Within SM, it is know that baryon number is not preserved and changes as
$$ \Delta B = 3·\Delta n_{CS}, \quad n_{CS} \in \mathbb{Z}\ ({\rm Chern-Simons\ index\ for\ vacuum}) \tag1$$ Then, its minimum value is $\Delta B = -3 = B(f) - B(i)$ for a reaction $i \rightarrow f$. Looking for $B$ violation in nuclei, you have to take $i$ as a set of neutrons and protons. I have tried to use 3 nucleons, so $B(i) = 3$ and therefore $B(f) = 0$ but I couldn't find any way to obtain mesons from the valence quarks of the nucleons.
Do you know any examples of nuclei decays with $B$ violation?