Dielectric behavior of beef meat in the 1-1500kHz range: Simulation with the Fricke/Cole-Cole model

The electrical properties of biological tissues have been researched for many years. Impedance measurements observed with increasing frequencies are mainly attributed to changes in membrane conductivity and ion and charged-molecule mobility (mainly Na⁺, K⁺, CL⁻ ions). Equivalent circuits with passive electrical components are frequently used as a support model for presentation and analyses of the behavior of tissues submitted to electrical fields. Fricke proposed an electrical model where the elements are resistive and capacitive. The model is composed of a resistive element (Rp) representing extracellular fluids (ECF) placed in parallel with a capacitive element (Cs) representing insulating membranes in series and a resistive element (Rs) representing intracellular fluids (ICF). This model is able to describe impedance measurements: at lower frequencies, most of the current flows around the cells without being able to penetrate them, while at higher frequencies the membranes lose their insulating properties and the current flows through both the extracellular and intracellular compartments. Since meat ageing induces structural change, particularly in membrane integrity, the insulating properties of membranes decrease, and intracellular and extracellular electrolytes mix, thus driving changes in their electrical properties. We report a method combining the Fricke and Cole–Cole models that was developed to monitor and explain tissues conductivity changes in preferential directions during beef meat ageing.     

Impact of carcass scalding and chilling on muscle proteins and meat quality of broiler breast fillets

The objective of this study was to determine the effects of broiler carcass scalding and chilling methods on meat quality and muscle proteins. During processing, carcasses were hard (60 °C, 1.5 min) or soft (52.8 °C, 3 min) scalded, and either immersion chilled (IC: 0.5 °C, 40 min) or air chilled (AC: 0.5 °C, 120 min). Breast fillets were deboned at 4 h postmortem and used for measuring meat quality and muscle protein characteristics. Scalding by chilling treatment interaction effects on meat quality were not observed. Air chilled carcasses had greater pH₂₄, and reduced drip loss and shear force compared to IC carcasses. Cook yield, color (L*a*b*), and moisture content were not different between chilling treatments. Scalding treatments did not influence quality traits. Sarcoplasmic protein solubility was not influenced by chilling treatment, but was greater in hard versus soft scalded carcasses. Myofibrillar protein solubility was greater in fillets from soft scalded IC carcasses. Alterations in the electrophoretic profiles of the myofibrillar and sarcoplasmic proteins due to treatments indicated minor changes in protein degradation and solubility. Data suggest that while only chilling method influenced meat quality, both scalding and chilling methods influenced protein solubility and degradation in breast fillets deboned 4 h postmortem.     

Effect of vitamin E supplementation on fatty acid composition of muscle and adipose tissues of indoor lambs with special attention on rumen-derived trans monounsaturated fatty acids

Thirty male lambs were assigned to one of 3 concentrate diets supplemented with 45 (E0), 286 (E1) or 551 (E2) mg/kg DM of dl-α-tocopheryl acetate to test the effect of vitamin E supplementation on muscle, caudal and perirenal fatty acid (FA) compositions. Specific attention was paid to C18:1 10t, usually observed in high proportions with high-starch or high-unsaturated FA diets. Vitamin E supplementation increased the α-tocopherol plasma concentrations of lambs. It did not modify lamb growth and slaughter parameters. Vitamin E supplementation did not modify FA composition in most tissues but it increased the C18:2 n − 6/C18:3 n − 3 ratio in muscle and adipose tissues of the E1 group compared to E0 and E2 groups. Vitamin E supplementation enhanced the C18:1 10t proportion in muscle and adipose tissues and it decreased the C18:2 9c,11t proportion in adipose tissues, especially in the E2 group. These changes may not be favourable for the nutritional value of lamb meat.     

The impact of homogenizer type and speed on the determination of myofibrillar fragmentation

The myofibrillar fragmentation index (MFI) was determined by the turbidity method on five samples of ovine Longissimus muscle, aged for either 1 or 5 days and processed from the frozen state over 3 weeks. These samples were homogenized at one of four speeds (11,000, 16,000, 19,000 or 22,000 rpm) with a shaft type homogenizer (Ystral) and at 15,000 rpm with a blade type homogenizer (Omni mixer). At all speeds except 15,000 or 22,000 rpm samples were homogenized for either one or two bursts of 30 s giving a total of eight different treatments. There was a significant interaction between ageing and treatment (P<0.05) and ageing and muscle sample (P<0.001). Regarding the Omni mixer result as a reference standard, the closest result from the Ystral homogenizer was obtained at 19,000 rpm after two bursts of 30 s. These two treatments gave similar mean values for samples aged 5 days. Repeatability between duplicates did not differ significantly for the various treatments (r=0.55). A large difference was found between samples aged for 1 and 5 days and the difference was greater for the Ystral homogenizer than the Omni mixer. The Omni mixer values for 1 day aged samples were 38 units less than for samples aged for 5 days while this difference for the Ystral homogenizer was 63 units. As speed of homogenization increased with the Ystral homogenizer the overall mean values increased and the values were always greater after two bursts of 30 s compared to one burst of 30 s. The results suggest that the Ystral homogenizer may be better for detecting differences between treatments than the Omni mixer.

At the slower speeds myofibrils consist of more sarcomeres and intermyofibril linkages could still be observed. This contrast was also seen between samples aged for 1 or 5 days with much greater degradation visually observed in the latter samples. This was supported by the quantitative data.     

Effect of moist or dry heat cooking procedures on carotenoid retention and colour of fillets of rainbow trout (Oncorhynchus mykiss) fed astaxanthin or canthaxanthin

Rainbow trout were pigmented with diets containing astaxanthin or canthaxanthin for 100 days, and then they were moist or dry heat-cooked. Fish fillet weight, fillet colour, and fillet biochemical contents (moisture, canthaxanthin and astaxanthin contents, and total lipid content) were analyzed. There was no significant effect of using astaxanthin or canthaxanthin on moisture, lipid or carotenoid contents of fish fillet. Giving astaxanthin or canthaxanthin to fish resulted in different hues; astaxanthin-fed fish yielded fillets that were visually more red than those of canthaxanthin-fed fish. The dry heat-cooking procedure showed the highest impact on the fillet colour. Carotenoid retention was affected by carotenoid source and cooking procedure. Canthaxanthin appeared more stable after heat processing than did astaxanthin.     

Double-band sarcomeric SHG pattern induced by adult skeletal muscles alteration during myofibrils preparation

To understand the reported difference between double band, sarcomeric second harmonic generation pattern of isolated myofibril and predominant single band pattern found in thick muscle tissues, we studied the effect of myofibril preparation on the second harmonic generation pattern. We found that double band sarcomeric second harmonic generation pattern usually observed in myofibrils (prepared from fresh tissue) is due to muscle alteration during the mixing and triton treatment processes. Single band sarcomeric second harmonic generation pattern could be observed in isolated myofibrils when this alteration is previously prevented using paraformaldehyd fixed tissue. We conclude that single band sarcomeric second harmonic generation pattern is a signature of adult muscle myofibrils in normal physiological condition, suggesting that sarcomeric second harmonic generation patterns could be used as a valuable diagnosis tool of muscle health.