According to my textbook (Class 12 NCERT Chemistry):
Fructose also exists in two cyclic forms which are obtained by the addition of —OH at C5 to the C = O group. The ring, thus formed is a five membered ring and is named as furanose with analogy to the compound furan.
I understood why the pyranose structure for glucose is more stable than the furanose structure ( The pyranose form has the perfect 60° dihedral angle between two non-ring atoms which minimises this type of strain Source: Stability of furanose vs. pyranose form of glucose?). But I do not understand why the same cannot be applied to the fructose structure.
So, to summarize : Why is fructose present in furanose form and not in pyranose form?