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Fatty acid composition and iodine value of pork fat from 3 sampling locations in the carcass
The effect of sampling location (belly, jowl, and backfat) on fatty acid composition and iodine value (IV) of pork fat was evaluated in 90 pigs (barrows and gilts) that had been fed diets with a range of DDGS inclusion levels (0, 20, 40, 60%) from 23.4 ± 1.14 kg to 128.3 ± 2.15 kg BW. At the end of the growth period, pigs were harvested at a commercial plant and fat samples were collected from the belly (posterior to sternum), jowl (anterior end), and backfat (3rd thoracic vertebra). Fatty acid profile of fat samples from individual pigs was measured using gas chromatography (GC) and IV was predicted with an equation from AOCS (1998) based on unsaturated fatty acid content; IV was also measured using near infrared spectroscopy (NIR). The concentration of total saturated fatty acids (33.9, 30.0, and 33.3% for belly, jowl, and backfat, respectively; SEM 0.35), total monounsaturated fatty acids (43.1, 44.2, and 41.0%, respectively; SEM 0.28), total polyunsaturated fatty acids (23.0, 25.9, and 25.7%, respectively; SEM 0.52), and GC IV (74.9, 80.2, and 77.6 g/kg, respectively; SEM 0.71) differed (P < 0.05) between locations. Pearson correlations between GC IV for the 3 locations were between 0.80 to 0.90. The IV values measured using either GC or NIR were similar (P> 0.05) for all locations (e.g., IV of backfat sample was 77.6 and 77.6 g/kg for GC and NIR measurements, respectively) and the Pearson correlation between GC and NIR IV values were between 0.95 to 0.97 for the 3 locations. The results of this study, which was carried out with fat samples from pigs that had been reared under commercial conditions and fed a wide range of DDGS levels, suggest a relatively large effect of sampling location on fatty acid profile and IV, and that using NIR to measure IV gives comparable values to GC analysis.
Keywords: fat, IV, NIR