Comparative study of selected quality parameters during storage of fresh trout packed in vacuum and modified atmosphere. [Doctoral dissertation] | Uporedno ispitivanje odabranih parametara kvaliteta u toku skladištenja sveže pastrmke pakovane u vakuumu i modifikovanoj atmosferi. Doktorska disertacija

For experiment conducted in this dissertation, there were four groups of samples formed. The three groups of samples were packaged in different modified atmospheres: the first group (I) – 60%CO2+40%N2, the second group (II) – 40%CO2+60%N2 and the third group (III) – 90%CO2+10%N2. The samples of fourth group (IV) were vacuumed. During the three week storage of fresh trout on the temperature of +3 deg C, there was a bacteriological status to be followed as well as chemical and physical properties and sensory attributes. Based on the achieved results, it is concluded that the total number of microorganisms in all samples during the period of storage was significantly being grown. Growth rate of mesophilic bacteria was higher in samples packaged in vacuum and in high concentration of carbon dioxide (90%). Also, it is determined that the growth rate of total number of enterobacteria was lowest of all investigated microorganisms. The number of lactobacilli was much higher in samples packaged in high concentration of carbon dioxide. The way of packaging of fresh trout did not have so significant influence to the differences in determined number of anaerobic bacteria. Growth rate among all investigated microorganisms was highest in psychotrophic bacteria. Content of total volatile basic nitrogen increased in all samples during storage at +3 deg C. The result of research shows that there were significant changes of pH value during the storage of compared groups of samples. Measurements conducted by Torrymeter shows that torrymeter value decreased during the storage, which was particularly pronounced in samples that were packed in high concentration of carbon dioxide (90%). Based on sensory evaluation of trout freshness, depending on packaging method, shelf-life of fresh trout is 7 and 14 days, respectively. Packaging of fresh trout in modified atmosphere (groups I and II) has some advantages (better sensory attributes, lower content of total volatile basic nitrogen, smaller number of mesophilic bacteria) with regard to packaging in vacuum or in high carbon dioxide mixtures.