Curious Cook in the New York Times: The red-meat miracle and other tales from the butcher case

My column in today's New York Times food section is about the redness of red meats and how it's maintained in both fresh and cured cuts. Check back for some other interesting findings about meat pigments and nitrites.


Note added on April 18: the column contains an error. In the sentence

Nitrite reacts in the meat tissue to form nitrous oxide, which bonds firmly to the iron in myoglobin and stabilizes it.

"nitrous oxide" should be "nitric oxide."
Nitrous oxide, also known as laughing gas, is N2O, and nitric oxide is NO.

My thanks to Professor Douglas T. Hess of the Duke University Medical Center for pointing this out--just hours after publication!

_____________________________________

Huang, Y.-R. et al. Change of hygienic quality and freshness in tuna treated with electrolyzed water and carbon monoxide gas during fresh and frozen storage. Journal of Food Science 2006, vol. 71 no. 4, M127-33.

Sorheim, O. et al. Carbon monoxide as a colorant in cooked or fermented sausages. Journal of Food Science 2006, vol. 71 no. 9, C549-55.

Kim, Y. H. et al. Mechanism for lactate-color stabilization in injection-enhanced beef. J. Agric. Food Chem. 2006, 54, 7856-62.
http://dx.doi.org/10.1021/jf061225h

Sebranek, J. and J. Bacus. Natural and organic cured meat products: regulatory, manufacturing, marketing, quality and safety issues. American Meat Science Association, White Paper Series, number 1, March 2007.

Moller, J.K.S. et al. Mass spectrometric evidence for a zinc-porphyrin complex as the red pigment in dry-cured Iberian and Parma ham. Meat Science 2007, 75, 203-210
http://dx.doi.org/10.1016/j.meatsci.2006.07.005

Wakamatsu, J. et al. Direct demonstration of the presence of zinc in the acetone-extractable red pigment from parma ham. Meat Science 2007, 76, 385-87.
http://dx.doi.org/10.1016/j.meatsci.2006.12.006

Gleanings for Thanksgiving: turkeys and sweet potatoes

From a quick survey of recent advances in turkey science, it looks as though producers still have a lot to learn about processing their birds to give them the best cooking qualities--so that cooks have at least a fighting chance of making a tender, succulent roast.
After being slaughtered, eviscerated, and plucked, turkeys are generally immersed in chilled water to bring down their temperature rapidly and limit the growth of bacteria. The wet chill certainly improves the bird's shelf life. And by slowing down the enzymes that consume glucose for energy, it prevents the muscle cells from accumulating lactic acid and releasing fluid, a defect known as "soft exudative" meat.
But it also adds a substantial amount of water to the carcass, which makes it harder to crisp and brown the skin. And it also appears to eliminate the chance for the turkey's own muscle enzymes to tenderize and flavor the meat, as happens in the aging of beef. Scientists at Lincoln University in Canterbury, New Zealand found that rapid and prolonged chilling doesn't just slow down the tenderizing enzymes: it prevents them from acting at all. The result is "significantly tougher meat" than would be obtained if the enzymes retained some activity.
In the case of beef, cooks can compensate for inadequate aging by holding the meat for an hour or so at body temperature and giving the enzymes a chance to work much more rapidly than they can in a cold meat locker. This is one of the several benefits of cooking roasts slowly. But this kind of accelerated aging would be risky with chickens and turkeys, which have higher loads of bacteria both on the skin and in the body cavity: a temperature that encourages bird enzymes also encourages microbes. And it's not clear that the bird enzymes survive rapid and prolonged chilling.

So it's great to have more flavorful "heritage" turkeys making a comeback. Let's also figure out how to make them, and the rest of our birds, as tender and tasty as they can be.

F. Obanor et al. Effect of processing on turkey meat quality and proteolysis. Poultry Science 2005: 84, no.7, p.1123-1128.


Now a side dish. It may be that the sweetness which gives sweet potatoes their name involves more than just ordinary sugars. Chemists at the University of Naples have found that, in addition to being rich in maltose--a sugar made up of two glucose molecules--sweet potatoes contain unusual "aminoacyl sugars." These are molecules that combine a sugar (here sucrose, or table sugar) with an amino acid. In the past, chemists have synthesized similar molecules in the laboratory and found that some had a sweet taste. If the sweet-potato types do as well, then they may find use as natural and probably low-calorie alternatives to the sweeteners we now extract from cane, beets, and corn.

I. Dini et al., J Agric. Food Chem. 2006: 54, 16: 6089-93.

Grass-Fed Beef vs. Farmed Salmon

My post last August about the weak claim of grass-fed beef to healthful quantities of omega-3 fatty acids has drawn a skeptical response from Robert Buxbaum, who found a contrary view in Michael Pollan's important new book, The Omnivore's Dilemma. I'd like to dissect the discussion a bit, because I think it's a cautionary example of how easily speculations about food and nutrition can stray from the facts, become accepted as fact themselves, and end up being unintentionally misleading.

For context: I've long been a believer in the importance of local, small-scale, sustainable food production, greatly admired Michael Pollan's address in the moving opening ceremonies at Terra Madre last month, and have been a fan ever since reading his 1991 book Second Nature.

Bux wrote:
I have some comments and a question about your August 25 report on
omega-3 fatty acids in grass-fed beef. Are you comparing farm raised
salmon or wild salmon when comparing grass-fed beef to salmon? As I
posted on [Michael] Ruhlman's blog: Pollan, in "The Omnivore's Dilemma,"
mentioned that our impression of salmon as superior to beef as a
source of omega 3 fatty acids was based on measurements taken at the
time in which we first became conscious of omega 3s. That was when
most available beef was corn fed and most salmon was wild. Pollan
further claims that grass fed beef is a better source omega 3s than
farmed salmon, which is what most consumers eat now.
It seems as if how the salmon, as well as the cattle, are raised is significant in
each case.

What Michael Pollan does say on pp. 268-269 of his book is that, like industrial cattle, farmed salmon are fed on grain, and they therefore contain less omega-3s than wild salmon, which eat small creatures that have accumulated omega-3s from the oceanic equivalent of grass, the tiny phytoplankton. He then speculates (my italics) that "if the steer is fattened on grass and the salmon on grain, we might actually be better off eating the beef," and that "the species of animal you eat may matter less than what the animal you're eating has itself eaten."

In fact, farmed salmon are primarily raised not on grain but on fish meal, a feed which is problematic in its own way, but which is plenty rich in omega-3s. A thorough survey published in 2005 found that salmon farmed in various regions throughout the world have consistently higher omega-3 levels than wild salmon, mainly because they are consistently fattier. And beef? The long-chain omega-3s in grassfed beef are present at around 20 milligrams per 100 grams (about a quarter-pound) of beef. The levels in farmed salmon are around 3 grams per 100 grams of fish: more than a hundredfold higher. Even salmon raised experimentally on vegetable oil for three-quarters of their life (to begin to address the issue of sustainability) have 1 gram of omega-3s per 100 grams fish: 50 times more than grass-fed beef. These are huge differences!

So species matters a lot. Ocean-going creatures live in a cold environment and need highly unsaturated fats that won't congeal at temperatures that can approach the freezing point; mammals are warm-blooded and need saturated fats that won't be too fluid at body temperature. Even grass-fed beef still comes from a warm-blooded steer, and farmed salmon is still a cold-blooded fish. And when it comes to the highly unsaturated omega-3s, we're far better off eating salmon.

Of course this is just one small piece of a large and complicated picture. There is plenty to be said in favor of grass-fed beef, plenty of problems with salmon aquaculture, and there's more to a healthy diet than omega-3s, which we can also get from other fish and shellfish. But it's good to have each piece of the picture in the right place, right-side up, however small it is.

Hamilton, M.C. et al. Lipid Composition and Contaminants in Farmed and Wild Salmon. Environ. Sci. Technol. 2005, 39, 8622-8629.
Torstensen, B.E. et al. Tailoring of Atlantic salmon (Salmo salar L.) flesh lipid composition and sensory quality by replacing fish oil with a vegetable oil blend. J. Agric. Food Chem. 2005; 53:10166-78.

Good Fats In Grass-Fed Beef?

My friend Daniel Patterson, the chef and owner of Coi in San Francisco, recently told me that some of his meat suppliers have been promoting grass-fed beef as a good source of healthful omega-3 fatty acids, both the linolenic acid found in walnuts and canola oil, and the very long chain fatty acids characteristic of fish oils. Beef, the archetype of foods laden with cholesterol-raising saturated fats, as a health food? I took a fresh look at the numbers.
Sure enough, grass-fed beef has substantially more omega-3 fatty acids than conventional beef raised on grain or a combination of grain and other concentrated nutrients. This makes sense: green grass doesn’t have much fat or oil, but its membranes are rich in linolenic acid. When the grass is cut and turned into hay, the linolenic acid tends to be oxidized and converted into other molecules, so hay is a poorer source, and grains contain little or no linolenic acid.
Once it gets into cattle, the grass linolenic acid meets several fates. Much of it is hydrogenated by microbes in the animal’s rumen, and turned into more saturated, less valuable fatty acids. Some of it enters intact into the circulation, and ends up being deposited in both muscle and milk. And a small portion of it is converted by the cattle tissues into the longer-chain fatty acids found in abundance in fish.
So is grass-fed beef a meaningful source of omega-3s? No. An entire grass-fed beefsteak contains hundredths of a gram of long-chain omega-3s, and less than a quarter of a gram of linolenic acid. You can get the same quantities from a couple of walnut pieces and a few grams—a very small bite—of salmon or oyster. Beef is wonderful stuff, and grass-fed beef is especially lean and flavorful, but it’s still beef.

Dannenberger, D. et al., J. Agric. Food Chem. 2004, 52 (21) 6607