Lines 372–377: what contrast is in the final paragraph? how does the contrast between what the author sees and what he smells relate to his purpose?

text:
grainger had brought a dozen small glass bottles from the lab.
after he opened each bottle, i dipped a fragrance testing filter into it.
the filters were long white strips of paper designed to absorb aroma
chemicals without producing off-notes. before placing the strips of
paper before my nose, i closed my eyes. then i inhaled deeply, and
one food after another was conjured from the glass bottles. i smelled
fresh cherries, black olives, sautéed onions, and shrimp. grainger’s
most remarkable creation took me by surprise. after closing my eyes,
i suddenly smelled a grilled hamburger. the aroma was uncanny,
almost miraculous. it smelled like someone in the room was flipping
burgers on a hot grill. but when i opened my eyes, there was just a
narrow strip of white paper and a smiling flavorist.