Advances in the ultrasound characterization of dry-cured meat products Edith Corona a , Jose V. Garcia-Perez a,⇑ , Tomas E. Gomez Alvarez-Arenas b , Nicholas Watson c , Malcolm J.W. Povey c , Jose Benedito a a Grupo de Análisis y Simulación de Procesos Agroalimentarios, Departamento Tecnología de Alimentos, Universitat Politècnica de València, Camí de Vera s/n, E46022 Valencia, Spain b UMEDIA (Ultrasound for Medical and Industrial Applications) Research Group, CSIC, Serrano 144, 28006 Madrid, Spain c School of Food Science and Nutrition, University of Leeds, Leeds LS2 9JT, United Kingdom article info Article history: Received 15 February 2013 Received in revised form 13 May 2013 Accepted 16 June 2013 Available online 25 June 2013 Keywords: Ultrasound Air-coupled Scanning acoustic microscopy Dry-cured meat products abstract In this work, the feasibility of using non-contact ultrasonic techniques (air-coupled and scanning acoustic microscopy, SAM) for characterizing different dry-cured meat products was assessed. Air-coupled ultra- sonic measurements were performed on vacuum packaged sliced dry-cured ham, and compared with contact measurements. The average ultrasonic velocity in dry-cured ham was 1846 ± 49 m/s and 1842 ± 42 m/s for air-coupled and contact measurements, respectively. The deviation (1% relative error) between both techniques was related to the influence of the heterogeneous structure and composition of dry-cured ham and the transducer focusing. The SAM was used to characterize dry-cured ham and cho- rizo samples. B-scan images for dry-cured ham and chorizo showed two dominant reflections from the sample, linked to reflections in the lean and fatty tissues. The results indicate that contact ultrasonic mea- surements could be replaced by the air-coupled technique, reducing the measuring time and the material handling. On the other hand, SAM technique allows the microscopic characterization of dry-cured meat products. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Dry-cured meat products, such as, salchichón, chorizo, dry- cured loin or dry-cured ham, among others, are products with high quality and consumer acceptance in Spain and other Mediterra- nean countries. Several techniques have been developed to objec- tively measure the quality traits of these products. Some of the techniques frequently used are invasive, by which the structure of the product is affected (Damez and Clerjon, 2008). Thereby, non-destructive techniques are being developed for assessing the quality of dry-cured meat products affecting minimally their struc- ture. These techniques include nuclear magnetic resonance (NMR) (Straadt et al., 2012), X-ray technologies (Santos-Garcés et al., 2010), near infrared spectroscopy (NIRS) (Håseth et al., 2012; Gar- cía-Rey et al., 2005) and ultrasound (Benedito et al., 2001; Niñoles et al., 2007, 2010, 2011; Santacatalina et al., 2011). The implemen- tation of these techniques in the meat industry could lead to a bet- ter control not only of raw materials but also intermediate and final products. Low intensity ultrasound can provide a rapid, accurate, on-line, inexpensive and non-destructive food and process characterization (Benedito et al., 2002; Chandrapala et al., 2012; Koch et al., 2011a, 2011b). In the meat sector, ultrasonic contact measurements had been used to for the characterization of macroscopic properties, such as the composition of raw meat mixtures (Benedito et al., 2001) or the textural properties (Llull et al., 2002) and composition of fermented meat products (Simal et al., 2003). Ultrasonic mea- surements have a larger penetration capacity than NIR technique and has a lower cost and easiness of on-line implementation than NMR and X-rays systems. However, sometimes the use of contact ultrasonic measurements involves the need of a couplant to im- prove the matching between the sample and the transducer, for example in the packaged products. Thus, for those applications where the use of couplants can affect the product quality or where the time of measurement restricts the application and removal of the couplant, air-coupled ultrasonic measurements can be a reli- able alternative. Air-coupled ultrasound is a promising non-destructive tech- nique, due to its minimally invasive nature and broad application range, including on-line application. However, the most important challenge lies in the several orders of magnitude acoustic imped- ance mismatch between air and materials of the transducer and the sample. The impedance mismatch causes high interfacial reflection and low acoustic transmission efficiency. This, along with the attenuation of ultrasound in the air, has hampered devel- oping a practical non-contact ultrasound such as inspection meth- od. Therefore, the efficiency of ultrasound transducers must be significantly improved. Even so, this technique has been used for the successfully inspection and detection of foreign bodies in 0260-8774/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jfoodeng.2013.06.023 ⇑ Corresponding author. Tel.: +34 963879376. E-mail address: jogarpe4@tal.upv.es (J.V. Garcia-Perez). Journal of Food Engineering 119 (2013) 464–470 Contents lists available at SciVerse ScienceDirect Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng