Improvement of the retention of ocimene in water phase using Class II hydrophobin HFBII

Hydrophobins have exceptional surface activity with potential applications for food and pharmaceutical industry. In this study, the effect of Class II hydrophobin HFBII on the retention of a volatile compound, ocimene in a water phase was investigated. We observed a negative gushing when 200 μg pure HFBII (κ-grade) and 40 μg ocimene (assay ≥ 90%) was added to 1 L sparkling water with CO ₂ concentration of 7 g/L. The droplet size analysis of κ-HFBII, ocimene and the mixture of them showed that the ocimene was emulsified in a solution containing κ-HFBII. The stability of this emulsion was reduced in function of time and this effect was intensified by increasing the temperature and the presence of CO ₂. Additionally, the retention of ocimene in a HFBII rich solution was measured by SPME-GC-MS. When 0.26±0.03 mg HFBII/mL is added to ocimene solution, 43% of the original ocimene concentration (i.e. 5.9 × 10 ^-6 mg/mL) remained in the solution after 3 days, and 32% after 7 days. In contrast, original ocimene concentration in solutions without HFBII was only retained 20% and 14%, respectively. It showed the potential of HFBII to incorporate insoluble flavour compounds in beverages and control their release.