Plant sterol oxides in functional beverages: Influence of matrix and storage

Three plant sterol (PS)-enriched beverages, milk based fruit juice (MFJPS), fruit juice (FJPS) and milk beverage (MPS), were stored at 4, 24, or 37 C and analysed at regular time intervals of 2 months until 6 months. PS stability was analysed from the production of phytosterol oxidation products (POPs). The 6-sitosterol oxides (7 alpha/7 beta-hydroxy, beta/alpha-epoxy, triol, and 7-keto) and campesterol oxides (beta/alpha-epoxy, and 7-keto) were detected in all beverages and at all storage times and temperatures. Total POP contents followed the order MPS >> FJPS > MFJPS. In general, the beverages showed low PS oxidation levels (<0.17%). Predictive models of POP content versus storage time were established. These models explain total POP content by over 75% and individual POP content by over 50%. We propose 7-ketositosterol and 7-ketocampesterol as PS oxidation markers during storage of beverages of this kind. (C) 2014 Elsevier Ltd. All rights reserved.