In¯uence of Active Packaging on the Shelf-life of Minimally Processed Fish Products in a Modi®ed Atmosphere By Laura Franzetti, Stefano Martinoli, Luciano Piergiovanni* and Antonietta Galli Universita Á degli Studi di Milano, Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Via Celoria, 2, 20133 Milano, Italy. Theeffectivenessofaninnovativefoamplastictray,providedwithabsorbersfor volatileaminesandliquids,ontheshelf-lifeofdifferent®shproductspacked underamodi®edatmosphere(40%CO 2 :60%N 2 ),wasevaluatedincomparison withastandardtray.Filletsofsole(Soleasolea),steaksofcod(Merluccius merluccius)andwholecuttle®sh(Sepia®llouxi),placedinthetwodifferentkinds oftrays,werekeptat3°C.Microbiological(TBC-,Gram-negative-,H 2 S-producing bacteriaandlacticacidbacteria)andchemical(surfacepH,TMAheadspace) analyseswerecarriedoutafter3,7and10daysofstorage.Thenewpackaging, associatedwitharigorouscontrolofstoragetemperature,increasedtheshelf-life upto10days.Infact,theinnovativetraysequestratedthegreaterpartof trimethylaminefromtheheadspaceandledtodelayedmicrobialgrowth, especiallyofGram-negativeandH 2 S-producingbacteria,andinadditionit favouredthegrowthofbacterialstrainssuchas Moraxellaphenylpiruvica,which arenotinvolvedinoff-¯avouringproduction(especiallyH 2 S),becauseoftheir lypolitic activity. Copyright O 2001JohnWiley&Sons,Ltd. Received 16 July 2001; Revised 30 October 2001; Accepted 7 December 2001 KEY WORDS: active packaging; TMA absorber; Shewanella putrefaciens; ®sh products INTRODUCTION Fish products are certainly the most dif®cult fresh foodstuffs to preserve, because of their high water contents (65±80%), post mortem pH value (>6) and large amounts of non-protein nitrogen (9±18%, N tot ). The rate of the deterioration processes depends widely on storage temperature; in fact, chill temperatures (0±4°C) reduce bacterial growth and therefore spoilage activity. 1 The micro¯ora of cold or temperate saltwater ®sh is dominated by psychrotrophic Gram-nega- tive rod-shaped bacteria, 2 and during aerobic iced storage Shewanella putrefaciens and Pseudomonas spp. become the main producers of the volatile compounds associated with spoilage, 3±5 such as trimethylamine (TMA), ammonia and sulphides. TMA is particularly responsible for the unpleasant `®shy' odour of spoiled ®sh, and is a common index of seafood quality. 6 However, the changes in sensory characters often occur before ®sh products are hygienically spoiled. A current trend in food PACKAGING TECHNOLOGY AND SCIENCE Packag. Technol. Sci. 2001; 14: 267±274 DOI:10.1002/pts.559 Copyright  2001 John Wiley & Sons, Ltd. * Correspondence to: L. Piergiovanni, Universita Á degli Studi di Milano, Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, sez. Industrie Agrarie, Via Celoria, 2, 20133 Milano, Italy. Email: luciano.piergiovanni@unimi.it.