**8.8 Domestic heat application**

In general, research has shown that olive oil phenolic compounds are subject to degradation upon the application of heat during cooking (Brenes et al., 2002, Gomez-Alonso et al., 2003). However, oleocanthal has demonstrated to be relatively stable upon heating when the EVOO contains a considerable quantity of this compound initially.

One study found a 20% decrease in oleocanthal (96.7 ± 8.5 to 77.5 ± 2.4 mg/kg) upon 12 frying operations (each frying operation 10 min in length, at a temperature of 180°C) (Gomez-Alonso et al., 2003). Similarly, another study observed a 24% decrease (41.5 ± 0.3 to 31.4 ± 0.1 mg/kg) in oleocanthal after heating at 180°C for 36 hr (Allouche et al., 2007). However, for EVOO which naturally contained a lower quantity of oleocanthal to begin with (7.9 ± 0.5 mg/kg), oleocanthal degradation was substantially higher at 71%. It appears that oleocanthal possesses an antioxidative effect, in that oleocanthal is able to withstand heating and therefore protect itself to a greater degree when there is a higher concentration of it in EVOO.

Cicerale and co-workers (Cicerale et al., 2009b) also demonstrated oleocanthal to be stable upon heating at high temperatures (240°C) for extended periods of time (up to 90 min). The authors postulated that the minimal degradation of oleocanthal may be partially due to the chemical structure of this compound and subsequent antioxidant activity. The antioxidant capacity of phenolic compounds is dependent upon the number of hydroxyl groups bonded to the aromatic ring (Sroka and Cisowski, 2003). When free radicals are produced through oxidation, phenolic compounds with a higher number of hydroxyls and therefore increased antioxidant capacity, quickly diminish because they react rapidly with lipid radicals and are therefore consumed (Gomez-Alonso et al., 2003). Oleocanthal possesses one hydroxyl group. Moreover, the site of bonding and mutual position of hydroxyls in the aromatic ring was also postulated to play a role in the antioxidant potential of phenolic compounds (Sroka and Cisowski, 2003, Rice-Evans et al., 1996). Rice-Evans and co-workers (Rice-Evans et al., 1996) reported that a hydroxyl group in the *ortho* position in the aromatic ring results in increased antioxidant capacity compared to compounds with hydroxyl groups in the *meta* and *para* positions. Oleocanthal contains its one hydroxyl group in the *para* position. These structural features may help in explaining why a minimal degradation of oleocanthal was observed (Cicerale et al., 2009c).
