B. Engel

A comparison of methods to estimate water-holding capacity in post-rigor porcine muscle

Water-holding capacity (WHC) of muscle is important because it affects both qualitative and quantitative aspects of meat and meat products. For assessment of WHC under field and laboratory conditions, there are several methods available, but they have not been compared in a single experiment to determine accuracy and repeatibility. The Longissimus dorsi from each of 28 porcine loins representing three distinct levels of WHC (DFD, PSE, normal) was separated into eighteen parts that were randomly assigned to individual methods. The following methods were compared: Grau-Hamm and Braunschweiger-Gerät filter paper press techniques using five approaches of evaluation for each method; transmission per cent; swelling due to added water; centrifugation; 48-h fresh and cooked shrink: imbibition of surface fluids, kapillar volumeter, permittivity; and score or weight of surface fluids accumulating on filter paper. Results indicated that most methods separated the three muscle types. However, the cooking loss tests failed to differentiate between PSE and normal samples, and the transmission, imbibition and pressed fluid methods did not always distinguish between DFD and normal. The tests that appeared to be most reliable included drip loss originating from size-standardized samples, swelling of homogenized samples by added water and absorption of surface fluids on filter paper.

The effectiveness of examining early post-mortem musculature to predict ultimate pork quality

Variations in pork quality reflect value differentials. However, only when they can be easily, accurately, rapidly and cost-effectively detected, can swine producers expect to eliminate poor quality from their herds through genetic selection, and can the industry be expected to take the necessary environmental precautions to prevent poor quality. This study was designed to assess the effectiveness of various techniques thought to predict ultimate pork quality through the examination of the physical and chemical properties of early post-mortem (PM) musculature. Based on stiffness and pH 30, 285 carcasses were selected. This selection procedure ensured a wide variation in ultimate quality. Using 12 instruments simultaneously, temperature, stiffness, electrical properties, lightness properties, and pH 45 of the early PM longissimus thoracis et lumborum were recorded to predict ultimate quality. Based on post-rigor light reflection and water-holding capacity (WHC), quality was assigned to one of five arbitrary groups. Of all techniques tested, the only one with any potential for adequate prediction of quality categories was pH 45. Combination of different techniques did not significantly increase predictive values. For predicting quality of single carcasses, pH 45 should not be considered satisfactory. However, based on our success in selecting carcasses representing quality variation for this study and the results obtained from the study, using pH 45 and muscle stiffness to select groups of carcasses is feasible. We conclude that the techniques used early post mortem are not appropriate for predicting ultimate pork quality for single carcasses. At present we recommend that only post-rigor muscle be considered, and that ultimate pH, light reflection and a measure of WHC should be used.

The effect of stress, applied immediately before stunning, on pork quality

The effect on meat quality characteristics of stress, applied during a short period just before stunning, was studied on slaughterpigs (113 boars, 85 gilts). Sexes were kept separately and only pigs that had been stunned correctly were included. Aggressive behaviour during lairage occurred more frequently in boars (about twice) than in gilts. Just before stunning, two animals of the same sex, that were lairaged for an equal period at the slaughter facility, were moved as quietly as possible to the stunning pen, after which one pig was stunned immediately and the other subsequently forced to move through the stunning pen over a period of 1 min. Stress resulted in lower pH values and higher temperatures in the semimembranosus (SM) and the longissimus lumborum (LL) muscles and a higher rigor mortis value of the SM, at 45 min post mortem. Stress affected water holding capacity of the LL negatively at 24 h p.m. Statistically significant interactions were present for sex×stress for several meat quality traits. In general, gilts reacted more strongly to short periods of stress than did boars.

Marbling, intramuscular fat and meat colour of Dutch pork

The amounts of intramuscular (i.m.) fat in the lean meat of the lumbar region of 21 slaughterpigs have been determined according to the Soxhlet method as a reference, and compared with those determined with the faster Foss-let procedure. These methods were highly correlated, over the lower range of fat concentrations (0·30-4·35%) studied. Although the Foss-Let values were on average slightly lower than the Soxhlet values, the Foss-Let procedure can be recommended for the determination of i.m. fat in pork. Furthermore, chemically determined i.m. fat was found to be significantly correlated with marbling. The sensory evaluations of pork colour were significantly correlated with each other and with the instrumentally determined colour lightness.