Antioxidant enzyme activities in beef in relation to oxidation of lipid and myoglobin

Lipid- and oxy-free radical generation has been implicated in oxidative processes which occur during meat maturation but the importance of the antioxidant enzyme (AOE) activity in these processes is not known. It was shown that metmyoglobin (MetMb) % and lipofuscin content were higher in colour-unstable muscles such as psoas major (PM) and diaphragma (D) compared to longissimus lumborum (LL) and tensor fasciae latae (TFL). Although Superoxide dismutase (SOD) activity is higher post mortem in PM and D muscles than in LL and TFL muscles, catalase and glutathione peroxidase (GPx) activities were higher only in D muscle. The higher AOE activity in colour-unstable muscles such as PM and D was not sufficient to prevent increased formation of MetMb and lipofuscin in these muscles compared to LL and TFL muscles.     

Titin content of beef in relation to tenderness

Steaks obtained from the longissimus dorsi muscle of 24 crossbred steers were subjected to four treatments (unaged raw, aged raw, unaged cooked, aged cooked) and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Titin migrated primarily as a single protein band in unaged raw samples (48 h post mortem), as a doublet in aged (16 days) raw samples, and as a triplet in unaged and aged cooked samples. Total titin band density remained constant among steaks that varied widely in Warner-Bratzler shear value, suggesting that beef steaks varying in tenderness contain the same amount of titin. It is concluded that titin content, as determined by gel electrophoresis, does not distinguish 'tough' from 'tender' beef.     

Quantitative determination of myoglobin and haemoglobin in beef by high-performance liquid chromatography

Three different HPLC columns were tested for their suitability for the analysis of myoglobin and haemoglobin in beef. Complete separation of the two proteins was obtained with an anion exchange column and a column based on hydrophobic interaction. With the latter column a recovery close to 100% was obtained for both proteins when they were added to meat extracts. For both proteins, the standard error of the mean for repeated analyses of ground beef was less than 2% of the detected amount. The method is considered as suited for quantitative routine analysis of myoglobin and haemoglobin in beef and beef products.     

Assessment of relative content of myoglobin, oxymyoglobin and metmyoglobin at the surface of beef

A method of calculating the relative content of myoglobin, metmyoglobin and oxymyoglobin at the surface of beef is described. It is based on measurements of reflex attenuance of incident light at the isobestic points 572, 525, 473 and 730 nm. The latter value corresponds to the achromatic attenuance of light at the meat surface and can be used as an objective measure of its lightness. It was shown that the colour image of the meat surface, and the relative amounts of these three myoglobin derivatives, are influenced by the opacity of the surface layer. A variability in the light diffusing properties of the meat surface may be considered to be the primary factor in creating differences of colour perception of meat derived from animals of the same species and of the same approximate age.     

Soil nitrogen analyses and their relation to nitrogen responses in winter wheat

Analyses for nitrate and ammonium were carried out periodically on surface soil samples, obtained at various times throughout the season, from a large number of nitrogen on winter wheat experimental sites. It was found that soil analyses for nitrate alone or nitrate plus ammonia were of no value for prediction of soil-nitrogen status and nitrogen-fertiliser responses in winter wheat. Responses of winter wheat to nitrogen fertiliser on freely drained soils where the nitrate nitrogen content of the soil was 15 ppm or more at sowing time were only reduced by this nitrate left over from the previous season when the November–February inclusive rainfall was less than 9 ins.     

Texture,composition and anatomy of spinach leaves in relation to nitrogen fertilization

BACKGROUND: The postharvest quality and shelf life of spinach are greatly influenced by cultural practices. Reduced spinach shelf life is a common quandary in the Salinas Valley, California, where current agronomic practices depend on high nitrogen (N) rates. This study aimed to describe the postharvest fracture properties of spinach leaves in relation to N fertilization, leaf age and spinach cultivar. RESULTS: Force–displacement curves, generated by a puncture test, showed a negative correlation between N fertilization and the toughness, stiffness and strength of spinach leaves (P > 0.05). Younger leaves (leaves 12 and 16) from all N treatments were tougher than older leaves (leaves 6 and 8) (P > 0.05). Leaves from the 50 and 75 ppm total N treatments irrespective of spinach cultivar had higher fracture properties and nutritional quality than leaves from other N treatments (P > 0.05). Total alcohol‐insoluble residues (AIR) and pectins were present at higher concentrations in low‐N grown plants. These plants also had smaller cells and intercellular spaces than high‐N grown leaves (P > 0.05). CONCLUSION: Observed changes in physicochemical and mechanical properties of spinach leaves due to excess nitrogen fertilization were significantly associated with greater postharvest leaf fragility and lower nutritional quality. Copyright © 2012 Society of Chemical Industry     

Tensile properties of cooked beef in relation to rigor temperature and tenderness

A study of the tensile properties of cooked strips from beef sternomandibularis which had gone into rigor at various temperatures showed no clear relationships with earlier observed variations in shear force with rigor temperature. A consistent feature of the load extension curves was a sudden increase in extensibility at a ‘change point’ of about 1 kg/cm². Some curves, particularly those for strips cooked under restraint, showed a third intermediate extensibility. Evidence points to modification of a myofibrillar component as the reason for the sudden changes.     

高压二氧化碳处理对牛通脊颜色和肌红蛋白的影响

在35℃、30min,不同压力(0、7、14、21、28、35MPa)和在35℃、21MPa,不同时间(0、10、20、30、40、50min)对牛通脊进行高压二氧化碳(HPCD)处理,测定肉的色泽和肌红蛋白(Mb)指标的变化。结果表明:HPCD处理能使肉由红色逐渐变成灰棕色,显著提高L*值(p<0.05)、降低a*值(p<0.01)。在35℃、30min条件下,7、14、21MPa的处理分别使L*值提高4.891、9.494、16.432;a*值降低1.575、3.573、5.872。同时,HPCD处理显著降低了肌红蛋白的总量(p<0.01),7～35MPa处理后分别降低了0.034、0.048、0.054、0.044、0.061mmol/L/L。另外,提高压力、延长时间也能显著降低高铁肌红蛋白(MetMb)比例(p<0.05),提高氧合肌红蛋白(MbO2)比例(p<0.01)。4℃冷藏7d后,与对照组相比,HPCD处理均能提高肌红蛋白的稳定性。该研究为HPCD技术在肉类中的应用提供理论参考。     

Evaluation of a dehydrated beef protein to replace sodium-based phosphates in injected beef strip loins

A dehydrated beef protein (DBP) was evaluated as a replacement for the phosphate added to beef injection brines. U.S. Select strip loins (n=20) were injected to 110% of their initial weight with a brine containing 3.6% salt and 4.5% sodium phosphate (CON) or 3.6% salt and 5% dehydrated beef protein (DBP). DBP loins had less fluid loss after 30 min. Steaks from both treatments lost similar amounts of fluid during storage. Total fluid loss was lower for DBP injected product. Lipid oxidation (TBARS) products were 0.23-0.60 mg/Kg higher for DBP steaks. DBP steaks were slightly less red than CON steaks according to instrumental measurements. Sensory panel evaluation, however, indicated no differences in redness. DBP steaks were less tender according to trained sensory panel. Results indicated the DBP to be effective in increasing brine retention and a viable alternative to phosphates when used in brines injected into beef strip steaks.     

Tenderness in relation to the temperature of rigor onset in cold shortened beef

Beef sternomandibularis muscle was cold shortened at 2°C for 24 h and then transferred to 37°C until rigor mortis was complete. In spite of a final shortening of 33%, the mean shear value after cooking was identical with that of unshortened meat which had gone into rigor at 15°C. Meat sent into rigor at 2°C with the same degree of shortening had twice the shear value. Thus raising the temperature to 37°C in the final stages of rigor completely nullifies the toughness seen in cold shortened meat, without affecting the shortening. Small changes in cooking loss run parallel to tenderness. The effects are not due to ageing, and may arise from modification of actin–myosin bonding. It is concluded that conditions during the last stages of rigor onset are more important to tenderness than the rest of the post-mortem history of the muscle.     

Quality and hygiene of beef burgers in relation to the addition of sodium ascorbate,sodium citrate and sodium acetate

We evaluated the effects of two additive mixtures (sodium ascorbate 1 g kg^?1, sodium citrate 1 g kg^?1 and sodium acetate 1.75 or 2.5 g kg^?1) on the microbiological and physical–chemical characteristics of non‐prepacked beef burgers stored in air at 4 °C or 12 °C for 96 h. Total microbial count reached 7 Log CFU g^?1 48 h later in treated samples at 4 °C. The mixture containing the higher acetate concentration led to a smaller increase in Gram‐negatives, in particular Pseudomonas (2 Log of difference towards control samples at 96 h); at 12 °C, a 1.7 Log difference in Enterobacteriaceae was also shown. Total viable basic nitrogen was significantly lower in the treated samples at 12 °C. The addition resulted in pH stabilisation and lower cooking loss and positively influenced the a* index of burgers at 4 °C. Clearly, the use of these mixtures should not be a substitute of good hygienic practices and optimal storage conditions.     

Determination of the myoglobin states in ground beef using non-invasive reflectance spectrometry and multivariate regression analysis

Seventy-two samples of ground beef from M. semimembranosus of two 5 and two 1.5 year old animals were prepared. Two types of fat tissues from either beef or pork were added to the ground beef. The samples were prepared to contain predominantly deoxymyoglobin (DMb), oxymyoglobin (OMb) and metmyoglobin (MMb) states on surfaces using selected methods based on chemical treatment (for MMb) and oxygen pressure packaging to induce the two other states. Reflectance spectra were measured on ground beef after three storage times. Partial least regression analysis was used to make calibration models of the desired myoglobin states. Validated models using leave-one-sample out cross validation gave, after correction and normalization, prediction errors of about 5%. Long term storage of ground beef was unsuitable for preparing pure MMb states due to gradual reduction of the pigment to DMb, presumably by bacteria.     

Evaluation of models to estimate urinary nitrogen and expected milk urea nitrogen

Milk urea nitrogen (MUN) has been introduced as a means to estimate urinary nitrogen (N) excretion and protein status of dairy cattle. For Holstein cows, the amount of urinary N excreted (g/d) was originally reported to be 12.54 x MUN (mg/dl), but recently urinary N (g/d) was reported to equal 17.64 x MUN (mg/dl). The objectives of the present study were to evaluate models to predict urinary N and expected MUN, by using older and newer data sets, and to quantify changes that may have occurred in MUN measurements over time. Two data sets were used for model evaluation. Data set 1 was from the spring of 1998 and data set 2 was from the spring of 1999. Similar cows and diets were used in both studies. By using data set 1, the newer model underestimated MUN by an average of 3.8 mg/dl, whereas the older model was accurate. By using data set 2, the older model overestimated MUN by 4.8 mg/ dl, but the newer model was accurate. In the period between the two studies, the MUN measured appeared to decrease by an average of 4.0 mg/dl. By using current wet chemistry methods to analyze for MUN, urinary N (mg/dl) can be predicted as 0.026 x MUN (mg/dl) x body weight (kg). Because of changes in methodology that occurred in the fall of 1998, target MUN concentrations have decreased to 8.5 to 11.5 mg/dl for most dairy herds compared with previous target concentrations of 12 to 16 mg/dl.     

Evaluation of an enzyme-linked immunosorbent assay for beef blood serum to determine indirectly the apparent beef content of beef joints and model mixtures

Evaluation of an enzyme-linked immunosorbent assay (ELISA) for the indirect quantification of beef using antibodies to blood serum is described. Results obtained using model mixtures of known composition agreed well with their calculated beef contents. Other meats, rusk and soya flour displayed negligible interference. Apparent percentages of beef based on blood sera levels were determined on 24 different joints of beef using a leg of beef as the standard reference material. A wide variation in the apparent percentage of beef was observed (54.4 to 175.7%) from one joint to another. The results suggest that a quantitative determination of beef in meat products using this particular antisera is not possible, unless the actual cut of beef used is known. The variation in the quantity of blood serum from one joint to another together with deterioration of the blood serum appear to be major problems. Although the method does not appear to be applicable to the quantification of beef it seems to provide a good qualitative test for beef.     

Effects of total iron, myoglobin, hemoglobin, and lipid oxidation of uncooked muscles on livery flavor development and volatiles of cooked beef steaks

Infraspinatus (IN), gluteus medius (GM), and psoas major (PM) steaks were obtained from A- and B-maturity carcasses with either high (6.0) or normal (5.7) pH, and either Slight or Small marbling. Steaks were vacuum aged either 7, 14, 21, or 35 d postmortem, and were broiled and served to a highly trained, flavor-profile sensory panel. Steaks with livery flavor were analyzed by gas chromatography/mass spectrometry for flavor compounds. Steaks aged 7 or 35 d postmortem were analyzed for myoglobin (Mb) and hemoglobin (Hb) concentrations and for total iron (Fe) (35 d steaks only). The IN had greater Fe (P < 0.05) than did the GM or PM. Livery flavor increased (P < 0.05) and beef flavor identification decreased (P < 0.05) in the GM as Fe increased. The PM had the lowest (P < 0.05) Mb/Fe ratios and highest (P < 0.05) Hb/Fe ratios. Several statistically significant, but relatively low correlations between 16-, 17-, and 18-carbon chain fatty acids and livery flavor resulted. Thirteen volatile compounds had higher concentrations in steaks with livery flavor than in those without livery flavor. Livery flavor development is a complex trait that can be affected by concentrations of total Fe, Mb, and fatty acids, but the relationships are relatively low.     

Early post-mortem conditions and the calpain/calpastatin system in relation to tenderness of double-muscled beef

Early post mortem temperature, pH, sarcomere length, colour, water holding capacity, calpain/calpastatin activities and myofibrillar protein concentrations (semi-quantative SDS-PAGE), measured at different times post mortem on 153 double-muscled Belgian Blue White bulls, were related to shear force (SF) measurements. The M. longissimus thoracis tenderised up to 8 days post mortem. SF was slightly correlated with temperature at 3 h post mortem (r = 0.20, p = 0.015), but not with pH early post mortem. Higher ultimate pH values measured at 24 h post mortem were related to darker meat, lower cooking losses and shorter sarcomere lengths. Sarcomere length was significantly related to SF, even after 12 days of ageing, suggesting that proteolytic activity was not able to overcome shortening. Up to 12 days post mortem, calpastatin and m-calpain activities were significantly correlated with SF suggesting a considerable role of calpains in meat tenderization of double-muscled Belgian Blue White bulls, although at 24 h post mortem, μ-calpain could no longer be detected. Titin, nebulin, filamin and troponin-T were degraded during the ageing period. Troponin-T was degraded by 80% between day 1 and 8. At 8 days post mortem its concentration was significantly correlated with 30 kDa (r = 0.63, p = 0.00), shear force (r = 0.39, p = 0.00), calpastatin activity at 1 day post mortem (r = 0.29, p = 0.01) and with the m-calpain/ calpastatin activity ratio at 1 day post mortem (r = -0.43, p = 0.00).     

Glutathione peroxidase activity,tissue and soluble selenium content in beef and pork in relation to meat ageing and pig RN phenotype

Since glutathione peroxidase (GSHPx) may be important for meat quality, its activity was examined in relation to animal species (beef and pork), muscle type (oxidative and glycolytic), selenium content, meat ageing and RN phenotype in Hampshire crossbred pigs. The GSHPx activity in bovine M. Longissimus dorsi [LD; 1.9 (0.4) U/g, mean (S.D.)] was significantly higher (P<0.001) than in M. Psoas major [PM; 1.5 (0.5) U/g] and the activities in the two muscles were correlated (r=0.66; P<0.001). Pork LD had a several fold lower GSHPx activity [0.4 (0.2) U/g] than bovine muscles but, in contrast, a somewhat higher content of selenium [113 (15) ng/g] than bovine LD [106 (12) ng/g] and PM [95 (17) ng/g]. The proportion of soluble selenium in bovine LD (72%) tended to be higher than that in bovine PM (64%), and it was significantly lower in pork LD (52%). Significant correlations between GSHPx activity and soluble selenium were obtained in both beef and pork. Thus, GSHPx activity varied among single animals, with species and muscle type, whereas meat ageing and pig RN phenotype had no effect.     

Capacitance, transepidermal water loss and causal level of sebum in healthy subjects in relation to site, sex and age

To determine normal levels of transepidermal water loss (TEWL), capacitance and sebum according to different sex and age groups, 93 healthy subjects were studied at 14 different anatomical locations with three different instruments: the Evaporimeter EP 1, the Corneometer CM 820, and the Sebumeter SM 810, evaluating respectively the transepidermal water loss, the capacitance and the causal level of sebum. Differences depending on the anatomical site were noticed. Unlike the capacitance, the transepidermal water loss and the causal level of sebum significantly decreased according to age. Furthermore, in some sites, male subjects showed a significantly higher transepidermal water loss than females, while hydration of the horny layer expressed by the capacitance showed an opposite trend. Correlations between the above-mentioned skin parameters were calculated: a positive correlation between TEWL and hydration was observed only at plantar and palmar areas.