A student tests a food sample and finds it contains reducing sugars, starch, and protein. Which combination of positive results would confirm this?

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Question

A student tests a food sample and finds it contains reducing sugars, starch, and protein. Which combination of positive results would confirm this?

Accepted Answer

A. Blue-black with iodine, brick-red with Benedict's, purple with Biuret — Iodine solution turns blue-black in the presence of starch. Benedict's reagent produces a brick-red precipitate with reducing sugars. Biuret reagent turns purple in the presence of protein.

Answer

A. Blue-black with iodine, brick-red with Benedict's, purple with Biuret

Answer

C. Blue-black with iodine, brick-red with Benedict's, blue with Biuret

Answer

D. Orange with iodine, brick-red with Benedict's, purple with Biuret

Answer

B. Brick-red with iodine, blue-black with Benedict's, purple with Biuret

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