why is it that the taste of sugar seems to be different when we have cold or when our nose is blocked?

Seventy to seventy-five percent of what we perceive as taste actually comes from our sense of smell. Taste buds allow us to perceive only bitter, salty, sweet, and sour flavors. It’s the odor molecules from food that give us most of our taste sensation.

When you put food in your mouth, odor molecules from that food travel through the passage between your nose and mouth to olfactory receptor cells at the top of your nasal cavity. 

During cold, the? mucus in ?????nasal passages becomes too thick, ?d?u?e? ?t?o? ?w?h?i?c?h? air and odor molecules can’t reach ?t?h?e???? olfactory receptor cells. Thus, ?????brain receives no signal identifying the odor, and everything ?w?e???? eat tastes much the same. ?????