Effects and mechanism of sub-freezing storage on water holding capacity and tenderness of beef

In order to explore the effect of sub-freezing storage on water holding capacity and tenderness of beef, four treatments were compared in this study: sub-freezing (-7 °C) fast sub-freezing (-38 °C until the core temperature achieved to -7 °C), superchilling (-1 °C) and fast frozen (-38 °C until the core temperature achieved to -18 °C) with the latter two treatments serving as the controls. The differences in muscle fiber structure, water distribution, protein oxidation and cytoskeletal protein degradation were studied. The results demonstrated that compared with other treatments, the fast sub-freezing treatment resulted in less structural damage to the muscle fibers and had better water holding capacity. Both sub-freezing and fast sub-freezing treatments inhibited protein oxidation compared with superchilling, but the former treatment's level of protein oxidation was higher than that in fast sub-freezing treatment during long-term storage (42 weeks). In addition, the structural proteins in the sub-freezing and fast sub-freezing treatments underwent faster degradation during long-term storage and therefore the meat was more tender compared with the fast frozen treatment. The results indicate that the fast sub-freezing treatment can be potentially applied in beef storage.

A current review of U.S. beef flavor I: Measuring beef flavor

Historically, consumer acceptance of beef was determined by tenderness. Developments in genetics and management over the last couple of decades have improved tenderness to the point that it is secondary to other factors in beef's taste. Flavor, however, is an extraordinarily complex taste attribute dependent on biological sensors in the mouth, sinus cavity, and jaws. The culinary industry has recently focused on innovative ways to give consumers new products satisfying their curiosity about different foods, especially proteins. Competition from plant-based, cell-based, and even other animal-based proteins provides diversity in consumers' ability to select a protein that satisfies their desire to include unique products in their diet. Consequently, the beef industry has focused on flavor for the last 10 to 15 years to determine whether it can provide the guardrails for beef consumption in the future. The U.S. beef industry formed a Flavor Working Group in 2012 composed of the authors listed here to investigate new and innovative ways to manage and measure beef flavor. The results of this working group have resulted in dozens of papers, presentations, abstracts, and symposia. The objective of this manuscript is to summarize the research developed by this working group and by others worldwide that have investigated methodologies that measure beef flavor. This paper will describe the strengths of the research in beef flavor measurement and point out future needs that might be identified as technology advances.

Influence of aging temperature and duration on spoilage organism growth, proteolytic activity, and related chemical changes in vacuum-packaged beef longissimus

Each carcass was assigned to a storage temperature (-2, 0, 4℃). Strip loins were portioned into half loins and assigned to an aging duration (14, 28, 42, 56 d) and vacuum packaged. Loins were aged in commercial upright refrigerators. At each aging interval, loin portion packages were aseptically opened and loins were surface swabbed for microbial analysis before fabrication into 2.54 cm strip steaks. Steaks assigned to slice shear force (SSF) were cooked to 71℃. A raw steak was used to track proteolytic activity, free amino acid content, and volatile compounds. Two-way interactions were observed for all spoilage organisms (P < 0.001). Aging for 42 and 56 d at -2℃ produced lower microbial counts compared to 4℃ (P < 0.05).  Loins aged for 14 d at 4℃ had increased desmin and troponin-T degradation compared to aging for 14 at -2 and 0℃ (P < 0.05). Loins aged in 4These data indicate aging at 4℃ increases the rate of proteolysis and subsequent tenderness development and flavor precursor accumulation. However, extended aging at 4℃ resulted in increased microbial counts. Many traits peaked at 42 d of aging.

Effect of postmortem tenderization strategies (pretumbling, blade tenderization, moisture enhancement) on processing yield parameters and eating quality of selected hip and loin muscles from youthful and mature beef carcasses

Several muscles from mature beef carcasses have been identified as failing to provide adequate tenderness required for a satisfactory consumer eating experience. Postmortem processing strategies can help improve the tenderness and subsequent eating quality of mature beef muscles. The current study was undertaken to investigate the impact of processing strategies (blade tenderization [BT], pretumbling [PT], and moisture enhancement [ME]), alone and in combination, on processing yield and eating quality-related parameters of selected loin and hip muscles (gluteus medius [GM], longissimus lumborum [LL], semimembranosus [SM], and biceps femoris [BF]) from youthful and mature beef cattle. Results indicate that muscles from mature beef were inherently less tender (P < 0.05), but some tenderization procedures produced meat that was similar in tenderness to that of youthful cattle. Of the different tenderization strategies evaluated, BT followed by ME (injection of a salt/phosphate solution) was the most effective strategy for improving (P < 0.05) tenderness of tougher muscle cuts such as BF and SM. Moisture enhancement alone improved tenderness (P < 0.05) and juiciness (P < 0.01) of SM, GM and LL, but with the exception of samples tenderized prior to injection, was not effective (P > 0.05) in BF muscles. No additional tenderization of GM and LL samples was observed (P > 0.05) by combining PT or BT with ME. Combining PT or BT with ME; however, was effective (P < 0.05) to control the increased purge loss observed following ME treatment in SM and LL muscles. Pretumbling as a single treatment was ineffective (P > 0.05) in all of the muscles, and only treatments that included BT were sufficient to effect an increase (P < 0.05) in tenderness of BF.

Extended Aging and Marbling Class Effects on Color Stability of Beef Longissimus lumborum, Gluteus medius, and Biceps femoris Steaks

Postmortem aging improves palatability of various muscles, especially those from lower quality grades. This study evaluated postmortem aging and marbling class effects on the color stability of longissimus lumborum, gluteus medius, and biceps femoris steaks. Carcasses were selected at grading to have Lower Small (Small00 to Small50; n = 50) or Upper Slight (Slight50 to Slight90; n = 50) marbling scores. Strip loin and top sirloin subprimals from each carcass side were assigned to aging treatments (14, 21, 28, or 35 d) in an incomplete block arrangement. After aging, subprimals were cut into longissimus lumborum, gluteus medius, and biceps femoris steaks, respectively. Steaks were placed in a simulated retail display for 11 d. Changes in redness (a* and hue angle) were much slower and less extensive (P &lt; 0.001) in longissimus lumborum steaks than in gluteus medius steaks, which had slightly slower and less extensive (P &lt; 0.01) redness changes than biceps femoris. Increasing aging time increased (P &lt; 0.001) the rate and extent of overall color change (ΔE) during simulated retail display. Steaks from Lower Small carcasses had higher (P &lt; 0.01) L* values than steaks from Upper Slight carcasses at 14, 28, and 35 d postmortem. In steaks from Upper Slight carcasses, L* values were lower (P &lt; 0.01) in steaks aged for 28 d compared to other aging times. In steaks from Lower Small carcasses, L* values were highest (P &lt; 0.001) when aged for 14 d. Increased aging time generally decreased (P &lt; 0.05) a*, b*, and chroma values. However, within each aging time, only b* values of steaks aged for 35 d differed (P = 0.01) with regard to marbling class. Results indicate that increasing aging time decreased color life of beef muscles, and that marbling class had minimal impact on lean color stability.

Effects backgrounding-finishing programs of different age/weight at harvest of feedlot steers

Four ages at harvest (HA: A15, A18, A24 and A30 for 15, 18, 24 and 30 months, respectively) were compared in performance, carcass and meat traits of feedlot finished steers over a 123-day period. Three meat aging periods (postmortem days: 2, 7 and 14) were imposed on a longissimus thoracis muscle (LM) section of each left carcass. Feed efficiency (FE) was greater (P ≤ 0.02) for A15 and A18. Treatment A30 had the lowest FE (P ≤ 0.02). The LM area was largest for A30, but no different (P = 0.15) from A24. Intramuscular fat was lowest (P < 0.01) for A15. No differences were detected (P ≥ 0.11) among the A18, A24 and A30. Treatment A30 had the highest rib fat thickness (P ≤ 0.02) and WBsf values. No differences were detected (P ≥ 0.25) in WBSf between A15, A18 and A24 after any aging period. Results suggested A24 as a threshold for carcass and meat traits.

Postmortem Aging Time and Marbling Class Effects on Flavor of Three Muscles From Beef Top Loin and Top Sirloin Subprimals

This study evaluated postmortem aging time and marbling class effects on flavor attributes of longissimus lumborum, gluteus medius, and biceps femoris steaks. Carcasses selected to have Lower Small (Small00 to Small49; n = 50) or Upper Slight (Slight50 to Slight99; n = 50) marbling were assigned to aging treatments (14, 21, 28, or 35 d) in an incomplete block arrangement. A trained sensory panel evaluated longissimus lumborum, gluteus medius, and biceps femoris steaks for tenderness, juiciness, and 31 flavor notes. Tenderness increases with aging time were linear (P &lt; 0.001) in longissimus lumborum and gluteus medius steaks and quadratic (P = 0.001) in biceps femoris steaks. Aging response of rancid flavor in longissimus lumborum steaks was cubic (P = 0.01), whereas the aging response of bloody/serumy flavor in biceps femoris steaks was quadratic (P = 0.03). Compared with Upper Slight marbling, carcasses with Lower Small marbling produced longissimus lumborum steaks with greater (P &lt; 0.01) beef flavor and lesser (P = 0.001) bitter flavor, gluteus medius steaks with greater (P = 0.05) brown/roasted flavor, and biceps femoris steaks with greater (P = 0.02) fat-like flavor, although differences were small. Principal component analysis indicated that bloody/serumy, sour, metallic, and bitter flavor attributes were the strongest contributors to a factor explaining 38% of longissimus lumborum flavor variation. Barnyard, bitter, sour, rancid, and bloody/serumy were the greatest contributors to a principal component explaining 41% of gluteus medius flavor. Barnyard, rancid, sour, bloody/serumy, and bitter were contributors to a component explaining 63% of biceps femoris sirloin cap flavor variance. Sample score plots indicated that neither aging time nor marbling class was associated with principal components and identified production lot as contributing to principal components explaining flavor variation in all 3 muscles. Results indicate that, in strip loin and top sirloin subprimals from carcasses with Upper Slight and Lower Small marbling scores, aging time and marbling class had little impact on beef flavor. Thus, increased aging times could be used to enhance tenderness with no adverse effects on other important palatability attributes.

Flavor, Tenderness, and Related Chemical Changes of Aged Beef Strip Loins

Varying aging times and methods were evaluated for their effect on flavor, tenderness, and related changes involatile compounds and flavor precursors. Strip loin sections from USDA Choice beef carcasses (n = 38) were randomly assigned to treatments: (1) 3 d wet-aged, (2) 14 d wet-aged, (3) 28 d wet-aged, (4) 35 d wet-aged, (5) 49 d wet-aged, (6) 63 d wet-aged, (7) 21 d dry-aged, and (8) 14 d wet-aged followed by 21 d dry-aged. Samples were analyzed for trained sensory attributes, shear force, volatile compounds, and flavor precursors (fatty acids, free amino acids, and sugars). Discriminant function analysis was used to identify sensory attributes contributing the greatest to treatment differences. Flavor notes were not differentiated in beef aged up to 35 d, regardless of aging method. A shift in flavor occurred between 35 d and 49 d of wet-aging time that was characterized by more intense sour and musty/earthy notes. Both shear force assessment and trained panelists agreed that tenderness was not affected (P &gt; 0.05) by additional aging beyond 28 d. Volatile compound production and liberation of amino acids and sugars increased (P &lt; 0.01) during the progression of aging time, with no change (P &gt; 0.05) in fatty acid composition, which may be a result of metabolic processes like microbial metabolism. Chemical properties shared strong positive relationships (r &gt; 0.50, P &lt; 0.001) with sour, musty/earthy, and overall tenderness. These results substantiate the deteriorative effect of extended aging times of 49 d or greater on flavor of beef strip loins without tenderness improvement.

Palatability assessments of beef strip loin steaks portioned by weight or by thickness sourced from various carcass weight/ribeye area size combinations

Beef carcasses (n = 90; U.S. Choice) met a 3 ribeye area (REA - Small, Medium, Large) × 3 carcass weight (CW - Light, Intermediate, Heavy) scheme to assess palatability on steaks cut by portion thickness (PT- 3.18 cm) and weight (PW -340 g). Significant interactions revealed trends for steaks from the Small REA, regardless of CW, to have among the lowest shear-force values. For PT steaks, significant interaction for overall liking revealed no differences for Small and Medium REA across all CW categories, but steaks from Large REA from Light CW differed (P < 0.05) from the other two CW categories. For PT steaks, overall liking and tenderness liking scores were higher (P < 0.05) for Small REA compared to other categories, whereas CW did not influence any palatability trait. REA and CW do impact beef steak palatability, though steaks from all combinations were "very tender" and highly acceptable from a palatability standpoint.

Temperature-time combination effects on aged beef volatile profiles and their relationship to sensory attributes

Beef ageing (in vacuo) for tenderisation and flavour development may be accelerated by favourable temperature-time combinations (TTCs), however the effect of such manipulations on volatile organic compounds (VOCs) that are generated during cooking, is unknown. We compared VOCs from grilled beef longissimus lumborum muscle samples which had been subjected to different TTCs. The TTCs consisted of combinations of temperatures (~ 3, 5, or 7 °C) and ageing time periods (6, 8, 10 or 12 d); as well as control samples, which were held at 0-2 °C for a total of 14 d. Sensory quality attributes of these same samples were measured by untrained consumer panellists. Generally, it was found that TTCs had negligible effects on grilled beef VOCs and were comparable to controls. Furthermore, many VOCs were significantly related to flavour intensity, flavour liking and overall liking. These findings support the use of TTCs as a viable means to accelerate the rate of beef ageing without compromising quality.

Moisture content, fatty acid profile and oxidative traits of aged beef subjected to different temperature-time combinations

Temperature-time combinations (TTC) effects on beef fatty acid (FA) composition, moisture content and oxidative traits were investigated. TTC were designed so temperatures were constant over each time period, and there was at most one variation in temperature within a sample's combined (total) time period. Therefore, three temperatures (~ 3, 5 and 7 °C) and five time periods (6, 8, 10 and 12 d) resulted in 72 different TTC, which were compared to control samples held for 14 d at ~ 1 °C. It was found that moisture losses increased as TTC temperature and time periods increased. There were negligible effects of TTC on FA composition. Sample TBARS and vitamin E content did not respond to TTC. A positive relationship between beef vitamin E and long chain polyunsaturated FA contents was observed. We concluded that TTC could be applied to accelerate the rate of ageing for beef and achieve comparable yield, oxidative and FA characteristics compared to conventional ageing approaches.

Point of purchase fatty acid profile, oxidative status and quality of vacuum-packaged grass fed Australian beef held chilled for up to 12 weeks

We investigated the fatty acid (FA) composition, oxidative biomarkers and quality traits of chilled beef. Specifically, striploin portions were held in vacuo and chilled (~ 1.5 °C) for up to 12 weeks, and analysed dependent on their assigned chilled storage period (0, 2, 5, 8, 10 and 12 weeks). There were no practical effects observed on beef FA composition as a result of chilled storage - including several polyunsaturated FA (PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Intramuscular fat content was found to have a covariate effect, but only for saturated FA and monounsaturated FA. Vitamin E and thiobarbituric acid reactive substances were unchanged. Furthermore, improvements to shear force and particle size were evident at 2 weeks and thereafter, no further variation was evident. These findings suggest that beef produced to be healthier based on the EPA, DHA and PUFA content will remain so, for up to 12 weeks. Likewise, beef quality will be preserved across this same period.

Metabolomic Investigation of Tenderness and Aging Response in Beef Longissimus Steaks

A study was conducted to identify molecular changes reflective of beef tenderness variation and tenderization during postmortem aging. Carcasses (U.S. Select) were selected to represent extremes in tenderness (n = 20; 10 per class). Two pairs of adjacent longissimus lumborum steaks from each strip loin were blocked by location and assigned to each aging time (2, 7, 14, or 28 d postmortem). One steak from each pair was designated for slice shear force determination and the other was used for sarcomere length, western blotting for desmin, and non-targeted LC- and GC–MS metabolite profiling. Tough steaks had higher (P &lt; 0.001) slice shear force values than tender steaks, and increasing aging time decreased (P &lt; 0.001) slice shear force values. Tender steaks had a greater (P &lt; 10–4) proportion of desmin degraded than tough steaks, and increasing aging time increased (P &lt; 10–22) desmin degradation in steaks from both classes. From 2,562 profiled metabolites, 102 metabolites were included in the final analysis after statistical screening. Twenty-eight metabolites could be annotated and loosely categorized into amino acids/peptides (n = 16), metabolism intermediates (n = 7), glycosides (n = 4), and fatty acids and phospholipids (n = 3). Amino acids were primarily associated with desmin degradation. Increased glucose levels were strongly associated to the tender classification and moderately associated to increased proteolysis, while increased glucose-6-phosphate was strongly related to the tender class but was related to decreased proteolysis. Increased malic acid was strongly associated to the tough classification, increased slice shear force, and decreased proteolysis. Increased levels of 3-phosphoglyceric acid and glycerol-3-phosphate was moderately associated with increased slice shear force and decreased proteolysis. These data indicate that accumulation of amino acids during aging is strongly related to postmortem proteolysis and may provide evidence of the fate of proteins degraded postmortem. Measures of glucose, glucose-6-phosphate, and malic acid concentrations may provide a metabolic fingerprint indicative of tenderness differences in beef longissimus.

Consumer and Warner-Bratzler Shear Evaluations of Steaks from Blade Tenderized, Aged, or Frozen Sirloin Subprimals

Paired USDA Choice top sirloin butts (n = 60) were divided equally across 3 trials: 1) blade tenderized (BT) versus non-blade tenderized (NBT), 2) refrigerated versus frozen aging/storage, and 3) 14-d versus 35-d refrigerated aging. Steaks from subprimals were evaluated using Warner-Bratzler Shear (WBS) force testing and consumer sensory evaluation. Consumers found BT steaks to be more tender and palatable compared to NBT steaks (P < 0.05), even though WBS values did not differ. Steaks from refrigerated versus frozen and 14- versus 35-d age treatments did not differ (P > 0.05) in consumer sensory ratings or WBS values. When compared to refrigerated, frozen storage of product did not affect consumer sensory ratings. Lack of differences between 14- and 35-d aging treatments indicated that the top sirloin butt did not require extended-aging periods to increase tenderness. Blade tenderization remains important for the top sirloin; however, purveyors may have options in postmortem aging and frozen storage of product without sacrificing quality.

National Beef Tenderness Survey—2015: Palatability and Shear Force Assessments of Retail and Foodservice Beef

Beef retail steaks from establishments across 11 US cities and beef foodservice steaks from establishments in 6 US cities were evaluated using Warner-Bratzler shear (WBS) force and consumer sensory panels. The average post-fabrication aging time of steaks at retail establishments was 25.9 d with a range of 6 to 102 d, and those from foodservice establishments averaged 31.5 d with a range of 3 to 91 d. The retail steaks with the lowest WBS value (P < 0.05) was the boneless top loin, compared to the top round steaks, which had the higher (P < 0.05) average WBS value. For the foodservice sector, top loin and ribeye steaks had the lowest (P < 0.05) WBS values, whereas the top sirloin represented the highest (P < 0.05) WBS values. The top blade retail steaks received among the highest consumer ratings (P < 0.05), whereas the top round and bottom round steaks received among the lowest (P < 0.05) consumer ratings for overall liking, tenderness liking, tenderness level, flavor liking, and juiciness liking. For the foodservice sector, the ribeye and top loin steaks were rated higher (P < 0.05) than top sirloin steaks for all consumer rating categories. The WBS values and sensory ratings were comparable to previous surveys, indicating no substantial changes in tenderness. Additional emphasis in improving the tenderness of top and bottom round steaks is necessary to increase consumer acceptability of these cuts.

Antimicrobial interventions for O157:H7 and non-O157 Shiga toxin-producing Escherichia coli on beef subprimal and mechanically tenderized steaks

Non-O157 Shiga toxin-producing Escherichia coli (STEC) is an emerging risk for food safety. Although numerous postharvest antimicrobial interventions have been effectively used to control E. coli O157:H7 during beef harvesting, research regarding their effectiveness against non-O157 STEC is scarce. The objectives of this study were (i) to evaluate effects of the spray treatments-ambient water, 5% lactic acid (LA), 200 ppm of hypobromous acid (HA), and 200 ppm of peroxyacetic acid (PA)-on the reduction of O157:H7 or non-O157 STEC (O26, O103, O111, and O145) with high (10(6) log CFU/50 cm(2)) or low (10(2) log CFU/50 cm(2)) levels on beef subprimals after vacuum storage for 14 days and (ii) to evaluate the association of the antimicrobial treatments and cooking (50 or 70°C) on the reduction of the pathogens in blade-tenderized steaks. The treatment effects were only observed (P = 0.012) on samples taken immediately after spray intervention treatment following inoculation with a high level of O157:H7. The LA and PA treatments significantly reduced low-inoculated non-O157 STEC after spray intervention; further, the LA and HA treatments resulted in significant reductions of non-O157 STEC on the low-inoculated samples after storage. Although cooking effectively reduced the detection of pathogens in internal steak samples, internalized E. coli O157:H7 and non-O157 STEC were able to survive in steaks cooked to a medium degree of doneness (70°C). This study indicated that the reduction on surface populations was not sufficient enough to eliminate the pathogen's detection following vacuum storage, mechanical tenderization, and cooking. Nevertheless, the findings of this study emphasize the necessity for a multihurdle approach and further investigations of factors that may influence thermal tolerance of internalized pathogenic STEC.