Meat quality of Nguni, Bonsmara and Aberdeen Angus steers raised on natural pasture in the Eastern Cape, South Africa

The current study compared meat quality of Nguni, Bonsmara and Angus steers raised on natural pasture. Fifteen seven-month-old weaners of each breed were kept at the University of Fort Hare Farm for 12 months till slaughter. Monthly weights of the steers were recorded. Carcasses were electrically stimulated. The m. longissimus thoracis et lumborum was sampled for the measurement of meat colour, pH, drip loss, sarcomere length, myofibrillar fragmentation length and Warner Bratzler (WB) shear force. The Nguni had the highest (P < 0.05) average daily gain. Bonsmara and Angus steers had higher (P < 0.05) carcass weight and dressing percentage than the Nguni steers. Meat quality characteristics were similar among all the breeds except that Nguni meat was darker (L^∗) (P < 0.05) than meat from the other two breeds. The respective L^∗ values for Nguni, Bonsmara and Angus steers were 36.5, 38.6 and 39.9. There were significant (P < 0.05) correlations among some meat quality traits. There were significant (P < 0.05) correlations between WB values of meat aged for 2 and 21 days in Nguni and Bonsmara, but not in Angus. Meat quality from Nguni compares favourably with that from established breeds, when raised on natural pasture.     

Effects of rapid chilling of carcasses and time of deboning on weight loss and technological quality of pork semimembranosus muscle

The effect of rapid air chilling of carcasses in the first 3 h of chilling at −31 °C (then at 2–4 °C, till 24 h post-mortem) and the possibility of earlier deboning (8 h post-mortem) after rapid air chilling, compared to conventional air chilling (at 2–4 °C, till 24 h post-mortem) on weight loss and technological quality (pH value, tenderness, drip loss, cooking loss and colour - L^*a^*b^* values) of pork M. semimembranosus was investigated. Under the rapid chilling conditions, weight loss was 0.8% at 8 h post-mortem and increased to 1.4% at 24 h post-mortem when weight loss was 2.0% under conventional chilling. Carcasses that were rapid chilled had significantly lower (P < 0.001) internal temperature in the deep leg at 4 (25.7 °C), 6 (13.0 °C), 8 (6.2 °C) and 24 h (3.8 °C) post-mortem compared to conventional chill treatment (32.7, 24.2, 19.1 and 5.1 °C, respectively). Rapid chilling reduced significantly (P < 0.05) the rate of pH value decline at 8 h (6.02) post-mortem in M. semimembranosus compared to conventional chill treatment (5.88). Compared to conventional chilling, in M. semimembranosus deboned in different time post-mortem, rapid chilling had a positive significant effect on drip loss (P < 0.05, muscles deboned 8 h post-mortem), cooking loss (P < 0.001) and incidence of pale colour (L^* value). Rapid chilling i.e. rapid chilling and earlier deboning had neither positive nor negative significant effects (P > 0.05) on other investigated technological quality parameters of M. semimembranosus (tenderness, a^* value and b^* value) compared to conventional chilling.     

Effects of ionizing irradiation and hydrostatic pressure on Escherichia coli O157:H7 inactivation, chemical composition, and sensory acceptability of ground beef patties

A randomized complete block design with three replications was utilized to determine the effects of ionizing irradiation and hydrostatic pressure on the inactivation of Escherichia coli O157:H7, volatile composition, and consumer acceptability (n = 155) of frozen ground beef patties. E-beam and X-ray irradiation (2 kGy) inactivated E. coli O157:H7 below the limit of detection, while hydrostatic pressure treatment (300 mPa for 5 min at 4 °C) did not inactivate this pathogen. Solid-phase microextraction (SPME) was used to extract volatile compounds from treated ground beef patties. Irradiation and hydrostatic pressure altered the volatile composition (P < 0.05) of the ground beef patties in respect to radiolytic products. However, results were inconclusive on whether these differences were great enough to use this method to differentiate between irradiated and non-irradiated samples in a commercial setting. Irradiation did not affect (P > 0.05) consumer acceptability of ground beef patties when compared to untreated samples, but hydrostatic pressure caused decreased acceptability (P < 0.05) when compared to other treatments.     

Influence of sonication on Warner-Bratzler shear force,colour and myoglobin of beef (<Emphasis Type="Italic">m. semimembranosus</Emphasis>)

Research in the past few decades has shown the potential benefits of using ultrasound treatment as a technique to enhance tenderness and sensory properties of meat and its sub-products. The objective of current study was to assess whether the low-frequency, low-intensity ultrasound treatment at 24 h postmortem affects the pH, Warner-Bratzler shear force (WBSF), colour (CIE L^*a^*b^*c^*H°), and relative proportions of myoglobin (Mb) redox forms and total Mb concentration during 96 h of beef (musculus semimembranosus) storage. Muscles were obtained from young bulls (n = 15) of Lowland Black and White breed slaughtered at a live weight of 475 (SD 16.1) kg. Ultrasound treatment did not have a statistically significant (p < 0.05) effect on the pH of meat directly after sonication (24 h postmortem), or at 72 and 96 h postmortem. Sonicated meat sample (S) was characterized by higher, but not statistically significant (p < 0.05), L* coordinate values 24, 48 and 72 h postmortem. During the whole storage period, colour coordinates a*b*c* and H° were not significantly (p < 0.05) affected by sonication. Ultrasound treatment accelerated the total colour change ΔE, limited the formation of MbO₂ and slowed down the formation of MetMb. Measurements carried out 48 and 72 h after slaughter revealed that the ultrasound treatment significantly (p < 0.05) reduced the WBSF. This study demonstrates the potential of low-frequency, low-intensity ultrasound treatment at 24 h postmortem for beef tenderization without detrimental effects on its CIE colour parameters and relative proportions of Mb redox forms.     

Effect of lactate-enhancement, modified atmosphere packaging, and muscle source on the internal cooked colour of beef steaks

Earlier studies on lactate-mediated colour stability in beef did not address the possible influence on cooked colour. Our objective was to examine the effect of lactate-enhancement, muscle source, and modified atmosphere packaging (MAP) on the internal cooked colour of beef steaks. Longissimus lumborum (LL) and Psoas major (PM) muscles from 16 (n = 16) beef carcasses (USDA Select) were randomly assigned to 4 enhancement treatments (non-injected control, distilled water-enhanced control, 1.25% and 2.5% lactate), and fabricated into 2.54-cm steaks. Steaks were individually packaged in either vacuum (VP), high-oxygen MAP (HIOX; 80% O₂ + 20% CO₂), or carbon monoxide MAP (CO; 0.4% CO + 19.6% CO₂ + 80% N₂), and stored for 0, 5, or 9 days at 1 °C. At the end of storage, surface and internal colour (visual and instrumental) was measured on raw steaks. Steaks were cooked to an internal temperature of 71 °C, and internal cooked colour (visual and instrumental) was evaluated. Lactate-enhancement at 2.5% level resulted in darker (P < 0.05) cooked interiors than other treatments. Interior cooked redness decreased (P < 0.05) during storage for steaks in VP and HIOX, whereas it was stable for steaks in CO. Our findings indicated that the beef industry could utilise a combination of lactate-enhancement and CO MAP to minimise premature browning in whole-muscle beef steaks.     

Ohmic cooking of whole beef muscle – Optimisation of meat preparation

Uniform ohmic heating of solid foods primarily depends on the uniformity of electrolyte distribution within the product. Different preparation techniques were tested in an attempt to ensure an even salt dispersion within a full beef muscle (biceps femoris). Meat pieces were soaked, injected and tumbled using a range of procedures before ohmic cooking at pasteurization temperatures. A final preparation method (multi-injection (five points) with a 3% salt solution followed by 16 h tumbling) was validated. Selected quality parameters of the ohmically cooked products were compared to steam cooked products. Ohmically heated meat had a significantly (P < 0.05) uniform lighter and less red colour. Cook loss was significantly lower (P < 0.05) in ohmic samples and in relation to tenderness ohmic heated samples were tougher (P < 0.05) though the difference was only 5.08 N. Comparable cook values were attained in the ohmic and conventionally cooked products.     

Microbial and physicochemical succession in fermented sausages produced with bacteriocinogenic culture of Lactobacillus sakei and semi-purified bacteriocin mesenterocin Y

The influence of the bacteriocinogenic culture Lactobacillus sakei (10⁵/g) and semi-purified bacteriocin mesenterocin Y (2560 AU/kg) on the safety and quality of traditional Croatian fermented sausages was investigated. The addition of Lb. sakei and/or mesenterocin Y reduced microbial counts (P < 0.05) in the final products. After 28 days of ripening, coagulase-negative cocci decreased 1.5–2.0 log, yeasts 1.2–1.4 log and enterococci 1.7–2.7 log. In the case of the addition of Lb. sakei, the lactic acid bacteria count was significantly (P < 0.05) higher at day 7 of ripening, and was accompanied by a lower pH and a higher amount of lactic acid (P < 0.05). In the final product the amount of acetic acid was significantly lower. More intensive proteolysis and an increase in ammonia content were found at the beginning of fermentation, and in the second phase of ripening in the control samples, respectively. The free fatty acid concentration was significantly lower during the entire ripening process compared to the control (P < 0.05). Semi-purified mesenterocin Y did not affect the sensory properties of the sausages, whilst the addition of Lb. sakei enhanced them.     

Microbial translocation of needle-free versus traditional needle injection-enhanced beef strip loins

Our objective was to determine the effects of needle-free (NF) versus needle injection (N) enhancement on microbial translocation of generic Escherichia coli in beef strip loins. Fifteen longissimus muscles (LM) were obtained and halved. Surfaces were inoculated with generic E. coli at a level of 10⁶ CFU/cm² (three replications of five strip loins). LM halves were injection-enhanced with a phosphate and salt solution with either NF or N injection. After injection, two cores were taken from each LM half and sliced cross-sectionally at depths of 2-mm (surface), 1, 3, and 5 cm. The paired samples were stomached, serially diluted, and plated. Surface samples from N-injected muscles had lower (P < 0.05) E. coli counts (2.79 versus 3.23 log CFU/g for NF). Also, the 3- and 5-cm depth samples from N injection had the least (P < 0.05) E. coli contamination (1.69 versus 2.12 CFU/g for NF). Although traditional N injection resulted in approximately 0.5 log CFU/g less microbial contamination at all depths, because the level of contamination was extremely high, the difference in the treatments could arguably be of little practical importance in terms of safety.     

Effects of vitamin A supplementation and weaning age on serum and liver retinol concentrations, carcass traits, and lipid composition in market beef cattle

Angus crossbred steers (n = 48) were either early-weaned (EW) at 137 days or weaned at a traditional age (TW) of 199 days to determine effects of weaning age and dietary vitamin A on serum and liver retinol, carcass traits, and lipid composition. Steers from both weaning ages were allotted to receive either 42,180 IU vitamin A/day (HA) or no supplemental vitamin A (NA). Early-weaned and TW steers consumed vitamin A treatments for 235 and 175 days, respectively. Serum and liver retinol of HA steers were dramatically higher (P < 0.01) than those of NA steers at the end of finishing. Steers were harvested in two groups 35 days apart at an average ultrasound 12th rib fat thickness of 1.0 cm. Live and HCW were similar (P > 0.10) between NA and HA steers, but HA steers had numerically greater (P  0.10) fat thickness (1.05 vs. 0.87 cm). Marbling score and %IMF fat were numerically (P > 0.10) higher for EWNA than EWHA steers. Ratio of marbling score/12th rib fat thickness was greater (P = 0.08), and ratios of either marbling or %IMF per unit of 12th rib fat thickness, days on finishing diet, unit of HCW, and tenth of yield grade consistently favored steers fed NA, particularly EW steers. Proportions of serum fatty acids changed (P < 0.05) during finishing; proportions of individual fatty acids of the longissimus muscle did not change. Restricting vitamin A during finishing has potential to increase carcass marbling and to decrease waste fat, particularly for EW.     

Dietary administration of ewe diets with a distillate from rosemary leaves (Rosmarinus officinalis L.): Influence on lamb meat quality

The effect of including distilled rosemary leaf in the diet of pregnant ewes on subsequent lamb meat quality was studied. Thirty-six Segureña ewes were randomly assigned to three homogeneous groups. One group was fed a basal diet (BD) as control while the diet of the other two groups was modified by substituting 10% (R₁) and 20% (R₂) of the BD with a pellet made from 50% barley and 50% of distilled rosemary leaves (DRL). Meat spoilage (TVC, PSY and MYC), TBARS, CIELab coordinates and the sensory characteristics contribution of fresh lamb meat packed in MAP (70% O₂:30% CO₂) were analyzed on days 0, 7, 14 and 21. In general, R₁ and R₂ had higher a^* values, better scores for meat and fat colour (P < 0.05) and lower TBARS and rancid odour (P < 0.05), than the control samples. The total viable count was lower in meat DRL. No statistically significant differences were detected between the two treatments (10–20% DRL).     

Pseudomonas spp. convert metmyoglobin into deoxymyoglobin

Meat ‘reddening’ by bacteria was observed in chilled beef. To identify the reddening bacteria, isolates were inoculated onto beef and the changes in CIE L^*a^*b^* values monitored. As a result, two Pseudomonas spp., including Pseudomonas fragi which is commonly observed in raw meat, were selected and identified as reddening bacteria. The reddening was coincidentally occurred with the appearance of slime, and the increase in thiobarbituric acid-reactive substances (TBARS) was simultaneously suppressed. In myoglobin-containing nutrient broth, it is shown spectroscopically that P. fragi converted metmyoglobin into deoxymyoglobin. It was concluded that the meat reddening was due to the formation of deoxymyoglobin, induced by the very-low-oxygen tension brought about by Pseudomonad’s oxygen consumption: This oxygen depletion simultaneously suppressed TBARS increase.     

Effect of Zataria multiflora Boiss. essential oil and nisin on Salmonella typhimurium and Staphylococcus aureus in a food model system and on the bacterial cell membranes

The effects of different concentrations of Zataria multiflora Boiss. essential oil (EO: 0, 5, 15 and 30 μl 100 ml⁻¹) and nisin (N: 0, 0.25 and 0.5 μg ml⁻¹), temperatures (T: 25 and 8 °C), and storage times (up to 21 days) on growth of Salmonella typhimurium and Staphylococcus aureus in a commercial barley soup were evaluated in a factorial design study. The growth of S. typhimurium was significantly (P < 0.05) decreased by EO concentrations and their combinations with N concentrations at 8 °C. For S. aureus, the viable count was significantly (P < 0.05) inhibited by EO and N concentrations and their combinations, incubated at both storage temperatures. The mechanism of the antimicrobial action of EO, N, and their combinations against cell membranes of the tested organisms were also studied by measurement of the release of cell constituents and by the electronic microscopy observations of the cells. The significant increase of the cell constituents’ release of both organisms was observed as a result of treatments with EO and EO in combination with N. Electronic microscopy observations revealed that the cell membranes of S. typhimurium treated by EO and EO in combination with N were significantly damaged, while cells treated with only N looked similar to untreated cells. The electron micrographs of treated cells of S. aureus with EO, N, and their combination also showed important morphological damages and disrupted membranes.     

Consumer acceptance and steak cutting yields of beef top sirloin and knuckle subprimals

Beef knuckles (n = 150) and center-cut top sirloin butts (n = 150) were used to determine portion-controlled steak cutting yields, palatability characteristics, and consumer acceptance of rectus femoris (RF), vastus lateralis (VL), and gluteus medius (GM) steaks. Steak yields were higher (P < 0.05) for top sirloins than knuckles. Trained sensory panel ratings for overall tenderness, juiciness, and flavor were similar between RF and GM. Consumer panel ratings for tenderness and juiciness were higher (P < 0.05) for GM than RF; however, consumer perceptions of overall like and flavor were similar for GM and RF. Vastus lateralis received lower (P < 0.05) trained panel and consumer ratings for all traits than either RF or GM. Palatability of VL will need improvement to be a viable foodservice offering. Yet, these data suggest that RF would amply substitute for GM in foodservice settings, and that knuckle steak yields would be adequate for foodservice applications.     

Physicochemical change and protein oxidation in porcine longissimus dorsi as influenced by different freeze–thaw cycles

Effects of different freeze–thaw cycles (0, 1, 3 and 5) on physicochemical change and protein oxidation in porcine longissimus dorsi were investigated. When the number of freeze–thaw cycles increased, the thawing losses, cooking loss and b*-value increased (P < 0.05), a*-value decreased (P < 0.05). The cutting forces of pork increased after one cycle of freeze–thaw (from 28.3 N to 40.4 N) (P < 0.05), but the further increase of freeze–thaw cycles would lead to decrease of cutting force. The decreases in Ca²⁺- and K⁺-ATPase activity and sulfhydryl group (P < 0.05) content with concomitant increases in carbonyl content and thiobarbituric acid-reactive substances (TBARS) value (P < 0.05) showed that multiple freeze–thaw could cause the porcine protein and fat oxidation, especially for the pork subjected to five freeze–thaw cycles. Gel electrophoresis patterns of porcine muscle showed that multiple freeze–thaw cycles could cause cross-linking of protein in myofibril. Overall, the freeze–thaw process has a detrimental effect on the quality of pork.     

Fresh and cooked color of dark-cutting beef can be altered by post-rigor enhancement with lactic acid

Fresh and cooked color of dark-cutting (DC) beef strip loins (mean pH = 6.56) enhanced with 0.25, 0.50, 0.75 or 1.00% lactic acid (LA) were compared to non-enhanced DC and normal pH (NpH; mean pH = 5.43) strip loins. Even though NpH steaks received the most (P < 0.05) desirable fresh color scores, color scores for steaks from DC sections enhanced with 0.25% LA approached those of NpH steaks after the first day of retail display. Discoloration scores were also similar (P > 0.05) among NpH and 0.25% LA-enhanced DC steaks throughout the 5 d of display. Fresh steaks from NpH strip loins were redder, as evidenced by greater (P < 0.05) a^* values and lower (P < 0.05) hue angles, than DC steaks and DC steaks enhanced with LA, regardless of concentration. However, cooked color scores and proportions of denatured myoglobin were similar (P > 0.05) between untreated NpH steaks and DC steaks enhanced with 0.25% LA. Results from this study indicate that enhancing DC beef with LA may lead to the brightening of the fresh color and prevention of the persistent red cooked color, approaching that of NpH beef.     

Amino acids effects on heterocyclic amines formation and physicochemical properties in pan-fried beef patties

The effects of surface application of amino acids on the formation of heterocyclic amines (HCAs) and meat quality properties were evaluated in pan-fried beef patties (230 °C/15 min). Tryptophan, lysine, leucine, and proline at three concentrations, 0.05%, 0.20%, and 0.50% (w/w), were tested. The meat crusts were analyzed for HCA content using liquid chromatography-tandem mass spectrometry. Results showed that surface application of all tested amino acids significantly reduced total HCA content (P < 0.05), and the interaction of amino acid type and concentration significantly affected (P < 0.05) both individual and total HCA formation. Tryptophan at 0.50% reduced total HCAs the most (0.92 ng/g, 93% inhibition), followed by 0.50% lysine (1.94 ng/g, 84% inhibition), while leucine (3.95 ng/g, 64% inhibition) and proline (4.71 ng/g, 56% inhibition) were less effective at 0.50%. In addition, applying amino acids to meat surface significantly influenced (P < 0.05) pH and surface color change of beef crusts; particularly, lysine at 0.20% and 0.50% increased pH and a^* (redness) but reduced b^* (yellowness), while tryptophan and leucine at 0.50% increased L^* (whiteness). No significant effect was observed on cooking loss. Adding amino acids at 0.50% affected (P < 0.05) formation of aldehydes and pyrazines (as the key flavor compounds of fried beef). Overall, the results of this study suggested that adding amino acids to ground beef patties could effectively mitigate mutagenic HCA formation during cooking.     

The effects of extended curing on the microbiological, physicochemical and sensorial characteristics of Cecina de León

The objective of this study was to evaluate the effects of curing times on the characteristics of 7-month dry-cured beef cecina stored for up to 12-months at 16 °C and 65% relative humidity. Microbiological and physicochemical parameters, sensorial properties and consumer preferences were analysed at three different processing times (210, 270 and 360 days). Curing time significantly affected (p < 0.05) most of the parameters studied. Moisture and a_w decreased (p < 0.05) and NaCl content increased from day 210 to day 360, whereas microbial counts decreased (p < 0.05) from day 210 to day 360. The continued increase of amino acid content and free fatty acid (p < 0.05) until day 360 contributed to modifications in the characteristics of the final product. Thus, cecina with longer processing times had higher scores for colour, flavour and aftertaste. Consumer preferences indicated that the sensory quality of cecina improved from day 210 to day 270 of processing, after which no further changes were noted as curing was extended to 360 days.     

Disparity of dietary effects on collagen characteristics and toughness between two beef muscles

Manipulation of growth rate and/or diet has been shown to affect protein turnover and may be used to improve beef quality. This trial was conducted to evaluate the effects of average daily gain (ADG) and diet on animal performance, collagen characteristics and beef quality of two different muscles; longissimus dorsi (LD) and semitendinosus (ST). Seventy six Hereford and Angus steers were assigned to three dietary management regimens for finishing: high grain diet based on corn (n = 28), alfalfa pasture (n = 22) and grass pasture (n = 26). Average daily gains were greater (P < 0.001) in Herefords vs. Angus and for corn- vs. pasture finished cattle. Overall, total collagen content was greater (P < 0.001) and the percentage of total collagen that was heat soluble was lower (P < 0.0001) for ST than for LD muscle. The lowest (P < 0.05) values for both total and heat soluble collagens were found in animals finished on corn. WBSF values for LD were greater (P < 0.01) in grass-fed vs. alfalfa- and grain-finished cattle while there was no difference in WBSF values for ST between grass- and corn-fed animals. No correlation between ADG and WBSF was observed for any muscle. ADG was not correlated with collagen solubility in ST, but was correlated (P < 0.05) with collagen solubility in LD. A key finding is that growth rate affected heat soluble collagen in the two muscles to a different extent. In conclusion, this study shows that different feeding strategies may not influence the tenderness of all muscles in a similar way.     

Consumer acceptability and physiochemical characteristics of modified atmosphere packed beef steaks

The objective of this study was to investigate the physiochemical changes of beef steaks packed under various combinations of gasses and the relationship between consumer perception of flavour and acceptability of modified atmosphere packed beef steaks during retail display. Experimental gas atmospheres included: 40%, 50%, 60%, 70%, and 80% oxygen, with all packs containing 20% CO₂ and the make up gas N₂. Steaks were stored at 4 °C for 12 days and tested for lipid and protein oxidation, heme iron, colour, oxymyoglobin concentration, Warner–Bratzler shear force (WBSF) and consumer acceptability for the resulting cooked meat. The results from 134 consumers indicated a directional preference for the steaks stored in packs containing 40% and 80% oxygen. Samples with high oxygen levels, particularly the O₂60 and O₂70 treatments, were positively and significantly (P < 0.01) correlated to sensory toughness, and significantly (P < 0.05) negatively correlated to juiciness, as determined by consumers. However, the O₂40 samples were most negatively (P < 0.001) correlated to toughness and positively (P < 0.01) correlated to juiciness, which shows that, in general, these higher O₂ levels, >40%, imparted greater meat toughness as determined by the consumers. The greater directional acceptance of the O₂40 samples may be linked to the consumer perceived reduction in sensory toughness and increases in juiciness.     

Biochemical and thermal characterization of crude exo-polygalacturonase produced by Aspergillus sojae

Crude exo-polygalacturonase enzyme (produced by Aspergillus sojae), significant for industrial processes, was characterized with respect to its biochemical and thermal properties. The optimum pH and temperature for maximum crude exo-polygalacturonase activity were pH 5 and 55 °C, respectively. It retained 60–70% of its activity over a broad pH range and 80% of its initial activity at 65 °C for 1 h. The thermal stability study indicated an inactivation energy of E_d = 152 kJ mol⁻¹. The half lives at 75 and 85 °C were estimated as 3.6 and 1.02 h, respectively. Thermodynamic parameters, ΔH^*, ΔS^* and ΔG^*, were determined as a function of temperature. The kinetic constants K_m and V_max, using polygalacturonic acid as substrate, were determined as 0.424 g l⁻¹ and 80 μmol min⁻¹, respectively. SDS-PAGE profiling revealed three major bands with molecular weights of 36, 53 and 68 kDa. This enzyme can be considered as a potential candidate in various applications of waste treatment, in food, paper and textile industries.