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Courtesy Mohr and AssociatesThe Mohr Digi-Test 2 computerized penetrometer measures the crispness of apples. A new version of a device that tests apples for crispness, the Mohr Digi-Test 2 computerized penetrometer, will soon hit the market.

“We’re ready to ship at the end of January or early February,” said Chuck Mohr, co-owner and principal engineer at Richland, Wash.-based Mohr and Associates.

The tester, whose prototype dates to 1999, is used mostly in research but several packing houses have also adopted them, Mohr said.

It’s good for time of picking and looking at storability,” he said. “Once you’ve met the brix level, you want the smallest deviation in your quality standard at picking. If not, it’s prone to more rapid decay. We’re able to pull an apple off the tree with a certain maturity level.”

A rod on the device plunges into an apple, and software computes the data.

"We measure the crispness between three tenths of an inch in all the way to 40% of the radius, which is where your tooth goes,” Mohr said. “If you look at the inside of the fruit, there may be 27 pounds of pressure but as it ages it drops down and can match the outside pressure, maybe 13 to 15 pounds.”

Smaller numbers inside could suggest browning.

Replacing a client’s own teeth — that is, human taste testers — is not the goal. Such testers don’t really serve the same function anyway, Mohr said.

“They are few and far between,” he said. “But you would need a lot of folks lined up because everybody votes differently. And you can’t have 500 people taste an apple.”

To keep subjectivity at bay and anticipate how taste changes in storage, the company weighs criteria like fruit pressure and crispness.

The penetrometer also tests for creep deformation and offers a quality measure. Tests generate graphic and statistical output. The MDT-2 comes with a touch screen and some features previously only available by download.

Some customers run 100,000 apples a year through the penetrometer, Mohr said. Commercial clients include Allan Bros. Inc., Naches, Wash.; and Columbia Reach Pack, Yakima, Wash.

But use is more widespread in cultivar development.

“The USDA research center has had our stuff since we first came out,” Mohr said, referring to the Agricultural Research Service Tree Fruit Research Laboratory in Wenatchee, Wash.

Research employing the device has been published in the electronic HortTechnology journal.

Apple crispness is variety-specific. Fujis have comparatively little, about 150 to 200 on Mohr’s scale. Galas and braeburns might be 300 to 400 at time of picking, and the better red delicious close to 500.

“I’ve seen Honeycrisp up in the 700 range,” he said. “But Honeycrisp doesn’t like to hang out long. If they aren’t refrigerated they can soften up and drop from 700 to 300 pretty quickly.”

The company also offers specialized probes and test routines for pears, grapes, cherries, kiwi, watermelon, tomatoes, potatoes and other commodities.