Page 379 - Natural Antioxidants, Applications in Foods of Animal Origin

358 Natural Antioxidants: Applications in Foods of Animal Origin
VetBooks.ir This circumstance, however, seems to be irrelevant from the point of view

of the food chemistry concerns.
Ascorbic acid is, of course, approved and widely used in foods, being he
E300 additive.

9.3.1.3 CAROTENOIDS

Carotenoids are natural pigments which are synthesized by plants, being
responsible for the bright colors of several fruits and vegetables. There
are several dozen carotenoids in foods, and most of them have antioxidant
activity (Paiva & Russell, 1999). Beta-carotene and lycopene; however,
have been the best studied and more widely used ones.
Beta-carotene (C H ) is a tetraterpene formed by eight isoprene units
40
56
having beta-rings at the two ends of the molecule. It is well known for
its provitamin A activity. With a strong lipophilic character, it acts as free
radical scavenger and therefore it has antioxidant properties widely demon-
strated in in vitro assays and in animal models. This antioxidant activity
is not lost by degradation to long chain breakdown products (Mueller &
Boehm, 2011). It shows, however, good antioxidant behavior only at partial
pressures of oxygen lower than 150 mm Hg. At higher oxygen pressure
values, β-carotene loses its antioxidant activity and, in contrary, it shows an
autocatalytic, pro-oxidant effect, particularly at relatively high concentra-
tions (higher than 5 × 10 mol/L). Despite of its antioxidant activity, in the
−5
food industry is more used as colorant with the number E160a(ii).
Lycopene (C H ) is also a tetraterpene formed by eight isoprene units,
40
56
but with a single aliphatic chain lacking of rings. As the β-carotene, lyco-
pene is highly lipophilic and it has antioxidant activity (Sies & Stahl, 1998)
due to their conjugated double bonds, but it lacks of provitamin A activity.
Contrary to the β-carotene, it is not obtained by synthesis, and purification
from natural foods, following complicated and expensive processes, is the
only source of this compound. This circumstance, together with the high
instability of the molecule notably limits its use as food additive, being used
preferably as colorant (E160d). However, tomato powder, mainly due to its
high lycopene content, was reported as an effective antioxidant in cooked
pork patties (Kim et al., 2013).
Mixtures of carotenoids or associations with other antioxidants (e.g.,
tocopherols) can increase their scavenging free radical activity.