The Digi-Test is a new instrument for assessing the internal quality of apples. It probes deeper into the fruit than the standard Magness-Taylor firmness tester.

The Digi-Test is a new instrument for assessing the internal quality of apples. It probes deeper into the fruit than the standard Magness-Taylor firmness tester.

Labor-saving taste tester

The measure of crispness correlates with perceived eating quality.

Washington State University’s apple breeding program is using a new instrument to judge the eating quality of potential apple cultivars.
The industry’s standard instrument for measuring the internal quality of apples is the Magness-Taylor penetrometer, which punches a hole in the apple about a third of an inch deep to assess its firmness.

The Mohr Digi-Test, developed by Mohr and Associates of Richland, Washington, has a plunger that goes much deeper and measures more of the edible portion of the fruit, not just the outer layer.

Dr. Kate Evans, WSU’s apple breeder, said that apple softens from the core outwards, so a reading of the texture of the outer area of the fruit does not give the best indication of its eating quality. Another important difference between the two devices is that the Digi-Test measures crispness of the interior flesh—based on the tearing of the fruit as the probe goes through it—not just its hardness. Brandt Mohr, Mohr’s chief technologist, said the plunger could be thought of as a mechanical tooth.


For a research study, Evans compared readings from the Digi-Test with results of a sensory analysis of eating quality by a small panel of expert tasters (scientists working with the breeding program). She found a strong correlation between the Digi-Test’s crispness measurements and the sensory evaluations. The tests confirmed that ­measures of hardness are not as highly correlated to eating quality as crispness is.

Selecting for internal fruit quality is a major part of an apple-breeding program, Evans reports. WSU’s breeding program evaluates around 7,500 apples each year. Previously, sensory analysis was the preferred form of testing for crispness, but there is a limit to the number of apples that a sensory panel can score without becoming fatigued and losing accuracy.  The new instrument will reduce the need for some of the sensory analysis.

Data from the Digi-Test, which can also be used to weigh the apples, are automatically downloaded into a computer. An advantage over the Magness-Taylor penetrometer is that the instrument is robust enough to be taken out into the field to sample fruit. The data can be downloaded into a computer upon return to the lab.

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Kit for teaching pesticide safety

A fluorescent tracer kit developed for pesticide safety training can be purchased from the University of Washington’s Pacific Northwest Agricultural Safety and Health Center in Seattle. The kit is designed to be used by pesticide safety educators and farm supervisors or safety managers when teaching safe farming practices.

The tracer is a nontoxic chemical that can be used to mimic pesticide contamination on skin, clothing, and surfaces. Under normal lighting, it cannot be seen. Under a blacklight, it is visible and can reveal areas of potential exposure.

The tracer kit, which costs $175, contains a manual, instructional video, the tracer, a blacklight, and mixing, measuring, and safety materials. It contains enough tracer for 200 demonstrations. The kit can be rented for $75 a month.

For information or to purchase a kit, e-mail pnash or call (800) 330-0827.

Scorpion registered in California

The neonicotinoid insecticide Scorpion (dinotefuran) from Gowan has been registered in California for use on grapes and a range of vegetable crops. On grapes, target pests include leafhoppers, mealybugs, whiteflies, glassy-winged sharpshooter, flea beetles, the grape berry moth, thrips, phylloxera, and the brown marmorated stinkbug. The product can be applied to the soil or the vine.

Scorpion is highly soluble in water, allowing for rapid uptake and movement through the plant. Studies show that it has a different mode of action from other ­neonicotinoid pesticides.