Posibility to improve the quality characteristics of olive-pomace oils and to enhance differentiation with refined olive-pomace oil

An investigation was carried out to evaluate the oxidative and hydrolytic degradation of 37 olive-pomace oils marketed in southern Italy and to compare the results with those obtained from 10 deodorised olive-pomace oils representative of large stocks of oil obtained after the ®nal step of re®ning. One aim of the research was to ascertain the quality characteristics of commercial olivepomace oils; another was to verify whether the legally prescribed addition of virgin olive oil to re®ned pomace oil, so that the ®nal product may be classi®ed commercially as olive-pomace oil, was actually suf®cient to justify upgrading. The analytical methods used were silica gel column chromatography and high-performance size exclusion chromatography. The data obtained showed that the ®nal retail olive-pomace oils had a lower degree of oxidative degradation than the re®ned oils, as indicated by the lower values obtained when summing the proportions of triglyceride oligopolymers and oxidised triglycerides. Conversely, hydrolytic degradation, which was evaluated by determining diglycerides, proved to be the same in the two categories of oil. The proportions of virgin olive oil added are small, as indicated by the statistically indistinguishable values of triglyceride oligopolymers and free fatty acids obtained. The possibility of setting a limit to the amount of triglyceride oligopolymers present in the commercial category of olive-pomace oil has been considered. This limit would ensure standardisation of the level of oxidation and, consequently, of the quality of marketed oils and would enhance differentiation between olive-pomace oil and re®ned olive-pomace oil.