Neither olive oil nor vinnegar need to be refrigerated; yet when mixed (as
in home-made salad dressing), the recipes all ask for it to be refrigerated
(where it congeals to a gooey mess).

What is different about olive oil + vinnegar + a few spices & salt from a
microbial culture standpoint?

Why must I refrigerate a mix of that which doesn't itself need to be
refrigerated?

Jeanette Guire wrote:

Neither olive oil nor vinnegar need to be refrigerated; yet when
mixed (as in home-made salad dressing), the recipes all ask
for it to be refrigerated (where it congeals to a gooey mess).

What is different about olive oil + vinnegar + a few spices & salt
from a microbial culture standpoint?

Why must I refrigerate a mix of that which
doesn't itself need to be refrigerated?

Essentially because the mixing will normally end up contaminating
the mixture, if only because the container wont be sterile.

On Oct 14, 10:18 pm, Jeanette Guire
wrote:
Neither olive oil nor vinnegar need to be refrigerated; yet when mixed (as
in home-made salad dressing), the recipes all ask for it to be refrigerated
(where it congeals to a gooey mess).

What is different about olive oil + vinnegar + a few spices & salt from a
microbial culture standpoint?

The bacteria need to be in water to live and the oil provides the food
for them to grow.

--
Ron

Rod Speed wrote:

Why must I refrigerate a mix of that which
doesn't itself need to be refrigerated?

Essentially because the mixing will normally end up contaminating
the mixture, if only because the container wont be sterile.

They technically weren't sterile beforehand either.

Ron Peterson wrote:
On Oct 14, 10:18 pm, Jeanette Guire
wrote:
Neither olive oil nor vinnegar need to be refrigerated; yet when mixed (as
in home-made salad dressing), the recipes all ask for it to be refrigerated
(where it congeals to a gooey mess).

What is different about olive oil + vinnegar + a few spices & salt from a
microbial culture standpoint?

The bacteria need to be in water to live and the oil provides the food
for them to grow.

Bacteria do not need water to survive.
That said, I'd be curious if this is just habit or has anyone actually
done study of whether the mixed oil/vinegar require chilling to keep
bacterial load in check? What other ingredients are added tht might
introduce higher risks?

Goomba38 wrote
Rod Speed wrote

Why must I refrigerate a mix of that which
doesn't itself need to be refrigerated?

Essentially because the mixing will normally end up contaminating
the mixture, if only because the container wont be sterile.

They technically weren't sterile beforehand either.

The containers they came in were near enough.

Rod Speed wrote:
Goomba38 wrote
Rod Speed wrote

Why must I refrigerate a mix of that which
doesn't itself need to be refrigerated?

Essentially because the mixing will normally end up contaminating
the mixture, if only because the container wont be sterile.

They technically weren't sterile beforehand either.

The containers they came in were near enough.

Not nearly...clean is a far cry from "sterile" which is what I was
responding to.

Rod Speed wrote:
Goomba38 wrote
Rod Speed wrote

Why must I refrigerate a mix of that which
doesn't itself need to be refrigerated?

Essentially because the mixing will normally end up contaminating
the mixture, if only because the container wont be sterile.

They technically weren't sterile beforehand either.

The containers they came in were near enough.

Sterility (from a microbiological view)is like virginity it either is or it
isn't no in between.

Goomba38 wrote:
Ron Peterson wrote:
On Oct 14, 10:18 pm, Jeanette Guire
wrote:
Neither olive oil nor vinnegar need to be refrigerated; yet when
mixed (as in home-made salad dressing), the recipes all ask for it
to be refrigerated (where it congeals to a gooey mess).

What is different about olive oil + vinnegar + a few spices & salt
from a microbial culture standpoint?

The bacteria need to be in water to live and the oil provides the
food for them to grow.

Bacteria do not need water to survive.
That said, I'd be curious if this is just habit or has anyone actually
done study of whether the mixed oil/vinegar require chilling to keep
bacterial load in check? What other ingredients are added tht might
introduce higher risks?

Microorganisms such as bacteria and fungi (including yeasts) require a
certain level of "Available Water" to metabolise and grow. Properly made
jams do not have sufficient "Available Water" to permit microbial growth.

Fungi and bacteria can grow (usually anaerobically) at an oil/water
interface an this causes immense problems when water gets in to fuel
storages causing the build up of gunge that can disable jet engines (most
embarrising at 20,000 feet when all engines cut out).

The question is what bacteria are able to grow at the vinegar/oil interface?
My guess would be very few medically important microorganisms if it is good
quality vinegar.

Either make the dressing up in small batches and discard the unused portion
or keep it in the fridge and either zap it in the microwave or warm it up
with warm water before use.

Goomba38 wrote:
Rod Speed wrote:
Goomba38 wrote
Rod Speed wrote

Why must I refrigerate a mix of that which
doesn't itself need to be refrigerated?

Essentially because the mixing will normally end up contaminating
the mixture, if only because the container wont be sterile.

They technically weren't sterile beforehand either.

The containers they came in were near enough.

Not nearly...clean is a far cry from "sterile"

They're pretty close to sterile in practice.

which is what I was responding to.

GreenieLeBrun wrote:
Rod Speed wrote:
Goomba38 wrote
Rod Speed wrote

Why must I refrigerate a mix of that which
doesn't itself need to be refrigerated?

Essentially because the mixing will normally end up contaminating
the mixture, if only because the container wont be sterile.

They technically weren't sterile beforehand either.

The containers they came in were near enough.

Sterility (from a microbiological view)is like virginity it either is
or it isn't no in between.

Wrong with new containers for those components.

GreenieLeBrun wrote:
Goomba38 wrote:
Ron Peterson wrote:
On Oct 14, 10:18 pm, Jeanette Guire
wrote:
Neither olive oil nor vinnegar need to be refrigerated; yet when
mixed (as in home-made salad dressing), the recipes all ask for it
to be refrigerated (where it congeals to a gooey mess).

What is different about olive oil + vinnegar + a few spices & salt
from a microbial culture standpoint?

The bacteria need to be in water to live and the oil provides the
food for them to grow.

Bacteria do not need water to survive.
That said, I'd be curious if this is just habit or has anyone
actually done study of whether the mixed oil/vinegar require
chilling to keep bacterial load in check? What other ingredients are
added tht might introduce higher risks?

Microorganisms such as bacteria and fungi (including yeasts) require a
certain level of "Available Water" to metabolise and grow. Properly
made jams do not have sufficient "Available Water" to permit
microbial growth.
Fungi and bacteria can grow (usually anaerobically) at an oil/water
interface an this causes immense problems when water gets in to fuel
storages causing the build up of gunge that can disable jet engines
(most embarrising at 20,000 feet when all engines cut out).

The problem with that theory is that the dressing sold ready to use already
has that interface and doesnt require refrigeration until its opened.

The question is what bacteria are able to grow at the vinegar/oil
interface? My guess would be very few medically important
microorganisms if it is good quality vinegar.

Either make the dressing up in small batches and discard the unused portion or keep it in the fridge and either zap it
in the microwave or warm it up with warm water before use.

They're pretty close to sterile in practice.

You're not listening. Either a container is sterile - that is, a can,
or a jar with an airtight seal, and has been "processed" at a certain
temperature for a certain number of minutes, or it is not. There is no
such thing as "pretty close in practice."

Dressing and mayonnaise containers in the grocery store are not. They
have cardboard seals, are in no way airtight, and have not been
"processed." They *can't* be processed - you can't heat mayonnaise.

Conversely, if you argue that a plastic jar with a cardboard seal is
sufficient to preserve food, you should put up some fruits and
vegetables that way and check back on them in a couple of weeks.

--
Daniel MacKay
Halifax, Nova Scotia, Canada

Jeanette Guire wrote:

Neither olive oil nor vinnegar need to be refrigerated; yet when mixed (as
in home-made salad dressing), the recipes all ask for it to be refrigerated
(where it congeals to a gooey mess).

What is different about olive oil + vinnegar + a few spices & salt from a
microbial culture standpoint?

Why must I refrigerate a mix of that which doesn't itself need to be
refrigerated?

As I understand it, the garlic and other herbs put in the dressing may
have botulism spores on them, the oil provides the environment for the
botulism to grow. The vinegar doesn't stop the growth because it
separates too easily from the mix.

You may be able to avoid refrigeration if you first infuse the herbs and
garlic in pure vinegar. However I think the likelihood of spoilage is
greater if you do this. (It may not be toxic, but it will taste bad.)

Daniel MacKay wrote:

They're pretty close to sterile in practice.

You're not listening.

You in spades.

Either a container is sterile - that is, a can, or a jar with
an airtight seal, and has been "processed" at a certain
temperature for a certain number of minutes, or it is not.
There is no such thing as "pretty close in practice."

You can keep asserting that till you are blue in the face if you like, changes nothing.

Dressing and mayonnaise containers in the grocery store are not. They
have cardboard seals, are in no way airtight, and have not been "processed."

And they are close enough to sterile for all practical purposes anyway.

They *can't* be processed - you can't heat mayonnaise.

We aint talking about mayonnaise.

Conversely, if you argue that a plastic jar with a cardboard seal

Its got a plastic top as well as the cardboard seal.

is sufficient to preserve food, you should put up some fruits and
vegetables that way and check back on them in a couple of weeks.

Having fun thrashing that straw man are you child ?