Saltpetre and Salt Prunella

On my Jane Grigson blog I recently completed a recipe, the 441^st, Smoking Meat. It wasn’t so much a recipe, more a bit of advice, and the advice was: don’t bother. However, I wanted to have a go at curing and smoking my own bacon, so took this as an opportunity, and because there was no recipe in English Food, I could do my own thing with respect to the recipe (see The Premise). All of Jane’s cured meats contain a combination of salt and saltpetre – also known as potassium nitrate – which has a bad rep these days because it has been implicated as a causative agent in diseases associated with eating processed meat products (more on that later). So, with my bacon, I thought it a good opportunity to see if leaving out the saltpetre would have any observable detrimental effects. SPOILER ALERT! My bacon is still completely fine three months after making it, stored at room temperature – there isn’t the merest trace of mould – and it got me thinking about its use in meat curing and processing and whether it needs to be included.

Just what is the function of saltpetre? Everyone does agree that the pink colour saltpetre gives the meat is attractive. However, there is certainly disagreement out there as to its efficacy in preservation. According to Jane Grigson saltpetre ‘no preservative value’¹ and Elizabeth David is of the belief that it is simply ‘the cosmetic of the preserved meat industry.’²

On the other side of the argument Larousse Gastronomique reckons it a ‘powerful bactericide [that] has been used since ancient times to preserve food.’³ Harold McGee concurs, adding that it is particularly effective against the bacteria that causes botulism.⁴

In conclusion: I don’t know what to think.

It seems that it hasn’t been used since ‘ancient times’ either; according to Peter Brears, ‘there appears to be no evidence for the use of saltpetre, sugar or smoking in medieval meat preparation, only salt.’⁵

Saltpetre can be found deposited naturally as veins in rocks – indeed, saltpetre literally means salt stone. Houses built on foundations dug into rocks containing the mineral sometimes find saltpetre can be found in crystalline forms in damp cellars. It is relatively rare, but it was in demand in the Middle Ages, not for its preserving powers but as an ingredient in gunpowder. In the sixteenth century a method of production was devised after an alchemist found that after boiling the water from urine the crystalline material left behind was highly flammable.⁶ With further refining of the process, urine was combined with faeces and lime on an industrial scale. It was said that the best urine for the job was ‘Bishops’ piss’; not because it was the urine of a holy man, but because of the large volume of wine that Bishops drank. The process even makes an appearance in the Canterbury Tales:

Chalk, quicklime, ashes and the white of eggs,

Various powders, clay, piss, dung and dregs,

Waxed bags, saltpetre, vitriol and a whole

Variety of fires of wood and coal.⁷

Everyone was well aware how saltpetre was made, and people – as you might expect – did not want to use a product derived from human waste in their food and continued to use saltpetre from natural sources at great expense. Today it is made from ammonium nitrate and potassium chloride.

When saltpetre comes into contact with meat, the nitrate part of the molecule reacts with haemoglobin (in the blood) and myoglobin (in the muscle) to form a nitrite, which reacts further to form nitric oxide. It is the nitrite and globin molecules reacting that form the pink colour. The products of reduction are stable away from oxygen in the air, however if one takes a slice from the meat to reveal the pink meat within, the nitrites oxidise back into nitrates and the meat loses its rosy tinge.

Some recipes ask for salt prunella, which is simply saltpetre that’s been formed into little balls and dissolve at a slower rate that regular saltpetre. It also contains a small proportion of potassium nitrite to help kick-start the chemical processes in the meat. Again sources disagree as to the truth of this.

Saltpetre is used in very small amounts – when I used it in the past, I used approximately a teaspoon or two to every 500 g salt. You can purchase it on the internet, but it is much better to buy salt mixes for curing that contain salt and nitrates already mixed and measured.

This brings us to health – this chemical which is added in small amounts is getting the blame for causing heart disease and bowel cancer in those who eat processed meat products. Well, there is certainly a correlation between consumption of processed meats and cancer. But let’s not jump on nitrates as the causative agent: correlation is not causation, after all. Remember when red wine was supposedly good for your heart? It wasn’t true – there was a correlation, sure, but only because folk who drink red wine tend to be middle class, and therefore tend to also exercise regularly and eat a heathier diet. Nothing to do with wine.* I suspect there is something similar going on with nitrates: they are used in processed meats, which are cheap and much more likely to be consumed by poorer families, who in turn, are less likely to eat fewer fresh fruit and vegetables, and less likely to own a gym membership. As it turns out, nitrates may actually be beneficial in that they help lower blood pressure.

The jury then is still out. And in the case of my own homemade, nitrate-free bacon, leaving out the nitrates hasn’t caused the meat to go bad, and it stayed relatively pink too. Removing it might not improve the nation’s health, but at least it removes a chemical that’s been produced from nasty chemicals which can only be good for the environment.

Do you have any thoughts on the matter? Let me know them in the comments.

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*In fact it has been demonstrated that there is no safe minimum alcohol levels – it’s all bad, sorry!

References

1.           Grigson, J. Charcuterie and French Pork Cookery. (Grub Street, 1969).

2.           David, E. Spices, Salt and Aromatics in the English Kitchen. (Penguin, 1970).

3.           Larousse Gastronomique. (Hamlyn, 2001 edition).

4.           McGee, H. On Food and Cooking: The Science and Lore of the Kitchen. (Allen and Unwin, 1984).

5.           Brears, P. Cooking & Dining in Medieval England. (Prospect Books, 2012).

6.           Beach, H. By the Sword Sundered. (Authorhouse, 2014).

7.           Chaucer, G. The Canterbury Tales. (Translated by Nevill Coghill, Penguin, 1951).