Sensory Properties and Lipid Oxidation in Prerigor Processed Fresh Pork Sausage

Fresh pork sausage prepared from prerigor ground and salted meat had higher pH, lower cooking losses, higher juiciness scores, and less easily fragmented cooked patties than that prepared from post-rigor ground and salted meat. Sausage from prerigor ground-post-rigor salted meat was intermediate in these properties to prerigor ground and salted and postrigor ground and salted products. Prerigor grinding and salting reduced the rate of autoxidation (TBA number) during storage at 0°C contrasted to oxidation in sausage that was salted postrigor after either prerigor or postrigor grinding.     

Preserving pre-rigor meat functionality for beef patty production

Three methods were examined for preserving pre-rigor meat functionality in beef patties. Hot-boned semimembranosus muscles were processed as follows: (1) pre-rigor ground, salted, patties immediately cooked; (2) pre-rigor ground, salted and stored overnight; (3) pre-rigor injected with brine; and (4) post-rigor ground and salted. Raw patties contained 60% lean beef, 19.7% beef fat trim, 1.7% NaCl, 3.6% starch, and 15% water. Pre-rigor processing occurred at 3-3.5h postmortem. Patties made from pre-rigor ground meat had higher pH values; greater protein solubility; firmer, more cohesive, and chewier texture; and substantially lower cooking losses than the other treatments. Addition of salt was sufficient to reduce the rate and extent of glycolysis. Brine injection of intact pre-rigor muscles resulted in some preservation of the functional properties but not as pronounced as with salt addition to pre-rigor ground meat.     

Effect of post-slaughter processing and freezing on the functionality of hot-boned meat from young bull

The effects of variation in the times of mincing post mortem (2, 4, or 6 h), pre-rigor salting (1.5% wt wt ) and freezing rate [fast (10 min, liquid nitrogen); medium (4-6 h at -40 °C and 0.8 m s(-1) air velocity); or slow (36-38 h at -10 °C and 0.1 m s(-1) air velocity followed by 12 h at -20 °C and 0.1 m s(-1) air velocity)] on the functionality of young bull meat were examined using hot-boned forequarters. At 52 h post packaging, the meat was thawed (72 h at 4 °C), its pH measured, and it was used to make finely comminuted batters. Cook yield and stress and strain of the cooked batters were measured. Time of mincing had no effect on meat pH, cook yield or stress and strain. There was a significant interaction (P < 0.05) between pre-rigor salting and freezing rate for pH. Freezing rate did not affect the pH of pre-rigor salted meat whereas the pH of unsalted pre-rigor meat was highest at the fastest freezing rate. Meat salted pre-rigor had a significantly (P < 0.05) higher pH than the post-rigor chilled control. Pre-rigor salting decreased the stress values of cooked batter whereas the slowest freezing rate increased stress. Stress and strain values for cooked batters from thawed meat were not significantly different from the values for batters made from the unfrozen control. Cook yields of batters made from pre-rigor frozen meat were higher than that of the postrigor control but not significantly so. The results indicate that suppliers can use pre-rigor salted and frozen meat when manufacturing comminuted products without major detrimental effects on the cook yield and texture of the finished product.     

Effects of transport time and rest period on the quality of electrically stimulated male cattle carcasses

Ground, pre-salted, pre-rigor semimembranosus muscles of beef were subjected to three treatments A=rapid carbon dioxide (CO(2)) chilling, B=slow CO(2) chilling and C=air chilling, and compared to a control D=slow air chilling of muscles, which were subsequently ground and salted post-rigor. Meat of the pre-rigor treatments A, B and C had higher pH values during processing, lower cooking loss, firmer texture and a lighter yellowish external colour of cooked patties than the post-rigor control D (p<0.05). The two CO(2) chilling regimes A and B had no detrimental effects on the functional properties of the pre-rigor meat. Sarcomere lengths did not differ in meat of the four treatments (p>0.05), indicating that early pre-salting protected the meat from cold shortening during rapid temperature decline. A process combination of grinding, followed by immediate pre-salting and CO(2) chilling within 312h post-mortem of non-stimulated beef muscles is likely to yield superior binding properties of cooked patties and similar ground beef products.     

Effect of salt on myoglobin derivatives in the sarcoplasmic extract from pre- and post-rigor beef in the presence or absence of mitochondria and microsomes

The effect of salt and pH on the colour stability (oxymyoglobin) in the sarcoplasmic extract (SPE) prepared from pre- and post-rigor beef muscle was studied in the presence or absence of mitochondria and microsomes during 96 h at 4°C. The sarcoplasmic extract from the post-rigor meat (pH 5·4) or from the pre-rigor meat adjusted to pH 5·4 contained more oxymyoglobin (MbO(2)) than the pre- or post-rigor SPE maintained at pH 7·4. The presence or absence of mitochondria and microsomes in the SPE at pH 5·4 had little effect on the percentage of MbO(2). At pH 7·4, however, the percentage of MbO(2) decreased in the SPE in the presence of mitochondria, whereas the percentage of MetMb was lower in the presence of microsomes. The relative proportion of MbO(2) decreased and that of metmyoglobin (MetMb) increased with increasing salt concentration at low pH (more so in the absence of subcellular organelles) and with storage period in the SPE from both pre- and post-rigor meat. However, at pH 7·4, high levels of salt (2-4%) helped to maintain a high percentage of MbO(2) in SPE in the absence of subcellular organelles, especially the mitochondria. The first-order interactions of pH value × subcellular organelles (P < 0·01) and pH value × salt concentration (P < 0·01) accounted for about 55% of the total variation in the percentage of MbO(2) in the SPE. It is suggested that depressing microbial growth may be the operative mechanism by which added salt stabilizes the colour in pre-rigor minced meat rather than by enzymic effects of subcellular organelles.     

Effects of chopping time, meat source and storage temperature on the colour of New Zealand type fresh beef sausages

The colour stability of finely chopped fresh sausages made from post-rigor, pre-rigor salt added (1.5% w/w) or pre-rigor no salt added beef mince was evaluated using a Hunter Miniscan (L (?) a (?) b (?)) and sensory colour panel. Batters were chopped for various times and sausages stored at -1.5 °, + 4.0 ° and + 8.0 °C. Regardless of meat source or chopping time, colour stability was greatest at -1.5 °C. Panellists found the colour of all sausages stored at -1.5 °C acceptable for at least six days. Sausages made from unsalted pre-rigor mince had markedly better colour stability than those made from the other meats, especially when stored at 4 °C or 8 °C.     

Effects of brine ingredients and temperature on cook yields and tenderness of pre-rigor processed roast beef

In semimembranosus (SM) muscles removed pre- and post-rigor and injected 10% (wt/wt) with brines formulated to give 2% salt, 1.5% glucose, 0.3% phosphate, 0.15% calcium chloride or 3% sodium lactate in the finished product and cooked within 1 h of injection, cook yields were not significantly affected by processing pre- or post-rigor. Within treatments, however, brine composition had a significant (P < 0.05) effect on cook yields; highest yields were obtained using salt (although this was not significantly different from the water injected control) and lowest yields with calcium chloride. Adding phosphate resulted in lower peak shear force values, and less energy was required to break the sample. The most tender roasts from pre-rigor meat were produced using salt, phosphate or lactate brines and the least tender using calcium chloride. Brine temperature (0-12 °C) during injection had little effect on cook yields or tenderness of the roast beef manufactured pre-rigor. The results indicate that accelerated processing of roast beef can result in finished product with acceptable yields and tenderness if salt and phosphate brines are used.     

Influence of cooling and freezing of minced pre-rigor muscle on the breakdown of ATP and glycogen

The high water-holding capacity of pre-rigor beef can be preserved for months by rapid freezing of the minced salted or unsalted bovine muscle before onset of the breakdown of ATP. If beef frozen in this way is processed without preceding thawing, sausages of excellent quality are obtained. The same result can be obtained using beef salted and freeze-dried in the pre-rigor state. It is important in both procedures to ensure that the depletion of ATP during freezing is kept to a minimum. The optimum conditions for cooling and freezing were therefore studied. If NaCl is not added, the rate of ATP breakdown decreases with falling temperature to about +6°C but then increases with further cooling, reaching a maximum rate at about -1°C, at which temperature the meat remains for a relatively long period during freezing. If the beef is salted, the rate of ATP hydrolysis decreases with falling temperature until the meat is frozen. Above + 3°C the concentration of ATP is lower in salted than unsalted meat in the first hours post mortem, but below this temperature the position is reversed. The influence of temperature on lactate formation, i.e. on the rate of glycolysis in the presence and absence of salt, follows similar patterns. Therefore, it is better to salt the beef before freezing rather than during the preparation of the sausage emulsion. These influences of temperature on the ATP depletion in unsalted and salted beef can be explained in terms of the release of Ca(2+) ions from the sarcoplasmic reticulum.     

Osmotic properties of post-rigor beef muscle

The osmotic pressure of beef sternomandibularis and psoas muscles ranged from 480 to 540 mOs, which is almost twice that of pre-rigor muscle (about 300 mOs). The post-rigor osmotic pressure appears to be satisfactorily explained by the low molecular weight components. Muscle samples were soaked at 2°C for 24 h in various solutions and sample weight changes were recorded. Samples soaked in buffered mannitol solutions exhibited weight changes indicative of predictable osmotic behaviour. Those samples soaked in buffered salt solutions (KCl, NaCl), however, exhibited dramatic increases in weight, irrespective of the solute concentration. The reasons for this are not clear. These results indicative that the use of salt solutions, such as 0·15 m KCl, for studies on post-rigor muscle is suspect and conclusions from such studies may be unfounded.     

The effects of hot water pasteurizing treatments on the appearances of pork and beef

Portions of post- and pre-rigor pork and beef were treated by immersion in water of 75 or 85 °C for 5, 10, 15 or 20 s. The appearances of untreated and treated cut muscle, fat, membrane covered and cut bone surfaces, and the overall appearances of treated and untreated meat pieces, were assessed by a 5-member panel 2 hr and 24 hr after each treatment. At those times, CIE L(?)a(?)b(?) values were obtained for cut-muscle surfaces. The appearances of surfaces covered by membrane, of fat and cut bone surfaces of pre-rigor pork and beef, and of fat and cut bone surfaces of post-rigor pork, were not persistently degraded by any treatment. However, the appearances of fat and cut bone surfaces of post-rigor beef were persistently degraded by the harsher treatments, apparently because of pre-treatment staining of fat and changes in the bone marrow. Panel scores for the overall appearance and for the appearance of cut muscle surfaces were generally the same for each meat piece. All treatments caused patchy bleaching of cut muscle. The degraded appearances of pre- and post-rigor pork and post-rigor beef muscle persisted at 24 hr, but the appearances of beef muscle treated pre-rigor improved between 2 and 24 hr. Most treated muscle gave increased CIE L(?) values and decreased a(?) and b(?) values as compared with untreated portions from the same primal cut. However, CIE b(?) values for pre-rigor beef muscle were higher than for untreated muscle 2hr after treatment, but lower than for untreated muscle 24 hr after treatment. It appears that pasteurizing treatments cannot be applied to meat without some degradation of the appearances of cut muscle surfaces, which will persist in pork treated pre- or post-rigor and in beef treated post-rigor, but which will partially resolve during the storage of beef treated pre-rigor.     

Modelling post-mortem tenderisation-I: Texture of electrically stimulated and non-stimulated beef

Texture in electrically stimulated and non-stimulated beef M Pectoralis profundus, stored under a range of temperatures from 0 to 30°C, while avoiding muscle shortening, was measured from 1 to 21 days after stunning. The pre-rigor temperature (from 0 to 30°C), maintained until the pH had fallen to 6·4 and then held at 15°C, had no effect on the toughness nor on the rate of tenderisation after rigor. Modelling toughness prior to 24 h suggested that toughness of all muscles could be rationalised and that first-order tenderisation began when the muscles reached pH 6·1 when the toughness of all the muscles was projected to be 12·5 kg. After pH 6·1, the rate of tenderisation at 30°C was 10-fold higher than at 1°C and was not affected by variations in pH from 6·1 to 5·5. At the higher temperatures, the ultimate toughness of aged meat was slightly higher than at the lower temperatures.     

Pressure-induced pH and length changes in muscle

The response to increase in pressure of pre- and post-rigor muscle strips supporting a load has been investigated by measuring length changes with application of pressure up to 150 MPa in a windowed pressure vessel. The response of the pre-rigor strips depended on temperature; at 30°C the strips contracted, then, after some minutes, lengthened, presumably because of a breakdown of myofibrillar integrity. At 0°C the cold-shortened muscle lengthened but if pressure was released the strips shortened again. Loaded post-rigor muscle strips lengthened with application of pressure. It is suggested that the conditions that prevail in pre-rigor muscle are not as favourable for disaggregation of the myofilaments as those in post-rigor muscle. Measuresurement of pH changes in pre-rigor pressure-treated muscle showed these were accelerated at 30°C, but completely inhibited by treatment at 0°C for 3 or 24h.     

The effects of conditioning on meat collagen: Part 4-The use of pre-rigor lactic acid injection to accelerate conditioning in bovine meat

Injection of fresh bovine muscle with 0·1 m lactic acid (to a level of 10% of original muscle weight) resulted in a pH decline to a minimum pH of 5·33 at 15°C only 3 h after injection. Untreated muscle reached the same pH after 26 h when held at the same temperature. Fresh, unconditioned meat colour was unaffected by pre-rigor 0·1 m lactic acid injection as assessed by visual inspection. The percentage of perimysial collagen extracted as the soluble form was significantly higher (P < 0·05) from three muscles of varying quality when pre-injected with 0·1 m lactic acid and conditioned from 1 to 14 days, than from conditioned untreated muscles. SDS-polyacrylamide gel electrophoresis of CNBr peptides from insoluble perimysium obtained from three muscles of varying quality revealed no obvious differences due to pre-rigor lactic acid injection before conditioning. However, analysis of the high molecular weight perimysial collagen CNBr peptides from lactic acid treated muscles by two-dimensional SDS-polyacrylamide gel electrophoresis revealed an increased incidence of degradation in this region compared with untreated controls. These data strongly suggest that pre-rigor injection of beef muscle with lactic acid may accelerate conditioning. The implications of this finding are discussed.     

Pre- and Post-Rigor Sectioned and Formed Beef Steaks Manufactured with Different Salt Levels, Mixing Times and Tempering Times

This study was designed to identify processing parameters necessary for the incorporation of pre-rigor beef in sectioned and formed steaks. Meat logs were prepared from pre- or post-rigor beef muscle with 0.0, 0.5 or 1.0% salt, mixed for 0, 6, 12 or 18 min, frozen and tempered to —3°C. Logs were pressed and cleaved after 0, 24, 48 or 72 hr tempering. Tempering at -3°C resulted in sufficient metabolic activity (as measured by pH and R-value) to deplete the ATP content of pre-rigor muscle. The presence of salt hastened the onset of rigor, maintained a higher ultimate muscle pH and improved cooking yields, bind (adhesion) and tenderness. Longer mixing times enhanced bind. These data suggest that, with appropriate modification in the processing procedure, pre-rigor muscle can be incorporated into sectioned and formed products.     

Effect of pH at time of salting on the functional properties of pre-rigor beef

The functional properties of thawed pre-rigor beef that had been minced and salted or not salted when its pH value reached 6.8, 6.6, 6.4, 6.2 and 6.0, then immediately frozen, were determined. The mince samples were used to manufacture a finely comminuted sausage batter. Presalting before frozen storage resulted in higher (p < 0.05) thawed mince pH, and batter cook yield and shear strain, and lower (p < 0.05) mince salt soluble proteins, thaw drip and Hunter L^* and b^* values and batter shear stress than unsalted controls. The pre-rigor pH at time of salting/mincing affected (p < 0.05) thaw drip (unsalted mince only), Hunter L^* and b^* values and shear stress. Shear stress tended to increase (p < 0.01) and Hunter L^* (p < 0.05) and b^* (p < 0.01) values tended to decrease with fall in pre-rigor salting pH. No interaction (p > 0.05) between salting and pre-rigor pH at time of salting was observed.     

Antioxidative activity of α-tocopherol in cooked and uncooked ground pork

The effect of α-tocopherol (0, 100, 200 ppm) on lipid oxidation either in cooked or uncooked ground pork was studied during aerobic storage at 4°C and -20°C. Lipid oxidation was measured using the 2-thiobarbituric acid (TBA) method and rancidity development was scored by a trained sensory panel. Alpha-tocopherol slowed the rate of oxidation in cooked ground pork stored at either 4°C or -20°C and uncooked samples refrigerated for extended periods of time (12 days). In cooked product stored at 4°C where oxidation development was intense and off-flavors were strong, panelists did not detect flavor differences due to treatments. But in cooked product stored at -20°C sensory results were consistent with TBA analysis. Pre-rigor grinding, known to induce a high pH and inhibit lipid oxidation in uncooked fresh pork, had no protective effect on lipid oxidation as measured by TBA values in cooked ground pork, regardless of storage condition. TBA numbers increased during storage of cooked product at 4°C with an increase in internal cooking temperature between 50°C and 80°C. Internal cooking temperatures of 70°C or higher induced a rapid rate of oxidation when stored at 4°C.     

Shortening and tenderness of pre-rigor heated beef: Part 2 - Effect of heating rate on muscles of electrically stimulated carcasses

This study was conducted to compare the effects of rapid and slow heating rates on muscles from electrically stimulated beef carcasses. Myofibrillar and cooking shortening and related changes were measured with physiograph recordings on pre-rigor M. triceps brachii strips suspended in paraffin oil during heating. Warner-Bratzler shear values were determined on pre-rigor and post-rigor M. triceps brachii samples heated at approximately the same rates at which muscle strips were heated (2°C/2 min and 2°C/12 min), on pre-rigor M. triceps brachii samples heated at 2°C/6 min, 2°C/9 min and 2°C/12 min and on pre-rigor and post-rigor M. triceps brachii and M. longissimus muscle heated similarly at 2°C/12 min. Rapid heating (2°C/2 min) of pre-rigor muscle produced more severe myofibrillar shortening that was complete at higher muscle temperature than slow heating (2°C/12 min). Slow heating, in contrast to rapid heating, resulted in a cooked product of lower shear value in both the pre-rigor and post-rigor states. The slower the heating rate of the pre-rigor M. triceps brachii, the more tender was the product. Heating at a rate of 2°C/12 min produced acceptable tenderness in both the pre-rigor M. longissimus and M. triceps brachii muscles but even greater tenderness when both muscles were heated in the post-rigor state. The tenderizing action of severe muscle shortening could not be induced in electrically stimulated muscle.     

Double-antibody ELISA for detection of trace amounts of pig meat in raw meat mixtures

Pre-rigor cooked beef is tender if the cooking produces severe shortening. This study was conducted to compare the effects of different heating rates on shortening and tenderness. Myofibrillar and cooking shortening and related changes were measured with physiograph recordings on pre-rigor M. triceps brachii strips suspended in paraffin oil during heating. Warner-Bratzler shear values were determined on M. triceps brachii samples heated at approximately the same rates at which the muscle strips were heated. Rapid heating (2°C/2min) produced more (p < 0·01) severe myofibrillar shortening that was complete at higher (p < 0·01) muscle temperatures than slow heating (2°C/12 min). Regardless of animal age, rapid heating resulted in a cooked product that was more (p < 0·01) tender than that produced by slow heating in the pre-rigor state and slow heating resulted in a more (p < 0·01) tender product than that achieved by rapid heating in the post-rigor state. Data on muscle shortening and from differential scanning calorimetry suggest that the tenderness produced from pre-rigor rapid heating results from a heat-induced active contraction.     

Effect of NaCl, polydextrose, and storage conditions on the functional characteristics and microbial quality of pre- and post-rigor salted beef

The functionality and microbial storage life of pre-rigor beef mince stored at −1.5 °C under vacuum or a saturated carbon dioxide atmosphere, or at −18 °C in polyethylene bags, was investigated. Salt (2% w/w) or salt plus the cryoprotectant Polydextrose^® (2%/2.6% w/w) was added pre-rigor to some samples. Chilled storage decreased salt soluble protein (SSP) by 13–18% (P < 0.01); frozen storage decreased SSP content by 20%. Pre-rigor salted mince in saturated carbon dioxide packs had a satisfactory microbial quality after 12 weeks storage. The cook yield of finely comminuted sausage batters made from that mince and from fresh pre-rigor mince were similar, although batter stress and strain decreased with chilled storage. Adding Polydextrose^® to salted mince improved batter strain compared with the non-additive and salt-only samples and improved batter stress compared with the salt-only samples. The microbial storage life of chilled vacuumpacked unsalted mince was less than 6 weeks; pre-rigor salting increased its storage life.     

Effects of rigor attainment temperature on meat blooming and colour on display

This paper describes the colour properties of seven hot-boned, unstimulated beef striploins during rigor attainment at 9, 14 and 24°C, during blooming at 4°C, and after storage at -1°C for 0, 2 and 8 weeks. Immediately after rigor attainment (0 weeks of storage) full blooming, as judged by L* and chroma, took at least 12 h. After 2 and 8 weeks storage, blooming was complete within about 4 h. The exponential equations describing blooming were different for 0 weeks compared with 2 and 8 weeks. This difference can be explained in terms of oxygen consumption by meat freshly in rigor. At 0 weeks, meat that entered rigor at 24°C had the best bloomed colour, whereas at 2 and 8 weeks the 9°C treatment had the best and the 24°C the worst. The data set, which spanned a range of ultimate pH values and three rigor attainment temperatures, was used to estimate the value of early colour measurements (first 24 h post-rigor) in predicting colour during display several weeks later. As judged by correlation coefficients, early measurements of hue were the only ones useful. L* and chroma were poor predictors. This result, together with the knowledge that blooming is slow in the first 24 h post-rigor, casts doubt on the value of subjective or objective colour assessments made in chillers. Temperature of rigor attainment between 9 and 24°C did not affect the time of browning onset, nor the rate of browning. It was confirmed that meat with lower pH had higher chroma before and after blooming.