RELATIONSHIPS OF SERUM, MUSCLE AND SUBCUTANEOUS LIPIDS TO BEEF CARCASS TRAITS AND FLAVOR

ABSTRACT— An examination of the means and range coefficients of the total serum, intramuscular (longissimus) and subcutaneous lipids, the major lipid classes and fatty acid compositions of the 3 tissue sites from 30 heifers and 31 bulls of the Hereford breed revealed some interesting aspects of lipid metabolism. When placed on a concentration (percent of tissue) basis, significant differences due to sex, environment and sires were shown by an analysis of variance for many of the lipid components. Phenotypic correlations, also computed on a concentration basis, gave indications of the growth and development of the animals, in addition to showing the associations of various lipid components of the 3 tissue sites to various carcass cutout traits and flavor. With a few exceptions, low positive correlations were shown for the serum lipid components with flavor, whereas, most of the marbling and subcutaneous fat components exhibited low negative correlations with flavor.     

REALIMENTATION OF CULL BEEF COWS. II. MEAT QUALITY OF MUSCLES FROM THE CHUCK, LOIN AND ROUND IN RESPONSE TO DIET AND ENHANCEMENT

From an experiment in which 60 beef cull cows were assigned to one of three feeding treatments, forage fed, high concentrate or high concentrate plus ractopamine, 10 muscles were removed from both sides of the carcass. Muscles from one side of the carcass were enhanced with a solution to target 0.3% salt and 0.3% phosphate in the final product. Minimal to no differences were observed in color, pH, sensory characteristics or shear force as a result of dietary treatment. Enhancement resulted in muscles with higher ( P ≤  0.05) pH and darker color. Sensory scores for juiciness and tenderness were improved ( P ≤  0.05) with enhancement. The Adductor was the only muscle not exhibiting lower shear values due to enhancement ( P >  0.05). To add further value to meat from cull cows, enhancement could be utilized, independent of feeding regimen prior to slaughter.

PRACTICAL APPLICATIONS

The use of enhancement in the beef industry has become common practice, particularly in beef from lower grading cattle. However, research examining the improvement in palatability with enhancement has focused mainly on younger cattle. Our research demonstrates that enhancement is able to improve the sensory characteristics of meat from cull cows.
Thus, in meat from older animals, which is usually characterized as being less palatable, enhancement could be used to improve the organoleptic traits. This practice may assist the beef industry in capturing further value from cull cows.     

THE EFFECTS OF DELAYED CHILLING AND ALTERED CARCASS SUSPENSION UPON BEEF MUSCLE: I. PHYSICAL AND TEXTURAL PROPERTIES

A total of 60 bovine carcasses from crossbred heifers, 12 to 16 months of age with carcass weights of approximately 260 kg were utilized in two related experiments to evaluate the effects of delayed chilling and altered carcass suspension on certain physical and textural properties of beef muscle. Hip-free suspension (suspension by the os coxae from a hook inserted through the obturator foramen with the limbs hanging free) significantly (P<0.05) reduced the shear force values obtained on samples from the longissimus dorsi (LD) and semimembranosus (SM) muscles but had no effect (P>0.05) on shear force values obtained on samples from the psoas major (PM) muscle. The only other physical property affected by altered carcass suspension was objective measurement of lean color in the SM. Carcasses suspended from the aitchbone had darker SM muscles. Delayed chilling treatments had no effect (P>0.05) on 2-h SM pH values or 144-h pH values for any of the muscles studied. However, carcasses held at either 13°C or 22°C for 24 h had higher (P<0.05) SM pH values. When delayed chilling treatments affected muscle color, treated sides had darker lean than their conventinally chilled counterparts. Textural properties (shear values and taste panel tenderness ratings) and amount of expressible juice generally were unaffected by the delayed chilling treatments evaluated.     

THE EFFECTS OF DELAYED CHILLING AND ALTERED CARCASS SUSPENSION UPON BEEF MUSCLE: II. HISTOLOGICAL AND CHEMICAL PROPERTIES

A total of 60 bovine carcasses from “exotic”— crossbred heifers, 12 to 16 months of age with carcass weights of approximately 260 kg were utilized in two separate but related experiments to evaluate the effects of delayed chilling at 2 temperatures (13 and 22°C) for 12 or 24 h and altered carcass suspension on certain histological and chemical properties of beef muscle. Hip-free suspension (suspension by the os coxae from hooks inserted through the obturator foramen with the limbs hanging free) produced substantially greater alteration of the histological properties of the muscles evaluated than did delayed chilling. Such alterations resulted in longer semimembranosus (SM) and longissimus dorsi (LD) sarcomeres, shorter psoas major (PM) sarcomeres, smaller SM and LD muscle fiber diameters, larger PM muscle fiber diameters, fewer SM and LD wavy fibers, more PM wavy fibers, and shorter SM muscle fiber fragment lengths (P<0.05). Neither hip-free suspension nor delayed chilling produced consistent differences (P<0.05) in either the intramuscular collagen content, the heat solubility of the intramuscular collagen, or the histological properties of the intramuscular collagen fibers.     

EFFECTS OF DRY AND MOIST HEAT ON SELECTED HISTOLOGICAL CHARACTERISTICS OF BEEF SEMIMEMBRANOSUS MUSCLE

ABSTRACT— Samples of raw and heat-treated beef semimembranosus muscle were examined histologically to determine how deep-fat frying, oven roasting, oven braising and pressure braising to 70°C affected histological characteristics of the muscle. A panel of three persons used an ocular micrometer to measure muscle fiber width, observed color and type of connective tissue and distribution of fat and estimated quantity of connective tissue of 475 histological sections. Differences among heat treatments in muscle fiber width and relative proportion of straight and wavy connective tissue were not significant. However, there was a significantly (P<0.05) larger quantity of granular tissue in deep-fat fried, pressure braised, and oven braised samples than in oven roasted samples. Intact fat cell walls were observed in both raw and heated samples.     

PHYSICAL, CHEMICAL, AND PALATABILITY TRAITS OF RAW AND PRECOOKED GROUND BEEF PATTIES

Boneless beef (U.S. Utility chucks or triangles; U.S. Choice plates) was ground (0.95 cm plate), standardized to 26% fat, reground (0.38 cm plate) and divided into two lots. One lot remained in Plant A and the other lot was shipped via air-freight to Plant B. On the same day and at the same time, meat at both Plants was formed into patties. Half of the patties at Plant A were precooked in a moisture-controlled oven broiler, half of the patties at Plant B were precooked in an open-hearth broiler; the remaining patties at each Plant were not precooked and were frozen in the raw state. Precooked and raw patties at both Plants were frozen (°30°C) in spiral air blast freezers, boxed, air-freighted to College Station, Tex. and Beltsville, Md. and stored at °20°C. Frozen patties were cooked to 63°C (11 mm at 190°C) and palatability was evaluated by an 84-member consumer panel and by an 8-member trained panel. Pre-cooking of ground beef patties: (a) reduces cube space-weight dimensions, thus economies would accrue in packaging-transportmg-distributing such product in comparison to requirements for raw patties; (b) increases total weight loss by approximately 1.8–9.4 percentage points; (c) resulted in increased moisture retention but increased loss of fat during final heating of product; (d) increases incidence of off-flavors by 7–16 percentage points and decreases flavor desirability if performed by use of a moisture-controlled oven broiler; (e) increases tenderness of heated patties; and (f) has no apparent effect on amount of organoleptically detectable connective tissue, flavor intensity or ready-to-serve appearance. It is very doubtful that the advantages in size reduction and tenderness are sufficient to offset the disadvantages in off-flavor incidence, in cooking-freezing-heating losses, in energy required to cool trie product after precooking, and in the necessity to use heat twice (once for precooking, once for heating prior to being served) to prepare the product for ultimate consumption.     

CORRELATIONS BETWEEN SERUM CONCENTRATIONS OF LEPTIN AND BEEF CARCASS COMPOSITION AND QUALITY

Steers (n = 84) of various genotypes raised under diverse management conditions from the 2001 Missouri State Beef carcass contest were used to evaluate the relationship between serum concentrations of leptin and beef carcass composition and quality. Serum and carcass data including hot carcass weight; adjusted 12^th rib fat thickness; percentage kidney; pelvic and heart fat (KPH); marbling score; and USDA yield grades were measured at harvest. Leptin was correlated with back fat thickness over the 12^th rib, yield grade, and marbling score (r = 0.35, r = 0.19, r = 0.26 , P < 0.10; respectively), but not with hot carcass weight, ribeye area, or KPH (P > 0.10). Serum concentrations of leptin may be useful to objectively evaluate carcass composition in fed cattle and may provide a means by which carcass quality can be predicted in the live animal.     

PORCINE LONGISSIMUS GLYCOLYTIC POTENTIAL LEVEL EFFECTS ON GROWTH PERFORMANCE, CARCASS, AND MEAT QUALITY CHARACTERISTICS

Animals (n = 72) with longissimus glycolytic potential (GP) values ranging from 113.8 to 301.1 μmol/g of tissue, were classified as having low (n = 24), moderate (n = 24), and high (n = 24) GP levels. Meat quality measurements such as longissimus ultimate pH and subjective color score decreased, while Hunter L* values, percentage drip loss and purge loss increased for animals classified as having either high or moderate GP levels compared to those with low GP values. Animals with higher GP had decreased longissimus protein content and improved taste panel tenderness scores and lower shear force indicating superior eating quality. Increasing aging time from 2 to 21 days decreased shear force and improved taste panel tenderness scores. These data indicate that both glycolytic potential level within the muscle and aging time can have significant effects on pork quality characteristics.     

CARCASS CHARACTERISTICS, SENSORY PROPERTIES AND MINERAL CONTENT OF MEAT FROM BULLS AND STEERS

Thirty-three bulls and 22 steers were slaughtered and subsequent carcasses were evaluated for carcass characteristics. Longissimus muscle samples were analyzed for sensory properties and concentrations of Cu, Fe and Zn. Bulls produced carcasses with older maturity characteristics, larger ribeyes, less fat and produced longissimus steaks that were less tender and had more organo-leptically detectable connective tissue than steaks from steers. Zn concentration was significantly correlated to skeletal maturity, fat thickness, ribeye area, connective tissue and tenderness before adjusting for sex. After adjusting for sex, mineral content did not significantly correlate as well with many carcass or sensory properties as before adjusting for sex.     

CATHEPTIC ACTIVITY, TEXTURAL PROPERTIES AND SURFACE ULTRASTRUCTURE OF POST-MORTEM BEEF MUSCLE

Catheptic enzyme release was studied in beef psoas muscle as a function of post-mortem aging. Textural qualities (tensile and shear) and fiber surface ultrastructure were examined. A crude (12-fold purification) catheptic fraction was prepared that exhibited the expected pH and temperature optima and was activated by dithiothreitol, EDTA and Triton X-100. When beef muscle was fractionated according to its solubility characteristics the susceptibility to proteolysis decreased: water soluble > salt soluble > insoluble. During post-mortem aging proteolytic activity decreased slightly at rigor, increased to day 6 and subsequently decreased. Shear force, breaking strength, ATP, break elongation and elasticity all dropped during the first 4 days, but the latter two parameters increased thereafter. The major alteration in fiber appearance through 2 days was shortening. Later, however, transverse striations became depressed and beginning at day 5 and continuing through the 2-wk period extensive fiber breakage occurred. The possibility that cathepsins play a role in these post-mortem events is considered.     

SPECTROPHOTOMETRY OF BEEF MUSCLE AND ADIPOSE TISSUE DURING HEATING AND COOLING

The effect of heating and cooling on the reflectance of beef was measured by fiber-optics. Triplicate samples of sternomandibularis and deep pectoral adipose tissue were heated from 20 to 80C, then cooled to 20C, over a 3 h period. Reflectance spectra were measured at every 5C. During heating, muscle reflectance from 400 to 700 nm increased to 70C, then decreased from 70 to 80C. During cooling, reflectance at most wavelengths decreased from 80 to 20C. However, in the Soret absorbance band at 440 nm, there was little change in reflectance during cooling from 80 to 20C. Thus, the 440/700 nm ratio of reflectance increased as muscles were heated, but changed little during cooling. During heating, adipose tissue reflectance from 400 to 700 nm decreased, then showed a further small decrease during cooling, so that optical changes were irreversible.     

PROCESSING AND PALATABILITY CHARACTERISTICS OF ROUND BEEF BACON

The objective of this study was to evaluate the effects of tumbling, maceration, and emulsion coating on the processing and palatability characteristics of round beef bacon. Fifty-one beef plates were cured and assigned to treatments: vacuum-tumbled (T); macerated and vacuum-tumbled (MT); macerated, emulsion-coated, and vacuum-tumbled (MET); and emulsion-coated and vacuum-tumbled (ET). Plates were rolled longitudinally, stuffed in fibrous casings, and smoked. Visual bind, visual appearance, and binding strength were lower (P < 0.05) for MET bacons than all other treatments. T bacons were more (P < 0.05) uniform in cured color than MET bacons. There were no differences (P > 0.05) among treatments for visual fat to lean ratio or sensory properties. ET bacons had higher processing yields (P < 0.05) than T or MT bacons, and T bacons higher processing yields (P < 0.05) than MT bacons. Results of this investigation indicate that only vacuum-tumbling is needed to produce an acceptable round beef bacon product.