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What makes fish smell “fishy”?

By Ann L.

If you have ever caught fresh fish, you know that it doesn’t have a particularly strong odor, maybe a hint of ocean or lake water.But sometimes the fish you get from the store can have a pungent “fishy” odor.What causes that smell?

The answer has to do with some interesting physiology unique to sea creatures.Water in the open ocean is about 3% salt by weight, but the optimal levels of dissolved minerals inside an animal cell is less than 1%.In order to maintain fluid balance, ocean creatures must fill their cells with amino acids and amines to counter the saltiness of seawater. Ocean fish tend to rely on trimethylamine oxide (TMAO) for this purpose.

The problem is that when fish are killed, bacteria and fish enzymes convert TMAO into trimethylamine (TMA), which gives off the characteristic “fishy” odor.This smell can be reduced in two ways.TMA on the surface of the fish can be rinsed off with tap water.Treating the fish with acidic ingredients such as lemon, vinegar, or tomato can also cause TMA to bind to water and become less volatile.Thus the odor compounds do not reach the nose.

Freshwater fish generally do not accumulate TMAO because their environment is less salty than their cells.As a result their flesh tends to be milder, and they do not get as “fishy” as ocean fish.However, freshwater fish sometimes suffer from an unpleasant “muddy” aroma.This often occurs in bottom-feeders such as catfish, and is caused by two compounds produced by blue-green algae (geosmin and methylisoborneol).These chemicals concentrate in the skin and dark muscle tissue of the fish.Acidic conditions will cause these compounds to break down, so there is good reason for the inclusion of acidic ingredients in traditional recipes.

Next time you have fish be sure to give it a squeeze of lemon or a splash of vinegar!

Reference: McGee, Harold.On Food and Cooking: The Science and Lore of the Kitchen.New York: Scribner, 2004.

By: Laura S.

I am currently training for my second marathon in my adult life, and while the aches and pains feel the same as last year, and as the mileage starts to creep up it feels like deja vu- one minor detail has changed: this year I am running the marathon as a vegetarian.

Vegetarian endurance athletes have become quite a trend in the last couple of years. Some noteworthy endurance athletes include Brendon Brazier (vegan ironman), Rich Roll (vegan ultra ironman), Robert Cheeke (vegan body builder), and Michael Arnstein (fruitarian ultra runner); just to name a few.

Giving up meat during this marathon training means I will be missing out on complete proteins and key amino acids from my diet. These amino acids are also called limiting amino acids and they are: lysine, threonine, methionine, and tryptophan. Limiting amino acids are found in the shortest supply from incomplete proteins. Incomplete proteins are those found in plant food sources and geletin.

The most frequently asked question I get asked when becoming a vegetarian involved getting enough protein. While I do not eat meat, fish, or dairy (except for yogurt) I get plenty of protein in my diet by using protein complementation.

Protein complementation is the most efficient way to get all 9 amino acids into a vegetarian’s diet. Protein complementation is when you combine two vegetable proteins (legumes and grains for an example) to get all 9 amino acids that are essential for your body. The breakdown of protein complementation goes like this:

 

Food Limited Amino Acid Complement
Beans Methionie Grains, nuts, seeds
Grains Lysine, threonine Legumes
Nuts/seeds Lysine Legumes
Vegetables Methionine Grains, nuts, seeds
Corn Tryptophan, lysine Legumes

By combining vegetarian protein sources you can ensure that you are getting all 9 amino acids. Protein complementation does not have to be done at the same meal. If you ate beans for lunch and then had some raw almonds for a snack later, you would be adding the methionine that you had missed out on during lunch.

A vegetarian diet, if planned correctly, can provide you with all of the vitamins, minerals, and amino acids the body needs.