Compositional and instrumental firmness variations within fresh pork bellies

Fresh pork bellies (n=24) were cut into 15 sections to measure the intra-belly variation in compositional and mechanical firmness characteristics. Length and width of each belly was measured before the belly was divided into 3 rows (D = dorsal; C = central; and V = ventral) and 5 columns (labeled 1, 2, 3, 4, and 5 from cranial to caudal), resulting in 15 belly sections of equal dimensions. The belly section with the greatest compression value was D-1, whereas the lowest compression value was found in the V-4 section (column×row, P<0.001). Conversely, the greatest and least puncture values were observed in the C-2 and V-5 locations, respectively (column×row, P=0.016). The D-3 section had the lowest proportion of lean and the greatest proportion of fat, but the greatest lean and lowest fat percentages were found in the V-1 and C-4 sections, respectively (column×row, P<0.001). The greatest proportions of saturated fatty acids (SFA) were found in the V-4 and V-5, and the lowest proportions of SFA were in D-1 (column×row, P<0.001). Moreover, C-4 and V-1 had the greatest percentages of monounsaturated fatty acids (MUFA), whereas the lowest MUFA content was observed in D-1, D-2, and D-3 (column×row, P<0.001). The D row (columns 1, 2, 3, and 5) also had the greatest proportion of polyunsaturated fatty acids (PUFA), but the lowest proportions of PUFA were located in C-4, V-4, and V-5 (column×row, P<0.001). Consequently, the iodine value was greatest in D-1 and lowest in V-4, V-5, and C-5 (column×row, P<0.001). It is apparent from these results that there is an obvious fatty acid composition gradient within bellies, which results in considerable intra-belly variation in composition and firmness.