Question

The following foods were tested for starch using iodine. The results are shown below:

Food stuff	Colour
rice	blue-black
cucumber	no colour change
onion	no colour change
dal	blue-black

Which of the following foods contains starch?
(i) rice + dal
(ii) rice + cucumber
(iii) only rice
(iv) dal + onion

(a) only i
(b) i, ii, iii, and iv
(c) i, ii, and iii
(d) i, iii and iv

Answer 1

(a) only i
When iodine's colour turns blue-black, it indicates the presence of starch in food. Here, rice and dal give positive test for starch.