Jesus walked on water. (And so can you!)

Take 45 grams of starch powder and mix in 25 ml of water to create a gooey paste. This sludgy substance is also known as “Oobleck.” You’ll notice: the starch doesn’t dissolve, it forms a suspension. We call this a “dilatant fluid.” Like quicksand. If you gently rest your hand on the surface, it sinks straight to the bottom. But when you apply sudden force, the viscosity increases. You can strike it with a flat hand, or even a hammer, and it’ll feel like granite.

If you’re pumping a starch-based liquid, this behavior is something you absolutely have to take into account. Any layer of starch left behind in the pump housing can cause major issues. When the pump kicks back in, the impeller might crack under the sudden resistance. Meat dough - a blend of meat proteins with about 10% starch and roughly 55% moisture - is another notorious culprit in the food industry. Once the mixer is turned off, what was once a smooth, pliable mixture slowly sets like concrete. Restarting the mixer takes an enormous amount of force to get things moving again. This is what we call a pseudoplastic fluid: the more force you apply, the thinner it gets. Paddle blades often break off the shaft. Or worse: the entire shaft breaks.

When it comes to processing raw materials in the food industry, rheological properties, or in plain terms, viscosity properties, are crucial parameters in machine design. If you want your equipment to stay intact, the safest bet is to just stick with water.

But if you'd like to walk on water safely, multiply the quantities in the recipe above by 10,000 and fill up a paddling pool. Don’t believe me? Just search “Oobleck walking on water” and you’ll find countless wild videos of people doing just that; walking, playing football, even breakdancing on water. The phenomenon was described over 2,000 years ago… Could it be he started with a bit of starch paste too?

IJsbrand Velzeboer
Curative food technologist