Control of histamine in Rihaakuru : emerging approaches : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy, Massey University, Palmerston North, New Zealand
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Date
2011
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Massey University
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Abstract
Rihaakuru is a cooked fish paste from the Maldives, consumed as a condiment
with rice and other food. The product is unique to the Maldives and there is no
information on the composition, characteristics and safety of this product.
Histamine contamination has been suspected due to symptoms sometimes seen
following consumption. This research established that Rihaakuru is a nutritious
and shelf-stable product. Rihaakuru is generally produced from poor quality fish
therefore presence of biogenic amines was suspected. This study confirmed that
Rihaakuru contained up to ten different biogenic amines, with histamine in excess
of 500 ppm. This may cause histamine poisoning with symptoms such as skin
rashes, vomiting and fever. The product examined in this study contained a few
weak histamine forming bacteria. Most of the histamine is likely to be produced
by bacteria in the raw fish. These bacteria are likely to die during the manufacture
of Rihaakuru. Histamine in Rihaakuru decreased by 30-70% during storage at -
80°C, 4°C and 30°C for 10 months. This showed that the histamine hazard in
Rihaakuru is unlikely to increase and may decrease during long term storage.
Traditional control of histamine in food is through refrigeration of raw material. In
the case of the fish used to manufacture Rihaakuru, refrigeration is not available
or limited. Histamine oxidizing bacteria and enzymes were identified as emerging
approaches to degrade pre-formed histamine. Histamine oxidizing bacteria
(Lactobacillus sakei [AGR 37, AGR 46, Lb 706] and Vergibacillus
halodonitrificans Nai18) tested in this study degraded histamine by 30-50%. The
histamine oxidizing enzyme, diamine oxidase (DAO) completely degraded 500
mg/L of histamine at pH 6 and salt 1% in buffer and in the tuna soup used to
manufacture Rihaakuru. A regression model was developed that predicted the rate
and amount of histamine removal by DAO under varied pH and salt
concentration. This model may be used to determine conditions that will reduce
histamine in other foods that have similar characteristics to the tuna soup used to
manufacture Rihaakuru.
Description
Chs. 2 & 3 have been published as: Naila, A., Flint, S., Fletcher, G. C., Bremer, P. J., & Meerdink, G. (2010). Control of biogenic amines in food-existing and emerging approaches. Journal of Food Science, 75(7), R139-R150. doi: 10.1111/j.1750-3841.2010.01774.x ; Naila, A., Flint, S., Fletcher, G. G., Bremer, P. J., & Meerdink, G. (2011b). Chemistry and microbiology of traditional Rihaakuru (fish paste) from the Maldives. International Journal of Food Sciences and Nutrition, 62(2), 139-147. doi: 10.3109/09637486.2010.515566.
Keywords
Fish pastes, Condiments, Fish sauce, Microbiology, Seafood poisoning, Histamine