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things that go bad

post #1 of 9
Thread Starter 
Cake, cookies, pie, when made at home everything is fresh no powdered or preservatives added unlike sold in stores. Does this stuff you make at home really go bad? I never had a bach of cookies or boxed cake turn. I have bought a pumpkin pie from a stand in PA grow hair after a week left on the counter, very sad their pies are awsome. Does keeping in the fridge extend there life much or just destroy them
post #2 of 9

the growth of microbes is dependent on many factors, one of them is temperature.

 

you should understand the danger zone.  Below is probably the most accurate and complete picture of microorganism growth in food pertaining to food safety.

ref:http://www.foodsafetymagazine.com/magazine-archive1/februarymarch-2004/the-danger-zone-reevaluated/

 

Refrigeration does not kill microorganisms but slows them down considerably.  This concept is called bacteriostatic

https://en.wikipedia.org/wiki/Bacteriostatic_agent

 

To answer your question: refrigeration extends the shelflife of the product.

 

PS. We keep homemade baked deserts on the counter under a glass bell.  They rarely last more than 4-5 days but one time my wife undercooked a banana bread.  The kids love it because it was very moist inside when they took a piece that same day. After 3 days, I took a piece and I thought it tasted bland (unsweet). When I placed the cake under the bell I had a whiff of winey, boozy fermentation come out.  It was fermenting.

 

Luc H.

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post #3 of 9

I LOVE THE SCIENCE!!!! Thank you once again @Luc_H ......this is AWESOME!!! :bounce:

post #4 of 9
Quote:
Originally Posted by Fablesable View Post
 

I LOVE THE SCIENCE!!!! Thank you once again @Luc_H ......this is AWESOME!!! :bounce:

 

Me too!

Nursing school ruined me when it comes to beasties that you cannot see...

At one point we swabbed our hands after washing with soap and then again after using sanitizer.....still grew out a surprising number of things...eek!

 

@Luc_H could you explain the bacteria to toxin process?

I read quite a few posts that suggest just bringing to a boil for X amt of minutes will kill every nastie in the pot.

 

mimi

post #5 of 9
Quote:
Originally Posted by flipflopgirl View Post
 

@Luc_H could you explain the bacteria to toxin process?

I read quite a few posts that suggest just bringing to a boil for X amt of minutes will kill every nastie in the pot.

Sorry for the late reply... I was travelling.

 

@flipflopgirl your question is not easily answered because of several concepts your wording has evoked.

 

here is some nomenclature:

Bacteria, yeast, molds are microorganisms (M-O).  M-Os fall in several categories in microbiology but fall in specific categories when it comes to food safety:

Useful M-Os: are the ones responsible for fermentation

 

Inoffensive M-Os: live on food and skin but convey neither function, odour, taste, smell or disease

 

Nuisance M-Os: changes the appearance, smell or taste of food but do not cause a disease (i.e. mold on bread for example). Some Useful M-O are considered nuisance if it is not intentional.

 

Pathogen M-Os: cause human disease when ingested.  There are 2 ways to cause disease, by growing in our GI tract (ex: e. coli) or by producing a toxin (ex botulinum toxin produced by Clostridium Botulinum causing botulism).

 

why I started my explanation this way is because you can kill pathogens very easily: no pathogen can survive above 75C (165F) for 3 seconds. Death and growth of M-Os are dependant on the temperature-time combination i.e. to kill pathogens you can do it at a lower temperature as long as you maintain a longer period of time. (see example below)

http://www.hi-tm.com/PDG/Retail-VI.html

 

Salmonella is the toughest vegetative pathogen to kill.  So instead of 74C (165F) for 3 sec you get the same result at 55C (130F) for 121 min.  (By the way, this table is a guide for safe sous vide cooking)

 

While these temperatures can kill all pathogens no amount of cooking can destroy toxins.

 

More nomenclature:

Pasteurization means to kill 99.9% of pathogens not all the M-Os. This means milk is pasteurized but can still go bad even if the container is never opened but the nuisance M-Os will not make you sick however.

 

Vegetative M-Os means M-Os that are little sacs of water that live and multiply.  Some M-Os make spores, like a tough nut, they cannot be killed with boiling water. It requires sterilization.

 

Sterilization means to kill 99.999% of all M-Os (it's a numbers game).  Canned foods are sterilized to kill spores like from Clostridium Botulinum.  This can only be done at temps above boiling which can only be done by applying high pressure: 120C+ (248F+) (requiring 15 PSI) for 10 min+ which depends on the size of the container.

http://www.hippressurecooking.com/pressure-canning-faq-put-em-up/

 

This post is long enough now (I'm leaving out details)...

Suffice to say that your question is not easily answered.

 

Luc H. (edited for typos)


Edited by Luc_H - 7/27/15 at 6:13am
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post #6 of 9
Fascinating stuff...
Micro was one of my fave science (nursing school) courses but had sooo much trouble keeping things straight.
Barely squeaked by...
Really do appreciate the time you take to break stuff down into digestible pieces (sorry could not help it lol).

mimi
post #7 of 9
Well... Temperature and time certainly are factors. Also consider
-the substrate. Proteins or carbs are more dangerous
-moisture content
-starting population (pasteurization was invented for a reason after all)
-acidity
-salt
-other microorganisms competing for resource. This is why ferments are room temp stable. Kimchi, sauerkraut etc have such high population of bacteria to start nothing dangerous can grow

Actually salt is all that is used in ferments to stop bad things long enough for lactic acid bacteria and yeast to take over

One thing people overlooks lot is cooked rice or pasta. Recipe for disaster there. Moist, warm, lots of carbs, no salt or acid, nothing already fermenting. Jackpot!
post #8 of 9

Brilliant breakdown @Luc_H....thank you!

 

I realize there is a lot more to things than one can simply put into a few sentences however, you always seem to be able to make it easy to digest.....(@flipflopgirl ....hehe thanks for that tidbit.....yup meant to be punny) :D 

post #9 of 9
Quote:
Originally Posted by flipflopgirl View Post
 

@Luc_H could you explain the bacteria to toxin process?

I read quite a few posts that suggest just bringing to a boil for X amt of minutes will kill every nastie in the pot.

since the question was about time and temp, I stayed within that limit.

 

Quote:
Originally Posted by MillionsKnives View Post

Well... Temperature and time certainly are factors. Also consider
-the substrate. Proteins or carbs are more dangerous
-moisture content
-starting population (pasteurization was invented for a reason after all)
-acidity
-salt
-other microorganisms competing for resource. This is why ferments are room temp stable. Kimchi, sauerkraut etc have such high population of bacteria to start nothing dangerous can grow

Actually salt is all that is used in ferments to stop bad things long enough for lactic acid bacteria and yeast to take over

One thing people overlooks lot is cooked rice or pasta. Recipe for disaster there. Moist, warm, lots of carbs, no salt or acid, nothing already fermenting. Jackpot!

mostly correct on all counts but I considered those comments off topic hence my comment below

 

Quote:

This post is long enough now (I'm leaving out details)...

 

Luc H. (edited for typos)

 

Cooking can only kill pathogens in foods but does not prevent them from growing back however 1 of these 2 factors can prevent the growth of any pathogens in foods regardless of their protein or carb content.

 

no pathogen can grow in a pH below 4.6 ex: yoghurt, buttermilk, lemonade, cola, ceviche, ...

http://www.ext.vt.edu/topics/food-health/food-innovations/basics/

 

no pathogens can grow if the water activity is below 0,85. ex. beef jerky, honey, corn syrup, maple syrup, capicollo, peanut butter, milk powder, etc...

water activity (Aw) is defined by how available water is to microbes.  Salt and sugar locks up water by osmosis. Pure water has a Aw of 1 and bone dry has a Aw of 0.  An Aw of 0.85 means 15% of the water is locked up.

(see reference above for definition)

 

foods with both factors are safer still: ex. cured sausages, mayonnaise

 

Luc H.


Edited by Luc_H - 7/27/15 at 6:52am
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