Working at the intersection of food and science, we come across a LOT of scientific jargon and terminology, from chemical processes (see: nixtamalization), to physical phenomena, to species names (see: Aspergillus oryzae). We’ll be sharing many of these fun words with you in this ongoing series, Word of the Week. Get ready to impress at your next cocktail party.
You open the ketchup bottle and turn it upside-down over your fries. Before you can even give it the whack or squeeze it needs to get the stuff flowing, a thin stream of orange water runs out and dampens your meal.
“SYNERESIS!” you curse.
Syneresis (after finding varying pronunciations across dictionaries and consulting experts, we settled on “sinnerRHEsus”) is the technical term for what chefs call “weeping”—when a gel that’s holding onto liquid in a food lets go of some of that liquid. Yes, ketchup is a gel: pectin from the cooked tomatoes stiffens it, and many commercial ketchups have other gelling ingredients, such as xanthan gum, added as well.
Water pooling on top of yogurt? That’s syneresis. So is a watery runoff from pudding, juices flowing from cooked steak, and frost forming on ice cream. It can be caused by a variety of changes, depending on the food and the circumstance. Yogurt’s protein gel and ketchup’s pectin gel are naturally both fairly weak (otherwise, they’d be less delightful to eat). As they sit, the mesh structure of the gel tends to contract a bit, reducing its capacity to hold water and pushing some out as a result.
Some gels are looser when they’re hot, like the starch gels that hold together pie filling and some puddings. Then, when they cool, they tighten up and lose some of their capacity to trap water. Protein gels, like those in meat and eggs, tend to contract when they’re heated instead, squeezing out water, and becoming unpleasantly dry if they’re overcooked.
With many preparations, hydrocolloid ingredients can be added to make a firmer gel that’s less prone to syneresis. However, that changes the texture of the food as well, so sometimes it’s better to put up with a little weeping than try to serve an over-firmed scoopable ketchup or a bouncy yogurt.
Not all syneresis is undesirable, though. One clever culinary technique that takes advantage of the way gels hold and release water is agar clarification. First you add agar to a stock or juice to turn it into a gel. Then you deliberately break up the gel with a whisk, and let the liquid drain out through a strainer. When it does, all the tiny solid particles that were in the juice or stock stay behind in the agar, so the liquid that went in cloudy comes out perfectly clear. Syneresis to the rescue.
Graphics by Jay Layman.