DATE June 27, 2002 ACCOUNT NUMBER N/A
TIME 12:00 Noon-1:00 PM AUDIENCE N/A
PROGRAM Fresh Air
Filler: By policy of WHYY, this information is restricted and has
been omitted from this transcript
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Interview: Robert Wolke discusses the science of food
TERRY GROSS, host:
My guest, Robert Wolke, is an expert in kitchen science. He explains the
chemical and physical principles behind the behavior of the food we cook and
the utensils and appliances we cook with. Wolke writes the syndicated
Washington Post column Food 101, which won the James Beard Foundation Award
for best newspaper column. And he has a new book called "What Einstein Told
His Cook." Wolke is also a professor of chemistry at the University of
Sometimes you go to the fish store, you buy a fish, you take it home, and it
smells fishy. And when that happens to me, I don't even know if I want to
keep it because it just shouldn't have that kind of smell. What are we
smelling when we smell that fishiness? What's giving off that odor?
Professor ROBERT WOLKE (Author, "What Einstein Told His Cook"): Largely, they
are chemicals called ammines. The simplest one that everyone's familiar with
is ammonia, itself. But ammines come from the breakdown of amino acids.
Amino acids, obviously, from the name, have what chemists call an amino group
in it, and ammines are generally smelly compounds. So when the fish begins to
decompose, the amino acids break down into ammines and it smells that way.
If, with your scenario, if you bring it home and it smells fishy, I would
recommend buying your fish somewhere else.
GROSS: If it smells fishy, does that mean you should just throw it away?
Does that mean that it's already bad?
Prof. WOLKE: Not necessarily because--getting back to our senses, our sense
of smell is incredibly sensitive, and those amino compounds are very smelly.
So we smell that unpleasant smell long before the fish becomes unhealthful.
So a slight fishy smell is OK. If it--you'll know it when it's unhealthfully
decomposed; the smell will be more than you can keep in your kitchen.
GROSS: Why does fish spoil so quickly?
Prof. WOLKE: Its muscle tissue is made of relatively thin fibers compared
with the muscle fibers, let's say, in beef or pork or any land animal. And
that's because they're so-called fast-contracting fibers. If you think about
what a fish needs to escape a predator, compared with let's say what a land
animal needs to escape a predator, the land animal has to run like the devil,
perhaps for miles, not just fast, but long distances, to outrun a predator,
say, a lion, a tiger, or something, so it needs long muscles that provide long
endurance. A fish, in order to escape a predator, just flips its tail faster
than the eye can see and darts away. So its muscles are these very thin
fibers of fast-contracting muscle tissue and these thin fibers are easier to
decompose by various decomposition things, even cooking, for that matter,
than, let's say, beef is. And that's why fish cooks so much faster than beef
because you don't need to keep it hot as long in order to break down these
muscle fibers and make it tender.
GROSS: When you're buying fish at a store, do you usually smell it before
Prof. WOLKE: Sometimes I do. Sometimes I don't. I nearly got killed when I
did that in Marseilles, France. The fishermen were just bringing things in
and selling it right there on the shore. And I wanted to buy some squid and I
just bent down and sniffed at the squid. That French fisherman had never been
so insulted in his life. So I've been--and fortunately I had a friend who
could speak rapid-fire colloquial French and calm him down but the answer is
you do it when it appears to be acceptable.
GROSS: You recommend using lemon to counteract the fishy smell of fish.
Would you be using the lemon before you cook the fish or after it's cooked?
Prof. WOLKE: The reason is lemon is usually served with fish in restaurants,
a wedge of lemon, is that these ammines that are the smell from let's say fish
that is too fishy smelling are alkaline and lemon juice is, of course, acid,
which counteracts the alkaline, unpleasant flavors in fish that has either
been, let's say, cooked too long or wasn't as fresh as we would have liked to
have been before it was cooked. So it generally is added afterwards.
Sprinkling fish flesh with lemon juice before you cook it wouldn't do much
good because it--well, it would run off and wouldn't stay long enough to do
its neutralizing job.
GROSS: So, gee, isn't serving lemon with fish in a restaurant almost a sign
that there's a fishiness that needs to be modified by the lemon, that...
Prof. WOLKE: Yeah, I...
GROSS: ...there's something you have to counteract.
Prof. WOLKE: I've often asked myself that question but I think it's just
become part of our culture. It's just...
Prof. WOLKE: It's become habit, that's all. And I think probably the chefs
don't even know why they put the lemon wedge on, but diners expect to see it,
and there it is.
GROSS: My guest is Robert Wolke, author of the new book, "What Einstein Told
His Cook: Kitchen Science Explained." We'll talk more after our break. This
is FRESH AIR.
(Soundbite of music)
GROSS: Robert Wolke is my guest. He's the author of the new book "What
Einstein Told His Cook: Kitchen Science Explained."
In your book, you write a little bit about those non-fat aerosol sprays that
you're supposed to use to prevent your eggs or your chicken, whatever, from
sticking to the frying pan. And on the one hand these sprays say that they're
non-fat; on the other hand, if you read the ingredients, there's oils in it.
So you explain that.
Prof. WOLKE: Yeah, that's something funny about those things. They do say
they're non-fat and they say only 1/10th of a calorie or something like that,
per serving. That's one of the services I think I do for my readers in their
roles as consumers outside the kitchen. It's a dodge because the Food and
Drug Administration which has to rule on how much fat can be called no-fat has
a problem. I mean, if a serving contains let's say a gram of fat, is that no
fat? It contains only 2/10ths of a gram of fat--When do we say it has no fat?
Well, the manufacturers of these non-stick sprays, these non-fat
sprays--which, as you point out, are fat. That's what they are. They're
oils. They get around this by defining a serving and all the FDA rules are in
terms of how much of this or that one serving contains. Well, they define
their servings as such a short blast of this spray that, of course, it's below
the half a gram of fat that the FDA defines as permissible to say it has no
fat. One major brand defines a serving as a one-third of a second spray. Now
who can limit his or her trigger finger to a one-third of a second spray? And
then it also says on the label that serving is enough to cover the--to cover
one-third of a 10-inch frying pan. Now all of that arithmetic manipulation is
done for one purpose, just to keep the amount of fat in it, in the serving,
below a half a gram that the FDA permits to be said as none.
GROSS: With July Fourth coming up, I thought I'd ask you about grilling food.
Why does charcoal-grilled food taste so good? What's the chemical--scientific
explanation for that?
Prof. WOLKE: It is chemical. It is not inherent to charcoal. We call it the
charcoal-grilled flavor, I guess, because charcoal was the--pretty much the
only way to grill before the gas grills started becoming popular. But there's
nothing about the charcoal, per se, that makes the flavor. What makes that
charcoal-grilled flavor is the very--first of all, the very high temperature
that the surface of the meat or whatever is exposed to. Grilling has to be a
very high temperature or you don't get those browned flavors that high
But also some of the flavor comes from--let's say we're doing steak or
hamburger or something that has fat in it--and hot dogs--that's why these are
all such popular things to grill, they are fatty, to some extent, and the fat
will melt, and drip down onto the charcoal where it might go--Poof!--and
create some smoke and it's the smoke that--or the products from the burning
fat that rise, of course, with the heat and may deposit themselves on the
bottom of the steak. So it's the fact that juices are dripping down, getting
quickly incinerated, producing, let's say, gases and fumes that condense on
the food. And that's pretty much the--what we call the charcoal flavor. But
remember I said it just has to drip down on a hot surface. That hot surface
doesn't have to be charcoal. And that's why even gas grills produce the,
quote, "charcoal flavor," unquote, because the juices drip down on, let's say,
a hot piece of ceramic or one of those volcanic stones or whatever they use.
And you get the same effect.
GROSS: Well, I want to thank you very much for talking with us.
Prof. WOLKE: Thank you, Terry. It's been my pleasure.
GROSS: Robert Wolke is the author of the new book "What Einstein Told His
Cook." He also writes the syndicated Washington Post column Food 101.
GROSS: I'm Terry Gross.
We'll close with a composition by Thelonious Monk. His widow, Nellie, died on
Tuesday at the age of 80 of a cerebral hemorrhage. He wrote this composition
for her in 1957 when she was in the hospital undergoing surgery. It's called
"Crepuscule With Nellie." `Crepuscule' means `twilight.'
(Soundbite of "Crepuscule With Nellie," by Thelonious Monk)
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