Abstract: Sea buckthorn (Hippophae rhamnoides L.) pulp oil (SPO) is an expensive edible vegetable oil due to its beneficial bioactive ingredients, but this oil may pose a risk of phthalic acid esters (PAEs) exceeding the legal limits, depending on various factors such as growing environment, picking methods, and storage methods. In the present study, two-stage molecular distillation (MD) was used to remove 8 PAEs from SPO. Fatty acid composition and the contents of VE, phytosterol, and flavonoids in SPO were detected before and after MD to evaluate the effect of MD on the removal of PAEs and the retention of bioactive constituents. The results showed the contents of di-butyl phthalate (DBP) (1.626 mg/kg) and bis(2-ethylhexyl) phthalate (DEHP) (10.933 mg/kg) in raw sea buckthorn pulp oil (R-SPO) greatly exceeded the limits (0.3 and 1.5 mg/kg respectively) specified in China’s national standard for the use of food contact materials and food additives. The content of DBP decreased from 1.626 to 0.071 mg/kg during the first stage of MD, which was far below the legal limit, and the content of DEHP reduced from 10.933 to 0.668 mg/kg during the whole MD process. The removal rates of DBP, DEHP, DINP and the sum of these PAEs and five others were 98%, 94%, 85% and 93%, respectively; after two-stage MD, the retention rates of VE, sterol and flavonoids were 14%, 32%, and 46% respectively. Fatty acid composition of SPO did not change obviously, almost no trans-fatty acids were produced, whereas the proportion of free fatty acids decreased visibly. These results indicated that the two-stage molecular distillation process was an effective method to remove high concentrations of PAEs from edible vegetable oils, but it could result in large losses of nutrients such as VE, sterol and flavonoids. One-stage molecular distillation could reduce the contents of DBP and DEHP in edible vegetable oil to less than the legal limits while avoiding losses of nutrients, increasing the retention rates of VE, sterol and flavonoids up to 35%, 55% and 63%, respectively.

Key words: sea buckthorn pulp oil, phthalic acid esters, molecular distillation, VE, sterol, flavonoids