How to test for sodium hydroxide residue in juice?

I prepare juice on a tank then by the operator fault the volume increased when see it so how can we know it is cip caustic soda solution or normal water the added by error i need ur help pls

The volume that i prepare is 4300 liter of mango juice when we after 8 hour it increased to 4850 liter i think some cip ( causti soda solution or Ro water inserted by the operator fault how can i verify it pls urgently i ask the operator but they told me that they dont know about it

As a rudimentary test, NaOh is alkaline and would therefore be expected to raise the pH of your product, so before/after comparison of the pH results might give you an indication. Whether it will be sufficient to discern anything useful is another question...

It may also have an impact on the colour and aroma (and possibly taste, but I'm not sure if you really want to drink it to find out?!) of the blend.

Depending on how your CIP system is set up, you may be able to check if there is "missing" volume of around 550L there?

Unfortunately I'd suggest that as a general principle if something has been put into your product and you can't confirm exactly what it is, and particularly if you suspect that it could be something that definitely isn't suitable for consumption, then the product should probably be disposed of.

Brix, titratable acidity, pH, sensory, density.  Compare to a control sample.

When you perform the last step of any CIP, the normal procedure is to rinse with hot water or normal water depending on your product type. Take the water sample of the last rinsing step of CIP, test the presence of caustic soda in lab, if present, you may increase the rinsing time of your CIP last step. You have to control the caustic soda or acid residues at CIP level before product transfer. 4300 liter of mango juice become 4850 liter after 8 hrs (why after 8 hrs?) There is a chance of purging water mixing with product, if this is the case, try to prepare less 550 L batch (3750 L) and check after 8 hrs. it may be 4300 L desired volume.  

For detection of Sodium hydroxide, titratable acidity can be determined using Phenolphthalein indicator solution by following:

1. Add a known amount of grape juice to a beaker (usually 10 or 15 milliliters).
2. Add additional water if the juice is rather dark. The amount of water you add is not critical, adding water does not change total amount of acid in your sample. Do not, however, add more water than 5 times the amount of juice.
3. Add about 5 drops of phenolphthalein. Phenolphthalein is an indicator that is clear when it is in a solution that is acidic, but will change to a purplish color when that solution becomes neutral to basic.
4. Add 0.1N NaOH (1/10 Normal Sodium Hydroxide) until the solution starts to turn pinkish and stay pinkish then note the amount of NaOH used for the titration. Make NaOH addition using a pipette graduated in milliliters. A 10 ml pipette works well.
5. Use the following formula to determine the TA of your wine or must. TA = (Number or milliliters of NaOH / Number of milliliters of juice) X 0.75 The units for the TA in this calculation are: Number of grams of tartaric acid per 100 milliliters of juice.