Take care when using acid ingredients in a cure

[Wade]

A number of curing recipes (especially when immersion brining) call for the addition of acid ingredients, however if you are also using Nitrite/Nitrate in your cure then you need to take extra care - especially when mixing the brine. Common acidic ingredients include Cola, vinegar and Liquid Smoke.

Sodium Nitrite (the primary active ingredient of almost all Curing salts) is very unstable in acidic conditions and is readily broken down into Nitrogen Dioxide, Nitric Oxide and water. When this happens the Nitrogen Dioxide is sometimes visibly given off as a gas, causing the curing salts to "fizz". Once the Sodium Nitrite has decomposed it can no longer be effective in the cure.

The rate of breakdown of Sodium Nitrite increases with the acidity and literature indicates that at pH levels below 4.8 the breakdown rate increases exponentially. As some of the ingredients we use, when pure, are highly acidic we need to ensure they do not come into direct contact with the brine before they are diluted.

Acidity levels of some common ingredients

• Cola (Coke) - pH = ~2.5
• Vinegar - pH = ~3.0
• Liquid Smoke - pH = ~3 to 5 (depending on brand)
• Lemon juice - pH = ~2.3
• Apple juice - pH = 3.5 to 4.0
• Apple Cider - pH = ~3.0

By first diluting the acidic ingredients in the water of your brine the acidity is decreased. Below is the graph showing the results of a quick experiment I carried out to see the effects of dilution on the acidity of Cola. The cola in this test was Diet Coke.

In order to ensure that the acidity of the brine is above pH 4.8 is important that the Coke is diluted to below 1/4 strength (1 part Coke to at least 3 parts water) before the curing salts are added.

To test the effects of adding common undiluted ingredients to both Cure#1 and Cure#2, small amounts of each were added to both cures. To ensure that any effect seen was down to the Nitrite/Nitrate, they were first tested using pure salt.

Even after leaving it for 10 minutes there were no visible signs of a reaction

Immediately a few drops of the liquid smoke was added to the cure there was a distinct fizzing and the pungent smell of nitric oxide was detected.

After adding a few drops of vinegar to the cures there was initially no visible reaction, however after approximately 45 seconds there was a distinct fizzing and the pungent smell of nitric oxide was detected.

The test with the vinegar was then repeated using a 1:10 dilution in water. Even after 10 minutes there were no visible signs of a reaction.

Conclusion

When using acidic ingredients as part of a cure containing Nitrite it is important that care is taken to ensure that they do not come in direct contact with the cure before they are diluted. When making an immersion brine or an injection brine this is most easily achieved by well mixing all of the ingredients together before the addition of the curing salts.

Extra care should be taken when making an injection brine, as this is frequently prepared at 10x the final desired concentration. If using ingredients such as apple or pineapple juice in this type of cure it could easily result in high levels of acidity and to the breakdown of the cures active ingredients.