The mystery of the splattering tomato sauce

February 13, 2012

עברית: בסיס רוטב עגבניות (לתבשיל חציל)

The nuisance:

Please indulge me and imagine this situation: You’re past the restaurant stage of dating and have invited the object of your desire to dinner in your own home, which can turn even the messiest slob into a temporary Stepford wife. Everything is neat and clean and the bedroom smells like roses, so now is the time to proceed to the kitchen to actually cook something. Oh dear, cooking. Well, the simplest dish would be a nice bowl of pasta for each with a spicy tomato sauce on top. What can possibly go wrong making this? Well… boiling the sauce, you’ll most likely end up with a kitchen that looks like they just filmed Chain saw massacre XII – the Splattering in there.

La Tomatina (25.08.2010) - Spain, Buñol 23

…well, either that, or a tomato-themed orgy

Why, oh why on earth does tomato sauce do this when all other sauces are so tame and benign by comparison? It almost seems like the delicious red vegetable was specifically designed to lament its passing by marking the murderer with smears of its innards. Actually… that’s not so far off.

The explanation:

Cohesion and viscoelasticity. Where the hot metal at the bottom of the pot meets liquid, gas will be expelled and starts pushing upwards, but the more the molecules of the fluid above stick together, the harder it is to push through, until the gas bubble at the bottom finally gets big enough to break free, rocketing upwards and taking a bunch of sauce with it. Now, tomatoes contain pectin, which is a very large, branched molecule that stabilizes the cell walls. During ripening, two enzymes break down those walls, making the tomato soft and squishy.

18th century illustration of perjurer John Wal...

….and therefore, ideal people pelting material

Those broken down pectins act like an emulsifier making a thick gel out of the tomato pulp. Because of this, the cohesion of the sauce keeps the bubble trapped for a longer time than comparable fluids that don’t bond together as much, and also form bigger splatters that also tend to stick on every surface they meet.

The solution?

Constant, quick stirring provides an outlet for the gas bubbles. This means investing some elbow grease in the cooking process, but it still beats slaving away while cleaning. At any rate, your date will probably impressed if you use rocket science and chemistry to explain the mess in your kitchen. Or you could take them out to a restaurant.


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