

 

It appears that the OP was visualizing a simple, open, cooking procedure, eg pasteurization, for which microbial residuals/regenerations/contaminations  are all possible subsequent occurrences. The Safety aspect, allied with long shelf lives/acceptable "Quality",  was a driving force to implementing thermal processes capable of preventing the previously  mentioned possibilities.

Unfortunately, non-Safety related "Quality" aspects can sometimes be a negative side-effect of achieving microbial Safety, eg sterilized foods may taste inferior to pasteurized for some people, eg IMEX, milk.