You could have tried sweet talking him.

Judges are meant to determine just how well you know the subject matter, and if you can convey the information in an accurate and easy to understand way to a person who has no idea what you're talking about. It doesn't matter if he already knew what glucose is; the point is that he's playing a part and judging how well the OP can inform him. This is probably a middle or high school presentation, and is designed to enhance presentation skills. The judge was actually doing his job. Source: Have judged and been judged for similar events.

#25, You're right. When I went to districts science fair, the judges there pretended they didnt know what the rocks were (I was doing a thing with rocks and acid). They're supposed to make you feel like you're presenting it to a crowd of people, not just a professional judge.

It's like getting a football coach to judge figure skating

That wouldn't have worked. Sweet things just end up as glucose

Well in life, you have to understand that not many people care, making it unfair most of the time.

Who doesn't know what glucose is??

They probably knew, but they might have been trying to see how well the information can be presented.

Exactly what I was thinking. There's no way a judge in a legitimate science competition didn't know what glucose was. They were probably seeing if OP could explain it to some one who has no idea what it is and doesn't have any science background.

Or as part of his job to judge, pretend to not know, to see how well the person knows the subject matter

agreed, maybe he expecting your presentation to include what it is?

was... was that a glucose joke?

Yes, but it didn't seem fructose.

i love both of you