Preparation of pterostilbene nanoemulsions with different formulation and its stability

Pterostilbene nanoemulsions ( PTSNE) were prepared by high-pressure homogenization using sunflower oil, olive oil and medium chain triglycerides ( MCT) as carrier oil phase, Tween 80 and sodium caseinate ( SC) as emulsifiers.The influence of the type and concentration of the oil phase, the type and concentration of the emulsifier and co-emulsifier on the droplet diameter of PTSNE were investigated.The influence of p H ( 3 ~ 9) , thermal treatment ( 40 ~ 100 ℃, 60 min) and ionic strength ( 0⁵00 mmol/L Na Cl, 0⁵00 mmol/L CaCl₂) on the physical stability of the emulsions were examined.The results showed that the droplet diameter of PTSNE depended on the type of the oil phase: sunflower oil ≈ olive oil > MCT.The droplet size became larger, and the storage stability became worse with the increase of the concentration of the oil phase up to 20%. The droplet diameter also depended on the type of the emulsifier: Tween 80 < SC, and decreased with increasing emulsifier concentration ( p < 0.05) . When the glycerol was added into the aqueous phase, the particle size of Tween 80 and SC stabilized nanoemulsions were significantly decreased ( p < 0.05) .For Tween 80 stabilized PTSNE, there were good stability at p H ( 3⁹) , thermal treatment ( 40⁹0 ℃, 60 min) and ionic strength ( 0 ⁵00 mmol/L Na Cl, 0 ⁵00 mmol/L CaCl₂) , and the droplet size increased 50 nm at 100 ℃ for 60 min.SC-stabilized nanoemulsions had good temperature stability and were unstable to droplet aggregation at p H values close to isoelectric point of the protein ( p H≈4.6) and at high salt strength ( ≥50 mmol/L CaCl₂) .