Stability of Hydroxy-α-Sanshool in Medium-Chain Triglyceride Oil and Corresponding Oil/Water Emulsions

The pungent component of sansho (Japanese pepper, Zanthoxylum pipritum) is sanshool, which is easily oxidized and decomposed. We have previously reported several sanshool stabilizers, such as α-tocopherol (α-Toc). Sansho pericarp powder treated with middle-chain triglycerides (MCTs) can be used to obtain extracts containing hydroxy-α-sanshool (HαS). Although HαS is stabilized when α-Toc is added to the MCT extracts, the loss of HαS is accelerated when it is mixed with a powder such as lactose. The separation of α-Toc from sanshools was thought to inevitably lead to their oxidation. Therefore, using sansho pericarp MCT extracts with or without α-Toc, oil/water (o/w) emulsions were prepared by adding a surfactant, glycerin, and water to these extracts. In both emulsions, HαS was stable in accelerated tests at 50 °C. However, when lactose powder was added to the emulsions and an accelerated test was performed, HαS in the emulsion containing α-Toc was stable, but HαS in the emulsion without α-Toc was unstable. These results highlight the importance of maintaining the close proximity of HαS and α-Toc in the emulsion. The stabilization of sanshools using emulsion technology can facilitate the production of various processed beverages, foods, cosmetics, and pharmaceuticals containing Japanese pepper.