Maria Teresa Bilancia

Diacylglycerol isomers in extra virgin olive oil: Effect of different storage conditions

An experimental investigation was carried out with the aim to investigate on the isomerisation of 1,2-diacylglycerols to 1,3-diacylglycerols as a function of the storage conditions, as well as to identify indices useful to evaluate the freshness of the oils. Two oils derived from two different cultivars (Coratina and Ogliarola barese) were stored for two years as follows: in bottles at dark; in clear glass bottles at light; in green glass bottles at light; in bottles at dark, the latter subjected to repeated opening and samplings to simulate domestic use. The obtained results evinced that during the storage period a significant increase in the 1,3-isomers was observed due to an isomerisation from the 1,2 to the 1,3 isomeric form, consequently the 1,3/1,2 ratio increased in both oils. The covariance analysis of the data showed that the isomerisation of diacylglycerols, taking place during time, was affected by the type of oil, probably due to the different initial hydrolysis level, but was not affected by the storage conditions. Among the parameters considered, the total diacylglycerols/1,3-diacylglycerols ratio could be used as freshness index of extra virgin olive oil, since it is not affected by either oil or storage conditions.

Assessment of the oxidative and hydrolytic degradation of the lipid fraction of mortadella by means of HPSEC analyses of polar compounds.

The aim of this work was to use the HPSEC analysis of polar compounds to assess the level of oxidative and hydrolytic degradation of the lipid fraction of mortadella. The results indicated high primary oxidative degradation of the lipid fraction in the samples, with a mean value for oxidized triacylglycerols of 1.77%, and low secondary oxidation, with a mean value for triacylglycerol oligopolymers of 0.16%. In addition, in some cases, significant hydrolytic degradation was found. HPSEC analysis of polar compounds, to evaluate the level of oxidative and hydrolytic degradation of the mortadella lipid fraction, could be used as an alternative to commonly used techniques, some of which are not always reliable.

A survey of in-oil canned tuna quality by sensory analysis and the determination of the oxidative degradation of the liquid medium.

Sensory analysis and determination of analytical indices to evaluate the oxidative degradation of the liquid medium were used to assess the overall quality of tuna canned in different types of oil. Moreover, the relationships between the quality of the liquid medium and the quality of raw material were studied. The results pointed out that quality of the raw material changed as related to the types of oil used. In particular, the tuna in extra virgin olive oil showed significant higher scores for the descriptors related to the quality of raw materials and lower values for the indices that evinced the degradation of liquid medium.