What a Gas! Packaging Meat in Carbon Monoxide

By Christopher R. Raines

Packaging meat in carbon monoxide (CO) has its perks, yet it is likely that public sentiment toward packaging fresh meat in carbon monoxide is anything-but-positive, even though the level of CO is miniscule (~0.4%).  I am writing about CO because of a previous entry (Color of Fresh Meat, 23 September 2009) that summarized the color dynamics of fresh meat, the different “forms” of its primary pigment, myoglobin [i.e. Deoxymyoglobin, Oxymyoglobin (OMb), Metmyoglobin] and the associated colors thereof.  In the upper right of the diagram in that entry there is a fourth “form,” Carboxymyoglobin.  This fourth pigment form appears very similar to OMb, yet develops due to the binding of CO, not oxygen, to myoglobin.  And today the question lingering may be:  “Why would one package meat in a toxic gas?!”

Beef packed with (above) and without (below) CO

Beef packed with (above) and without (below) CO

As I tend to do in this blog, I mention an anecdote related to the topic at hand. In this instance, I supply you with a story about dihydrogen monoxide in the minds of impressionable youth (granted, these students had some sort of meat science background):

  • The setting: a college classroom
  • The students: a mix of science and business sophomores and juniors
  • The question: Dihydrogen monoxide is a colorless, odorless chemical compound that can cause burns when vaporous, may lead to human injuries when solid, has been used in concentration camps, dungeons, and other human rights crimes, is implicated in many deaths worldwide each year, yet amazingly, it is found in nearly every food.  What should be done?
  • The response: About 50% wanted to ban its food use immediately and another 30% suggested further investigation be conducted before banning it, while another 20% (gasp! only 20%!) recognized that dihydrogen monoxide (H2O) is water.

This entry is about CO, and yes, I realize that CO and H2O are different and that I’m not comparing apples to apples.  I am, however, fruitfully (I hope) comparing scary-sounding word to scary-sounding word.

Researchers have found the use of CO in fresh meat packaging to be an effective way to prolong its shelf-life (shelf-life is the time span in which a food product remains “good” — before its microbial and sensory quality deteriorates).  Meat processors in Norway started using CO in meat packages on a commercial scale in 1985, yet stopped when the E.U. prohibited its use.  The CO level was about 0.3-0.5% of the gas composition of the package in Norway.  (Gas composition of the package? When meat is packaged for display in retail self-serve cases, the atmosphere within the actual package can be altered to minimize oxidative deterioration, retard microbial growth, and improve product appearance.) Packaging many vegetables in a CO-inclusive atmosphere — for its preservative effect — has been recommended for the U.S. for approximately 35 years.

An example of a modified atmosphere packaged meat, the barrier lidding is absent

An example of a modified atmosphere packaged meat, the barrier lidding is absent

Major Concern A: the safety of CO, for workers and consumers.  The amount of CO in a typical meat package (in the U.S., 0.4% is allowed, or 4,000 ppm) is comparable to that of cigarette smoke or van exhaust.  When a meat package is opened into a room of normal size, that CO is diluted to ~0.04 ppm.  In comparison, the EPA estimates that in 2002, the average CO concentration in city air was 1.8-4.4 ppm.  As such, the risk for CO exposure is just not there.  So much for Major Concern A…

Major Concern B: CO “masks” spoilage of fresh meat. Carbon monoxide will make fresh meat appear red, longer.  The absence of oxygen (since we now have CO to allow the red color develop) means that meat won’t get “rancid” or “off” (oxidize).  Some are concerned that meat will look fresh when it may be dangerous due to microbial growth (notably, some of those those who have voiced major concern also manufacture antioxidants for use in meat …), even though when CO is used at 0.4%, microbial growth is not masked in beef.  Adding to the debate is the issue that if meat smells bad, don’t eat it (since odors are associated with microbial spoilage). The other form of packaging that does not use CO uses instead high levels of oxygen (~20-30%) in the package’s atmosphere.  Intuitive (and this has been proven in science, too), meat packaged in high levels of oxygen will … oxidize!  And because we are now all experts on the color cycles of meat, we realize that oxidized meat will prematurely brown, which poses and entirely different risk.  Now I’m in the meat science doldrums… If meat is packaged with CO, spoilage-induced color changes may be masked (but spoilage odor due to bacteria won’t), yet if meat is packaged without CO it will look done before it is really done.  My summary for B: there may be a small risk for masking spoilage in CO, yet the meat lasts longer, and I think that’s a good thing [as outlined in (My) Major Concern C].

(My) Major Concern C: Each year, retailers pitch a lot of good ground beef and other meats because they just don’t look good.  Could, then, either (1) the retail cost of meat be reduced if CO is used (because less will be tossed out and its value lost), or (2) would less meat need to be produced altogether (because less would be tossed out and wasted)?  I think both of those are valid points in defending the use of CO.  Concern C is just my own personal thing...

For a comprehensive review of CO use in fresh meat packaging, there is a white paper available — Many of the figures presented in this entry are found in this thorough paper. It’s pretty sciencey, but if you’ve got the itch to learn more about the science of carbon monoxide in meat packaging systems, there it is for you to read.


3 thoughts on “What a Gas! Packaging Meat in Carbon Monoxide

  1. Pingback: Color of Fresh Meat: The Basics « meatisneat.wordpress.com

  2. Pingback: Are You Buying Old Food at the Grocery Store? | Fooducate

    • Very few retailers use CO in their modified atmosphere packages. Most use a “high-oxygen” blend of 70% or 80% oxygen (to saturate the pigment, creating a thick layer of red oxymyoglobin) and balance it with carbon dioxide (antimicrobial). Many household plastic films are oxygen permeable, allowing the meat to retain its red color. That, in combination with the saturated outer layer of OMb, may be why it looks “just as good.”

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