Chemistry Reference
In-Depth Information
Fig. 12.19 Chemical structure of citric acid.
Citric acid
This naturally occurring acid can be found in a variety of fruits and vegetable,
with lemons being the richest source (Madhavi and Kulkarni, 1996). Citric acid
is probably one of the most widely used chelators in foods, but it is certainly not
the most potent (Fig. 12.19).
Citric acid was studied in the 1940s and 1950s as a food antioxidant useful in
butterfat, vegetable oils, shortenings, lard, fats, and the phospholipid portion of
milk (Stull et al., 1951). Its use has been studied in combination with primary
antioxidants such as mixed tocopherols (Lea, 1944) and BHA (Magoffin and
Bentz, 1949). In all these studies, citric acid was referred to as `synergist' mainly
because of its metal chelating potential in oil. The other chelators such as EDTA
and phosphates are not readily dispersible in oils.
Madhavi and Kulkarni (1996) list a variety of applications such as fats and
oils, fruits and vegetable products and meat products where citric acid is being
used in combination with BHA, BHT, PG, tocopherols, ascorbic acid, and
ascorbyl palmitate in order to retard lipid oxidation, browning, discoloration of
fruits, and the formation of nitric-oxide hemoglobin in cured meats as well as
rancidity in ground beef and pork sausage. 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
Lecithin is a broad term used to describe crude fractions of oil, fat, or egg
phospholipids. Although nowadays the term lecithin can be used as a reference to
phosphatidylcholine; crude lecithin contains other phospholipids, such as phos-
phatidyl ethanolamine, phosphatidyl inositol, and phosphatidyl serine (Fig. 12.20).
Commercial lecithin, mostly coming from soybeans, is a widely used
surfactant for food emulsions. Although there are contradicting reports on its
antioxidant capabilities and the mechanism of action of its active ingredients;
lecithin is still classified as a food preservative, especially when used with
primary antioxidants.
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