Influence of Edible Oil Refining Processes on its Contamination by PAHs

BARRANCO, A.; ALONSO-SALCES, R. M.; BERRUETA, L. A.; GALLO, B.; VICENTE, F.; SAROBE, M.

La Coruña (España)

Simposio; VIII International Symposium on Analytical Methology in the Environmental Field and XIII Meeting of the Spanish Society of Analytical Chemistry; 2003

Universidad de La Coruña y Sociedad Española de Química Analítica (SEQA)

Edible oil production consists of two main steps. First, the oil is extracted from the seeds orfiu~tsb y mechanical @ress) or chemical (solvent extraction) processes. The raw oil obtained isbasically composed of biglycerides and in minor proportion by other products, whose effects onthe organoleptic, functional and nutritional properties are very important. Secondly, the oil isusually refined in order to remove those undesirable components, wlthout damaging its quality.The polycycllc aromatic hydrocarbons (PAIIs) are one of these undesirable minoritycomponents in the raw oils and they appear in concentrations from a few pgkg to mgkg, due tothe environmental contamination and several technological practices camed out in some producingcountries [I].The aim of this work is the study of the influence of some steps in the refining process on thecontamination by PAHs. Therefore, samples of different oils (coconut, sunflower and palm kernel)along the process have been taken and the PAHs have been Isolated by means of a liquid-liquidextraction, followed by a solid phase extraction sample clean-up. Finally, 16 PAHs have beenseparated and quantified by HPLC with fluorescent detection. Above all, bleaching anddeodorization are the most influential steps. The latter reduces the concentration of the llght PAHs(naphthalene, acenaphthylene, acenapbthene, fluorene, phenanthrene, anthracene, fluoranthene andpyrene) in more than 90 %, while benzo(a)anthracene and chrysene are reduced in a 50 % and theheavy PAHs @enzo@)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dlbenz(ab)anthracene,benzo(&h,i)perylene, mdeno(l,2,3-c,d)pyrene) remain nearly haltered.The bleaching step removes the heavy PAHs almost completely due to the employment ofactivated carbon, whlle the light ones are reduced to a lesscr extent than during the deodorization.The raw coconut oil was, among all the oils studied, the one that showed a greater level ofcontamination, more than 10 nglg of benzo(a)pyrene and a great quantity of light PAHs. Therefore,it is needed to include an additional deodorization step before bleaching, in order to avoid a changeof the retention capacity of the activated carbon since a saturation of the active sites can occur.Besides, it has been verified that a hydrogenation step is able by itself to remove the heavy PAHsand to reduce the quantity of the light ones almost in the same percentage as the deodorization.