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The more I read about this subject, the more glad I am that I don't eat meat, though I do consume small amounts of gelatin. After recently investigating the scientific literature on this subject, if I were to eat meat, I would freeze it for two weeks (as Enig and Fallon suggest in their book, "Nourishing Traditions"), then let it thaw and place it in an antioxidant-rich sauce at low temperature until warm enough to be tasty. My sauces of this kind are usually tomato and herbs or curry and corn based. Considering how little meat I would actually use, I doubt this would present any major health hazards. However, I asked biologist Ray Peat a few questions on this subject, and here are his response:
1. When boiled, the meat is not exposed to air, so how are the radicals generated?
===There's enough in the meat, along with lots of iron and other oxidants, to do it. When meat is cooked, the oxidation processes proceed rapidly, even when it's stored at refrigerator temperature. Raw/living meat kept in the fridge for a day keeps consuming the reactive electrons, but once it's cooked, 24 hours in the fridge produce the stale taste of peroxidized fats and proteins.
2. My guess would have been that if one boils meat, then puts it in an antioxidant-rich sauce at low temperature, this would be the safest way to eat meat. Is there any problem with this idea?
====In dead stuff, antioxidants don't do much, and some combinations can be mainly pro-oxidant.
3. Another method, which seems reasonable theoretically, would be to put a piece of meat in a pot of boiling water for a few minutes, then transfer it to a pot of cold water, to acheive a pasteurization type of effect. The idea would be to limit its exposure to air, and then it could be cut up and put in an antioxiant-rich sauce. Any thoughts on this?
====Eating it while it's still warm from cooking, and digesting it quickly, would be best. Salt and saturated fats would inhibit oxidation in the stomach and bowel somewhat.
4. When they say that boiled meat is lower in nutritional value, what do they mean? If they mean lower amounts of iron and "essential fatty acids," then this may be good, not bad.
====The increased peroxidization affects everything. Beef, lamb, other ruminants, are the best for boiling, because of low PUFA. Poached salmon, extremely high peroxidation, is at the other extreme.
5. Is it the case that some of these tests, such as TBARS, don't address the creation of HCAs, but instead focus on lipid peroxdation? If this is so, then the meat cooked while exposed to air may have already "lost" much of its PUFA content, or am I missing something here?
====Searing the meat quickly, as in a flame or over glowing coals, or dipping it in very hot coconut oil or tallow, minimizes the surface HCA formation, and leaving the inside rare to some degree is safest, and tastes best. A quick microwave heating, for people who don't like the bloody look, is safer than boiling.
My comments: one is not obliged to eat the seared surface area, so it might be a good idea simply to eat the rest of the meat and discard the surface. Also, I have seen experimental studies that discuss how good prunes, rosemary, and some other herbs/spices are at keep lipid peroxide to very minimal levels, so I can't say that I agree with the idea notion that antioxidants are of little use. As I said above, it might be best to simply freeze the meat a couple of weeks, then prepare it with antioxdants shown to be effect at preventing lipid peroxidation in meat. |
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A follow-up question:
So would it be a good test to cook the meat, then put it in the refrigerator for 24 hours in a container that is not air tight, to see how much rancidity there is?
==== Once it's cooked, exposure to air won't make much difference. Iron is let loose when proteins are denatured. With samples from the same piece of meat, one cooked a day earlier, getting them the same temperature to eat, the taste should be easy to notice.
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One thing that confuses me about your point concerning the
ineffectiveness of antioxidants used on cooked meat are the stuides
such as the following:
QUOTE: To help satisfy consumer demand for more natural food
products, researchers at Texas A&M University are investigating dried
plums as a meat preservative.
"We found that dried plums, when pureed, actually have a very good
antioxidant capacity," said Dr. Jimmy Keeton, professor of animal
science and leader of the research at Texas A&M.
"We've been experimenting with dried plums and plum juice in
different types of products such as pre-cooked pork sausages, roast
beef and ham to see which of those products will respond most
effectively as antioxidants," he said. "We found that pre-cooked and
uncured products like sausages and roast beef actually respond the
best."
Antioxidants retard oxidation of fatty acids that make up fat, he said.
"If these are unsaturated fatty acids, they can oxidize more and
produce off-flavors and cause shelf life problems," he said.
Synthetic products called BHA (butylated hydroxyl anisole) and BHT
(butylated hydroxyl toluene) have long been used as antioxidants. The
natural product, extract of rosemary, is also used. UNQUOTE.
Is there something I am missing, because I have to say that I'm a bit
confused at this point.
===If it is either chewed or ground up with the sauce, that would
make a difference, because the dead stuff has little organization,
and any antioxidant action would be on a very local scale. Meat
science is mostly marketing. Mince-meat and pemmican were traditional
meat preservation methods that no one has really studied in detail,
but things like plum puree will have a range of actions, including
the chelation of some of the oxidants, the reduction of some of the
oxidized catalytic states of metals (and the activation of some
previously sequestered metals), lowering the pH causing the proteins
to condense and be less reactive, etc. Raw meat is the safest, and
the quickly seared surface for disinfection and flavor is the next
best.
J Agric Food Chem. 2001 Nov;49(11):5662-7.
Oxidation process affecting fatty acids and cholesterol in fried and
roasted salmon.
Echarte M, Zulet MA, Astiasaran I.
Departamento de Bromatologia, Tecnologia de los Alimentos y
Toxicologia,
Universidad de Navarra, 31080 Pamplona, Spain.
Salmon was processed by three different culinary techniques: pan-frying
with
olive oil, pan-frying with soya oil, and roasting. Roasting did not
modify the
fat content from that of raw samples. Frying increased the fat content
2-fold,
with no difference between samples fried with different oils. Total
cholesterol
oxidized products (COPs) were 0.74, 2.98, 3.35, and 7.38 microg/g fat
in raw,
fried with olive oil, fried with soya oil, and roasted salmon,
respectively,
which represent 0.01, 0.08, 0.09, and 0.15% of cholesterol. A
significant
correlation (r = 0.902, < or = 0.01) was found between acidity index
and total
COPs. The most abundant COPs were 7-ketocholesterol, which appeared in
all the
samples, and cholestanetriol (one of the most citotoxic COP), which
appeared
only in cooked samples (1.05-1.33 microg/g fat). All cooked samples
supplied
more omega-6 polyunsaturated fatty acids (PUFAs) than raw samples and
showed
higher omega-6/omega-3 ratios. Roasted salmon showed the lowest omega-3
content
and the highest PUFAs/(SFAs)-C18:0 and MUFAs+PUFAs/(SFAs-C18:0) ratios.
I found a good description of how pemmican is made at http://www.smokylake.com/history/native/pemmican.htm and the question that comes to mind is, how does it last so long (considering the exposure to sun and air, etc.)? I thought it was made by boiling, and I was also surprised that a great deal of fat was added to make the pemmican, and yet rancidity was not a problem. I knew that gelatin was made by boiling, and so I thought that exposure to atmospheric air was the most important factor in determining which cooking method for meat was healthiest (I also recently saw a study that found that steamed salmon producd the most oxidized cholesterol, which is consistent with this notion). Would it be possible to do this with the proteins in a typical steak, or is it only safe (or possible) when done with hides and this kind of material?
The way I thought I understood it was that antioxidants could be removed by the cooking technique, that a highly unsaturated fat source would be more susceptible to air, light, temperature, etc., and that other things, such as a lot of iron in the food item, would generate more free radical activity. When you talk about the lack of organization of "dead" things, I am assuming you are thinking in terms of Ling's findings here. I can understand that if ions are bound to the structural proteins of the cell, they would be less reactive initially, but won't the food be broken down during the digestive process, at some point liberating iron, etc. ?
The study you cited is interesting, because (unless they wrote it up in a confusing way), roasted salmon had the "highest PUFAs/(SFAs)-C18:0" ration. How could one take raw salmon, measure the PUFAs, then roast it, and the PUFAs are then more abundant? Or is it that they are just talking about the cooked samples? It is not clear, but the way it is written it seems to me that they are saying that after roasting, the salmon had more PUFAs than the raw sample, and if so, where did these extra PUFAs come from?
===I don't think I would want to eat the traditional pemmican. V. Stefansson's descriptions, including the remark that eskimo women of 60 looked as old as Europeans at 80, and his comments on learning to like rotten fish, never stimulated my appetite, but his main contribution was that meat is better than canned lemon juice for preventing scurvy, or whatever it was that killed the polar explorers.
The absence of tryptophan in gelatin should make it an effective chain-breaker, because tryptophan is so reactive. During digestion, iron's route from heme or protein binding in the food to new sites in the assimilator is shortest when the meat is freshest and most nearly raw. After slaughter, metabolism continues, but in progressively more destructive pathways, with oxidations and reductions that become less biological as they move toward equilibrium. Cooking stops the biochemical processes, and that makes some of the oxidation and reduction pathways change. Fats and proteins tend to coalesce and cross-link.
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Source of the passage quoted in the above post:
http://www.sciencedaily.com/releases/2006/11/061106164429.htm |
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