Posts Tagged ‘density’

Volume-to-weight calculator for the kitchen

Thursday, January 23rd, 2014

glasbake-measuring-cup

Vintage Glasbake Measuring Cup by Gerrilynn Nunley

Despite the fact that the U.S. Metric Association have advocated metrication for nearly 100 years, many cookbooks still use US customary weights and volume measures. When following a recipe calling for teaspoons, tablespoons, fluid ounces, cups, pints, quarts or even gallons, I’ve often found myself using conversion websites such as Convert-me, picking ingredients from a list and entering the amount and unit. This works OK for single ingredients, but is less practical when converting a complete recipe. I therefore made a calculator to convert volumetric units to grams based on densities of a range of common ingredients. It has greatly simplified the task for me, and perhaps you’ll find it useful as well?

Download calculator (more…)

Ten tips for practical molecular gastronomy, part 9

Saturday, May 31st, 2008

9. Keep a written record of what you do!

Wouldn’t it be a pity if you couldn’t recreate that perfect concoction you made last week, simply because you forgot how you did it? Last year I made a vegetable soup to which I added garam masala and pepper. I was cooking ad lib, adding a little of this and that without taking notes… Which is annoying, because it turned out very nice! It had a remarkable aftertaste which gave me a somewhat dry feeling on the back of the tongue and it reminded me of mangoes. Even immediately after the meal I wasn’t able to recall all the ingredients.

As an undergraduate student I took an organic chemistry lab course, and I remember we were told not to use post it notes or small pieces of paper for taking notes. Everything should be recorded in a proper journal or – if necessary – small note books. Having finished my Ph.D. a couple of years later, I can only testify to this. Everything you do – be it in the lab or in the kitchen – should be recorded immediately in a journal. It’s amazing how something that was obvious one day, slips your mind a week or month later.

There is a wonderful Donald Duck story by Volker Reiche entitled “The soul of science” (the original appeared in 1981 in the Dutch Donald Duck magazine). At a point “Professor Duck”, who actually works as a janitor in a lab, utters the words “Careful notes are the soul of science” as he is caught experimenting. This is true also for the kitchen and experimental cooking. A German translation of the story was reprinted in the article “Das Leiden des cand. chem. Donald Duck” (open access) in case you want to read the whole story.


Careful notes are also the soul of kitchen science!

When taking notes it’s essential that you are able to re-cook the dish yourself. But if no one else is, the notes are of limited value. The biggest source of uncertainty in the kitchen is the widespread use of volume for measuring powders. This can best be illustrated by the question: How much does a cup of flour weigh?

I bumped into this when I began baking no-knead bread (recipe). I converted the recipe to metric units using an online calculator, but the no-knead bread wasn’t a huge success. The problem was that there is no simple answer to the question “How much does a cup of flour weigh?”. Cooking conversion online states that a cup of all-purpose flour weighs 99 g. King Arthur Mills claim that all their flours weigh 113 g/cup. USDA states 125 g/cup and Gold Medal 130 g/cup. Some cookbooks have settled at 140 g/cup (apparently because this is about half way between a loosely and densly packed cup) and if the flour is hard packed you can reach 160 g/cup. In other words – when following a recipe you would need to know how the volume of flour was measured in order to use exactly the same amount of flour. Some recipes call for “spoon and level” or “scoop and level”, but many do not include any information about this.

My recommendation is to weigh all dry ingredients (and preferably also the wet ingredients). A normal digital kitchen scale typically has a resolution of 1 g with an accuracy of +/- 5 g and they are quite affordable. Weighing liquids is also far more accurate than the average volume measurement in the kitchen. If the scale has a “tara” function it’s also much faster as you can zero the display after each ingredient you add. It shouldn’t come as a surprise that I’m not the only chemist advocating weight measurements in kitchen. And it’s not difficult finding other sites in favor of weight measurements either.

It therefore puzzles me why recipes that call for the following are still so abundant:

1 pack of instant yeast
1 envelope unflavored gelatin
1 gelatin sheet (see comment #4-5)
1 sachet powdered pectin
1 tablespoon liquid pectin
1 stick of butter
… and the list goes on

The only exception to the general advice on weighing ingredients is when very small quantities are used. This could be spices, food coloring or hydrocolloids. With normal kitchen scales, you’ll be better of using volume measurements for amounts less than 5 g (equal to a teaspoon if measuring water). Otherweise it’s worthwhile mentioning that scales with a 0.1 g and 0.01 g readout are getting cheaper and cheaper.

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There is a summary of the “10 tips for practical molecular gastronomy” posts. The collection of books (favorite, molecular gastronomy, aroma/taste, reference/technique, food chemistry) and links (people/chefs/blogs, webresources, institutions, articles and audio/video) at khymos.org might also be of interest.

Help needed with densities of hydrocolloids

Wednesday, April 30th, 2008


Photo by Mel B via flickr.com (CC).

Measuring powders by volume has serious limitations (more on this later in an up-coming post), but one great advantage is that for small quantities going by volume can sometimes be more accurate than weighing them. At least when you work in a kitchen and don’t have access to professional lab scales. When a scale shows 0.1 g, the true weight could be anywere from 0.05-0.149 g due to rounding (that’s ± 50%!). Not to mention the fact that cheap balances aren’t always very accurate for such small amounts, even though they feature a 0.1 g resolution.

I’m currently working on a major revision of the collection of hydrocolloid recipes. One thing I would like to include is a table with densities of the hydrocolloids and chemicals used. When the densities are known, it’s possible to give some rough advice for what volume to use (this on-line conversion calculator has the densities of many common ingredients). This could ease small scale preparations. It will also make it easier to calculate the percentage of hydrocolloid used in recipes where the amount is given by volume. I’ve measured the hydrocolloids I have at hand, but I need your help to fill out the table and repeat the measurements I’ve done. With enough measurements I could also do some statistics and make a plot. I’m also interested to see if there is much variation between different brands.

How to determine the density:

  1. Find a suitable measuring spoon, cup, shot glass, container – whatever you have – with a volume of at least 10 mL (I used one of about 30 mL).
  2. Put the empty container on the balance and use the tara function.
  3. Fill completely with water and weigh again. The difference gives you the exact volume (for water 1 g = 1 mL).
  4. Dry the container, put it on the balance and use the tara function.
  5. Spoon the hydrocolloid into the container, tap the side gently once or twice with the spoon and level off.
  6. Weigh the container again and write down the mass of the hydrocolloid.
  7. To calculate the density of the hydrocolloid, divide the mass by the volume you obtained for your container. This gives you the density of the hydrocolloid with units g/mL.

Repeat steps 4-7 for each hydrocolloid you have at hand. I would very much appreciate if you email your results directly to me at webmaster (@) khymos (.) org. Please include the volume you measured (larger volume means more accurate measurement) and which brand you used. It will be interesting to see if the brands differ a lot.

I should add one coment about the products from texturePro: this picture indicates that all (?!!) the texturePro hydrocolloids are mixed with maltodextrin (please correct me if I’m wrong – it could be that this only applies to the cocktailPro kit). And I think the same is the case for several of the Sosa products. This increases the volume and eases the use of a measuring spoon (which comes with every texturePro kit), but unless the exact proportion of hydrocolloid to maltodextrin is known, following other recipes than the onces included with the kit is more or less impossible. Let me know if you have further details on the hydrocolloid/maltodextrin ratio in texturePro or Sosa products.

In advance: Thank you very much for your help!