Morphometric analysis and tissue structural continuity evaluation of senescence progression in fresh cut papaya (Carica papaya L.) Gabriela C  aez-Ramírez a , Liliana Alamilla-Beltr  an b , Gustavo F. Guti  errez-L  opez b, * a Agro-industrial Processes Research Group. Biosciences Graduate Program, Engineering Faculty, Universidad de La Sabana, Campus Puente del Común, Km 7 Vía Autopista Norte, Bogot a DC, Colombia b Departamento de Graduados e Investigaci on en Alimentos, Escuela Nacional de Ciencias Biol ogicas, Instituto Politecnico Nacional, Plan de Ayala y Carpio S/N, CP 11340, Ciudad de Mexico, Mexico article info Article history: Received 27 April 2017 Received in revised form 10 July 2017 Accepted 6 August 2017 Available online xxx Keywords: Papaya Digital image analysis Tissue structural continuity Multifractal analysis Lacunarity abstract Senescence prompted after cutting and environmental exposure was evaluated in fresh cut papaya in two ripening stages and two tissue locations by confocal laser scanning microscopy and digital image analysis to stablishing tissue structural stability. Self-fluorescence images from two emission channels were analysed through multifractal parameters, lacunarity, and skeleton attributes. Skeletons features reflected tissue integrity by the number and length of branches, and amount of junctures as key elements in the microarchitecture of the cellular supportive structure, depending on pectin variation. Tissue sta- bility could be described through the integrity of continuity lines given by the connected cell walls and middle lamella. The patterns of structural continuity lines showed properties of a multifractal set. Ripened and exposed tissues addressed lower singularity. Digital Image analysis allowed to determining stability status associated to tissue integrity and structural continuity by establishing singularities in heterogeneous tissue netting when describing senescence progression of fresh cut papaya. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Papaya (Carica papaya L.) is a fruit that originated in the Carib- bean coast of Mesoamerica and spread around the world. It is an important crop given its high agricultural yield, sensory attributes, functional properties (Jim enez et al., 2014), and nutritional value, particularly as a good source of carotenes (Schweiggert et al., 2014). The metabolic phenomena that occurs during fruit development and ripening causes sensorial and compositional changes, which intensify after minimal processing in cut fruits ready-to-eat due to abiotic stress (Lara et al., 2014). Abiotic stress tolerance challenges shelf life (Ma et al., 2017). Natural senescence and abiotic stress- induced senescence are associated with structural degradation and cell death (Brummell et al., 2004; Gepstein and Glick, 2013). Cellular structure determines mechanical, optical, chemical, microbiological as well as shelf life stability. Therefore, cells from different type of tissue or different microscale arrangement report diverse physical responses when facing the same adverse factors (Li and Thomas, 2014). Fruit and vegetable living cells are enclosed in a primary cell wall, which consists of a three-dimensional (3D) multicomponent hydrated matrix of cellulose microfibrils, pectin, hemicellulose and structural proteins, surrounded by the middle lamella formed mainly by pectin responsible for cell-to-cell adhe- sion (Cosgrove, 2016; Goulao and Oliveira, 2008). Cell wall and middle lamella integrity maintain tissue morphology and func- tionality, depending on ripening and processing (Phothiset and Charoenrein, 2014). Therefore, disruption of cell walls and middle lamella leads to softening, senescence progression and other changes in macro- and micro-structural levels (C aez-Ramirez et al., 2015). Structural integrity evaluation has been applied to follow processing changes in onions to identify parenchymal cell integrity changes after the application of high pressure (Gonzalez et al., 2010); in strawberry authors studied softening due to pectin depolymerisation by atomic force microscopy (Pos e et al., 2015); and in apple, to determine tissue continuity affected by pressure impregnation (S. Wang et al., 2015). Complex fruit microstructures were also assessed using 2D and 3D images. For example, morphometric parameters and linear discriminant analysis described structures in apple mesocarp tissue from Confocal Laser Scanning Microscopy (CLSM) images (Pieczywek and Zdunek, 2012). Other studies on apple, pome, and mango applied 3D X-ray * Corresponding author. E-mail address: gusfgl@gmail.com (G.F. Guti errez-L opez). Contents lists available at ScienceDirect Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng http://dx.doi.org/10.1016/j.jfoodeng.2017.08.004 0260-8774/© 2017 Elsevier Ltd. All rights reserved. Journal of Food Engineering xxx (2017) 1e13 Please cite this article in press as: Caez-Ramírez, G., et al., Morphometric analysis and tissue structural continuity evaluation of senescence progression in fresh cut papaya (Carica papaya L.), Journal of Food Engineering (2017), http://dx.doi.org/10.1016/j.jfoodeng.2017.08.004