Relation of Biogenic Amines’ Formation with Microbiological and Sensory Attributes in Lactobacillus-Inoculated Vacuum-Packed Rainbow Trout (Oncorhynchus mykiss) Fillets PANAGIOTA KATIKOU,* ,† DIMITRIOS GEORGANTELIS, † EVANGELOS K. PALEOLOGOS, ‡ IOANNIS AMBROSIADIS, † AND MICHAEL G. KONTOMINAS ‡ Department of Hygiene and Technology of Animal Origin Products, School of Veterinary Medicine, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece, and Laboratory of Food Chemistry and Food Microbiology, Department of Chemistry, University of Ioannina, 45110 Ioannina, Greece The biogenic amine (BA) content of vacuum-packed filleted rainbow trout (Oncorhynchus mykiss) inoculated or not with two different Lactobacillus strains, individually or in combination, was monitored during refrigerated storage for 20 days and related to respective bacteriological and sensory changes occurring during the same period. Eight amines, namely putrescine, cadaverine, tyramine, tryptamine, -phenylethylamine, histamine, spermine, and spermidine, were determined, whereas agmatine was not detected in any of the samples. In all cases, BA concentration was higher (P e 0.05) in the controls compared to all inoculated treatments, whereas the trend with regard to the bacterial populations (Enterobacteriaceae, pseudomonads, and H 2 S-producing bacteria) and the off-odor scores was similar. Inoculation with Lactobacillus sakei CECT 4808 showed the best preservative effect among inoculated treatments. Concentrations of putrescine and cadaverine, the main BAs formed, correlated well with both spoilage bacterial counts and off-odor scores and can be useful indicators of shelf life. Spermine and spermidine contents decreased during storage, while levels of the other determined BAs remained below 10 mg/kg even after sensory rejection. KEYWORDS: Biogenic amines; rainbow trout fillets; Lactobacillus sakei; Lactobacillus curvatus; vacuum- packaging; Oncorhynchus mykiss INTRODUCTION Fresh fish are known to be extremely perishable food commodities, and consequently their quality and safety are parameters of major concern to both industry and consumers. Initial quality deterioration of fresh fish is primarily caused by autolytic changes, whereas subsequent quality loss and spoilage occur as a result of bacteriological activity. A wide variety of bacterial species are involved in the spoilage of refrigerated fish under aerobic and vacuum storage conditions, including Pseudomonas spp., Enterobacteriaceae, Shewanella putrefaciens, Alteromonas spp., Photobacterium phosphoreum, Brochothrix thermosphacta, and lactic acid bacteria (LAB) (1). Although abundant data exist regarding spoilage of marine fish stored under vacuum, little is known about the spoilage bacteriology of vacuum-packed freshwater fish. It is unlikely, though, that P. phosphoreum plays a major role as it is a sodium-requiring species. Moreover, TMAO-reducing organisms such as S. putrefaciens are commonly found at lower levels in vacuum- packed freshwater fish than in marine fish and usually at later stages of storage (1). Evaluation of fish quality and safety is based on the measurement of various microbiological, chemical, and/or sensory parameters, which are associated with both freshness and changes leading to fish spoilage. Sensory evaluation is believed to be the simplest and most reliable method for establishing freshness as well as the shelf life of fish and, consequently, for the assessment of fish spoilage; however, in order to be objective it requires both highly trained and specialized assessors and statistical treatment of the data, which can be a problem under industrial conditions. For this reason alternative methods have been proposed, among which is the determination of nonvolatile amines (2). Biogenic amines (BAs) are nonvolatile compounds, most of which are normally present in fresh fish at very low levels. Gradual accumulation of BAs is associated with the growth of bacteria, whereas their presence at high concentrations is indicative of bacterial spoilage (3). BAs are formed by decarboxylation of amino acids as a result of bacterial metabolism; amino acid decarboxylases are found in, among others, certain Enterobacteriaceae, Pseudomonas, Clostridium, Lactobacillus, Streptococcus, and Micrococcus species. Enterobacteriaceae are usually implicated in the forma- * Address correspondence to this author at the National Reference Laboratory on Marine Biotoxins, Centre of Veterinary Institutions of Thessaloniki, Ministry of Rural Development and Food, 3A Limnou St., 54627 Thessaloniki, Greece (telephone +30 2310 552928; fax +30 2310 566581; e-mail pkatikou@hotmail.com). † Aristotle University of Thessaloniki. ‡ University of Ioannina. J. Agric. Food Chem. 2006, 54, 4277-4283 4277 10.1021/jf0602121 CCC: $33.50 © 2006 American Chemical Society Published on Web 05/16/2006