Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/22/2009
Publication Date: 8/1/2009
Citation: Lu, R., Tipper, N.C. 2009. A Portable Device for the Bioyield Detection to Measure Apple Firmness. Applied Engineering in Agriculture. 25(4):517-523. Interpretive Summary: Fruit firmness is of key importance in determining consumer satisfaction. Firmness also serves as an important physiological indicator in determining the best time to harvest a crop of apples. In addition, the ability to monitor firmness will enable packinghouse operators to better control and optimize postharvest handling and storage regimes, thus resulting in improved quality and a consistent supply of apples for the market. In this article, we report on the development and evaluation of a portable device for the automatic detection of bioyield force to measure fruit firmness. The bioyield phenomenon occurs to an apple under compressive loading, which causes cell failure without destroying the integrity of the fruit tissue. Bioyield measurement causes minimum damage to the fruit and does not degrade it after testing. The device design features accurate control of loading speed, automated detection and recording of bioyield point, and ease of operation. Moreover, the device is portable and low in cost, can operate stand-alone or via computer, and thus is suitable for use in both field and laboratory environments. Bioyield measurements correlated well with standard destructive firmness measurements with the R-squared values of 0.835, 0.654, and 0.751 for Golden Delicious, Red Delicious, and the pooled data, respectively. Bioyield measurement was as sensitive to firmness change over time as the standard destructive test for apples that underwent accelerated softening. This device is now being used for measuring the firmness of apples during postharvest handling and monitoring fruit conditions during storage. It could also be used for measuring the firmness of on-tree apples and may be integrated with robotic harvesters for selective harvest and in-orchard quality grading.
Technical Abstract: The bioyield phenomenon occurs to an apple under compressive loading, which causes cell failure without destroying the integrity of the fruit tissue. Force at the bioyield point is useful for nondestructive evaluation of fruit firmness. A portable device, which consisted of an off-shelf force meter, an actuation driver and control module, was developed for detecting bioyield force from apples. The device was tested and evaluated to determine its correlation with the standard Magness-Taylor (MT) firmness tester, measure sensitivity to changes in firmness over time, and quantify firmness variation over the fruit. Bioyield force correlated well with MT force with the R-squared values of 0.835, 0.654, and 0.751 for Golden Delicious, Red Delicious, and the pooled data, respectively. Bioyield force was as sensitive to firmness change over time as MT force (R-squared value of 0.990) for apples that underwent accelerated softening. The bottom section (the calyx end) of an apple is significantly firmer than the middle and top sections of the fruit. Moreover, the south face or sunny side of an apple is significantly firmer than the north face or shady side of the fruit. Firmness measurement accuracy improves when measuring opposing sides of an apple to obtain a single, averaged firmness measurement. Because bioyield measurements do not degrade the quality of a tested apple, this device is useful for measuring the firmness of apples in the orchard and during postharvest handling, and monitoring fruit conditions during storage.