Fish sauce fermentation technology using New Zealand raw materials : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) at at Massey University, New Zealand
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Date
2025
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Massey University
Figures are reproduced with permission
Figures are reproduced with permission
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© The Author
Abstract
Despite abundant raw material, industrial fish sauce production is absent in New Zealand, partly due to a paucity of prior research on how well cold-climate South Pacific fish ferment under temperate conditions with local solar salt. The present study investigates the effect of different fish sauce fermentation conditions using New Zealand raw materials (Hoki and snapper heads and frames as well as green-shell mussel), New Zealand solar salts (stoved and unstoved salts) and different temperatures on volatile fatty acid (VFA) production as well as bacterial composition and diversity. Four different fermentation set-ups were conducted to investigate different aims:
1. Laboratory scale fermentation to investigate the influence of different variables (including seafood material, type of salt and temperature) on fermentation.
2. Pilot scale fermentation to investigate the influence of sampling depth on fermentation.
3. Shell-on mussel fermentation to investigate the influence of mussel shell on mussel fermentation
4. Snapper fermentation with mussel shell added to investigate the influence of mussel shell on snapper fermentation.
Four VFA were quantified in all fermentation in this study: acetic acid, propionic acid, butanoic acid and 3-methylbutanoic acid. Butanoic acid was detected only in fermentations with unstoved solar salt regardless of seafood material and fermentation temperature. The presence of butanoic acid exclusively in unstoved fermentations may be associated with the presence or abundance of bacterial groups associated with butanoic acid production in these fermentations.
The current study found that VFA concentrations generally increased as the fermentation time increased. Salt type had more influence on VFA production than any other single variable including seafood material used, fermentation temperature and sampling depth.
It was also revealed that seafood material had more influence on bacterial compositions than any other variable and seafood material appeared to be the primary determinant of the predominant bacterial family groups for the fermentations (Hoki paste – Micrococcaceae and Moraxellaceae; snapper paste – Carnobacteriaceae, Moraxellaceae and Pseudomonadaceae; and mussel paste – Flavobacteriaceae, Moraxellaceae, Paracoccaceae, Pseudomonadaceae and Roseobacteriaceae). Halobacteriales were found only in unstoved salt fermentations suggesting that salt type may be responsible for these results. However, this postulate could not be validated since insufficient intact nucleic acid could be recovered from the salts used to generate adequate bioinformatics information.
Shell-on mussel and snapper plus shell fermentation revealed that the presence of mussel shell was associated with high pH in fish sauce fermentation, an observation not previously reported. However, no significant difference in pH was found in fermentations with different shell contents. In pilot scale snapper fermentation, sampling depth did not have a major influence on VFA production. However, sampling depth may influence the growth of some bacterial families to become the predominant groups by the end of the fermentation.
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Keywords
Fish sauce fermentation, seafood by-products, Hoki (Macruronus novaezelandiae), Snapper (Pagrus auratus), Green-shell Mussel (Perna canaliculus), New Zealand raw materials, stoved salt, unstoved salt, Fermentation, Fermented fish, Seafood, New Zealand, Sauces