Sunday, May 19, 2013

Detrimental Effects of Aerobic & High Oxygen Packaging on Meat Quality: 2x Higher Lipid & Cholesterol Oxidation, Less Tender, More Drip Loss, Less Juicy... but More Convenient!

Rosy, but rusty: "Fresh" meat packaged with 70% oxygen.
I don't know about the US, but most of the "fresh" meat, you buy at the Supermarket here in Germany is packaged in what the label calls a "Schutzatmosphäre". Literally translated this means nothing but a "protective atmosphere" and it refers to the supposedly bacteria-free high oxygen air that's pumped into the airtight packaging in which the chicken breasts and beef steaks, the pork and lamb and all the other appetizingly looking meats are stored for up to a week in the fridges of the meat counter.

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)
As the data in figure 1 goes to show aerobic packaging (this is not yet a high oxygen environment) accelerates the rate of lipid and protein oxidation, so that the content of potentially hazardous cholesterol oxidation products (COPs) in your turkey legs, raw beef on day 7 is anywhere between 20-100% higher than on day one.
"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)
Now, with normal air, the nice red color will at some time give way to a brownish one, with extra high oxygen air that's used in high oxygen packaging, it will prevail, but at the same time,
"[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).



Vacuum + Irridation = Plastimeat 2.0 According to a 2012 paper the phtalate DEHP content of vacuumed meats increases "dramatically" by 2.55, 2.75, 2.18 and 2.16 times in comparison to that in control samples having a fat content of 10%, 20%, 30% and 40%, respectively, when it is exposed to 20 h of UV irradiation at an intensity 900µW/cm² (Zhang. 2012).
Bottom line: As inconvenient as it may sound, the lipid and cholesterol oxidation meat undergoes, when it is packaged surrounded by a "protective atmosphere" of highly oxygenated air is just another example of how our urge for "convenience" and immediate 365 x 24/7 availability of whatever we want to eat can contribute to the overall burden of dietary-related diseases.

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.

References:
  • 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).

1 comment:

  1. 'high oxygen enviroment'
    Context please? Wikipedia:
    http://en.wikipedia.org/wiki/Modified_atmosphere
    Looks like it's _low_ in O2, what are you on about?

    ReplyDelete