Submitted to: Fruit Nut and Vegetable Production Engineering
Publication Type: Proceedings
Publication Acceptance Date: January 15, 2002
Publication Date: N/A
Interpretive Summary: Near-infrared (NIR) spectroscopy shows great potential for nondestructively measuring the internal quality of apple fruit. Currently, most NIR instruments are still too expensive and large in size to be used as a portable sensor for measuring internal quality of apple fruit. Development of a low cost, portable sensing technique would help the grower make better rharvest decisions and provide the fruit packer, the fruit inspector, and perhaps the consumer with a useful tool for assessing fruit quality. In this study, we investigated the feasibility of using a low cost NIR microspectrometer, in conjunction with a specially designed sensing probe assembly, as a NIR sensor for measuring the sugar content and firmness of apple fruit. Experiments were conducted with this new sensor on three varieties of apples. Results showed that the sensor was capable of measuring the sugar content of apple fruit with the prediction errors ranging between 0.65% and 0.91%. Relatively good predictions of fruit firmness were also obtained with the prediction errors as low as 8.3 N for Empire apples and 7.9 N for Red Delicious apples. This study indicates that the new NIR sensor can be used to measure the sugar content of apple fruit and it also has the potential for measuring fruit firmness. With further research, this low-cost NIR sensor can be a valuable tool to the fruit industry and the consumer for assessing the internal quality of apple fruit. This would help the industry in providing better quality fruit to the consumer, thus improving the profitability of growing apples.
Technical Abstract: Development of a portable near-infrared (NIR) sensor will help the fruit grower make better harvest decisions and provide a useful tool for the fruit packer, the fruit inspector, and perhaps the consumer to assess fruit postharvest quality more accurately and objectively. The objective of this study was to develop a low cost, portable NIR sensor for measuring the sugar content and firmness of apple fruit. A feasibility study was performed on using a new microspectrometer as a NIR sensor to measure the sugar content and firmness of apple fruit. A specially designed sensing probe assembly was constructed, which acquires spectral data from two different distances between light source and the detecting probe in interactance mode. Experiments were performed on three apple cultivars, 'Empire', 'Golden Delicious', and 'Red Delicious', to evaluate the performance of the new sensor. Results showed that the sensor was capable of measuring the sugar content of apple fruit with the correlation coefficient (r) as high as 0.77 and the standard error of prediction (SEP) of 0.65 degree Brix. Relatively good firmness predictions were also obtained for Empire apples (r=0.79 and SEP=8.3 N) and Red Delicious apples (r=0.48 and SEP=7.9 N). Ratio spectra, which are less affected by the variation in light source and detector performance, gave equally good predictions as those using relative reflectance. With further research, this low cost NIR sensor can be used for fruit quality inspection.