Wednesday, May 9, 2012

2011 carcass comparision: pen vs. pasture

As part of last year's preliminary study comparing carcasses from pen-fed goats to carcasses from pasture-raised goats, a portion of the longissimus dorsi (rib eye) muscle from each carcass was submitted to Dr. Henry Zerby's meat lab at Ohio State University for further analysis. The analyses took several months. The results are presented here.

There was no difference in the percentage of protein or intramuscular fat in the samples from the pen vs. pasture-fed goats. The samples contained an average of 23.3 percent protein and 1.03 percent intramuscular fat.

The fatty acid data is much more complex and harder to interpret, as the percentages of 28 different fatty acids were compared. Statistical differences were detected in 8 of the 28 fatty acids that were measured.

The following table gives the number of grams of each fatty acid per 100 g of fat. The final column in the table indicates whether or not the differences measured were statistically significant. The meat from the pen-fed goats had a higher portion of mono-unsaturated fat (MUFA), whereas the meat from the pasture-raised goats had more poly-unsaturated (PUFA) and saturated fat (SFA). It is not known if any of these differences are relevant to human health.

Fatty acid nomenclature
A fatty acid is a carboxylic acid with an even number of carbon chains. Short-chained fatty acids have fewer than six carbons. Medium chained fatty acids have 6-12 carbons. Long-chained fatty acids have more than 12 carbons. Very long chained fatty acids have more than 22 carbons.

Fatty acids without double bonds between the carbon atoms (e.g. 14:0) are saturated fatty acids (SFA). Fatty acids with double bonds (e.g. 18:1) are unsaturated fatty acids. Monounsaturated fatty acids (MUFA) have one double bond (e.g. 18:1).  Polyunsaturated fatty acids (PUFA) have more than one double bond (e.g. 22:3) and can occur in either a cis or trans configuration.  

A cis configuration (e.g. 18:1 cis 11) means that adjacent hydrogen atoms are on the same side of the double bond. A trans configuration (e.g. 18:1 trans-11), by contrast, means that the next two hydrogen atoms are bound to opposite sides of the double bond. As a result, they do not cause the chain to bend much, and their shape is similar to straight saturated fatty acids.  These are trans fats.

A similar analysis will be done with the carcasses from this year's pen vs. pasture study.

Thanks to Dr. Dahlia J. O'Brien at Delaware State University for conducting the statistical analysis of the data. Thanks to Dr. Ken Turner from USDA-ARS for covering the cost of the meat analysis.