Comparison of the color stability and lipid oxidative stability of fresh and vacuum packaged lamb muscle containing elevated omega-3 and omega-6 fatty acid levels from dietary manipulation.

A series of three experiments were conducted with second cross ([Merino×Border Leicester]×Poll Dorset) wether lambs to evaluate the effects of dietary treatments on manipulation of muscle long-chain (LC) omega-3 fatty acids (FA) on the color stability and oxidative stability of fresh and vacuum packaged lamb. At the end of 7-, 6- and 6-week experimental periods for experiments (Exp.) 1-3 respectively, lambs were slaughtered at a commercial abattoir. At 24 h post-mortem, muscle longissimus lumborum (LL) and longissimus thoracis (LT) were removed and evaluated for color and lipid oxidative stability under specified commercial storage and display condition. Of the dietary supplements used, fish meal and fish oil moderately (P<0.01) and markedly (P<0.001) increased muscle omega-3 FA content, while both protected canola seed (P<0.001) and protected sunflower meal protein significantly (P<0.02) increased muscle omega-6 FA content or ratio of omega-6/omega-3 of the longissimus muscle. In all experiments, the substantial increase (P<0.001) in muscle LC omega-3 and omega-6 FA had no consistent significant effect on color values (redness (a*), yellowness (b*) and lightness (L*)) for fresh and vacuum packaged lamb over a 6-day display period. Lipid oxidation, determined by the levels of thiobarbituric acid reactive substances (TBARS) indicated the enrichment of muscle polyunsaturated fatty acid (PUFA) levels in lambs did not produce significant differences resulting either from main treatment effects or for treatment×day×type interactions (where type was fresh and vacuum packaged). Present results demonstrated the color and lipid oxidative stability of lamb longissimus muscle during refrigerated display was not affected by enhanced levels of omega-3 and omega-6 FA due to dietary treatments.

The effect of ionic strength, polyphosphates type, pH, cooking temperature and preblending on the functional properties of normal and pale, soft, exudative (PSE) pork.

Compared to processed meat product made from normal pork, products made from pale soft exudative (PSE) pork have higher cook loss (CL) and weaker texture. In this study interactions between a range of processing conditions (ionic strength, polyphosphate addition, polyphosphate chain length, pH, cooking temperature and time between preparation and cooking), and their effect on the texture [shear stress (SS), true shear strain (TSS)] and CL of gels made from normal and PSE pork were examined. Of the processing conditions studied, ionic strength, polyphosphate addition and polyphosphate chain length affected the functional properties of normal and PSE pork differently. Generally, the functional properties of normal pork were superior to PSE pork, with no combination of conditions making all the functional properties of PSE pork equal to those of normal pork under the same conditions. The combination of conditions that was most effective in reducing the difference between normal and PSE pork was high ionic strength in the presence of added polyphosphate. Under these conditions there was no significant difference in CL between normal and PSE pork, although the texture (SS and TSS) of the PSE pork samples was still inferior.

A Simple, rapid preparative method for isolating and purifying oxymyoglobin.

A simple and rapid procedure was developed to isolate and purify preparative quantities (up to 200 mg) of reduced myoglobin (98% oxy) of high purity (>96%) from beef and pork muscles. This method involved fractional precipitation of a crude myoglobin extract with ammonium sulfate and purification with a single Chromatographic step on a Sephadex G-100 column. The metmyoglobin level of the myoglobin preparation was minimised by using muscle from freshly slaughtered animals (<48h post-mortem), trimming the muscle immediately before use to remove any oxidised myoglobin on the surface and carrying out all procedures at low temperature (0-5 °C) and alkaline pH (8.0-8.5). The purity of the myoglobin preparations was confirmed by ion exchange HPLC and SDS-polyacrylamide gel electrophoresis. The method was effective for skeletal muscle of both low myoglobin content (pork) and high myoglobin content (beef). The resulting purified myoglobin was very stable and there was little change in metmyoglobin level or autoxidation rate during 3 months' storage at 0 °C.

Plasma and muscle cortisol measurements as indicators of meat quality and stress in pigs.

Post-slaughter blood samples and muscle samples were collected from pigs slaughtered at the completion of a live-animal performance trial. There were two lines of pigs in which the halothane allele (n) was segregating. The lines were a lean line selected for rapid lean growth and an unselected fat line. There were homozygous normal (NN), homozygous halothane positive (nn) and heterozygous (Nn) genotypes in both lnes. Cortisol was measured in the plasma of the blood samples and in muscle juice obtained by high-speed centrifugation. Meat quality was assessed using pH, colour, fibre-optic probe, drip loss and cure yield measurements. Plasma cortisol concentrations in the fat line were significantly (P < 0·05) greater than thosein the lean line but concentrations did not differ significantly for the three halothane genotypes. Carcasses classified as dark, firm and dry (DFD) had significantly (P < 0·05) greater muscle cortisol concentrations than those classified as normal. Plasma and muscle cortisol concentrations of carcases classified as pale, soft and exudative (PSE) did not differ significantly from those classified as normal. Correlations between muscle cortisol and meat quality attributes were generally highly significant (r = 0·31 to r = 0·51, P < 0·001) There was a highly significant correlation (r = 0·73, P < 0·0001) between plasma and muscle cortisol concentrations.

The rate of metmyoglobin formation in beef, pork, and turkey meat as influenced by pH, sodium chloride, and sodium tripolyphosphate.

This study investigated the effects of pH (5·5 to 7·0), sodium chloride concentration (0·0-3·0%), and sodium tripolyphosphate concentration (0·0 and 0·5%) on the rate of metmyoglobin formation in ground beef, pork and turkey meat during refrigerated storage. Increasing the sodium chloride concentration produced a progressive increase in the rate of metmyoglobin formation in ground beef. Increasing the pH between pH 5·5 and 6·5 had no effect on the rate of metmyoglobin formation with ground beef and turkey meat, but produced a marked decrease between pH 6·5 and 7·0. In contrast pH had no consistent effect on the rate of metmyoglobin formation of ground pork and the rate of formation remained low at all pH levels. When ground beef contained 0·5% sodium tripolyphosphate, the effect of pH was reversed and the rate of metmyoglobin formation was lowest at pH 5·5, increased as the pH increased to 6·5 and then plateaued.

The effect of calcium carbonate and sodium alginate on the color and bind strength of restructured beef steaks.

This study investigated the effect of calcium carbonate concentration (0·00-0·26%) and sodium alginate concentration (0·0-1·4%) on the amount of discoloration and the raw and cooked bind-strength of restructured beef steaks. Alginate slightly increased and calcium carbonate markedly decreased the amount of discoloration in the restructured steaks. The protective effect of the calcium carbonate did not increase with increasing concentration and did not appear to be due to increased pH. The amount of discoloration in restructured steaks prepared with alginate was similar to that in conventionally prepared restructured steaks. The optimum concentration of calcium carbonate and alginate required for minimum discoloration and maximum raw and cooked bind-strength was 0·13% and 0·7%, respectively.

Techniques for measuring water-binding capacity in muscle foods-A review of methodology.

Many methods are available for measuring the WHC (water-holding capacity) of muscle and muscle products. However, not all WHC methods are suitable for a given application and use of an inappropriate method may lead to erroneous conclusions. This paper will first briefly describe the mechanism which immobilizes water in muscle foods, then review the methods currently used for measuring WHC of muscle foods and indicate suitable applications for each method.

The effect of cooking temperature on the functional properties of beef proteins: The role of ionic strength, pH, and pyrophosphate.

This study examined the effect of ionic strength (0·12 to 0·52), pH (5·50 and 6·00), pyrophosphate (PP) concentration (0 and 0·31%) and cooking temperature (52 to 87°C) on the cook yield (CY) and tensile strength (TS) of beef homogenates. Increasing the ionic strength, pH and pyrophosphate concentration increased the temperature at which cooking loss first occurred and decreased the temperature required for maximum TS. For most treatments, ionic strengths between 0·32 and 0·42 prevented cooking loss at all temperatures; the lower ionic strengths were required at the higher pH and PP concentration. Maximum TS occurred at 66°C for treatments that had no cooking loss between 60° and 75°C. For treatments that had cooking loss in this temperature range, TS increased linearly with increasing temperature; however, the TS values of these treatments were much lower than those in the former category. CY and TS were optimized by heating to 66°C. PP had a positive effect on both functional properties at ionic strengths >0·25 but a negative effect at ionic strengths <0·25.