Henrik J. Andersen

Factors of significance for pork quality-a review.

This paper reviews current knowledge about factors of importance for pork quality with special emphasis on technological quality attributes. It is evident that production and slaughter factors can be used to control technological quality traits. However, most of the present knowledge is based on studies investigating the influence of a single or at the most two factors. This survey reveals that: -Most important, an understanding of how production and slaughter factors interact in relation to pork quality is a must to give the maximum number of tools to control pork quality and hereby meat quality demands of tomorrow. -The existence of a new genetic pool (elimination of the halothane and RN(-) genes in the commercial pig populations of tomorrow) force the meat science into a renaissance, as the influence of production and slaughter factors on pork quality may be fundamentally different in this new genetic pool. -A basic understanding on how muscle glycogen stores are influenced by genotype and feeding regime and the interaction with pre-slaughter handling might be the next major breakthrough in controlling technological pork quality. -Introduction of new production systems claim parallel studies to prevent unforseen negative effect on quality. -A holistic approach is needed to give an overall understanding of the influence of production, peri and post mortem factors on pork quality.

Water distribution and mobility in meat during the conversion of muscle to meat and ageing and the impacts on fresh meat quality attributes — A review

This paper reviews current knowledge on the distribution and mobility of water in muscle (myowater) ante- and post mortem and factors affecting these in relation to fresh meat quality parameters; water-holding capacity (WHC), tenderness and juiciness. NMR transverse relaxometry (T(2)) using bench-top Low-Field Nuclear Magnetic Resonance (LF-NMR) has characterised myowater distribution and mobility as well as structural features in meat which directly affect WHC. The current literature demonstrates that WHC is correlated to the water located outside the myofibrillar network (extra-myofibrillar). This review identifies the critical stages which affect the translocation of water into the extra-myofibrillar space and thus the potential for decreased WHC during proteolysis (the conversion of muscle to meat). This review discusses how the intrinsic properties of the water held within the meat could contribute to juiciness and tenderness. Tenderness has been shown to correlate to T(2), however breed and species differences made it difficult to draw firm conclusions. Further understanding of the inherent water properties of fresh meat and the factors affecting water distribution and mobility using NMR technologies will increase the understanding of WHC and tenderisation of fresh meat.

Cooking loss and juiciness of pork in relation to raw meat quality and cooking procedure

The study comprised two experiments with the aim to investigate the influence of raw meat quality and cooking procedure on cooking loss and juiciness of pork. The first experiment determined the cooking loss at 60, 70 and 80 °C centre temperature of 10 raw meat qualities (defined according to ultimate pH, drip loss, breed and rearing conditions) when cooked as steaks on a pan or as a roast in oven at a oven temperature of 90 or 190 °C. The differences in cooking loss between the raw meat qualities and the cooking procedures did decrease as the centre temperature increased and were almost negligble at 80 °C. Low water holding capacity (WHC) and low pH resulted in high cooking loss while no difference in cooking loss was observed between meat having medium or high WHC and pH. In the second experiment four raw meat qualities (standard, Duroc, low pH and heavy carcass weight) chosen from the first experiment to ensure a wide variation in cooking loss, were cooked in oven at 90 or 190 °C oven temperature. Juiciness was assessed three times during the chewing process. The results suggested that juiciness experienced initially in the chewing process depended only on the water content of the meat, whereas juiciness experienced later in the chewing process was determined by a combination of the water and intramuscular fat contents and the saliva production during chewing.

Feeding and meat quality - a future approach.

The continuous demand for high standards of quality assurance in the meat production of today and tomorrow calls for development of new tools capable of meeting such demands. The present paper aims to re-think the traditional way of using feeding as a quality control tool in the production of meat and to introduce the potential of a nutrigenomic approach as a first step in the development of pro-active quality control systems which fulfil future demands from industry and consumers. A few chosen examples present how specific feeding strategies can manipulate (i) muscle protein turnover and thereby meat tenderness as well as the cost and sustainability of the production and (ii) muscle energy levels at slaughter and thereby the pH decline, water-holding capacity and the sensory characteristics of meats. The examples are discussed in relation to exploiting essential and basic understanding of physiological and physical processes, which can subsequently be included in a systems biology line of thought of importance for development of unique decision support systems in future meat production.

Continuous distribution analysis of T2 relaxation in meat-an approach in the determination of water-holding capacity

Continuous distribution analysis as well as traditional bi-exponential fitting analysis were carried out on NMR T(2) relaxation data measured 24 h post-mortem in 74 pork meat samples from M. longissimus dorsi. Areas of relaxation populations found by continuous distribution analysis and corresponding time constants were determined. Comparison of correlations to water holding capacity (WHC), determined by Honikels bag method [Honikel, K. O. (1998). Reference methods for the assessment of physical characteristics of meat. Meat Science, 49, 447-457], revealed superior performance of continuous distribution analysis (r=-0.85) compared with traditional bi-exponential fitting analysis (r=-0.77). Furthermore, the changes in continuous relaxation time distribution spectra were followed during loss of water from meat samples by centrifugation. It was found that the area of the slowest relaxation population (T(22)) decreased proportionally with the amount of expelled water. A physical explanation for the obtained correlation between continuous relaxation time distribution data and WHC is given upon the results from these data.

Comparative study of low-field NMR relaxation measurements and two traditional methods in the determination of water holding capacity of pork.

The correlation between transverse relaxation, T(2,) and water holding capacity (WHC) determined either by Honikels bag method (Honikel, 1998) or centrifugation has been investigated in meat samples from m. longissimus dorsi (LD) 24 h post mortem from 74 pigs. Bi-exponential analysis of the transverse relaxation, T(2), showed highly significant correlations between both the two NMR time constants (T(21),T(22)) and water holding capacity determined by both Honikels bag method (r(T(21))=-0.72 and r(T(22))=0.77) and centrifugation (r(T(21))-0.50 and r(T(22))=0.75). This shows that transverse relaxation measurement is an efficient method for determination of water holding capacity in pork. Significant correlations were also found between T(21) and T(22) measured 24 h post mortem and pH measured at various time post mortem. This indicates that transverse relaxation, T(2), reflects pH-induced structural changes occurring in muscles post mortem.

Aging-induced changes in microstructure and water distribution in fresh and cooked pork in relation to water-holding capacity and cooking loss - A combined confocal laser scanning microscopy (CLSM) and low-field nuclear magnetic resonance relaxation study.

Confocal laser scanning microscopy (CLSM) and low-field nuclear magnetic resonance (LF-NMR) relaxometry were combined to characterize microstructural changes and water distribution in fresh and cooked pork during an aging period of 14 days. At day 1 (24h postmortem) a few muscle fibres, which appear swollen, were observed in both fresh and cooked meat. An identical microstructure was still apparent after 14 days, however, the number of muscle fibres showing distinguished characteristics was found to increase throughout the aging period. Hence, it was apparent that during aging the individual fibres swell and disintegrate at different rates. Development in water-holding capacity (WHC) was followed during the aging period using gravimetric methods, and an increase in the WHC in the fresh meat was observed, which resembled the amount of extramyofibrillar water measured by NMR relaxometry (T(22) population). This was consistent with the CLSM images, as a substantial increase in the number of myofibrils that appeared swollen, capable of holding more water, was observed during aging. In the cooked meat the width of the T(21c) population, reflecting the myofibrillar water in the cooked meat, was seen to decrease during the entire storage period, which corresponds to the development of a more homogeneous structure. In the CLSM data a continuous degradation during the storage period was observed, which could resemble a shift to a more homogeneous structure. Comparison of CLSM of transverse sections of fresh and cooked pork revealed a pronounced shrinkage of muscle fibres upon cooking. This resulted in large gaps between the cooked muscle fibres, which also was visible as shrinkage at the level of the individual myofibrils. This pattern was also reflected in the NMR relaxation data. The cooking-induced shrinkage of the myofibrils occurred concomitantly with a decrease in the amount of intermyofibrillar water within the individual fibre and an increase in the larger extramyofibrillar spaces between fibres, i.e. water is expelled from the myofibrillar matrix upon cooking. Accordingly, the present study demonstrated that the use of CLSM together with NMR relaxometry can provide further information on the relationship between structural characteristics of meat and resultant water distribution.

Early prediction of water-holding capacity in meat by multivariate vibrational spectroscopy

This study had the dual purpose of (a) investigating the feasibility of measuring fundamental vibrational information in fresh porcine meat using infrared (IR) absorption and Raman scattering, and (b) investigating if the vibrational spectra obtained within 1 h after slaughter contained information about the water-holding capacity (WHC) of the meat. Preliminary studies performed at a research slaughterhouse revealed a high correlation between WHC and both IR (r=0.89) and Raman spectra using Partial Least Squares Regressions (PLSR). The good results were confirmed under industrial conditions using FT-IR at-line spectroscopy. However, the latter experiment yielded a somewhat lower correlation (r=0.79). This result is, however, promising for the purpose of finding a method for classification of carcasses with regard to WHC at the slaughter line. The IR region 1800-900 cm(-1) contains the best predictive information according to WHC of the porcine meat. This region covers functional group frequencies of water, protein, fat and glycogen, including the carbonyl and amide groups.

Effect of organic pig production systems on performance and meat quality

The present study was carried out to establish knowledge of consequence for setting up guidelines of importance for production of competitive organic pork of high quality. Performance and meat quality characteristics were compared between three organic pig production systems based on indoor housing with access to an outdoor area and a Danish conventional indoor system including 100% concentrate during the finishing feeding stage. The three organic systems used the following three feeding regimes: 100% organic concentrate according to Danish recommendations, 70% organic concentrate (restricted) plus ad libitum organic barley/pea silage and 70% organic concentrate (restricted) plus ad libitum organic clover grass silage, respectively. With exception of a slightly lower daily gain in organic pigs fed 100% concentrate, no significant difference was found in performance and meat quality characteristics compared with results obtained in the conventional system. In contrast and independent of roughage used, organic pigs raised on 70% concentrate had a significant reduction in daily gain (P<0.001) compared with pigs raised on 100% concentrate, despite the fact that no difference in feed conversion rate was seen between the tested production systems. However, the percentage of leanness increased significantly in meat from organic pigs raised on 70% concentrate plus roughage compared with meat from pigs given 100% concentrate. This was reflected in higher yield (weight) of lean cuts and lower yield of cuts with high fat content from pigs fed 70% concentrate plus roughage. In general, organic feeding resulted in a significantly higher content of polyunsaturated fatty acids in the back fat (1.8%), which increased further when restricted feeding plus roughage (4%) was used. Restricted concentrate feeding gave rise to a decrease in tenderness compared with pork from pigs fed 100% concentrate.

The significance of pre-slaughter stress and diet on colour and colour stability of pork

The influence of pre-slaughter stress and a diet known to affect post mortem muscle metabolism or a standard diet (control pigs) on colour and colour stability of m. longissimus dorsi, m. biceps femoris and m. semimembranosus from 112 female pigs, free of the Halothane gene, was investigated. Pre-slaughter stress increased the early post mortem temperature in the three muscles, as well as the pH decline in control pigs, but not in pigs fed the experimental diet. Colour was measured on sliced samples after 0, 2 and 5 days retail display (1, 3 and 6 days post mortem, respectively) from the three muscles aged 1 day before cutting as well as on sliced m. longissimus dorsi samples aged 8 days before cutting (8, 10 and 13 days post mortem, respectively). Early post mortem pH was not a main determinant of the colour and colour stability, while the degree of pre-slaughter stress and especially its influence on temperature early post mortem was crucial in relation to colour development and colour stability. The discoloration rate was enhanced in m. longissimus dorsi aged for 8 days prior to retail display compared with samples aged for 1 day. However, the extent of the discoloration after 5 days of retail display was not inferior in muscle samples aged for 8 days due to a higher degree of blooming. Finally, present data indicate that 3-4 days ageing of pork prior to retail display results in the optimal colour stability.