Bacteria in curing

[Lee]

My understanding of it is that internal muscle is considered to be safe to eat raw due to the very low bacterial load. Exceptions are fowl, usually said due to the exceptionally high levels of pathogens endemic in these species.
This really only applies to indervidual muscles though, any bacteria can work its way down the interfaces between muscles and bones (hence the bone sour issue), but this takes time, so with good meat Cattle, sheep, even Pork in this country (although this is being challenged by the French who have Toxoplasmosis issues with English Pork) are therfore safe to eat rare, as long as the suface contamination (from slaughter/bad hygiene in the food chain etc) is knocked back by either cooked or curing. There's still some bacteria present, but not enough of the right kind to cause food poisoning.

[Oddley]

I Understand Lee and Wohoki. This brings us back to the original question, If osmotic shock kills most bacteria on the meat surface and internally the meat has few bacteria what is converting the nitrate to nitrite.

I'm now banging my head against the wall. As we seem to have come full circle.

[Lee]

[color=indigo]If osmotic shock kills most bacteria on the meat surface and internally the meat has few bacteria what is converting the nitrate to nitrite.

color]

Halophillic Micrococci and Lactic Acid Bacilli.

[Wohoki]

Maybe there isn't any conversion inside whole cuts of meat, and the cure is added as a colour enhancer

[Oddley]

Wohoki nitrate has no effect on colour it has to be converted to nitrite first.

Lee what leads you to believe it is Halophillic Micrococci and Lactic Acid Bacilli. Are the bacteria salt and low temp resistant are they more likely to be inside the meat?

[Wohoki]

Quite right, I was being flippant.

just found this, "Dry curing of ham and bacon" about half way down the page:

http://www.continentalmeattechnology.co ... ws/news.pl


Nothing too new, but it's all grist to the mill.

[saucisson]

"Microorganisms generally inhibited by aw at this point

Micrococcus 0.870 eg Fermented sausage (salami)"

From: http://www.rhmtech.co.uk/science/water.htm

Does this mean micrococcus can survive in up to 13% saline?

Dave

[Vernon Smith]

Wow, a whole lot of chatter going on overnight (Solomon time) so I might be a bit late with some of my thoughts that have been made redundant by well informed postings by the three wise men Oddley, Lee and Dave. But here goes anyway. Dave, I endorse Oddley's request that you keep going so we can all poison ourselves with full cognisance of what we have done. Thanks for your definition of >10% Oddley. It is now clear to me how you work out percentages. Paul's brine recipe appears in his posting on Brawn dated 03 Nov 2005. Sorry if I confused you with my quaint calculations of salt and sugar percentages "ingoing" (1:6 = 16.66%). You calculate percentages of the total solution so I agree that 1:8 = 12.5%. I stand corrected, thanks. I confused the issue further by referring to 3% KNO3. What I meant was 3% by weight of the salt that I rounded down from 33.3 to 30g/kg. If I follow your corrected convention my formula should look like this

1 kg salt 12.4533%
1 kg sugar 12.4533%
6 ltr water 74.7198%
30g KNO3 0.3736% (ingoing 373.6mg/kg)

Total brine weight 8030g. My total KN03 is below your 500mg/kg figure because I followed a formula I picked up from the University of Missouri that specifies 7lb salt, 4lb sugar and 3oz KN03. 3 oz in 112oz salt is 2.67857% that I rounded up to 3%. Does this look ok to you? I have used it several times and I'm still alive but I see how dangerous mixing conventions can be.

Aaah, Lee. I wondered when pH would come out of the woodwork. Thanks! This topic is really bubbling now. Using KNO3 should lead to low pH acidic conditions less than the arbitrary neutral factor of 7 but do you think our solutions will get down to your factor of 4 to prevent nasties propogating. Indeed, are we sure that all the nasties are acidophobic? Some may be acidophlic or secondarily acidophytic. Any ideas? You've already fessed up to being a microbiologist, so SUFFER!!! But seriously, this is great stuff and we all luvya lots. Unfortunately the Sol. Is. are a bit far to come for our party this w/e but we will all be thinking of you.

E. Coli, Staph. A, and Salmonellae all seem to be off the troublesome menu but micrococcus aurantiacis raises another issue. Psychrotrophic or psychrophilic? The whole process of curing seems to be a balance between pH, temperature, salinity, oxygen and KNO3 and I'm not sure any definitive answers have appeared yet but I'm sure we're getting there. Hopefully my 8 deg C hypotheses fits. I was a wildfowler back in Essex for a number of years and I don't know what bacteria went to work tenderising my ducks and game birds when hung. Temperatures varied between 0 deg 15 deg C and nobody got poisoned but this may need another topic. Is micrococcus aurantiacis salt tolerant? Oddley mentions that 10% salt kills most bacteria. The Swiss site refers to micrococcacae working at high pH, which conflicts with the low pH that you suggest to prevent growth of Cl. botulinum. What do you reckon to this? Curiouser and curioser. Oddley also raises this. If we rule out micrococci what else could be converting the Nitrate? I'm a bit worried that an abundance of micrococci that on face value are goodies converting the NO3 could spoil my ham unless there are some other goodies, without the side-effects, helping out. I injected 650ml of cure into a 6.5 kg ham to kick start the curing assuming, hopefully, that there are some species of NO3 converters in the muscle. I also assume the brine will kill off any nasties on the skin. Cheers for now guys, I'll check for more good stuff tomorrow.
Regards,
Vernon

[Vernon Smith]

Dave, It's 23.40hrs Solomon time. I just picked up your facultative bacteria idea. Sounds good, what do you think Lee? I also think you have summed up the issue so far extremely well with your comment that using nitrate makes sure that botulism risk is eliminated. I'm too young and handsome to die yet.
Regards,
Vernon

[saucisson]

Further to my salinity post which Vernon will have missed as we posted at the same time, it appears that almost all bacteria used in "moderately halophilic" research were isolated from salted food stuffs or unrefined salt and include micrococci. I quote:

"Recently, 128 strains of moderate halophiles were isolated from bachalao (dried salted codfish) and from fresh cod and curing salt used in its preservation. "

from: http://mmbr.asm.org/cgi/content/full/62/2/504

The salted cod in question is 19% salt. They also say moderate halophiles are found on salted meat.

Dave

[Oddley]

1 kg salt 12.4533%
1 kg sugar 12.4533%
6 ltr water 74.7198%
30g KNO3 0.3736% (ingoing 373.6mg/kg)

Total brine weight 8030g. My total KN03 is below your 500mg/kg figure because I followed a formula I picked up from the University of Missouri that specifies 7lb salt, 4lb sugar and 3oz KN03. 3 oz in 112oz salt is 2.67857% that I rounded up to 3%. Does this look ok to you? I have used it several times and I'm still alive but I see how dangerous mixing conventions can be.

Potassium Nitrate is a reservoir for potassium Nitrite which is a botulism inhibitor. That being said after extensive research I use 500 mg/kg KNO3 for meats that are going to be cooked soon after curing finishes.

For meats that are going to be air dried I use from 700 mg/kg to 1250 mg/kg max depending on estimated air drying time.

As too the amount you use. As you said it ain't killed you yet.

As for ph if the meat is too acidic then this will kill any bacteria that convert nitrate to nitrite and the cure will fail

The meat should be used three days after slaughter and one should only use properly trimmed prime cuts. When available mature pigs 7-9 months old should be used. The meat of younger animals can be too light and soft, older meat can be too dry and dark. Three days after slaughter the ph-value should have dropped and stabilised from 7 to around 5.8 to 6.2. Different meat has different cure readiness. DFD meat (dark, firm, dry) has a low reediness. The ph-value remains high and the salt absorption is low. PSE meat (pale, soft, exudative) should also be avoided. Its ph-value is low and there is little chance to achieve good colour and taste. PSE meats readily accept salt and ham and bacon made from it always tastes salty.

http://www.continentalmeattechnology.co ... ws/news.pl

Thanks Wohoki handy link.

[Oddley]

After a look at saucisson post I found this link:

http://library.thinkquest.org/CR0212089/halo.htm

Which gives an easy to read overview of halophiles. They are shaping up as a good contender I think.

[Lee]

Blimey, we've been busy
From Vernons long post, All nasties that sporulate (eg Cl Boyulinum) will not grow below pH 4, at pH that low you only really get moulds and yeasts growing (with the odd exception, and non of these are food poisening risks, just food spoilage, which is less serious, unless it's your last sausage thats gone mouldy). For your ducks tenderising, I think this is less due to bacteria, and down to the hydrolysis of the muscle protein, which doesn't take bacteria (although they will speed things along).
But thats another story......
I'm backing my halophillic hypothesis for the nitrate/nitrite converters, simply because nowt else will grow in the salt, and the bacteria that are often halophillic are the ones you guys identified as the ones that are responsible for the Nitrate reduction.
Good this innit!

[Wohoki]

I think I'm going to leave this thread alone: I might go back to vegetarianism if I read any more


I shall lull myself to sleep tonight thinking of the thousands of generations of artisan butchers and cooks who knew nothing of microbiology, and yet who managed to make hams and sausage that I'd kill to be able to equal. Kill pigs, that is

[Oddley]

I think that is why we are all here. Most of us have lost the knowledge of the generations. So we have had to come here and sit at the feet of people who have the knowledge.

I first came to this forum about two years ago and was helped by parson Snows too the point where I could formulate brines on my own and had a basic understanding of the processes.

I have been learning ever since. I am at a stage now where I feel confident to advise other people. If my children want to learn how to cure I would be able to give them the knowledge to do so safely.

Maybe If your children are interested you will be able to start a new generation of artisan curers.