Here, I'll copy and paste what I wrote in the Can't Judge a Powder thread:
I did Food Science every year since it was introduced when I was in 8th grade (it was a trial at Nats that year), and I even medalled 4th at Nats in 9th grade.
For B division, it's a lot of biochem. Proteins, amino acids, lipids, sugars, etc. Nothing too in depth, but know the building blocks of proteins, lipids, and sugars, what the molecules look like (know all the sugars, but I wouldn't get too hung up on memorizing every structure of every amino acid, you shouldn't have to know more than guanine, alanine, and phenylalanine. But I would suggest knowing every amino acid's name, and whether they're aromatic or not and if they're polar, non-polar, acidic, or basic), and where they get broken down in the body. Also, it's a good idea to study vitamins and their respective deficiencies (e.g. scurvy for vitamin C, rickets for vitamin D), though again, don't worry about their structures. You should also know how the digestive system works, and how food travels through the body.There's also a section on food labels; they'll give you some sample food labels with parts missing and you have to fill them in; you can do this by knowing that proteins and sugars both contribute 4 calories per gram and fat contributes 9 calories per gram. The rest of the written test part is basically just random food knowledge. I've seen questions ranging from cooking techniques to labeling the diagram of an egg to asking us to write observations of broccoli cooked for various times to the question "What is the New York State muffin?" (apple, by the way). As for the lab part, you need to know how different indicator solutions work. Benedict's/Fehling's for monosaccharides (NOT all sugars, sucrose won't change anything in Benedict's), Sudan III and IV for fats, Iodine's (also known as Lugol's) solution for starch, and Biuret's (spelling?) for proteins. I'd also be prepared to do a titration (that's more likely in C division though than B) and to make a bomb calorimeter to measure the calories of something like a peanut.
C division focuses much less on biology and much more on chemistry, much to my chagrin. One event I did at States in division C felt like I got tricked into taking a mixture of Chem Lab and Forensics, with mostly chemistry questions on molarity and titrations and stuff like that rather than anything about food, as well as a section on identifying powders (food powders, but still).
Food Science was one of my all time favorite events, but the problem with it is that it's so broad, they can really ask anything about food at all (though as far as I know, you don't have to cook anything for the lab part). Still, it's a really interesting event, and I'm glad it's back (sorry C division, it's B only this year. I know Phenyl's gonna be upset, it's her favorite event ever and she won't get to do it).
Fossils: 1st @ reg. 3rd @ states (stupid dinosaurs...) 5th @ nats.
Dynamic: 1st @ reg. 19thish @ states, 18th @ nats
Herpetology (NOT the study of herpes): NA
Enviro Chem: 39th @ states =(
Cell Bio: 9th @ reg. 18th @ nats
Remote: 6th @ states 3rd @ Nats
Ecology: 5th @ Nats