Sentence:  Sugars are wonderfully robust materials! Unlike proteins that easily <WSD>denature</WSD> and coagulate, unlike fats that are damaged by air and heat and go rancid, unlike starch chains that break apart into smaller chains of glucose molecules, sugars themselves are small and stable molecules. 
Meaning of the word marked with <WSD> tags:  To alter its original form or state, especially of a protein, by heat, acidity etc.