The fruit of the oak tree.

When sugar syrup is cooked, water evaporates and sugar concentration increases as well as the temperature of the syrup. The hard-ball stage is when a bit of syrup dropped into cold water forms a hard ball that doesn't flatten when removed from the water. Although hard, it's still malleable. The temperature of the boiling sugar syrup at this stage is between 240°-265°F.

A substance that binds together ingredients that normally don't combine, such as oil and water. Egg yolks contain lecithin, a natural emulsifier, and are used to stabilize oil in water emulsions such as mayonnaise or Hollandaise sauce.

A type of leavener, similar to baking powder and baking soda, that's used in some recipes. Also known as hartshorn, carbonate of ammonia and powdered baking ammonia.