Black pepper

Except potato, all the rest are the names of the fruits, while Potato is a vegetable. Hence, it is the odd one.

Sum of the digit in each number, except 324 is 10.

hey the answer is ….

28 as it not perfect square

whereas 16 , 36 , 64 are perfect squares

626-1 = 625 = 25².
962-1 = 961 = 31².
1090-1 = 1089 = 33².
But,
841-1 = 840 (not a perfect square).

Otherwise, 841 is a perfect square of 29, other are not a perfect square.