Original article Aroma profile of Niagara grape juice contaminated with multicoloured Asian lady beetle taint using gas chromatography ⁄ mass spectrometry ⁄ olfactometry Carolyn F. Ross,* Maria U. Rosales & Virginia C. Fernandez-Plotka School of Food Science, Washington State University, Pullman, WA 99164, USA (Received 10 September 2009; Accepted in revised form 20 January 2010) Summary The objective of this study was to determine the odour-active compounds present in Niagara grape juice tainted with multicoloured Asian lady beetle (MALB: Harmonia axyridis: Coleoptera: coccinellidae). Niagara grape juice was made with (2.5 MALB ⁄ L) and without MALB and evaluated using solid-phase microextraction coupled with gas chromatography ⁄ mass spectrometry ⁄ olfactometry (GC ⁄ MS ⁄ O) to tentatively identify compounds. Compared to the control juice, phenol, described as musty ⁄ mouldy, was found to be unique to the MALB-tainted grape juice. The four odourants significantly higher in the MALB- tainted grape juice were described as fruity, asparagus, stagnant water ⁄ chemical and musty ⁄ mouldy, tentatively corresponding to octanal, 3-sec-butyl-2-methoxypyrazine (SBMP), 2-methoxy-4-methylphenol and decanal, respectively. Three of the five compounds found in the MALB-tainted juice have been reported to be produced by live MALB. While past literature has focused on the contribution of 3-alkyl-2- methoxypyrazines to MALB-taint, the present study suggests other compounds, in addition to SBMP, may contribute to the aroma profile of MALB-tainted grape juice. Keywords Gas chromatography ⁄ olfactometry, Harmonia axyridis, multi-coloured Asian lady beetle, Niagara grape juice. Introduction The multicoloured Asian lady beetle (MALB) (Harmo- nia axyridis: Coleoptera: coccinellidae) was originally introduced into the USA as a method of biocontrol for aphids and other soft bodied insects (Nalepa et al., 1996). However, the establishment of MALB popula- tions and the off-aromas associated with the presence of MALB in wine grapes (Galvan et al., 2007), finished wines (Pickering et al., 2004; Galvan et al., 2008) and grape juice (Ross et al., 2007; Pickering et al., 2008) have been documented in the literature. In 2001, the presence of MALB taint resulted in the disposal of a million liters in Ontario, directly causing the Ontario wine industry a multi-million dollar loss in sales. The establishment of MALB populations has also been reported as a harvest contamination problem in Europe (Linder et al., 2009), including Denmark, France, Czech Republic and UK (Majerus et al., 2006; Brown et al., 2008), with the prediction that the spread of MALB will continue through Europe (Brown et al., 2008). Several studies have reviewed the behaviour and impacts of MALB on other predators and on fruit crops (Koch et al., 2004; Galvan et al., 2007a; Koch & Galvan, 2008). Additional studies have demonstrated the potential of MALB presence to influence wine and grape juice quality (Pickering et al., 2004, 2005; Ross et al., 2007). The off-aromas associated with the pres- ence of MALB have been attributed to the presence of 3-alkyl-2-methoxypyrazines. One of the key 3-alkyl-2- methoxypyrazines thought to be responsible for the off-odour is 2-isopropyl-3-methoxypyrazine (IPMP; Pic- kering et al., 2005, 2006, 2007, 2008). In addition to IPMP, 3-sec-butyl-2-methoxypyrazine (SBMP), 3-isobu- tyl-2-methoxypyrazine (IBMP) and 2,5-dimethyl-3- methoxypyrazine (DMMP) have also been found to be produced by live MALB, possibly contributing to the off-odours associated with MALB-taint (Cudjoe et al., 2005; Cai et al., 2007). In wine, Pickering et al. (2005) found that wines made from grape juice infested with 10 MALB L )1 had higher concentrations of IPMP than a control wine. However, a recent study by Galvan et al. (2008) found that contrary to this research, IPMP concentrations did not vary with MALB infestation level. They also reported that SBMP was present in the *Correspondent: Fax: +1 509 335 4815; e-mail: cfross@wsu.edu International Journal of Food Science and Technology 2010, 45, 789–793 789 doi:10.1111/j.1365-2621.2010.02197.x Ó 2010 The Authors. Journal compilation Ó 2010 Institute of Food Science and Technology