Introduction
Consumer acceptance of fresh beef is strongly driven by lean color, with deviations from the expected bright-cherry red appearance deterring consumer purchasing intent (Altmann et al., 2023; Aboah et al., 2020; Feuz et al., 2020 Troy and Kerry 2010;). Dark-cutting beef, characterized by abnormally dark, purplish lean color, and represents a persistent challenge to the beef industry (Mayer et al., 2024; Steel et al., 2022; Loredo-Osti et al., 2018). This condition arises when muscle glycogen reserves are depleted prior to harvest, resulting in insufficient postmortem acidification and a higher-than-normal ultimate pH (Wulf et al., 2002). Elevated muscle pH reduces light scattering, increases water-holding capacity, and limits myoglobin oxygenation, collectively producing the dark appearance that is readily rejected by consumers (Ponnampalam et al., 2017). In turn, dark-cutting carcasses are frequently downgraded and diverted from fresh retail markets, leading to substantial economic losses across the beef supply chain (Harr et al., 2024; Yang et al., 2021).
The economic consequences of dark cutting carcasses are particularly pronounced in high-value primals, where visual appearance is critical to consumer acceptance (Ramanathan et al., 2022). Among these, the beef tenderloin (Psoas major) represents one of the most valuable cut on the carcass due to its exceptional tenderness and premium market positioning. However, when dark cutting defect affects this premium muscle, its value is disproportionately reduced, transforming an otherwise wholesome product into one that is difficult to market in fresh retail channels (Ramanathan et al., 2022). Despite the financial importance of the tenderloin, limited research has focused on strategies to restore the visual quality and marketability of this muscle from dark-cutting carcasses.
High-pressure processing (HPP) has emerged as a promising post-harvest intervention for modifying meat quality attributes without the application of heat (Reesman et al., 2023a). By subjecting products to intense hydrostatic pressures, HPP can alter muscle protein structure, pigment chemistry, and light-scattering properties, influencing color, texture, and microbial stability (Ma et al., 2007; Ueno et al., 1999; Carlez et al., 1995). Previous research has demonstrated that HPP can improve the color of dark-cutting beef, particularly in the Longissimus dorsi, a color-stable muscle. Application of 300 MPa to a strip steaks have shown to increase both lightness and redness (Reesman et al., 2023a). While effective, the majority of HPP research has focused on muscles with relatively high color stability (Mao et al., 2023; Reesman et al., 2023a ; Utama et al., 2016), leaving a critical gap in knowledge regarding the effectiveness in color-labile muscles.
Muscle-specific responses to postmortem interventions are well documented and are largely driven by differences in fiber type composition, connective tissue characteristics, and metabolic properties (Listrat et al., 2020; Picard and Gagaoua, 2020). The Psoas major contains a greater proportion of oxidative fibers, elevated mitochondrial density, and reduced glycogen reserves compared to its color-stable counterpart, all of which contribute to its susceptibility to discoloration and oxidative deterioration during retail display (Canto et al., 2016). Consequently, the response of this muscle to HPP cannot be assumed to reflect that of the previous outcomes observed in more color-stable muscles. Therefore, the objective of this study was to evaluate the effects of high-pressure processing on color and quality attributes of beef tenderloins from dark-cutting carcasses.
Materials and Methods
Sample Collection and Processing
Twelve beef tenderloins (Psoas major) from selected from USDA deemed dark-cutting carcasses (Dark-cutting, mean pH = 5.8 ± 0.08) and 6 beef tenderloins from USDA Choice carcasses (Normal, mean pH = 5.4 ± 0.08) were collected approximately 48 to 72 h postmortem from a commercial beef packing facility. Tenderloins were transported on ice to the Loeffel Meat Laboratory (Lincoln, NE) and stored at 2°C for 5 days. Each tenderloin served as a block. After aging, pH of tenderloins was measured using a calibrated portable pH probe (type) and tenderloins were faced and tail portion removed, leaving the uniformed center cut portion to be fabricated into two ∼10 cm sections and vacuum packaged.
From each dark-cutting tenderloin, one center cut portion was randomly assigned to a 300MPa (n=6) or 450 MPa (n= 6) HPP treatment and 1 portion served as a non-HPP dark cutting control (n=12). Additionally, 1 portion from each normal-pH tenderloin did not receive HPP treatment and served as reference standard control (Normal pH Non-HPP Control, n=6) while the remaining portion was discarded from project. All portions were transported on ice to the Food Processing Center (Lincoln, NE) for HPP treatment.
High-Pressure Processing
High-pressure processing was performed using a Hiperbaric unit (Hiperbaric 55; Hiperbaric USA, Miami, FL; 55-L vessel; 200-mm diameter; 270 kg/h throughput; 300 MPa/min pressurization rate). Pressurization treatments were conducted in duplicate by dividing each treatment group into two batches. Water maintained at 4–8 °C was used as the pressurizing medium, and product bins were filled with ice to minimize temperature fluctuations during processing. Following HPP, tenderloin sections were transported back to the Loeffel Meat Laboratory on ice and placed in refrigerated (2°C) storage for 48 h to simulate shipping time (d 0).
Retail Display
Following the HPP treatment and 48 h of refrigerated storage at 2 °C, tenderloin portions were fabricated from anterior to posterior direction with the first two steaks being sliced into 2, 2.4-cm thick steaks while the more posterior steaks were sliced into4, 1.2-cm thick steaks for subsequent analyses. From each center cut portion, steaks were placed on a polystyrene tray, overwrapped with polyvinyl chloride film (Prime Source PSM 18 #75003815, Bunzl Processors Division, North Kansas City, MO; oxygen transmission rate = 2.25 mL/cm2/24 h), and displayed under simulated retail conditions (white fluorescent lighting at 1,612.5–2,152 lux; 1–2 °C) in accordance with King et al. (2023). One 2.4 cm thick steak served as 1 d steak for WBSF, while the other served as the instrumental and visual sample for entirety of retail display as well as 7 d WBSF sample. The remaining 4, 1.2 cm steaks served as d 0, 3 and d 7 samples for TBARS and pH, Regardless of the d, all steaks were and steaks were rotated randomly each day throughout the retail display period.
Instrumental and Visual Color
Instrumental color measurements were obtained daily using a Minolta CR-400 colorimeter (D65 illuminant, 8-mm aperture, 2° observer angle; Minolta, Osaka, Japan). CIE L*, a*, and b* color values were collected in triplicate with means calculated on overwrapped steaks. The instrument was calibrated daily using a white ceramic tile covered with overwrap film. Pre-HPP and 0 d color were taken following a 30 m bloom time. For all other days of instrumental color samples were in oxygen permeable film and required no additional bloom time.
Visual color evaluations were conducted daily by six trained panelists from the University of Nebraska–Lincoln. Standardized color reference guides were used to evaluate percent surface discoloration, overall color score, and paleness score in accordance with King et al. (2023). All panelists were screened for normal color vision prior to participation. Training consisted of multiple calibration sessions using anchored reference samples representing the full range of the color scale. During these sessions, panelists independently evaluated samples and discussed scores to improve agreement and consistency. Training was conducted under standardized lighting and evaluation conditions consistent with AMSA recommendations. Rather than a fixed duration, training continued until panelists demonstrated acceptable repeatability and agreement with the reference standards, ensuring consistent and reliable color evaluations prior to data collection. Panelist evaluated steaks for surface discoloration, color, and paleness. Percent surface discoloration was assessed using a 6-point scale (1 = 0%; 6 = 81–100%). Color score was evaluated on an 8-point scale in 0.5-unit increments (1 = bleached red; 8 = very dark red). Paleness was assessed using a 6-point scale (1 = very dark; 6 = very pale) to evaluate color fading associated with HPP.
pH Analysis
Steaks were at 0, 3, and 7 d of retail display, diced, and frozen and stored in −80°C until time of pH analysis. Determination of pH was carried out as described by Ribeiro et al. (2021). Briefly, frozen samples were powered using a metal cup blender (Model 51BL32, Waring Commercial, Torrington, CT) and weighed in duplicates(5 g) and homogenized with 45 mL of Milli-Q water using a Polytron homogenizer (Kinematica CH-6010, Switzerland). Sample pH was measured in duplicate using a calibrated pH meter, and mean values were calculated. The pH meter was calibrated daily using standard buffers (pH 4.0, 7.0, and 10.0).
Thiobarbituric Acid Reactive Substances
Lipid oxidation was quantified using the thiobarbituric acid reactive substances (TBARS) assay following Buege and Aust (1978), with modifications by Ahn et al. (1998). Steaks from 0, 3, and 7 d of retail display were powdered, and 5-g duplicate samples were homogenized with 14 mL Milli-Q water and 1 mL butylated hydroxyanisole solution (10% BHA in ethanol). Homogenates were centrifuged at 2,000 × g for 5 min at 4 °C.
One milliliter of supernatant was combined with 2 mL of TCA–TBA solution (15% TCA; 20 mM TBA) and incubated in a 70 °C water bath for 30 min, followed by cooling for 15 min. Samples were centrifuged again (2,000 × g, 15 min, 4 °C), and 200 μL of supernatant was transferred to a 96-well plate. Absorbance was measured at 540 nm using a microplate spectrophotometer (Epoch, BioTek, Winooski, VT). Results were expressed as mg malonaldehyde/kg tissue using a standard curve generated from 1,1,3,3-tetraethoxypropane and the following equation:
Warner–Bratzler Shear Force
Warner–Bratzler shear force (WBSF) was evaluated using methods described by Riberio et al., (2021) with slight modifactions. Breifly, 2.54-cm steaks from 0 and 7 d of retail display were removed from the freezer (−20 °C) and thawed at 4 °C overnight. Steak internal temperatures and mass were recorded prior and after cooking. Temperature was recorded for each steak using an insulated T thermocouple (5SC-TTT-30-120, OMEGA Engineering, Inc., Stamford, CT) connected to a handheld thermometer (OMEGA 450-ATT, Engineering, Inc., Stamford, CT). The thermocouples were inserted into the geometric center of each steak. Steaks were cooked on a preheated electric griddle (Model 38546, Hamilton Beach Brands, Glen Allen, VA) set to 163 °C. Internal temperature was monitored using a T-type thermocouple connected to a digital thermometer (Omega Engineering, Stamford, CT). Steaks were flipped at 35 °C and removed at a final internal temperature of 71 °C.
Cooked steaks were placed on trays, covered, and held overnight at 2 °C. The following day, steaks were equilibrated to room temperature for at least 1 h before coring. At least four 1.27-cm-diameter cores were removed parallel to the muscle fiber orientation using a drill press. Cores were sheared using a Warner–Bratzler blade mounted on a texture analyzer (TMS-Pro, Food Technology Corp., Sterling, VA) at a crosshead speed of 200 mm/min with a 1,000-N load cell. Peak shear force was recorded in kilograms. The mean of all cores from a steak was used for statistical analysis.
Statistical Analysis
Data were analyzed using the GLIMMIX procedure of SAS 9.4 (SAS Institute Inc., Cary, NC). A randomized incomplete block design was used. For samples evaluated overtime, comparisons only considered main effects within day. Pressure used as the main effect and tenderloin included as a random effect. Means were considered significant at P ≤ 0.05. All data are expressed as least squares means ± SE.
Results
Color
High-pressure processing markedly altered both objective and subjective color attributes of tenderloin steaks throughout retail display. Pre-HPP instrumental color values were similar among all treatments prior to HPP application (P ≥ 0.3735; Figures 1A, 2A, and 3A), confirming that subsequent differences were attributable to processing effects rather than initial color variation.
Effect of HPP treatment (Normal pH Non-HPP Control (n=6), Dark-cutting Non-HPP Control (n=12), 300 MPa 90 s (n=6), 450 MPa 90 s (n=6)) within retail day on L* values of steaks. Data represent LS means ± SE. Means are considered significantly different at P < 0.05. Means lacking common letters differ.
Effect of HPP treatment (Normal pH Non-HPP Control (n=6), Dark-cutting Non-HPP Control (n=12), 300 MPa 90 s (n=6), 450 MPa 90 s (n=6)) within retail day on a* values of steaks. Data represent LS means ± SE. Means are considered significantly different at P < 0.05. Means lacking common letters differ.
Effect of HPP treatment(Normal pH Non-HPP Control (n=6), Dark-cutting Non-HPP Control (n=12), 300 MPa 90 s (n=6), 450 MPa 90 s (n=6)) within retail day on b* values of steaks. Data represent LS means ± SE. Means are considered significantly different at P < 0.05. Means lacking common letters differ.
Lightness (L*) was strongly influenced by HPP treatment across the entire retail display (P < 0.001; Figures 1B–I). Steaks subjected to 450 MPa consistently exhibited the greatest L* values, followed by the 300 MPa treatment, with both dark-cutting and normal-pH non-HPP controls remaining darker. This response was evident during the early display period (d 0–3; P < 0.0001; Figures 1B–E) and persisted through d 7 (P < 0.0001; Figures 1F–I), indicating that pressure-induced lightening was both immediate and sustained.
Redness (a*) exhibited a display-day–dependent response to HPP. A treatment effect was detected on all retail display days (P ≤ 0.0153), except d 1 and d 2 (P ≥ 0.068; Figures 2C and 2D). On d 0, steaks subjected to 450 MPa were had an increase in a* values (redness) than dark-cutting non-HPP controls (P < 0.05; Figure 2B). However, from d 3 through d 7, the 450 MPa treatment resulted in lower a* values compared with both non-HPP controls (P < 0.05; Figures 2E–I), suggesting accelerated loss of redness at higher pressures. The 300 MPa treatment generally produced intermediate a* values across the display period.
Yellowness (b*) was affected by HPP regardless of retail display day (P ≤ 0.013; Figures 3B–I). On d 0, dark-cutting-non-HPP control steaks exhibited lower b* values (yellowness) than steaks treated 450 MPa, with normal-pH-non-HPP and 300 MPA being intermediate (P = 0.0003; Figure 3B). From d 1 to d 3, 450 MPa steaks were more yellow than dark-cutting controls and, on d 1, normal-pH controls (P < 0.01; Figures 3C–E). During the remainder of the display, 450 MPa steaks maintained greater b* values than all other treatments (P < 0.01; Figures 3F–I).
Visual color traits were influenced by HPP treatment, including percent surface discoloration (P ≤ 0.0097; Figure 4), visual color score (P ≤ 0.001; Figure 5), and paleness score (P < 0.0001; Figure 6). Percent surface discoloration did not differ among treatments on d 0 (P = 0.2853; Figure 4A); however, 450 MPa steaks exhibited greater discoloration on d 1 and d 2 compared with other treatments (P < 0.0001; Figures 4B and 4C). From d 3 through d 7, both non-HPP control groups generally exhibited less discoloration than the 450 MPa treatment, with the lowest discoloration observed in dark-cutting non-HPP controls on d 3 (P < 0.01; Figures 3D–H). The 300 MPa treatment was similar to the 450 MPa steaks on d 4 and d 5.
Effect of HPP treatment (Normal pH Non-HPP Control (n=6), Dark-cutting Non-HPP Control (n=12), 300 MPa 90 s (n=6), 450 MPa 90 s (n=6)) within retail day on visual surface discoloration values of steaks. Data represent LS means ± SE. Means are considered significantly different at P < 0.05. Means lacking common letters differ. Surface discoloration: 1 = 0%, no discoloration, 2 = 1% to 20%, 3 = 21% to 40 %, 4 = 41% to 60 %, 5 = 61 % to 80 %, 6 = 81 % to 100 % discoloration.
Effect of HPP treatment (Normal pH Non-HPP Control (n=6), Dark-cutting Non-HPP Control (n=12), 300 MPa 90 s (n=6), 450 MPa 90 s (n=6)) within retail day on visual color score values of steaks. Data represent LS means ± SE. Means are considered significantly different at P < 0.05. Means lacking common letters differ. Color Score: 1 = bleached red, 2 = very light cherry red, 3 = moderately light cherry red, 4 = cherry red, 5 = slightly dark red, 6 = moderately dark red, 7 = dark red, 8 = very dark red.
Effect of HPP treatment (Normal pH Non-HPP Control (n=6), Dark-cutting Non-HPP Control (n=12), 300 MPa 90 s (n=6), 450 MPa 90 s (n=6)) within retail day on visual paleness score values of steaks. Data represent LS means ± SE. Means are considered significantly different at P < 0.05. Means lacking common letters differ. Paleness Score: 1 = very dark, 2 = dark red, 3= red, 4 = slightly pale, 5 = moderately pale, 6 = very pale.
Visual color scores mirrored these trends. The 450 MPa treatment consistently received lower color scores (lighter colored) than both control treatments across all retail display days (P ≤ 0.001) and lower scores than the 300 MPa treatment on d 1, 2, and 4 (Figures 5A–H). The 300 MPa steaks typically exhibited intermediate color scores, particularly during the latter portion of the display (P < 0.0001; Figure 5I-H).
Paleness scores further emphasized pressure-dependent effects. Steaks treated at 450 MPa exhibited the greatest paleness throughout the retail display (P < 0.0001; Figures 6A–H). In contrast, dark-cutting non-HPP control steaks most frequently exhibited the lowest paleness scores (d 0–3 and d 6–7), while normal-pH non-HPP controls exhibited lower paleness from d 3 through d 7 compared to HPP treated steaks.
pH Analysis
Steak pH was not affected by HPP treatment throughout the retail display (P > 0.05; Figures 7A–C). pH differences were observed between normal-pH and dark-cutting control steaks (P < 0.05). No differences were detected among dark-cutting non-HPP controls, 300 MPa, or 450 MPa treatments.
Effect of HPP treatment (Normal pH Non-HPP Control (n=6), Dark-cutting Non-HPP Control (n=12), 300 MPa 90 s (n=6), 450 MPa 90 s (n=6)) within retail day on pH values of steaks. Data represent LS means ± SE. Means are considered significantly different at P < 0.05. Means lacking common letters differ.
Thiobarbituric Acid Reactive Substances
Lipid oxidation, measured as TBARS, was influenced by HPP treatment in a pressure-dependent manner. No treatment differences were observed on d 0 (P = 0.8572; Figure 8A). However, a difference was detected on d 3 (P = 0.0004; Figure 8B) and d 7 (P = 0.0011; Figure 8C). On d 3, steaks subjected to 450 MPa exhibited the highest TBARS values, followed by the 300 MPa treatment, with both non-HPP control groups exhibiting the least lipid oxidation (P = 0.0004; Figure 8B). This pattern persisted on d 7, with 450 MPa steaks maintaining higher TBARS values than both control groups, while 300 MPa steaks were similar to normal-pH controls (P = 0.0011; Figure 8C).
Effect of HPP treatment (Normal pH Non-HPP Control (n=6), Dark-cutting Non-HPP Control (n=12), 300 MPa 90 s (n=6), 450 MPa 90 s (n=6)) within retail day on thiobarbituric reactive substances (mg of malondialhyde per kg of sample) of steaks. Data represent LS means ± SE. Means are considered significantly different at P < 0.05. Means lacking common letters differ.
Warner–Bratzler Shear Force
Warner–Bratzler shear force (WBSF) values were affected by HPP treatment on both d 0 (P = 0.0148; Figure 9A) and d 7 (P < 0.001; Figure 9B). On d 0, dark-cutting non-HPP control steaks exhibited lower WBSF values than steaks treated at 450 MPa (P = 0.0148; Figure 9A). By d 7, steaks treated at 450 MPa exhibited the highest WBSF values, whereas dark-cutting non-HPP control steaks remained the most tender. Steaks treated at 300 MPa and normal-pH non-HPP controls exhibited intermediate WBSF values (P < 0.001; Figure 9B).
Effect of HPP treatment (Normal pH Non-HPP Control (n=6), Dark-cutting Non-HPP Control (n=12), 300 MPa 90 s (n=6), 450 MPa 90 s (n=6)) within retail day on WBSF (kilograms of force kg/f)values of steaks. Data represent LS means ± SE. Means are considered significantly different at P < 0.05. Means lacking common letters differ.
Discussion
The Psoas major is among the most valuable beef cuts due to its exceptional tenderness, strong consumer recognition, and limited yield per carcass. Despite this premium, the tenderloin is inherently disadvantaged with respect to color stability and thus shelf-life viability. The Psoas major muscle is characterized by a high proportion of oxidative fibers and elevated mitochondrial density (Canto et al., 2016; Jeong et al., 2009), which accelerates oxygen consumption on the meat’s surface and limits oxymyoglobin formation (Lanari & Cassens, 1991; O’Keefe & Hood, 1982). Consequently, tenderloins discolor rapidly, shortening visual shelf-life relative to more color-stable muscles such as the Longissimus lumborum. Even so, advanced packaging technologies, including vacuum, modified atmosphere and nitrite embedded films, slows this rapid discoloration, helping to maintain both the quality and value at the retail counter (McMillian, 2017; Roberts et al., 2017: Claus et al., 2013). However, unlike rapid discoloration, which can be managed at the retail level with applied technologies, dark cutting defects result in discounts at the processing plant level, causing immediate and irreversible loss (Ramanathan et al., 2022).
Dark-cutting is a carcass-wide metabolic condition that impacts all muscles (Bass et al., 2008). Although limited literature has specifically evaluated the Psoas major under dark cutting conditions, the inherent color lability of the tenderloin often amplifies the visual severity of the defect, thereby exacerbating its impact on marketability and value, as illustrated by our sample population. To that end, we chose to investigate and evaluate post-harvest strategies capable of restoring the color and value of tenderloins from dark cutting carcasses.
It is well documented that high-pressure processing induces a lightening effect in meat, primarily through pressure-induced alterations in muscle proteins and myoglobin chemistry (reviewed by: Bolumar et al., 2021). Fundamental work by Carlez et al. (1995) demonstrated that normal pH beef exposed to pressures as low as 200 MPa exhibited a marked increase in lightness (L*), with additional lightening increases observed as pressure intensified. This pressure-induced lightening has since been corroborated by multiple studies and is often accompanied by reductions in redness (a*), particularly at higher pressure levels that exceed 400 MPa (Reesman et al., 2023a; Carlez et al., 1995). Fundamentally, these color changes are attributed to a combination of myoglobin oxidation, partial denaturation of the globin moiety, and denaturation of myofibrillar and sarcoplasmic proteins, which increases light scattering at the meat surface (Bak et al., 2019). As pressure increases beyond 300 MPa, the oxidation of oxymyoglobin to metmyoglobin and the disruption of the myoglobin structure further contribute to the development of a pale or gray appearance (Carlez et al., 1995).
Given the well-established susceptibility of fresh beef to pressure-induced discoloration, HPP has traditionally not been applied to fresh meat intended for retail display (Bolumar et al., 2012; Tang et al., 2005; Carlez et al., 1995;). However, dark-cutting beef presents a fundamentally different challenge as it presents with elevated pH, reduced light scattering properties, and abnormally dark lean which is heavily discounted despite being otherwise wholesome (Ponnampalam et al., 2017). In this context, the lightening effect associated with HPP, particularly at pressures at or above 300 MPa may be advantageous for restoring visual acceptability and value to dark-cutting product. Reesman et al. (2023a) evaluated this concept in dark-cutting Longissimus muscle and reported that pressures ranging from 300 to 450 MPa increased both lightness and redness, whereas treatment at 600 MPa resulted in excessive paleness consistent with protein denaturation.
Contrary to expectations, treatment at 300 MPa was not excessively aggressive in the tenderloin, producing lightness and redness values comparable to those of normal, non-HPP control steaks through d 3 of shelf-life while significantly improving color relative to untreated dark-cutting tenderloins. In contrast, application of 450 MPa resulted in excessive lightening and diminished color, indicating that pressure intensity plays a critical role in determining whether HPP functions as a value-restoring or color-compromising intervention in this muscle. This response reflects a pressure-threshold effect, whereby moderate pressure induces subtle structural modifications and sarcoplasmic proteins that increase light scattering while largely preserving myoglobin functionality (Cheah & Ledward 1996; Carlez et al., 1995). In high-pH tenderloins, the elevated pH may further stabilize muscle proteins and shift the onset of pressure-induced denaturation to higher pressure levels, allowing beneficial color changes to occur at 300 MPa without excessive pigment oxidation, whereas 450 MPa exceeds this pressure-threshold (Denzer et al., 2023; Djimsa et al., 2017; Brantley et al., 1993). Additionally, moderate pressure may partially suppress mitochondrial oxygen consumption, thereby improving oxygen availability at the meat surface and supporting oxymyoglobin formation in the inherently color-labile muscle (Tang et al., 2005).
Even so, high pH tenderloins treated at 300 MPa exhibited a gradual increase in lightness following d 3 of retail display, while a* values and b* values remained largely stable across the entire retail display and closely mirrored the trends observed in normal-pH controls. The increase in L* was not only recognized objectively through instrumental color but also trained visual color as noted by visual discoloration and paleness scores, which became noticeably apparent on d 3 as well. This convergence of objective and visual panel observations aligns with our TBARS results, suggesting that the observed lightening is at least partially driven by pressure-accelerated oxidation. Mechanistically, HPP can modify protein structure and increase the exposure of heme iron, promoting the formation of reactive oxygen species that gradually oxidize both myoglobin and lipids leading to discoloration and/or paleness (Bolumar et al., 2012; Tang et al., 2005; Carlez et al., 1995). Moderate pressures initially preserve oxymyoglobin, which may in part explain the why the improvement in color is maintained for approximately the first three days of shelf-life (Djimsa et al.,2017; Denzer et al., 2023). Although the data herein reflect the effects of HPP on a color-labile muscle, they align with Reesman et al. (2023a), and Sun et al. (2017), which also reported increased TBARS values with increased pressure in color-stable muscles, suggesting that, despite inherent differences between muscles, beef generally responds to HPP in a consistent manner with respect to the pressure-induced lipid oxidation. Moreover, our results show other similarities to that of HPP treated dark-cutting (high-pH) color-stable muscles. Similar to that of Reesman et al. (2023a), and Sun et al. (2017), HPP did not induce shifts in pH within treatment across time, suggesting changes in color occur in the absence of changes in pH. Another aspect that seems to follow that of HPP treated dark-cutting (high-pH) color-stable muscles is pressure exceeding 300 MPa effect on tenderness. HPP has repeatedly proven to have a slight toughening affect after high pressures (Reesman et al., 2023b; Sun et al., 2019; Jung et al., 2000), as it induces cross-linking of myofibrillar proteins (Bolumar et al., 2021). This cross-linking is only enhanced by continued gelation of proteins during the cooking process, resulting in a tougher product (Bak et al., 2019). Our data suggests that while there were no noted differences in WBSF values between normal-pH non HPP controls and 300 MPa treated steaks on d 0 or 7, WBSF values of high-pH steaks significantly increased on both days when subjected to 450 MPa. This challenges that of Reesman et al., (2023b), which reported a toughening effect at 300 MPa, but no difference at 450 MPa compared to the control. Still, Reesman et al (2023b) found their highest pressure (600 MPa) has a significant toughening effect, and while our highest pressure was much lower, it still shows our highest pressure produced a similar result. Even so, the WBSF values for all steaks would still be considered “tender” according to the tenderness grouping reported by Belew et al. (2003), indicating that the impact on eating quality would likely be minimal.
Conclusion
Collectively, these findings indicate that moderate pressure (300 MPa) initially improves color, but oxidative processes ultimately limit the persistence of these benefits. Moreover, our results highlight pressures of 450 MPa exacerbate lightening, accelerate lipid oxidation, and compromise tenderness, making it less viable in future work. However, 300 MPa highlights the potential of HPP as a post-harvest intervention for restoring color and value of dark-cutting tenderloins. Therefore, additional research is warranted to optimize processing parameters, including the use of lower pressures or shorter treatment times, and to incorporate consumer sensory evaluation to determine the practical feasibility of HPP as a value-restoration strategy for dark-cutting beef tenderloins.
Acknowledgements
Authors would like to thank our industry partner for donating tenderloins for the use of this project. This research was coordinated by the National Cattlemen’s Beef Association, a contractor to the Beef Checkoff.
Conflicts of Interest
The authors declare that there are no financial or personal relationships with other people or organizations that could inappropriately influence their work.
Author Contributions
Ashley A. Hahn, Methodology, Data curation, Writing – Original draft preparation, Writing – Review & Editing, Visualization; Leila G. Venzor, Methodology, Data curation; Shelley A. Curry, Data curation, Writing – Review & Editing; Grace C. Johnson, Methodology, Data curation; Mary-Grace C. Danao, Conceptualization, Methodology, Writing – Review & Editing; Ranjith Ramanathan, Conceptualization, Methodology, Writing – Review & Editing; Gary A. Sullivan, Conceptualization, Methodology, Writing – Review & Editing, Supervision; Jordan C. Wicks, Conceptualization, Methodology, Writing – Review & Editing, Supervision
Declaration of Ai-Assisted Technologies in The Manuscript Preparation Process
During the preparation of this work the authors used ChatGPT in order to improve readability and language. After using this tool/service, the authors reviewed and edited the content as needed and take full responsibility for the content of the published article.
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