2006 Abstracts - American Society of Animal Science

100 Adipose tissue, lipids, and meat quality. S. Smith* and D.Lunt, Texas A&M University, College Station.Fat (or lipid) has marked effects on mouthfeel and flavor of meat, whichare primary components of palatability. The amount of fat and its fattyacid composition both influence palatability. The kinds of fatty acidspresent in meat and its cholesterol content also dictate the perceivedhealthfulness of meat. There are three sources of lipid in meat: themuscle fibers; subcutaneous adipose tissue; and intramuscular (marbling)adipose tissue. Most meat in the market place now is closelytrimmed of subcutaneous adipose tissue, so subcutaneous adipose tissuenow contributes little to fat and cholesterol intake. Once subcutaneousadipose tissue has been removed, the primary contributor to lipidcontent of meat is intramuscular adipose tissue. Lean beef, pork, orlamb, in which all subcutaneous and intermuscular (seam) adipose tissueshave been removed, contain approximately 1% extractable lipid.The composition of lipids in meat varies in response to diet and the ageof the animals at slaughter. The fatty acid composition of pork is especiallysensitive to dietary manipulation, whereas that of beef and lamb isaffected by the age of the animal and whether the animals are forage orgrain-fed. Meat from steers fed a corn-based diet to 525 kg BW hadmonounsaturated:saturated fatty acid (MUFA:SFA) ratios of 0.91,whereas feeding cattle a hay-based diet to the same BW resulted in meatwith a MUFA:SFA ratio of 0.72. Extended feeding (to 650 kg) increasedthe MUFA:SFA ratio in meat from corn-fed steers to 1.42, but increasedthe MUFA:SFA only to 1.22 in hay-fed steers. Melting points of lipidsfrom corn- and hay-fed steers raised to 525 kg were 37.9 and 42.8°C,respectively, whereas melting points of lipids from corn- and hay-fedsteers raised to 650 kg were 27.8 and 31.3°C, respectively. Cholesterolcontent of meat increased with BW, but was unaffected by diet. Theseresults indicate that pasture feeding causes harder fat, with lower concentrationsof monounsaturated fatty acids. Similar results can be obtainedin pork by feeding diets enriched with conjugated linoleic acid.Thus, some production practices can produce meat that may be perceivedas less healthful by consumers.Key Words: Adipose tissue, Fatty acids, Meat101 Intramuscular connective tissue and its role in meatquality. P. Purslow*, University of Guelph, Guelph, Ontario, Canada.Intramuscular connective tissue (IMCT) components of muscle have alarge contribution to the toughness of cooked meat. Three main aspectsof how and why this contribution can be highly variable are: 1) Variationsin amount, composition and spatial distribution of connectivetissues between muscles. Differences in tenderness between differentcuts are principally due to variations in IMCT content of the differentmuscles. This tremendous variation in the expression of a givenanimalâ€s genome theoretically represents good opportunity formanipulation of expression of connective tissue. 2) Variations duringthe development, growth, and especially during the physiological ageingor maturing of animals. IMCT guides muscle growth and repair and is aprime route through which some signals for muscle turnover and growthare transmitted to muscle cells. IMCT also coordinates force productionbetween adjacent muscle fibers and accommodates changes in muscleshape upon contraction. These functions are dominant in explaining thevariations in IMCT content between muscles with different mechanicalroles in the animal body. Connective tissue becomes stronger and moreresistant to solubilisation on cooking as an animal physiologically matures.The appearance of mature, covalent crosslinks coincides with thischange in physical properties. The control of turnover of IMCT may bea mechanism to combat this. There is evidence that increased turnoverof during compensatory growth increases connective tissue solubility.3) Variations produced on cooking, and how this may interact withageing. The connective tissue contribution to meat toughness increasesas meat is cooked from raw to approx 50-55°C and decreases thereafter,as shoen either from shear force measures on whole meat or directlyon IMCTcomponents isolated from cooked meat. Recent publicationshave again shown that IMCT is degraded during post-mortem ageing.This reduces the strength of IMCT in the raw state. However, as haslong been known, this degradation has no effect on the connective tissuecontribution to toughness after cooking at temperature of 60°C orhigher.Key Words: Meat texture, Connective tissue, Quality102 Effect of aging on tenderness of pork loin rib chops derivedfrom Berkshire swine. A. C. Naber*, K. M. Brueggemeier, S. J.Moeller, and H. N. Zerby, The Ohio State University, Columbus.The objective was to determine the effect of post-harvest aging ontenderness of pork loin rib chops derived from high quality purebredBerkshire swine. Thirty-eight purebred Berkshire barrows and gilts fedin a common contemporary group within a traditional swine finishingfacility were harvested on a single day in a commercial swine packingfacility. Bone-in, fat-on, whole loins from the right-hand side of thecarcass were removed at 18 h post-harvest and processed at 24 h postharvestat OSU. Five, 5.08 cm-thick loin chops were removed betweenthe fifth and last rib, vacuum-packaged and assigned to aging treatmentsof 1, 4, 7, 14, or 21 days. Chop orientation relative to days aged wasapproximately as follows: d 21 (5th to 7th rib), d 14 (7th to 9th rib), d1 (9th to 11th), d 7 (11th to 13th rib), d 4 (13th to last rib). Chops werestored at 0 to 4° C for their designated aging period and then frozen at -5° C. Frozen chops were cut to 2.54 cm, thawed at 2.20 C, and cookedin an Impingement oven set at 109.50 C to a target internal temperatureof 71° C. Cooked loin temperature was recorded. Chops were cooled to20° C and six, 1.27-cm cores were removed parallel to the muscle fiberorientation. Warner Bratzler Shear Force (WBS) measures representedthe average of the six cores per chop. The mixed model for WBS includedtreatment, sex, a covariate for the deviation of cooked temperaturefrom 71° C within a treatment, and a random pig effect. Leastsquares means for WBS in all age treatments were less than 3.0 kgindicating very desirable tenderness. No differences in WBS were observedwhen comparing d 1, d 4, and d 7 aging periods. However, WBSdeclined (P < 0.001) for d 14 and d 21 aging treatments when comparedwith d 1, d 4, and d 7, with no difference detected between WBS for d 14and d 21 post-harvest. Loins from barrows exhibited consistently less(P