Sterols and triterpene diols in olive oil as indicators of variety and degree of ripening.

Sterols and triterpene diols in olive oil as indicators of variety and degree of ripening derived from three olive varieties and produced at three different harvesting periods were studied. In order to test the stability of the proposed indicators, oils obtained were stored for 12 months at three different temperatures. Thirty-six samples in total were subjected to GC analysis and results were processed by multivariate chemometric methods (MANOVA, PCA, and SLDA). Campesterol, β-sitosterol, Δ(7)-campesterol/Δ(5,24)-stigmastadienol, clerosterol, uvaol, and campestanol/Δ(7)-avenasterol were established as the indicators of variety of fresh oils, while when stored oils were included in the model, the final three compounds were substituted by 24-methylene-cholesterol/stigmasterol. The most important variables for differentiating fresh oils according to degree of ripening were Δ(7)-campesterol/β-sitosterol, uvaol/stigmasterol, clerosterol/Δ(5)-avenasterol and sitostanol/uvaol, while stored oils were differentiated by campestanol/stigmasterol, erythrodiol, stigmasterol/Δ(7)-campesterol, Δ(5)-avenasterol, 24-methylene-cholesterol/β-sitosterol and 24-methylene-cholesterol. Results demonstrated that sterols and triterpene diols can be used as indicators of variety and degree of ripening among virgin olive oils.