Has your food gone rancid?
From: www.baltimoresun.com - March 7, 2012
By Monica Eng, Tribune Newspapers
Has your food gone rancid?
Consumers may have kitchen full of dangerous products and not know it
Does your cupboard hold a package of unfinished crackers? An old bag of
whole grain flour? Some leftover nuts from holiday baking? Or perhaps a
bottle of vegetable oil you've been slow to finish?
If so, you may be harboring dangerous, rancid foods.
Protecting against rancidity — which occurs when oils oxidize — has long
been a challenge for home cooks, but a recent perfect stew of factors has
made the issue more serious. Strangely enough, this situation comes courtesy
of the rising popularity of "healthy" polyunsaturated fats, whole grain
flours and warehouse stores — not bad developments on their own, but
taken together they've resulted in American pantries full of food that
goes rancid much faster than we're used to.
Add to that Americans' growing acclimation to the taste of rancid foods,
and the problem gets bigger.
So what's wrong with eating rancid oils?
"There are at least two," says lipid specialist and University of
Massachusetts professor Eric Decker. "One is that they lose their
vitamins, but they also can develop potentially toxic compounds" that
have been linked to advanced aging, neurological disorders, heart
disease and cancer.
"They're carcinogenic, pro-inflammatory and very toxic," says integrative
medicine specialist Andrew Weil. "They are also widespread in the food
chain."
The growing problem comes as a byproduct of Americans and food manufacturers
swapping trans fats for polyunsaturates in their products over the past 10
years. This has resulted in a whopping 58 percent drop in trans fatty acid consumption in the U.S. in the past decade, according to a recent government
report. But for all of their artery-blocking evil, trans fats had at least
one big benefit: They were very stable, meaning they took forever to go
rancid. The same is true of highly refined white flours.
But when these flours and fats were replaced with whole grain flours and
polyunsaturates, such as corn and soybean oil, that shelf stability
collapsed.
"Manufacturers noticed this and had to change their delivery schedules
and formulations," says Kantha Shelke a food scientist and spokeswoman
for the Institute of Food Technologists. "And some consumers became
irrationally angry that their food was not lasting as long as it had
before."
Indeed, while Americans followed orders to ditch saturated and trans
fats for polyunsaturated (vegetable) and monounsaturated (olive, canola
and peanut) fats, they didn't realize these healthier fats don't last
nearly as long.
"People buy these huge containers of oil (at warehouse clubs) and just
don't realize that there's no way they can use it before it goes rancid,"
Decker says. "They don't recognize it as a problem."
While monounsaturates (like olive or peanut oil) also can go rancid after
about a year, they are still 10 times more stable than polyunsaturates,
according to Decker.
"People need to minimize their use (of polyunsaturated oils)," Weil says.
"And if you do use them, keep them in the refrigerator in the dark, and
buy only small amounts that you use up quickly."
And while some consumers can sniff out (and toss out) rancid foods, many
don't know the telltale stale, grassy, paintlike odor. Others may not be
able to detect them through layers of other flavorings. And still others
might feel compelled to consume them out of thriftiness or hopes that a
strong sauce will mask the taste.
Because air, light and heat speed up oxidation, it's normally a bad idea
to, for example, buy vegetable oil in a clear bottle and place it on the
counter in a warm kitchen for several months.
Exotic oils (macadamia, walnut, sesame, fish, flaxseed, etc.), nuts and
whole grain flours are also major candidates for fast rancidity, and
should all be stored in the refrigerator or freezer. Whole intact grains
and nuts in their shells, however, last much longer.
"When grains are ground, their interiors are exposed to the air," says
food scientist and author Harold McGee. "The whole grains contain the
germ and the bran, both of which are rich in oils, that are especially
prone to oxidizing and going rancid. So you end up with off flavors
very quickly in whole grain flours compared to refined flours."
Frequent shopping for small quantities of fresh and freshly processed
foods has served much of the world well in avoiding rancid food.
Americans, however, favor a different grocery-shopping pattern that
involves less-frequent trips for larger quantities of shelf-stable
foods.
Trans fats, preservatives and refined flours combined to train a couple
of generations of Americans that "chips, cakes, cookies and crackers
could last for months," Shelke notes, "and we became accustomed to
that."
Those habits may change in time, but until they do, Weil suggests that
consumers train their "noses to recognize the smell of rancidity even
in parts of a dish."
Though some hope that our sense of smell and taste can help us avoid
rancid foods, recent studies raise doubts. Shelke notes that new
immigrants to America often think peanut butter — now often made
with polyunsaturates — smells rancid while American natives think
it just smells like peanut butter.
McGee notes that the problem extends to rancid olive oils, which,
in a 2011 University of California study, were actually preferred
by 44 percent of American tasters.
"We assume that rancid flavors are normal," McGee says, "because,
in some cases, that's what we've gotten used to."
The smell test
A rancid food is "the smell of oil paint," says integrative medicine
specialist Andrew Weil. "Linseed oil, which is the same as flax oil,
is the basis of oil paint. It's highly unsaturated and so it oxidizes
fast when exposed to the air."
How long is this good?
Although the FDA oversees advice on the safe storage of food at home,
it has not updated its recommendations since the gradual switch from
saturated fats to unsaturated fats in food production.
Experts advise paying close attention to "use by" and "sell by" dates
on packages, which may have changed in recent years because of new
formulations.
The Institute of Food Technologists' Kantha Shelke says she's found
that similar boxes of soda crackers using refined and whole grain
flours had shelf lives of 141 and 80 days respectively when left
unopened.
In general, buy products that contain oils or fats in small quantities.
Store most cooking oils in a cool, dark cabinet — not next to the stove.
Refrigerate polyunsaturated oils especially fish, nut and flax seed oils.
Store nuts and whole grain flours in the freezer.
