|Rosy, but rusty: "Fresh" meat packaged with 70% oxygen.|
Good to now it's protected! Right?
If you ever bought a product like that you will have realized that you can easily store it for the whole 7day+ period in you fridge and - as long as the airtight plastic container is not broken - it will look and smell almost as it did on day one, when you rip the container open and take a closer look, whether the meat you are about to prepare is still good to eat; Looking good!
What you cannot see though, is that the "protective atmosphere" protects, may have protected the looks of the meat, but not its nutritional quality.
I mean think about it: What happens when you put metal into a wet high oxygen environment? Right! It starts to oxidize. Now guess what has happened to your appetizing piece of chicken, beef, pork or lamb while it was (highly conveniently, obviously) waiting for you in your fridge. Right it began to rust.
|Figure 1: Content of cholesterol oxidation products (COPs) in non-irradiated raw chicken/turkey leg and raw beef with packaging, and storage time; data expressed relative to baseline (Nam. 2001)|
"Although the packaging conditions of meat during storage were critical for the oxidation of cholesterol in raw meat, irradiation synergistically increased it." (Nam. 2001)And as Nam et al. point out this effect is even more pronounced if the meat has been irridated before packaging. The vacuum packaging, most producers and vendors are reluctant to use, because the meat does not look anywhere as fresh as the one that's packaged with highly oxygenated air (in fact it's the oxidized oxyhaemoglobin MbO2 that's responsible for the rosy color, cf. Rennere. 1999), on the other hand, "was enough to protect cholesterol and fatty acids from oxidation regardless of irradiation dose." (Nam. 2001)
Red deception in the "fresh" food corner
|Figure 2: T-bar levels (a marker of lipid oxidation) in air, high oxygen and vacuum packaged pork during refrigeration for 0-20 days (Cayuela. 2004)|
"[t]he use of modified atmospheres with a high oxygen concentration (70%) act[s] as a pro-oxidation factor both for fatty acids and for cholesterol (an increase of 86.4% on the initial COPS content)." (Cayuela. 2004)And that's a plus of almost 90% on top of what you would see with "regular" air packaging, as it was used in the Nam study.
Ah, and did I mention that this "meat" will also be less tender, less juicy and will have a 4-6x higher drip loss than "regular" packaged meat, when it's stored at 4°C for several days (Lund. 2004).
Don't get me wrong, you certainly won't die when you eat meat from the supermarket and still - the oxidized fats and cholesterol from the gas packaged meats from the supermarket are another on its own probably negligible piece to the puzzle that holds the answer to the complex question why we are fat and sick. One thing appears to be relatively certain, though, the terms "convenience" and "revenue" relate to almost every item on the never ending list of causative and confounding factors of the obesity epidemic in one or the other way.
- Cayuela JM, Gil MD, Bañón S, Garrido MD. Effect of vacuum and modified atmosphere packaging on the quality of pork loin. European Food Research and Technology. 2004; 219(4), 316-320.
- Lund MN, Lametsch R, Hviid MS, Jensen ON, Skibsted LH. High-oxygen packaging atmosphere influences protein oxidation and tenderness of porcine longissimus dorsi during chill storage. Meat Sci. 2007 Nov;77(3):295-303.
- Nam KC, Du M, Jo C, Ahn DU. Cholesterol oxidation products in irradiated raw meat with different packaging and storage time. Meat Sci. 2001 Aug;58(4):431-5.
- Rennere, M. Factors involved in the discoloration of beef meat. International Journal of Food Science & Technology. 1990; 25: 613–630.
- Zhang SL. Effect of UV Irradiation on the Migration of DEHP from Food-Grade PVC Film into Packaged Ground Meat . Advanced Materials Research. 2012; 601(94).