Stability at cooking temperatures of model chicken breast muscle emulsions

Emulsion stability (ES) was measured on timed emulsification (TE) samples made with natural actomyosin (NAM) and exhaustively washed (EW) muscle, heated to 75°C, before using the Omni-mixer or after centrifugation. All emulsions cooked after centrifugation were found to be stable. The emulsions made with NAM showed a large decrease in ES when heated above 40°C prior to using the Omni-mixer. However, aqueous protein disappearance did not decrease significantly after TE until NAM was heated to between 60°C and 75°C. On the other hand, emulsions made with EW muscle heated prior to using the Omni-mixer showed a large decrease in both ES and aqueous protein disappearance after TE between 60°C and 75°C.     

Effects of postmortem temperature and time on the water-holding capacity of hot-boned turkey breast and thigh muscle

Turkey breast and thigh muscles were excised immediately after slaughter and held from 0.25 to 4 h postmortem at 0, 12 or 30 °C to determine postmortem time and temperature effect on muscle pH, drip loss, sarcomere length, homogenate supernatant weight, salt-soluble protein and cooking yields. Higher temperature and longer storage time induced greater drip losses in breast. Longer storage time induced greater drip losses but the least drip loss occurred at 12 °C in thigh muscle. High temperature increased the supernatant weight in breast but decreased that in thigh. Storage time increased supernatant weight and supernatant salt soluble protein levels in both muscles. Homogenate cooking yields of breast containing water, salt and phosphate (HWSP) were higher for 0 and 12 °C compared with 30 °C, and increased with storage. The low postmortem temperature (0 °C) decreased homogenate cooking yields in thigh. These findings indicate that lower postmortem temperatures (0 and 12 °C) and shorter storage time (24 h) produced the greatest water-holding capacity in turkey breast muscle, whereas high and low postmortem temperatures (30 and 0 °C) and longer storage (168 h) produced the least water-holding capacity in raw turkey thigh muscle.     

Timed Emulsification Studies with Chicken Breast Muscle: Whole Muscle, Low-Salt Washed Muscle and Low-Salt Soluble Proteins

Emulsion formation with chicken breast muscle was investigated using timed emulsification. Emulsions were made at a fixed oil/water ratio of 2:1 by Omni-mixing for various lengths of time between 0 and 5 min; then the emulsions were centrifuged and the aqueous layer analyzed for protein. Emulsions formed using whole muscle or muscle washed with low molarity salt solution and suspended in buffered (10 mM sodium phosphate, pH 7.0) 0.6M NaCl were superior in stability upon centrifugation to those made with muscle in distilled water, buffered 0.025M NaCl or buffered 0.05M NaCl. Size of insoluble protein pellets from the centrifuged emulsions decreased as emulsification time increased. Little emulsifying effect of the low-salt soluble (sarcoplasmic) protein, defined as those proteins extracted with buffered 0.05M NaCl, was observed in the presence or absence of high-salt solubilized protein.     

Timed Emulsification Studies with Chicken Breast Muscle: Soluble and Insoluble Myofibrillar Proteins

Emulsion formation with chicken breast muscle was investigated using timed emulsification. High-salt soluble proteins (pH 7.0, 0.6M NaCl) extracted from previously washed muscle (pH 7.0, 0.05M NaCl) were removed from the aqueous phase as mixing time increased. Low- and high-salt exhaustively washed muscle, resuspended in either 0.15 or 0.6M NaCl, pH 7.0, still exhibited good emulsion properties. The pellet protein decreased (> 90%) as mixing time increased from 0 to 5 min. Addition of sodium pyrophosphate to 0.6M NaCl suspensions of 0.05M NaCl washed muscle resulted in an increase in solubility of myofibrillar proteins and a general improvement in emulsification properties. High-salt insoluble proteins may play an important role in emulsion formation.     

Emulsion Stability and Water Uptake Ability of Chicken Breast Muscle Proteins as Affected by Microbial Transglutaminase

ABSTRACT: Using response surface methodology, the effect of microbial transglutaminase (TG) concentration and incubation time (IT) after emulsification, but before creaming, on the functional properties of chicken meat proteins was examined. TG improved the stability of emulsions (ES) made with a high-salt chicken meat protein extract, although TG did not significantly affect the amount of protein incorporated into the emulsion cream layer. IT significantly enhanced ES when incubated at 40 °C, but not at 4 °C. TG increased the water uptake ability (WUA) of both chicken muscle and chicken muscle protein extract incubated at 40 °C and 4 °C. Similarly, TG increased the protein and water content of the pellet formed in the WUA test. TG therefore appears to be a useful method to enhance the stability and yield of meat batters.     

Heat and ultrafiltration extraction of broiler meat carnosine and its antioxidant activity

This study examined the effects of extraction and further ultrafiltration on the carnosine content, antioxidant activity and total iron content of chicken muscle extracts. Fresh breast meat had 7-fold higher carnosine than fresh thigh meat (2900 versus 419μg/g meat, respectively). Carnosine extracts of breast and thigh were prepared by heating at 60, 80 and 100°C, and ultrafiltration (UF) using a 5000MW cut-off. At increasing temperatures, protein concentrations decreased while carnosine, total iron and antioxidant activity increased. Antioxidant abilities of the 80 and 100°C-heated extracts were greater than that of the 60°C extract (p<0.05). The ultrafiltrate from the 80°C-heated extract had approximately 20% higher carnosine, but 40% lower protein and 10-30% lower iron than the 80°C-heated ultrafiltrate. However, compared in terms of carnosine concentration, the meat extracts had greater antioxidant activity than pure carnosine (p<0.05).     

Modelling the yield and texture of comminuted pork products using color and temperature. Effect of fat/lean ratio and starch

Practices to control the processing of finely comminuted meat products are proposed. The objective was to test the practical value of both temperature and light reflection measurements made during emulsification as potential indicators of cooking losses and resulting gel texture in pork sausages emulsified within a wide range of temperatures and starch and fat levels. Prior to cooking, pork batters were chopped for different times to ensure final emulsion temperatures ranging from 5 to 50°C. The effects of the fat/lean ratio (0.25 and 0.67) and starch addition (0.8 and 3.2% w:w) on temperature and optical reflection were also investigated. The chopping increased the temperature and decreased the light reflection of fresh meat emulsion. There was no relevant loss of emulsifying capacity at emulsion temperature below 30°C and lightness values over 70 CIE units. The losses and textural parameters of cooked emulsions could be predicted by means of non-linear regression equations based on the temperature and color of the raw emulsion. The determination coefficients obtained ranged from 0.89 to 0.99. The prediction models needed to be fitted to each batter formulation, especially in the presence of reduced levels of gelation agents (meat protein and starch). Lightness was a better predictor than chromaticity, since it decreased constantly with chopping in the range of final emulsion temperatures studied (5-50°C). This confirms previous studies that lightness could be used for monitoring emulsion stability in meat batters.     

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.     

Chilling pig carcasses: Effects on temperature, weight loss and ultimate meat quality

Effects of conventional (4°C, air velocity 0·5 m/s) and forced chilling at -5°C (120 min) or -30°C (30 min) with air velocities of 1, 2 or 4 m/s, followed by conventional chilling till 24 h post mortem on temperatures, meat quality and weight losses, were studied. Experiments were carried out in six batches of six slaughter pigs each (crossbred gilts, weighing 105-110 kg. The subcutaneous temperature decreased very rapidly to values below 0°C when 'ultra' rapid chilling (-30°C) at high air velocities (4 m/s was used. Immediately after rapid chilling, when the carcasses were railed into a conventional chiller, the subcutaneous temperature increased above the air temperature, after which the decline in temperature was continued. Temperature inside the biceps femoris muscle decreased from the start of chilling rather slowly according to an asymptotic curve until ultimate values of 4°C were reached. Theoretically calculated temperatures during slaughter and chilling were comparable with the measured values; indicating that a finite-element calculation method in combination with a cylindrical model for heat transport can be used to predict muscle temperatures for various chilling regimes. Losses in carcass weight, 24 h after conventional and forced chilling at -5°C, were about 2%. After 'ultra' rapid chilling (-30°C) the losses were reduced to 1·3% when air velocity was increased to 4 m/s. Meat quality of the longissimus lumborum muscle was not significantly affected by the various chilling regimes except for the variables related to tenderness. The Warner-Bratzler shear forces were higher (P < 0·05) together with shorter sarcomere lengths (P < 0·10) after 'ultra' rapid chilling at a high (4 m/s) air velocity, indicating an increased risk of cold shortening.     

Optimum chopping conditions for Alaska pollock, Pacific whiting, and threadfin bream surimi paste and gel based on rheological and Raman spectroscopic analysis

Rheological and Raman spectroscopic properties of surimi from three species [Alaska pollock (AP) (cold water), Pacific whiting (temperate water), and threadfin bream (warm water)] were investigated as affected by various chopping conditions. Comminuting Alaska pollock surimi at 0 °C demonstrated superior gel hardness and cohesiveness when chopping time was extended to 15-18 min; however, long chopping time at higher temperatures resulted in a significantly decreased gel texture particularly at 20 °C. Warm water fish threadfin bream exhibited higher gel texture when chopping was done longer at higher temperature. Rheological properties were significantly affected by both chopping time and temperature. Species effect, based on their thermal stability, was readily apparent. Raman spectroscopy revealed a significant change in disulfide linkage and the reduction of secondary structure upon extended chopping. Dynamic oscillation rheology demonstrated the damage of light meromyoisn and lowering of onset of gelling temperature as the chopping time was extended. PRACTICAL APPLICATION: Chopping conditions to determine gel quality and manufacture surimi seafood are varied by all manufacturers. This paper covering three primary species for surimi with their suggested optimum chopping conditions: 15 min for Alaska pollock when chopped at 0 °C, 15 min for Pacific whiting at 15-20 °C, and 18 min for threadfin bream at 25-30 °C. The use of optimum chopping condition should maximize the value of each surimi and provide consistent quality to the end users.     

原辅料添加顺序对乳化型香肠品质的影响

对5 种原辅料不同添加顺序生产的乳化型香肠的持水性、质构特性(感官评定和机械测定,其中机械测定包括TPA 压缩和W-B 剪切)和微观结构进行研究。结果表明：按照瘦肉蛋白提取后和脂肪的乳化体混合斩拌,最后拌制调味料、淀粉、剩余冰水的顺序生产的乳化型香肠的持水性、质构特性和微观结构都最好,TPA 压缩法和W-B 剪切测试多重比较结果均呈显著差异性。     

Effect of heat processing on DNA quantification of meat species

In this study, real-time polymerase chain reaction (PCR) was used for identifying the effects of different temperatures and times of heat treatment on the DNA of meat products. For this purpose, beef, pork, and chicken were baked at 200 °C for 10, 20, 30, 40, 50 min, and for 30 min at 30, 60, 90, 120, 150, 180, 210 °C and also cooked by boiling at 99 °C for 10, 30, 60, 90, 120, 150, 180, 210, and 240 min. The DNA was then extracted from all samples after the heat treatment. Further, a region of 374, 290, and 183-bp of mitochondrial DNA of beef, pork, and chicken, respectively, was amplified by real-time PCR. It was found that baking and boiling of the beef, pork, and chicken resulted in decreases in the detectable copy numbers of specific genes, which varied with the heating time and degree. The results indicated that species determination and quantification using real-time PCR are affected by the temperature, duration of the heat treatment, and size of the DNA fragment to be amplified.     

The influence of high temperature, type of muscle and electrical stimulation on the course of rigor, ageing and tenderness of beef muscles

The course of rigor mortis (rigor), ageing and tenderness has been evaluated for three beef muscles; M. biceps femoris (BF), M. semimembranosus (SM) and M. semitendinosus (ST), when entering rigor at constant temperatures of 15 and 37°C respectively, with and without electrical stimulation (ES/NS) (85 V, 14 Hz and 32 s). The course of post-mortem changes has been registered by isometric tension, by shortening of unrestrained muscle strips and by following the pH decline and the changes in metabolites, such as ATP and CP. Ageing at +4°C was recorded by measuring Warner-Bratzler (W-B) shear values 2, 8 and 15 days post mortem. On the last occasion, the sensory properties of the cooked meat were also evaluated. Maximum shortening and isometric tension were higher at 37°C as compared to 15°C, whereas ES did not reduce rigor shortening. A high correlation between maximum shortening and the ATP-level at the onset of the shortening rapid phase was found (r = 0·77(???)), which could explain the greater shortening obtained at 37°C compared to 15°C. Rigor shortening is an important phenomenon governing meat tenderness as tenderness is highly affected by rigor temperature but not by ES. This was the case for muscles SM and ST but not for BF muscle. Even though tenderness was measured after ageing (15 days post mortem), shortening during rigor seems to be more important for toughness when rigor mortis occurs at 37°C than any suggested tenderizing effect due to increased proteolysis in this temperature region.     

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.     

Liberation of actin from actomyosin in meats heated to 65°C

This study investigated whether actin liberation from myofibrils occurs during the heating of various muscles, as well as squid mantle muscle at temperatures, such as 60°C, employed for vacuum cooking of meats. Actin liberation was demonstrated in scallop striated adductor muscle, but not in beef, pork, or chicken, using the detection method previously employed with squid muscle, in which liberated actin was detected with SDS-PAGE, in the supernatant obtained by centrifugation of the homogenate of heated muscle in 0.2M KCl at a neutral pH. However, actin liberation was demonstrated in beef, pork and chicken by a new detection method, in which heated muscle was homogenized in 0.6M KCl or NaCl at a slightly alkaline pH and maintained at 4°C for 16h with stirring, after which the homogenate was diluted three times with water and centrifuged to obtain the supernatant containing the liberated actin. This new method indicated that actin liberation in beef, pork, and chicken was marked by heating at 65°C, but scarcely induced at 80°C. Thus, the liberation of actin from myofibrils may contribute to the greater tenderness of vacuum-cooked meat (meat heated at a low temperature for long time), as compared with meat prepared by cooking at a higher temperature.     

Effect of dipping in pomegranate (Punica granatum) fruit juice phenolic solution on the shelf life of chicken meat under refrigerated storage (4°C)

An experiment was conducted to evaluate the effect of dipping in pomegranate fruit juice phenolics (PFJP) solution on the shelf life of chicken meat held under refrigerated storage at 4°C. Breast muscle obtained from spent hens was dipped (1:2w/v; muscle: liquid) in sterile water or in sterile water with 0.02% (v/v) PFJP, packed, stored at 4°C for 28 days and samples were analyzed on 2 days of intervals. Thiobarbituric acid reactive substance values were lower in samples treated with PFJP. Total sulfhydryl and protein bound sulfhydryl content values were higher in samples treated with PFJP. Microbial quality evaluation showed that aerobic and psychrotrophic counts were higher in samples treated without PFJP. Sensory evaluation revealed that acceptability level of samples treated without PFJP decreased on 12th day of storage. It is concluded that spent hen breast meat samples dipped in 0.02% PFJP reduced protein oxidation and inhibited microbial growth and sensorily acceptable up to 12 days of refrigerated storage at 4°C.     

Thermal Transitions of Salt-soluble Proteins from Pre- and Postrigor Chicken Muscles

Salt-soluble protein (SSP) was extracted from pre- and postrigor chicken muscles at various pH values, and protein thermal denaturation was studied using several techniques. Heating at 1°C/min from 20 to 70°C induced a three- to fourfold increase in breast and leg hydrophobicity. Differential scanning calorimetry of breast and leg SSP showed a major transition occurring within the range 55 to 64°C, with the value dependent on rigor state and pH. Protein-protein association, as measured by turbidity change upon heating, underwent two transitions for leg SSP and two or three for breast SSP. The specific transition temperature and rate were dependent on pH, muscle type and rigor state. However, muscle type and pH had a greater effect than muscle rigor state on SSP denaturation.     

Effects of thawing temperature on the physicochemical properties of pre-rigor frozen chicken breast and leg muscles

The objective of this study was to evaluate effects of thawing temperature on the biochemical and physicochemical properties of pre-rigor frozen chicken breast and leg muscles. Breast and leg muscles from 24 broiler chickens were excised within 10min postmortem. Pre-rigor muscles were frozen at -20°C and thawed at 0 and 18°C, and pH, R-value, sarcomere length, muscle shortening, thaw and cook loss, shear force and myofibrillar fragmentation index (MFI) compared with those in pre-rigor or 2°C chilled muscles. The ultimate pH of 18°C thawed muscle was lower than that of 0°C thawed and 2°C chilled muscles. As expected, the shortening of sarcomere length and muscle length of thaw rigor muscles were more than those of chilled muscle, but there were no significant differences between chilled muscle and 0°C thawed muscle. Also, there were no significant differences in R-value (Abs 250/Abs 260) and cook loss due to thawing temperature. Samples thawed at 0°C had higher MFI and lower shear value than samples thawed at 18°C. Shear force value and MFI were not significantly different between chilled muscle and 0°C thawed muscle. By thawing at 0°C, thaw shortening was prevented, and tender meat comparable to the chilled meat was obtained.     

The effect of conditioning on the strength of perimysial connective tissue dissected from cooked meat

Tensile tests were carried out on ribbons of perimysial connective tissue dissected from slices of bovine semitendinosus muscles that had been conditioned or not conditioned and then cooked to a range of temperatures. A consistent reduction in the strength of the perimysia was seen in the conditioned samples, both in the raw meat and meat cooked to 50°C. At higher cooking temperatures (60-80°C), no effect of conditioning was seen. The content of collagen or total protein of mechanically extracted perimysia and the collagen content of the test pieces from conditioned and unconditioned muscles was not significantly different. It was concluded that conditioning decreases the breaking strength of the perimysial connective tissue in raw meat or in meat which is subsequently cooked to 50°C, but not in meat cooked to the temperatures normally employed by consumers. The tenderization observed in conditioned meat cooked to 60°C and above is, therefore, due to the weakening of muscle fibres within the fibre bundles.     

Low-temperature osmotic dehydration improves the quality of intermediate moisture meats

Dehydration of meat at low temperature (4°C) with a new dehydrating sheet to obtain intermediate moisture meat produced more desirable results than did more rapid dehydration at 25°C, because the native state of meat proteins was better retained at the lower temperature. At low temperature with replacement of the dehydrating sheet once per day, the water content decreased to 57% after 150 h. Water activity (a(w)) dropped to 0·965. Myofibrils could be prepared readily from meat after 150 h at 4°C, and the myofibrils were induced to contract by addition of Mg(2+)-ATP solution and therefore retained biological activity. Electron microscopic observation showed that intermediate moisture meat prepared at 4°C retained the original muscle structure to a large extent. Myosin could be extracted easily from intermediate moisture meat dehydrated at 4°C after 10 days of storage at 25°C. No marked difference in the effect of dehydration on muscle was observed among species (beef, pork, chicken and rabbit). Results show that dehydration at low temperature (4°C) with use of the new dehydrating sheet enables intermediate moisture meat of good quality to be manufactured.