Characterisation of the volatile profile of orange juice contaminated with Alicyclobacillus acidoterrestris F. Bianchi a , M. Careri a , A. Mangia a , M. Mattarozzi a , M. Musci a, * , I. Concina b , E. Gobbi c a Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Università degli Studi di Parma, Viale Usberti 17/A, 43100 Parma, Italy b SENSOR Laboratory, CNR-INFM, Dipartimento di Chimica e Fisica per l’Ingegneria e per i Materiali, Università di Brescia, Via Valotti 9, 25133 Brescia, Italy c Dipartimento di Biologia e Protezione delle Piante, Università di Udine, Via Scienze 208, 33100 Udine, Italy article info Article history: Received 21 May 2009 Received in revised form 20 April 2010 Accepted 1 May 2010 Keywords: Orange juice Alicyclobacillus acidoterrestris Volatile profile Multivariate analysis Guaiacol 2,6-Dibromophenol abstract A rapid and reliable analytical method, based on the characterisation of the volatile profile by dynamic headspace extraction followed by gas chromatography mass–spectrometry, was developed in order to early detect Alicyclobacillus acidoterrestris spoilage in orange juice. Gas chromatographic peak areas were submitted to multivariate statistical analysis (principal component and linear discriminant analysis) in order to visualise clusters within samples and to detect the volatile compounds able to differentiate con- taminated from not-contaminated samples. Significant differences in the volatile profile of the analysed samples were found, assessing the reliability of the proposed method to detect the A. acidoterrestris con- tamination in orange juice. Neither guaiacol nor 2,6-dibromophenol, usually regarded as A. acidoterrestris contamination markers, were detected in the analysed samples. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Orange juice is undoubtedly the most popular fruit beverage worldwide. It is greatly appreciated by the consumers, due both to its nutritional and sensory properties. The flavor of orange juice has been extensively studied in the past in order to evaluate and guarantee the quality and the authen- ticity of this product, as well as to detect adulterations (Brat, Rega, Reynes, & Brillouet, 2003; Hognadottir & Rouseff, 2003; Robards & Antolovich, 1995; Shaw, 1991; Tonder, Petersen, Poll, & Olsen, 1998). The quality of orange juice and, consequently, consumer acceptance, can be dramatically reduced if off-flavors occur; as a consequence, the juice industry can suffer economic losses. One of the possible ways leading to off-flavors production is microbio- logical contamination, thus requiring not only spoilage prevention, but also its early detection. Amongst non-pathogenic bacteria, great attention has been devoted to Alicyclobacillus acidoterrestris, a thermophilic and acidophilic spore-forming bacterium. Orange juice can be contaminated with spores of A. acidoterrestris, mainly coming from soil; due to their resistance to temperature and acid pH, spores can survive to the pasteurisation process (Chang & Kang, 2004). A. acidoterrestris has been recognised as the responsi- ble for the production of off-flavors in different kind of juice, including orange juice, amongst which guaiacol (2-methoxyphe- nol) and 2,6-dibromophenol are recognised as the most powerful compounds contributing to taint (Chang & Kang, 2004; Gocmen, El- ston, Williams, Parish, & Rouseff, 2005; Jensen & Whitfield, 2003; Petthiper, Osmundson, & Murphy, 1997; Whitfield, 1998) due to their very low odour threshold value (2–100 lgl À1 in water for guaiacol and 0.0005 lgl À1 in water for 2,6-dibromophenol) (Chang & Kang, 2004; Zierler, Siegmund, & Pfannhauser, 2004). To our knowledge, no previous studies have been carried out aimed at characterizing the volatile fraction of A. acidoterrestris contami- nated orange juice. In this study we tested the potentiality of dynamic headspace (DHS) extraction followed by gas chromatography–mass spec- trometry (GC–MS) to early detect A. acidoterrestris spoilage in con- taminated orange juice (10 4 CFU ml À1 ). The comparison of the volatile profile of not-contaminated samples with that of contam- inated ones could allow the detection of significant differences amongst samples. In fact, it has been assessed that the volatile pro- file of food, depending both on the nature and the relative amount of volatile compounds, represents a fingerprint of the product that can be used not only to assess food quality (Bianchi et al., 2007) but also to detect adulteration, including microbial spoilage (Bianchi et al., 2009). Determination of guaiacol and 2,6-dibromophenol, usu- ally regarded as A. acidoterrestris contamination markers, was also performed by solid-phase microextraction (SPME) followed by GC–MS (Zierler et al., 2004), in order to verify their possible forma- tion also at low contamination levels. 0308-8146/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2010.05.023 * Corresponding author. Tel.: +39 0521 905446; fax: +39 0521 905556. E-mail address: marilena.musci@unipr.it (M. Musci). Food Chemistry 123 (2010) 653–658 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem