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Table 7.7 Limits of the percentage of insoluble impurities in petroleum ether for each olive oil category fixed by IOOC and Codex Alimentarius for each olive oil category. Category IOOC Codex A. Extra virgin olive oil Virgin olive oil Ordinary virgin olive oil Lampante virgin olive oil Refined olive oil Olive oil Crude olive oil Refined olive residue oil Olive residue oil
≤ 0.1 ≤ 0.1 ≤ 0.1 ≤ 0.2 ≤ 0.05 < 0.05 - ≤ 0.05 ≤ 0.05
≤ 0.1 ≤ 0.1 ≤ 0.1 ≤ 0.05 ≤ 0.05 ≤ 0.05 ≤ 0.05
microbiological/fermentative or chemical oxidative processes. Phenolic Compounds Virgin olive oils contains phenolic substances responsible for their stability against oxidation (Baldioli et al., 1996; Servili and Montedoro, 2002; Del Carlo et al., 2004), beneficial properties in relation to human health (Visioli et al., 2002; Boskou et al., 2005) and for bitter, pungent, and astringent sensory notes (Gutierrez-Rosales et al., 2003; Angerosa and Di Giacinto, 1995; Andrewes et al., 2003; Mateos et al., 2004). Phenolic compounds are transferred into the oil during the olive processing, but their concentration is dramatically reduced during refining (Servili and Montedoro, 2002; Servili et al., 2004) and storage of oils (Cinquanta et al., 1997; Okogeri and TasioulaMargari, 2002). Phenolic fraction includes simple phenols, tyrosol, and hydroxytyrosol, derivatives of hydroxybenzoic and hydroxycinnamic acids, aglycons of some glucosides, namely oleuropein, demethyloleuropein, ligstroside, and verbascoside (Montedoro et al., 1993; Angerosa et al., 1995, 1996a; Cortesi et al., 1995; Bianchi, 2003). Free and esterified cinnamic and elenolic acids, some flavones, hydroxy-isochromans (Bianco et al., 2002), pinoresinol and 1-acetoxypinoresinol (Brenes et al., 2000; Owen et al., 2000) have also been identified (see also Chapter 5). The analysis of phenolic substances involves their extraction from the oil, a cleanup step, the separation into single compounds, and finally their quantification. Several Authors (Morales and Tsimidou, 2000; Tsimidou, 1998; Pirisi et al., 2000; Hrncirik and Fritsche, 2004) have recently reviewed the different analytical approaches for the determination of phenolic compounds, in order to explain the controversial data reported in the literature. Extraction is usually performed by liquid-liquid partition with mixtures of methanol and water, in different ratios, or absolute methanol or tetrahydrofuran. Some researchers consider that the mixture methanol:water 80:20 v/v
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