Acidity of a food by titration

You could always add universal indicator to a food sample to see what colour it turns, which will give you the pH of the food, but there's another way and it involves titration.

10ml of the fruit juice you are testing goes into the conical flask with 2ml of phenolpthalein indicator. Dilute (0.5M) sodium hydroxide goes into the burette.

Add the NaOH slowly until the fruit juice turns bright pink (the indicator turns pink in alkali).

OR

Put the fruit juice in the burette (take care that it's filtered and doesn't contain any pith that might block the burette).

Add 10ml of NaOH to the conical flask and 2ml of the phenolpthalein indicator (it should go pink straight away).

Add the fruit juice until the colour disappears. Whichever method you use, you should be able to use the general assumption that the more fruit juice it took to neutralise the alkali, the less acidic the fruit juice.