We've all been on the receiving end of a ketchup malfunction — slap the bottle too hard and it splatters all over the plate; treat it gently and it separates into red sludge and an unappetizing clear liquid ooze. Thankfully, though, research has finally determined how to get ketchup out of a bottle without the mess. Let's hear it for science!
Perhaps unsurprisingly, it seems to be a matter of physics. The excellent tips for freeing the sticky tomato-based condiment from its poorly designed glass bottle come courtesy of Dr. Anthony Stickland, a food researcher at the University of Melbourne. The main issue preventing that tasty sauce from reaching your burger, Strickland points out, is not the bottle's small opening, but the physical makeup of the ketchup itself.
Ketchup is a more complicated mixture than we give it credit for. Like mayo, paint, or toothpaste, Ketchup is a "yield stress fluid," meaning that it does not respond to force like a normal liquid. Instead, the sauce is comprised of tomato pulp particles suspended in liquid; these solid particles form a continuous network, making ketchup strong and resistant to motion. "If you tilt a bottle of water, the water flows out because it is a liquid. But tomato sauce prefers to be in the bottle because it is technically a solid, not a liquid," Dr. Stickland tells the University of Melbourne's research site, Pursuit.
To get the sauce to flow out of the bottle, you must overcome the yield stress by using proportional force. Ketchup, like many other soft solid condiments, defies Newton's the law of viscosity (perhaps one of the reasons why it's so frustrating), and will not move at a steady rate proportional to the force applied. A good whack on the bottle may start the flow, but depending on how much ketchup is in the bottle and the force of the slap, it could also result in a soggy red hotdog.
To overcome these ketchup pitfalls, and keep your next BBQ from looking like a crime scene, Dr. Strickland has three main pointers:
1. Tighten The Lid And Shake The Bottle
Shaking the sticky tomato ichor redistributes the solid particles evenly throughout the bottle and dislodges dried out particles that could clog the neck of the bottle. Separation occurs naturally in ketchup, but nobody wants icky tomato water on their fries and the rest of the solid stuff staunchly left in the bottle.
2. Turn The Bottle Upside Down With The Cap Still On
In order to get the ketchup to the neck of the bottle, tilt the bottle upside down and give it a few taps. If you're getting down to the dregs, this step may take a little more effort. "If there’s not much left in the bottle, you may need a strong whack to dislodge tomato sauce from the bottom," Strickland warns. "Turn the bottle upside down (still with the lid on) and thrust downward at high speeds, accelerating both the ketchup and the bottle. Swiftly stopping the bottle should slump the sauce into the neck.” It's physics!
3. Remove The Cap And Gently Pour
Now comes the final move in the delicate dance of coaxing ketchup from its glass shell. "With the bottle upright, remove the lid and start to tilt the bottle, aiming at the desired location. Increase the angle until sauce begins to flow," Strickland recommends. "If it does not flow once the bottle is almost upside down, there is not enough weight of sauce left to induce flow. This is where some sort of encouragement, like tapping, slapping, or whacking, is required." This pivotal moment separates the pro from the novice: Apply too much force and you're scraping the red stuff off your hands, but apply too little and the tangy sauce stays in the bottle.
Remember, though: If all else fails, there's no shame in poking the red stuff with a knife or buying your condiments in plastic squeeze bottles.