Here is a discussion of nutrient loss in cooking from "Cookwise" by Shirley
Corriier, P 353-356.
--------------------------------------------
The unexpected stability of nutrients

You would expect different cooking methods to result in different losses of
nutrients, and there are differences -- more of with vitamins than with
minerals -- but not as much as you might think. The following table shows
the variation of losses in minerals and several vitamins for selected raw
vegetables and cooking methods. (chart omitted) The mineral loss is
relatively small (5 to 10 percent) no matter how the vegetable is cooked.
On the other hand, the loss in vitamins varies somewhat, but many vegetables
lose only 20 percent or less no matter what the cooking method. This is not
to say, however, that there isn't great variability in the nutrient content,
because there are very large differences in nutrient content before cooking
(see page 322).

Minimizing nutrient loss in cooking

Vegetables lose nutrients in cooking primarily in two ways: water soluble
compounds (like minerals, vitamin C, and some of the B vitamins) dissolve in
the cooking water, and heat destroys or makes unavailable certain nutrients
(vitamin C and thiamin). The simplest way to avoid loss of water-soluble
nutrients is to not cook the vegetables in water or to cook it in such a
manner that the cooking liquid remains part of the dish, as it does in a
casserole. You can cook vegetables whole in the skin and avoid a little
nutrient loss. When you consider that you can lose as much as 50 percent of
the vitamin C in some produce in 24 hours simply by not keeping it
refrigerated, losses during cooking takes on a new perspective.

Some of these cooking losses can be minimized. To preserve vitamin C in
boiling, it is very important that the cooking water be a boil before the
vegetable in added. In warm water, the enzymes in vegetables become very
active before the water gets hot enough to kill them. Some of these enzymes
cause great destruction (up to 20 percent loss) of vitamin C in the first 2
minutes of cooking. Having the water boiling before you add the vegetable
can prevent this vitamin C loss.

These is also loss of more water-soluble vitamins when you cut up vegetable
because there is more surface from which vitamins can dissolve into the
water. At the same time, however, you reduce cooking time, which saves
vitamins.

Some cooking methods --cooking vegetable in a closed container with a
minimum of water--will slightly improve the water-soluble vitamin content,
but green vegetables will be an unappetizing olive drab, and those for the
genus Brassica will be very strong tasting. It doesn't matter how many
vitamins you preserve if you can't get anyone to that them! I think a
realistic approach is needed in this area. Don't strain a gnat and swallow
a fly.

Cooking has little effect on the nutritive value of carotenoids. Even with
the color change form one structure to another, the nutrient value does not
change. Most of the carotenoids in yellow or orange vegetables are
precursors of vitamin A. This in not true, however, for red vegetable that
get their color from carotenoids.

Carotenoids do deteriorate with lengthy exposure to oxygen. Dried carrot
chips, for example lose their beta-carotene if packaged in air but not if
nitrogen packaged.

Cooking and bioavailabilty of nutrients

You have seen that the comparative nutritional profile of fruits and
vegetables is complex even before cooking. One grapefruit can have 20 time
more vitamin A than another ( page 323). Spinach and lose 50 percent of its
vitamin C in 24 hours if it is not refrigerated.

The effects of cooking on fruits and vegetables are not less complex.
Cooking can remove some toxins and harmful compounds from foods. As
discussed later (page 365), cooking removes cyanide compounds from lima
beans and others. Cooking destroys enzymes in soybeans and other beans that
inhibit our digestion of proteins (page 365). Cooking also converts some
nutrients that are present in foods in unusable forms to forms that the body
can absorb.

Corn is the classic example of cooking to make essential nutrients in a food
available for use in the body. Corn contains lysine, one of the essential
amino acids, but in a form that our bodies cannot use. Cooking corn with a
strong alkali converts the lysine to a form that is bioavailable. This
makes corn a food that can be the staple or primary food of a culture.

The Indians of South and Central America have know this for centuries. How
on earth did these early tribes know to cook corn with an alkali -- ashes or
burned shells or bits of limestone -- to make it more nutritious? They
probably didn't.

What they may have learned accidentally was that cooking corn with an alkali
softened and puffed the kernels and made the corn much easier to grind.
Food preference researcher Dr. Paul Rozin tells of asking South American
Indian women in remote villages why they cooked the corn with ashes? They
explained that it will not grind right and you cannot make tortillas from
the meal if you don't do it that way.

Early cultures that learned to raise corn but did not learn to cook it with
alkali suffered severe dietary deficiency diseases such as pellagra.

Cooking methods

No matter how fruits and vegetables are heated, the same dramatic events
occur --cell walls shrink, cells lose fluid, firm pectin substances between
cells converts to pectin and dissolve, and the cells fall apart.

As we have seen in he preceding sections, this destruction of the cells
brings about changes in texture, color, taste, and nutrients regardless of
the cooking method. Although the differences produced by various cooking
methods are much smaller with plant foods than with meats, there are
practical reasons for choosing one method over another in many situations.

Boiling, blanching, and poaching

Cooking fruits or vegetables in water does remove some of the water-soluble
vitamins; however, as already mentioned, this loss can be minimized by
having the water boiling before plunging the vegetables in. This
immediately kills enzymes that are destructive to vitamins.

Cooking in water does not produce the crust or sweet surface compounds that
you get from plunging foods into hot fats. It does offer controlled
temperature since the water, and therefore the fruit or vegetables can never
get over 212F. However that is not a great advantage. Even with the water
well below a simmer you get all the results of the death of the
cells--changes in color, texture and taste.

You do have control over some of these changes with the cooking time. For
example, you can keep green vegetables green by not cooking them longer than
7 minutes, keep Brassicas sweet and pleasant tasting by not cooking them for
more than 5 minutes, and enhance the taste of onions and carrots with longer
cooking.

When cooking in water, you also have the ability to minimize or control how
much flavor is extracted from a food. For example, if you want to extract
flavor, as in stock making or sauce making, you can put the food into cold
water, bring the temperature up slowly, and simmer for a long time. If you
have ever tasted the onions or celery left after straining stock, you know
they are almost devoid of flavor.

On the other hand, it you want the flavor to remain in the the fruit or
vegetable, you should bring the liquid to a boil, then add the produce and
cook for a limited time. In most of the recipes in this chapter I wanted to
reserve flavor in the fruit or vegetable.

"Vox Humana" > wrote in message
...
> Here is a discussion of nutrient loss in cooking from "Cookwise" by
Shirley
> Corriier, P 353-356.
> --------------------------------------------
> The unexpected stability of nutrients
>
>>
>
> When cooking in water, you also have the ability to minimize or control
how
> much flavor is extracted from a food. For example, if you want to extract
> flavor, as in stock making or sauce making, you can put the food into cold
> water, bring the temperature up slowly, and simmer for a long time. If
you
> have ever tasted the onions or celery left after straining stock, you know
> they are almost devoid of flavor.
>
>

Yes, I have noticed that when making soup stock. I have tried a carrot that
gave up its life to chicken broth and they don't taste very good. The broth
however is excellent! Someday this cold season, I will have time to make
some chicken broth, too!

Dawn

"DawnK" > wrote in message
...
>
> "Vox Humana" > wrote in message
> ...
> > Here is a discussion of nutrient loss in cooking from "Cookwise" by
> Shirley
> > Corriier, P 353-356.
> > --------------------------------------------
> > The unexpected stability of nutrients
> >
> >>
> >
> > When cooking in water, you also have the ability to minimize or control
> how
> > much flavor is extracted from a food. For example, if you want to
extract
> > flavor, as in stock making or sauce making, you can put the food into
cold
> > water, bring the temperature up slowly, and simmer for a long time. If
> you
> > have ever tasted the onions or celery left after straining stock, you
know
> > they are almost devoid of flavor.
> >
> >
>
> Yes, I have noticed that when making soup stock. I have tried a carrot
that
> gave up its life to chicken broth and they don't taste very good. The
broth
> however is excellent! Someday this cold season, I will have time to make
> some chicken broth, too!
>

Nothing goes to waste here. I feed the stock making ingredients to the dogs
instead of throwing it out. Bones and all go into the food processor and
they get the resulting paste on their food.

vox,

Thank you so much for being so 'rude' as to inject science into the
previous discussion on 'waterless' cooking.

Colin





Vox Humana wrote:
> Here is a discussion of nutrient loss in cooking from "Cookwise" by Shirley
> Corriier, P 353-356.
> --------------------------------------------
> The unexpected stability of nutrients
>
> You would expect different cooking methods to result in different losses of



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