Edible and non-edible olive oils discrimination by the application of a sensory olfactory system based on tin dioxide sensors.

An array of semiconductor sensors has been developed to discriminate virgin olive oil samples based on their organoleptic characteristics. The multisensor, developed at laboratory, is composed by 14 sensing elements of tin dioxide thin layers (doped with Cr and In, and undoped) deposited by the reactive sputtering technique. The sensors are stable and show good repeatability. Off-flavors and extra-virgin olive oil samples, taken at the outlet of the vertical centrifuge of a small experimental olive oil mill and sensory evaluated, have been used. A good discrimination of edible (extra-virgin and virgin) from non-edible (lampante) olive oils has been obtained through the statistical method of principal component analysis (PCA).

Digestive stability of hydroxytyrosol, hydroxytyrosyl acetate and alkyl hydroxytyrosyl ethers.

The digestive stability of two natural antioxidant compounds present in virgin olive oil, hydroxytyrosol (HTy) and hydroxytyrosyl acetate (HTy-Ac) and a new series of hydroxytyrosyl ethers (methyl, ethyl and butyl hydroxytyrosyl ethers) was evaluated by a simulated digestion procedure. High recovery of all compounds after gastric digestion was obtained, although they showed a statistically significant lower stability after pancreatic-bile salts digestion. HTy-Ac was partially hydrolyzed into free HTy, whereas after intestinal digestion, HTy was converted into 3,4-dihydroxyphenyl acetic acid (DOPAC), and HTy-Ac was hydrolyzed to HTy and subsequently transformed into DOPAC. In contrast, no chemical modification of hydroxytyrosyl ethers during in vitro digestion was observed. In summary, HTy, HTy-Ac and hydroxytyrosyl ethers show high and interesting digestive stability and the new synthetic hydroxytyrosyl ethers showed enhanced chemical stability compared to HTy and HTy-Ac.