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NMR proton density imaging was used to study isothermal and unidirectional drying of pork semi membranosus muscle samples at temperatures of 12, 16 and 20 °C. An independent calibration of the transversal relaxation time T(2) as a function of the moisture content was carried out to convert the signal amplitude into moisture content. Due to spatial heterogeneity in drying, 2D images were needed to assess the evolution of 1D moisture profiles. The relationship between the effective water diffusivity (D) was calculated in function of water content (X) using the Boltzman transformation which needs no a priori on the relationship D=f(X); the effect of lipid content, temperature and fibre direction on this relationship were also studied. In all cases a decrease in water content brought about a decrease in D. A slight increase in lipid content led to a dramatic decrease in D. The fibre direction relative to water movement had a negligible effect. No significative differences in D between the three temperatures were observed, due to variability in the chemical composition of the samples.

Rabbit triceps brachii muscle was perfused with bovine red cells medium. Changes in phosphorus compounds and intracellular pH were followed using (31)P NMR during 15 min in the perfused muscle and during 50 min in muscle made anoxic by perfusion stop. Potassium levels in perfusate was maintained at 4 mM (normal plasma concentration at rest) during all perfusion in one muscle and at 4 mM for 10 min then 10 mM during 5 min before perfusion stop in the contralateral muscle. The intracellular pH and phosphorylated compounds content remained stable in the perfused muscle whatever the potassium concentration of the perfusate. Five min after perfusion stop a decrease in phosphocreatine (P<0.05) and pH (P<0.01) and an increase in sugar-phosphates (P<0.01) were observed independently of potassium concentration. The lack of effect of increasing circulating potassium indicates that hyperkalemia does not affect, by itself the muscles energetic metabolism.

Phosphorus nuclear magnetic resonance ((31)P NMR) measurements were made on biopsy samples from pig muscles. Two experiments were performed, one in France and one in Czechoslovakia. In experiment 1, the muscle samples were obtained by surgery from the Biceps femoris muscle of 10 pigs with various genetic types (5 Large White, 1 Large White × Landrace, 4 Pietrains). In experiment 2, the muscle samples were obtained by shot biopsy from the Longissimus dorsi muscle of 11 Belgian Landrace × Duroc pigs, of which 6 were halothane-negative and 5 halothane-positive. The pigs were slaughtered by electrostunning and exsanguination respectively 3 weeks and 1 week after the biopsy, and meat quality traits (pH(1), reflectance and water holding capacity) were determined. The changes in adenosine triphosphate (ATP), creatine phosphate (CP), inorganic phosphate (P(i)) and pH, as deduced from NMR, were faster in Pietrains than in Large Whites, and in halothane-positive than in halothane-negative pigs. The value of the CP/P(i) ratio at 40 min after taking biopsy allowed discrimination between halothane-positive and halothane-negative pigs. The values of pH, creatine phosphate and adenosine triphosphate, as measured at definite times on the biopsies, were correlated with the rate of post-mortem metabolism (r approx 0·8) and with meat quality traits. (31)P NMR measurements combined with a rapid and efficient biopsy technique appear as an alternative tool for assessment of both halothane sensitivity and prediction of meat quality in pigs., (Copyright © 1993. Published by Elsevier Ltd.)

The rate and the extent of post mortem pH changes in pig muscle largely determine pork quality. Fast pH fall combined with low ultimate pH leads to pale soft exudative (PSE) meat; high ultimate pH leads to dark firm dry (DFD) meat. Post mortem metabolism was studied in pig muscle using(31)P NMR. Fifteen pigs, i.e. 7 Large White pigs and 8 Pietrain pigs, were used. Five pigs of each breed were slaughtered, taking care to minimize preslaughter stress. The other pigs (3 Large Whites and 2 Pietrains) were injected with 0·1 mg adrenaline per kg liveweight before slaughter, in order to increase meat ultimate pH. All the animals were killed by electronarcosis and exsanguination. Three of the adrenaline-treated pigs (1 Large White and 2 Pietrains) gave meat with ultimate pH above 6 (DFD meat). The pigs with normal muscle ultimate pH, i.e. 6 Large Whites and 6 Pietrains, had very variable rates of post mortem muscle metabolism (pH at 30 min after slaughter: 6·17-6·85 in Large Whites; 6·04-6·23 in Pietrains). The relationships between pH and ATP changes were similar in all pigs showing normal muscle ultimate pH, whereas ATP disappeared at a high pH value (on average pH 6·4) in pigs with high ultimate pH. The course of post mortem biochemical changes in a given animal could be predicted rather well by examination of a single(31)P NMR spectrum obtained around 30 min after death. At this time, muscle with a low rate of metabolism simultaneously showed medium to high pH, high ATP content (4-6·8 μmol/g) and rather low Pi content (6-14 μmol/g); muscle with a fast rate of metabolism (PSE-prone muscle) had low pH, low to medium ATP content (1·1-4 μmol/g) and generally high phosphomonoester (PME) content (9-23 μmol/g); muscle with high ultimate pH (DFD-prone muscle) had high pH, low PME content (4-8 μmol/g) and high Pi content (22-27 μmol/g)., (Copyright © 1991. Published by Elsevier Ltd.)

An experimental system was designed to study as independently as possible the effects of various in-vivo or post-mortem factors susceptible to influence muscle metabolism. This system was made up of an NMR probe, a physiological stimulator, a perfusion system and a force monitoring device. Rabbit muscles were isolated and perfused with bovine red cells, then put into the NMR probe to follow the evolution of pH and phosphorylated compounds. It was possible to keep muscle metabolism stable for 2 h. Death was simulated by stopping the perfusion which allowed post-mortem changes to be followed. The effects of adrenaline perfusion or of a 5 s tetanus on some traits of metabolism and on changes following muscle death were studied. Tetanus immediately before perfusion was stopped accelerated changes in pH and in phosphocreatine and ATP contents; adrenaline perfusion during 30 min before perfusion was stopped had little effect on these traits., (Copyright © 1991. Published by Elsevier Ltd.)

Nuclear magnetic resonance measurements were made on pork samples from pigs of various genetic types (Large White, halothane positive and halothane-negative Pietrain) slaughtered either under minimal stress or somewhat stressful conditions. The (1)H spin-lattice (T(1)) and spin-spin (T(2)) relaxation times of water protons were recorded. The observed T(1) was single-exponential but a two-component T(2) relaxation behaviour (components referred to as T(2a) and T(2b)) was observed. Highly significant relationships were found between T(1) and all the meat characteristics studied. T(2a) was related only to ultimate pH and cooking loss, whereas T(2b) was more closely related to the rate of post-mortem pH fall and protein denaturation criteria., (Copyright © 1985. Published by Elsevier Ltd.)

The effects of combined oestradiol and trenbolone acetate implants have been investigated. Meat tenderness, juiciness and flavour were assessed by trained taste panelists and 16 variables related to muscle biochemistry and composition and ageing kinetics parameters were analysed on Longissimus dorsi and Triceps brachii caput longum muscles from 24 months old treated and control Charolais steers. Increases in carcass weight and mean daily weight gain, generally observed following such treatment, were confirmed. Furthermore, meat quality traits and ageing rate were significantly correlated with muscle typing parameters. Factorial discriminant analysis of data revealed that muscle typing (isomyosin 3 content) and composition (dry matter and lipid content) as well as NRM relaxation time of meat water (T2b) and ageing rate were the most affected by treatment. In addition, the hormone effect appeared to be muscle dependent., (Copyright © 1989. Published by Elsevier Ltd.)

(1)H-NMR has been used to study the evolution of water proton transversal relaxation times in ageing skeletal muscles of normal and halothane-positive Pietrain pigs. Malignant hyperthermia was confirmed by the caffeine contracture test. Lactic acid, creatine phosphate, and ATP levels in muscle biopsies were measured by biochemical analysis. The NMR dynamic results revealed malignant hyperthermia, but knowledge of animal age and muscle type improved significantly the detection ability. The NMR results revealed large differences between muscles. Halothane sensitivity detection seems to be less affected by animal age, than by muscle effect but discrimination was more efficient in the older animal group. It is concluded that (1) H-NMR is a suitable method for diagnosing halothane sensitivity on a well identified muscle biopsy and that water dynamics might be related to acidosis in muscle fibres., (Copyright © 1989. Published by Elsevier Ltd.)