Ray, Debashree (2014) An investigation of genetic factors impacting sterol profiles in Australian olive oils. PhD thesis, Victoria University.

Abstract

Analyses of phytosterol levels in Australian olive oils derived from the cultivar Barnea (Olea europaea L. cv. Barnea)reveal up to 4.8% campesterol, exceeding the IOOC standards that stipulate a level of <4%. It has been observed that sterol profiles appear to remain relatively consistent within individual cultivars, strongly implicating genetic factors as the cause of these different levels. The plant sterol biosynthetic pathway contains a bifurcation that leads to the formation of β-sitosterol or campesterol, with the flux controlled by the activity of two enzymes, SAM-24-methylene-lophenol-C-24-methyltransferase2 (SMT2) and C-4α-sterol-methyl-oxidase2 (SMO2). Thus, it is conceivable that the relative activity/expression of these enzymes could play a pivotal role in determining the relative amounts of β-sitosterol and campesterol in Australian olive oils. However, little is known about these enzymes in olives, nor the effect that many agronomic and/or processing practices have on the relative levels of these sterols in olive oil. To fill this gap, this research describes the analysis of sterol levels in olive oils extracted from fruits grown, harvested and processed under various conditions. In addition, the coding sequences of SMT2 and SMO2 cDNAs and their expression levels during fruit development in olive cultivars Barnea, Frantoio and Picual were also investigated.

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