Proteomics and metabolomics profiling of meat exudate to determine the impact of postmortem aging on oxidative stability of beef muscles.

The objective of this study was to characterize the major proteomes and metabolites in beef exudate and determine their relationship to color and oxidative quality of beef muscles. Beef loin (LD) and tenderloin (PM) muscles were cut into sections, individually vacuum-packaged, and aged for 9, 16 and 23 days at 2 °C. Following aging, beef exudates were collected and analyzed for both proteomics and metabolomics profiles. Proteome analysis indicated clustering by muscle types, while metabolomics profiling further clustered the samples based on the aging periods. The PM exudate had a greater concentration of oxidative enzymes, while the LD exudate contained more glycolytic enzymes. Greater lipid, nucleotide, carnitine and glucoside metabolites were observed in LD and 23d exudates. HSP70 and laminin proteins, together with glucosides metabolites, were correlated to muscle oxidative stability. The results indicated that meat exudate could be a viable analytical matrix to determine changes in quality attributes of meat with aging.

Beef quality, biochemical attributes, and descriptive sensory scores of gluteus medius, biceps femoris, and tensor fasciae latae muscles subjected to combined tumbling and postmortem aging.

This study assessed how fresh beef tumbling without brine inclusion combined with aging would affect quality, biochemical attributes, and descriptive sensory scores of sirloin muscles. Paired gluteus medius (GM), biceps femoris (BF), and tensor fasciae latae (TFL) muscles from beef carcasses (n = 16) at 5 days postmortem were assigned to 0 or 120 min of tumbling, after which sections were aged 0 or 10 days. Tumbled GM (p < 0.001) and TFL (p < 0.01) muscles had increased objective tenderness compared to respective controls. Greater cook and initial purge losses were induced in all muscles with tumbling (p < 0.05), while thawing loss and purge loss with aging were similar (p > 0.05). Fragmentation of myofibrils was increased with tumbling and aging main effects (p < 0.001), although degradation of troponin T and desmin were primarily affected by aging only. In general, neither tumbling nor aging affected properties of collagen. Trained panelists assessed muscles aged 10 days for descriptive sensory scores including tenderness (myofibrillar, connective tissue, and overall), flavor (beef flavor identity, bloody/serumy, fat-like, liver-like, oxidized, umami, metallic, and sour), and juiciness (overall). Tumbled GM had greater myofibrillar tenderness than the control group (p < 0.05). Most sensory scores were unaffected by tumbling; however, tumbling increased oxidized and liver-like flavors of GM and TFL, respectively, as well as decreased overall juiciness of BF (p < 0.05). These findings indicate tumbling combined with postmortem aging can improve tenderness of certain sirloin muscles like GM, although some impairments to flavor and juiciness could also occur. PRACTICAL APPLICATION: The findings of this study are applicable to the beef industry to develop postharvest strategies to ensure sufficient tenderization of fresh beef sirloin muscles is achieved. However, the effectiveness of this process would differ between individual cuts, and minimizing possible impairments to flavor and juiciness would be critical.

Characterizing the Flavor Precursors and Liberation Mechanisms of Various Dry-Aging Methods in Cull Beef Loins Using Metabolomics and Microbiome Approaches.

The objective of this study was to characterize and compare the dry-aging flavor precursors and their liberation mechanisms in beef aged with different methods. Thirteen paired loins were collected at 5 days postmortem, divided into four sections, and randomly assigned into four aging methods (wet-aging (WA), conventional dry-aging (DA), dry-aging in a water-permeable bag (DWA), and UV-light dry-aging (UDA)). All sections were aged for 28 days at 2 °C, 65% RH, and a 0.8 m/s airflow before trimming and sample collection for chemical, metabolomics, and microbiome analyses. Higher concentrations of free amino acids and reducing sugars were observed in all dry-aging samples (p < 0.05). Similarly, metabolomics revealed greater short-chain peptides in the dry-aged beef (p < 0.05). The DWA samples had an increase in polyunsaturated free fatty acids (C18:2trans, C18:3n3, C20:2, and C20:5; p < 0.05) along with higher volatile compound concentrations compared to other aging methods (aldehyde, nonanal, octanal, octanol, and carbon disulfide; p < 0.05). Microbiome profiling identified a clear separation in beta diversity between dry and wet aging methods. The Pseudomonas spp. are the most prominent bacterial species in dry-aged meat, potentially contributing to the greater accumulation of flavor precursor concentrations in addition to the dehydration process during the dry-aging. Minor microbial species involvement, such as Bacillus spp., could potentially liberate unique and potent flavor precursors.

Tumbling and subsequent aging improves tenderness of beef longissimus lumborum and semitendinosus steaks by disrupting myofibrillar structure and enhancing proteolysis.

Tenderness is an important sensory attribute to the overall eating experience of beef. Identifying novel methods to ensure consistent tenderness, especially in inherently tough cuts, is critical for the industry. This study investigated if tumbling without brine inclusion could be an effective method to improve the quality and palatability attributes of beef longissimus lumborum (LL) and semitendinosus (ST) steaks. Furthermore, interactions with postmortem aging were evaluated to determine how tumbling might affect protein degradation and muscle ultrastructure. At 5 d postmortem, pairs of LL and ST muscles from beef carcasses (n = 16) were bisected, vacuum packaged, and tumbled for 0, 40, 80, or 120 min. Sections were divided and subsequently aged an additional 0 or 10 d at 2 °C. Tumbling for any duration improved instrumental tenderness of LL (P < 0.001) but not ST (P > 0.05) steaks, regardless of aging time. Tumbling exacerbated moisture loss in both muscles shown by greater purge and cooking losses (P < 0.05). Myofibrillar fragmentation was induced through tumbling in both muscles (P < 0.001), which was supported by transmission electron microscopy images. Tumbling for 120 min followed by 10 d of aging resulted in less abundant intact troponin-T in both LL and ST (P < 0.05), as well as less intact desmin in ST (P < 0.05); however, calpain-1 autolysis was not affected by tumbling (P > 0.05). No effects of tumbling, aging, nor the interaction were found for the content and solubility of collagen (P > 0.05). Consumer panelists (n = 120/muscle) rated LL steaks tumbled for any duration higher for tenderness and overall liking compared to control steaks (P < 0.05). For ST, significant interactions were found for consumer liking of tenderness and juiciness. In general, tumbling without subsequent aging resulted in poorer juiciness than non-tumbled (P < 0.05), while at 10 d no differences in juiciness were found between treatments (P > 0.05). For ST steaks that were aged 10 d, 120 min of tumbling resulted in greater tenderness liking than non-tumbled steaks (P < 0.05). These results suggest that tumbling would result in myofibrillar fragmentation and may benefit the degradation of myofibrillar proteins; however, there would be negligible impacts on collagen. Accordingly, tumbling without brine inclusion alone may be sufficient to improve tenderness and overall liking of LL steaks, while combined tumbling with subsequent postmortem aging would be necessary to improve tenderness liking of ST.

Tenderness is a primary driver to the overall eating experience of beef. Postmortem aging is applied to improve beef tenderness through the activity of endogenous proteolytic enzymes; however, certain inherently tough cuts may not reach acceptable levels of tenderness through aging alone. This study investigated if tumbling in the absence of a brine solution, coupled with subsequent postmortem aging, would be an effective strategy to improve the quality and palatability attributes of fresh beef loin (longissimus lumborum; LL) and eye of round (semitendinosus; ST) steaks. Regardless of aging, tumbling for 40, 80, or 120 min improved instrumental tenderness of LL but not ST steaks. Consumer panelists rated tumbled LL steaks to be more tender with greater overall liking compared to those that were not tumbled. Tumbling alone was insufficient to affect consumer liking of tenderness of ST steaks, although tumbling combined with subsequent aging improved tenderness liking. The results supported that tumbling would physically disrupt and fragment the myofibrillar structure, which may aid in the degradation of myofibrillar proteins during postmortem aging.

Effect of Dry-Aging on Quality and Palatability Attributes and Flavor-Related Metabolites of Pork Loins.

This study evaluated the effect of dry-aging on quality, palatability, and flavor-related compounds of pork loins. Ten pork loins were obtained at 7 days postmortem, divided into three equal portions, randomly assigned into three different aging methods (wet-aging (W), conventional dry-aging (DA), and UV-light dry-aging (UDA)), and aged for 21 days at 2 °C, 70% RH, and 0.8 m/s airflow. The results showed similar instrumental tenderness values across all treatments (p > 0.05), while DA and UDA had a greater water-holding capacity than WA (p < 0.05). Both DA and UDA were observed to have comparable color stability to WA up to 5 days of retail display (p > 0.05). Greater lipid oxidation was measured in both DA and UDA at the end of display compared to WA (p < 0.05). The UV light minimized microorganisms concentration on both surface and lean portions of UDA compared to other treatments (p < 0.05). The consumer panel was not able to differentiate any sensory traits and overall likeness between the treatments (p > 0.05). Metabolomics analysis, however, identified more flavor-related compounds in dry-aged meat. These findings suggested that dry-aging can be used for pork loins for value-seeking consumers, as it has a potential to generate unique dry-aged flavor in meat with no adverse impacts on meat quality and microbiological attributes.

Elucidating mechanisms involved in flavor generation of dry-aged beef loins using metabolomics approach.

The present study was conducted to identify flavor-related chemical compounds and to elucidate beef flavor development in response to dry-aging. Paired grass-fed beef loins (n = 18) were obtained at 7 d postmortem, cut into two sections and assigned to 3 aging methods: conventional dry-aging (DA), vacuum packaged wet-aging (WA) and dry-aging in a bag (DW) for 28 days. Following aging, samples were analyzed for UPLC-MS metabolomics, volatile, fatty acid profiling, and consumer sensory comment analysis. Greater number of proteins and nucleotides derived metabolites were liberated in dry-aged samples compared to WA (P < 0.05). In particular, the liberation of gammaglutmayl peptides and glutamine metabolites through the glutathione metabolism were identified. While fatty acid profile was not affected by treatments (P > 0.05), higher concentrations of volatile compounds were found in the dry-aged (P < 0.05). Dry-aging process decreased the presence of terpenoid and steroid lipid group, which could possibly result in reducing undesirable flavor of grass-fed beef.

Evaluation of functional and chemical properties of crust from dry-aged beef loins as a novel food ingredient.

Efficacy of utilizing dry-aged beef crusts as a functional food ingredient was investigated. Paired beef M. longissimus lumborum (n = 13) were aged under various conditions (dry-aging, DA; dry-aging in water-permeable bag, DWA; dry-aging under UV light, UDA; wet-aging, WA; unaged-initial, INI) for 28 d. Crusts were collected and lyophilized to characterize functional and technological properties. Crusts from dry-aged samples (DA/DWA/UDA) had lower chroma values, higher lipid and protein oxidation extents than WA and INI (P < 0.05). However, crust from DA had higher antioxidant and emulsifying capacities compared to the others (P < 0.05). Adding 5% (w/w) crusts to beef patties resulted in equivalent textural properties and oxidative stability to the no-crust patties (P > 0.05). Trained sensory-panel found enhanced brown-roasted/grilled (P < 0.05) and umami flavors (P = 0.0512) in DA-patties compared to the others. Volatile analysis found decane in only DA-patties. The results indicate the potential feasibility of beef crust from dry-aged beef as a novel food ingredient.

Impacts of aging/freezing sequence on microstructure, protein degradation and physico-chemical properties of beef muscles.

The objective of this study was to determine the effect of aging/freezing sequence on meat quality, oxidative stability and biochemical attributes of beef muscles. At 3 days postmortem, Longissimus lumborum and Semitendinosus muscles were obtained from 10 beef carcasses, cut into 3 sections and vacuum-packaged. The sections were randomly assigned to aging/freezing treatments (aging only, aging then freezing/thawing, and freezing then thaw/aging). Freezing first then-thaw/aging showed more enlarged gaps between muscle fibers and widely opened extracellular drip channels, resulting in more purge/exudate loss compared to other treatments (P < .05). No differences in other meat quality attributes (e.g. shear force, color and lipid oxidative stability) were found between the aging/freezing sequence treatments (P > .05). A greater desmin degradation was observed in both freezing treatments, while troponin-T degradation was not affected (P > .05). The results suggest that freezing (and aging) itself would be the critical factor affecting those quality attributes of frozen/thawed meat rather than the sequence of aging/freezing.

Efficacy of Alkali-treated Sugarcane Fiber for Improving Physicochemical and Textural Properties of Meat Emulsions with Different Fat Levels.

The objective of this study was to evaluate the efficacy of alkaline-treated sugarcane bagasse fiber on physicochemical and textural properties of meat emulsion with different fat levels. Crude sugarcane bagasse fiber (CSF) was treated with calcium hydroxide (Ca(OH2)) to obtain alkaline-treated sugarcane bagasse fiber (ASF). The two types of sugarcane bagasse fiber (CSF and ASF) were incorporated at 2% levels in pork meat emulsions prepared with 5%, 10% and 20% fat levels. Alkaline-treatment markedly increased acid detergent fiber content (p=0.002), but significantly decreased protein, fat, ash and other carbohydrate contents. ASF exhibited significantly higher water-binding capacity, but lower oil-binding and emulsifying capacities than CSF. Meat emulsions formulated with 10% fat and 2% sugarcane bagasse fiber had equivalent cooking loss and textural properties to control meat emulsion (20% fat without sugarcane bagasse fiber). The two types of sugarcane bagasse fiber had similar impacts on proximate composition, cooking yield and texture of meat emulsion at the same fat level, respectively (p>0.05). Our results confirm that sugarcane bagasse fiber could be a functional food ingredient for improving physicochemical and textural properties of meat emulsion, at 2% addition level. Further, the altered functional properties of alkaline-treated sugarcane bagasse fiber had no impacts on physicochemical and textural properties of meat emulsions, regardless of fat level at 5%, 10% and 20%.

Understanding postmortem biochemical processes and post-harvest aging factors to develop novel smart-aging strategies.

Postmortem aging is a value-adding process and has been extensively practiced by the global meat industry for years. The rate and extent of aging impacts on meat quality characteristics are greatly affected by various biochemical/physiological changes occurring during the pre-rigor phase through post-rigor aging processes. This should also mean that the positive aging impacts on eating quality attributes can be further maximized through establishing specific post-harvest aging strategies. In this review, we propose the smart-aging concept, which is to develop innovative template strategies through identifying optimal aging regimes to maximize positive aging impacts on meat quality and value. The concept requires a good understanding of the physical, biochemical and post-harvest factors that affect the aging of beef. This knowledge coupled with the ability to non-invasively determine muscle composition early postmortem will create opportunities to tailor the process of muscle conversion to meat and the subsequent aging processes to deliver meat with consistent and improved eating qualities and functionality.

Effects of aging/freezing sequence and freezing rate on meat quality and oxidative stability of pork loins.

The aim of this study was to evaluate the effect of aging/freezing sequence and freezing rate on quality attributes and oxidative stability of frozen/thawed pork loins (M. longissimus lumborum, n = 6). Six treatments were prepared by combining 3 aging/freezing sequences (FT, freezing/thawing only; AFT, aging prior to freezing/thawing; and FTA, freezing/thawing and aging) with 2 freezing rates (slow- and fast-freezing). The lowest purge/thaw loss and drip loss were found for AFT, in which fast-freezing reduced total exudate loss (P < 0.05). Aging combination (AFT/FTA) decreased shear force of frozen/thawed pork loins, and FTA with slow-freezing caused the lowest shear force (P < 0.05). However, aging combination regardless of the sequence accelerated discoloration and lipid/protein oxidation during display (P < 0.05). This study suggests that aging prior to freezing coupled with fast-freezing could be an effective way to minimize quality defects of frozen/thawed only meat, particularly water-holding capacity and tenderness.

Effect of House Cricket (Acheta domesticus) Flour Addition on Physicochemical and Textural Properties of Meat Emulsion Under Various Formulations.

The objective of this study was to determine the effect of house cricket (Acheta domesticus) flour addition on physicochemical and textural properties of meat emulsion under various formulations. As an initial marker of functionality, protein solubility, water absorption, emulsifying capacity, and gel formation ability of house cricket flour were determined at pH (2 to 10) and NaCl concentrations (0 to 2.10 M). Control emulsion was formulated with 60% lean pork, 20% back fat, and 20% ice. Six treatment emulsions were prepared with replacement of lean pork and/or back fat portions with spray-dried house cricket flour at 5% and 10% levels, based on a total sample weight. The protein solubility of house cricket flour (67 g protein/100 g) was significantly altered depending upon pH (P < 0.0001) and NaCl concentration (P = 0.0421). Similar water absorption capacity, emulsifying capacity, and gel formation ability of house cricket flour were found between 0 and 2.10 M NaCl concentration (P > 0.05). The replacement of lean meat/fat portion with house cricket flour within 10% level could fortify protein and some micronutrients (phosphorus, potassium, and magnesium) in meat emulsion, without negative impacts on cooking yield and textural properties. Our results suggest that house cricket flour can be used as an effective nonmeat functional ingredient to manufacture emulsified meat products. PRACTICAL APPLICATION: To better utilize house cricket flour as a food ingredient in wide application, understanding its technological properties in various pH, and ionic strength conditions is a pivotal step. Protein solubility of house cricket flour would be considerably affected by the varying pH and NaCl concentrations of applied conventional foods. In the case of meat emulsion, within 10% lean meat and/or fat portions could be successfully substituted with house cricket flour without detectable adverse impacts on technological properties associated with cooking yield and instrumental analysis of texture. Thus, our findings suggest that house cricket flour possess the necessary physical properties to be used as an alternative nonmeat ingredient for incorporation within emulsified meat products, which could be further explored in subsequent sensory-based studies.

Rapid Discoloration of Aged Beef Muscles after Short-Term/Extreme Temperature Abuse during Retail Display.

The objective of this study was to evaluate the effects of a short-term/extreme temperature abuse (STA) on color characteristics and oxidative stability of aged beef muscles during simulated retail display. Two beef muscles (longissimus lumborum, LL and semitendinosus, ST) were aged for 7 (A7), 14 (A14), 21 (A21), and 28 d (A28), and further displayed at 2℃ for 7 d. The STA was induced by placing steak samples at 20℃ for 1 h on the 4th d of display. Instrumental and visual color evaluations, ferric ion reducing capacity (FRC) and 2-thiobarbituric acid reactive substances (TBARS) assay were performed. Initially, redness, yellowness and hue angle of all beef muscles were similar, regardless of aging time before display (p>0.05). An increase in postmortem aging time increased lipid oxidation and caused a rapid discoloration after STA during display (p<0.05). ST muscle was more sharply discolored and oxidized after STA, when compared to LL muscle (p<0.05). The FRC value of beef muscles was decreased after 7 d of display (p<0.05). The results from the current study indicate adverse impacts of postmortem aging on color and oxidative stabilities of beef muscles, particularly under temperature abusing conditions during retail display. Thus, developing a specific post-harvest strategy to control quality attributes in retail levels for different muscle types and aging conditions would be required.