VARIATIONS IN THE SENSORY PROPERTIES OF BEEF AS AFFECTED BY SEX CONDITION, MUSCLE AND POSTMORTEM AGING

The longissimus (LD), biceps femoris (BF), psoas major (PM), semitendinosus (ST) and semimembranosus (SM) muscles from 8 bulls and 8 steers were removed from sides at 1 day postmortem and 7 days postmortem. The sensory and textural properties were evaluated and related to meat composition, meat characteristics and mineral content. Muscles were ranked in order of increasing sensory tenderness ratings: PM>ST>LD>BF>SM. The amount of intramuscular fat was found to be positively correlated to sensory panel tenderness ratings. The amount of intramuscular collagen was found to be negatively correlated to sensory panel tenderness ratings. Muscle concentrations of copper, iron and manganese were found to be positively correlated to tenderness ratings.     

EFFECT OF POSTMORTEM AGING ON CHICKEN MUSCLE LIPIDS

Neutral lipids of fresh chicken breast muscles are shown to be triglycerides, sterols and sterol esters with only traces of mono- and diglycerides and free fatty acids. Phospholipids include measurable quantities of phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl inositol, phosphatidyl serine, sphingomyelin, diphosphatidyl glycerol, lysophosphatidyl choline and lysophosphatidyl ethanolamine. Fatty acid analyses of several of the lipid fractions are also included. Decreases in phosphatidyl choline and phosphatidyl ethanolamine coupled with increases in lysophosphatidyl choline, lysophosphatidyl ethanolamine and free fatty acids after 48 hr postmortem in the cold indicate phospholipase A activity concurrent with other postmortem changes. The significance of the results is discussed.     

WATER-HOLDING AND COLOR CHARACTERISTICS OF BEEF FROM ELECTRICALLY STIMULATED CARCASSES

Electrical stimulation (ES) was applied to the right sides of 15 beef carcasses and the corresponding left sides were used as nonstimulated (NS) controls. Data collected included: postexsanguination pH (0.5, 3, 6, 24 h), L, a, and b color values, drip loss, and expressible moisture. Muscles from ES carcasses tended to have more accelerated postmortem pH declines than the corresponding muscles from NS carcasses. M. triceps brachii had a lower pH at 0.5 h (P < 0.05) , M. longissimus thoracis had a lower pH at 0.5 h (P = 0.055) and 3 h (P < 0.05), and M. semimembranosus had a lower pH at 0.5 and 3 h (P < 0.05), respectively. Hunter L, a, and b values did not differ within ES and NS treated muscles. Additionally, ES did not influence color values of the M. semimembranosus. ES did not affect drip loss or expressible moisture in beef muscles.     

DEVELOPMENT OF THE ARMOUR TENDEROMETER FOR TENDERNESS EVALUATION OF BEEF CARCASSES

A simple rapid non-destructive test and apparatus were developed for quantifying tenderness of beef carcasses. A probe with ten 1/2 inch diameter needles mounted on a manifold is pressed manually two inches into the rib eye. Measurements of maximum force during penetration into the cold rib eye on the day after slaughter correlated well with subjective panel tenderness scores on the same meat cooked after one week of aging.     

THE INFLUENCE OF AGING BEEF IN VACUUM

U.S. Choice grade beef loins and ribs were aged to determine the effect of vacuum packaging for 7 and 15 days at 32° and 40° F on sensory characteristics, microbial counts and weight loss. Vacuum packaging had no significant influence on tenderness, flavor and juiciness but produced a highly significant reduction in weight loss during aging. Surface bacterial counts were significantly less on the vacuum packaged portions than the portions not packaged.     

FECAL COLIFORM CONTAMINATION OF BEEF CARCASSES DURING THE SLAUGHTERING PROCESS

The purpose of this study was to determine the fecal coliform counts of beef carcasses during different stages in the slaughter process. A total of nine carcasses were selected at random in the abattoir. The samples were taken by excision from three different sites; rump, brisket and shoulder. The samples were collected from the same carcasses at four different stages of processing; after dressing, after evisceration, after washing and after chilling for 24 h in a chilling room. The processing steps did not increase the fecal coliform counts on the rump samples. There were no significant differences in the samples of rump and shoulder among different processing steps. The contamination level of the brisket after washing was significantly higher than other processing steps. Brisket and shoulder parts are critical points for microbiological sampling as these sites showed higher microbial counts after chilling steps. The data obtained have relevance for the planning of washing methods for the production of clean and safe carcasses.     

EFFECT OF POSTMORTEM AGING ON CHICKEN BREAST MUSCLE SARCOPLASMIC RETICULUM

FSR (fragmented sarcoplasmic reticulum) isolated from chicken breast muscle (Pectoralis major) at 0 hr, 48 hr and 7 day postmortem was purified using linear density gradient centrifugation. The Ca⁺⁺accumulating ability of the FSR was found to increase with postmortem aging. No loss in ATPase activity was noted nor was any significant change observed in the SDS-gel electrophoresis patterns of the proteins with postmortem aging. The FSR from the aged muscle contained a higher proportion of phospholipids These studies indicate that the Ca⁺⁺ sequestering properties of sarcoplasmic reticulum from chicken breast muscle are not impaired during postmortem aging.     

EFFECTS OF DIFFERENT AGING PROCEDURES ON THE PALATABILITY OF BEEF

Ten pairs of beef strip loins were obtained 48 h postmortem from ten good grade beef carcasses. Three steaks (2.5 cm thick) were cut from the loin end of each strip loin and the remaining portion retained as the subprimal. Steaks and subprimals were aged for 7 days at 2°C in the following treatments: polyvinyl chloride overwrapped steaks (PVC-ST), vacuum packaged steaks (VP-ST), vacuum packaged subprimals (VP-SP), and subprimals held in air (Air-SP). After aging of the subprimal, 3 additional steaks were cut for evaluation. The steaks from all treatments were evaluated for palatability and chemical characteristics. Palatability characteristics did not differ significantly (P > 0.05) between treatments with the exception of the off-flavor intensity of PVC-ST which was higher (P < 0.05) than other treatments. Warner-Bratzler shear values were similar for all treatments. No significant differences (P > 0.05) were observed between treatments for percent moisture, percent lipid, pH or TBA number. The results of this study indicate that aging method (air or vacuum) or type of cut (steaks or subprimals) had little effect on the palatability attributes or chemical characteristics of the beef strip loins.