Weight Loss Query

Postby Oddley » Tue Jun 03, 2008 12:43 pm

I think those of you who want to cure, and or smoke fish, could do a lot worse than read:

Processing Parameters Needed to Control Pathogens in Cold Smoked Fish

For the scientists among you, who want to cheaply find the salt in cured fish.

Quick Determination of Water Phase Salt Content of Smoked Fish
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Postby saucisson » Tue Jun 03, 2008 3:04 pm

Excellent finds Oddley, thanks.

Phil, Read the section on "Control of Food Safety Hazards during Cold-Smoked Fish Processing " Section 6.1 onwards from Oddley's first link
Does that answer the question?

The bottom line seems to be that if you achieve 3.5% Water Phase Salt your fish will be safe (I think). And although weight loss is a factor it is not the sole determinant. And from the other link:

WPS =

%salt x 100
________________

%moisture + %Salt

Dave

PS an alternative, less detailed link to determining WPS may be found at :
http://seagrant.oregonstate.edu/sgpubs/ ... 00003.html
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Postby Batman » Tue Jun 03, 2008 3:50 pm

Thanks Oddley, that is a fantastic find. Should be a sticky (do we have stickies on this forum?). I will pass on the chemical testing which I don't think is practical for home curers.

I've quickly read through the document and whilst I was initially worried about the whole process, I now feel much more confident about the process I (and others here) have used. I will re-read and post my views on the key issues for home curers/smokers.

Dave, my initial reading of the document is that the 3.5% seems to be a recommendation, but not necessarily a must do depending on a whole lot of other issues. Nevertheless, it is something I will try and aspire to. Do you or Oddley have any thoughts on how we can achieve this on an input basis ie would 35g of salt per 1kg salmon be a reasonable starting point, assuming we can achieve equilibrium in a few hours?

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Postby saucisson » Tue Jun 03, 2008 4:26 pm

I will make Oddley's post into a sticky. Oddley has a much better feel than me for these things so I'll let him comment first.

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Postby wheels » Tue Jun 03, 2008 4:57 pm

Dave

I need to inwardly digest all this - I think it answers the question, by the way, thanks Oddley for posting the link.

It's interesting to note the references to the use of Sodium Nitrite in the smoking of fish in the US. Has anyone experience of this?

Trouble is I'm no nearer being able to know whether the product is safe as I don't realistically stand any chance of being able to determine WPS.

I guess the answer to all this is to err on the salty side, without it becoming unpleasant, smoke to taste, and then dry to the required level of weight loss.

Batman - I look forward to reading your conclusions.

Phil
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Postby Oddley » Tue Jun 03, 2008 5:03 pm

Hi Batman

I don't think it is quite as simple as adding dry rub 3.5% salt of the whole fish. As it is 3.5% salt in the moisture of the fish. As described from this formula in the Quick Determination of Water Phase Salt Content of Smoked Fish .pdf


COMPUTE WATER PHASE SALT CONTENT

% SALT x 100
---------------------------- = WPS
% MOISTURE + % SALT


So dry curing is just going to be guesswork. Whereas if you use an immersion brine cure to equalisation, then if calculated right, will give an equalisation in the water of the fish 3.5% salt. Does this make any sense?
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Postby Batman » Wed Jun 04, 2008 2:00 pm

Thanks Oddley, I didn't think it would be as simple as I had hoped. Shame, but if you come across anything re salt take up of salmon using dry cure please pass it on.

Logically, it would seem that an immersion to equalisation of 3.5% would seem to be one way, though I suspect that to use such a weak brine would require a very long time to equalisation. Again I would be interested if you come across anything showing salt content as a function of time in say an 80% brine (or similar).

In any event, the more I read the document, the less I become convinced about the 'magical' 3.5% figure quoted. My impression is that the microbiologists would prefer 5%+ but this would not be acceptable to consumers (therefore producers). There doesn't seem to be any analysis of the impact of varying salt concentration levels. But I would welcome your thoughts on this. I am inclined to think that this is not a serious issue for home producers provided other things are ok (see next post).

Having read the FDA paper, I am content with the general process described on this forum.

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Postby Batman » Wed Jun 04, 2008 2:04 pm

Personal view of FDA document on Pathogens associated with Cold Smoking Fish as it relates to home curers/smokers ie occasional producers..

Document lists 4 pathogenic issues: listeria monocytogenes, clostridium botulinum, biogenic amines and parasites.

Listeria monocytogenes
Occasional sporadic outbreaks in smoked mussels and cold smoked trout, no reported cases in salmon.
Capable of growing in normal salt/temperature combinations but in �naturally� contaminated products growth is slow. Therefore good hygiene in processing is the major hurdle.

Clostridium botulinum.
Widespread prevalence but incidence is low. Anaerobic. No reported outbreaks of botulism arising from cold smoked fish.
Inhibited by low temperature, therefore try and keep storage temperatures as low as possible.
Because the bacteria is anaerobic, vac packing could be an issue.

Biogenic Amines
Not generally seen as an issue for salmon.

Parasites
Pre frozen fish is suggested, not sure if domestic freezers get down to the required temperature level. �Smoke� will kill surface parasites but not any inside the flesh. Interestingly, Farmed salmon fed on pellet food should have no parasites as the parasites are passed up the food chain.

Key Issues
Try to obtain good quality fish.
Keep well chilled
Process the fish under good hygiene conditions.
Try to achieve 3.5% salt content in finished fish*
Don�t smoke for more 24 hours.
Keep the finished product chilled if to be eaten in days (as opposed to weeks), freeze for longer keeping periods.

* Difficult to establish why 3.5% is the �magic� figure. In general the higher the salt content the less pathogenic problems but poor eating quality. The 3.5 % level seems to be a compromise figure but very difficult to see any specific scientific basis, and may not be an issue for home curers/smokers who either eat their fish within days or freeze for future use. Testing for final salt content would seem to be impractical for home producers, more useful would be some sort of input calculation.

These is my personal precis of the FDA document, I am not a microbiologist or biochemist, however, the key issues are ones I will be trying to follow for any future fish that I cure/smoke. If you have any concerns you must refer to the original document.

I would welcome any comments/discussion.

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Postby Oddley » Wed Jun 04, 2008 2:54 pm

Batman,

I believe curing fish is exactly the same as curing meat, the document "Processing Parameters Needed to Control Pathogens in Cold Smoked Fish" has confirmed that for me. Commercial ham, usually has a residual salt content of between 3 - 3.3%, is this a coincidence. I think not!

The salt content of the fish is important so is the PH, as is the water activity (AW), or how dry it is. We don't want to use vinegar to drop the PH, so all we have left, is to use chemicals to control the bacteria ie: nitrite, or dry the fish so that Clostridium botulinum can't grow. That's why at the start of this discussion I suggested an AW of less than or equal too 0.85.
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Postby wheels » Wed Jun 04, 2008 4:22 pm

The use of Cure #1 (Sodium Nitrite) seems an acepted practice in the 'curing' stage of smoked fish in the US but, I have never come across any mention of in GB.

Does anyone have any experience/knowledge of this?

Phil
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Postby saucisson » Wed Jun 04, 2008 4:24 pm

For the science behind the 0.85 figure look here:

http://www.foodscience.csiro.au/water_fs.htm

Noting in particular:

The risk of food poisoning must be considered in low acid foods (pH > 4.5) with a water activity greater than 0.86 aw.

Our friend clostridium actually gives up at 0.93, but some of the others are hardier. I had access to a nice table showing which ones they were but the site is currently unavailable, I think it was the Staphs.

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Postby Batman » Wed Jun 04, 2008 6:07 pm

Oddley,
I've never come across Aw before so you will have to bear with.

I think the requirements of commercial producers and ad hoc home producers are quite different so I think that what they do needs to be considered with the differences in mind.

I don't know whether the residual salt content of commercial ham is coincidence or not, but I am much less sure than you.

Clostridium botulinum is inhibited at Aw 0.97 and the pH of smoked fish is between 6.3 and 7 according to the FDA report. given that Aw distilled water is 1.0, raw fish will be less than 1 and that we are removing moisture through salting, I would guess that we must be close to the 0.97, maybe even below it. (Would you believe milk is shown as being Aw 0.97)

The FDA report also lists some research (among a whole lot) which shows that there was no toxin in cold smoked trout with a salt content of 1.7% after 4 weeks stored at 4C (Cann and Taylor 1979).

Wheels
The FDA report notes that nitrite is not allowed in (commercial?) smoking in the EU but ok in the US.

Saucisson
If you search Wikipedia for 'water activity' it gives quite a bit on the subject plus a table of microorganism inhibit levels:

Clostridium Botulinum 0.97
Listeria Monocytogenes 0.92

I think the common sense points I identified from the report are a good basis for home curers/smokers.

I never expected to learn so much when I started sausage making!

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Postby wheels » Wed Jun 04, 2008 6:18 pm

Batman wrote:The FDA report notes that nitrite is not allowed in (commercial?) smoking in the EU but ok in the US.



Yes, I've come across it a couple of times in US docs. It may be banned in UK commercial production but for the home smoker...

That's why I ask whether anyone has experience/knowledge of it - maybe one of our US forum members?

Phil
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Postby Oddley » Wed Jun 04, 2008 9:09 pm

Batman,

I think it may be better to be sure of the AW, than guessing. If you think the same, then I show how to get a reasonable reading of AW
Here.
I have suggested an AW of 0.85, because I know this is a reasonably safe level. I'm sure those of you that cure fish could do with more closely matched info to the product produced. I doubt I will ever do smoked salmon, so may I pass on the torch to who ever is willing to take it up.
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Postby Batman » Thu Jun 05, 2008 10:15 am

Thanks Oddley, I intend to do some meat air dry curing so will probably buy a hygrometer in the near future. The majority of instruments I've quickly looked at have quite poor sensitivity (+/- 5%) so not sure how useful the information would be for home curing fish.

I don't intend doing a lot of fish curing and the FDA document has given me sufficient confidence that choosing good quality fish, having good hygiene practices and subsequently freezing the product will minimize any risk to that of normal domestic kitchen level. However, out of interest I will try your test for Aw when I get a hygrometer and report the results on the board for information.

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