By Harold McGee
The original interfering agents were glucose and fructose, or “invert sugar”. When heated along with a small amount of acid (often cream of tartar), sucrose is broken down into its two components, glucose and fructose. Glucose and fructose interfere with sucrose crystallization by bonding temporarily to the crystal surface and blocking the way of sucrose molecules. Honey is a natural source of invert sugar, and “invert syrup” is an artificial preparation of a glucose-fructose mixture. Thanks to their fructose content, both honey and invert syrup readily caramelize and can cause undesirable browning in some sweets. Acid-inverted syrups brown less because their acidity slows caramelization.