Masters Theses

Date of Award

12-1998

Degree Type

Thesis

Degree Name

Master of Science

Major

Food Science and Technology

Major Professor

Riëtte van Laack

Committee Members

Dwight Loveday, Michael Smith

Abstract

The problem of Pale, Soft, Exudative (PSE) chicken has been recognized only recently. Although PSE in chicken seems linked to stress, it is unknown if this condition is comparable to PSE pork which occurs in stress susceptible pigs. In Experiment 1 of the study, 20 normal and 20 pale color chicken breasts were evaluated. Compared with normal meat, the pale (PSE) chicken had a significantly (P<0.05) lower pH (5.9 vs. 5.7), higher L*-value (55.1 vs. 60.0), higher drip loss (0.87 vs. 1.33%), lower water-holding capacity (WHO, 44 vs. 31%), and lower cooking yield (106 vs. 96%). Differences in sarcomere length (1.77 vs. 1.72 pm) were small and insignificant. Protein solubility in PSE samples was slightly, but significantly, lower than in normal samples. Correlations between pH and L*-value (R = -0.76), pH and WHO (R = -0.65), and sarcoplasmic protein and L*-value (R = -0.71) were significant. Correlations between protein solubility and WHC were not significant.

Experiment 2, 3, 4, 5, utilizing a total of 195 commercial male broilers, were conducted to evaluate if a rapid change in pre-slaughter environmental temperature results in PSE quality. In Experiment 2, heat-stressed broilers were kept in a temperature-controlled chamber, in which temperature increased from 23.9 to 35 C within 3 h. In Experiment 3,4 and 5, the temperature was increased to 36.1 °C instead of 35°C. In Experiment 4 and 5, additional stress was imposed by chasing chicken on the floor for 10 min before catching. The heat-stressed birds were caught and kept in the crate for an additional hour before slaughter in order to simulate a commercial environment. For each experiment the control group was kept at 23.9°C. Breast muscles were excised at 8 h post-mortem and stored at 0-2 °C. At 24 h post-mortem, the quality characteristics pH, color (L*), and water-holding capacity, were assessed. In Experiment 2, heat stress did not affect any of the meat quality characteristics. In Experiment 3, heat stress resulted In significantly (P<0.05) higher L*-values (59.8 vs. 58.3), lower water-holding capacity (WHC, 36 vs. 52%), and lower cooking yield (CY, 99 vs. 111%). In Experiment 4 and 5, the sudden change In temperature and extra stress (chasing) did not affect quality. A low ultimate pH seems to be the main factor for the PSE phenomenon In chicken. Results of this study Indicate that under conditions of these experiments, temperature Is not the main cause of PSE. Other factors, such as genetics, may Interact or Interfere with the development of PSE broiler breast muscle under (temperature) stress conditions.

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