Formation of the 5,6-epoxy derivatives of 7-liydroxy-cholesteryl 3β-acetates during peroxidation of cholesteryl acetate.

The thermal peroxidation of cholesteryl acetate (CA) generates many compounds, most of which have been identified in previous studies. The trimethylsilyl (TMS) derivatives of the thermodegradation products of the single hydroperoxides of CA (7α- and 7β-) gave GCMS spectra that were almost identical to those of the thermal peroxidation of CA, except for four compounds that were only detected as TMS derivatives. These substances were identified by comparing their mass spectra and their GC retention time against those of the four synthesized isomers of the epoxy-hydroxy derivatives of CA. The presence of a considerable amount of epoxy-hydroxy derivates of CA, especially at low-temperature degradations, provides an explanation for the formation of other substances that have been previously identified

Stereospecific distribution of fatty acids in triacylglycerols of olive oils

The positional distribution of fatty acids (FA) in triacylglycerols (TAG) of 47\u2009virgin olive oils from diverse cultivars grown in distinct areas of North-Eastern Italy was studied. Few data were previously available on oils from these geographical areas. The effects of climatic and geographical conditions on the stereospecific distribution of TAG in olive oil were confirmed. Moreover, the results of the stereospecific analysis were used to evaluate the preferential esterification position of each FA on the basis of the degree of unsaturation and the chain length. The data of the stereospecific analysis of olive oil TAG can contribute to the determination of the selectivity of olive fruit acyltransferases for distinct FA

Thermal stability of 7-trimethylsilylperoxy-cholest-5-ene 3b-acetates at high temperature

The thermal degradation of the two hydroperoxy isomers (7 a - and 7 b -hydroperoxides) of cholest-5-ene 3 b -acetate (CA) generates many products, of which most have already been identified; the two 7-hydroxy-CA a - and b -isomers are among these compounds. In the case of the 7 a -hydroperoxy-CA degradation, the isomer 7 a -hydroxy-CA is present in a high proportion, while the 7 b -isomer is generated in a larger amount from the 7 b -hydroperoxy-CA. The thermal degradation of the trimethylsilyl derivatives (TMS) of the 7-hydroperoxy-CA gives rise to many products, of which several components are the same as those obtained from the corresponding non silylated 7-hydroperoxy-CA isomer. We have found an unexpectedly high amount of the TMS derivative of the 7-hydroperoxy-CA (7 a - or 7 b -isomers). Traces of free 7 a -hydroperoxy-CA, from thermal degradation of each 7-hydroperoxide-CA TMS (7 a - and 7 b -isomers), were also found

Formación de derivados 5,6-epoxi de los 7-hidroxi-colesteril 3β-acetatos durante la peroxidación del colesteril acetato.

The thermal peroxidation of cholesteryl acetate (CA) generates many compounds, most of which have been identified in previous studies. The trimethylsilyl (TMS) derivatives of the thermodegradation products of the single hydroperoxides of CA (7α- and 7β-) gave GCMS spectra that were almost identical to those of the thermal peroxidation of CA, except for four compounds that were only detected as TMS derivatives. These substances were identified by comparing their mass spectra and their GC retention time against those of the four synthesized isomers of the epoxy-hydroxy derivatives of CA. The presence of a considerable amount of epoxy-hydroxy derivates of CA, especially at low-temperature degradations, provides an explanation for the formation of other substances that have been previously identified.La peroxidación térmica del colesteril acetato (OA) produce varios compuestos, la mayoría de los cuales fueron ya identificados en estudios precedentes. Los trimetilsilil (TMS) derivados de los productos de la termodegradación de los hidroperóxidos simples del CA (7α- y 7β-) producen espectros GC-MS que son siempre idénticos a aquellos de la peroxidación de CA, a excepción de los cuatro compuestos que son únicamente detectados como derivados TMS. Estas substancias fueron identificadas comparando los espectros de masa y los tiempos de retención GC con los cuatro isómeros de los derivados epoxi-hidroxi del CA. La presencia de una considerable cantidad de derivados epoxi- hidroxi del CA, especialmente a bajas temperaturas de degradación, proveen una explicación de la formación de otras substancias que fueron Identificadas precedentemente

Le molecole del gusto: metodi di analisi della frazione aromatica degli alimenti

Foods usually undergo to sensory evaluation: in some cases (olive oils, butter) it has become a legal evaluation within the frame of EU regulations, in some other cases (e.g. honeys) they have reached a fully standardized level. Analytical chemistry applied to foods, however since a number of years devoted efforts to characterize food volatile compounds which are responsible of the so said \u201cflavor\u201d. In this paper some details will be described concerning improvements and trends in foods volatile compounds, enclosing trials carried out to study relationships between these and sensory evaluation