Evaluation of Beef Palatability Following Extended Storage at Low Temperature

Extending the shelf life of fresh meat without having an adverse effect on its quality attributes is critical to the meat industry to reduce waste, stabilize supply, and facilitate export. Low temperature (LT) storage of beef muscles at or slightly above their freezing point slows down microbiological spoilage while maintaining the product’s fresh status.This study evaluated the impact of 60, 75, or 90 d of LT storage (−2.7°C±0.3°C) on the palatability characteristics of steaks from inside rounds (IR), bone-in ribeyes, and striploins (SL) from 10 (n=10) upper two-thirds Choice beef carcasses. Two steaks fabricated from each subprimal were vacuum-packaged, wet-aged for 21 d (3°C), and frozen (−20°C) for Warner-Bratzler shear force (WBSF) and sensory analyses. These steaks served as the control with regard to storage condition and time. The remainder of each subprimal was fabricated into 3 portions, vacuum packaged, and randomly allocated to an LT storage time (60, 75, or 90 d). After each storage time, subprimals were fabricated into steaks, vacuum-packaged, and stored (−20°C) for WBSF and consumer sensory analyses. Consumers (N=238) evaluated cooked samples for juiciness, tenderness, flavor liking, and overall liking. Data were analyzed using a mixed model with storage time as the fixed effect and individual carcasses as the random blocking factor. The WBSF values decreased (P<0.05) with increased storage time for all the cuts. Similarly, consumer tenderness rating scores increased with the LT storage time, particularly in IR and SL steaks. However, storage time did not influence (P≥0.05) the juiciness, flavor, and overall liking of any of the cuts.The results of this study suggest it would be feasible to extend the storage time of beef while preserving or improving the sensory quality when held at optimal conditions above the freezing temperature

Housekeeping Proteins in Meat Quality Research: Are They Reliable Markers for Internal Controls in Western Blot? A Mini Review

Advancements in technology and analytical methods enable researchers to explore the biochemical events that cause variation in meat quality. Among those, western blot techniques have been successfully used in identifying and quantifying the key proteins that have critical functions in the development of meat quality. Housekeeping proteins, like β-actin, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and tubulins are often used as internal controls in western blots to normalize the abundance of the protein of interest. However, there are increasing concerns about using housekeeping proteins for western blot normalization, as these proteins do not demonstrate any loading differences above the relatively small total protein loading amounts of 10μg. In addition, the interaction between these housekeeping proteins and programmed cell death processes highlights the concerns about using the housekeeping protein as the internal control in meat quality research. Moreover, recent proteomic research has indicated that the abundance of some housekeeping proteins, like β-actin, GAPDH, and tubulin, can be altered by preslaughter stress, dietary supplementation, sex, slaughter method, genotype, breed, aging period, muscle type, and muscle portion. Furthermore, these housekeeping proteins could have differential expression in meat with differing color stability, tenderness, and water holding capacity. Therefore, this review aims to examine the realities of using housekeeping proteins as the loading control in meat quality research and introduce some alternative methods that can be used for western blot normalization

Differences in Spoilage Microflora Growth Kinetics Could Be Contributing to Beef Muscle-Specific Color Stability

The role of microbial communities on beef color stability during retail display is not fully understood. Therefore, this study aimed to characterize the physiochemical properties and microbial communities of color-stable (longissimus lumborum [LL]) and color-labile (psoas major PM]) beef muscles during aerobic retail display. Paired USDA Select beef LL and PM (n=5) were collected and aged (at 2°C) for 14 d. These were fabricated into 2.54-cm-thick steaks, packaged aerobically, and subjected to 7 d of retail display. Samples were evaluated daily for visual and instrumental color, percent-age discoloration, water activity, pH, metmyoglobin reducing activity (MRA), and bacterial population levels using conventional culture-based methodologies. Additionally, 16S ribosomal RNA (rRNA) amplicon sequencing was performed to characterize microbial communities associated with the LL and PM steaks throughout storage. The percentage discoloration was greater (P<0.05) in PM than LL after 2 d of retail display. Color stability, measured by MRA, was lower (P<0.05) for PM compared with LL each day. Culture-based microbiological analysis revealed that bacterial populations of PM steaks either exhibited no lag phase or had a shorter lag phase than the populations on LL samples. By the end of the retail display, bacterial levels on PM steaks were 1.3 to 1.6 log CFU/cm2 higher (P<0.05) than those recovered from LL samples. The 16S rRNA gene sequencing showed no differences (P≥0.05) in the alpha or beta diversities for the microbial communities of PM and LL on the same display day. The results confirmed that PM steaks had less color stability and a faster increase in bacterial numbers compared with LL during display. These results suggest that when initial bacterial communities are similar, the differential growth kinetics of bacteria present on these 2 muscles could contribute to the difference in their color stabilities

Effect of Extended Postmortem Aging on Beef Muscles of Differing Quality Grade during Retail Display

Aging of beef subprimals is a common industry practice to improve tenderness. However, the effect of extended aging (up to 63 d) on retail shelf life, tenderness, and eating quality of beef strip loin and sirloin of differing quality grades is not clearly understood. Therefore, in the current study, longissimus dorsi (strip loin) and gluteus medius muscles (sirloin) were collected from USDA Choice or Select carcasses and fabricated into 6 portions. Each of these portions was designated to an assigned time of wet aging (14, 21, 28, 35, 45, or 63 d) in vacuum bags. After aging, samples were fabricated into steaks and placed into a multideck retail display case for 72 h. Steaks were evaluated for color (instrumental and color panelists) every 8 h during retail display, and Warner-Bratzler shear force and sensory analysis were conducted after retail display. The results were analyzed using the PROC MIXED procedure of SAS with repeated measures for the color data. Among the effects evaluated (aging, quality grade, and aging×quality grade), quality grade was not significant (P>0.05) for either strip loin or sirloin steaks. An aging×display hour interaction was identified (P<0.05) for the color measurements. In general, as aging time increased over the display period, color was negatively impacted. Although tenderness improved (P<0.05) with aging, the incidence of off-flavors also increased, especially in sirloin steaks, suggesting that beef processors need to consider flavor changes during extended aging

Investigating the Etiology of Sour Knuckles in Postchilled Beef Carcasses

Development of sourness in beef round muscle cuts, such as knuckles, has been a long-standing issue in the beef industry with little characterization. Therefore, the objective of this study was to investigate and characterize the sour odor associated with beef knuckles using sensory, analytical (gas chromatography-mass spectrometry [GC-MS]), and microbiological approaches. Knuckles (n = 10) with no sour odor (control), a slight sour odor, or severe sour odor were collected during fabrication from a commercial beef processing plant. In addition, the synovial fluid from the femur joint, and the femur surface associated with the collected knuckles, were sponge-sampled. Knuckles were separated into 2 halves, with one half subjected to an odor panel, GC-MS, and microbial analyses on the day of collection (day 0). The remaining half was analyzed for odor and microbial populations following 35 d of vacuum-packaged storage at 0°C ± 2°C (day 35). Odor panelists identified differences (P < 0.05) between control and sour knuckles (slight sour odor and severe sour odor) for all attributes tested (off-odor, oxidation, putrid, and sour notes) regardless of storage day. GC-MS analysis found no statistical difference (P > 0.05) in volatiles between control and severe-sour-odor samples. Microbial analysis (aerobic plate counts and lactic acid bacteria counts) of muscle tissue on day 0 and day 35 of storage revealed no (P > 0.05) differences between the 3 treatment groups. Similarly, no (P > 0.05) differences between the treatment groups were obtained following analysis of synovial fluid and femur surface sponge samples for psychrotrophic anaerobic sporeformer counts. The findings of the study indicated that the souring condition in knuckles exists at identifiable intensities with no volatile acid or microbial population differences; therefore, further investigation is needed to determine the etiology

The Impact of Carcass Size, Chilling Conditions, and Electrical Stimulation on Beef Postmortem Temperature and pH Decline

Variability in carcass size can influence carcass chilling rates, which could result in issues associated with beef tenderness and color. Moreover, the usage of electrical stimulation can affect postmortem metabolism and meat quality. However, few studies have looked at the combined impact of chilling and electrical stimulation on temperature decline, postmortem biochemistry, and color among the current population of US beef. Beef carcasses (N = 162, < 30 mo) were randomly selected from 2 beef processing plants. One side of each carcass was electrically stimulated, while the opposing side was not electrically stimulated. Matched sides were subjected to either conventional spray chilling (CONV) or delayed spray chilling (DELAY). Deep tissue (10.5 cm under the pelvic bone) and surface temperature (1.5 cm under the loin fat) were continuously monitored during chilling in addition to temperature and pH measurements from the semimembranosus (SM), longissimus lumborum (LL), and psoas major (PM) muscles at an initial time (45 to 60 min), 6 h, 12 h, and after chilling (28 to 36 h) postmortem. Further, the instrumental (L*, a*, and b*) and visual color were evaluated on 14-d aged PM steaks. For data analysis, carcasses with hot carcass weights above or below the plant average were considered heavy or light, respectively. A nonlinear regression model was fitted to the continuous deep and surface temperatures, whereas other parameters were evaluated using a mixed model. Electrical stimulation improved L* (lightness; P < 0.05) of PM in light- weight carcasses but not (P > 0.05) in heavyweight carcasses. Temperature decline was faster (P < 0.05) and pH decline slower (P < 0.05) in the SM and LL of lightweight carcasses under CONV compared to lightweight carcasses under DELAY and heavyweight carcasses under CONV and DELAY. Exponential decay models for deep and surface temperatures indicated the rate of cooling differed (P < 0.05) due to the combination of treatment factors. Heavyweight carcasses in DELAY had slower rates of temperature decline (P < 0.05). Overall, the variability in carcass size affected temperature decline and postmortem metabolism. Therefore, postmortem management practices should consider carcass weights to optimize meat quality

Economic Loss, Amount of Beef Discarded, Natural Resources Wastage, and Environmental Impact Due to Beef Discoloration

Any deviation from a bright-red color leads to a discounted price or beef is discarded. Limited data are currently available on the economic losses due to retail beef discoloration. Therefore, the objective of the study was to estimate economic losses, the amount of beef discarded, natural resource wastage, and environmental impact due to beef discoloration. One-year data of total beef sales, total beef discarded, and discounted sale values were collected from 2 national retail chains and 1 regional retail chain located in the Southern United States, representing data from 5,034 stores and 44 states. The US beef system life cycle parameters from published literature were used to calculate the impact of discarded meat on water and energy use and greenhouse gas emissions. The study noted that approximately 2.55% of beef is discarded because of discoloration. The results indicate that the US beef industry loses $3.73 billion annually owing to discoloration. The total amount of beef discarded per year in the US corresponds to 194.70 million kg, which represents wasting 780,000 animals and the associated natural resources used in their production. A 1% decrease in discolored beef in the US could reduce natural resource waste and environmental impact by 23.95 billion L of water, 96.88 billion MJ of energy consumed, and 0.40 million tons of carbon dioxide equivalent emission along the beef upstream value chain. Therefore, improving the color stability of meat could increase the sustainability of beef production and limit the waste of nutritious beef, so the application of novel technologies to mitigate color deterioration should be imperative

Prediction of Tenderness, Juiciness, and Flavor Profile of 2 Beef Muscles with Different Aging Times Using Rapid Evaporative Ionization Mass Spectrometry (REIMS)

Rapid evaporative ionization mass spectrometry (REIMS) is a novel technique that provides rapid chemical information on biological tissues and has the potential to predict beef quality attributes in real time. This study aims to assess the ability of analysis by REIMS coupled with chemometric modeling to predict the quality attributes of wet-aged beef at the grading time. USDA Select and upper two-thirds Choice (n=42, N=84) striploins (longissimus lumborum [LL]) and tenderloins (psoas major [PM]) were collected 36 h postmortem from a commercial beef abattoir. The LL and PM were cut into portions and aged for 3, 14, and 28 d. Aged samples were analyzed for slice shear force,Warner-Bratzler shear force (WBS), and trained sensory panels (tenderness, juiciness, and flavor attributes), and results were used to categorize both LL and PM into binary classes. Additionally, slivers of the longissimus dorsi muscle between the 12th and 13th rib were collected during grading (36 h postmortem) and analyzed using REIMS. The REIMS data were used to build predictive models for tenderness, juiciness, and flavor classes for the 3 aging periods and 2 muscles. Prediction accuracies of all models were higher than classifying the samples by chance (P<0.05), except WBS of 3 d aging model (P>0.05). However, model accuracies were not too high, which could be due to overlaps between classes, small sample sizes, and unbalanced data, which could negatively affect predictive models. Results demonstrated that the chemical finger-prints obtained with REIMS could potentially sort carcasses by flavor, juiciness, and tenderness in real time. However, the full realization of this approach will require an increased sample size and the development of a sampling method that allows improved separation between sensory classes

Variations in Low Electrical Stimulator Voltage Settings Minimally Influence Beef Longissimus Muscle Slice Shear Force Values

The objective of the current study was to evaluate the effect of differing electrical stimulation (ES) voltage levels on beef longissimus muscle tenderness, postmortem temperature, pH decline, and carcass quality. Beef carcasses from 3 commercial beef processing plants (A, B, C) were exposed to 3 varying voltage levels: (1) control (no ES), (2) ES level 1 (ES1; 60 Hz for 17 s each at 16, 20, 24, and 28 V), and (3) ES level 2 (ES2; 60 Hz for 17 s each at 25, 35, 45, and 55 V) prior to chilling. Ninety beef carcasses were selected from each of the 3 plants, and within a carcass, paired sides were randomly assigned to one of 3 ES treatments (n = 60 sides/treatment/plant). The results indicated that ES affected (P < 0.05) muscle pH at 3 h postmortem in 2 of the 3 plants. However, ES did not affect (P > 0.05) pH at the time of grading (postrigor). Although the slice shear force (SSF) values were lower (P < 0.05) for ES steaks compared with controls, voltage did not affect (P > 0.05) SSF values. Variation in SSF was observed among the plants (P < 0.05), with steaks from Plant C having greater (P < 0.05) SSF values compared with steaks from Plants A and B, which exhibited similar (P > 0.05) SSF values. Overall, although ES steaks had lower SSF values compared with control steaks, the lack of difference in postmortem tenderness between ES1 and ES2 voltage settings indicated that the low ES voltages minimally influenced SSF values

Recent Updates in Meat Color Research: Integrating Traditional and High-Throughput Approaches

Deviation from a bright cherry-red color of fresh meat results in less consumer acceptance and either discounted or discarded products in the value chain. Tissue homeostasis changes immediately after exsanguination, leading to acidification of muscle. Any alteration in pH drop can influence both muscle structure and enzymatic activity related to oxygen consumption and the redox state of myoglobin. This review focuses on both fundamental and applied approaches to under-stand the effects of pH on biochemical changes, oxygen diffusion, and its impact on meat color. Recent updates utilizing high-throughput “omics” approaches to elucidate the biochemical changes associated with high-pH meat are also dis-cussed. The fundamental aspects affecting fresh meat color are complex and highly interrelated with factors ranging from live animal production to preharvest environmental issues, muscle to meat conversion, and numerous facets along the merchandising chain of marketing meat to consumers