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Pink Slime, Deconstructed

The views expressed are those of the author and are not necessarily those of Scientific American.

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“I don’t eat school lunch anyway . . . It looks weird.”

BPI / The Atlantic

BPI / The Atlantic

This is from a high school student, quoted in the New York Times over the weekend, in response to a seemingly “beefless” future in school cafeterias. Most of the recent media outcry surrounds “pink slime,” the low-fat filler used to bulk up many processed meats. Coverage focuses on schools, where parents and administrators alike worry about students’ exposure to “chemically-treated” foodstuffs and poorly-labeled processed meat.

The low-cost, nutritious school lunch has long been an American institution. Smaller school budgets and larger student populations have led to schools cutting costs wherever possible. When industrial beef producers suggested a newer, cheaper meat alternative back in the early ‘90s, cash-strapped school districts happily agreed.

In 2010, Michael Moss of the New York Times won a Pulitzer for reports probing the processing end of the beef industry. He was among the first to explore the sterilization process, microbial testing, and potential contamination recalls over the past decade. Today, more journalists, along with celebrity chefs, moms, and school officials have all taken up torches and pitchforks against “pink slime”. Online articles address a myriad of questions: Where does this product come from, and where does it end up? Is it OK to eat? Why aren’t all the ingredients labeled? How is it made, anyway?

But thus far, no one has really satiated my curiosity…what, exactly, is “pink slime?”

What Pink Slime Is, and What It’s Not

Let’s address the name – there’s undeniably an “‘ick factor’…ever heard anyone use [slime] in a positive way?” (Borrowing a pithy phrase from Deborah Blum, who covered the subject for Discover Blogs)

Well, if you come from the meat producers’ camp, you instead refer to “slime” as lean, finely-textured beef, or LFTB. Connective tissue, trimmings, and scraps from industrial butcher plants are mixed in a large steel reactor, where technicians heat the mixture to 100 oF, initiating tissue lysis – fats and oils begin to rise up, while thicker bits like protein sink. After a spin on the centrifuge to separate these components, lean, squishy pink goo emerges. Ammonium hydroxide – ammonia dissolved partially in water – sterilizes the resulting mass against microbes such as E. coli or Salmonella. (Side Note: a similar product, finely textured beef, uses citric acid in place of ammonia to eliminate pathogens). Once extruded, the “slime” can be blended into hamburger, hot dogs, and other products, or frozen into pellets for shipping and storage.

But, is it nutritious? Consumers can certainly make valid arguments regarding LFTB’s content: there’s less overall “functional” protein than that found in other meat products. An analysis conducted at Iowa State University (A.S. Leaflet R1361) found two-and-a-half times more insoluble protein (77% vs. 30%) relative to soluble proteins in ordinary ground chuck. Nutritionally, our gut bacteria digest much of what we cannot, but there’s a good bet that we can’t get as much value from insoluble proteins (collagen and elastin, found largely in tendons, ligaments, and cartilage) as from their soluble siblings (myosin and actin, usually associated with muscle tissues). While these proteins may be hard to digest, on the plus side, there’s less fat in LFTB (~5%) than standard ground chuck (15-20%).

For those revolted by these contents, or even the thought of anything referred to as “slime” crossing their plates, I have two comments: first, consider Jell-O. The packaging only lists a single ingredient, which reads: gelatin. If you were to tell a child that “gummy worms” and other wobbly treats were made from steamed animal bones, would they really want dessert?

Second, consider checking the Code of Federal Regulations (CFR), the U.S. Gov’t standards used to coordinate aspects of daily life ranging from taxes to farming. In 9CFR 301.2, a collection of terms used in the meat packaging industry, we see the following definition for meat:

The part of the muscle of any cattle, sheep, swine, or goats, which is skeletal or which is found in the tongue, diaphragm, heart, or esophagus, with or without the accompanying or overlying fat, and the portions of bone…skin, sinew, nerve, and blood vessels which normally accompany the muscle tissue, and are not separated from it in the process of dressing.”

Pretty gruesome reading, true, but realize that this explanation covers everything bought at the butcher, so think carefully when considering catch-all meat products like grounds, mush, pastes, or loaves. In this light, “slime” doesn’t seem half as bad; as a culture, we’ve implicitly agreed that throat, blood, and tendons are already on the menu.

Ammonia and Other Additives

Since we’re checking the CFR, let’s consider all the other approved meat additives we encounter there. Mosey on over to 9CFR 424.21 to find a table, no less than 20 pages in length, of all the allowable additives used in meat processing: tenderizers, emulsifiers, denuders, binders, bleaching agents, and sweeteners, all on display for the discerning diner’s palate. Compared to “pink slime” seeing only brief ammonia exposure, I’m more inclined to be suspicious of sausage.

Speaking of additives, what about the ammonium hydroxide? As Blum points out, you’ve eaten it before: close molecular cousins ammonium chloride (NH4Cl) and ammonium phosphate [(NH4)3PO4] are found in licorice and breads, respectively. Plant proteins like pectins and glutens are commonly treated with ammonia for various food applications. I’m less concerned with the ammonia treatment, but more with just how much ammonia a single batch of LFTB requires to make it “safe.” Levels high enough to raise the product pH to about 9.00 rid the beef of most virulent microorganisms, but batches tested by the New York Times back in 2009 showed pH levels as low as 7.75. So what, that’s not a huge difference, right? The pH scale tracks logarithmically, so a one unit variance actually corresponds to 10 times less ammonia, which might reduce odor but also increases potential bacterial contamination.

Contrary to some news reports, ammonia is not a “pink chemical,” it’s colorless. Nor does the level of ammonia in meat even approach that found in floor cleaners. For my money, a more worrisome butcher’s helper comes from an entirely different source – carbon monoxide, which when applied to beef binds to the myoglobin and causes the tissue to develop the reassuring pink color consumers associate with freshness and quality.

One last safety note – perhaps the few examples of contamination detected really are outliers. Click here for the 40-page USDA checklist meat producers must complete to assess their sterilization measures. This document addresses all production activities, including testing regimens, sampling size, antiseptic washes, lot documentation, and cross-contamination checks. USDA even establishes a maximum target of 0.2% for lot checking; or a tolerance of 2 per thousand lots produced with positive tests (in 2007, positive tests had crept up too high, and USDA cracked down. Higher numbers of failed tests were also noted in Moss’s 2009 Times article). Surprisingly, a chart buried near the middle (p.13) of the checklist indicates that processed beef has a lower overall risk of bacterial contamination relative to standard raw beef.

“That’s the thing…it isn’t freaking labeled.”

Healthy food, healthy kid; USDA

Healthy food, healthy kid; USDA

Microbiologist Gerald Zirnstein, a meat industry critic and the man whose 2002 email inadvertently coined the term “pink slime,” delivered this rebuttal in a Reuters interview this past weekend. Under current regulations, LFTB does not have to be disclosed separately on labels, with the caveat that USDA allows a 15% maximum of the stuff in any product. However, a generation of parents accustomed to fighting high-fructose corn syrup and artificial dyes argue for inclusion of, at least, ammonia in the final ingredient list. Since manufacturers (and the USDA) consider this a production step, it, too, doesn’t need to be discretely mentioned.

So, besides loose labeling and chemical treatment, what is it about this processed meat that so unnerves customers? Certainly, it doesn’t look like a traditional cut anymore, but then neither does hamburger. The “slime” moniker doesn’t help matters, nor its public unfamiliarity – slicing animals into sections has a long history in human culture, but secondary processing of the remains is more recent. Blame cultural context: while steaks, chops, and ribs are on menus everywhere, LFTB is not. Perhaps we haven’t had time to adapt. Yet processed food still fills a necessary societal role – it’s widely available, inexpensive, and can be fortified with nutrients and vitamins.

But is LFTB really food anymore? I would say yes, in the same way those byproducts from any other organism that we consume are. Surely, most people realize that we set our table every day thanks to the labors of other life forms: honey, from bee regurgitation, yogurt, from bacterial metabolism, and multiple cheeses from calf enzymes (rennets) or via fungal decomposition. Cochineal, a crimson dye still used to color meat products (9CFR, p. 624), comes from the dried, crushed bodies of millions of tiny insects. But, compared to insects and microbes, cows hit closer to home somehow, so we revolt at a meat byproduct we don’t recognize.

So, for my final thoughts: to the beef industry, clearer labeling and heightened public awareness would help to quash some of the squeamishness at LFTB’s inclusion in the food pantheon. And to the schools and parents, well-documented and tested LFTB doesn’t seem to be much more harmful, albeit less nutritious, than the Jell-O we already serve at dessert.

Enjoy your school lunch. Bon appétit!

Note: the top image replaced on 3/28/2012.

See Arr Oh About the Author: See Arr Oh is a medicinal chemist working in industry. See Arr Oh blogs at Just Like Cooking and contributes to several other blogs, including Chemjobber, Totally Synthetic, and CENtral Science’s The Haystack and Newscripts Follow on Twitter @seearroh.

The views expressed are those of the author and are not necessarily those of Scientific American.

Comments 30 Comments

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  1. 1. matthartings 8:28 am 03/27/2012

    Great Post, See Ar Oh!
    I think that the thing I worry about most with this food product IS the nutritional value. As a chemist, I am less inclined to worry about the ammonia or the type of processing they are doing. (There are enough super-high-end restaurants doing crazy food processing that NO ONE seems to be concerned with … even when they are worried about “pink slime”) I would really like to see more work done on our ability to digest and take up nutrients from these products. Because, while processing may play a big role in jello and gummy worms as well, I don’t eat these foods as a major part of my diet.
    Really enjoyed your post.

    Link to this
  2. 2. seearroh 8:36 am 03/27/2012

    Hey, thanks Matt! I had fun writing it, though it made me a bit queasy…

    Talk about apropos timing – as this post goes live, Beef Products, Inc. has announced that they will close three of their four LFTB plants, citing consumer backlash.

    Link to this
  3. 3. cmalinak 2:57 pm 03/27/2012

    Really sad to see Scientific American post an article using the “pink slime” photo – that many have noted bears no resemblance to the actual product. LFTB is simply beef, and there is no credible evidence that it is nutritionally different than other lean beef products. Anyone who has processed their own meat knows what hamburger is made of. By the way, I do not work in the meat industry, I’m a molecular biologist.

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  4. 4. seearroh 3:43 pm 03/27/2012

    @cmalinak – I have had trouble tracking down a more reliable representation of what the final product looks like. Perhaps you could suggest a better, more accurate image to me?

    The “credible evidence” I use to make nutritional assertions in this article comes from Iowa State University A.S. reports, USDA literature, and AMI press briefs. Incidentally, the protein breakdown, and identity of the components, comes directly from a study financially supported by Beef Products, Inc.

    Link to this
  5. 5. singing flea 3:44 pm 03/27/2012

    The lower nutritional value of pink meat is not the problem as I see it. Too many people eat way to much in America anyway. What I have noticed is the prepackaged hamburger with the pink meat additives don’t keep as well on the supermarket shelves as fresh ground beef. Try leaving a package out of refrigeration next to a package of sealed fresh ground beef and see which one starts to smell bad first. I tried several packages of mixed burger meat and none had the fresh smell of 100% ground beef. I suspect this is because control conditions are rarely ideal in any giant meat packing plant and methods used to eliminate harmful bacteria are not 100% efficient. This means introduced pollution, both chemical and biological are added to quality beef in the process. There is better uses for the butcher scrap and band saw shavings then using it as a filler to stretch profits at the expense of quality.

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  6. 6. k-dub 4:31 pm 03/27/2012

    A more accurate image would be no image at all. You are just spreading the misinformation further by using that one.

    Link to this
  7. 7. seearroh 5:07 pm 03/27/2012

    @k-dub – Hmmm, OK. Let’s break this down: the physical product exists. Technicians in four plants, in four different U.S. states have seen it. It’s blended into commercially available food. The media has mounted a strong campaign against it.

    So, I repeat: who can provide me with an accurate image, if the one above is not representational? Show me the LFTB!

    Link to this
  8. 8. Ari LeVaux 5:35 pm 03/27/2012

    @seearroh BPI has images of LFTB available on its website, including the one I used for my piece in The Atlantic:

    Link to this
  9. 9. seearroh 6:24 pm 03/27/2012

    Thanks, Ari – I’ve asked the blog admin to switch it out, and credit you guys and BPI. Again, my thanks for the help. Also, great post!

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  10. 10. davidhill222 6:45 pm 03/27/2012

    Good post.
    But, in the end the truth does not matter. What matters is what those enviro-wackos make of the whole situations. The would rather die of food poisoning than eat something that is not as wholesome as they want.

    Another thing in favor of the pink slime is that it is a good example of the use of resources. Nothing goes to waste. The whole animal is processed.

    Link to this
  11. 11. Ari LeVaux 6:46 pm 03/27/2012

    Thanks See Arr Oh, and you’re very welcome!

    Link to this
  12. 12. N a g n o s t i c 9:10 pm 03/27/2012

    matthartings, you say “Because, while processing may play a big role in jello and gummy worms as well, I don’t eat these foods as a major part of my diet.”

    From the article – “Under current regulations, LFTB does not have to be disclosed separately on labels, with the caveat that USDA allows a 15% maximum of the stuff in any product.”

    15% is not a major percentage value.

    Link to this
  13. 13. N a g n o s t i c 9:15 pm 03/27/2012

    matthartings… especially since it’s not very likely that everything you eat includes LFTB.

    Link to this
  14. 14. KarlGoldman 1:26 am 03/28/2012

    There seems to be one great omission to the article. The average consumer doesn’t know that transglutaminase is meat glue to put together chucks of similar or dissimilar meat products. Nor do they know that Phenylketonurics or Phenylalanine (Artificial Sweetener ) is an amino acid that is produced in the brain and was never meant to be digested or put in one’s stomach until some chemist licked his fingers slicing human brains and thought it was sweet.
    The problem with pink slime is that rather than the chucks of glued meat that make a bologna sandwich or the bleached dark chicken meat packaged as chicken slices the consumers thought that beef put into a meat grinder was just that, not some mixture of pink slime made from the veins and snouts of cows.
    They do realize that a hotdog is good, but is bad for you. They thought they were safe when it came to ground beef. They didn’t expect a Taco company to add bone meal and fillers in which the majority of what they were eating was not beef. Now you had people for years eating something that they did not realize or thought was better for them than the average hotdog.
    Profit should not be made from a con to trick your consumer. It should be made by honest hard work. Perhaps this is why other countries have large vegetarian populations; but wait we seem to be modifying that too…lol

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  15. 15. seearroh 3:45 am 03/28/2012

    @KarlGoldman – So, uh, just “one” great omission? : )

    Since I’m your “host,” I’ll oblige:

    1. Transglutaminase, an enzyme, does indeed “glue” together dissimilar meats, simply by catalyzing peptide linkages. It’s also used in fancy ‘molecular gastronomy’ cooking.

    2. Phenyketonurics are people, not sweeteners. They cannot metabolize phenylalanine, an otherwise essential amino acid. The sweetener you’re looking for is aspartame, and it’s not even an approved artificial sweetener for meat…only saccharine gets that honor. Other approved sweeteners include dextrose, malt syrup, and sorbitol.

    3. Slicing human brains? Not usually part of my day job.

    4. Per definition in the CFR – for human consumption: veins in, snouts out.

    5. Actually, 9 CFR355.29 prohibits bone meal inclusion as a meat filler, referring to it as “inedible-not for human consumption” (in 9 CFR 325.11, USDA relegates bone meal to use in animal food). Searching the terms “bone meal + taco bell” in multiple search engines yields no reputable news source to support that claim.

    6. The US vegetarian population is growing at a good clip. See this article, from USA Today, in 2007:

    *Please consider supporting future far-reaching statements with factual sources. Thanks!

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  16. 16. Jerzy New 5:32 am 03/28/2012

    Besides, processed food is good for mankind.

    Stupid ones eat bad food and die, clever ones stay away and survive. In the longer time, future generations of Americans will be wiser. This type of selection is infinitely less brutal than being eaten by sabertoothed tiger, like our distant ancestors.

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  17. 17. redwitch1 9:40 am 03/28/2012

    3. cmalinak
    2:57 pm 03/27/2012
    “LFTB is simply beef, and there is no credible evidence that it is nutritionally different than other lean beef products.”

    Who are you trying to kid?
    3. cmalinak
    2:57 pm 03/27/2012
    “Anyone who has processed their own meat knows what hamburger is made of.”
    Yes…. ground, clean, raw, fresh, beef.

    Link to this
  18. 18. bucketofsquid 11:31 am 03/29/2012

    @Jerzy New – Very good point. The total number of cigarette smokers is dropping because smokers tend to die just a little younger. People that routinely violate traffic laws tend to be incarcerated or disabled or killed more than people that obey the traffic laws. People that over consume tend to die younger than those that don’t. The problem is that it is very lucrative to provide treatment to keep them alive.

    I for one, prefer being alive to being dead so I’ll continue to be a fan of modern medicine.

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  19. 19. INTJ_Man 9:44 am 03/30/2012

    This article seems a bit skewed towards the pro “meat processors” camp (I prefer to think of cattle farmers & ranchers as meat producers) because there are a lot of assumptions being made in regards to all the federally allowed “nasties” that are part of factory farming & mass food processing. Just because a process or additive is allowed doesn’t automatically make it benign. Being concerned about what fillers and additives are being slipped into the food supply is not being “squeamish”. Once upon a time they use to think drinking radium was good for your health.

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  20. 20. seearroh 2:34 pm 03/30/2012

    @INTJ_Man – I like to think of myself as less “pro-meat” and more “anti-hysteria” where additives or chemical compounds are concerned. I concede that industrial processes carry risks, and that we may not become aware of them until some time in the future.

    However, since you’ve commented on my choice of “squeamish,” I’ll ask about yours: how does one define “benign?” I haven’t expressly assumed that any of the additives I’ve listed are benign; as they say, the dose makes the poison. Some things, in acute (large amount / short time) doses, are harmful, but the great majority of compounds we’re exposed to in our daily lives are fine. CFR-listed meat additives usually end up at milligram concentrations in final products.

    As with any health discussion, the best cure is education before reaction. If you worry about an additive, look it up. The Merck Index is a good start, also encyclopedias, and Wikipedia about 75/25 for reliability. Failing that, consult a physician, scientist, or public health professional.

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  21. 21. diacad 3:50 pm 03/30/2012

    I’m not worried about what has recently been labelled “pink slime”. Who first coined this odious term (and why) for something which has been used and known for at least a century? In fact, processed meat products(tradenames “Spam”, “Treet”, and others) are almost pure “pink slime”, as is Vienna sausage. We serve both often in our household, and will continue to do so. Meanwhile, we have more serious health issues with the foods we eat, such as a weak FDA with resultant inadequate inspection of farms and food plants, and loopholes allowing “food supplements” and certain small local producers escape regulation entirely.

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  22. 22. billsmith 4:01 pm 03/30/2012

    Realistically, meat processors are not going to suddenly start throwing undesirable cow parts into the garbage. They will ensure that as little of the cow as possible goes to waste. In addition, I know how often people manage to poison themselves with undercooked hamburger or cross-contamination by its juices. In that light, any reasonable sanitizing method seems like a net benefit.

    Now, given that ammonia is easily driven off during cooking, this treatment seems far better than the alternative sanitizing procedures. Chlorine would leave chloramines. Sodium hydroxide would raise the sodium content. Organic preservatives might have unforseen decomposition products when flame broiled. Chemicals extracted from perilla or rosemary would be expensive and overwhelm the actual meat flavor.

    On the other hand, adding organic acids like citric (lemon), acetic (vinegar), or lactic (yogurt) seems a good solution as well. Burgers are likely to be doused anyway with a sauce containing one of those. High acidity would retard the growth of bacteria. This also seems a little more traditional as a culinary practice- with the exception of bagel crusts and lutefisk, almost all foods are acidic.

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  23. 23. 2008RealityCheck 4:01 pm 03/30/2012

    Pink Slime is the name of a short story I wrote and is available at Amazon, B&N, Smashwords. The story’s conclusion isn’t what one might expect. And while I use some fictional characters to drive the story I incorporated real facts in the investigation. I have to say, this blog is excellent in providing new details.

    Here’s a photo of LFTB being made

    Link to this
  24. 24. 2008RealityCheck 4:02 pm 03/30/2012 will take you to the publishing website and give you more detail.

    Link to this
  25. 25. meanjean 7:13 pm 03/30/2012

    Hi, here is what else I could find for you:,r:22,s:90

    I hope you can bring it up. An industrial picture of PS.

    Here’s another link to a story and picture of the actual trimmings used.,0,3620553.story

    Let me know if this works. I couldn’t paste any pictures in the comments section. I can email you if you wish. Jean

    Link to this
  26. 26. meanjean 8:11 pm 03/30/2012

    In answer to davidhill222: It’s been used for years in pet food. It doesn’t go to waste. Why are they suddenly feeding it to us? If you want to extend your groundmeat, use bread crumbs. My mother did for years.

    Safe or not I won’t eat it; if nothing else, it’s nutritionally indifferent and hard to digest, as well. Why does the industry insist we need it?

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  27. 27. Eric Rasmusen 10:16 am 04/5/2012

    Good article! I will find it useful in my economic regulation class, on the tough question of whether information disclosure is always good, and what consumer expectations are.

    I do wonder about the issue of the digestibility of beef scraps (we are getting revenge on the food industry for inventing the awkward name “lean, finely-textured beef, or LFTB”– “pink slime” is so much handier). I think what you’re saying boils down to beef scraps having more gristle than ground steak. A lot of gristle (most?) is collagen. Raw collagen is, as you, say, less digestible. Is elastin? I found this quote “During the digestion of meat in the human gut, elastic fibers are broken down by elastase, an enzyme from the pancreas that would not be there if our evolutionary ancestors had not been at least partly carnivorous. In other words, I have never read of the occurrence of elastin in any human food except meat. So if we have evolved a highly specific enzyme, elastase, to deal with elastin in our food, this can only mean that we are the descendants of meat eaters.”

    Also, while raw collagen needs bacterial help to digest, sufficiently cooked collagen does not— it turns into gelatin. Is the slime processing good enough for that? How about cooking the hamburger? Since the collagen is ground up finely, it maybe needs less cooking to hydrolyze. Any reader of this blog know the answers?

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  28. 28. Eric Rasmusen 11:04 am 04/6/2012

    Here’s an even more palatable pink slime picture:

    This stuff, like ground beef, can be molded into any shape you like, ugly or attractive.

    Link to this
  29. 29. WyoMike 12:12 am 04/15/2012

    I enjoyed the blog. Seemed pretty balanced…maybe leaning towards a “Buyer beware” approach. That seems fair. There arguments for being less wasteful. The process which produces LFTB seems to help us do this. I have processed my own meat many, many times (usually venison and once elk). That process taxed me. I knew the meat. I knew where it came from. I accepted a standard lower in cleanliness than is set as norm for commercially produced meat. But the experience was good for me to realize just how picky we’ve become as a people regarding our food (which is good in some ways and not so good in others). LFTB is not pretty. But I can see its purpose. And I accept its presence as long as I know it is present.
    Good blog. Thanks.

    Link to this
  30. 30. vanDeemter 10:30 am 05/3/2012

    Nice article, but I have one minor quibble. You greatly oversimplified the relationship between the pH and the amount of ammonia added.

    First, “ammonium hydroxide” is not a strong base–it is actually an aqueous solution of ammonia, a weak base, which complicates the calculations. In pure water, you would need about 1.05e-6 M ammonia to get pH 8, and about 1.57e-5 M to get pH 9. This is about 15 times as much, not 10 times.

    But even more importantly, we’re not starting with pure water. You ignored the buffer capacity of the meat itself, which is substantial: proteins are polyprotic weak acids and bases. The buffer capacity of protein should increase slightly as you go from pH 8 to 9 because you are getting closer to the pKa’s of many of the side chains. Using ammonia to adjust pH is like titrating with a weak base, which requires much more base than if the titrant were strong. And since the starting pH is probably around 6 (Google pH of meat for some more fun reading), it must take an awful lot of ammonia to get even to pH 7.75, let alone 9.

    Link to this

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