In this work we investigate the use of nanoporous carrier as drug delivery systems for hydrophobic molecules. By studying a model system made of porous silicon loaded with beta-carotene, we unveil a fundamental limitation of these carriers that is due to heterogeneous nucleation that imposes a tradeoff between the amount of drug loaded and the reproducibility of the release. Nonetheless, such issue is an alternative and improved method, compared with the standard induction time, to monitor the formation of heterogenously nucleated aggregates.