Re: Hey Wait a Minute! - bacteria/freezing

[Guest guest]

Hi MFJ,

Freezing does not kill bacteria. Freezing only slows down the

bacteria. When they warm up they start growing again, if conditions

are hospitable.

F. Jewett wrote:

So there's all sorts of neat bacteria and enzymes and things in raw

milk,

that's why we drink it, right? But ... doesn't freezing the milk kill

them, so some/all of those benefits are lost?

MFJ

The Unscientific One

[Guest guest]

Short answer. It probably doesn't have much affect.

The longer answer. Most bacteria can withstand freezing, nearly all stop reproducing, some change into forms that withstand the cold. Since it takes very few surviving individuals to proliferate and repopulate under favorable conditions, for the most part they are still there when thawed. Enzymes are a little more of a problem. Researchers spend a lot of resources looking at freezing (which is a handy way of preserving things). They are striving to preserve without altering or loosing the properties they care about. Hardest thing to preserve is viability, but keeping proteins and other biologically important molecules (which includes enzymes) in such a way that they behave the same after freezing and thawing is still difficult. They utilize additive chemicals that "protect" during freezing, they control the rate of freezing (usually extremely fast), keep the solution circulating so all of the solution cools uniformly, and other techniques. Interestingly, since many are trying to preserve different biological properties, they don't all use exactly the same techniques. Then they pay a lot of attention to how the material is thawed.

If the reason for freezing and then thawing is to preserve longer, and the goal is to maintain as much nutritional value and original taste, I suspect that all that technology is not relevant. But trying to drop the temperature, throughout the entire container, as rapidly as possible will probably minimize the changes. Keep the container small, allow rapid cooling by using containers that transmit heat easily, and place the containers as close to the cooling coils in the freezer as possible. And remember that when dairy solutions freeze, they expand with a lot of pressure.

Ted

Hey Wait a Minute! - bacteria/freezing

So there's all sorts of neat bacteria and enzymes and things in raw milk,that's why we drink it, right? But ... doesn't freezing the milk killthem, so some/all of those benefits are lost?MFJThe Unscientific OnePLEASE BE KIND AND TRIM YOUR POSTS WHEN REPLYING!

[Guest guest]

So if I get raw milk and freeze it, is there a proper way to unthaw

it? Will it last just as long in the fridge as milk that had never

been frozen and taste the same?

Robin

[Guest guest]

At 09:47 AM 2/8/04 -0600, you wrote:

>Hi MFJ,

>Freezing does not kill bacteria. Freezing only slows down the bacteria.

When they warm up they start growing again, if conditions are hospitable.

>

Cool. The thought occurred to me when I was putting my defrosted milk

into the fridge. I know if *I* had spent a week at zero degrees, I'd be

kaputsky. Brrrrrrrrrr.

MFJ

It's finally happened. I'm slightly mad. Oh dear. ~Queen

[Guest guest]

At 12:06 PM 2/8/04 -0500, you wrote:

>Short answer. It probably doesn't have much affect.

Again, cool. (no pun intended, either time hehe)

>If the reason for freezing and then thawing is to preserve longer, and the

goal is to maintain as much nutritional value and original taste, I suspect

that all that technology is not relevant. But trying to drop the

temperature, throughout the entire container, as rapidly as possible will

probably minimize the changes. Keep the container small, allow rapid

cooling by using containers that transmit heat easily, and place the

containers as close to the cooling coils in the freezer as possible. And

remember that when dairy solutions freeze, they expand with a lot of pressure.

I get my milk deliveries once every two weeks, so I freeze half of it for

use the second week, in plastic half-gallon containers. Re: expansion -

every once in while I'll open the freezer to grab one and have it fall out,

endangering my poor tootsies, because of the expansion on the bottom making

it not exactly ... stable.

MFJ

It's finally happened. I'm slightly mad. Oh dear. ~Queen