Device Measures Apple’s Crispness

A unique taste-testing device offers the U.S. apple market the chance to develop apple varieties with great crispness, a prized characteristic for consumers.

A crisp apple makes for a delicious snack.

A crisp apple makes for a delicious snack. Kim Goh

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Richland, Washington – Everybody knows a good apple when they bite into one, and it turns out that an apple's crispness is rated among its most important qualities by consumers. However, despite the size and economic importance of the U.S. apple market, an estimated 231 million bushels in 2009, the industry has not established a reliable automated method for measuring fruit crispness, instead relying primarily on taste-testing that is both subjective and labor-intensive. Now, new research confirming the capabilities of a unique texture-testing instrument suggests this is about to change.

Researchers with the Washington State University Apple Breeding Program in Pullman, led by Associate Professor Kate Evans, compared the sensory attributes of a variety of apple selections, rated by an expert taste-testing panel, with measurements obtained by the Mohr MDT-1 penetrometer.

According to their report published in the December 2010 issue of HortTechnology, the researchers found a significant correlation between the MDT-1's Crispness (Cn) measurements and the apples' crispness and overall eating quality. The MDT-1 is a next-generation replacement for the hand-operated Magness-Taylor (MT) penetrometer the industry has relied on for decades to measure fruit firmness, manufactured by Mohr and Associates.

The researchers conclude the MDT-1's unique measurements are likely more informative than standard MT penetrometer tests or acoustic resonance techniques with which the industry has more recently experimented. The report goes on to state that the WABP intends to use the MDT-1's Cn measurements to reduce the need for labor-intensive taste-testing as they develop new apple varieties.

According to Brandt Mohr, Mohr's chief technologist, the MDT-1 measures some of the same fruit characteristics as a consumer.

"Think of the MDT-1's plunger as a mechanical tooth," Mohr says. "The MDT-1 measures the energy released by the crunch of the apple as plunger advances in a way that is repeatable and operator-independent. Fruit firmness alone is not adequate because a firm apple is not necessarily a crisp apple."

According to Mohr, the WABP team's results confirm the company's internal findings and provide a solid basis for wider adoption of the technology throughout the horticultural research community and industry.

Mohr Digi-Test Series computerized penetrometers include the MDT-1 and the new MDT-2 instrument planned for release in early 2011. The instruments can measure numerous fruit quality parameters. Standard software and fixtures enable accurate high-volume testing of fruit and other agricultural products. Available features include automated report generation, barcode scanner integration, and custom fixtures for general materials testing. To learn more about the MDT-1, visit the Mohr and Associates website.

Established in 1982, Mohr and Associates develops innovative test and measurement instrumentation for a wide range of applications. Visit the Mohr and Associates' website for more information.