Master of Science / Food Science Institute / Elizabeth Boyle / To evaluate the effect of extended post-harvest hanging time on pork sides and the microbial shelf-life of fabricated steaks, aerobic plate count (APC), Enterobacteriaceae (EB), yeast and mold populations, pH, and moisture content of pork sides hung for 21 days at 0±1°C was determined. After hanging, blade steaks fabricated from these sides were vacuum packaged, stored up to 35 days at 0±1°C, and evaluated for APC, EB, yeast and mold populations, and pH. Carcass cooler temperature and percent relative humidity, measured every hour during storage, averaged 0±1°C and 87.3% (66-100%), respectively. Pork carcass surface moisture content declined (P ≤ 0.05) from 65.1% on day 1 to 50.5% on day 21. The carcass pH was similar (P ≥ 0.05) at 5.88 on days 1, 7, and 14; however, by day 21 the pH declined (P ≤ 0.05) to 5.72. The flank, shoulder, and jowl were sampled on pork carcasses. There was no day effect for carcass APC; however, there was a location effect. The jowl had the highest (P ≤ 0.05) APC with 1.21 log CFU/cm². There was no carcass location or day effect for EB or mold populations, but there was a carcass location and day effect for yeast populations. The detection limit (DL) for EB and yeast and mold populations on pork carcass samples (n = 240) was 0.06 and 0.41 log CFU/cm² for the shoulder and flank, and jowl, respectively. For EB and mold populations, 98.8 and 97.9% of carcass samples, respectively, were below the DL. For yeast populations, 37.5, 45.0, and 63.8% were above the DL for flank, shoulder, and jowl, respectively. On days 1, 7, 14, and 21, 60.0, 55.0, 53.3 and 26.6% were above the DL, respectively, for carcass yeast populations; however, none were greater than 2.83 log CFU/cm². The pH of pork steaks was 5.69-5.89. There was a day effect for APC on pork steaks. The initial APC of steaks was 1.61 log CFU/g, increasing (P ≤ 0.05) to 5.06 log CFU/g on day 35. There was a day effect for EB and mold populations; but not for yeast populations. The DL for EB and yeast and mold populations on pork steaks (n = 102) was 0.70 log CFU/g. On days 0, 7, 14, 21, 28, and 35, the percent of EB populations above the DL on pork steaks were 0.0, 0.0, 23.5, 41.2, 94.1, 41.2%, respectively, however, none of the steak samples exceeded 4.40 log CFU/g. For mold populations, 100.0% of steaks were below the DL on days 0, 7, and 14. On days 21, 28, and 35, 18, 24, and 12%, respectively, were above the DL. None of the steak samples exceeded 2.68 log CFU/g for mold populations. For yeast populations, 56.8% of pork steaks samples were above the DL, but none were greater than 3.69 log CFU/g. These results indicate that pork carcasses and vacuum packaged shoulder blade steaks fabricated from these carcasses have acceptable quality for 21 and 35 days, respectively, when stored at 0±1°C after harvest.

Se estudió la influencia de la tecnología del sacrificio sobre la calidad de la canal y la carne porcinas. El trabajo consistió en estudiar minuciosamente todas las operaciones llevadas a cabo en un matadero industrial de gran capacidad, desde la recepción de los cerdos, hasta la obtención de la canal refrigerada, con el objeto de detectar y, en su caso, subsanar, posibles pérdidas de calidad que pudieran ser atribuibles a la tecnología empleada. Para ello, se valoró la importancia de aquellas operaciones que podrían jugar un papel relevante en la consecución de una mejor calidad, incluido el diseño de instalaciones, tales como zonas de descarga, corrales, salas de sacrificio y faenado y cámaras frigoríficas. El estudio fue realizado sobre 2047 cerdos de cebo procedentes de 36 granjas, realizando diferentes medidas y ensayos según las operaciones estudiadas. Se determinó el peso, magro y panículo adiposo de la canal, estableciéndose su clase comercial y conformación subjetiva. La temperatura de la canal fue estudiada en el músculo SM a 3 niveles de profundidad (superficial, medio y profundo) a 45 min, 2 y 24 h. pm. La calidad de la carne fue estimada en el músculo SM a partir de medidas de pH (45 min, 2, 8 y 24 h) y CE (45 min, 2 y 24 h). Las carnes fueron clasificadas como PSE (CE2>8 mS/cm), DFD (pH86,2) y Normales cuando la CE2<6 mS/ cm y el pH8<6. Los resultados obtenidos muestran como la calidad de la carne va a estar condicionada por el manejo presacrificio, la refrigeración de las canales, y en menor medida, por el faenado. Especialmente críticos son el reposo, acarreo y aturdido, como las operaciones más influyentes en vida del animal, junto con los ritmos de sacrificio que puedan sobrepasar la capacidad frigorífica del sistema de oreo rápido. También se encontraron mermas en la calidad de la carne como consecuencia del diseño y ubicación inadecuadas de algunas instalaciones o equipos. / The influence of the slaughter technology on carcass and pork meat quality was studied. The work consisted in a throughout study including all the operations carried out in a great capacity industrial slaughter, from the arrival of the animals to the refrigerated carcass. This was made in order to detect and correcting possible quality losses related to the technology applied. For this purpose, it was considered the most important processes that could have influence on the meat quality, among them were included: installation design, loading areas, corrals, slaughtering rooms, and refrigeration rooms. 2047 pigs from 36 different farms were studied considering different batches and measurements according to the industrial stage under study. Weight, lean, and backfat of carcass were determined in order to establish their commercial type and subjective conformation. SM temperature at 45 min. 2 and 24 h pm was measured at three different deep levels (surface, middle, bottom). pH (45min. 2,8,and 24h pm and CE (45min, 2, and 24h pro) measurements at SM were used for the estimation of meat quality. Meat was classified according to the latest parameters as PSE (CE2>8 mS/cm), DFD (PH8>6.2), and normal (CE2<6mS/cm and pH8<6). The results obtained showed the relationship between antemortem handling, carcass refrigeration conditions, and slaughter handling with meat quality. The most critical parameters affecting meat quality can be considered: resting animal, entry of animals into the slaughter rooms, stunning, and finally refrigeration room capacity being enough to keep the slaughtering rate. Losses of meat quality were also found because of non-adequate design and location of the installations.