Rigor Mortis Assessment of Atlantic Salmon (Salmo Salar) and Effects of Stress

The rigor mortis development of large Atlantic salmon was evaluated at a commercial plant using a sensory method, a mechanical rigorometer and low-frequency vibrations. The fish were classified according to rigor state using a neural network. Assessments were done with fish subjected to two different levels of handling stress prior to slaughter. White muscle high-energy phosphates and inosine monophosphate were used as indices of stress showing that handling stress may be considerable during commercial slaughter. Results indicate rigor assessment should be nondestructive and classificaton of rigor state was possible using a lowfrequency vibration method combined with a neural network.     

The Effect of Stunning Methods and Season on Muscle Texture Hardness in Atlantic Salmon (Salmo salar L.)

Commercially collected records of Atlantic salmon (Salmo salar L.) muscle texture hardness were used to evaluate the effect of slaughter procedures and seasonality on texture quality. A database collected by Marine Harvest® contained flesh hardness records of Atlantic salmon slaughtered at processing plants in Norway from summer 2010 to summer 2011. The fish were slaughtered either by (1) percussion followed by automated bleeding (“Percussive”) or (2) live chilling with exposure to carbon dioxide (CO₂) followed by manual severing gill arches and bleeding (“CO₂”) or (3) live chilling with exposure to CO₂ followed by percussive stunning and at the end automated bleeding (“CO₂·percussive”). Hardness in salmon muscle cutlets was measured in Newtons (N) by Materials Testing Machine Zwick 500N. The hardness in salmon varied significantly over the study period (P < 0.05, mixed effect model) and showed the softest value of 21.2 (± 0.7) Newton (N) in summer 2011 and hardest 24.1 (± 0.2) N in autumn 2010. Slaughter procedures had a significant effect on salmon muscle hardness (P < 0.05, mixed effect model), where percussion followed by automated bleeding resulted in the hardest value (24.0 ± 0.4 N) as compared with CO₂ stunning (21.8 ± 0.2 N) and combination of CO₂ and percussive stunning (23.1 ± 0.15 N). CO₂ is suspected as a causal factor in accelerated postmortem softening of the salmon muscle.     

Video Analysis to Monitor Rigor Mortis in Cultured Gulf of Mexico Sturgeon (Ancipenser oxyrynchus desotoi)

ABSTRACT: A subjective method was used to evaluate rigor mortis in 50 Gulf sturgeons distributed into 5 weight categories. Duration of rigor increased with fish weight. Onset of rigor ranged from 12 to 24 h. A new method to determine onset and resolution of rigor in cultured Gulf sturgeon was studied using analysis of video images. Insight on the progress of rigor through the fish body is provided. In 10 different time intervals from 0 to 67 h after death, fish were temporarily secured to the edge of a table by the head, with the body free to droop, and video images were taken. Rulers in the background allowed quantification of body position. The extent of deflection of various points along the body length was analyzed. New parameters based on maximum deflection and integral deflections were developed. Rigor in Gulf sturgeon took an average of 24 h to onset and 67 h to resolve and was not a uniform process: the tail reached maximum rigor later than the middle of the fish.     

Relating Sensory and Instrumental Texture Analyses of Atlantic Salmon

Sensory‐evaluated hardness of smoked Atlantic salmon (Salmo salar L.) was correlated with various response variables from instrumental texture analysis of raw or smoked cutlets (25 mm thick) using 4 different probes: 12.5‐ and 23‐ mm‐dia cylinders, a Warner‐Bratzler blade, and a 25.4‐mm‐dia sphere. Sensory hardness correlated significantly with analyses using all mechanical methods, but it was most accurately predicted by the 12.5‐mm‐dia cylinder in raw salmon (force and area at 90% compression; r = 0.70, P < 0.0001), and by the 23‐mm‐dia cylinder in smoked salmon (force at 90% compression and the area from origo to the 1st significant break; r = 0.63 to 0.64, P < 0.0001).     

Injection‐Salting and Cold‐Smoking of Farmed Atlantic Cod (Gadus morhua L.) and Atlantic Salmon (Salmo salar L.) at Different Stages of Rigor Mortis: Effect on Physical Properties

ABSTRACT: Processing of fish is generally conducted postrigor, but prerigor processing is associated with some potential advantages. The aim of this study was to study how 5 processing regimes of cold‐smoked cod and salmon conducted at different stages of rigor influenced yield, fillet shrinkage, and gaping. Farmed cod and salmon was filleted, salted by brine injection of 25% NaCl, and smoked for 2 h at different stages of rigor. Filleting and salting prerigor resulted in increased fillet shrinkage and less increase in weight during brine injection, which in turn was correlated to the salt content of the fillet. These effects were more pronounced in cod fillets when compared to salmon. Early processing reduced fillet gaping and fillets were evaluated as having a firmer texture. In a follow‐up trial with cod, shrinkage and weight gain during injection was studied as an effect of processing time postmortem. No changes in weight gain were observed for fillets salted the first 24 h postmortem; however, by delaying the processing 12 h postmortem, the high and rapid shrinking of cod fillets during brine injection was halved.     

Salmon Fillet Texture is Determined by Myofiber-Myofiber and Myofiber-Myocommata Attachment

ABSTRACT: Atlantic salmon ( Salmo salar ) fillets were stored on ice for a maximum of 14 d to determine which muscle structures are associated with changes in texture and rigor. Texture was measured as shear force and the changes correlated with structural alterations. Texture decreased significantly within 24 h in parallel with loss of attachment of muscle fibers. Loss of rigor stiffness by 5 d was associated with myofiber detachment from the myocommata. These results show that fillet texture depends on several distinct structures and events, initially including breaks in the cell cytoskeleton and loss of fiber-fiber attachment and later breaks in the connective tissue and fiber detachment from the myocommata.     

Injection-salting of pre rigor fillets of Atlantic salmon (Salmo salar)

ABSTRACT:  The effects of temperature (−1, 4, and 10 °C), brine concentration (12% and 25% NaCl), injection volumes, and needle densities were investigated on fillet weight gain (%), salt content (%), fillet contraction (%), and muscle gaping in pre rigor brine-injected fillets of Atlantic salmon ( Salmo salar ). Increased brine concentration (12% to 25%) significantly increased the initial (< 5 min after injection) and final contraction (24 h after injection) of pre rigor fillets. Increased brine concentration significantly reduced weight gain and increased salt content but had no significant effect on muscle gaping. The temperatures tested did not significantly affect weight gain, fillet contraction, or gaping score. Significant regressions ( P < 0.01) between the injection volume and weight gain (range: 2.5% to 15.5%) and salt content (range: 1.7% to 6.5%) were observed for injections of pre rigor fillets. Double injections significantly increased the weight gain and salt content compared to single injections. Initial fillet contraction measured 30 min after brine injection increased significantly ( P < 0.01) with increasing brine injection volume but no significant difference in the fillet contraction was observed 12 h after brine injection (range: 7.9% to 8.9%). Brine-injected post rigor control fillets obtained higher weight gain, higher salt content, more muscle gaping, and significantly lower fillet contraction compared to the pre rigor injected fillets.
Injection-salting is an applicable technology as a means to obtain satisfactory salt contents and homogenously distribute the salt into the muscle of pre rigor fillets of Atlantic salmon before further processing steps such as drying and smoking.     

Computer vision-based evaluation of pre- and postrigor changes in size and shape of Atlantic cod (Gadus morhua) and Atlantic salmon (Salmo salar) fillets during rigor mortis and ice storage: effects of perimortem handling stress

The present study describes the possibilities for using computer vision-based methods for the detection and monitoring of transient 2D and 3D changes in the geometry of a given product. The rigor contractions of unstressed and stressed fillets of Atlantic salmon (Salmo salar) and Atlantic cod (Gadus morhua) were used as a model system. Gradual changes in fillet shape and size (area, length, width, and roundness) were recorded for 7 and 3 d, respectively. Also, changes in fillet area and height (cross-section profiles) were tracked using a laser beam and a 3D digital camera. Another goal was to compare rigor developments of the 2 species of farmed fish, and whether perimortem stress affected the appearance of the fillets. Some significant changes in fillet size and shape were found (length, width, area, roundness, height) between unstressed and stressed fish during the course of rigor mortis as well as after ice storage (postrigor). However, the observed irreversible stress-related changes were small and would hardly mean anything for postrigor fish processors or consumers. The cod were less stressed (as defined by muscle biochemistry) than the salmon after the 2 species had been subjected to similar stress bouts. Consequently, the difference between the rigor courses of unstressed and stressed fish was more extreme in the case of salmon. However, the maximal whole fish rigor strength was judged to be about the same for both species. Moreover, the reductions in fillet area and length, as well as the increases in width, were basically of similar magnitude for both species. In fact, the increases in fillet roundness and cross-section height were larger for the cod. We conclude that the computer vision method can be used effectively for automated monitoring of changes in 2D and 3D shape and size of fish fillets during rigor mortis and ice storage. In addition, it can be used for grading of fillets according to uniformity in size and shape, as well as measurement of fillet yield measured in thickness. The methods are accurate, rapid, nondestructive, and contact-free and can therefore be regarded as suitable for industrial purposes.     

Study of the quality characteristics in cold-smoked salmon (Salmo salar) originating from pre- or post-rigor raw material

Improved slaughtering procedures in the salmon industry have caused a delayed onset of rigor mortis and, thus, a potential for pre-rigor secondary processing. The aim of this study was to investigate the effect of rigor status at time of processing on quality traits color, texture, sensory, microbiological, in injection salted, and cold-smoked Atlantic salmon (Salmo salar). Injection of pre-rigor fillets caused a significant (P<0.001) contraction (-7.9%± 0.9%) on the caudal-cranial axis. No significant differences in instrumental color (a*, b*, C*, or h*), texture (hardness), or sensory traits (aroma, color, taste, and texture) were observed between pre- or post-rigor processed fillets; however, post-rigor (1477 ± 38 g) fillets had a significant (P>0.05) higher fracturability than pre-rigor fillets (1369 ± 71 g). Pre-rigor fillets were significantly (P<0.01) lighter, L*, (39.7 ± 1.0) than post-rigor fillets (37.8 ± 0.8) and had significantly lower (P<0.05) aerobic plate count (APC), 1.4 ± 0.4 log CFU/g against 2.6 ± 0.6 log CFU/g, and psychrotrophic count (PC), 2.1 ± 0.2 log CFU/g against 3.0 ± 0.5 log CFU/g, than post-rigor processed fillets. This study showed that similar quality characteristics can be obtained in cold-smoked products processed either pre- or post-rigor when using suitable injection salting protocols and smoking techniques.     

Rigor Contractions in "Rested" and "Partially Exercised" Chinook Salmon White Muscle as Affected by Temperature

Time lapse video was used to determine the effects of temperature and fatigue on the development of rigor contractions in chinooksalmon ( Oncorhynchus tshawytscha ) white muscle. Minimal handling and chemical anaesthesia (AQUI-STM) produced rested fish. After removal of one fillet from the rested fish, post-mortem electrical stimulation of the carcass was used to partially exercise the remaining muscle. Specific strips of rested and partially exercised muscle were held in physiological saline at 0,4,6,8 and 12°C. Contraction onset and end were delayed by decreasing temperature in the rested treatment, but were unaffected in the partially exercised treatment. The final contracted length was affected by fatigue state and temperature.     

Effect of Modified Atmosphere Packaging and Superchilled Storage on the Microbial and Sensory Quality of Atlantic Salmon (Salmo salar) Fillets

ABSTRACT: Fresh Atlantic salmon fillets packaged under modified atmosphere (MA) (CO²:N² 60:40) and air was stored at superchilled (-2 °C) and chilled (+4 °C) temperatures. Changes in sensory scores, microbial growth, headspace gas composition, water loss, and pH were monitored during 24 d of storage. The superchilled MA packaged salmon maintained a good quality, with negligible microbial growth (<1000 colony-forming units [CFU]/g) for more than 24 d based on both sensory and microbial analyses (aerobic plate count, H2S-producing, and psychrotrophic bacteria). Superchilled salmon in air had a 21-d sensory shelf life, whereas MA and air-stored fillets at chilled conditions was spoiled after 10 d and 7 d, respectively.     

The texture of Atlantic salmon (Salmo salar) muscle as measured instrumentally using TPA and Warner–Brazler shear test

Muscle texture measurements were performed on Atlantic salmon (Salmo salar) using two different instrumental methods; The Texture Profile Analysis, which is a uniaxial compression test, and the Warner–Brazler shear test. The performances of the two tests were evaluated as to their ability to differentiate between recently killed salmon and salmon stored on ice for up to 24 days. Both tests performed well, but the shear test was slightly more sensitive than the compression test. Further, salmon were either starved or fed for two weeks prior to slaughter. The muscle from fed salmon lost its strength slightly faster than that from starved salmon, but this difference was only detectable during the first two days of chilled storage. The effects of temperature, fish size and degree and mode of deformation on the instrumental test results were studied and were found to be significant. Also, the sample geometry, ie the thickness of the fillet was found to have a very significant effect on the TPA-test results. © 1999 Society of Chemical Industry     

Atlantic salmon skin and fillet color changes effected by perimortem handling stress, rigor mortis, and ice storage

ABSTRACT:  The changes in skin and fillet color of anesthetized and exhausted Atlantic salmon were determined immediately after killing, during rigor mortis, and after ice storage for 7 d. Skin color (CIE L *, a *, b *, and related values) was determined by a Minolta Chroma Meter. Roche Salmo Fan™ Lineal and Roche Color Card values were determined by a computer vision method and a sensory panel. Before color assessment, the stress levels of the 2 fish groups were characterized in terms of white muscle parameters (pH, rigor mortis, and core temperature). The results showed that perimortem handling stress initially significantly affected several color parameters of skin and fillets. Significant transient fillet color changes also occurred in the prerigor phase and during the development of rigor mortis. Our results suggested that fillet color was affected by postmortem glycolysis (pH drop, particularly in anesthetized fillets), then by onset and development of rigor mortis. The color change patterns during storage were different for the 2 groups of fish. The computer vision method was considered suitable for automated (online) quality control and grading of salmonid fillets according to color.     

Product Yield and Gaping in Cold-smoked Atlantic Salmon (Salmo salar) Fillets as Influenced by Different Injection-salting Techniques

Product yield and fillet gaping severity were determined in cold‐smoked Atlantic salmon fillets subjected to injection‐salting. Effects of process parameter settings (brine injection pressure, number of repeated injections, needle speed, injection of brine in 1 or 2 directions, and chilled fillet resting before smoking) were tested. Repeated injections increased the yield up to 5.3% (wt/wt). Increasing injection pressure significantly increased the severity of fillet gaping in smoked fillets by 18%. Brine injection directions or needle speed did not affect smoking yield. The stability of the injection system was high. The results show that choice of process parameter settings during injection‐salting affects product yield after smoking.     

冷却方式对黄羽肉鸡胴体僵直进程与品质的影响

以黄羽肉鸡为研究对象,探讨宰后肉鸡胴体自来水降温至25 ℃、冰水浸泡冷却及冰水浸泡结合低温冷风的混合冷却对肉鸡僵直进程和鸡肉品质的影响。结果表明：鲜光鸡肌糖原酵解产生乳酸的速度较快,导致肉的pH值快速降低,4 h左右即进入僵直期。冰鲜鸡在4 ℃下储藏,低温减缓了肌糖原酵解产生乳酸及pH值降低的速度,低温对延缓肉鸡进入僵直期有明显效果。鲜光鸡弹性的降速及降幅显著大于（p<0.05）冰鲜鸡;混合冷却在储藏后期,弹性略优于（p>0.05）冰水直接冷却。在储藏过程中,胸肉的剪切力下降的速率和幅度明显高于腿肉,特别是鲜光鸡胸肉由0 h的59.55±2.71 N/mm2降至4 h的36.73±1.61 N/mm2,腿肉的剪切力变化相对较小。鲜光鸡胸肉及腿肉中可溶性蛋白含量显著高于（p<0.05）冰鲜鸡样品,混合冷却略高于水冷样品。因此,冰水浸泡冷却是导致鸡肉中可溶性蛋白损失和冰鲜鸡滋味逊于鲜光鸡的主要原因。     

Proteolytic Activity in Muscle from Atlantic Salmon (Salmo salar)

The maximum proteolytic activity appeared in the neutral to slightly alkaline pH range. Heat-stable alkaline proteases were detected. Optimal activity was found at pH 8 and 65°C. The activity dropped off markedly below 60°C and above 70°C. Preincubation of the muscle-extract for about 10 min at 65°C stimulated the activity. Salmon muscle was especially susceptible to proteolytic degradation at elevated temperatures. No notable differences were detected in proteolytic activities of Atlantic salmon in the feeding stage (superior quality) and in the sexually mature stage.     

Tocopherol Deposition in the Muscle of Atlantic Salmon (Salmo salar)

The deposition of four tocopherols (α, β, γ and δ) was studied in the muscle of Atlantic salmon (Salmo salar) smolts reared in seawater. γ-Tocopherol was deposited in proportion to the a-tocopherol content of the diet when both were added to the diet in a natural mixture. Both δ- and β-tocopherols were deposited in the muscle to a lesser extent than the a and γ forms. An equilibrium among tocopherols in muscle was reached in 15 wk.     

Postmortem Changes of Cultivated Atlantic Salmon and Their Effects on Salt Uptake

Rigor mortis of cultivated Atlantic salmon (Salmo salar) began to set in 8h after death and was fully resolved 60–70h after death during storage at 0°C. Maximum muscle contraction was observed 24–30h after death. ATP content decreased from 7.25 to 0.14 to 0.09 μmol/g fish from pre-rigor mortis to in-rigor mortis to post-rigor mortis state. The inosine and hypoxanthine contents increased from 0 to 1.20 to 4.06 μmol/ g fish and from 0.08 to 0.33 to 0.84 μmol/g fish during 60h storage, respectively, during 60h of storage at 0°C. Postmortem changes affected salt uptake. The equilibrium salt concentrations of pre-rigor, in-rigor and post-rigor mortis salmon were 0.53, 0.66 and 0.75 g/g salt-free solids, respectively, in a 20% (w/v) sodium chloride solution at 10°C.     

致晕方式对黄羽肉鸡品质的影响

以90日龄的黄羽肉鸡为研究对象,对比二氧化碳(CO2)致晕、电击致晕、不致晕(直接屠宰)3种处理方式对黄羽肉鸡品质的影响.结果表明:CO2致晕组的胴体损伤最小,肌肉僵直进程缩短,沥血量增加,pH值下降速率较快,与其他2组均差异显著(P<0.05);宰后45?min?CO2致晕组的亮度值(L*)、红度值(a*)及黄度值(...