Saturday, June 23, 2012

In which my kitchen scale helps me reduce a sauce

A scale is an essential tool in my kitchen.  It makes ingredient measurement easier, more accurate (especially for flour), and less messy (especially for oily and sticky ingredients).  Last weekend, I found another use: monitoring reductions.

I was making the utterly delicious "Spicy Chipotle Toltec Barbeque Glaze" from Coyote's Pantry (by Mark Miller, Mark Kiffin and John Harrison).  Instead inaccurately 'eye-balling' the liquid level, or dangerously pouring hot liquid into a measuring cup (complete with inevitable spills and drips), I was able to use my scale to monitor the progress of the reduction.

It takes a bit of preparation, so get out your scale, a pen and paper, and a potholder or trivet and go through the following steps:
  1. Switch your scale to grams, it will make the math much easier.
  2. Put the empty pot you plan to use on the scale, press the tare button.
  3. Pour in the liquid. Write down the weight of the added liquid.  Call this L.
  4. Calculate weight loss needed.  If you are aiming for a 50% reduction, that's L / 2.
  5. Remove the pot from the scale and press the tare button.
  6. Now you want to find the target weight.  Since you'll be dealing with a hot pot, place a pot holder or trivet on the scale.  Do not press the tare button.
  7. Put pot with liquid on the pot holder and scale.  Write down this weight (the total weight of the pot holder, pot, and unreduced liquid).  Call this W.
  8. The target weight is then T = W - L / 2.
  9. During the reduction process, periodically weigh the pot.  When it reaches target, you are done. Important:  Some scales turn off automatically, and perform an auto-tare upon restart.  If your scale does that, you'll need to take the pot holder off of the scale before restarting it, then put the pot holder and pot on the scale to get the current weight.  
For example, let's say that my pot weighs 750 grams and I have 250 grams of liquid that I want to reduce by 50% (L = 250).  If the pot holder weighs 100 grams, the beginning weight (W) will be 1100 grams (750 + 250 + 100).  The target will then be 1100 - 125 (W - L / 2), or 975 grams. 

Sticklers for accuracy will note a flaw in this approach, namely that it assumes constant density throughout the reduction, something that is probably not correct because the evaporated material will be mostly water (and alcohol if wine, beer or spirits are in the sauce), while the material remaining behind will be a collection of lower density liquids like fats and higher density materials like the solids.  But since most reductions are approximate, it's close enough.

Image credit and details:  One of the many wonders at the National Gallery of Art in Washington, D.C., Johannes Vermeer's "Woman Holding a Balance" (c. 1664).  The image was downloaded from the NGA Images database at the National Gallery of Art, "a repository of digital images of the collections of the National Gallery of Art. ...  More than 20,000 open access digital images up to 3000 pixels each are available free of charge for download and use. NGA Images is designed to facilitate learning, enrichment, enjoyment, and exploration."

Random link from the archive: Soy Trilogy

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