Original article Characterisation of the volatiles of yellowfin tuna (Thunnus albacares) during storage by solid phase microextraction and GC–MS and their relationship to fish quality parameters Ranjith K.B. Edirisinghe*, Andrew J. Graham & Sarah J. Taylor Natural Resources Institute (NRI), University of Greenwich, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK (Received 13 May 2005; Accepted in revised form 23 March 2006) Summary Investigations were carried out to extract the volatile compounds of fish using solid phase microextraction (SPME) in order to develop a new rapid indicator for determining the quality of fish. Changes in the aroma composition of yellowfin tuna (Thunnus albacares) was studied at 30 °C and in ice, using SPME GC–MS, and their relationship with the fish quality parameters – total volatile basic nitrogen and sensory analysis – was determined using principal component analysis (PCA) and stepwise multiple regression analysis. Hexanal (30.9%) and 2-nonanone (28.4%) were recorded in relatively high amounts in fresh fish, whereas 3-methyl-1-butanol and 3-hydroxy-2-butanone increased with storage time. PCA clearly differentiated the volatile profile of each sampling stage (P < 0.05) throughout storage treatments. Regression analysis showed a significant relationship between the fish quality and the levels of 3-methyl-1-butanol and pentadecane. The findings highlight the possibility of developing a rapid quality evaluation method for fish using SPME GC–MS. Keywords Fish quality, GC–MS, principal component analysis, sensory analysis, solid phase microextraction, tuna, total volatile basic nitrogen, volatiles. Introduction Tuna is the most highly traded fish species, with an estimated annual world trade worth over US$ 5 billion in 1997. The production has increased almost eightfold, from around 400 000 tons in 1950 to over 3.6 million tons in 1999 (FAO, 1999). The assessment of the quality of fish is an important factor because of the high commercial demand for fresh fish. A number of methods have been used to measure fish quality based on physical and chemical changes and postmortem microbial growth during storage (Olafsdottir et al., 1977). Most of these methods are highly expensive and time consu- ming, and therefore there is a need to invent new and rapid techniques to assess fish freshness relevant to research and industry. The aroma is one of the most important indicators used by consumers to judge the freshness of fish. The aroma quality of fish changes rapidly in relation to the degree of freshness of the product, and for this reason sensory analysis of the aroma is used to evaluate the quality of fish by consumers, researchers and the fish industry as a whole. The characteristic fresh fish odour, mainly asso- ciated with aldehydes and ketones, tends to change as a result of enzymatic (Josephson & Lindsay, 1986) and bacterial (Shewan, 1962) action during spoilage. The process produces different kinds of volatile compounds with characteristic off-odours such as 2,4-heptadienal and 2,4,7-decatrienal (Karahadian & Lindsay, 1989), short-chain alcohols (e.g. ethanol, propanol, butanol) and 3-methyl-1-butanol, acetone, butanone, ethanal and propanal (Kawai, 1996) and some sulphur-containing compounds (Whitfield & Tindale, 1984). A number of volatile compounds such as ethanol, propanol, hexanal, butanol, 1-penten-2-ol have been identified in tuna fish (Human & Khayat, 1981). Some of these are reported to have a strong relationship with freshness of fish. In fresh fish, the concentration of volatiles is very low at the microgram per kilogram level. However, even at low concentration, some of these volatiles have a very intense odour that has an impact on sensory quality (Refsgaard et al., 1999). Analysis of fish volatiles is normally associated with gas chromatography – sometimes in combination with mass spectrometry. Dynamic and static headspace analyses are still popular techniques. The collection of volatiles by these methods is critical and time consuming and makes the analysis complex. *Correspondent: Fax: 00942529715; e-mail: ranjith.edirisinghe@nara.ac.lk International Journal of Food Science and Technology 2007, 42, 1139–1147 1139 doi:10.1111/j.1365-2621.2006.01224.x Ó 2007 Institute of Food Science and Technology Trust Fund