Beverage brewing unit (1) particularly for machines for preparing beverages from capsules by centrifugation, comprising: a casing, a capsule enclosing assembly comprising a first enclosing part (2) connected to the casing and a second enclosing part (3), moveable relative to the first enclosing part along a longitudinal direction of axis (I), preferably in translatory movement, between a capsule insertion position in which the two enclosing parts are at distance from each other with a passage (9) formed in between and a capsule enclosing position in which the capsule is enclosed between the first and second enclosing parts (2,3), wherein the first enclosing part (2) and the second enclosing part (3) define together a centrifugal rotating chamber assembly arranged for receiving the capsule and for rotating it for the extraction of the beverage; wherein the brewing unit comprises a capsule insertion assembly (32) comprising sliding surfaces (36), preferably arranged on each lateral side of the passage (9), for guiding the flange (7) of the capsule during insertion in the passage (9) and support surfaces (35), preferably transversally oriented relative to the sliding surfaces, for holding the flange of the capsule when inserted in the passage (9).