Edible vegetable oils enriched with carotenoids extracted from by-products of sea buckthorn (Hippophae rhamnoides ssp. sinensis): the investigation of some characteristic properties, oxidative stability and the effect on thermal behaviour

In the recent years, it has been granted a growing interest to the substitution of synthetic food antioxidants by natural ones, while a special attention was directed to their extraction from the by-products of the food industry. Sea buckthorn (Hippophae rhamnoides) by-products are promising sources of bioactive compounds that could be used for their favourable nutritional and functional properties. In this study, ultrasound-assisted extraction and maceration have been used for the direct enrichment of three edible oils (refined sunflower oil, cold-pressed sunflower oil and extra virgin olive oil) with carotenoids from dried sea buckthorn by-products. Total carotenoids content and ABTS free radical scavenger activity of both enriched and commercial oils were determined by spectrophotometric methods, and the colour was evaluated according to the CIELab colour space. The oxidative stability of vegetable oils containing the extracted carotenoids was assessed in terms of peroxide value, while the thermal stability of the oils was evaluated by thermogravimetry and by differential scanning calorimetry. It was shown that the ultrasound-assisted extraction was more effective than the maceration for the extraction of carotenoids from dried sea buckthorn by-products. ABTS radical scavenging activity has been slightly improved for all the oils studied after carotenoid enrichment, while the oxidative stability increased in extra virgin olive oil but decreased in unrefined and refined sunflower oils. Extraction of sea buckthorn by-products significantly (P < 0.05) reduced lightness and increased redness and yellowness of the oils.