Introduction
The use of freezing to extend shelf-life and hold products for use when supply is low has been used for centuries in various forms. Freezing meat is critical to the meat industry to minimize bacterial growth, allowing for more flexibility in storage and transportation as well as added shelf-life (Lagerstedt et al., 2008; Dang et al., 2021). There are few ways to extend the shelf-life of meat because its chemical attributes are prone to microbial spoilage in a fresh state (Dang et al., 2021). Consumers widely perceive that freezing meat results in reduced eating quality. Contrastingly, this claim is not supported by scientific research (Pietrasik and Janz, 2009). In recent years, based on personal communication with multiple industry partners, it has become increasingly popular to freeze primals before fabrication to reduce waste from fabrication to retail cuts. While this practice has been conducted, little knowledge exists on the implications on product yield, cooking loss, and palatability.
While freezing has been used for centuries, recent challenges in the supply and demand of beef have caused a greater amount of product to be frozen and thawed, and sometimes frozen and thawed again, prior to reaching the end consumer. During 2020, the COVID-19 pandemic caused numerous food service establishments to close, shifting products to retail (Darcy, 2021; Whitehead and Kim, 2022). Labor shortages and continued supply chain disruptions also forced many processors and marketers to alter their processing plans, sometimes forcing products to undergo multiple freeze-thaw cycles. Furthermore, rapidly shifting patterns in supply and demand have forced more packers to adopt freezing and thawing of primals to account for shifts in demand during certain times of year when demand is high while supply is low. Based on communication with packers and further processors, it is common for products to be frozen, thawed for fabrication, and then subsequently refrozen in order to be shipped to its final destination. Additionally, the increase in beef exports has led to more beef being frozen for shipping, which could undergo multiple freeze-thaw cycles before reaching at its final destination. Yet, little information exists within the body of research on the implications of numerous freeze-thaw cycles, especially on consumer palatability traits.
Previous freezing research has primarily focused on the impacts of ice crystal formation and the subsequent impacts on tenderness. It is well established that freezing causes ice crystals to form between muscle fibers, thus damaging the cellular membrane (Rahelić et al., 1985a; Rahelić et al., 1985b; Qian et al., 2022). Damage to the cell membrane allows for increased moisture loss upon thawing when compared to fresh, never-frozen products, resulting in less consumer satisfaction (Wheeler et al., 1990; Lagerstedt et al., 2008; Beyer, 2023). While inconsistent in the research, a few studies have also observed decreased shear-force values in whole muscle beef cuts because of ice crystal formation (Lagerstedt et al., 2008; Kim et al., 2018). In addition, a faster rate of freezing caused by lower temperatures creates less intercellular ice crystal formation and smaller, more uniformly shaped ice crystals, thus reducing muscle fiber damage (Rahelić et al., 1985a). However, freezing rate and temperature have not been shown to have any impact on shear force values or thaw loss (Eastridge and Bowker, 2011; Hergenreder et al., 2013; Kim et al., 2015). Recent research by Beyer et al;. (2023) reported a decrease in the perceived juiciness by consumers in frozen steaks.
Changes in supply and demand of beef products forced several processors to shift their production models to utilizing previously frozen products. While the impacts of freezing have been studied, little information exists on the impact of beef undergoing multiple freeze-thaw cycles on consumers’ eating experience. The objective of this study was to evaluate the impact of frozen versus thawed fabrication and subsequent refreezing on the palatability, thaw loss, and cook loss of beef longissimus lumborum steaks.
Materials and Methods
Product collection
Twenty paired (left and right sides; total strip loins = 40) US Department of Agriculture (USDA) Low Choice strip loins (longissimus lumborum; IMPS #180) were collected from a commercial beef processing facility at 2 d postmortem. Carcass data (hot carcass weight, preliminary yield grade, adjusted preliminary yield grade, ribeye area marbling score, skeletal maturity score) were collected by the Oklahoma State University research team and reported in Table 1. In addition, strip loins were tagged, and their unique identity was maintained throughout fabrication to ensure that matched pairs were used throughout analysis. Strip loins were vacuum-packaged and transported on ice to the Robert M. Kerr Food and Agricultural Products Center at Oklahoma State University.
Average, minimum, and maximum values for HCW, PYG, APYG, REA, marbling score, skeletal maturity score, and loin pH for beef heifer carcasses (n = 20)
| Average | Minimum | Maximum | |
|---|---|---|---|
| HCW, kg | 460 | 367 | 534 |
| PYG | 3.82 | 2.8 | 5.1 |
| APYG | 4.09 | 3.0 | 5.5 |
| REA, cm2 | 92.3 | 87.1 | 98.7 |
| Marbling scorea | 450 | 420 | 490 |
| Skeletal scoreb | 162 | 140 | 190 |
| Loin pH | 5.41 | 5.26 | 5.83 |
Abbreviations: APYG, adjusted preliminary yield grade; HCW, hot carcass weight; PYG, preliminary yield grade; REA, ribeye area.
Marbling scores were converted to numerical values ranging from 420 (Small20) to 490 (Small90).
Skeletal scores were converted to numerical values ranging from 140 (A40) to 190 (A90).
Packaging and storage
Upon arrival at Oklahoma State University, each strip loin was wet aged for 21 d at 4°C. Vacuum packages were checked periodically throughout aging for any leaking seals and were repackaged if broken bags or seals were found. After aging, each strip loin was weighed and then frozen at −21°C for 14 d. At the end of the 14-d period, each of the paired loins was assigned to either remain frozen or be thawed to ensure an equal number of left and right sides were assigned to be frozen or thawed. The strip loins designated to remain frozen were held at −21°C for an additional 7 d. The strip loins designated to be thawed were held at 4°C for 7 d. Following the freeze or thaw period, strip loins were weighed and fabricated into 2.54-cm-thick steaks using a bandsaw (Biro Manufacturing Co., Cleveland, OH) starting at the anterior end. The anterior face steak was designated for proximate analysis. Nine steaks from each loin were randomly but equally assigned to 1 of 3 freezing temperatures: −12°C, −18°C, or −21°C. One steak within each temperature per loin was assigned to either a consumer sensory panel, trained sensory panel, or Warner-Bratzler shear force (WBSF). Also, steaks designated for WBSF were utilized to assess cooked lipid oxidation. Steaks designated for trained sensory and consumer sensory analysis were used to evaluate thaw and cook loss. Internal cooked color analysis was conducted on steaks designated for trained sensory analysis. Steaks were individually weighed, vacuum-packaged, boxed in bulk, and placed in designated temperature frozen storage for 180 d. Frozen temperatures were monitored throughout the study, and freezers were defrosted according to manufacturer’s recommendations.
Thaw and cook loss
Loins were weighed prior to initial freezing and before fabrication to determine moisture loss from the first freezing cycle. Weights were taken while still in the package. Loins were removed from the package, patted dry with a paper towel, and weighed. The packaging and tag were air-dried and weighed, and total thawing loss was calculated for the first freezing cycle using the following formula: ((packaged loin weight – unpackaged loin weight – package weight)/packaged loin weight) × 100. After thawing for 24 h at 4°C, steaks designated for WBSF, trained sensory analysis, and consumer sensory analysis were weighed in the package, removed from the package, patted dry with a paper towel, and weighed. Following weighing, steaks were cooked to 68°C and tempered to 71°C using a Rational oven (Model SCC WE 102G, Rational AG Landsberg am Lech, Germany) set to 204°C with 0% humidity. Temperature of steaks was monitored throughout cooking with the oven thermometer, and tempered temperature was measured using a Thermapen Mk4 (Thermoworks, American Fork, UT). Packaging and tags were dried and weighed, and total thawing loss was calculated for the second freezing cycle using the following formula: ((packaged steak weight – unpackaged steak weight – package weight)/packaged steak weight) × 100. Steaks were cooked as described for WBSF, and peak temperatures were recorded. To calculate cooking loss, raw steak weight from thawing loss calculation was used, and cooked weight was taken after peak temperatures were reached. The formula used for cooking loss is as follows: ((raw steak weight – cooked steak weight)/raw steak weight) × 100.
WBSF
WBSF was performed according to the Sensory Guidelines of the American Meat Science Association (AMSA) (AMSA, 2016). Steaks were cooked as previously described for cook loss measurement and placed onto metal pans and cooled for 18 h at 4°C prior to shearing. Six cores were taken from each steak (1.27 cm in diameter) parallel to the muscle fiber orientation. An Instron Universal Testing Machine (Model 66 5943; Instron Corporation; Norwood, MA) outfitted with the manufacturer’s WBSF blade was used to evaluate the maximum load (kgf) of each core, and the average of the 6 cores per sample was used for the analysis. The crosshead speed was set at 250 mm/s.
Trained sensory panel
The Oklahoma State University Institutional Review Board approved both consumer and trained panel analyses (approval number: IRB-22-434). Sensory panelists were trained according to the AMSA Sensory Guidelines (AMSA, 2016). Trained panels occurred over a 2-wk period, with each panel consisting of 8 trained panelists. Steaks were thawed and cooked using the same method as steaks used for WBSF. Peak temperatures were verified and recorded using a thermometer (Thermopen mk4, Salt Lake City, UT). Samples were cut into pieces (1 cm × 1 cm × 1.9 cm) using a cutting guide to ensure piece uniformity. Samples were held in a commercial warmer until fed to panelists. Panelists were served 12 samples, 2 of each treatment combination, in random order. Each panelist was served two 1 cm × 1 cm × 1.9 cm pieces of each sample.
Panelists were provided a napkin, toothpick, water cup, expectorant cup, and unsalted crackers. Moreover, panelists were provided a paper survey consisting of 6 questions, evaluated on an 8-point scale for initial juiciness, sustained juiciness, tenderness, connective tissue amount, beef flavor intensity, and off-flavor intensity (1 = extremely dry, 8 = extremely juicy; 1 = extremely tough, 8 = extremely tender; 1 = no connective tissue, 8 = abundant connective tissue; 1 = extremely bland, 8 = extremely intense). Samples were evaluated under red lighting to prevent degree of doneness bias. The panelists were given a “warm-up” sample before beginning to prevent panelist drift.
Internal cooked color
Steaks used for internal cooked color analysis were prepared as described in the trained sensory analysis. Following cooking, steaks were sliced perpendicular to the cut surface, and internal cooked color was measured by taking 3 surface color measurements using a HunterLab 4500L MiniScan EZ Spectrophotometer (2.5-cm aperture, illuminant A, and 10° standard observer angle; HunterLab Associates, Reston, VA). The CIE L*, a*, and b* values and spectral readings from 400–700 nm were used to evaluate the internal cooked color. Chroma and hue values were calculated according to the AMSA color guidelines (King et al., 2023). Additionally, 8 trained panelists evaluated cooked color on a 6-point scale (1 = very red/rare, 3 = pink/medium rare, 6 = tan/brown/very well).
Consumer sensory panel
Untrained consumer panelists (n = 160) from the Stillwater, OK area were recruited and compensated for their participation. Ten-panel sessions took place at Oklahoma State University in a large lecture-style room with 16 panelists per session. Samples were prepared as described for trained sensory analysis. Consumers were asked to evaluate 6 samples during the panel session. Each steak was cut in a way in which 8 individual panelists received 2 pieces each.
Consumers filled out a digital survey (Qualtrics Software, Provo, UT) using individual smartphones. The survey consisted of a demographics survey, beef consumption survey, and a 6-sample evaluation survey. The demographics survey included the following information: gender, age, ethnicity, pre-tax annual household income level, and education level. Consumers answered questions numerically describing their monthly beef consumption and purchasing habits, most important trait when eating steak, and endpoint cookery preference. Consumers evaluated samples on a 9-point hedonic scale rating tenderness, juiciness, flavor liking, and overall liking (1 = extremely tough, 9 = extremely tender; 1 = extremely dry, 9 = extremely juicy, 1 = dislike extremely, 9 = like extremely). Additionally, a yes-or-no question was answered to determine if off-flavor was detectable in the sample. An additional space was left for consumers to provide any off-flavor descriptors or additional sample comments at the end of the survey for each sample. Consumers were provided a napkin, toothpick, water cup, expectorant cup, and unsalted crackers. Prior to beginning, consumers were verbally given instructions regarding the ballot, testing procedures, and palate cleansers.
Thiobarbituric acid reactive substances
Lipid oxidation was evaluated after the second frozen storage time using a modified version of the thiobarbituric acid (TBA) reactive substances assay (Witte et al., 1970). Steaks were cooked as described for the WBSF analysis. A 3-g sample from the exterior surface was blended with 27 mL of trichloroacetic acid (TCA) in a Waring commercial blender (Model 33BL7; New Hartford, CT) for 10 s. After blending, each sample was filtered through a Whatman 42 filter paper. After filtration, 1 mL of filtrate was added with 1 mL of TBA in a glass test tube. The test tube was then placed in a water bath at 100°C for 10 min and then cooled at room temperature for 5 min. Absorbance was measured at 532 nm using a spectrophotometer (UV-2600, UV-VIS Spectrophotometer; Shimadzu; Columbia, MD). One mL of TCA was mixed with 1 mL of TBA to represent the standard. Lipid oxidation values were reported as mg malonaldehyde/kg meat according to the equation provided in the AMSA color guidelines (King et al., 2023).
Statistical analysis
For loin fabrication yield following the first freeze-thaw cycle, a randomized complete block design was used in which the experimental unit was considered the loin, and treatments were blocked by the carcass. Following the second freeze-thaw cycle, a split-plot design was utilized to determine the effects of fabrication state and frozen storage temperature for all analyses. In the whole plot, a randomized complete block design was used to evaluate the effects of fabrication state (frozen or thawed). The whole plot experimental unit was loin and blocked by animal. In the sub-plot, each steak was allocated to either a −12°C, −18°C, or −21°C frozen storage temperature. Twenty paired (left and right side) strip loins served as replicates. The fixed effects included fabrication state, freezing temperature, and their interactions.
The least-squares means were determined using the PROC GLIMMIX procedure of SAS (SAS 9.4; SAS Inst.; Cary, NC) and were considered significant at P < 0.05. In addition, Kenward-Roger was utilized throughout all analyses for the denominator degrees of freedom. Using the PDIFF options, least-squares means were separated, and the LINES statement was used to generate superscripts when overall F-test indicated significant differences.
Results
Lipid oxidation
There were no (P > 0.05) differences in the lipid oxidation values when comparing the impact of fabrication status and frozen storage temperature (Table 2).
Least-squares means for moisture loss percentagea, thaw loss percentageb, cook loss percentagec, WBSFd, TBARS valuese for beef strip loins (n = 40) fabricated from a frozen or thawed state, and beef longissimus lumborum steaks (n = 240) subjected to 3 different frozen storage temperatures following fabrication
| Treatment | Fabrication Moisture Loss, % | Steak Thaw Loss, % | Steak Cook Loss, % | WBSF, kg/f | TBARS, mg MDA eq/kg |
|---|---|---|---|---|---|
| Freeze-thaw cycles | |||||
| 1 cycle | 1.98b | 3.61a | 20.77 | 2.85f | 0.403 |
| 2 cycles | 7.00a | 2.16b | 20.50 | 2.36f | 0.381 |
| Standard error | 0.38 | 0.16 | 0.34 | 0.75 | 0.01 |
| P value | <0.0001 | <0.0001 | 0.58 | <0.001 | 0.06 |
| Frozen storage temperature | |||||
| −12°C | 3.06 | 20.57 | 2.57 | 0.398 | |
| −18°C | 2.73 | 20.62 | 2.62 | 0.392 | |
| −21°C | 2.86 | 20.72 | 2.62 | 0.388 | |
| Standard error | 0.20 | 0.38 | 0.07 | 0.008 | |
| P value | 0.48 | 0.95 | 0.77 | 0.66 | |
| Interaction P value | 0.49 | 0.97 | 0.62 | 0.69 | |
Abbreviations: MDA, malondialdehyde; TBARS, thiobarbituric acid reactive substance; WBSF, Warner-Bratzler shear force.
Initial and post-freezing/thawing weights of strip loins were recorded (post-freezing/thawing weight/initial weight × 100).
Initial and post-freezing/thawing weights of steaks were recorded (post-freezing/thawing weight/initial weight × 100).
Initial and post-cooking weights of steaks were recorded (post-cooking weight/initial weight × 100).
WBSF values in which smaller values indicate greater tenderness and less shear force required to bite through sample.
TBARS values presented in which higher values indicate greater lipid oxidation.
Means within treatment and trait without a common superscript differ (P < 0.05).
Thaw and cook loss
Loin and steak thaw and cook loss percentages are presented in Table 2. Loins thawed before fabrication had a higher percentage (P < 0.05) of thaw loss when compared with loins fabricated frozen. There was a 5.02% difference in moisture loss between frozen and thawed strip loins. Correspondingly, steaks from loins enduring only 1 freeze-thaw cycle reported greater thaw loss (P < 0.05) than steaks from loins that underwent 2 freeze-thaw cycles. Overall, loins that were thawed prior to fabrication incurred numerically 292.6 g more total moisture loss when compared to loins kept in a frozen state for fabrication. This translates to a numerical increase of 19.51 g in total steak moisture loss for steaks from loins, which underwent 2 freeze-thaw cycles. Steaks from loins enduring one freeze-thaw cycle resulted in $1.64 of lost value due to moisture loss, while steaks from loins undergoing two freeze-thaw cycles lost $2.02. These values were calculated based on weight loss during thawing and current reported values of USDA Choice strip loins (IMPS #180; USDA, 2024). Overall, loins fabricated in a frozen state retained $5.71 in value over those fabricated in a thawed state. However, frozen storage temperature did not (P > 0.05) affect steak thaw loss. Neither steaks from loins enduring 1 or 2 freeze-thaw cycles had a significant difference (P > 0.05) in cook loss percentage. Likewise, frozen storage temperature had no effect (P > 0.05) on percent cook loss.
WBSF
Values for WBSF are displayed in Table 2. Steaks from loins experiencing 2 freeze-thaw cycles had lower (P < 0.0001) WSBF values when compared to steaks from loins undergoing 1 freeze-thaw cycle. Frozen storage temperature resulted in no differences (P > 0.05) in WBSF values. No interaction was found (P > 0.05) between the number of freeze-thaw cycles or frozen storage temperature.
Trained sensory panel
Trained panelists’ least-squares means for all palatability characteristics are represented in Table 3. Trained panelists found no differences (P > 0.05) in initial juiciness, sustained juiciness, tenderness, connective tissue amount, off-flavor, or beef flavor when comparing steaks that underwent 1 or 2 freeze-thaw cycles. Moreover, frozen storage temperature had no effect (P > 0.05) on any palatability characteristic.
Least-squares means for trained sensory panel palatability ratingsa for beef longissimus lumborum steaks (n = 120) fabricated from a frozen or thawed state and subjected to 3 different frozen storage temperatures following fabrication
| Treatment | Initial Juiciness | Sustained Juiciness | Tenderness | Connective Tissue Amount | Off-Flavor | Beef Flavor |
|---|---|---|---|---|---|---|
| Freeze-thaw cycles | ||||||
| 1 cycle | 3.87 | 3.69 | 4.30 | 1.68 | 1.65 | 3.33 |
| 2 cycles | 3.73 | 3.55 | 4.36 | 1.61 | 1.49 | 3.27 |
| Standard error | 0.92 | 0.09 | 0.95 | 0.06 | 0.71 | 0.61 |
| P value | 0.10 | 0.08 | 0.64 | 0.34 | 0.10 | 0.31 |
| Frozen storage temperature | ||||||
| −12°C | 3.73 | 3.55 | 4.26 | 1.70 | 1.55 | 3.31 |
| −18°C | 3.77 | 3.58 | 4.31 | 1.59 | 1.56 | 3.28 |
| −21°C | 3.90 | 3.73 | 4.42 | 1.65 | 1.59 | 3.30 |
| Standard error | 0.10 | 0.10 | 0.10 | 0.06 | 0.07 | 0.63 |
| P value | 0.14 | 0.11 | 0.31 | 0.27 | 0.86 | 0.82 |
| Interaction P value | 0.79 | 0.79 | 0.49 | 0.10 | 0.32 | 0.76 |
Sensory scores: 1 = extremely dry, 8 = extremely juicy; 1 = extremely tough, 8 = extremely tender; 1 = no connective tissue, 8 = abundant connective tissue; 1 = extremely bland/no off-flavor, 8 = extremely intense/intense off-flavor.
Internal cooked color
Internal cooked color data are presented in Table 4. Trained cooked color evaluators were unable to detect (P > 0.05) differences in the internal cooked color of steaks regardless of the number of freeze-thaw cycles. Moreover, no differences (P > 0.05) were found in the internal cooked color of steaks frozen at 3 different storage temperatures. The number of freeze-thaw cycles had no effect on internal cooked color L*, a*, b*, chroma, hue, or 630/580 values. Similarly, frozen storage temperature resulted in no difference (P > 0.05) in L*, a*, b*, chroma, hue, or 630/580 instrumental cooked color values.
Least-squares means for trained panelist ratingsa, L*b, a*c, b*d, chromae, huef, and 630/580 nmg internal cookedh color valuesa of beef longissimus lumborum steaks (n = 120) fabricated from a frozen or thawed state and subjected to 3 different frozen storage temperatures following fabrication
| Treatment | Panelist Rating | L* | a* | b* | Chroma | Hue | 630/580 nm |
|---|---|---|---|---|---|---|---|
| Freeze-thaw cycles | |||||||
| 1 cycle | 3.60 | 51.50 | 22.48 | 20.37 | 30.56 | 42.32 | 3.03 |
| 2 cycles | 3.58 | 52.13 | 22.10 | 19.96 | 29.77 | 42.26 | 2.96 |
| Standard error | 0.13 | 0.53 | 0.42 | 0.27 | 0.46 | 0.31 | 0.92 |
| P value | 0.82 | 0.40 | 0.44 | 0.30 | 0.39 | 0.89 | 0.59 |
| Frozen storage temperature | |||||||
| −12°C | 3.71 | 51.57 | 22.48 | 20.42 | 30.39 | 42.35 | 3.04 |
| −18°C | 3.43 | 51.85 | 22.13 | 20.16 | 30.11 | 42.29 | 3.02 |
| −21°C | 3.64 | 52.02 | 22.01 | 19.92 | 29.70 | 42.24 | 2.94 |
| Standard error | 0.14 | 0.51 | 0.47 | 0.31 | 0.53 | 0.37 | 0.10 |
| P value | 0.09 | 0.75 | 0.75 | 0.48 | 0.61 | 0.98 | 0.74 |
| Interaction P value | 0.07 | 0.26 | 0.44 | 0.48 | 0.43 | 0.59 | 0.49 |
Cooked color sensory scores: 1 = very red/rare; 3 = pink/medium rare; 6 = tan/brown/very well.
L* values: higher values indicate brightness.
a* values: higher values indicate a redder color.
b*values: higher values indicate yellowness.
Chroma values: higher values indicate surface redness.
Hue values: higher values indicate surface yellowness.
Ratio of 630/580 nm calculated from reflectance spectra. A number closer to 1 indicates a browner cooked color.
Steaks were cooked to an internal temperature of 71°C using a Rational oven.
Consumer demographic and purchasing motivators
The demographic information of the 160 consumer panelists is shown in Table 5. Panelists were primarily female (62.3%) and married (70.0%) rather than male (37.7%) and single (30.0%). Additionally, panelists were largely composed of Caucasian (72.5%) individuals below 40 y of age (74.3%) living in a household of 4 people or fewer (77.2%) and had at least some college education (90.6%). The participants’ household income was predominantly between $75,000 and $150,000 (54.4%). Flavor (50.0%) was the most frequent response by panelists when asked which palatability trait was the most important when consuming beef steaks, followed by tenderness (31.1%) and juiciness (11.9%). Consumers’ preferred doneness was medium-rare (51.3%), followed by medium (20.6%). Consumers predominantly consumed (75.6%) and purchased (47.5%) beef more than 5 times a month.
Demographic characteristics of consumers (n = 160) who participated in beef longissimus lumborum steaks consumer sensory panel for steaks fabricated from a frozen or thawed state and subjected to 3 different frozen storage temperatures following fabrication
| Characteristic | Response | Percentage of Consumers |
|---|---|---|
| Gender | Male | 37.7 |
| Female | 62.3 | |
| Household size | 1 person | 11.2 |
| 2 people | 35.0 | |
| 3 people | 30.0 | |
| 4 people | 16.2 | |
| 5 people | 3.8 | |
| 6 people or greater | 3.8 | |
| Marital status | Married | 70.0 |
| Single | 30.0 | |
| Age, y | <20 | 8.7 |
| 20–29 | 11.2 | |
| 30–39 | 54.4 | |
| 40–49 | 10.0 | |
| 50–59 | 11.9 | |
| >60 | 3.8 | |
| Ethnic origin | African American | 0.6 |
| Asian | 11.2 | |
| Caucasian/White | 72.5 | |
| Hispanic | 7.5 | |
| Mixed race | 2.5 | |
| Native-American | 3.8 | |
| Other | 1.9 | |
| Household income | <$25,000 | 8.1 |
| $25,000–$49,999 | 16.3 | |
| $50,000–$74,999 | 7.4 | |
| $75,000–$99,999 | 37.5 | |
| $100,000–$149,999 | 16.9 | |
| $150,000–$199,999 | 7.5 | |
| >$199,999 | 6.3 | |
| Education level | Non–high school graduate | 0.6 |
| High school graduate | 8.8 | |
| Some college/technical school | 30.6 | |
| College graduate | 28.1 | |
| Advanced degree | 31.9 | |
| Most important palatability trait when consuming beef steaks | Tenderness | 31.1 |
| Juiciness | 11.9 | |
| Flavor | 50.0 | |
| Preferred degree of doneness when consuming beef steaks | Very rare | 3.8 |
| Rare | 6.9 | |
| Medium rare | 51.3 | |
| Medium | 20.6 | |
| Medium well | 11.2 | |
| Well done | 4.4 | |
| Monthly beef consumption | 0 times | 0.0 |
| 1 time | 1.9 | |
| 2 times | 3.1 | |
| 3 times | 8.8 | |
| 4 times | 10.6 | |
| 5 or more times | 75.6 | |
| 0 times | 3.7 | |
| Monthly beef purchasing | 1 time | 9.4 |
| 2 times | 11.9 | |
| 3 times | 18.1 | |
| 4 times | 9.4 | |
| 5 or more times | 47.5 |
Consumer sensory panel
Consumer panelist least-squares means for palatability characteristics are reported in Table 6. There were no differences (P > 0.05) in number of freeze-thaw cycles for tenderness, juiciness, flavor liking, off-flavor detection, and overall liking of the sample. Similarly, no differences (P > 0.05) were noted between any frozen storage temperature for all the consumer sensory traits evaluated.
Least-squares means for consumer sensory panel (n = 160) palatability ratingsa for beef longissimus lumborum steaks fabricated frozen or thawed and subjected to 3 different frozen temperatures following fabrication
| Treatment | Tenderness | Juiciness | Flavor Liking | Off-Flavorb, % | Overall Liking |
|---|---|---|---|---|---|
| Freeze-thaw cycles | |||||
| 1 cycle | 6.22 | 5.96 | 5.76 | 11.31 | 5.83 |
| 2 cycles | 6.34 | 5.75 | 5.65 | 11.49 | 5.91 |
| Standard error | 0.15 | 0.15 | 0.12 | 0.13 | 0.13 |
| P value | 0.49 | 0.27 | 0.35 | 0.93 | 0.58 |
| Frozen storage temperature | |||||
| −12°C | 6.19 | 5.78 | 5.65 | 13.00 | 5.79 |
| −18°C | 6.40 | 5.88 | 5.71 | 10.65 | 5.88 |
| −21°C | 6.26 | 5.91 | 5.76 | 10.69 | 5.95 |
| Standard error | 0.16 | 0.16 | 0.13 | 0.22 | 0.14 |
| P value | 0.49 | 0.27 | 0.35 | 0.93 | 0.56 |
| Interaction P value | 0.62 | 0.99 | 0.24 | 0.46 | 0.08 |
Sensory score: 1 = extremely tough/dry, extremely dislike flavor/overall; 9 = extremely tender/juicy, extremely like flavor/overall; No = no off-flavor detected; Yes = off-flavor detected.
Off-flavor expressed as % of panelists who indicated “Yes” off-flavor was detected.
Discussion
Freezing temperature following fabrication had no impact on any of the objective and subjective palatability measurements conducted in this study. The effects of freezing rate on meat quality has been well studies within the literature (Farouk et al., 2003; Kim et al., 2015; Setyabrata et al., 2019). During freezing, the rate of freezing has been reported to impact the cellular structure of meat, which ultimately impacts the water holding capacity (Huff-Lonergan and Sosnicki, 2005; Dang et al., 2021). While the industry maintains relatively standard freezing temperatures, times during transport and once the product arrives at the food service establishment may be indicative of more variable frozen storage temperatures. When designing this study, we hypothesized that there might be differences in lipid oxidation and tenderness values due to the frozen storage temperatures in the second freezing cycle. Previous research from Viera et al. (2009) indicated no difference in lipid oxidation and tenderness values when freezing at −20°C and −80°C. The temperatures utilized in the present study ranged from −12°C to −21°C, which we hypothesize might not have been a large enough range in temperature to induce significant cellular and oxidative changes like previous studies indicated.
Freezing and its impacts on tenderness have been extensively researched. However, little literature is available on the impact of multiple freeze-thaw cycles on myofibrillar tenderness. Ice crystal formation leading to the rupture of the cell membrane results in an improvement of instrumental tenderness by decreasing the shear force (Rahelić et al., 1985b; Grayson et al., 2014). Our study demonstrated an improvement in objective tenderness with an 17.2% decrease in WBSF values with an additional freeze-thaw cycle. While mechanical tenderness was improved by freezing, both trained and consumer panelists could not detect a difference. Steaks from both loins undergoing 1 or 2 freeze-thaw cycles resulted in WBSF values below the threshold values for “Certified Very-Tender” designation (ASTM, 2011). Neither trained nor untrained panelists detected any sensory differences between a number of freeze-thaw cycles. In addition, the freezing temperature did not impact tenderness in our study both from an objective and subjective perspective. We attribute this to a smaller range in freezing temperature and the refreezing occurring on steaks, which would have frozen much quicker, causing less membrane damage.
Results of our study did not indicate a difference in lipid oxidation between steaks that had undergone 2 freeze-thaw cycles versus those that underwent a single freeze-thaw cycle. All lipid oxidation values for both number of freeze-thaw cycles and freezing temperature fell below the threshold value (<2.0 mg malondialdehyde/kg) for consumer detection of lipid oxidation (Love and Pearson, 1971). Previous studies by Setyabrata and Kim (2019) and Rahman et al. (2015) have concluded that multiple freeze-thaw cycles can result in significant increase in lipid oxidation. However, in the cases of both previous published studies, the aging period was not held constant, which could be partially responsible for the differences in findings relative to our study. Ice crystal formation and dissolution can disrupt cell membrane stability, thus initiating the release of metals and heme proteins, which function as prooxidants, and increasing the level of lipid oxidation (Zhang et al., 2023). Oxidation occurring within multiple freeze-thaw cycles can lead to detrimental changes in flavor and overall acceptability in sensory evaluations (Xia et al., 2009).
Maximizing yield is a major economic driver for those involved in fabricating and selling products into food service. Steaks from loins enduring 1 freeze-thaw cycle resulted in $1.64 of lost value due to moisture loss, while steaks from loins undergoing 2 freeze-thaw cycles lost $2.02 in value based on current reported values of USDA Choice strip loins. This results in $0.38 per steak savings by fabricating loins in a frozen state rather than in a thawed state. Overall, loins fabricated in a frozen state retained $5.71 in value over those fabricated in a thawed state. This difference over several thousand pounds of product would lead to significant economic implications. To the best of our knowledge, no scientific studies have evaluated the economic impacts of frozen versus thawed fabrication. Further studies are warranted to evaluate the economic differences between freezing and thawing in order to document the entire economic basis. A significant economic incentive could be found in the decreased moisture loss derived from frozen fabrication and a single freeze-thaw cycle.
Conclusion
Neither fabrication state (frozen or thawed) nor frozen storage temperature substantially impacted beef steak quality characteristics. No differences in palatability were detected by consumers or trained panelists. However, loins and steaks from loins that were thawed prior to fabrication significantly increased thaw loss percentages compared to those fabricated in a frozen state. Increased thaw loss affects fresh meat yield and has a negative economic impact. For example, loins fabricated in frozen state retained $5.71 in value over those fabricated in a thawed state after freezing. Therefore, to maximize fresh meat yield and consumer palatability, frozen loins should remain frozen through fabrication and only be thawed before cooking.
Conflict of interest
The authors declare no conflicts of interest regarding the content of this manuscript.
Acknowledgments
This research was coordinated by the National Cattlemen’s Beef Association, a contractor to the Beef Checkoff.
Author Contributions
Jade Edwards conducted the study and wrote the draft manuscript; Keayla Harr conducted the study and edited the draft manuscript; Morgan Denzer edited the manuscript; Morgan Pfeiffer edited the manuscript; Gretchen Mafi edited the manuscript script and supervision; and Ranjith Ramanathan edited the manuscript, funding, and supervision.
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