Texture, colour and optical characteristics of a meat product depending on smoking time and casing type Estefanía Ledesma a, b , Amanda Laca a , Manuel Rendueles a, * , Mario Díaz a, ** a Department of Chemical Engineering and Environmental Technology, University of Oviedo, Faculty of Chemistry, C/Juli an Clavería s/n, 33071, Oviedo, Principality of Asturias, Spain b Research, Development and Innovation (R&Dþi) Department, El H orreo Healthy Food S.L, C/Las Caba~ nas 43-45, 33180, Nore~ na, Principality of Asturias, Spain article info Article history: Received 22 June 2015 Received in revised form 20 July 2015 Accepted 30 July 2015 Available online 4 August 2015 Keywords: Chorizo Smoked meat products Casing Colour Texture Microstructure abstract Synthetic casings have recently been found to prevent the penetration of carcinogenic compounds in meat products during smoking, in contrast to natural casings. In this paper, physical characteristics of 48 chorizos encased in natural (ChN) and synthetic (ChS) casings, during 11 days of direct smoking, were compared by means of texturometry, colourimetry, moisture, Scanning Electron Microscopy and Fluo- rescence Stereo Microscopy analyses. The lightness (L*) of ChS is lower (p ¼ 0) than ChN. During 5 days, ChS presented higher hardness and browning index, and less redness (a*), yellowness (b*) and chroma than ChN (p < 0.05). At 7 days, no differences (p > 0.05) were found in a*, b*, hue angle or chroma. Except at 1 day, no differences (p > 0.05) were found in their moisture. Physical characteristics were suitable in both cases, but synthetic casing reduces production time, prevents the penetration and accumulation of soot particles in mass cavities, and enables the standardization of chorizo. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction The consumption of meat and meat products, which contain important levels of protein, vitamins, minerals and essential micronutrients, is growing in developing countries. Meat process- ing provides the opportunity to add value, reduce prices, improve food safety and extend shelf life. However, unsuitable processing can lead to undesirable health effects and environmental impact (EC, 2013; FAO, 2013). Chorizo is a typical Spanish meat product. In northern Spain and other European countries, chorizo is exposed to direct smoking with the main aim of prolonging its shelf life and conferring sensorial characteristics (Lorenzo, Purri ~ nos, Bermúdez, Figueiredo, & García Font an, 2011). During non-controlled smok- ing, however, chemical contaminants are also formed, such as polycyclic aromatic hydrocarbons (PAH), dioxins, formaldehyde, nitrogen and sulphur oxides (relevant in the formation of nitrosa- mines, for instance) and even heavy metals (CAC, 2009). PAH have been found to be carcinogenic for humans (ATSDR, 2009). In order to protect consumers from PAH contamination, laws and codes of best practices in food processing have been proposed. Regulation (EU) No. 835/2011 of 19 August 2011 (EC, 2011) has recently reduced the maximum permissible content in BaP (a marker of the presence of PAH) in smoked meat and smoked meat products from 5.0 to 2.0 mg/kg in wet weight from 1/9/2014 on. The permissible sum of PAH4 (benzo(a)pyrene, benzo(a)anthra- cene, benzo(b)fluoranthene and chrysene) in these foods has been reduced from 30.0 to 12.0 mg/kg in wet weight from 1/9/2014 on. The “Code of practice for the reduction of contamination of food with (PAH) from smoking and direct drying processes” (CAC/RCP 68/2009) advocates the control of certain variables to prevent PAH contamination. A number of studies have been carried out to test these variables, including the kind of fuel (Hitzel, P€ ohlmann, Schw€ agele, Speer, & Jira, 2013; P€ ohlmann, Hitzel, Schw€ agele, Speer, & Jira, 2012; Stumpe-V  ıksna, Bartkevics, Kukare, & Morozovs, 2008), smoking method (P€ ohlmann et al., 2012, P€ ohlmann, Hitzel, Schw€ agele, Speer, & Jira, 2013a;  Skaljac et al., 2014; Varlet et al., 2007), duration of smoking (Djinovic, Popovic, & Jira, 2008; Essumang, Dodoo, & Adjei, 2013; Ledesma, Rendueles, & Díaz, 2014), fat content (P€ ohlmann, Hitzel, Schw€ agele, Speer, & Jira, 2013b), distance between the food and * Corresponding author. ** Corresponding author. E-mail addresses: mrenduel@uniovi.es (M. Rendueles), mariodiaz@uniovi.es (M. Díaz). Contents lists available at ScienceDirect LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt http://dx.doi.org/10.1016/j.lwt.2015.07.077 0023-6438/© 2015 Elsevier Ltd. All rights reserved. LWT - Food Science and Technology 65 (2016) 164e172