the new fields have a canonical Kähler potential [@weinberg]. As originally shown by Leurer, Nir and Seiberg [@leurernir] this transformation in the chiral superfields consists of a rotation in flavour space and a rescaling of the fields. However, even after this field redefinition, we can still perform further arbitrary unitary rotations of the chiral superfields which will preserve the canonical form of the Kähler potential. Clearly any superfield field redefinitions in the Kähler potential must be performed consistently for all the superfields in the theory and this will result in a transformation of the superpotential couplings when written in terms of the new chiral superfields. This transformation of the Yukawa couplings is the main subject of this work and we are especially interested in the observable effects of this transformation on the physical masses and mixing angles. In fact, in the literature it is often stated that these field redefinitions can have very important observable effects in quark and squark mixings [@dudas; @dreiner; @peddie]. That this is not the case in specific models has been stressed in [@leurernir; @timjones]. Here we generalise this result and show that, at least for the case of an hierarchical Yukawa textures for the up 