Page 256 - Natural Antioxidants, Applications in Foods of Animal Origin

Methods and Their Applications for Measuring 235
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FIGURE 6.23 Alpha linolenic (ω-3 fatty acid) fatty acid. This fatty acid is 4–5 times higher
in grass fed beef than grain fed beef, and is highly susceptible to oxidation. Modified from
ChemDraw software CambridgeSoft /Perkin-Elmer .
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The ω-3 fatty acids have seven important structural features.

1. The alpha carbon is associated with the carboxyl end of the molecule.
2. The approximate reactive site (allylic carbon) where peroxidation
and scission begin with the abstraction of the carbon atom.
3. The approximate reactive site (bis-allylic carbon) where peroxida-
tion and scission are most likely to occur during initial phases of
oxidation.
4. Hydrocarbon backbone (cis-C H ) of the fatty acid
2n
n
5. Unsaturated portion of the fatty acid (cis-C H )
n-2
n
6. ω-6 carbon
7. ω-3 carbon
To preserve the status of meat products in the consumer’s daily diet, some
meat processors offer conventional products reformulated with grass fed.
The data in Table 6.6 compare the fatty acid profiles between grass fed/grass
finished (95% lean) and grain fed (90% lean) beef forequarter and show
grass fed beef has a higher ω-3 fatty acid content. Small changes in levels
of unsaturated fatty acids significantly impact the oxidative stability (Wood
et al., 2003). Using analytical methods, oxidative stability can be monitored
when there are changes in the fatty acid composition in the meat formula.
Indices based on the fatty acid composition in raw beef, pork, poultry, and
finfish are shown. Indices that are positively correlated to nutritional value
also present shelf-life challenges.
Indices of nutritional value (bottom of Table 6.6) are IT, AI, and ratio of
desirable fatty acids (DFA) to the undesirable fatty acids (OFA) that elevates
low density lipoproteins (LDL).