beta-carotene and 2-tert-butylhydroquinone

The effect of the thickness and density of droplet interfacial membrane on the chemical stability of β-carotene in emulsions was investigated, and its impact on the effectiveness of oil-soluble antioxidants to retard β-carotene degradation was examined. β-Carotene was incorporated into the emulsions stabilized by PEGylated emulsifiers having various-sized hydrophilic groups. In the presence of oxidative stresses (pH, iron ions, and radicals in this study), it was observed that the interfacial thickness was relevant to the stability of β-carotene encapsulated into emulsion droplets. Particularly, iron-mediated carotene degradation was effectively retarded in the emulsions having a thin interfacial membrane than ones with a thick interfacial membrane. The interfacial denseness also affected β-carotene stability but its ability to retard β-carotene degradation was influenced by the interfacial thickness. Although β-carotene degradation rate decreased upon the addition of oil-soluble antioxidants, its antioxidant activity depended on what prooxidant promoted the degradation of β-carotene in the emulsions.

Topics: Antioxidants; beta Carotene; Beverages; Emulsifying Agents; Emulsions; Hydrophobic and Hydrophilic Interactions; Hydroquinones; Oxidation-Reduction

The effects of spray-drying of the unicellular microalga Dunaliella salina on its beta-carotene content and geometric isomer composition have been studied. The efficacy of a range of synthetic and natural antioxidants in preventing degradation of beta-carotene has been determined. Losses of beta-carotene and isomerization were minimal during processing for both the control (no exogenous antioxidants) and the samples containing butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ). However, the use of tocopherol-based antioxidants resulted in degradation of 52-72% of beta-carotene during the drying process. All dried powders of Dunaliella proved to be unstable during storage in the presence of light and air, with beta-carotene degraded according to a first-order kinetic model. Of the antioxidants studied, only TBHQ was successful in significantly minimizing degradation (degradation constants of 0.03 and 0.04 days(-)(1), compared to 0.53 days(-)(1) for the respective control). For control powders and those with BHT added to the feed, the degradation constants were reduced to values between 0.27 and 0.37 days(-)(1) by restricting light and flushing with nitrogen; however, storage in the dark alone had no effect. For more slowly degrading powders having TBHQ added to the feed, it was clear that degradation of beta-carotene was influenced by both light and oxygen. During storage the 9-cis isomer of beta-carotene was significantly more unstable than the all-trans form. TBHQ was, however, successful in reducing relative losses of this isomer for samples stored in the dark. The results suggest a dominant photodegradative mechanism for the loss of the 9-cis isomer of beta-carotene.

Topics: beta Carotene; Chromatography, High Pressure Liquid; Eukaryota; Hydroquinones; Isomerism; Light