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Aeromonas spp. are regularly present in water, and in some cases, they cause diseases in fish and amphibians. Humans are infected by ingestion of the bacteria through contaminated food or water. Objective of this paper was to examine the presence of Aeromonas species in trout samples and to investigate the biochemical characteristics of isolated strains. In microbiological analysis of 120 trout samples, 12 bacteria strains of Aeromonas genus were isolated, of which seven (58.3%) belonged to strains of A. hydrophila group 1, and five (41.6%) to strains of A. hydrophila group 2. By biochemical characterization of isolated strains it was established that they were oxidase positive, catalase positive, arginine positive, ornitin positive, H2S negative, urease negative, tryptophan desaminase negative, gelatine negative, fermenting mannitol, inositol, rhamnose and saccharose, the are mobile, hemolytic and hydrolyze starch. In regard to other biochemical characteristics, it was established that 11 (91.7%) of 12 studied strains of A.hydrophila had β-galactosidase, they were citrate and indole positive, sorbitole negative, arabinose positive, produce NO2 and reduce it to N2. Also 10 (83.3%) of 12 studied strains were Voges-Proskauer positive and melibiosis negative, whereas eight (66.7%) of 12 studied strains had lysine-decarboxylase positive reaction and were amygdalin positive. In 58.3 % of strains (seven of 12 strains) were established to ferment glucose., Aeromonas spp. redovno su prisutni u vodi, i u izvesnim slučajevima, uzrokuju oboljenje riba i vodozemaca. Čovek se infi cira ingestijom ovih bakterija putem kontaminirane hrane ili vode. Cilj ovog rada bio je da se ispita prisustvo Aeromonas vrsta u uzorcima pastrmke i ispitaju biohemijske karakteristike izolovanih sojeva. Mikrobiološkom analizom 120 uzoraka pastrmke, izolovano je 12 sojeva bakterija iz roda Aeromonas, od kojih je sedam (58,3%) pripadalo sojevima A. hydrophila grupa 1, a pet (41,6%) je pripadalo sojevima A. hydrophila grupa 2. Biohemijskom karakterizacijom izolovanih sojeva utvrđeno je da su oksidaza pozitivni, katalaza pozitivni, arginin pozitivni, ornitin pozitivni, H2S negativni, ureaza negativni, triptofan dezaminaza negativni, želatin negativni, fermentuju manitol, inositol, rhamnosu i saharozu, pokretni su, hemolitični i hidrolizuju skrob. Od ostalih biohemijskih karatkeristika utvrđeno je da 11 (91,7%) od 12 ispitanih sojeva A. hydrophila poseduje β-galaktosidazu, zatim citrat i indol su pozitivni, sorbitol negativni, arabinoza pozitivni, produkuju NO2 i vrši njegovu redukciju do N2, zatim da je 10 (83,3%) od 12 ispitanih sojeva Voges-Proskauer pozitivno i negativno na melibiozu, dok je osam (66,7%) od 12 sojeva dalo lizin-dekarboksilaza pozitivnu reakciju i bilo je amigdalin pozitivno. Kod 58,3% sojeva (sedam od 12 sojeva) utvrđeno je da fermentuju glukozu.

This work presents the results of comparative examination of trout freshness using sensory analysis and measuring electrical characteristics of fish skin by torymeter. Trout stored by freezing, and in the air at temperature from +4ºC to +6ºC was examined. Statistically significant difference in the total sensory evaluation expressed as index of quality between trout stored by freezing and stored in the air, was found after four days storage. Total sensory evaluation (expressed as index of quality) above ten, showed significant loss of fish freshness what was noticed in fish stored in the air after five days, and in fish stored by freezing after eight days of storage. Statistically significant difference was determined between average values of torymetric number of fish stored in the air and by freezing, after thee days of storage (p lt 0.01). The fall of torymetric value below ten means significant loss of fish freshness, what in fish stored in the air was recorded after eight days of storage., U radu su prikazani rezultati uporednog ispitivanja svežine pastrmke senzornom analizom i merenjem električnih osobina kože ribe torimetrom. Za ispitivanja je korištena pastrmka koja je čuvana poleđivanjem, odnosno u vazduhu pri temperaturi od +4ºC do +6ºC. Statistički značajna razlika u ukupnoj senzornoj oceni izraženoj kao indeks kvaliteta između pastrmke skladištene poleđivanjem i skladištene u vazduhu utvrđena je četvrtog dana čuvanja. Ukupna senzorna ocena (izražena kao indeks kvaliteta) veća od deset, označava značajan gubitak svežine ribe što je kod ribe skladištene u vazduhu utvrđeno petog dana, a kod ribe skladištene poleđivanjem osmog dana skladištenja. Između prosečnih vrednosti torimetrijskog broja ribe skladištene u vazduhu i poleđivanjem utvrđena je statistički značajna razlika počevši od trećeg dana skladištenja (p lt 0,01). Pad torimetrijske vrednosti ispod deset označava značajan gubitak svežine ribe, što je kod ribe skladištene u vazduhu zabeleženo petog dana, a kod ribe skladištene poleđivanjem osmog dana skladištenja.