Can you suggest some interesting food items for my students to taste for our class science fair project?

I teach primary, which means we have to do our project together as a class. I'm planning to have a kind of boys versus girls thing in which they'll make predictions about which sex has better taste buds.

Then I wanted to have each group taste 5 different food items while blind folded. Each team would have a designated person that tallies how many people guess correctly and incorrectly.

They're second grade, so I wanted to make it challenging, but not so hard that no one can guess any of them. Here are some of the ideas I had:

1) Vinegar

2) Cotton Candy

3) Ketch --up

Choose something from each of the 4 tastes - sweet, salty, bitter, sour and maybe something from the "5th taste" umami, which is a kind of savoury flavour.
Honey, pretzel, cocoa, lemon juice or grapefruit. For umami, maybe chicken broth?
If you stick to fairly pure and unprocessed items you will minimize food allergy dangers and give a reasonably pure flavour.
Sounds like fun, good luck.

Seaweed (the paper like stuff they use to make sushi)

broccoli, apple sauce, cottage cheese, banana, green bean, corn, cucumber, tomato, there are many. This is a good idea. I home school, I want to try it with my 2nd grader. Good luck have fun.

Vinegar is nasty alone and bad for you, I'd stratch that one lol.

Catchup - Good!
Cotton Candy - A bit easy but it's good.
Soy milk
Life cereal
Doritos
Cheerios
Penne Pasta (the noodles)
Red or white pasta sauce
Peanuts
M & M's
Raisins

But, send out a slip asking their PARENTS if they have any alergic reactions to any foods. If so, have a box for them to check Yes or No and if yes, then have them fill it out like dairy products or just cheese etc.

First of all, vinegar isn't bad for you and I think that's a good one!

Other ideas:
orange juice
radishes
lemons
ice cream
yogurt
pineapple

it sounds very fun and like a great project. but as the parent of kids with life-threatening allergies, it does make me cringe a little. do make sure first whether any of the kids in your class have allergies and then make sure you read the labels on absolutely everything (even if you're "sure" it wouldn't have the allergen in it ... i can tell you that peanuts or peanut oil, for example, can show up in jellybeans, salsa, chili, and and a thousand other unlikely places ... and that one bite can be fatal for some kids).

if you're careful with the labels and the allergies, go for it. again, sounds like a great project. maybe some herbs, like basil or oregano? or spices, like cinnamon?

1.Relish
2.Tomatoes
3.Sweet Pickles
4.Sour Gummies

apple
mango
strawberry
sugar water
salt water (a drop on the tongue)
carrot
jam (jelly if your american)
a potatoe chip

We did this when I was in second grade and no one guessed honey. It was harder than you think.

nacho cheese

sugar

salt

graham crackers

salad dressings

I remember for one tast challenge, they had us eat a small piece of baker's chocolate. We were expecting something good, but we got something NASTY!! It's a good example of a bitter taste.