The sweetness you taste when you bite into a juicy kiwi fruit comes from a type of sugar known as ketose sugar, specifically fructose (See Reference 1, Page 236). Ketose sugars are a type of monosaccharide, the molecule that forms carbohydrates (See Reference 1, Page 236). Organic chemists differentiate ketose sugars from other monsaccharides by the location of the molecule's carbonyl group (See Reference 1, Page 236). A carbonyl group is the name for the part of a molecule that is made of a carbon atom double bonded to an oxygen atom (See Reference 2). Ketose sugars are grouped into different types based on the number of carbon atoms in the "backbone" of the molecule (See Reference 1, Page 236).
Ketotriose sugars are the simplest molecules of the ketose sugar family (See Reference 1, Page 236). These ketoses only have a three carbon backbone (See Reference 1, Page 236). There is only one ketotriose known in chemistry, called dihydroxyacetone (See Reference 3, Page 194). Dihydroxyacetone is used mostly in self-tanning cosmetics (See Reference 4, Page 5). Although this ketose is not used in food, scientists have concluded that DHA is safe to use as a self-tanning product (See Reference 4, Page 32).