Understanding oxidation processes in foods - Oxidation in Foods and Beverages and Antioxidant Applications - page 24

Fig. 1.13 Antioxidant evaluation strategy as proposed by Becker et al. (2004). The final
evaluation of antioxidant protection of food and beverages depends on storage
experiments, while the final evaluation of health effects of antioxidants depends on
human intervention studies. Quantification of radical scavenging capacity or reducing
efficiency alone only provides guidelines for the final evaluation.

experiments or in human intervention studies. For food systems this has become
even clearer as it now appears that antioxidants protecting lipids do not
necessarily protect proteins, at least in meat (Lund et al., 2007).
Radical scavenging alone does not constitute a good antioxidant. Carotenoids
are not chain-breaking antioxidants but are, besides being quenchers of singlet
oxygen, efficient radical scavengers through three mechanisms (Galano, 2007):
R · Car ! R ÿ Car ·

1.20

R · Car ! [R ÿ Car] · 1.21

R · Car ! RH Car(ÿH) · 1.22

Carotenoids may regenerate each other from their radical cations:
Car 1 · Car 2 ! Car 1 Car 2 ·

1.23

for which reaction the following hierarchy has been established (Mortensen et
al., 2001):

lycopene > -carotene > zeaxanthin > lutein >> canthaxanthin > astaxanthin
1.24

with lycopene being the most efficient radical scavenger. Notably astaxanthin,
which is the least efficient radical scavenger among the carotenoids considered
and with a moderate tendency of forming radical cations, is often found to have
very positive effects on oxidative stability of food lipids (Jensen et al., 1998). In