The older cheesemakers will tell you that you should not renew your brine but simply add more salt as required, and they have very sound reasons for this.
However; in today's climate of hygiene hysteria it is advisable to change you brine solution periodically.
When you first make up a fresh solution the pH. of this will be around pH. 7.00. (Neutral).
Now, the average pH. of any cheese, which you are going to float in this solution, will be around pH. 5.00.
When you use this new bath the pH. of the brine will try to level out and this will increase the pH. (in other words, reduce the acidity) of your cheese. This will lead to many possible defects:
Usually they will manifest themselves most visibly in rind defects.
You will feel a greasiness of the rind at first.
This will develop into areas of sticky and discoloured patches, with the discolouration varying from straw colour to bright orange, red or brown.
The surface will be prone to show growths of the black or grey mucor molds (poille de chat).
The body of the cheese will be weaker and softer than desired.
The low acidity will favour the growth of spoilage organisms, flavour will suffer and the keeping quality of the cheese will be reduced considerably.
No problem:... there is an answer to this. As any Dutch Gouda maker can tell you.
You simply add acid to the fresh solution and from there on both the brine and the cheese are happy.
This can be done with lactic acid but the cost is a little high.
I use the same acid as the cow does in it's digestive system: hydrochloric acid (which you can buy from a chemists / local pharmacy).
Right, let's make up a brine bath.
You need a 20% solution. We will work with 100 litres, just to make things easy, but you will make up what is required for the amount of cheese you usually make per batch.
1 litre of water weighs 1 kilo.
100 litres of water: 100 kilo. So, for a 20% solution you will need 20 Kilo of salt. (If you work in pounds and ounces: a Gallon weighs around 10 lb..).
I usually find that I need one for the pot as well. Particularly if one uses sea salt as this is not so purified.
Dissolve the salt in the water. It will take some time so leave it to soak before you really do a lot of stirring.
Once it is dissolved you need to measure both the salt solution and the pH.
A very fresh egg will float in a 20% solution and this is a very reliable method in home-production but what you really need is a Brine weight.
You simply float the weight and read the percentage that is marked in gradients on the side. Then add either more salt or more water as may be necessary.
The pH. can be measured with a pH. Meter ... expensive and unreliable for the small producer.
What you need is a pack of pH.Dip papers. (litmus paper). You simply dip one of these strips into the solution and then read the pH. off against the colour chart on the packet.
The reading is going to be far too high, so now reduce it.
Put a couple of litres of water in a jug and add the equivalent of 3 or 4 teaspoons of the acid to it. (if you are using Lactic acid you will need a good deal more) Pour about half of this into the bath and stir for a few minutes. Then take another Ph. reading.
Continue to add until you have a pH.of 5.00.
You should be using the solution at a minimum of 15C (60 Fahrenheit) and maximum of 20c. 18c is the norm. Below this temperature the salt will not be properly absorbed and, the low temperature will restrict or kill many of the flavour producing organisms in your cheese. Store it at room temperature and keep it covered and clear of any cheese particles and it will be fine for the whole season.
When you use this bath the cheese will absorb salt and reduce the solution %.
Every time you put fresh cheese into the solution you must give them a liberal sprinkling of salt to compensate for this. The cheese should be flipped over in the brine halfway through the brining period, and sprinkled again with salt or you will find that the upper side of the cheese will soften as it ages because it will retain more moisture.
Measure the salt solution % occasionally by all means, but once you have a little experience this will only be necessary about once a month.
I keep a very fine mesh gadget to hand (a plastic swimming pool skimmer) and skim the surface of the brine shortly after each use.
This removes any cheese particles and helps to keep the solution clear.
Periodically you need to filter the solution thoroughly.
I do this by either pumping or bucketing it from one container to another and back again.
You can make up a simple yet effective filter by lining a basket or colander with cheese muslin and passing the solution through this.
This gives you the opportunity to clean the bath and surrounding area. Do not allow a smear of slime to develop on the sides of the bath above the water line... this will be fat and bacterial growth.
A note on pH. If you do not set the pH. of your brine solution it will gradually level itself out as it takes acid from your cheese so, after a period of time the pH. will be correct. However, this will depend on how often you use it and how much cheese you float in it so it will take some time and in the meantime you will be reducing the acidity of your cheese. This is why the older cheese-makers did not change their solution.... in most cases, for many, many years.
I think that will about do you. James.