EFFECT OF ELECTRICAL STIMULATION AND BLADE TENDERIZATION ON PALATABILITY OF BEEF LONGISSIMUS AND SEMIMEMBRANOSUS MUSCLES

The effect of electrical stimulation (ES) and/or blade tenderization (BT) on palatability of longissimus (LD) and semimembranosus (SM) muscles from range-grazed and concentrate-fed steers were compared. Range-grazed steers graded lower and the steaks contained less fat and more moisture (P<0.05) than those from concentrate-fed steers. Broiled steaks from the range-grazed steers were less flavorful, less juicy, and less desirable overall than those from concentrate-fed steers (P<0.05). Nevertheless, tenderness of ES and BT treated steaks from range-grazed steers was comparable to steaks from concentrate-fed animals that had not been tenderized. Flavor and juiciness of LD muscle did not change with ES or BT treatments but flavor and juiciness of SM muscle decreased when combined ES and BT treatments were used.     

INFLUENCE OF SEX AND POSTMORTEM AGING ON INTRAMUSCULAR AND SUBCUTANEOUS BOVINE LIPIDS

SUMMARY –Fifteen wholesale beef ribs from an equal number (5) of half-sib bulls, steers and heifers were used to study the changes in subcutaneous (SQ) and longissimus dorsi intramuscular (IM) lipids at 2, 7, 14 and 21 days post-mortem (PM). The progressively increasing free fatty acid (FFA) levels observed in both depots with time PM were paralleled by fatty acid composition changes. During the aging period the content of C14:0 in the FFA fraction decreased from 11.7–5.8%; the level of C18:1 increased from 42.6–49.7%. Cholesterol and phospholipid levels did not change with PM aging. PM aging had no effect on the composition of the IM phospholipid class, suggesting that autoxidation does not readily occur during aging of fresh beef ribs. Fatty acid composition of the bull IM lipid fractions frequently differed from the fatty acid composition of these fractions in heifers or steers; the latter two sexes had similar fatty acid compositions in their IM lipid fractions. In the SQ triglyceride fraction, heifers had higher and lower levels of C18:1 and C16:0, respectively, when compared to both bulls and steers. Traces of C22:6 were present in the IM free fatty acid fraction of heifers, whereas 3.2 and 4.1% were present in the FFA of steers and bulls, respectively. Rib steaks from heifers had significantly (P < .05) higher sensory panel scores for aroma and lower IM and SQ levels of FFA when compared to bulls. A significant (P < .01) correlation of -0.49 was obtained between aroma score and IM levels of FFA.     

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.     

EFFECT OF TOTAL LIPIDS, TRIACYLGLYCEROLS AND PHOSPHOLIPIDS ON MALONALDEHYDE CONTENT IN DIFFERENT TYPES OF CHICKEN MUSCLES AND THE CORRESPONDING SKIN

Total lipid extracted from chicken breast, thigh, drumstick and wing muscles and the corresponding skin was analyzed for triacylglycerols and phospholipids as well as their fatty acid composition and also for malonaldehyde and lipid oxidation fluorescent products (LOFP) content.
Muscles consist of only 1.2–3.2% lipid, but lipid concentration in the skin ranges from 22.2–31.7%. The percentage of phospholipid in muscle lipid was 20 times more than that of the skin. The fatty acids of triacylglycerols from muscles and skin contained less than 2% of polyunsaturated fatty acids (PUFA). Fatty acids from phospholipid of the meat contained over 15% arachidonic acid and substantial amounts of PUFA with 22 carbon atoms. Skin phospholipid had 10.6–13.2% of all PUFA.
Differences in the lipid composition of muscles and skin resulted in a concentration of malonaldehyde in muscle lipids of 30–50 mg/g, a value more than 15 times greater than in lipids of the skin. However, the TBA number of the skin was the same or a little bit lower as compared to muscles. The relative levels of LOFP in the organic phase of Folch-extracted muscle and skin tissues paralleled the trend found for malonaldehyde concentrations.
It was concluded that the simultaneous determination of total lipid content and malonaldehyde concentration in lipid extracted from various chicken muscles and corresponding skin was the most informative method for evaluation of precursors of lipid oxidation in fresh tissue.     

OXIDATION OF LIPIDS IN SARCOPLASMIC RETICULUM OF MUSCLES FROM PASTURE- AND GRAIN-FED CATTLE WITH OR WITHOUT VITAMIN E SUPPLEMENTATION

The effect of different α-tocopherol contents in sarcoplasmic reticulum (SR) membranes on lipid oxidation was investigated. Muscle membranes contain high contents of polyunsaturated fatty acids that are very susceptible to oxidation during chilled or frozen storage. SR was prepared from M. longissimus dorsi, M. semimembranosus and M. gluteus medius muscles of pasture- and grain-fed steers supplemented with vitamin E (0, 500 or 2500 IU α-tocopheryl acetate) for 105 -132 days. Vitamin E supplementation increased the α-tocopherol concentration in SR of grain-fed cattle but did not change that of pasture-fed cattle. SR from pasture-fed beef had more linolenic and less linoleic acid than that of grain-fed meat and, compared with the other treatment groups, SR of control grain-fed cattle was significantly more prone to lipid oxidation, corresponding with its lower α-tocopherol content. Thus, α-tocopherol content appears to play a major role in determining the extent of lipid oxidation in muscle membranes, especially in those from pasture-fed beef that contained more polyunsaturated fatty acids.     

INTRAMUSCULAR LIPIDS IN M. LONGISSIMUS DORSI FROM PORK, AS RELATED TO BREED AND SENSORY PROPERTIES

The content, composition and distribution of intramuscular lipids in M. longissimus dorsi (LD) of pure bred Hampshire, Swedish Landrace and Swedish Yorkshire pigs were investigated. The highest content of intramuscular lipids was found in Hampshire (2.0%). Swedish Yorkshire had on an average 1.8% intramuscular lipids and Swedish Landrace 1.4%. About 35% of the fatty acids are saturated, 51–56% are monounsaturated and 8–12% are polyunsaturated. The content, as well as the fatty acid composition of the intramuscular lipids, were influenced by breed and sex and most probably also by genetic factors. The intramuscular lipids were mainly found in fat depots containing 20 to 150 fat cells. The fat depots were situated in the perimysium and, to some extent, in the endomysium. The fat cells had mostly an elliptical shape. The diameter of the fat cells varied between 15 and 180 μm but a diameter of 30–60 μm was most frequently noted. An increase in fat depot size was related to an increase in fat cell diameter. For the Swedish Landrace breed a relationship between the sensory properties of LD and the content and the distribution of intramuscular lipids was noted. The sensory properties of Yorkshire were related to the content, composition and distribution of intramuscular lipids, whereas no relationship was noted for the Hampshire breed.     

MINERALS AND XENOBIOTIC RESIDUES IN THE EDIBLE TISSUES OF WILD AND POND-RAISED LOUISIANA CRAYFISH1

The popularity of Cajun cuisine has promoted the consumption of Louisiana crayfish, Procambarus clarkii. Tail meat and hepatopancreatic tissues of crayfish captured from two locations in the Atchafalaya River Basin and four open ponds were analyzed separately for xenobiotic metal and mineral composition using an inductively coupled plasma emission spectrometer (ICP) and chlorinated hydrocarbons by gas chromatograph (GC) with electron capture detector. Less than 3 mg/kg of toxic xenobiotic metals were found in the tail meats and less than 5 mg/kg in the hepatopancreatic tissues. Mineral concentrations were similar to those reported for other crustacean species. Occasional trace amounts of DDD and DDE were found present in tissue samples.     

DELINEATION OF PUNCTURE FORCES FOR EXOCARP AND MESOCARP TISSUES IN CUCUMBER FRUIT 1

A puncture test was used to differentiate exocarp (skin) and mesocarp tissues of fresh cucumbers for resistance to penetration. Optimum instrumental test conditions were a punch size of 3.15 mm diameter and crosshead speed of 5 cm/min. The force required to penetrate the exocarp of whole fruit was determined and was deemed to represent a composite of the exocarp and the underlying tissue. By placing 7 mm thick, longitudinal slices skin down on a die plate, failure forces representing the mesocarp and exocarp tissues were determined in fruit ranging from 2.5–5.5 cm diameter. Exocarp force measurements were not influenced by slice thicknesses greater than 1 mm. Mesocarp measurements were lower with thicker slices, and required uniformity of thickness to maximize precision. The exocarp was found to represent about 60% of the composite force required to penetrate whole cucumbers, regardless of fruit size. Toughness of both exocarp and mesocarp increased with fruit size. The relative contributions of exocarp to penetration of seven other fruits varied from 58 to 88%.     

DISTRIBUTION OF OCHRATOXIN A IN CHICKEN TISSUES AND EGGS

The kinetics of distribution of ochratoxin A (OA) in chicken tissues was studied. Day-old chicks were fed a starter diet alone or containing 1 ppm OA. After 5 weeks, all chicks were intubated with 50 μg ³H-OA per chick. The highest level of radioactivity was found in kidney and liver 8 hr after intubation. Peak levels of OA in kidney, liver and breast were found to be 12, 4, and 0.2 ppb, respectively. Over 90% of the radioactivity was eliminated 48 hr after intubation. Moreover, when laying hens were fed a diet containing 0.5 or 5.0 ppm of OA for 2 weeks, the highest levels of OA were found in the kidney (124 ppb) and liver (80 ppb) also. Levels of OA in breast, leg and eggs of laying hens were found to be 8, 7, and 2.8 ppb, respectively.     

POSTMORTEM CHANGES IN THE MECHANICAL PROPERTIES AND ULTRASTRUCTURE OF THE LONGISSIMUS IN TWO PORCINE BREEDS

Kinetics of postmortem muscle changes of two pig breeds were studied. pH was measured at 30 min (pH₁) and 26 h (pH₂) after slaughter. The longissimus thoracis et lumborum was used at 1, 2, 3, 6 and 14 days postmortem for measurements of sarcomere length and mechanical properties in the raw state, and cooking loss and mechanical properties after cooking. Electron microscopy was performed at 1, 6 and 14 days postmortem. pH₁ was higher and the maximum stress lower in Large Whites than in Pietrains. Maximum stress of cooked meat decreased with aging time in Large Whites but not in Pietrains. Ultrastructural changes were more obvious in Large Whites than in Pietrains through day 6, but breed differences were no longer observed at day 14. Meat from Pietrain pigs was tougher than that from Large White pigs and tenderized at a slower rate and to a lesser extent during aging.     

CHANGES IN TENDERNESS OF BEEF LONGISSIMUS DORSI AS RELATED TO MUSCLE COLOR AND pH

Longissimus dorsi shear values for carcasses of 168 steers, 147 heifers and 259 bulls, all slaughtered in the age range of 12–16 months, were correlated with postmortem pH values and postmortem change in pH. Neither the individual pH values nor degree of postmortem pH change were useful predictors of shear value for steer and heifer carcass (r² values less than 0.07). For bull carcasses, pH of the longissimus dorsi taken 24 hr postmortem was significantly correlated with shear value, (r =−0.7) and with meat color (r =+0.7). Sexes differed markedly in the range of 24 hr pH of the longissimus dorsi with none of the steers, 8% of the heifers and 49% of the bulls having values greater than 6.0.     

EFFECTS OF TYPES OF FAT AND OF RATES AND TEMPERATURES OF COMMINUTION ON DISPERSION OF LIPIDS IN FRANKFURTERS

ABSTRACT— The effect of time, temperature and rpm of comminution of emulsions was determined on the dispersion of approximately 25% of beef fat, pork fat or cottonseed oil in frankfurters. The numbers of lipid particles 5 μ or less in diameter increased in frankfurters containing either beef or pork fat as comminution was continued to higher temperatures, with pork fat dispersed more thoroughly. Fat tended to separate from frankfurters containing beef fat in particles 200 μ or more in diameter. In contrast, no specific degree of dispersion of particles 5 μ or less in diameter consistently indicated emulsion stability, or its lack. Increased rpm during comminution produced an increased dispersion of beef or pork fat. Under the same conditions pork fat was dispersed more finely than beef fat. Dispersion of cottonseed oil produced finely dispersed particles beyond the resolution of light microscopy, as was confirmed by electron microscopy which showed a substantial number of particles to be less than 1 μ in diameter.     

LIPIDS IN WILD RUMINANT ANIMALS AND STEERS

Lipid was extracted from the biceps femoris and longissimus dorsi muscles of pronghorn antelope, mule deer, elk, range steers and feedlot steers after being trimmed of subcutaneous fat and connective tissue. Muscles of game animals contained more phospholipids than those of steers and muscles of antelope and deer were higher in cholesterol. Muscles of feedlot steers contained the most total lipid and triglycerides. Polyunsaturated lipid was highest in muscles of game animals due to higher levels of phospholipids. Polyunsaturated:saturated lipid ratios were highest in muscles of game animals followed by those in the muscles of range steers and lastly by those in the muscles of feedlot steers. In addition, the proporation of 18:3, an omega-3 polyunsaturated fatty acid, in total polyunsaturated acids measured were higher in the muscles of game animals and range steers than in those of feedlot steers.     

AN INVESTIGATION OF TRANSPORT, LAIRAGE AND HIDE CLEANLINESS ON CAMPYLOBACTER PREVALENCE IN FEEDLOT CATTLE AND DRESSED CARCASSES

The aim of this study was to determine the effect of transport and lairage of cattle before slaughter had on the qualitative and quantitative shedding of Campylobacter in cattle feces, and hence on the prevalence of this pathogen on dressed carcasses. A cohort of 109 heifers aged 27 to 30 months from a single Irish feedlot was investigated. Individual rectal fecal samples were taken from all of the cattle at the feedlot, after transport and at the end of lairage. The entire outer and inner surfaces of a carcass side of each animal were then swabbed immediately following slaughter and dressing.
Campylobacter spp. were isolated from 191 (58%) of the 327 fecal samples analyzed. Of the 191 isolates recovered in the study, 62 (57%), 60 (55%) and 69 (63%) were isolated from farm, posttransport and postlairage samples, respectively. There was no Campylobacter spp. isolated from the dressed carcasses. A trend of decreasing numbers of Campylobacter shed per gram of feces between sampling at farm and postlairage was observed. This reduction was significant for visit 1 (P < 0.05 ).
The key findings of this study were that transport and lairage did not result in an increase in the number of animals shedding Campylobacter spp. in feces and with appropriate standards of abattoir hygiene a low prevalence of this pathogen can be achieved on dressed carcasses.