Page 166 - Natural Antioxidants, Applications in Foods of Animal Origin

Natural Antioxidants: Control of Oxidation in Fish and Fish Products 145
VetBooks.ir and fat-soluble vitamins including, vitamins A, D, E, and K. Christie

(1998) defined lipids as “fatty acids, their derivatives and substances
related biosynthetically or functionally to these components.” Although
they constitute a minor component of food, contribute to the feeling of
satiety, and help in making food products palatable, they have been known
to significantly affect food quality. This effect on food quality is as a result
of constant exposure of lipids, particularly unsaturated fatty acids to air.
The susceptibility of lipids to oxidation is one of the main causes of quality
deterioration in various types of fresh food products as well as in processed
foods.
Lipid oxidation is believed to be one of the factors limiting the shelf
life of fish as well as many other complex products (Jacobsen, 1999). Lipid

oxidation is most evident in products with a high amount of unsaturated
fatty acids leading to rancidity, off-flavor, taste, color, and nutritional value
such as reductions in omega-3 fatty acids, some vitamins, and formation of
potentially toxic substances (Medina et al., 2009). Lipid oxidation to some

extent affects the safety of fish products for human consumption; hence,
a notable determinant in consumers’ preference for fish and fish products.
Within the food industry, a great deal of research and attention is spent on
the on-going oxidative processes with the aim of protecting raw materials
and products from oxidation during production process and storage. Lipid
oxidation, initiated by hemoglobin(Hb) (Christensen et al., 2011), occurs by

a reaction between free radicals and oxygen in the presence of other initia-
tors (metal, light, and heat) that results in the formation of HPOs and peroxy
radicals(Andersen et al., 2007).

The primary products undergo further reactions to form more stable
compounds such as hydroxy acids (that can contribute to bitter taste) or
epoxides(Grosch et al., 1992). The interaction of lipid HPOs and secondary

oxidation products with proteins and other components in complex food
systems, significantly impact oxidative, flavor stability and texture during
processing, cooking, and storage (Erickson, 1992). Oxidized lipids can

further react with amines, amino acids, and proteins to form brown macro-
molecular products (Frankel, 1998). According to Pan et al. (2004), color

formation is known to be primarily influenced by the degree of fatty acid
unsaturation, water activity, oxygen pressure, and the presence of phenolic
compounds. Metal, metalloproteins, and enzymes are important factors
affecting lipid oxidation in fish products. Water activity, lipid interac-
tions, proteins, and sugars are important elements affecting the quality of
processed fish.