Transactions of the ASAE Vol. 46(2): 397–400 E 2003 American Society of Agricultural Engineers ISSN 0001–2351 397 ULTRASONIC CLASSIFICATION OF MEALINESS IN APPLES A. Mizrach, A. Bechar, Y. Grinshpon, A. Hofman, H. Egozi, L. Rosenfeld ABSTRACT . In modern agriculture, with its competitive markets, fruit quality is a significant factor, and mealiness impairs the quality of apples and reduces their market value and price. Retailers are perfectly able to distinguish a mealy product from a fresh one, describing it correctly with terms such as non–juicy, soft, etc. However, there is a need for a reliable method, incorporating appropriate sensors, for the nondestructive testing and classification of apples according to their mealiness; it needs to be designed for use by an untrained person. Several techniques have been suggested in the literature to detect and evaluate mealiness; they include destructive tests such as tensile tests, texture profile analysis, ultrasonic examination, etc., and some nondestructive sensory analysis methods based on, e.g., magnetic resonance, electrical impedance, and NIR. This article suggests a system based on ultrasonic energy absorbance for nondestructive determination of three mealiness levels (fresh, ripe and overripe) in Jonagold and Cox apples. The method is based on the emission of a known level of ultrasonic energy into the fruit flesh and measurement of the attenuated signal received after transmission through the fruit tissue. The strength of the received signal is affected by the mechanical structure of the tissue, the physiochemical quality indices, and any change in the quality attributes of the fruit. The detected sound waves were analyzed in parallel with determination of the mealiness level of the fruit. The results obtained suggest that it is possible to distinguish among the three mealiness levels in Jonagold fruits, but not in the Cox fruits. Keywords. Acoustic properties, Apples, Mealiness, Nondestructive, Ripeness, Ultrasonics, Ultrasound. n modern agriculture, with its competitive markets, the influence of fruit quality is significant and important. Therefore, quality evaluation of fruits and vegetables, during harvesting and in subsequent handling and storage, is an important issue that affects growers, marketers, and customers, and textural attributes of fruits and vegetables are among the main factors in quality assessment (Jowitt, 1974). In apple fruits, texture seems to be a primary quality attribute, together with flavor and appearance (Lapsely et al., 1992). Crispness, firmness, hardness, juiciness and mealiness are the most generally recognized texture attributes in apples, and mealiness impairs the quality of apples and reduces their market acceptability and price. Retailers have been found perfectly able to distinguish a mealy product from a fresh one, describing it correctly with terms such as non–juicy, soft, etc. (de Smedt, 2000); nevertheless, there is a need for a reliable method, supported by appropriate sensors, for nondestructive evaluation and classification of apples in terms of their mealiness. The demand for high quality calls for a reliable, rapid, Article was submitted for review in January 2002; approved for publication by the Food & Process Engineering Institute Division of ASAE in December 2002. Contribution from the Institute of Agricultural Engineering, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel, No. 713/01, 2001 Series. The authors are Amos Mizrach, ASAE Member, Senior Principal Scientist, Avital Bechar, ASAE Member, Scientist, Yosef Grinshpon, Research Engineer, Ahron Hofman, Research Technician, Haim Egozi, Research Technician, and Lavi Rosenfeld, Research Technician, Institute of Agricultural Engineering, Agricultural Research Organization, Bet Dagan, Israel. Corresponding author: Amos Mizrach, Institute of Agricultural Engineering, P.O. Box 6, Bet Dagan, 50250, Israel; phone: +972–3–9683451; fax: +972–3–9604704; e–mail: amos@agri.gov.il. non–destructive, non–invasive technique for measuring some of the texture attributes of the fruit, especially mealiness, that develop as it matures and that are indicative of its quality. Furthermore, such a technique must be usable by an untrained person. In addition to sensory analysis, several techniques for detection and measurement of mealiness in apples have been suggested in the literature. They include destructive methods based on, e.g., texture profile analysis (Tu and De Baerdmak- er, 1995), tensile tests (FAIR, 1998), and ultrasonic wave propagation in tissue (de Smedt, 2000), and nondestructive methods based on, e.g., magnetic resonance (Barreiro et al., 1999), acoustic impulse response (ASTEQ, 2001), and near–infrared (NIR) measurement (ASTEQ, 2001). Most of these sensory analyses are expensive and time consuming (de Smedt, 2000), and there is a need for a rapid nondestructive technique. Such a technique would be of considerable economic interest, both to the growers and to the retailers. This article suggests a system and method based on ultrasonic energy absorbance for the rapid nondestructive determination of mealiness in apples. The method is based on a patented development that enables the fruit quality attributes to be assessed by measuring the changes in ultrasonic sound waves passing through the peel and flesh (Mizrach et al., 1994). Several versions of devices based on this technique have been developed and successfully used for nondestructive determination of quality attributes in avoca- do, mango, and other fruits and vegetables (Mizrach et al., 1989, 1996, 1997, 1999a, 1999b). A recently developed, more advanced model offers the capability of rapid measure- ment and discrimination among three ripeness levels (fresh, ripe, and overripe) in apples (ASTEQ, 2001). I