Title: Shelf life of herring (Clupea harengus) kept at different temperatures

Final project
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Supervisors: Heida Palmadottir


The objective of this project was to learn about the main types of evaluation of quality of fish, and quality changes during different storage condition. Atlantic herring (Clupea harengues) was chosen as a similar fish species to mackerel, the important fish species in Cape Verde. Herring was stored in ice and kept for 9 days, at +1, 5ºC and -1, 5ºC. Quality changes during chilled and superchilled storage was evaluated by sensory analyses using Quality Index Method (QIM) and Torry score, by microbiological analyses; total viable counts (TVC), hydrogen sulphide (H2S) producing bacteria and by chemical analyses of total volatile bases (TVB) and trimethylamine (TMA). The modified QIM scheme for herring had higher correlation (R2=0,914) than published QIM schemes with correlation of R2 =0,740. Storage time could be predicted to approximately 8 days in ice. During the chilled and superchilled storage of herring very low number of microorganisms was detected. On day 9 TVC and H2S – producing bacteria values were log 4.3 and log 4.1 (+1,5oC) and log 5 and log 4.4 (-1,5oC) respectively. Low levels of TVB-N and TMA were found during the storage time. The reason for these unexpected results was probably due to temperature fluctuation. There was no significant difference between the two storage groups.

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