Sunday, January 23, 2011

The Age of Shrimp

During an interview on To the Best of Our Knowledge, Ellen Ruppel Shell, the author of "Cheap: The High Cost of Discount Culture," dropped an amazing fact: we eat more shrimp today in the U.S. than tuna fish. It was one of those "wow" statistics that I had to check out for myself.

Fortunately, the U.S. Census Bureau released a new Statistical Abstract (via Marion Nestle's must-read Food Politics blog) a few weeks ago and I quickly found what I was looking for in Table 893, "Supply of Selected Fishery Items" (PDF, Excel) on the Fisheries, Aquaculture page.

The tuna and shrimp data are shown in the first figure below: while per capita canned tuna availability has remained relatively flat over the last few decades, shrimp availability has risen sharply, especially since the mid-1990s.  (Note: "availability" is a USDA term that is an estimate of "food supplies moving from production through marketing channels for domestic consumption." This USDA page has a lot about the concept of availability)

U.S. Per Capita Availability of Canned Tuna and Shrimp.  Data from Table 893 of The 2011 Statistical Abstract and U.S. Census Bureau (details at the bottom of the post).

So what happened? Globalization and aquaculture teamed up to make farmed shrimp far more plentiful, lowered their production cost significantly, and managed to bring the product to stores and restaurants in great quantity.  

The last few decades have seen great advances in the art and science of moving large amounts of perishable goods around the world, thanks in part to refrigerated cargo containers, air freight, and improvements in logistics and distribution.  At the same time, aquaculture experts have figured out how to grow shrimp in coastal and inland farms, while the rest of the supply chain — processing, transportation, distribution, marketing — has fallen into place.

Almost all of the increase in availability is because of imports, as the next figure indicates.  The blue line at the top shows the total imports, while the dotted lines (orange, green, purple) show the imports by sector. The red line running from the year 2000 to 2009 is the domestic catch, and it's been steady during that time. 

Per Capita Supply of Shrimp, Imports and Domestic Landings.  U.S. landings data from Fisheries Statistics Division (NOAA), imports data from USDA Economic Research Service (details at the bottom of the post).

The next figure shows import totals for the countries that make up roughly the top two-thirds of the imports.  Thailand really stands out with rapid growth from 50 million pounds in 1990 to over 400 million in 2009.
U.S. Shrimp Imports from the Top Six Countries.  Data from USDA Economic Research Service (details at the bottom of the post).

Shrimp is a messy subject because there are several varieties and several ways of capturing or farming them.   The Shrimp page from Monterey Bay Aquarium's Seafood Watch has 13 entries for shrimp and prawns, with ratings of "best choice," "good alternative" and "avoid" scattered across the list.  If you click on an individual entry, your browser will reveal Seafood Watch's explanation for its rating of that entry.

Most farmed shrimp are big trouble, as they are raised in "Aqua-CAFOs" that closely resemble cattle or hog "concentrated animal feeding operations" with all kinds of chemicals and antibiotics required to keep the creatures alive. In addition, the aquaculture areas are created by destroying mangrove forests, which are biologically rich coastal areas that providing habitat for a wide variety of creatures, including juvenile fish — hence, mangroves are often called "nurseries of the seas."

However, some farms are improving their practices.  On the Seafood Watch page about shrimp, imported farmed shrimp raised in "fully recirculating systems" are given the "Good Alternative" rating because these farms — which comprise only about 25% of the total shrimp farms in Thailand — are fully-enclosed ponds that don't release pollutants to open water. Some retailers like Walmart are using third-party certification agencies like Aquaculture Certification Council to ensure that their suppliers are using good practices. However, there are concerns that these certifiers aren't independent enough.  (My review of “Bottomfeeder” by Taras Grescoe at the Ethicurean has a bit more about how shrimp farming can be disaster for ecosystems and the people who live near shrimp farms.)

Some are making advances with smaller-scale recirculating aquaculture systems, like the operator of the Shrimp Farm Market in mid-Michigan.  Michigan, with it's cold winters, isn't exactly the best habitat for shrimp, but this shrimp farmer is getting around the bad weather by creating his own through use of an enclosed system (Edible WOW magazine had a short story about his farm, available as a PDF).  

Wild shrimp aren't without issues, the biggest being "bycatch". The Seafood Watch page on wild-caught imported shrimp notes that "Shrimp trawling has the highest bycatch of any commercial fishery – for every pound of shrimp hauled in, three to 15 pounds of unwanted animals die in the process" (click on the link for wild-caught imported shrimp on the Seafood Watch page for details).  More recently, the explosion of the Deepwater Horizon oil rig brought worries about chemical contamination of shrimp caught in the Gulf of Mexico.

Notes on sources:

First figure: Availability = domestic supply minus exports plus imports. The shrimp weight is for heads-off creatures, the tuna weight is canned weight. Per capita results were obtained using U.S. population figures from an Excel spreadsheet in the documentation on food availability at the USDA, which covers U.S. residents plus Armed Forces overseas.

Second and third figures: import data by country and form of import are from USDA's Economic Research Service. U.S. landings are from NOAA's Fisheries Statistics Division,(PDF).

The figures were created using the Calc application in the free software suite Open Office. It's a pretty good replacement for Excel, but I'm still learning to deal with its quirks. 

Random link from the archive: It's time for a political do-not-mail list

Sunday, January 09, 2011

The Yogurt Routine

Of all the things I tried in my kitchen in 2010, learning to make yogurt was by far the most valuable. I had tried once or twice in previous years, with rather poor results, but then in early 2010 I figured it out.  Euclidarms* wrote a long piece about his yogurt technique at La Vida Locavore that really opened my eyes, and soon thereafter Cherie Picked helped me a bit more.  By the middle of 2010 I had developed a system that worked for me and settled into a loose routine of home yogurt making.

I'm probably saving a good deal of money (perhaps $1 per quart), but what's more important to me is that I'm avoiding a good deal of plastic (like the tubs in the manipulated photo above). Instead of bringing home a new plastic container of yogurt every week, I buy milk in a reusable glass bottle or a compostable paper carton, thus making a big dent in plastic use (and of the piles of plastic in my container cupboard). In addition, it's one more thing I'm doing myself, which is often a good feeling.

Heat, Cool, Mix, Wait
Making yogurt at home is surprisingly easy: heat, cool, mix and wait. In more detail:
  • Heat: heat milk in a saucepan over gentle heat to about 190 °F (88 °C), stirring frequently. Heating the milk modifies the whey proteins, which will give you a finer, more compact curd. (For more on yogurt science, see a column by Harold McGee in the New York Times.)
  • Cool: let the milk cool to 120 °F (49 °C)
  • Mix: mix in some yogurt and pour the mixture into a clean pre-warmed container. Wrap the container with towels.
  • Wait: Let the container sit in a warm place for a few hours until it sets. 

That's the basic outline, and here are many more of the details woven into the system that I settled on. Note that what works for me might not work for you and that there are many ways of making yogurt at home, so another approach might be ideal for you.
  1. A few hours before heating the milk, I put a few tablespoons of yogurt from the previous batch into a room-temperature glass bowl and let it sit so that the cultures can reactivate and be ready for their big cultural event 
  2. When it is time to start the heating process.  I save about a half-cup of milk for the week's tea, and pour the rest into a saucepan that is set on top of a heat diffuser (something like this).  I turn the heat to medium.
  3. Stirring frequently, I let the milk get to about 190 °F (88 °C), then turn off the heat.
  4. After turning off the heat, I put some hot water into a very clean one-quart canning jar so the jar will be warm when it receives the milk-yogurt mixture (I only use jars that have gone through an automatic dishwasher cycle, but if I didn't have one available, I'd rinse the jar with boiling water to thoroughly disinfect the jar).
  5. I let the milk cool to about 120 °F (49 °C).
  6. I add a small amount of warm milk to the yogurt to temper it (thus avoiding thermal shock), then add the rest of the warm milk and whisk everything together.  Next, I pour the warm water out of the jar, pour the milk-yogurt mixture into the warm jar, give it one last stir, and screw on a lid. 
  7. Working quickly, I wrap the jar in two or three layers of kitchen towel, using rubber bands to hold each layer in place.
  8. I put the wrapped jar in a warm place — my oven (which has a pilot light) and prop the door partially open to avoid overheating (thanks to an absurdly large pilot light, the temperature of the oven with the door closed is far too hot to yogurt making, perhaps 140-150 °F).
  9. Four hours later (more or less), I remove the wrapped jar, unwrap it, and put the jar into the refrigerator.
Fitting it into the Rat Race
The process I just listed works great on weekends when I have a 4 1/2 hour block, but on weekdays it can be hard to get everything done between the time I get home and go to sleep.  So I've devised a slightly different process for reactivating the culture. I bring the last batch of yogurt and a glass bowl to work, putting the yogurt in the refrigerator and leaving the bowl at room temperature.  In the mid-afternoon, I put a few tablespoons of yogurt into the bowl and leave it at room temperature. This way, the culture has a chance to get reactivated during the end of the workday and is ready when I start the process at 6:30 or 7 PM at home. 

Additional Notes and a Question
Many months after getting into a routine, I noticed that Paula Wolfert's "The Cooking of the Eastern Mediterranean" has an appendix about yogurt and a recipe for making it at home. Wolfert writes that the most prized yogurt in the Eastern Mediterranean is made from buffalo's or sheep's milk because of the high butterfat content. With regard to home culturing, she relates an old saying about the culturing process: "the quicker the sweeter." In other words, the faster you can make the yogurt set, the sweeter it will taste, so some yogurt makers pour the warm milk-yogurt mixture into small jars for culturing.  At 100 F, a batch of yogurt will jell in about 6 hours. At a lower temperature, it could take as long as 24 hours and give you a much tarter result.

Writer and editor Jennifer Jeffrey wrote about a clever way of managing yogurt culturing temperature with a hacked slow-cooker. By installing a dimmer switch in the power cord, she could control the amount of energy reaching the cooker's heating elements, thus controlling the temperature of the water bath. (If you are going to hack commercial appliances, be sure you know what you are doing and follow good safety practices!)

Finally, a question for those who make yogurt at home:  wouldn't it make a lot of sense to use the microwave to heat the milk?  Microwave heating is even and gentle, therefore seeming less likely to scorch the milk than a pot on the stove. 

*euclidarms is the La Vida Locavore username of Ed Bruske, a.k.a. "the slow cook."  Bruske is a writer who has written some amazing pieces on school lunch in Washington, D.C., Berkeley, and Boulder. To research his articles, he doesn't just look around and talk to people, he actually works in the kitchen. You can find his multi-part articles at the Slow Cook (look to the right column).

Random link from the archive: Tempura at Ten-Ichi in Tokyo

Cross posted at La Vida Locavore