Food Lipids: Chemistry, Nutrition, and Biotechnology

pectinates, have at times been added to glazes so as to reduce the brittleness or the
evaporative rate of the glaze; however, success has been limited [334,369].
Edible coatings (formed directly on foods) and films (preformed, then placed
on foods) can also function to prevent quality losses associated with lipid oxidation
by acting as oxygen barriers. Materials displaying these barrier properties include
polysaccharides (alginates, pectins, agars, carrageenans, cellulose derivatives, amylose,
starches, chitin, etc.) and proteins (casein, whey proteins, wheat gluten, soy
proteins, corn zein, gelatin, collagen derivatives, etc.). Studies demonstrating the
effectiveness of these coatings include those conducted on frozen turkey [335], frozen
king salmon [336], frozen cooked ham and bacon pieces [337], and refrigerated
beef patties [338]. In some cases the coatings were no more effective than ice glazes
[334].
N. Freezing
An excellent method of preserving the quality of meat and fish for long periods is
by freezing the product. At temperatures below �10�C, both enzymatic and nonenzymatic
reactions associated with lipid oxidation are decreased. In the range 0 to
�10�C, however, decreased oxidative stabilities have been noted. When water is
removed as ice in this temperature range, an accelerating effect due to increased
concentration of reactants is observed and it offsets the temperature-induced deceleration.
Illustrating this accelerating effect of ice crystal formation on lipid oxidation,
Apgar and Hultin [339] incubated microsomal membrane fractions in the presence
and absence of miscible solvents (alcohols) to prevent freezing at temperatures below
0�C. When the ratio of the reaction rate at 6�C was compared to that at �12�C, the
rate of lipid oxidation was found to decrease less in the presence of ice than in the
presence of alcohols.
Unless the rate is very slow, rate of freezing has been found to have little
influence on the oxidative stability of frozen products [340]. Instead, storage temperatures
play a dominant role in dictating the stability of muscle foods. This is
particularly true when temperature fluctuations occur during storage, since the extracellular
formation of ice crystals is accelerated and cellular disruption is enhanced,
thus facilitating the interaction of catalysts with lipid substrates [158]. Order of time/
temperature holding treatments, on the other hand, markedly influenced development
of rancidity. Lamb held at temperatures of �5�C to�10�C before storage at �35�C
developed more rancidity than lamb stored at �35�C first, followed by storage at
�5�C or�10�C [341].
O. Packaging
The stability of muscle foods during storage may be influenced by the packaging
system. Vacuum packaging, which restricts the oxygen concentration, has been
shown in numerous studies to extend the shelf life of muscle foods
[328,330,331,342–347]. Similarly, oxidation was inhibited when an oxygen scavenger
was incorporated into the packaging [348]. In contrast, application of modified
atmospheres has produced variable results. Nolan et al. [349] found only minimal
improvement in rancidity and warmed-over flavor scores for precooked ground meat
packaged in CO2 or N2 compared with packaging in air, whereas Hwang et al. [350]
found that cooked beef loin slices packaged in an 80% N2 and 20% CO2 gas mixture
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