The effects of electrical stimulation and ageing on beef tenderness

Seventeen beef carcasses from cattle with a range of breeds, ages and body conditions were used in this trial. The four treatments applied to each carcass were control (C), electrical stimulation (ES), ageing for 28 days (A) and electrical stimulation plus ageing for 28 days (ES + A). Post-mortem muscle pH was measured at 0, 0·5, 4 and 24h post-stimulation. Significantly lower muscle pH values (P < 0·01) were achieved by the stimulated carcass side sompared to the unstimulated side at 0·5 (pH 6·47 vs. 6·91) and 4 h (pH 5·96 vs. 6·44) post-stimulation.

Warner-Bratzler shear and taste panel methods were used to assess the tenderness of Longissimus dorsi muscle samples from each of the four treatments. The ES, A and ES + A treatments were significantly more tender (P < 0·01) than the control treatment. The ES and the A treatments resulted in a similar improvement in tenderness compared to the control. The ES + A treatment was significantly more tender (P < 0·01) than the ES treatment alone, but there was no significant difference in tenderness between the A and the ES + A treatments.     

Post-mortem electrical stimulation and high temperature ageing of hot-deboned beef

The effects of electrical stimulation (80-100 V, 15 pps) of hot-deboned, bovine Longissimus dorsi muscles, followed by ageing at 30° or 40°Cfor 5, 7 or 10 h, on the solubility of sarcoplasmic and myofibrillar proteins, soluble non-protein nitrogen, and on the water-holding capacity, colour, tenderness and microbiological status of the meat, was assessed. Comparisons were made with the same traits measured on non-stimulated controls (average muscle temperature, 5°C), which were cold-deboned post rigor, and with hot-deboned, electrically stimulated muscles, subsequently held at 2°C. For each treatment and its corresponding control, six muscles each were studied. Such electrical stimulation produced a typical acceleration of pH fall post mortem and enhanced ageing changes at both 30°C and 40°C. It significantly increased tenderness over non-stimulated, cold-deboned controls. The higher temperature of ageing, however, was significantly associated with adverse colour development, loss of water-holding capacity and increased microbial growth. Electrical stimulation alone would not obviate the need for immediate refrigeration in hot-deboning operations with ambient temperatures of ～ 40°C.     

Microbiological and sensory characteristics of beef loin steaks: Role of subcutaneous fat

Beef loin steaks with the subcutaneous fat attached, without subcutaneous fat and the subcutaneous fat that was removed from steaks were packaged and stored at 4°C ± 1°C in polyvinyl chloride (PVC) film for 0–6 days and in high-oxygen barrier (HOB) film for 0–28 days. Aerobic plate counts (APCs) of subcutaneous fat of intact steaks and of subcutaneous fat that was packaged and stored separately in PVC and HOB films were greater (P < 0·05) than those of comparable lean samples. The APCs of lean of steaks without subcutaneous fat that were packaged and stored in HOB film were lower (P < 0·05) than those of the lean of intact steaks. APCs of the lean of these two types of steaks packaged and stored in PVC film did not differ (P > 0·05). Mean surface discoloration and mean overall appearance scores of intact steaks packaged and stored in HOB film were greater than those of steaks packaged and stored without subcutaneous fat; differences were significant (P < 0·05) after 21 and 14 days, respectively. This difference in surface discoloration was attributed to metmyoglobin formation due to possibly higher levels of oxygen remaining in the packages of steaks without subcutaneous fat than in packages containing steaks with the fat attached.     

Microbiological and sensory characteristics of beef loin steaks: Role of intramuscular fat

Beef loin steaks of different grades (Prime, Choice and Good) were packaged and stored in polyvinyl chloride (PVC) film for 0-6 days and in high-oxygen barrier (HOB) film for 0-28 days. Grade had no significant effect (P > 0·05) on the aerobic plate count and did not result in major differences in the distribution of types in the microflora of steaks. Of the sensory characteristics examined, mean surface discoloration and mean overall appearance scores of Prime and Choice steaks packaged and stored in HOB film often were higher (P < 0·05) than those of Good steaks. Differences in metmyoglobin formation among steaks from the three grades were attributed to differences in the inherent characteristics of the muscles; muscle fibers from Prime and Choice samples were probably more red (as evidenced by greater marbling ability), while muscle fibers of Good samples were probably more white (as evidenced by lesser marbling ability). Red muscles have greater cytochrome activity, which will help reduce metmyoglobin to myoglobin in the absence of oxygen.     

Proximate composition and energy content of beef steaks as influenced by USDA quality grade and degree of doneness

This study evaluated the influence of various degrees of doneness on proximate composition and energy content of beef. Ten steaks were obtained from each of five USDA Prime, five USDA Choice, and five USDA Select strip loins and assigned to one of five degree of doneness treatments (two sets of treatments per strip loin): raw, medium rare (63 °C), medium (71 °C), well done (77 °C), and very well done (82 °C). After cooking, steaks were dissected into separable tissue components consisting of lean, fat, and refuse. Lean tissue was used to obtain proximate analyses of protein, moisture, fat, and ash. Degree of doneness did influence (P<0.05) the nutrient composition of beef steaks. As the degree of doneness increased, percent fat and protein increased, while percent moisture decreased. Cooking steaks to a higher degree of doneness resulted in a higher caloric value when reported per 100g basis.     

Relationships of slice shear force and Warner-Bratzler shear force of beef strip loin steaks as related to the tenderness gradient of the strip loin

This study was conducted to investigate the effects of steak location within a strip loin and USDA quality grade on muscle fiber angle, slice shear force (SSF), and Warner-Bratzler shear force (WBSF) and to determine the relationship between SSF and WBSF. Steak location influenced both SSF and WBSF values, as steaks from the anterior portion were typically tenderer than steaks from the posterior end. Although there is some discrepancy between the two shear force methods, both agree that at least the first 5 anterior-most steaks are comparable. Muscle fiber angle was affected by steak position within the strip loin, as the fiber angle shifted between steaks 7 and 8. Quality grade had a significant effect on beef tenderness for both SSF and WBSF. Finally, there was a strong relationship between lateral SSF and average WBSF (r = 0.64), which are currently the most commonly used measurements for instrumental tenderness.     

Effects of chilling rate and spray-chilling on weight loss and tenderness in beef strip loin steaks

We evaluated the effects of chilling rate and the use of a spray-chilling system on the weight loss by evaporation on carcasses. We also evaluated the effects on meat purge in vacuum package, cooking losses, and on parameters related to the tenderness of strip loin steaks (M. longissimus lumborum). Forty non-castrated males of approximately 12 months old, finished in feed-lot were harvested in 16 Montana cattle (a composite breed), and 24 Simmental × Nellore crossbred cattle. After bleeding, the bodies were electrically stimulated and assigned to one of the four treatments: conventional air-chilling (CAC), conventional spray-chilling (CSC), slow air-chilling (SAC), and slow spray-chilling (SSC). Strip loin steaks (M. longissimus lumborum) of approximately 2.5 cm thick were removed, vacuum packed and aged for 7, 14, 30 or 60 days. Samples were analyzed for sarcomere length, myofibrillar fragmentation index, Warner–Bratzler shear force, and weight losses by purge and cooking. Spraying was efficient in reducing weight loss by evaporation (P < 0.05). Effects of treatments and aging period on purge losses were observed, where samples from sprayed carcasses or aged cuts showed higher losses. Cooking losses were not affected either by spraying or aging. The slow chilling, with or without spraying, was more efficient in producing strip loin steaks with lower average shear force and longer sarcomere. The myofibrillar fragmentation index increased with aging time, but was not affected by carcasses spraying.     

Pulsed UV-C radiation of beef loin steaks: Effects on microbial inactivation,quality attributes and volatile compounds

The aim of this study was to investigate the effect of pulsed light treatment at fluences of 0.525, 1.05, 2.1 and 4.2 J/cm² on the chemical composition, microbiological quality and volatile compounds of beef loin steaks. Pulsed light treatment did not affect total moisture, total protein, total lipid and ash content of samples significantly (P > 0.05). The a* and b* values of the pulsed light treated samples significantly decreased compared to control samples with maximum difference of 2.11 and 1.33 unit, respectively (P < 0.05). The highest reduction (3.49 ± 0.67 log CFU/g) in total aerobic mesophilic bacterial counts (compared to naturally occuring microbiota in control group) was achieved for samples treated with 4.2 J/cm² of UV-C fluence level. A total of 14 volatiles, mainly aldehydes, alcohols, ketones and terpen compounds were identified in the raw samples and pulsed light treatment caused an increase in the amounts of some volatile compounds, including hexanal (from 33.41 μg/kg to 69.67 μg/kg), 2-heptenal (from 0.60 μg/kg to 1.52 μg/kg), 2-octenal (from 0.39 μg/kg to 1.58 μg/kg), 2,4-nonadienal (from 0.05 μg/kg to 0.24 μg/kg), 2,4-decadienal (from 0.04 μg/kg to 0.26 μg/kg), 3-octen-2-one (from 0.37 μg/kg to 2.53 μg/kg), limonene (from 2.06 μg/kg to 18.42 μg/kg). Otherwise, pulsed light decreased the levels of some compounds coming from microbial metabolism such as 1-heptanol (from 0.57 μg/kg to 0.39 μg/kg), 1-octen-3-ol (from 1.83 μg/kg to 1.12 μg/kg), 2-octen-1-ol (from 0.28 μg/kg to 0.09 μg/kg). In conclusion, pulsed light treatment can enhance the microbial safety of meat and has potential for use in the meat industry.     

Water characteristics in cooked beef as influenced by ageing and high-pressure treatment-an NMR micro imaging study

The water characteristics in cooked pressure-heat treated (45?°C for 45 min prior to pressurisation at 150 MPa for 30 min) and non-pressurised, cooked (control) samples of beef Longissimus aged for 1, 3, 8 or 16 days were studied by nuclear magnetic resonance microscopy. A multi-echo sequence was used to obtain T2 images, and independent of ageing period, the T2 values were found to be lower in pressure-heat treated meat revealing alterations in water characteristics of pressure-treated, cooked meat compared with cooked meat. With increasing ageing duration, the T2 values in both pressure-treated, cooked and cooked meat decreased indicating that the water became more tightly trapped in the protein network. In addition, independent of length of ageing period the relationship between cooking loss in the cooked meat and transverse relaxation differed between non-pressurised and pressure-treated meat, which reveals that the mechanisms changing the water properties in beef during ageing are different from those occuring during pressure-heat treatment of meat.     

Effect of rapid thawing on the meat quality attributes of USDA select beef strip loin steaks

The objective was to determine the meat quality effects of rapidly thawing beef steaks in a water bath. Frozen beef strip loins (n = 24) were cut into steaks sequentially from the rib end and identified by anatomical location (anterior, middle, posterior) within the loin. Within location, steaks were randomly assigned to conventional (C; 18 to 20 h, 4 °C) or rapid thawing methods. Rapid thawing methods, fast (20 min, 20 °C) or very fast (11 min, 39 °C), were conducted in a circulating water bath. The physical, thawing, cooking, color, and texture characteristics of each steak were recorded. Data were analyzed as a randomized complete block design with a 3 thawing treatments × 3 locations factorial analysis with loin as a block. No location by thawing method interaction was detected (P > 0.05) for the measured variables. Compared to C steaks, rapidly thawed steaks exhibited lower thaw drip loss (P < 0.001) and higher a* values (P < 0.001). Thawing treatment did not influence L*, b*, cook yield, or shear force. Steaks from the posterior end had higher (P < 0.001) surface to volume ratios that may have contributed to the higher thaw loss (P < 0.01), longer cooking time (P < 0.001), lower cooking yield (P < 0.001), and higher shear force (P < 0.02) compared to steaks from the anterior and middle portions of the loins. These data indicate that beef steaks taken from the entire length of the loin can be rapidly thawed in a water bath following food safety guidelines with minimal impact on meat quality. Practical Application: Freezing rate and frozen storage effects on meat quality have been well documented; however, there is comparatively little information on the meat quality effects of rapid thawing within food safety guidelines. This study demonstrates that beef strip loin steaks can be rapidly thawed in as few as 11 min without affecting texture or cooking yield, while reducing thaw drip loss. Thus, rapid thawing may enhance the apparent juiciness of steaks for consumers and provide an effective method for maintaining consistent control of experimental conditions for researchers.     

Consumer selection of constant-weight ribeye,top loin,and sirloin steaks

Constant-weight ribeye, top loin, and sirloin steaks were collected from beef carcasses (n = 25) representing five weight/loin muscle area (LMA) groups: G1 (226.8–271.7 kg; 70.97–78.96 cm²), G2 (272.2–317.1 kg; 78.71–85.81 cm²), G3 (317.5–362.4 kg; 86.45–93.55 cm²), G4 (362.9–407.8 kg; 800 cwt, 94.19–101.29 cm²), and G5 (408.2–453.1 kg; 101.94–109.03 cm²). Consumers (n = 316) selected 3 steaks of each type and ranked selection criteria (color, marbling, thickness, texture). Consumers selected ribeye steaks from G5 most frequently (P = 0.0002), but there were no differences among HCW/LMA groups for top loin or sirloin steaks. Thickness was the primary criterion for sirloins and top loins, but marbling was the primary criterion for ribeyes. Data indicate that consumers have preferences for steak thickness and appearance, but the preferred characteristics differ among consumers.     

Quality, palatability and weight loss of pork as affected by electrical stimulation

Forty-five swine (n = 15, stress-susceptible pigs, fasted for 18 h; n = 15, normal pigs, fasted for 48, 60 or 72h; n = 15, normal pigs, fasted for 18 h) were slaughtered. One side of each pig was electrically stimulated (ES)-550 V, 2-6 A, seventeen impulses, 1·8 s on and 1·8 s off per impulse-and the opposite side was not stimulated (NS). Ham and loin temperatures were monitored at 12 and 24 hours post mortem. Carcass quality-marbling, loin eye colour, loin eye firmness, subcutaneous fat firmness and belly firmness-was evaluated at 24 hours post mortem. Sides were fabricated into four lean cuts at 48 hours; cuts were placed on open metal racks in a 2°C cooler and weight loss was measured after 24, 48 and 72 hours storage. At 120 hours post mortem, loin chops were cut, frozen (-24°C for 45 days) and subsequently used to determine thaw loss, cooking loss, Warner-Bratzler shear (WBS) force and palatability. Ham temperatures (12 h) were significantly (P < 0·05) lower for the ES sides from the stress-susceptible, short-fast (SSF) group but not for normal, long-fast (NLF) or normal, short-fast (NSF) groups. ES produced lighter coloured, softer loin eyes in the SSF group but darker coloured, firmer loin eyes and firmer subcutaneous fat in the NLF group. No significant differences (P > 0·05) were detected for thaw loss, cooking loss, palatability ratings or WBS values between ES and NS in the SSF group but chops from ES sides of NLF animals had significantly (P < 0·05) higher ratings for muscle fibre tenderness, overall tenderness and overall palatability. Weight losses of the lean cuts from the ES sides were higher (P < 0·05) than those from NS sides in only three of sixty comparisons of cuts from the three groups of swine. These data suggest that ES had very minimal effects on quality, palatability or weight loss of pork.     

The electrical stimulation of beef carcasses

Beef carcasses were stimulated shortly after slaughter at varying voltage, pulse frequency and duration, with the aim of accelerating the fall of pH, destruction of ATP and onset of rigor in the muscles, so that the meat could be chilled rapidly after slaughter without danger of cold-shortening. Optimal effects were produced at 700 V, 25 Hz for 2 min, to give a total of 3000 pulses. In undressed carcasses stimulation induced a pH fall to 6.0 within 1 h of slaughter and to 5.7 within 2.5 h in the major muscles of the forelimb, back and thigh, representing a gain of more than 8 h over the time required in unstimulated carcasses hanging at 16°C. Similar results were obtained with dressed carcasses and sides, after allowing for the 50 min or so lost in dressing. The apparently high rate of pH fall from 6.3 to 5.7 after stimulation had ceased, compared with that over the same pH range in unstimulated carcasses, can be attributed mainly to the different muscle temperatures in the two cases (38 and 26°C respectively, in four major muscles). The muscles of stimulated carcasses showed no deleterious effects of stimulation. The observed drip loss from the hindlimb jointed 6 days after slaughter was not significantly greater than that from unstimulated carcasses.     

Effects of electrical stimulation and ageing of beef on the gelation properties and protein extractability of isolated myofibrils

The gelation properties of bovine myofibrils, as evaluated by dynamic rheological measurements, were shown to be very sensitive to the variables investigated: stimulation and/or ageing of the meat used, presence of 5 mM pyrophosphate and 5 mM MgCl₂ (PP) and concentration of NaCl (0·3 or 0·M). Statistical evaluation of final gel storage moduli (determined at 70°C) revealed ageing to have a consistent detrimental effect. Fresh, stimulated processing of meat), gave gels of about 40% lower elasticity (storage modulus) than did non-stimulated myofibrils; when PP was included in the gel-forming mixture no effect from electrical stimulation was seen. In spite of the negative effects observed for gel elasticity, the myofibrils in question displayed enhanced protein extractability prior to heating. Electrophoretic results suggest myosin degradation to be partly responsible.     

High pre rigor temperature limits the ageing potential of beef that is not completely overcome by electrical stimulation and muscle restraining

Two simultaneous trials were conducted to determine the effects of electrical input [electrical stunning and stimulation (ES)], wrapping, pre rigor temperature (15 °C and 38 °C) and different post rigor chilling rates on beef quality using M. longissimus lumborum (n=100). The high pre rigor temperature induced a faster pH decline than ES. The loins at 38 °C had significantly greater protein denaturation, more purge and drip loss, higher shear force values and less desmin degradation compared with the loins at 15 °C. No difference in sarcomere length was determined between the pre rigor temperatures regardless of ES and wrapping. Different post rigor chilling rates did not play a substantial role in water-holding capacity, proteolysis, or shear force values during ageing. These results suggest that high pre rigor temperature induces temperature-related toughness of muscle due to protein denaturation with subsequent limitation of proteolysis by μ-calpain, regardless of ES and wrapping treatments.     

The effects of castration, preslaughter stress and zeranol implants on beef: Part 1-The texture of loin steaks from bovine males

A total of 144 male crossbred calves were allocated to four castration or implant treatments (unimplanted bulls; unimplanted steers; bulls implanted with zeranol at 100 days of age and reimplanted at intervals of 69, 93, and 56 days thereafter; bulls implanted with zeranol at 168 days of age and reimplanted at intervals of 93 and 56 days thereafter) and two preslaughter shipping treatments (minimum preslaughter stress with cattle shipped and slaughtered within 4 h of leaving the feedlot pen; normal preslaughter stress with cattle mixed, trucked 160 km, and slaughtered up to 24 h after leaving the feedlot pen). These cattle were slaughtered and striploins of these steaks were removed after 6 days of post-mortem aging. Evaluations of these steaks were then conducted using both an experienced laboratory taste panel and a highly trained professional texture profile panel. Results indicated that: (1) the differences that existed in palatability between steaks from unimplanted bulls and steers were primarily due to differences in textural properties directly related to tenderness; (2) increases in preslaughter stress levels were detrimental to the eating quality of both intact males and castrates; (3) zeranol implants had little effect on the textural properties of bull steaks when minimum levels of preslaughter stress were applied; (4) zeranol implants in combination with normal levels of preslaughter stress resulted in steaks which readily broke down to a wide range of particle types many of which were inappropriate and detracted from a well balanced beef texture, thereby more than offsetting the beneficial effects observed on textural properties directly related to tenderness, thus, reducing the texture amplitude; and (5) the influence of the combination of zeranol implants and normal preslaughter stress on textural properties may be manifested through the production of 'dark cutting' beef.     

Palatability characteristics of loin steaks from Charolais crossbred bulls and steers

Loins from 1/2-blood or 3/4- to 7/8-blood Charolais bulls (n = 60) and steers (n = 64) were obtained at 24 h post mortem from electrically stimulated sides and, at 12 days post mortem, steaks were removed and frozen. Shear force values were higher (P < 0·001) and sensory panel evaluations of tenderness and overall palatability were lower (P < 0·001) for steaks from bulls than from steers. No differences (P > 0·05) in connective tissue amount or off-flavour were detected for steaks from bulls versus steers. Significant correlations between carcass secondary sex characteristics and sensory panel evaluations of tenderness were noted, but the coefficients were not of a magnitude to be considered predictive of tenderness.     

The effect of processing techniques and brine formulations on the development of surface sheen in enhanced beef strip loin steaks

The surface sheen phenomenon in enhanced beef steaks, packaged under modified atmosphere, was studied using various combinations of processing techniques and brine formulations. There was no effect (P > 0.05) of time between enhancement and when steaks were cut on surface sheen. Beef temperature less than 0 °C prior to enhancement, resulted in less (P ≤ 0.05) sheen and less retained pump (P ≤ 0.05) than beef greater than 2 °C. Removal of phosphate from the brine resulted in lower (P ≤ 0.05) sheen, and the addition of lactate decreased (P ≤ 0.05) sheen but resulted in less (P ≤ 0.05) retained pump. Sheen was correlated (P ≤ 0.05) with pump uptake (r = 0.58) and pH (r = -0.29). Results indicate that surface sheen can be significantly affected by ingredients used, but caution must be taken as retained brine and pH can also be affected, causing secondary influences on instrumental and visual traits.     

Biogenic amines in restructured beef steaks as affected by added walnuts and cold storage

This article evaluates changes in biogenic amines and how these relate to microbiological growth in chilled, fresh restructured beef steaks containing transglutaminase as a cold binding agent and different amounts of walnut. Added walnut and chilling favored higher total and lactic acid bacteria counts during storage, whereas Enterobacteriaceae were not affected. The highest initial biogenic amine concentrations were identified as spermidine, spermine, and tyramine. Both added walnut and cold storage generally favored the formation of amines (tyramine, histamine, putrescine, and cadaverine), which was more obviously apparent by the end of the storage period. Agmatine, on the other hand, was not generally affected by the walnut.