Dear Grey,
Many years ago I was involved in a similar problem. Old regulations did not
recognized that TVB-N in canned fish would be higher than the TVB-N content
of the raw material, because they did not have into account the thermal
decomposition of TMAO. This in the past was a common reason for rejection of
canned fish (high TVB-N). We published a research note on this:
Production of nitrogen volatile basis on fish during the canning process
Yeannes, M.I.; del Valle C.E. and Lupin, H.M.
Rev. Agroquim. Tecnol. Alim., 23(4), pp 585-590, 1983 (Spain) (20 years, my
God!!)
(the paper is in Spanish with a short abstract in English)
Eventually regulations changed in the sense that TVB-N was not taken any
longer as a reliable uality/safety index for canned fish.
We did not measure TMAO, because this was not of regulatory interest,
however, we noticed that the strong (time/T) the treatment the large the
production of TVB-N (we included this observation in the paper).
I remember that one of the observations from people in regulatory bodies to
this paper was that we had not identified a "final" value for TVB-N for the
cooking/ sterilization process (there is a reduction of TMAO also during
cooking before sterilization). Of course this would depend of the initial
content of TMAO, that is different in each specie and has variations within
the same specie, we answered.
Nevertheless, we performed some experiments cooking and retorting till to
get a plateau in the TVB-N (which could indicate a total depletion of TMAO),
but for the species we worked with, this plateau corresponded to t/T stories
that were well above the commercial ones for commercial sterilization. We
never published such a result, but from that I would be tempted to suggest,
that in (at least some) commercial canned fish, there is still some
remaining TMAO. You could replicate this experiment very easily for your
conditions.
Kind regards.
Hector M. Lupin
Senior Fishery Industry Officer (Quality Assurance)
Fish Utilization and Marketing Service (FIIU)
Fishery Industries Division (FI)
Fisheries Department, FAO, Room F 606
Viale delle Terme di Caracalla 00100 Rome Italy
Tel + 39 06 570 56459
Fax + 39 06 570 55188
E-mail: hector.lupin@fao.org
-----Original Message-----
From: Peter Howgate [mailto:phowgate@rsc.co.uk]
Sent: 07 February 2003 23:57
To: D. Grey Allen; seafood@ucdavis.edu
Subject: Re: Student needing help!!!
Dear Grey
A paper I have, (there might be others), on the topic of breakdown of TMAO
during canning is:
Hughes, R.B., 1963, Some effects of heat_processing on herring. In: Food
Science & Technology, Proceedings of the first International Congress of
Food Science and Technology, London, September 18-21, 1962, Volume III,
Quality, Analysis and Composition, J.M. Leitch, ed, Gordon and Breach
Science Publishers, pp 477-489.
In it Hughes writes:
"Trimethylamine oxide in herring is reduced during heat_processing (Ronold
and Jakobsen, 1947), but it was further established (Hughes, 1959) that
dimethylamine as well as trimethylamine is a major breakdown product, being
formed in the approximate proportion of 1 mole of dimethylamine to 2 moles
of trimethylamine. This suggested that trimethylamine oxide is decomposed in
two ways, namely: (CH3)3NO to (CH3)N + O, and to (CH3)2NH + HCHO. Both these
reactions proceed when trimethylamine oxide is heated in the presence of
reducing agents (Dunstan and Goulding. 1899), and Vaisey (1956) recently
demonstrated that the oxide is reduced by both the above pathways even at
room temperature, in the presence of naturally_occurring reducing agents.
Ota (1958) has confirmed this by showing that the thermal breakdown of
trimethylamine oxide is accelerated by certain amino acids such as cysteine,
while Hattori and Hasehe (1934) had previously demonstrated the production
of both dimethylamine and formaldehyde in heated squid extracts."
The citations are:
Dunstan W. R., and Goulding, E., J. Chem. Soc. (7.) 75, 792 (1899)
Hughes, R. B., J. Sci. Food Agric. 10, 431 (1959).
Ronold O.A. and Jakobsen F., J Soc Chem. Ind., 66. 160 (1947).
Vaisey, E.B., Canadian J. Biochem. Physiol., 34, 1085 (1956).
The paper has a figure showing production of TMA and DMA over 5 hours of
heating herring at 120ºC which comes from the Hughes (1959) paper, but I do
not have a copy of this.
The phenomenon of 'greening' in canned tuna is related to the TMAO content
of the raw tuna. The papers on this topic that I have give values for the
TMAO content of raw tuna, but not of the canned product.
It might be worth following up the Hughes papers in Science Citations Index
for papers citing them, and also ASFA and/or FSTA for relevant publications.
You can always check on TMAO loss in your products as it is easy to measure
TMAO if you are going to measure volatile bases. Measure the bases in an
extract before and after reduction with titanous chloride.
Peter Howgate
_____ Original Message _____
From: D. Grey Allen
Sent: Wednesday, February 05, 2003 10:59 PM
Subject: Student needing help!!!
I am a student at NC State University, and I am looking into inoculating a
sterilized (autoclaved) fish tissue based media (either tuna and/or
mahi_mahi) with bacterial isolates and determining the rate they produce
volatile basic nitrogens. My question is, would there be enough TMAO and
other substrates left, after autoclaving, to interact with bacterial enzymes
to produce volatile basic nitrogens. Any references that illustrate the
answer to this question would be appreciated.
Thank you,
D. Grey Allen
----- Original Message -----
From: D. <mailto:dgallen2@unity.ncsu.edu> Grey Allen
To: seafood@ucdavis.edu <mailto:seafood@ucdavis.edu>
Sent: Wednesday, February 05, 2003 10:59 PM
Subject: Student needing help!!!
I am a student at NC State University, and I am looking into inoculating a
sterilized (autoclaved) fish tissue based media (either tuna and/or
mahi-mahi) with bacterial isolates and determining the rate they produce
volatile basic nitrogens. My question is, would there be enough TMAO and
other substrates left, after autoclaving, to interact with bacterial enzymes
to produce volatile basic nitrogens. Any references that illustrate the
answer to this question would be appreciated.
Thank you,
D. Grey Allen
This archive was generated by hypermail 2b29 : Mon Feb 17 2003 - 01:59:21 PST