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Freezer Burnt Meat

Photo credit: flickr/Steven Depolo

Photo credit: flickr/Steven Depolo

Freezing is an indispensable tool in modern cooking and eating. The biochemical processes that typically occur in meats cause decay, fat oxidation, and rancidity; the higher the temperature, the faster these reactions occur. Thus, we can largely thwart off these undesirable processes by keeping meat chilled. But tossing meat into the freezer rarely results in rainbows, sunshine, or perfect burger patties, because strangely enough we can also accelerate meat decay with cold. Freezer burn can take a beautiful filet mignon and turn its surface into a leathered, unappetizing slab.

Freezer burn is caused by water sublimation from ice crystals at the meat’s surface into the dry freezer air. Sublimation occurs when a solid substance undergoes a phase change and becomes a vapor without first passing through the liquid phase. The ice crystals on the meat surface sublimate, and leave behind tiny cavities. These tiny yet numerous cavities increase the surface area of the meat and expose more tissue to the air. This accelerates oxidation of fats, which causes the rancid flavors of old spoiled meat. We usually describe oxidized fats as simply tasting “off,” which is a vague term but seems apt if you’ve ever tasted lipids past their prime, perhaps by using shortening that has been in the pantry since you were a toddler.

Photo Credit: flickr/Marcus Ward

Here, solid ice crystals directly vaporize without first passing through the liquid phase. Photo Credit: flickr/Marcus Ward

In addition to the surface area increase caused by sublimation, the freezing process itself lends itself to fat oxidation. When the liquid water in meats crystallize in the cold, the concentrations of oxidizing salts and trace metals in the tissues increases. Unfortunately, oxidation can occur over time even in wrapped and frozen meats. Some oxygen will inevitably remain in contact with the meat, unless we create a vacuum seal.

Once meat has been damaged by the cold, there’s no undoing the oxidation. So either we plan our meals so that meats are cooked immediately after purchase, or we learn to prevent the sublimation that ruins both our pork chops and our days. We simply need to keep water crystals inside the meat and keep oxygen out. Using a vacuum sealer is our best bet for avoiding freezer burn, but for cheapskates like me who won’t shell out the $30 for the sealing device, a water-impermeable plastic wrapped tightly around the meat works well enough for most home chefs.

Thus meat is sealed away happily in plastic, free from villainous oxygen. Photo credits: flickr/Mike

Thus meat is sealed away happily in plastic, free from villainous oxygen. Photo credits: flickr/Mike

References cited

  1. McGee, Harold. “Meats.” McGee on Food & Cooking: An Encyclopedia of Kitchen Science, History and Culture. London: Hodder & Stoughton, 2004. N. pag. Print.
  2. “Sublimation.” The Columbia Electronic Encyclopedia. Columbia University Press, 2012. Web. 20 July 2015.

 


Elsbeth SitesAbout the author: Elsbeth Sites received her B.S. in Biology at UCLA. Her addiction to the Food Network has developed into a love of learning about the science behind food.

Read more by Elsbeth Sites


Follow-Up Q&A with Ole G. Mouritsen

Onodera, translator, and Mouritsen at Science of Sushi. Photo Credits: (Matthew Kang/Eater)

Onodera, translator, and Mouritsen at Science of Sushi. Photo Credit: Matthew Kang/Eater

The audience present at The Science of Sushi asked our guest lecturers some great questions, and quite a few of them! Unfortunately, there wasn’t enough time to answer them all, but Ole G. Mouritsen has been kind enough to answer some of the lingering questions that went unanswered. Below his responses, we have included some additional information to help quench your thirst for knowledge (and sake).

Q: Are parasites within fish common? Are they a passable health problem?

A: Parasites can be common in some species, e.g., cod, mackerel, herring, and wild salmon. If in doubt, always freeze or marinate fish before eating raw.

The FDA provides guidance under their Parasite Destruction Guarantee on the preparation of raw fish. Fish intended to be consumed raw must be “frozen and stored at a temperature of -20°C (-4°F) or below for a minimum of 168 hours (7 days)”. [1]

Photo Credits: (Antony Theobald/Flickr)

Photo Credit: Antony Theobald/Flickr

Q: What exactly is ‘sashimi/sushi grade’ fish?

A: Fish that can be eaten raw. If in doubt, ask a fishmonger you trust.

 In the United States, the term ‘sushi grade’ is unregulated. However, many suppliers have set up their own parameters for their products, often reserving the term for their most fresh fish.[2]

Photo Credits: (Marla Showfer/Flickr)

Photo Credit: Marla Showfer/Flickr

Q: What are your thoughts on using brown rice in sushi?

A: I don’t myself like brown rice in sushi. If you worry about the calories in white rice, don’t eat sushi.

During the milling process, the germ and bran layer of brown rice are left intact, and are not removed as they are in white rice. The only layer removed is the outermost layer, the hull. Some health-conscious people often opt for brown rice because several vitamins and dietary minerals are lost in this removal process and the subsequent polishing.

Photo Credits: (Thokrates/flickr)

Photo Credit: Thokrates/flickr

Q: What’s your thought on cooking rice with ‘bamboo charcoal’?

A: I don’t understand this question. In principle the source of heating does not matter (except if the cooking pot is open and takes taste from the burning material).

Q: Sake: does it add, hide, or subtract?

A: It is a matter of taste. An old Japanese proverb says that one should not drink sake with rice (too much of a good thing). So drink sake before the sushi meal, or after.

Sake, the alcoholic rice beverage officially known as “Seishu” is defined as one of the following:

  1. Fermented from rice, rice-koji (the mold used to convert the starch in rice into fermentable sugars), and water.
  2. Fermented from rice, water, Sake-Kasu (the lees that remain after pressing Sake; these can still contain fermentable elements), rice-koji, and anything else accepted by law.
  3. Sake to which Kasu has been added.

After any of these processes, the liquid is then strained through a mesh to produce a clear beverage. [3] 

Photo Credits: (atmtx/flickr)

Photo Credit: atmtx/flickr

 

References

  1. “FDA Food Code 2009 – Chapter 3 – Food.” Fda.gov. N.p., n.d. Web. 28 Apr. 2014.
  2. Ransom, Warren. “Sushi Grade Fish.” The Sushi FAQ. N.p., n.d. Web. 28 Apr. 2014. <http://www.sushifaq.com/sushi-sashimi-info/sushi-grade-fish/>.
  3. “Sake.com: Sake Making.” Sake.com: Sake Making. N.p., n.d. Web. 28 Apr. 2014.

Elsbeth SitesAbout the author: Elsbeth Sites is pursuing her B.S. in Biology at UCLA. Her addiction to the Food Network has developed into a love of learning about the science behind food.

Read more by Elsbeth Sites