DFD Beef Research Articles

Role of Heat-Shock Proteins in the Determination of Postmortem Metabolism and Meat Quality Development of DFD Meat.

This research explored the potential role of various heat-shock proteins (HSPs) in the determination of postmortem metabolism and the development of meat quality of normal, atypical DFD, and typical DFD beef. Beef longissimus thoracis muscle samples were classified into normal, atypical DFD, and typical DFD beef. The HSP27, HSP70, and HSP90 levels, meat quality parameters, and glycolytic metabolites were tested. The results showed that color coordinates (L*, a*, and b*), glycogen, and lactate contents were lower, whereas water-holding capacity was higher in the typical DFD beef than in the normal and atypical DFD beef (p < 0.05). The expression of HSP27 on day 1 was higher in atypical DFD beef. However, expressions of HSP70 on days 1 and 3 were higher in typical DFD, while the expression of HSP90 on day 1 was higher in atypical and typical DFD compared to the normal beef (p < 0.05). Interestingly, the expression of HSP27 was positively correlated with shear force readings. HSP70 and HSP90 presented a direct correlation with pH and water-holding capacity and an indirect correlation with a* and b*, glycogen and lactate contents (p < 0.05). The study concluded that the heat-shock proteins could influence the formation of DFD beef possibly by regulating the development of postmortem metabolism and meat quality traits.

Exploring the miRNAs Profile in Dark-Cutting Beef.

In an animal production system, different stressors may cause the depletion of muscle glycogen stores, resulting in an elevated pH at 24 h post mortem (pH24), which leads to cell metabolism alterations that affect the conversion of muscle into meat, causing meat quality defects, such as dark-cutting beef, also known as dark, firm, and dry (DFD) beef. This process may involve the alteration of small non-coding RNAs (miRNAs), which play critical regulatory roles in cellular processes. Here, we determined whether differential miRNA expression in the Longissimus thoracis et lumborum muscle from the Asturiana de los Valles breed at 24 h post mortem could serve as an early indicator of beef quality defects. Following total RNA extraction, complete miRNAome sequencing revealed 12 miRNAs that were significantly upregulated (p < 0.001) in DFD beef compared to the levels in CONTROL beef. These miRNAs are mainly involved in the cellular responses to redox imbalances and apoptosis. Among these, four miRNAs known to be related to oxidative stress (bta-miR-1246, bta-miR-2332, bta-miR-23b-5p, and bta-miR-2411-3p) were validated via quantitative RT-PCR. Some of their target proteins were also analyzed using Western blotting. High 70 kDa heat shock protein and low Caspase-9 expressions (p < 0.01) were found in DFD beef, suggesting the downregulation of apoptosis. These results suggest the importance of miRNAs in regulating stress in muscle cells during early post mortem, as differences in the abundance of some of these miRNAs are still observed at 24 h post mortem. These changes lead to an inadequate conversion of muscle into meat, resulting in meats with quality defects.

Behaviour of Escherichia coli O157:H7 and Listeria monocytogenes in Normal and DFD Beef of an Autochthonous Portuguese Breed

This study was carried out to identify the behaviour of Escherichia coli O157:H7 and of Listeria monocytogenes inoculated in Maronesa breed beef with different ultimate pH (pHu) (Normal and DFD), and stored at two different temperatures (4 and 9 °C), during 28 days post mortem (pm). The main objective was to illustrate the problematic feature of dealing with beef showing high pHu and stored at mild abusive temperatures (9 °C). Beef steaks (ms. longissimus dorsi) were inoculated with low levels (2-3 log CFU/g) of those both pathogens and packed in air, vacuum and three gaseous mixtures with decreasing O2 and increasing CO2 concentrations (MAP70/20, MAP50/40 and MAP30/60). At 4 °C, the growth of E. coli O157:H7 presented the same pattern on Normal and DFD meat. On the contrary, the growth of L. monocytogenes was higher in DFD meat, revealing the effect of the pHu and its psychotropic character. At abusive temperatures, both pathogens grew, achieving high levels in DFD meat. In these cases, the MAP with the highest CO2 concentration (60%) was revealed to be more effective against the development of E. coli O157:H7, therefore, not exceeding levels of 5 log CFU/g at the end of storage, while in L. monocytogenes, it reaches 8 log CFU/g under the same conditions.

High-pressure processing and modified atmosphere packaging combinations for the improvement of dark, firm, and dry beef quality and shelf-life

This study investigated the effects of high-pressure processing (HPP) and modified atmosphere packaging (MAP) on ‘dark, firm, and dry’ (DFD) beef. To optimize the HPP, beef steaks (n = 180) were first processed at different pressures (0.1, 200, 300, 400, 500 MPa). It was found that 400 MPa enhanced DFD beef color and shelf-life. This optimized HPP (400 MPa) was combined with 3 MAP formulations, in a second study (40, 60, or 80% O2-MAP), to determine their effect on DFD beef steaks. HPP (400 MPa) combined with MAP improved DFD beef L* and a*, color scores, and delayed discoloration (P < 0.01). Total plate counts for DFD beef held under 60% O2-MAP was ≤6 log10 CFU/g, even after 14 d of chilled storage. These same samples had shear force and TBARS values significantly lower than observed for DFD beef held under 80% O2-MAP. HPP (400 MPa) combined with 60% O2-MAP is recommended to improve DFD beef quality and shelf-life.

Changes in postmortem metabolites profile of atypical and typical DFD beef

This study explored the changes in postmortem metabolites of atypical and typical DFD beef using UHPLC-Q-TOF/MS. The longissimus thoracis muscles were categorized into normal, atypical DFD and typical DFD groups. The L⁎, a⁎, b⁎, glycogen and lactic acid contents were lower (P < 0.05) in typical DFD than normal beef. A total of 240 compounds were significantly different among groups. Levels of glycerol-3-phosphate, d-ribose-5-phosphate, d-glucose-6-phosphate, d-fructose-6-phosphate, alpha-d-glucose-1-phosphate and dihydroxyacetone phosphate were higher in atypical DFD than those in the normal and typical DFD beef and the contents of 9 amino acids were elevated in typical DFD. KEGG analysis showed that metabolomic changes were primarily related with ATP-binding cassette transporters, metabolism of purine, central carbon, glycine, serine and threonine, biosynthesis of aminoacyl-tRNA, digestion and absorption of proteins, metabolism of amino sugar and nucleotide sugar, pyrimidine, bile secretion and galactose. In conclusion, development of atypical and typical DFD meat results in differences at level of postmortem metabolite concentrations of different metabolic pathways.

Assessment of caspase activity in post mortem muscle as a way to explain characteristics of DFD beef

Pre-slaughter stress can lead to ‘dark cutting’ defective meat characterized by a high ultimate pH (pHu) in cattle, causing high economical losses in the meat industry. Therefore, the study of biochemical mechanisms related to animal stress response is a fact that needs to be addressed. The aim of this work was to determine caspase 9 and 3/7 activities in high and normal pHu muscle samples at 24 h post mortem as a way to reveal stress situations in different Spanish local breeds (Asturiana de los Valles, Retinta and Rubia Gallega) and crossbred animals (n = 83). Either breed or pHu factors had an effect in both caspase activities, showing the high pHu group the highest caspase activity independently of the studied breed. In contrast, activity levels among breeds were slightly different for each caspase and between the high and normal pHu group in the case of caspase 3/7. Overall, this study demonstrated that caspase activity can be a good indicator to detect stress situations that might lead to defective high pHu meats.

Sarcoplasmic and myofibrillar phosphoproteins profile of beef M. longissimus thoracis with different pHu at different days postmortem

The abnormal ultimate pH (pHu ) in postmortem muscles affect the meat quality and results in substantial economic losses. Dark, firm, and dry (DFD) meat linked with the higher postmortem pHu values and exhibited many quality issues such as dark color, tough texture and shorter shelf life. This research aimed to investigate the effect of protein phosphorylation on variations in beef pHu in order to explore the possible mechanisms underlying DFD meat formation. Glycogen and lactate contents were higher, while L* and a* were lower in high pHu beef. Shear force was higher in intermediate pHu group. Global phosphorylation of sarcoplasmic proteins was higher in low pHu samples on day 1 and of myofibrillar proteins was higher in intermediate pHu meat on days 1 and 2 postmortem. Sarcoplasmic protein bands with different phosphorylation levels were identified as containing some glycometabolism and stress response proteins and phosphorylated myofibrillar protein bands were identified sarcomeric and metabolic proteins. Phosphorylation of multiple proteins of glycolytic pathway and contractile machinery may play critical roles in development of DFD beef. © 2021 Society of Chemical Industry.

Thermal conductivity factor for beef of NOR and DFD grades at the subcryoscopic temperatures

Thermal conductivity factor and specific isobaric heat capacity of food products are currently the most important parameters in the development of mathematical models for food freezing and thawing and in improving production technology. There is significant variance among the existing experimental data for the thermal conductivity factor in meat. Most of the modern calculated relationships are based on the nutritional approach, which favorably differs by the ability to calculate the thermophysical characteristics of any food products. However, the calculation error at the subcryoscopic temperatures may be 15% to 20%. The development of superchilling as a way of storing meat requires high accuracy of freezing time calculation, including vacuumpacked boneless meat. In the presented article, the authors investigated hydrogen index, cryoscopic temperature, frozen moisture proportion and thermal conductivity factor for beef M. longissimus dorsi samples of NOR and DFD grades. It was found that DFD beef is characterized by 10% to 12% higher values of thermal conductivity factor in comparison with NOR grade. Using the method of regression analysis, the authors developed empirical relationships for calculating the thermal conductivity factor of meat depending on its temperature and pH level. Unlike cryoscopic temperature and frozen moisture proportion, pH is easy to measure and may be easily used on a conveyor belt for more accurate assessment of meat thermophysical properties. With an increase in pH from 5.3 to 7, an increase in cryoscopic temperature is observed from minus 0.94 °C to minus 0.72 °C. It has been shown that one of the factors for the higher cryoscopic temperature and higher pH level of DFD beef is higher water-holding capacity with less strongly bound moisture.

Association between meat color of DFD beef and other quality attributes

This study investigated the association between DFD beef color and other quality traits and explained the possible mechanisms. Beef longissimus thoracis (LT) was assessed and classified into one of three groups based on the pH 24 h post-mortem: normal (pH ≤ 5.70), atypical DFD (5.70 < pH ≤ 6.09) and typical DFD (pH > 6.09) beef and stored at 4 °C for 7 days. Typical DFD beef showed the lowest glycolytic potential, L*, a*, b*, chroma and oxymyoglobin accompanied with the highest water-holding capacity, hue angle and deoxymyoglobin values on day 1 of storage. Glycolytic potential was positively correlated with chroma, R630/580 and oxymyoglobin but was negatively correlated with pH and hue angle. Water-holding capacity was directly related to deoxymyoglobin levels. Atypical DFD beef showed a higher shear force value that was positively associated with metmyoglobin levels. In conclusion, DFD beef color was not only affected by ultimate pH but also related to shear force, glycolytic potential and water-holding capacity.

Comparative quality assessment of nor, pse and dfd beef

Comparative quality assessment of meat with NOR, PSE and DFD attributes was given in the paper. Application of NOR, PSE and DFD beef indicators in the industry was substantiated. The basic causes of attributes with the specific autolysis development were analyzed and it was found that these are age peculiarities, improper preparation of animals for slaughter and violation of their feeding and keeping. As a result, meat with deviated development of autolytic processes, including the emergence of NOR, PSE and DFD attributes may be observed. For this purpose, organoleptic quality assessment of the NOR, PSE and DFD meat in different age periods was conducted. It was found that the pigmentation in beef has directly proportional dependence on the age and sex of slaughtered animals and the meat color. The pigmentation in DFD meat was higher compared to NOR meat from bulls aged 18-24 months - by 85.9% (p<0.001); bulls aged 24-36 months - by 86.8% (p<0.001); cows - by 74.8% (p<0.001). Least pigments are contained in PSE beef: from bulls aged 18-24 months - 1.88 mg/cm 3 , bulls aged 24-36 months - 2.09, cows - 2.71 mg/cm 3 , so pale pink color is typical for such meat.

Carne de vacuno normal vs. DFD: valoración por un panel de consumidores y comparación mediante pH y color

Normal vs. DFD beef: evaluation by a consumer panel and comparison by pH and color The aim of this report was to evaluate normal and DFD beef by a consumer panel, as well as to compare both types of meat through their pH, colour parameters (L*, a*, b*, C* y ho) and reflectance spectra (400-700 nm). All parameters were measured at 8 days of ageing. Besides, 64 consumers evaluated acceptability of tenderness, juiciness, flavor and overall acceptability for the two types of meat. Colour variables supported that DFD meat colour is darker, browner and more saturated (P < 0,001) than normal meat. In the reflectance spectra the more significant differences (P <0.001) between the two types of meat appeared from 500 nm. Significant differences between both types of meat were observed for acceptability of tenderness (P < 0.001), juiciness and overall acceptability (P < 0.01). Therefore, it could be said that consumers preferred the DFD meat than the normal one.

Application of a computer vision system to classify beef as normal or dark, firm, and dry1

The purpose of this research was to evaluate the possibility of using computer vision systems (CVS) to detect DFD beef. The experimental material consisted of beef obtained from 60 carcasses (M. semimembranosus) that were 48 h postmortem. The beef was classified into 2 quality groups according to pH: normal (pH < 5.8) or DFD (pH ≥ 5.8). L*, a*, and b* color components were determined in the experimental materials using both CIELab and a CVS using 3 color models: RGB (red, green, blue), HSV (hue, saturation, value), and HSL (hue, saturation, lightness). The total heme pigment content also was determined. As determined by both CIELab and CVS, DFD meat was characterized by a darker color than normal beef. Color lightness, as determined using both CIELab and CVS, can also be used to detect DFD beef. A significant relationship was found between V (r = -0.79) and L (r = -0.77) using CVS and pH, which is an indicator of DFD beef. This finding indicates the possibility of using these color components to assess the pH level of beef.

Relationships among glycolytic potential, dark cutting (dark, firm, and dry) beef, and cooked beef palatability.

One hundred beef carcasses were selected at three packing plants and were used to determine the relationship between glycolytic potential (GP) and dark, firm, and dry (DFD) beef and to determine the effects of DFD status and GP on cooked beef palatability. Eight individual muscles were excised from one hindquarter of each carcass at d 7 postmortem: longissimus lumborum, psoas major, gluteus medius, tensor fasciae latae, rectus femoris, semimembranosus, biceps femoris, and semitendinosus. Ultimate pH, colorimeter readings, and Warner-Bratzler shear force were determined for all eight muscles at d 7 postmortem. A nine-member trained sensory panel evaluated cooked longissimus lumborum, gluteus medius, and semimembranosus steaks. Traits determined solely for the longissimus lumborum were GP (2 x [glycogen + glucose + glucose-6-phosphate] + lactate) and ether-extractable fat. A curvilinear relationship existed between GP and ultimate pH within the longissimus muscle. There appeared to be a GP threshold at approximately 100 micromol/g, below which lower GP was associated with higher ultimate pH and above which GP had no effect on ultimate pH. The greatest pH and muscle color differences between normal and DFD carcasses were observed in the longissimus lumborum, gluteus medius, semimembranosus, and semitendinosus muscles. Cooked longissimus from DFD carcasses had higher shear force values (46% greater) and more shear force variation (2.3 times greater variation) than those from normal carcasses. Dark cutting carcasses also had higher shear force values for gluteus medius (33% greater) and semimembranosus (36% greater) than normal carcasses. Sensory panel tenderness of longissimus, gluteus medius, and semimembranosus was lower for DFD carcasses than for normal carcasses. Longissimus and gluteus medius flavor desirability scores were lower for DFD than for normal carcasses. Steaks from DFD carcasses had more off-flavor comments than steaks from normal carcasses, specifically more "peanutty," "sour," and "bitter" flavors. The DFD effect of higher shear force values was approximately five times greater (+3.11 kg vs +0.63 kg) for carcasses with "slight" marbling scores than for carcasses with "small" marbling scores. In general, higher GP was associated with increased tenderness, even among normal carcasses. In conclusion, low GP was associated with DFD beef and resulted in substantially less-palatable cooked steaks.

Growth of Escherichia coli O157:H7, Salmonella Typhimurium DT104, and Listeria monocytogenes in Dark Cutting Beef at 10 or 22° C

An experiment was conducted to determine the effects of the dark, firm, and dry (DFD) condition of beef on growth of the foodborne pathogens Escherichia coli O157:H7, Salmonella Typhimurium DT104, and Listeria monocytogenes Scott A in ground beef. Longissimus muscles from a DFD carcass (pH = 6.45) and normal carcass (N; pH = 5.64) were ground and samples obtained (100 and 0% DFD, respectively). Equal amounts of the 0 and 100% DFD ground samples were mixed to obtain 50% DFD samples. Inoculated 0, 50, and 100% DFD samples were packaged into oxygen-permeable overwrap and stored at 10°C for E. coli O157:H7, Salmonella Typhimurium DT104, and L. monocytogenes Scott A or at 22°C for E. coli O157:H7. Growth characteristics of E. coli O157:H7, Salmonella Typhimurium DT104, and L. monocytogenes Scott A did not differ (P > 0.05) between 0 and 100% DFD. Results indicated that the DFD beef used in this study was no more susceptible to growth of E. coli O157:H7, Salmonella Typhimurium, or L. monocytogenes Scott A than N beef.

Colour of normal and high pH beef heated to different temperatures as related to oxygenation

The effects of oxygenation and thermal treatment (internal temperature, T i: 45, 60, 75°C) on the colour and some colour related physical and biochemical properties of beef longissimus dorsi (LD) muscle, both normal (pH u∼5.6) and DFD (pH u>6.6), were studied. The colour components ( L ∗, a ∗, b ∗ values) for the raw and heated LD, both before and after oxygenation, were instrumentally and sensorily evaluated. The colour of raw and heated (60°C) DFD beef before and after oxygenation differed significantly from the normal meat and contained more native muscle pigment (TMP). pH also influenced the depth of the oxygenated layer, specific activity of cytochrome c oxidase (SACCO) and the amount of oxygen consumed. An increase in internal temperature was usually accompanied by a lower SACCO and a significant decrease of TMP, as well as a change of all colour parameters. Oxygenation of the raw and heated slices (except at 75°C) of both types of meat led to higher L ∗ , a ∗ and b ∗ values.

Dissimilarity scaling and INDSCAL analysis in the study of flavour differences between normal pHu and DFD beef

AbstractOverall dissimilarity measurement of paired stimuli followed by Individual Differences Scaling (INDSCAL) analysis was used to study flavour perception in a set of beef extracts. The experiment was designed to determine whether pH contributed to flavour difference between beef of “normal” ultimate pH (pHu5.8) and “dark‐cutting” (DFD) beef (pHu6.2). Assessors distinguished the flavour of “normal” pHu and DFD beef both by a combination of pH and titratable acidity, and a second dimension independent of pH. The chemicals added to adjust pH independently of the original muscle composition contributed a third flavour dimension. Substantial assessor variation was observed in the relative weight given to the three flavour dimensions, and this is discussed in relation to the task of judging overall dissimilarity.