Instant results!
This shows a picture of the 4 potato halves.
Number 1 has salt added to the cavity scooped out, 2 has sugar, whereas 3 is left empty and 4 (which has been boiled) also has salt.
After about 1 hour, it can be seen that liquid has formed in numbers 1 & 2, but not in 3. Number 4 remains practically the same.