4 replies to this topic

[Maxiak]

Hello,

 

  I work for a company who will occasionally add citric acid or 400GPL lemon juice concentrate to vegetable juices in order to regulate pH. We have a citric acid calculator that we currently use but the specifics are a little vague and I would like to make sure that the calculations are accurate. Is there a standard calculation used in the industry for the addition of citric acid or lemon juice concentrate to juice? If you could please share the calculations or point me in the direction of any resources that would be much appreciated.

 

Thank you!

[Marloes]

Hi Maxiak,

 

Just to check. You want to be able to calculate how much citric acid/lemon additive to add to your vegetable juices to regulate it's pH to a set point?
Do you accurately know the current pH of your vegetable juices? And this know the exact amount that it should be decreased?

[Maxiak]

Hello,

 

  Yes, that is correct. I would like to be able to calculate how much citric acid/lemon juice to add to vegetable juices to be able to decrease pH. We do measure pH with a calibrated pH meter, however, the calculation we are currently using is only taking into account the change in % citric acid on the juice. Right now, the calculator we have is set up as follows:

The current brix and acidity of the juice are entered into separate cells of a workbook.

The current weight of the product in the tank is entered into another cell.

The operators will enter a sort of guess and check weight (in pounds) of the 99.5-100.0% anhydrous citric acid in a separate cell and then a calculation is performed to see how it increases the citric acid %.

Once the desired citric acid % of the juice is reached, they will then use that corresponding weight of citric acid entered to increase the % citric acid to the desired level and add that amount to the product in the tank.

Although ultimately we are adding the citric acid to lower the pH, the calculator we are using is more so taking into account the affect the citric acid addition will have on the citric acid % in the juice itself, rather than figuring how much citric acid to add in order to reach a certain pH. In summary, we perform the calculation, see how it affects the acid %, add the desired amount of citric acid, and then measure both the pH and citric acid % using a pH meter and auto titrator, respectively, after the acid addition.

I would just like to know if there is a standard way of doing this as it doesn't seem like our method is very user friendly and maybe not accurate.

What I would ultimately like to have is a calculator to show how much citric acid to add to the juice in order to reach the desired pH level, rather than entering random weights in the calculator and then seeing how it affects the citric acid %.

I have heard/read that it can be difficult to predict a final pH, or rather make a blend to target a certain pH value, so I believe that is why we look at the citric acid % in our calculation. If there is no way of making a blend to target a pH value, then a blend calculator targeting a citric acid value would also be helpful.

Attached is the workbook with the calculation we are currently using if that helps.

 

 

[pHruit]

The calculation method sounds reasonable for estimating citric acid content, but it is vastly more complex to extrapolate that to a calculation of pH.

Calculating pH due to acid (or base) addition is feasible in very simple cases, e.g. a single acid into pure water. In the real world it becomes very complicated - pH is effectively a measure of hydrogen ion concentration, and to calculate this, you have to be able to account for all of the components in your system that have an effect on this.

In your case you have two challenges:

1) The vegetable juice/puree is a complex system as there are a lot of different things in there, so your calculation is extremely complicated, and;

2) The vegetable juice/puree probably isn't sufficiently well characterised even if you did want to attempt this calculation - each batch will vary, the natural concentrations of the various components of the juice will be different each time.

 

IMEX many processors in your position approach this by defining a set addition that they know will work, based on lab trials and production data. It sounds like you have the latter so may be able to take a similar approach?

For example, you might find that adding 0.5% citric acid to your carrot puree means that it will always come out below pH4.5. So you set your finished product pH spec to something like 4.0-4.5 (or even just a maximum limit of pH4.5), add the same amount of citric each time, and then you're only having to check the pH to verify that it still works, rather than the more laborious measure/calculate/measure/repeat process that you're currently using. Sometimes you'll end up at pH4.1, sometimes at pH4.5, but it greatly simplifies things in terms of managing the production process.

 

The only time I've seen your approach actually be necessary is with finished products where the acid has too much of an impact on taste - e.g. needing to get to below pH4.5 to achieve a safe product with the available process, but staying above pH4.4 as the acid hurts the flavour profile so it needs to be minimised to the greatest extent possible. It's not something I'd recommend as an approach for your type of product though!

[Maxiak]

Thanks for the information! Sounds like there is no set formula or calculation for this so we will take your suggestion of adding a set amount and seeing how the pH turns out.