Browning and Associated Properties of Porcine Muscle

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Abstract
SUMMARY— A split‐plot design was used to study browning and associated properties of LD muscles from 12 Duroc and 12 Poland China barrows. Pigs were: (1) untreated, (2) sugar‐fed 1 week before slaughter, and (3) fasted 48 hr, then exercised to exhaustion before slaughter. One half of each carcass was cooled at 30°F and the other at 42°F. Loins and hams were evaluated for “quality” using the Wisconsin 5‐point scale.Muscles from Durocs had more marbling and ether extract than muscles from Poland Chinas; total moisture and Gardner reflectance values (browning) were lower in muscles from Durocs than in those from Poland Chinas. Color and firmness scores for hams were not affected by breed, but firmness scores of loins were higher (P < 0.05) for Durocs than for Poland Chinas. Glycogen, pH and reducing sugar values were similar for both breeds.Antemortem treatment had no significant effect on marbling. Usually muscles of sugar‐fed pigs had the lowest; untreated pigs, intermediate; and exercised pigs the highest color and firmness scores. Glycogen was higher (P < 0.05) in muscles from sugar‐fed animals than in muscles from untreated or exercised animals. Muscles of sugar‐fed pigs had the highest reducing sugar and lowest pH and reflectance values; those of exercised pigs had the lowest reducing sugar and the highest pH and reflectance values. Untreated pigs had intermediate values for those factors.Muscles chilled at 42°F had lower firmness, color, and marbling scores and higher reducing sugar values than those chilled at 30°F. Simple correlation coefficients indicated relationships between reflectance values and total moisture, pH, ether extract, and reducing sugar; whereas, partial correlation coefficients indicated relationships between reflectance and ether extract and reducing sugar. As reducing sugar and/or ether extract increased, the degree of browning increased. Also, regression analyses indicated that ether extract and reducing sugar were the important factors affecting browning.