Natural antioxidants as food and beverage ingredients - Natural Food Additives, Ingredients and Flavourings - page 118

Kulkarni 1996). In addition, it is reported that citric acid can work synergistically
with natural antioxidants from spices such as rosemary and sage (Irwandi et al.
2004).
Phospholipids
Commercial lecithin is a widely used surfactant for food emulsions, mostly
coming from soybeans. It is classifi ed as a food preservative, especially when
used with primary antioxidants. However, there are confl icting reports regarding
its mode of action. The term 'lecithin' can mean crude fractions (of oil, fat or egg
phospholipids) or it can be used as a reference to phosphatidylcholine specifi cally,
as opposed to other phospholipids, such as phosphatidyl ethanolamine,
phosphatidyl inositol and phosphatidyl serine (Fig. 5.14). Although crude lecithin,
pure phosphatidylcholine and phosphatidylethanolamine function as chelator
synergists (Madhavi and Kulkarni 1996), an additional possible mode of action is
that phospholipids participate actively in shielding vitamin E through the
antioxidant activity of the nitroxide radical that forms during the oxidation of the
phosphatides (Löliger et al. 1996). Soy lecithin is a better antioxidant than several
other synthetic and natural antioxidants in bread the day after baking (Kaur et al.
2007). In addition, soybean lecithin can be used for lard, sunfl ower oil and butter
fat (Sims and Foioriti 1991).
Proteins and peptides
Proteins constitute a rich source of antioxidants. Milk protein is an example of a
protein assessed extensively for its antioxidant activity. It constitutes a rich source
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Fig. 5.14 Phosphatidylcholine.