Re: Which veggies cooked?
- From: "David Saum" <dsaumNOSPAMPLEASE@xxxxxxxxxxxx>
- Date: Tue, 29 May 2007 21:58:38 GMT
<aargrey@xxxxxxxxx> wrote in message
news:1180473130.026564.197390@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I' boil my collards and broccoli for about 5 minutes each, because I
thought I remembered googling somewhere that I need cook them to get
the most of their nutrition. Most vegetables I like better raw.
Can anyone point to a good resource for which vegetables are important
to cook, besides obvious things like corn and potatoes?
Eat cabbage raw and cook broccoli for 10 minutes at 140F:
Cancer Epidemiol Biomarkers Prev. 2004 Jan;13(1):125-31.
Hydrolysis of glucosinolates to isothiocyanates after ingestion of raw or
microwaved cabbage by human volunteers.
Rouzaud G,Young SA,Duncan AJ.
Macaulay Institute, Craigiebuckler, Aberdeen, Scotland, United Kingdom.
Cabbage contains the glucosinolate sinigrin, which is hydrolyzed by
myrosinase to allyl isothiocyanate. Isothiocyanates are thought to inhibit
the development of cancer cells by a number of mechanisms. The effect of
cooking cabbage on isothiocyanate production from glucosinolates during and
after their ingestion was examined in human subjects. Each of 12 healthy
human volunteers consumed three meals, at 48-h intervals, containing either
raw cabbage, cooked cabbage, or mustard according to a cross-over design. At
each meal, watercress juice, which is rich in phenethyl isothiocyanate, was
also consumed to allow individual and temporal variation in postabsorptive
isothiocyanate recovery to be measured. Volunteers recorded the time and
volume of each urination for 24 h after each meal. Samples of each urination
were analyzed for N-acetyl cysteine conjugates of isothiocyanates as a
measure of entry of isothiocyanates into the peripheral circulation.
Excretion of isothiocyanates was rapid and substantial after ingestion of
mustard, a source of preformed allyl isothiocyanate. After raw cabbage
consumption, allyl isothiocyanate was again rapidly excreted, although to a
lesser extent than when mustard was consumed. On the cooked cabbage
treatment, excretion of allyl isothiocyanate was considerably less than for
raw cabbage, and the excretion was delayed. The results indicate that
isothiocyanate production is more extensive after consumption of raw
vegetables but that isothiocyanates still arise, albeit to a lesser degree,
when cooked vegetables are consumed. The lag in excretion on the cooked
cabbage treatment suggests that the colon microflora catalyze glucosinolate
hydrolysis in this case.
PMID: 14744743 [PubMed - indexed for MEDLINE]
-----------
http://www.aces.uiuc.edu/Discover/discover11.cfm
Maximizing the Anti-Cancer Power of Broccoli
University of Illinois researcher Elizabeth Jeffery has learned how to
maximize the cancer-fighting power of broccoli. It involves heating broccoli
just enough to eliminate a sulfur-grabbing protein, but not enough to stop
the plant from releasing an important cancer-fighting compound called
sulforaphane.
The discovery of this sulfur-grabbing protein in the Jeffery lab makes it
possible to maximize the amount of the anticarcinogen sulforaphane in
broccoli.
Jeffery's research will be published in an upcoming issue of Phytochemistry.
She is a professor in the Department of Food Science and Human Nutrition at
the U of I.
"As scientists, we learned that sulforaphane is maximized when broccoli has
been heated 10 minutes at 140 degrees Fahrenheit," said Jeffery. "For the
consumer, who cannot readily hold the temperature as low as 140 degrees,
that means the best way to prepare broccoli is to steam it lightly about 3
or 4 minutes--until the broccoli is tough-tender."
Frozen-food manufacturers may use this technology to increase the health
benefits of the broccoli they sell, allowing the consumer to heat it without
having to worry about the conditions.
Jeffery said that sulforaphane is one of the most powerful anticarcinogens
found in food. "It works by increasing the enzymes in your liver that
destroy the cancer-inducing chemicals you ingest in food or encounter in the
environment."
But the chemistry for triggering the release of sulforaphane is tricky.
Sulforaphane is linked to a sugar molecule through a sulfur bond. When the
broccoli enzyme breaks off the sugar to release the sulforaphane, a
sulfur-grabbing protein can remove the newly exposed sulfur on the
sulforaphane and inactivate it.
"Although our gut bacteria may be able to release some of the sulforaphane,
we don't have the enzyme to release sulforaphane in our body tissues, so our
best bet is to use the enzyme in the broccoli," Jeffery said. "The enzyme in
the broccoli does a really good job of breaking that bond. You can break it
simply by chopping the broccoli."
Jeffery's team of researchers began by cooking broccoli for different
lengths of times at different temperatures to learn the point at which the
broccoli enzyme that releases sulforaphane is destroyed.
"And, much to our excitement, after we had heated it for just a little
while, we found we had killed off a protein that nobody knew was there. This
protein, named the epithiospecifier protein, had been grabbing sulfur and
greatly depleting the amount of sulforaphane in a serving of broccoli.
"The protein was very heat-sensitive, and with a little bit of heat, we
killed it off and got an almost perfect yield of sulforaphane, the
cancer-fighting component," she said.
"It was a serendipitous discovery, and it changed our focus. Instead of
worrying about overcooking the broccoli and losing the enzyme that releases
the sulforaphane, we focused on heating the broccoli just enough to destroy
the sulfur-grabbing protein, but not enough to harm the enzyme that releases
sulforaphane from the sugar," said Jeffery.
Other researchers at the University of Illinois who contributed to the study
were Nathan Matusheski and Qinyan Qiao.
http://www.fshn.uiuc.edu/dept/person.cfm?id=90
http://www.sciencedaily.com/releases/2005/03/050326114810.htm
.
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