How are glycosidic linkages formed?
In sucrose molecule the  glycosidic linkage is formed by the OH group on the anomeric carbon of α-D-glucose and the OH group on the anomeric carbon of β-D-fructose.



source : 

https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Map%3A_Organic_Chemistry_(McMurry)/Chapter_25%3A_Biomolecules%3A_Carbohydrates/25.08_Disaccharides

As seen, in either alpha d-glucose or beta d-fructo furanose may react to give sucrose.

Let us examin.

Alpha D-gluco Pyranose gives an intermediate 1 and 2 by protonation at anomeric carbon. 



Similarly  Beta D-fructo furanose gives an intermediate 3 and 4 by protonation at anomeric carbon.


If you examine , structure 3 is more stable then structure 4.



The negative inductive effect of CH2OH in fructofuranose destablizes this intermediate 4.

Hence structure 2 , an intermediate of aplha D-gluco pyranose (more stable) attacks beta D-fructo furanose togive sucrose.

 



The above diagrams are author drawn in CHEM DRAW