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Consumers consider beef color to be an indicator of freshness and therefore it is a major factor when purchasing beef. The ideal conditions for maintaining color throughout retail display following frozen storage have yet to be well established. Therefore, the objective of this study was to determine the effects of myoglobin oxygenation levels (especially high oxygenation) during freezing on color stability of thawed steaks during retail display (RD) and to determine the impact that frozen storage duration, aging, and packaging films have on meat color after thawing under RD conditions. USDA Choice strip loins (n = 36) were aged for 4 or 20 d. Steaks were randomly assigned to a myoglobin oxygenation level [deoxymyoglobin (DeOxy; packaged within 3 min), oxygenation (Oxy; oxygenated in air for 30 min), or high oxygenation (HiOxy; packaged for 24 h in 80% O2)]. Steaks were then vacuum packaged in oxygen permeable or impermeable film and immediately frozen (−10 °C). Following either 0, 2, 4, or 6 months of frozen storage at -5 °C, steaks were removed from the packaging and immediately placed under simulated RD conditions for 7 d. During RD, instrumental color and subjective color were measured every day after the initial 24 h thaw period. Steaks were analyzed for instrumental color (L*, a*, b*), a*:b* ratio, percentage oxymyoglobin, metmyoglobin, and deoxymyoglobin, delta E, redness ratio, subjective discoloration, and lipid oxidation. For all days of RD, steaks that were frozen for 0 months had higher a* values (greater redness) than steaks frozen for 6 months which typically had the lowest a* values (P

ObjectivesMeat color is the number one factor influencing consumer purchase decisions. The emerging market of frozen meat emphasizes the need to understand beef surface discoloration and the ideal parameters of freezing beef to retain a superior color. Therefore, the objectives of this study were to determine the impacts of oxygenation level and frozen storage duration on frozen beef color.Materials and MethodsUSDA Choice strip loins (n = 36) were aged for 4 d or 20 d. Steaks were randomly assigned to a myoglobin state [deoxymyoglobin (DeOxy; immediately packaged), low oxygenation (LoOxy; oxygenated in air for 30 min), and high oxygenation (HiOxy; packaged for 24 h in 80% O2)]. Steaks were then vacuum packaged in oxygen permeable or impermeable film and immediately frozen (–20°C). Following either 0, 2, 4, or 6 mo of frozen storage, steaks were removed from the packaging and immediately analyzed for instrumental color (L*, a*, b*), delta E (magnitude of difference in the L*, a*, b* color space), subjective discoloration, lipid oxidation (via thiobarbituric acid reactive substances- TBARS), oxygen penetration, percent oxymyoglobin, metmyoglobin, and deoxymyoglobin (via spectrometer), and redness (calculated as 630nm/530nm). Data were analyzed using PROC Glimmix procedure in SAS as a split-split-plot with an incomplete block and a 2 × 3 factorial.ResultsHiOxy steaks had greater oxygen penetration and the highest a* values compared to DeOxy and LoOxy steaks regardless of packaging (P < 0.0005). Conversely, DeOxy steaks exhibited the lowest oxygen penetration and a* values regardless of film (P < 0.0005). HiOxy steaks at 4 d had higher a* values than DeOxy and LoOxy at all storage times (P = 0.0118). HiOxy steaks had the highest delta E values compared to DeOxy and LoOxy in permeable packaging and with increasing storage time an increase in delta E for the HiOxy steaks was observed (P = 0.0010).Redness and percent oxymyoglobin were highest for HiOxy steaks within each storage period (P < 0.0002). HiOxy and LoOxy steaks were similar in percent oxymyoglobin when in permeable packaging film. HiOxy steaks had the highest percent oxymyoglobin and DeOxy had the lowest percent oxymyoglobin within each aging and storage period (P < 0.01). Conversely, DeOxy steaks had the highest percent metmyoglobin and HiOxy had the lowest percent metmyoglobin when packaged in impermeable film (P < 0.0001). Lowest percent metmyoglobin values were from the 4 d HiOxy steaks at 2, 4, and 6 mo of storage (P = 0.0188).The HiOxy 20 d steaks had the highest discoloration compared to 4 d aging and more discoloration than all other myoglobin treatments at 6 mo of storage (P < 0.0001). Lipid oxidation increased with storage time (P = 0.0169). HiOxy 20 d aged steaks exhibited the highest TBARS values at 2, 4, and 6 mo (P = 0.0224). HiOxy and LoOxy were similar in discoloration and lipid oxidation except with the HiOxy 20 d (which were less desirable).ConclusionHiOxy steaks exhibit a brighter and deeper cherry red color compared to the DeOxy steaks. HiOxy steaks were superior or similar when compared to LoOxy steaks but displayed more detrimental effects when frozen storage was extended. Based on the results, HiOxy steaks aged for 4 d give a superior red color for extended storage with few unfavorable effects. However, it is not advised to freeze deoxygenated steaks and expect a cherry red color through frozen storage.

The objective of this study was to identify and validate key wavelengths in the visible/near-infrared (VNIR) spectral region for beef tenderness assessment using hyperspectral images of beef carcasses acquired on-line in a commercial beef packing plant. A prototype on-line spectrograph hyperspectral imaging (HSI) system was developed and used to acquire images of exposed ribeye muscle on hanging beef carcasses (n = 274) at 2 days post-mortem. After image acquisition, a strip steak was cut from each carcass and vacuum packaged. After aging for 14 days, the steaks were cooked and Warner-Bratzler shear force values were collected as a measure of tenderness. Hyperspectral and multispectral image analysis approaches were conducted and compared to each other in terms of accuracy and speed of implementation. In the hyperspectral approach, principal component analysis (PCA) was conducted to reduce the spectral dimension of the hyperspectral images and create principal component (PC) bands. Image textural features were extracted from the PC bands and modeled to classify samples into two tenderness categories (tender or tough). In the multispectral approach, the loading vectors obtained from the PCA procedure were used to identify five key wavelengths (584, 619, 739, 832, and 950 nm). Image textural features were then extracted from these key wavelength images and modeled. In both approaches, the image features were extracted from the images acquired at 2 days post-mortem and used to forecast 14-day beef tenderness. Using a true validation procedure involving 101 beef samples, the hyperspectral approach had a tender certification accuracy, tender identification accuracy, tough identification accuracy, and accuracy index value of 86.7%, 65.8%, 63.6, and 66.8%, respectively. The corresponding metrics for the multispectral approach were 87.5%, 62%, 68.2%, and 67.8%, respectively. The tenderness prediction results for these two analysis methods were not considerably different; however, multispectral image analysis took far less time (about 8 s compared to 105 s on a quad-core computer with 8 GB of memory) to classify a beef sample into one of the two tenderness categories (tender or tough). Therefore, the multispectral approach shows great potential for real-time beef tenderness assessment in commercial beef packing plants.

Tenderness is the most critical sensory trait related to overall palatability of beef. Measurement of tenderness can be difficult. Tenderness gradients exist within and among muscles and the traditional tenderness measurement technique (shear force) has inherent variation itself. Beef tenderness prediction is further complicated because the tenderness of a sample changes with storage time and the extent of the change is different among animals and muscles. Some measurement approaches focus on physical structures while others address the biochemical factors influencing tenderness. The need exists for a tenderness-prediction technique that evaluates both structural and biochemical factors and that forecasts tenderness class after aging. Hyperspectral imaging has great promise for this application. This method obtains a spectral reflectance curve on every pixel in an image. Thus, hyperspectral imaging can address both the spatial as well as the spectral aspects of a sample. A hyperspectral scan may cover a broad portion of the spectrum, from the visible region, through the near infrared region, and beyond. Not surprisingly, there is a wealth of information contained within a hyperspectral scan. Before meaningful information can be extracted from an image, it is likely that pre-processing is required in both the spectral and spatial domains. Subsequently, complex statistical techniques are required in order to develop meaningful algorithms. One way to reduce the size of the image is by multispectral imaging, whereby a subset of wavelengths is measured. This approach allows focus on important areas of the reflectance curve and shows promise in classifying beef into tenderness categories. A classification approach requires different strategies than a regression approach. A successful multispectral-based beef tenderness classification has been developed.

Feeding wet distillers grains plus solubles (WDGS) increases polyunsaturated fatty acid (PUFA) levels in beef. It was hypothesised that WDGS in feedlot diets increases PUFA concentration in the sarcoplasmic reticulum (SR) membrane, thereby altering membrane integrity, resulting in more rapid intracellular calcium leakage and improved tenderness. The objective of this study was to evaluate this hypothesis. Ninety-six crossbred steers were fed either a corn-based diet with 0% WDGS or 50% WDGS. Fifteen strip loins per treatment were collected, fabricated into steaks, aged and placed under retail display conditions. Steaks were used to measure tenderness, proteolysis, free calcium concentrations, lipid oxidation, sarcomere length and SR membrane fatty acid, phospholipid lipid, neutral lipid and total lipid profiles. Compared with steaks from steers fed 0% WDGS, steaks from steers fed 50% WDGS were more tender (P < 0.05) and had greater (P < 0.05) free calcium concentrations early post-mortem. Feeding 50% WDGS also tended to increase (P < 0.10) total PUFA concentrations, decrease (P < 0.10) total phospholipid concentration and increase (P < 0.10) total neutral lipid concentration for SR membrane. Steaks from steers fed 0% WDGS had greater (P < 0.05) lipid oxidation (TBARS values) than steaks from steers fed 50% WDGS after extended aging. Although differences in tenderness between the two treatments were detected, there were no corresponding differences (P > 0.10) in sarcomere length or proteolysis. This study showed that feeding WDGS may increase tenderness, possibly by increasing free calcium in muscle early post-mortem. However, the true mechanism that contributes to these differences is still unclear.

Feeding wet distillers grains plus solubles (WDGS) in beef feedlot diets increases beef polyunsaturated fatty acids (PUFA) concentration and decreases shelf-life; whereas feeding antioxidants like vitamin E and Agrado-Plus (AG; an ethoxyquin and tert-Butylhydroquinone mixture) mitigates such effects. The objective of this study was to evaluate shelf-life of beef from steers supplemented with WDGS and different antioxidants. One hundred and sixty steers were finished on a corn-based diet with 0% WDGS or 30% WDGS and four antioxidant treatments (no supplementation; vitamin E only; AG only; vitamin E + AG). Ten strip loins from each treatment were collected, aged, cut into steaks, and placed under retail display (2 ± 2°C). During retail display, steaks were evaluated daily for objective colour and subjective discolouration. After retail display, steaks were used to measure lipid oxidation, muscle fatty acids, and vitamin E and ethoxyquin concentrations. Feeding 30% WDGS increased total PUFA in beef when compared with beef from steers fed 0% WDGS (P < 0.05). Supplementing vitamin E or vitamin E + AG was effective in decreasing myoglobin and lipid oxidation in steaks from steers fed 0% or 30% WDGS after retail display (P < 0.01). Supplementation of vitamin E or AG also increased (P < 0.01) muscle tissue vitamin E or ethoxyquin levels, respectively, compared with the diets without vitamin E or AG supplementation. The inclusion of 30% WDGS altered beef fatty acid profiles, but did not promote lipid and myoglobin oxidation compared with the 0% WDGS diet. Feeding vitamin E was effective, whereas supplementing AG had minor effects in decreasing myoglobin and lipid oxidation in steaks from both diet.

The influence of slaughter season and sex on intramuscular total lipids (ITL) neutral lipid (NL) and phospholipid (PL) compositions, cholesterol and α-tocopherol contents were evaluated in Biceps femoris (Bf), Longissimus dorsi (Ld) and Supraspinatus (Ss) muscles from 92 Barrosa-PDO (Protected Denomination of Origin) calves. ITL content in Bf muscle was affected by slaughter season and sex whereas NL content was only affected by slaughter season. Neither sex nor slaughter season influenced cholesterol and α-tocopherol contents in the muscles under study. Concerning NL composition, sex was an important source of variation on the proportions of total SFA and MUFA in all muscles. Irrespective of the considered muscle, males had higher total SFA but lower total MUFA and MUFA/SFA contents than females. Slaughter season influenced C18:2 cis-9 trans-11 (CLA) content in Bf (P

Loin steaks were removed from USDA Commercial (n=38) and Utility (n=42) beef carcasses to facilitate study of Fragmentation Index (PI). Tenderness was assessed by the Warner-Bratzler shear (WBS) and a trained, 8-member sensory panel. To determine the minimum time required to obtain the FI for fresh and frozen raw longissimus muscle, three drying times were studied (10 min, 40 min, and 22 hr). Simple correlation coefficients relating FI to WBS force value and sensory tenderness rating were: fresh muscle FI (10 min), 0.60 and -0.60; frozen muscle FI (40 min), 0.73 and -0.69, respectively. USDA grade factors and simultaneous consideration of all all measures of fragmentation accounted for 14.1 and 61.1%, respectively, of the observed variation in WBS force values. PI determined from frozen longissimus muscle accounted for 18.6-23.8s more of the observed variation in cooked meat tenderness than FT of fresh muscle. The best two-variable regression model accounted for 56.6% of the observed variation in WBS force value.

Effects of electrical stimulation on quality-indicating characteristics of beef were evaluated in two studies involving a total of 402 carcasses. Electrical stimulation (550 volts, 5 amps, 60 cycles per set) was administered shortly after the carcasses were split and consisted of 17 impulses of 1.8 set each with a 1.8 set interval between impulses. In Study 1, one side of each carcass (n=222) was electrically stimulated (ES) and the opposite side served as an untreated control (C). Both sides of each carcass were ribbed and evaluated at 24 hr postmortem. Study 2 included carcasses (n=180) in which (a) neither side was stimulated, (b) both sides were stimulated, or (c) one side was stimulated and the opposite side was not stimulated. Postmortem chilling time prior to ribbing also was varied to permit evaluations to be made of the effects of electrical stimulation on carcasses chilled for 24, 48, or 72 hr. In Study 1, ES sides were more desirable (P < 0.0001) than C sides in all quality-indicating characteristics (marbling, USDA quality grade, lean maturity, lean color, lean firmness, and incidence of “heat-ring”). In Study 2, optimum chilling time for maximizing marbling score and USDA quality grade was 48 hr for both ES and C sides. ES sides usually were more youthful (lean maturity) than C sides, especially at 24 hr postmortem. Control sides chilled for 48 hr had more marbling and higher USDA quality grades than did ES sides chilled for 24 hr. Nothing in the present study indicates that electrical stimulation results in a higher-than-justified quality grade.

The effects of lighting type on fresh pork color were studied by displaying chops under delux cool white (DCW), cool white, Surlyn® coated (CWSC), or warm white (WW) fluorescent or cool flood (CF) incandescent lights. Initial color desirability was assessed. Hunter colorimeter values and percentage myoglobin (Mb), oxymyoglobin (OMb) aand metmyoglobin (MMb) were determined over 5 days of display. Light types CF and DCW provided the most desirable color rendition. Chops displayed under CF lights became darker, had less percentage OMb and greater Mb, and likely had greater microbial growth than other chops due to an increase in chop temperature. It appears that CF and DCW lights provide the most desirable color and that precautions against temperature elevation are needed.

Beef carcasses (n = 65) were selected to range widely in marbling (moderately abundan: to practically devoid) and maturity (A, n = 25; B, n = 19; C, n = 6; D, n = 8; E, n = 7). Number, percent, area and mean diameter of β-red (βR), α-white (αW) and α-red (αR) muscle fibers were determined. Warner-Bratzler shear force values and taste panel tenderness ratings were also obtained. αW muscle fiber parameters were negatively correlated (P < 0.05) to marbling and tenderness ratings while αR and βR parameters were positively correlated (P < 0.05) to these quality attributes. The ratio of αW fiber area to βR and/or αR fiber area was correlated (P < 0.05) with marbling and tenderness. Regression analyses indicate that muscle fiber type composition is more highly related to marbling (marb) than it is to shear force value (SFV) or tenderness rating (TR) although all relationships were significant (P < 0.10). The relationship of these quality indicators to fiber type is greater within A maturity [marb, coefficient of determination (C.D.) = 65.09; SFV, C.D. = 65.09; SFV, C.D. = 28.85; TR, C.D. = 62.94] than for the entire population (murb, C.D. = 49.16; SFV, C.D. = 18.71; TR, C.D. = 30.47). It appears that the oxidative capacity of a muscle is related to marbling and tenderness and that muscle fiber type composition could possibly be used as a predictor of marbling potential.

Short loin steaks selected from beef carcasses representing wide ranges in USDA maturity score (A, B, C, and E) and marbling level (high=moderate0 0 to moderately abundant5 0, medium=slight6 7 to modest9 0 and low=practically devoid5 0 to slight3 3, were subjected to flavor profile analyses. Beef from E maturity carcasses had higher aroma and flavor amplitudes and a greater predominance of “grassy” flavors than did beef from carcasses of other maturity groups. “Astringent” aftertaste was common to most samples. Analyses obtained in our study agree with earlier flavor profile studies conducted on beef of various USDA quality grades. Flavor profiles were developed for steaks from the same carcasses that had provided steaks previously identified as “desirable” or “undesirable” in flavor by two separate panels using hedonic flavor rating scales. “Sweet” and “browned” were typical flavors of steaks previously classified as desirable in flavor, while “grassy” and “astringent” were frequently noted flavors of steaks previously classified as undesirable in flavor. Marbling and fat content were higher in steaks previously classified as desirable in flavor, than in steaks classified as undesirable in flavor.