Natural antioxidants as food and beverage ingredients - Natural Food Additives, Ingredients and Flavourings - page 116

Fig. 5.11 Oxygen scavenging ability of ascorbic acid.

Ascorbic acid has proven useful in stabilizing oils and lipid-containing foods.
It is being currently sold for such applications, especially in combination with
other natural antioxidants that function synergistically with it. As with some other
antioxidants, prooxidant effects are observed in some systems, especially in
mayonnaise and energy bars, and more weakly in milk and dressings. This could
be due to its metal reducing power facilitating the release of iron from egg yolk in
the case of mayonnaise and dressings (Jacobsen et al. 2008).

5.3.3 Carotenoids
Carotenoids are lipid-soluble color pigments in fruits and vegetables whose
orange, yellow or red coloration stems from their extensively conjugated double
bond systems. There are hundreds of naturally occurring carotenoids, the most
commonly known ones being lycopene, β -carotene, lutein, zeaxanthin and
astaxanthin. They receive a lot of interest due to possible connections between
consumption and health. The health effects are thought to be associated with their
antioxidant properties. Epidemiological studies have suggested a relationship
between the ingestion of carotenoids and good health (Paiva and Russel 1999).
The extended electron delocalization in carotenoids is the driving force behind the
radical scavenging ability of these natural antioxidants. Other mechanisms include
singlet oxygen quenching and hydrogen peroxide scavengers at high oxygen
pressure, and radical chain-breaking at low oxygen pressure when singlet oxygen
is not present (Rajalakshmi and Narasimhan 1996).
β -Carotene (Fig. 5.12) is naturally present in oils such as palm oil (500-3000
parts per million) and carrots (Thyrion 1999). It can contribute to the oxidative

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Fig. 5.12 Chemical structure of β -carotene.