Percorrer por autor "Muller, Alexandra"
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- Estudio de meta-análisis del efecto de estimulación eléctrica en la fuerza de corte de la carne de vacunoPublication . Xavier, Cristina; Gonzales-Barron, Ursula; Muller, Alexandra; Cadavez, VascoThe objective of this work was to use meta-analysis to estimate the effect size of the electrical stimulation on beef tenderness through the study of the measurements of shear force. Eight independent studies were used based on comparison of shear force measurements on the Longissimus dorsi and Longissimus lumborum in cattle carcasses subject to electrical stimulation and unstimulated carcasses. For each study, the mean effect size and standard error was calculated in order to apply a random-effects meta-analysis model. The meta-analysis demonstrated that the electrical stimulation on beef carcasses decreases the values of shear-force of meat by an average of 1.34 kgf. Thus, this study confirmed the positive effect of the electrical stimulation on the beef meat tenderness. However, the effect size displayed high variation among studies which can be attributed to differences in their experimental conditions.
- Modelling beef meat quality traits during ageing by early post-mortem pH decay descriptorsPublication . Xavier, Cristina; Gonzales-Barron, Ursula; Muller, Alexandra; Cadavez, VascoPrevious work has demonstrated that beef carcasses can be promptly and accurately classified into optimal quality and cold-shortened in accordance to the concept of pH/temperature ‘ideal window’ by using carcass characteristics and early post-mortem pH/temperature decay descriptors. The objective of this study was to assess the combined effects of the aforementioned variables on the two main eating quality attributes of meat – namely, tenderness (measured as shear force) and juiciness (measured as cooking loss) – during chill ageing. The pH and temperature in longissimus thoracis muscle of 51 beef carcasses were recorded during 24 h post-mortem, and decay descriptors were then obtained by fitting exponential models. Measures of Warner-Bratzler shear force and cooking loss were obtained from cooked meat after 3, 8 and 13 days of cold ageing. The fitted mixed-effect models revealed that both meat tenderisation and cooking loss increased with ageing (P<0.01) although their rates slowed down in time (P<0.05). Beef carcasses with a higher pH (obtained at different endpoints: 1.5, 3.0, 4.5 or 6.0 h post-mortem) produced aged meat with increased tenderness (P=0.013) and increased water retention during cooking (P=0.016) than those of lower pH. Nonetheless, the slower the pH decay rate, as happens in a cold-shortened carcass, the lower the potential for tenderisation (P=0.038) and water retention (P=0.050) during ageing. Whereas sex affected shear force, with females producing meat of higher tenderness, aged meat of increased water retention was produced by heavier beef carcasses (P<0.001). The good fitting quality of the shear force (R2=0.847) and cooking loss (R2=0.882) models and their similarity among the different endpoints post-mortem indicated that both eating quality attributes can be approached by recording the pH decline of a beef carcass during the first 3.0 hours after slaughter.
- Modelling the temperature and pH decline early post-mortem of beef carcassesPublication . Xavier, Cristina; Gonzales-Barron, Ursula; Cadavez, Vasco; Muller, AlexandraThe objective of this work was to model the pH and temperature decline early post-mortem on beef carcasses and to study the effect of gender, genotype and weight class on the pH and temperature decline patterns. A total of 24 beef animals slaughtered in a local abattoir were sampled. pH and temperature were recorded using an OMEGA wireless receiver/host (UWTC-RECl). The decline of pH and temperature was modelled using one parameterisation of the exponential decay function, and its parameters were estimated using the software R. The fitted models were used to predict p H and temperature at 1.5 h, at 3.0 h and at 24 h; the time when p H reached 6.0, and the temperature at which p H reached 6.0. The rate parameters of the exponential decay function for pH (KpH) and temperature (KT) were found to be independent (r=0.35, P>0.05). The correlation between p H at 3 h and final p H (at 24 h) was very high (r=0.930, P<0.01). The KT was influenced by the time elapsed from slaughter until the first recording, and by the carcass weight. In opposition, those variables did not affect the KpH, The exponential decay function was able to model the early post-mortem decline of both p H and temperature, and the pII at 3 hours can be used as predictor of the final pH of beef meat.