Ispitivanje promena ukupnog isparljivog azota u toku skladištenja hladno dimljene ribe

Abstract

Smoked fish, especially cold-smoked fish, is one of the most respected fish products. Since this is a "ready to eat" product, a particular attention is given to the packaging and changing during storage (bacteriological status, physical and chemical characteristics, sensory properties). The cold-smoked fish most commonly is packaged in the vacuum and modified atmosphere (MAP). The aim of this study was to evaluate the changes in the content of total volatile nitrogen (TVN) in the cold smoked fish packaged in a vacuum and MAP. For the experiment slices of cold smoked trout were packaged in a vacuum (O-I group) and three different modified atmospheres (O-II: 50% CO2+50% N2; O-III: 60% CO2+40% N2 and O-IV: 90% Co2+10% N2). The fish is stored after packaging at a temperature of 3 ℃, and the content of TVN was examined on days 0,7, 14,21,28,35 and 42. The content of TVN was determined by reaction of titration with hydrochloric acid in the presence of 3% of boric acid and methyl red and methyl blue as indicators. The content of TVN in samples of O-I group was from 3.52±0.24 ppm (on day 0) to 28.38±3.22 ppm (day 42), in O-II group from 3.02±0.06 ppm to 23.72±7.45 ppm, in O-III group from 3.07±0.09 ppm to 39.26±10.78 ppm and in samples of O-IV group TVN content was from 3.12±0.07 ppm to 36.15±4.47 ppm (respectively). During the 6 weeks of storage, the TVN in the samples of all four groups of cold smoked fish grew throughout the whole storage period, as can be seen from the regression equation for O-I, O-II, O-il and IV-O group: y=3.3019x+3.1481, y=2.6366x+4.6628, y=4.9603x-0.7559 and y=4.9762x-0.0561 (respectively). From the shown data it can be concluded that, based on the content of TVN as an indicator of spoilage, the least changes were detected in samples of O-II group, then O-I group, while the most pronounced changes were in the samples O-III and O-IV group of cold-smoked trout.