Mechanisms of water-holding capacity of meat: The role of postmortem biochemical and structural changes

The feasibility of estimating and imaging the mechanical behavior of poroelastic materials using axial strain elastography

In this paper, we have investigated the feasibility of imaging the mechanical behavior of poroelastic materials using axial strain elastography. Cylindrical samples obtained from poroelastic materials having different elastic and permeability properties were subjected to a constant compression force (a classical creep experiment), during which poroelastographic data were acquired. For comparison, we also tested a few gelatin phantoms and non-homogeneous poroelastic phantoms constructed by combining different poroelastic materials. From the acquired data, we generated time-dependent sequences of axial strain elastograms and effective Poisson's ratio elastograms, which were then used for generating axial strain and effective Poisson's ratio time-constant elastograms. Thereafter, the various poroelastographic images were analyzed to evaluate the presence of statistically significant differences among the two types of poroelastic samples and for image quality analysis. The results of this study demonstrate that it is technically feasible to use axial strain elastography to distinguish among homogeneous poroelastic materials characterized by different elastic and permeability properties. They also show that the use of axial strain elastography instead of effective Poisson's ratio elastography results in objectively higher quality poroelastograms of the temporal behavior of the poroelastic materials under loading. However, the use of effective Poisson's ratio elastography may in any case be required to verify that the temporal changes occurring in the axial strains of the homogeneous poroelastic samples are also accompanied by temporal changes of the effective Poisson's ratios and are therefore due to poroelastic behavior.

Effect of different stunning systems on meat quality of light lamb

The present study was proposed to compare the effect that different types of stunning (TS) had on the quality of refrigerated meat from light lambs of the Spanish Manchega breed at 24h and 7 days post-mortem. Lambs were electrically stunned (ESL; n=10), using CO(2) (GSL; n=10) or slaughtered without previous stunning (USL; n=10). Measurements on meat quality were carried out by evaluating pH, colour coordinates (L(∗), a(∗), b(∗)), water holding capacity (WHC), cooking loss (CL), shear force (SF) and drip loss (DL). At 24h post-mortem, no significant differences were found in any of the variables studied. However, at 7 days post-mortem, meat quality was affected by the different TS: pH, CL and DL were lower (P<0.001) in the USL group and GSL obtained the lowest a(∗) (redness) and b(∗) (yellowness) values (P<0.01) than in the other groups. Ageing of meat affected SF in the ESL group (P<0.01), although there were no significant differences due to treatments at any of the ageing times.

Some qualitative and chromatic aspects of thawed buffalo (Bubalus bubalis) meat

After thawing, the meat of beef calves (Italian Frisian breed) and buffalo calves (Mediterranean breed) slaughtered at 4, 8 and 12 months of age was examined. Both the pH and the thawing loss confirmed that the meat of buffalo calves is more suitable for preservation by freezing. With increased age and time of exposure to air the lightness of the non-renewed surface was reduced. The lightness of the fresh cut surface remained stable in the various thawing phases though it was less in the older animals. The a(∗) index increased with animal age but decreased during the 4 days post-thawing. The fresh cut surface of buffalo meat from calves slaughtered at 4 and 8 months was not darker than beef slaughtered at the same age. On the contrary at 12 months of age, the buffalo meat had a lower redness index than beef and a higher haematin concentration.

Changes in the histochemical properties and meat quality traits of porcine muscles during the growing-finishing period as affected by feed restriction, slaughter age, or slaughter weight

In this study, the degree of contractile and metabolic development of myofibers in porcine LM, rectus femoris (RF), and dark and light portions of the semitendinosus (STD and STL, respectively) was determined, and their impact on meat quality was compared at the same age but different BW (trial 1) or at a given BW but different age (trial 2) in 48 Swiss Large White barrows from 12 litters after the growing and finishing period. The barrows had ad libitum (A) or restricted (R, 80% of A) feed access. In trial 1, at 113 and 154 d of age, 6 barrows in treatment A (62.1 and 99.5 kg of BW, respectively) and 6 siblings in treatment R (51.0 and 86.6 kg of BW, respectively) were slaughtered. In trial 2, a similar protocol was used except that the barrows were slaughtered at 61.3 (104 or 119 d of age, respectively) or 101.3 kg of BW (145 or 167 d of age, respectively). Muscle fibers were stained and classified as slow oxidative (SO), fast oxidative-glycolytic (FOG), or fast glycolytic (FG), and fiber area and distribution were determined. At 113 and 154 d of age, R barrows had smaller (P < or = 0.04) SO fibers in the LM, STD, and STL, smaller (P < 0.01) FOG fibers in the STL, smaller (P = 0.03) FG fibers in the LM, and smaller (P < or = 0.04) overall mean area in the LM, STD, and STL. In the STL and RF, R barrows had fewer (P < or = 0.06) FG and more (P < or = 0.08) FOG fibers than A barrows at 113 and 154 d of age. Except for smaller FOG fibers in the STD of R compared with A barrows slaughtered at the same BW, the myofiber size did not differ (P > or = 0.11). However, the LM tended to have fewer (P = 0.06) SO and more (P < 0.01) FG fibers, and the STD had more (P < 0.01) FOG fibers in R barrows. Regardless of whether R barrows were slaughtered at the same age or the same BW as the A barrows, shear force values and cooking losses were greater (P < or = 0.08) in the STD and STL of R barrows. These findings revealed that myofiber hypertrophy was impaired by feed restriction in barrows compared at the same age, but differences in myofiber size vanished at the same BW. By contrast, restricted nutrient supply affected myofiber maturation depending on the age and BW, but the impact differed between muscles. The absence of changes in myofiber type distribution among the younger-lighter and older-heavier barrows indicated that myofiber maturation was already completed in the younger-lighter barrows. Although changes in meat quality traits were affected by the feeding regimen, they were not related to myofiber characteristics.

The effect of post-mortem ageing and heating on water retention in bovine muscles

The muscles semitendinosus (ST) and psoas major (PM) were removed from chilled young bull carcasses 24h after slaughter and stored at 4°C. At the 1st, 6th and 12th day of post-mortem ageing the chemical composition (moisture, fat, protein, collagen) and contents of free, immobilized and unfreezable water in the muscles were estimated. The muscle steaks were boiled at 100°C, roasted at 170°C or fried at 160°C to an internal temperature of 75°C, and the amounts of total, free, immobilized, and unfreezable water in heated muscles were evaluated. The unfreezable water was estimated by DSC. In the raw muscles immobilized water constituted 74-75%, free water 16.6-17.6% and unfreezable water 7-8% of the total water. Independent of time of ageing, PM muscle contained significantly more free water than ST muscle. During post-mortem ageing, changes in free, immobilized and unfreezable water in muscles were not significant. The level of free water was highest in boiled and least in fried meat, however the amount of immobilized water was highest in fried and lowest in boiled meat. The amount of unfreezable water in muscles heated after 12 days of post-mortem ageing decreased.

Quantitative trait loci analysis of egg and meat production traits in a red junglefowl�נWhite Leghorn cross

Egg and production traits are of considerable economic importance in chickens. Using a White Leghorn x red junglefowl F(2) intercross, standard production measures of liver weight and colour, egg size, eggshell thickness, egg taste and meat quality were taken. A total of 160 markers covering 29 autosomes and the Z chromosome were genotyped on 175-243 individuals, depending on the trait under consideration. A total of nine significant quantitative trait loci (QTL) and three suggestive QTL were found on chicken chromosomes 1, 2, 4, 5, 7, 8, 10, 12, E47W24 and E22C19W28.

Influence of aging and salting on protein secondary structures and water distribution in uncooked and cooked pork. A combined FT-IR microspectroscopy and 1H NMR relaxometry study

Fourier transform infrared (FT-IR) microspectroscopy and low-field (LF) proton NMR transverse relaxation measurements were used to study the changes in protein secondary structure and water distribution as a consequence of aging (1 day and 14 days) followed by salting (3%, 6%, and 9% NaCl) and cooking (65 degrees C). An enhanced water uptake and increased proton NMR relaxation times after salting were observed in aged meat (14 days) compared with nonaged meat (1 day). FT-IR bands revealed that salting induced an increase in native beta-sheet structure while aging triggered an increase in native alpha-helical structure before cooking, which could explain the effects of aging and salting on water distribution and water uptake. Moreover, the decrease in T2 relaxation times and loss of water upon cooking were attributed to an increase in aggregated beta-sheet structures and a simultaneous decrease in native protein structures. Finally, aging increased the cooking loss and subsequently decreased the final yield, which corresponded to a further decrease in T2 relaxation times in aged meat upon cooking. However, salting weakened the effect of aging on the final yield, which is consistent with the increased T2 relaxation times upon salting for aged meat after cooking and the weaker effect of aging on protein secondary structural changes for samples treated with high salt concentration. The present study reveals that changes in water distribution during aging, salting, and cooking are not only due to the accepted causal connection, i.e., proteolytic degradation of myofibrillar structures, change in electrostatic repulsion, and dissolution and denaturation of proteins, but also dynamic changes in specific protein secondary structures.