A laboratory study of the bleaching process in stigmasta-3,5-diene concentration in olive oils

The bleaching effect was simulated in pilot plant by measuring the influence of temperature (40, 50, 60, 70, 80, and 90 degreesC), time (5, 10, 15, 20, 25, and 30 min), and concentration of solid adsorbent [1.5 and 8% (w/w) of Tonsil supreme NFF] on stigmasla-3,5-diene (STIG) obtained by dehydration of steroidal compounds. Conditions were chosen to simulate those used in industrial operations. The presence of refined oils in extra virgin olive oil can be detected by these newly formed steroid hydrocarbons. Experimental results indicated that STIG did not exceed an imposed limit of 0.15 mg/kg in extra virgin olive oil, when oils were breached with 1.5% earth at temperatures less than or equal to 80 degreesC for 30 min in admired to oils sold as virgin. A large proportion of the adulterations were not detectable by the official methods. Color determinations (CIE-1931 chromatic coordinates) were replicated on a refined oil and in admired extra virgin olive oil. Color of olive oil was not significantly affected by mixing with refined oil (less than or equal to 20%).