Postharvest Biology and Technology 36 (2005) 51–59 Micro-wound detection on apple and pear fruit surfaces using sulfur dioxide A. Amiri ∗ , G. Bompeix LaboratoryofPlantParasite,UniversityPierreetMarieCurie,BP155,4placeJussieu,75252Paris,France Received 14 April 2004; accepted 17 October 2004 Abstract The fumigation of apple and pear fruit for 2 h with 2 ml/l of sulfur dioxide at room temperature enabled adequate detection of fresh and old micro-wounds varying from 0.1 to 5 mm in diameter. A bleached spot surrounded by a brown halo formed around the wounds allowing their visualization. Otherwise, the same symptoms were observed when fruit were treated for 2 h with 20 ml sodium metabisulfite solution at 20 g/l. The incidence of wounding among SO 2 treated apples varied from 9 to 20% and from 13 to 24% in the 2001–2002 and 2002–2003 harvest periods, respectively. The susceptibility was higher on pear fruit which averaged 17–30% of wounded fruit at harvest for the same periods. Comparatively, the incidence of wounding varied between 5 and 11% when apple or pear fruit were evaluated visually for superficial defects. Additional wounds occurred during the sizing of ‘Cameo’ apples. Thus, the incidence of wounding was around 12 and 23% before and after sizing, respectively. SO 2 fumigation revealed an abraded surface two-fold larger on fruit after sizing resulting principally from impacts between adjacent fruit and between fruit and the bin sides. © 2004 Elsevier B.V. All rights reserved. Keywords: Wounds; Harvest; Sizing; SO 2 ; Sodium metabisulfite; Apples; Pears 1. Introduction The extracellular cuticle protects plants against wa- ter loss (Schreiber and Reiderer, 1996) and invasion of microorganisms (Jenks et al., 1994; Markstadter et al., 2000). The breakdown of this protective layer is closely related to the firmness and plasticity of cell walls, and to the adhesive strength between neighbor- ∗ Corresponding author. Tel.: +33 1 44 27 59 08; fax: +33 1 44 27 40 02. E-mailaddress: amiri@ccr.jussieu.fr (A. Amiri). ing cells (Banks, 1985). Breaking of cells generally results in openings that are required for the penetration of several pathogens. Consequently, numerous stud- ies have been conducted to evaluate the risks of the level of surface injury that is observed at harvest and in moving fresh fruit from the tree to the packinghouse (Gordon, 1985; Sugar and Penwell, 1989; Spotts et al., 1998). The visualization of non-obvious wounds may be difficult to do. Thus, methods such as confo- cal laser scanning microscopy (CLSM) (Veraverbeke et al., 2001) and electrical impedance spectroscopy (Harker and Maindonald, 1994; Jackson and Harker, 0925-5214/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.postharvbio.2004.10.010