Published September 1, 2012. From Cook's Illustrated.
When our affordable favorite went kaput after less than a year, we had to wonder: How much would we need to spend for durability and a little peace of mind?
In 2009, we spent weeks test-driving 10 blenders and eventually found two machines that could easily do it all: crush ice, make frozen drinks, and blend lump-free smoothies, milkshakes, and hummus—and without damaging our eardrums. Those were the Vitamix 5200 and the KitchenAid 5-Speed Blender. We’d already been fans of the Vitamix. This Ferrari of blenders ($449), the darling of restaurant chefs, has gone unmatched in the test kitchen for years. The KitchenAid didn’t quite rival the Vitamix, but it proved itself a worthy, far more affordable ($150) alternative, so we ranked it number one. (We also tested the Blendtec Total Blender in 2009 but were not impressed; see "Upscale Blenders" under related content for details.)
But since that time, some readers and test kitchen staffers who purchased the KitchenAid reported that their machines leaked or that the jar cracked after less than a year of use. Though many of these folks were die-hard smoothie makers who used their blenders daily, this was hardly the level of durability that we thought we were signing on for. So we circled back to square one with a simple question: Is the Vitamix really the only blender that can stand up to constant, hard-core use, or might there be another, less expensive contender that can also stay the course?
To find out, we corralled nine models—everything from an affordable $40 appliance to our luxe benchmark, the Vitamix, as well as a new copy of the KitchenAid. And you can be sure that we raised the bar since the last round of testing. Hummus, crushed ice, margarita, and milkshake tests were givens, but to separate the workhorses from the wimps, every day for a month we also made smoothies in each one with fibrous frozen pineapple and stringy raw kale.
Nuts and Bolts
The losers—and there were many—were easy to pick out. Some blenders flat-out failed at ice crushing. Others sputtered their way through milkshakes and fruit smoothies. The task of demolishing kale proved the downfall of a number of machines. The best that some could do was chop the leaves into small pieces, while one lesser model completely broke down during the challenge. Only two models plowed through this and every other task without flinching.
To make sense of why these two machines did so much better than the others, we consulted Dr. Daniel J. Braunstein, senior lecturer in mechanical engineering at MIT, who explained that there are three key factors that make or break a blender’s performance: jar shape, the number and position of the blades, and motor strength. The motor spins the blades to create a vortex, which pulls the food toward the blades, then to the bottom of the jar, and back up the sides to start all over again.
That’s why flat-bottomed jars generally slowed the blending process. Their 90-degree angles impeded flow (think of the speed you can reach taking a curve, as opposed to going around a corner), whereas curvy models kept the food moving at a steady clip. Gentle tapering also helped move food to the blades.
The length of the blades and how they were configured also altered a blender’s performance; this actually mattered more than whether a jar was fitted with four or six spikes. To maximize the chance that they’d whack the food, it was crucial not only that the blades be fixed at different positions and angles but also that the gap between the blade and the jar be minimal. (This way the food couldn’t fall and get trapped at the bottom or pass by at the edges without being chopped.) This “wingspan” helped explain the velvety-smooth drinks made by the better machines (whose blades left a gap of less than ¼ inch from the jar walls) and the lumpy output of lower-ranking models, whose blades left gaps as wide as 3/4 inch from the wall.
The final piece of the puzzle: motor strength. More power behind the blades increases their contact with food and literally gives the blender the energy to face down the toughest jobs, so we weren’t altogether surprised when blenders with three of the highest wattages performed best. The top two machines also had automatic shutoffs that allowed their motors to take a breather when faced with particularly strenuous tasks instead of shifting into overdrive and potentially burning out.
Those factors helped us figure out what makes a blender work well out of the box, but we hadn’t yet addressed the KitchenAid’s Achilles’ heel: durability. Our new copy of this blender did, in fact, show signs of breaking down by the end of testing (the blade apparatus loosened and a rubber gasket popped out), so we removed it from our final rankings. We also took a closer look at the materials used to create blender jars and made an important discovery: KitchenAid manufactures its pitchers from commercial-grade polycarbonate, whereas our top two performers use Eastman Tritan™ copolyester, considered more durable and resistant to impact and the harsh combination of heat, water pressure, and dishwasher chemicals. Not unexpectedly, one of those two blenders was the Vitamix. Just as it has for years, this test kitchen stalwart proved that there’s virtually nothing it can’t handle, thanks to its long-armed, well-configured blades and souped-up (1,380-watt) motor. Its performance comes at a steep price, but its exceptional durability (not to mention seven-year warranty) makes it cheaper in the long run than a less expensive blender that needs continual replacing.
But we have a co-winner. It sports all three key blender features: long blades, each set at a different position and angle; a bowl-shaped jar; and a relatively powerful (750-watt) motor. As a result, it sailed through every test. At $200, it’s less than half the price of the Vitamix. If it proves as durable as that machine—and during the coming months we will continue to test its powers by making multiple kale smoothies in it every day—we may award it the sole top spot. We’ll keep you posted.