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Muscle pH (muscle + ph)
Selected AbstractsRelating Instrumental Texture, Determined by Variable-Blade and Allo-Kramer Shear Attachments, to Sensory Analysis of Rainbow Trout, Oncorhynchus mykiss, FilletsJOURNAL OF FOOD SCIENCE, Issue 7 2010Aunchalee Aussanasuwannakul Abstract:, Texture is one of the most important quality attributes of fish fillets, and accurate assessment of variation in this attribute, as affected by storage and handling, is critical in providing consistent quality product. Trout fillets received 4 treatments: 3-d refrigeration (R3), 7-d refrigeration (R7), 3-d refrigeration followed by 30-d frozen storage (R3F30), and 7-d refrigeration followed by 30-d frozen storage (R7F30). Instrumental texture of raw and cooked fillets was determined by 3 approaches: 5-blade Allo-Kramer (AK) and variable-blade (VB) attachment with 12 blades arranged in perpendicular (PER) and parallel (PAR) orientations to muscle fibers. Correlation between instrumental texture and sensory hardness, juiciness, elasticity, fatness, and coarseness was determined. Muscle pH remained constant at 6.54 to 6.64. Raw fillets lost 3.66% of their original weight after 30-d frozen storage. After cooking, weight loss further increased to 15.97%. Moisture content decreased from 69.11 to 65.02%, while fat content remained constant at 10.41%. VBPER detected differences in muscle sample strength (P= 0.0019) and demonstrated effect of shear direction reported as maximum force (g force/g sample). AKPER detected differences in energy of shear (g × mm; P= 0.0001). Fillets that received F30 treatments were less extensible. Cooking increased muscle strength and toughness. Force determined by VBPER was correlated with sensory hardness (r= 0.423, P= 0.0394) and cook loss (r= 0.412, P= 0.0450). VB attachment is accurate, valid, and less destructive in fillet texture analysis. Practical Application:, A new shearing device was validated with sensory analysis. Settings and parameters obtained could be used to define fillet texture quality associated with muscle fiber orientation. [source] Optimum Postmortem Chilled Storage Temperature for Summer and Winter Acclimated, Rested, Chinook Salmon (Oncorhynchus tshawytscha) White MuscleJOURNAL OF FOOD SCIENCE, Issue 5 2000A.R. Jerrett ABSTRACT Chemical anaesthesia (AQUI-STM) was used to harvest 2 groups of tank-reared chinook salmon (Oncorhynchus tshawytscha), naturally acclimated to summer (18.8 °C) and winter (10.7 and 12.4 °C) temperatures, in a "rested"state. Carcasses were stored in 35% seawater at temperatures between approximately 2 and 19 °C to investigate the effects of acclimation and storage temperature on the postmortem metabolic rate of rested epaxial white muscle tissue. Muscle pH, [lactate], and adenosine triphosphate/inosine monophosphate measurements made 20 h postharvest indicated that winter acclimated fish were 2.2 times more sensitive to temperature than summer fish. A 3rd group of winter acclimated fish, stored between ,1.2 and 6 °C, indicated that significant cold injury only occurred on freezing. [source] Quality of farmed Atlantic cod: effects of season and storageAQUACULTURE RESEARCH, Issue 8 2010Hilde Herland Abstract Farming of Atlantic cod makes it possible to supply cod throughout the year. The aim of this study was to investigate the effects of season and postmortem ice storage on the quality parameters of farmed cod. Farmed Atlantic cod were sampled from the same pen in the period February 2006,March 2007. Cod whole body and somatic weight, condition factors and hepatosomatic index were all affected by season, all decreasing during maturation and spawning in the winter. Muscle pH and water were influenced by season, increasing during maturation and spawning and then decreasing after spawning. Season also affected the colour of the fillet. There was a significant increase in whiteness post-spawning and a decrease during the second maturation. Water-holding capacity (WHC), levels of trimethylamine oxide and trimethylamine, as well as microbiological data, did not vary due to season. Muscle pH, water content, WHC and microbial counts increased during storage for all samplings. [source] FACTORS AFFECTING LIPID OXIDATION IN BREAST AND THIGH MUSCLE FROM CHICKEN, TURKEY AND DUCKJOURNAL OF FOOD BIOCHEMISTRY, Issue 4 2010Y. GONG ABSTRACT Lipid oxidation occurred rapidly in turkey muscle, intermediate in duck and slowest in chicken. pH was lowest in turkey muscle. Chicken muscle had a lower content of polyunsaturated fatty acids compared with turkey and duck muscles. The aqueous fraction of duck breast inhibited hemoglobin-mediated lipid oxidation in washed muscle more effectively than aqueous fractions from turkey and chicken muscle. ,-Tocopherol content was highest in duck muscle, intermediate in chicken and lowest in turkey. Depletion of tocopherols during frozen storage was more rapid in turkey and duck compared with chicken. It was thought that the elevated tocopherol level in chicken muscle may be caused by less efficient catabolism via the omega hydroxylation pathway. However, tocopherol hydroxylase activity was similar in chicken compared with turkey liver microsomes. Heme pigment content was around sixfold higher in duck breast compared with chicken and turkey breast. Duck thigh had especially elevated pH. PRACTICAL APPLICATIONS This work describes a number of factors that explain the wide variation in oxidative stability (chicken > duck > turkey) when comparing muscle tissues from the three avian species. These factors include muscle pH, concentration of heme pigments, fatty acid unsaturation, inhibitors of lipid oxidation in the aqueous fraction of the muscle, tocopherol content in lipid phases and depletion rates of tocopherol. These factors should be considered when developing strategies to inhibit lipid oxidation in muscle foods. The relatively high content of ,-tocopherol in chicken muscle compared with turkey should be a subject of further research to better understand the mechanisms by which certain animal species preferentially deposit the molecule into muscle. [source] IMPACT OF FREEZING TEMPERATURE ON QUALITY OF FARMED ATLANTIC COD (GADUS MORHUA L.)JOURNAL OF TEXTURE STUDIES, Issue 4 2007TURID MØRKØRE ABSTRACT This study evaluates the impact of freezing temperature (,10,,25,,40,,55 or,70C) on thaw exudates, liquid leakage during freeze-chilling, appearance, gaping and mechanical properties of farmed Atlantic cod fillets. Freezing temperature significantly influenced each of the characteristics studied. High temperatures (,10 and,25C) gave increased thaw exudates, and freezing at,10C gave the highest liquid leakage during freeze-chilling. Fillets frozen at,10C had the lowest gaping and the whitest appearance. The results indicated the highest degree of toughening upon freezing at,10 or,55C, whereas the degree of toughening appeared to be similar and lower for fillets frozen at,25,,40 or,70C. The impact of freezing temperatures on the quality of farmed cod therefore appeared to be complex, but no overall beneficial effects were found by decreasing the freezing temperature below,40C. PRACTICAL APPLICATIONS For the fish processing industry, it is important to define optimal freezing and frozen storage regimes that are cost efficient and at the same time preserve the fresh fillet quality. Farmed cod differ from their wild counterparts by having lower water content, lower muscle pH and thicker fillets. Hence, industrial guidelines for wild cod may not be transferable to farmed cod. This study showed no beneficial effects by decreasing the freezing temperature below ,40C. Freezing and frozen storage are usually separated commercially. Results from the present study give valuable contribution to future studies aiming at defining optimal combination of freezing and frozen storage temperatures for farmed Atlantic cod. [source] Preslaughter stress and subsequent effect on flesh quality in farmed codAQUACULTURE RESEARCH, Issue 10 2010Marit Bjørnevik Abstract The aim of this study was to investigate the effect of prehandling stress on the flesh quality of Atlantic cod (Gadus morhua). In order to stress the animal, water was reduced in the tank before a total of 30 fish were caught five at a time using a dipnet and held for 3 min, causing stress by hypoxia. This fish was compared with a control group (n=30) of fish exposed to anaesthetics directly in the tank. All fish were killed by a percussive blow to the head and exsanguinated and stored on ice before flesh quality was measured. Immediately after death and after ice storage for 3 and 8 days, 10 fish per group were measured for muscle pH, texture, fillet gaping, colour, drip loss and cathepsin D. Handling stress resulted in an initial increased fillet lightness, drip loss and decreased fillet shear force, although these differences did level off during ice storage. Stress caused by handling resulted in earlier onset of rigour mortis as compared with the control group, which reached maximum rigour tensions within 26 and 36 h postmortem respectively. We conclude that handling before harvest results in reduced time before entering rigour. After 8 days of ice storage, no effect of handling stress was seen on the muscle pH, flesh colour, fillet shear force, gaping score, drip loss or cathepsin D activity. [source] Electrical stunning of farmed Atlantic cod Gadus morhua L.: a comparison of an industrial and experimental methodAQUACULTURE RESEARCH, Issue 8 2010Hanne Digre Abstract An industrial and experimental electrical method for stunning farmed Atlantic cod in air and seawater (SW), respectively, were compared. The impacts of sedation with AQUI-SÔ and exercise to exhaustion before electrical stunning were also assessed to monitor the possible depletion of rested muscle energy levels by electrical stunning. Stress (blood glucose, haematocrit, muscle pH, muscle excitability, high-energy phosphates and rigor mortis) and flesh quality (fillet texture, colour, liquid leakage (LL), gaping, residual blood and K -value) were assessed. For the industrial stunning method, an average of 41 V, 0.2 A dc was applied to individual cod for 18,27 s. For the SW method, a bipolar square wave current (170 Hz, 33% duty cycle) was applied for 5 s. After stunning, recovery was prevented by exsanguination in chilled SW. There were no differences (P>0.05) between the two stunning methods except for a higher ultimate fillet pH for cod stunned in air 8 days postmortem. Exercise before stunning depleted muscle energy levels at slaughter, increased LL and fillets had redder and darker flesh after storage on ice for 8 days. Electrical stunning (in air) of AQUI-SÔ -treated fish partly depleted muscle energy levels (pH 7.3, ATP 18.7 ,mol g,1, PCr 70.1 ,mol g,1). However, flesh quality was not affected. Unless pre-rigor filleting is the chosen processing strategy, electrical stunning of cod seems to be a promising stunning method. [source] | ||||||||||