I had a few questions about measuring modernist ingredients. I see a lot of the recipes use a percent sign, like "Xanthan Gum, 0.3%" what does that mean? Also, why are most of the ingredients listed by weight and not tablespoons or cups? And how exact do I have to be when measuring?
Great questions Luther! I'll tackle them one at a time
Many of the ingredients will specify the ratio they should be used in as a percent because it is a great way to help people when they are creating their own recipes. All the percents refer to the ratio between the weights of the liquid ingredients and the modernist ingredients.
For example, an agar recipe might say to add 2% agar. The 2% means that the weight of the agar should be 2% of the weight of the liquid it is being added to. So if you had 300 grams of fruit juice you would add 6 grams of agar to it, or 300 x 0.02.
Knowing those percents / ratios allows people who tweak the recipe or create their own recipes to achieve similar results.
There are two contradictory thoughts about modernist cooking and using some of the very powerful ingredients.
The first thought is that everything must be very precisely measured and the recipes must be followed to the letter.
The second thought is that ingredients from different companies will have different strengths and the quantities may have to be adjusted, especially if the recipe doesn't specify a specific brand.
Both of these statements are true and come into play depending on what you are trying to accomplish.
However, this is nothing new since both of these statements are true for traditional cooking as well. Unbleached flour from King Arthur will thicken gravy, make cakes, and form pie crusts differently than Gold Medal unbleached flour, much less their Gold Medal cake flour. A recipe calling for a "large tomato" leaves a lot of room for what size that actually is.
As home cooks we have learned to live with those differences and accept that our dish might not turn out exactly the same as the dish from the recipe, and no one will notice. For chefs, however, reproducing the exact same dish is of the utmost importance so these nuances really come into play.
I think because modernist cooking is mainly being practiced in restaurants by talented chefs there has been an emphasis on exact measurements that is very intimidating to the home cook. While the exactness is required in restaurant kitchens, home cooks can afford to be much looser.
Yes, you probably need a scale to measure grams, but this is mainly because the quantities are so small. I could adapt the recipes to call for 1/32 of a teaspoon, but most home cooks wouldn't have one. This makes measuring by weight much more effective and practical.
Also, since the ingredients interact with the particles in each other, the volume begins to become less important than the mass, expressed by weight.
Many of the ingredients are also powders and can have very different volumes based on how they have been stored. Michael Ruhlman pointed out that a cup of flour can weigh between 4 and 6 ounces, a 50% difference, depending on how packed it is. Even the humidity can affect the weight of flour and other powders.
All of these reasons highlight why we use scales and weight measurements instead of volume measurements. Plus, there's no measuring cups to clean!
Remember though, just because you have precision at your fingertips doesn't mean you have to obsess over it. All of the recipes provide gram measurements for most ingredients, but use common sense when measuring them. If you are within 1-2% of the correct weight of any ingredient then it should be fine. For 500 grams of water, about 2 cups, that is a 5 to 10 gram difference. For 3.2 grams of agar that is a 0.03 to 0.06 gram swing.
To someone not familiar with using a scale it can be a little intimidating until you use it once or twice. The main concept of using the scale is learning to "tare" or "zero" the scale. All digital scales will have a "tare" / "zero" button. What this does is reset the weight to zero.
This allows you to measure all the ingredients in the same bowl. You simply turn on the scale and place the bowl on it. Hit the tare button so it resets to zero. Add the next ingredient, then tare it to zero again. Repeat for all the ingredients.
You will most likely have to use a larger scale for the liquids or main ingredients and a gram scale for the modernist ingredients.
I hope this helps out. Thanks and happy cooking!