Beef chops (longissimus dorsi) were pre-treated with 5% carbon monoxide (CO) − 95% N 2 for 24 h, vacuum packed in thermo-contractile bags and stored at 0 ± 2°C. Shelf life, as determined by the viable aerobic bacterial load, was 11 weeks. Vacuum-packed chops with heat-contractile fi lm produced a smaller drip loss, had a more intense red colour and higher colour stability under storage than chops with non-heat-contractile fi lm. Chops pre-treated with CO were redder during all the storage period than controls without CO. The pre-treatment did not affect pH, water-holding capacity, drip loss or rancidity of the meat stored in vacuum.
Abbreviations: TAN: total ammonia nitrogen TOC: total organic carbon VSS: volatile suspended solidsReported models of denitrification rates integrate in an unique parameter the pH-dependent inhibition by HNO 2 and the pH effect on the bacterial metabolic activity; furthermore, they do not quantify separately the pH effect on the nitrate and on the nitrite reduction *Corresponding author rates. The goal of this work was to quantify both effects on the kinetics of nitrate and nitrite reduction to improve the models' predictive value. Assays were performed at a pH range of 6.5-9.0 in batch reactors at 37ºC with an activated sludge. At the studied pH range
Sodium chloride affects the transformation rate of several compounds in bioreactors. Most authors report a decrease in microorganism activity at increasing salt concentrations. In this work, a kinetic model that relates sodium chloride concentration with the rates of each step of the nitrification process is proposed; thus, the effect of sodium chloride concentration (0 to 60 g/L) on the nitritation and nitratation rates was separately studied. To carry out the independent study of each step, a combination of the respirometric method with sodium azide, an inhibitor of the nitratation step, was performed. The dot-blot hybridization technique with 16S rRNA-targeted probes was used to determine the ammoniaoxidizing and nitrite-oxidizing bacterial fraction, then it was possible to relate the culture's function with its biological composition. Rates of both steps were linearly reduced at increasing salt concentrations; the nitratation rate was more affected than the nitritation rate. Simulations carried out in a nitrifying sequencing batch reactor indicate that nitrite might accumulate at high salt concentrations. Sodium chloride exerts a reversible inhibition on ammonia oxidation and nitrite oxidation. Water Environ. Res., 76, 73 (2004).ABSTRACT: Sodium chloride affects the transformation rate of several compounds in bioreactors. Most authors report a decrease in microorganism activity at increasing salt concentrations. In this work, a kinetic model that relates sodium chloride concentration with the rates of each step of the nitrification process is proposed; thus, the effect of sodium chloride concentration (0 to 60 g/L) on the nitritation and nitratation rates was separately studied. To carry out the independent study of each step, a combination of the respirometric method with sodium azide, an inhibitor of the nitratation step, was performed. The dot-blot hybridization technique with 16S rRNA-targeted probes was used to determine the ammoniaoxidizing and nitrite-oxidizing bacterial fraction, then it was possible to relate the culture's function with its biological composition. Rates of both steps were linearly reduced at increasing salt concentrations; the nitratation rate was more affected than the nitritation rate. Simulations carried out in a nitrifying sequencing batch reactor indicate that nitrite might accumulate at high salt concentrations. Sodium chloride exerts a reversible inhibition on ammonia oxidation and nitrite oxidation. Water Environ. Res., 76, 73 (2004).
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