Effects of muscle cortisol concentration on muscle fiber characteristics, pork quality, and sensory quality of cooked pork

The effect of muscle cortisol concentration on muscle fiber characteristics and technological and sensory quality of pork was investigated. With the exception of the percentage of type IIA fibers, muscle fiber characteristics were not associated to cortisol levels. However, muscle cortisol concentration was positively associated with muscle pH(24h) (r = 0.23, P<0.05) and negatively associated with drip loss (r = -0.49, P<0.001), lightness (r = -0.24, P<0.05), shear force (r = -0.25, P<0.05), and texture profile analysis-hardness (r = -0.35, P<0.01). Additionally, the water-holding capacity of meat samples was affected by cortisol levels, with lower cortisol concentrations associated with less tender samples. These results indicate that the concentration of cortisol in the muscle is related with meat quality as well as the sensory quality of cooked pork.     

Correlations of trained panel sensory values of cooked pork with fatty acid composition,muscle fiber type,and pork quality characteristics in Berkshire pigs

The objective was to examine the relationship of trained panel sensory scores of cooked pork with fatty acid composition, muscle fiber type, and meat quality characteristics from Berkshire pigs. No or few associations were found between the panel sensory scores of cooked meat, especially tenderness attributes, and fatty acid composition; however, intramuscular fat content positively correlated with off-flavor score (r = 0.31). On the other hand, the morphological characteristics of muscle fibers were correlated with panel sensory values. Muscles with smaller cross-sectional area and higher density of fibers were more closely associated with softer, more tender panel scores and a lower number of chews than muscles with larger fiber area and lower density of fibers. The water holding capacity test of filter-paper fluid uptake was moderately correlated with panel scores of softness (r = 0.33), initial tenderness (r = 0.38), chewiness (r = 0.40), juiciness (r = − 0.27), flavor intensity (r = − 0.23), and off-flavor (r = 0.30). Panel sensory values of Berkshire pig meat was moderately related to postmortem meat quality, especially water holding capacity. A more thorough understanding of the relationships between fatty acid composition and muscle fiber type with palatability is needed.     

Trained sensory perception of pork eating quality as affected by fresh and cooked pork quality attributes and end-point cooked temperature

The present study evaluated individual and interactive influences of pork loin (n = 679) ultimate ph (pH), intramuscular fat (IMF), Minolta L∗ color (L∗), Warner-Bratzler shear force (WBSF), and internal cooked temperatures (62.8 °C, 68.3 °C, 73.9 °C, and 79.4 °C) on trained sensory perception of palatability. Logistical regression analyses were used, fitting sensory responses as dependent variables and quality and cooked temperature as independent variables, testing quadratic and interactive effects. Incremental increases in cooked temperature reduced sensory juiciness and tenderness scores by 3.8% and 0.9%, respectively, but did not influence sensory flavor or saltiness scores. An increase of 4.9 N in WBSF, from a base of 14.7 N (lowest) to 58.8 N (greatest) was associated with a 3.7% and 1.8% reduction in sensory tenderness and juiciness scores, respectively, with predicted sensory tenderness scores reduced by 3.55 units when comparing ends of the WBSF range. Modeled sensory responses for loins with pH of 5.40 and 5.60 had reduced tenderness, chewiness, and fat flavor ratings when compared with responses for loins with pH of 5.80 to 6.40, the range indicative of optimal sensory response. Loin IMF and L∗ were significant model effects; however, their influence on sensory attributes was small, with predicted mean sensory responses measurably improved only when comparing 6% and 1% IMF and L∗ values of 46.9 (dark) when compared with 65.0 (pale). Tenderness and juiciness scores, were related to a greater extent to loin WBSF and pH, and to a lesser extent to cooked temperature, IMF and L∗.     

The influence of pork quality traits and muscle fiber characteristics on the eating quality of pork from various breeds

The purpose of this study was to compare parameters associated with pork quality, muscle fiber, and eating quality among various breeds, and to examine if differences in eating quality were associated to pork quality and muscle fiber characteristics. For carcass and pork quality, although there were significant differences among breeds, the values of parameters in all pigs were assigned a normal quality class, a likely outcome of the similarity in the area percentage of type I and IIB fibers. For eating quality, pork loins from Berkshire pigs were more tender and full of pork flavor than Landrace and Yorkshire pigs. Except juiciness and mouth coating, over 20% of the variability in the eating quality parameters can be explained by pork quality traits and muscle fiber characteristics using multiple regression analysis. Furthermore, differences in muscle pH_24 h, cooking loss, shear force, and NPPC marbling score could explain a large proportion of variation in eating quality parameters associated with the texture of pork.     

Consumer perceptions of pork eating quality as affected by pork quality attributes and end-point cooked temperature

The study evaluated the interactive and individual effects of fresh pork loin (n = 679) ultimate pH (pH), intramuscular fat (IMF), Minolta L^* color (L^*), Warner–Bratzler shear force (WBS), and four cooked temperatures (62.8 °C, 68.3 °C, 73.9 °C, and 79.4 °C) on consumer (n = 2280) perception of eating quality (n = 13,265 observations). Data were analyzed using ordered logistical regression. Predicted mean responses were consistently near or under five on the 1–8-point end-anchored scale, indicating a neutral perception of pork eating quality regardless of fresh quality or cooked temperature. Responses improved as IMF and pH increased and WBS decreased, whereas L^* did not contribute significantly to variation in responses. Increasing IMF resulted in a very small incremental improvement in responses, but was of practical size only when comparing the least (1%) to the greatest (6%) levels. Loin pH and WBS were primary contributors to consumer perceptions, whereby an incremental increase in pH (0.20 unit) and decrease in WBS (4.9 N) resulted in a 4–5% reduction in the proportion of consumers rating pork as 6 (favorable) on the 8-point scale. No interactions between quality and temperature effects were observed. Increased cooked temperature was negatively (P < 0.05) associated with Overall-Like and Tenderness ratings, but the incremental effect was small. Juiciness-Like and Level responses decreased by 0.50 units as temperature increased across the range. Consumer responses favor pork with lower WBS, greater pH and IMF, and pork cooked to a lower temperature.     

Effect of enhancement on the formation of heterocyclic amines in cooked pork loins: Preliminary studies

Heterocyclic amines (HCAs) which are produced in meats cooked at high temperature a risk factor for certain human cancers. This study evaluated the effect of enhancement on HCA formation in cooked pork loins. Three samples of pork loin were prepared including non-injected loin, 12% water-injected loin, and 12% salt/phosphate injected loin. The HCAs were identified in all samples: PhIP (2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine), MeIQx (2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline), and DiMeIQx (2-amino-3,4,8-trimethylimidazo [4,5-f]quinoxaline). Injection of salt/phosphate significantly reduced the level of PhIP by 42.7%, MeIQx by 79.0%, and DiMeIQx by 75.0%. Enhancement with water alone did not reduce HCA formation.     

Effects of electrical stimulation and temperature on beef quality and tenderness

Beef carcasses were stimulated with either 50 or 500 V and exposed to three chilling temperatures during the first 3 to 9 h post mortem. Both high (HV) and low voltage (LV) electrical stimulation (ES) treatments improved lean maturity scores, lowered the pH values at 2 h through 12 h and reduced the time required for the ATP level to reach minimum values. Both HV-ES and LV-ES treatments influenced firmness, fragmentation and connective tissue (CT) residue as measured by sensory panel and reduced Instron shear value (ISV) of loin steaks. The 30°C temperature treatment had an adverse effect while the 20°C temperature treatment had a beneficial effect on ISV and panel ratings for firmness and CT residue. There was an interaction between conditioning treatments and ES for ISV and sensory panel traits. The LV-ES-20C treatment resulted in the lowest ISV and superior panel ratings; however, the LV-ES-30C treatment had ISV and sensory panel ratings that were similar to the NES-2C (control) group.     

Effects of micro-perforated film on the quality and shelf life improvements of pork loins during chilled storage

The effects of micro-perforated film (MPF) packaging method on the quality and shelf life of pork loin during chilled storage were investigated, compared with non-packaging (control) and non-perforated film (PPF) packaging. Loins were removed from five hogs after slaughter and chilling, and each loin was portioned into four parts. These samples (40 sections) were allocated to each of five intervals (0, 1, 4, 7 and 14 days) to minimize variation among treatments and stored for 14 days under 55±10% relative humidity and 0±1?°C. Total aerobic counts of control sample were significantly lower than those from MPF or PPF loins after 14 days of storage. At 14 days, the counts of Pseudomonas and Enterobacteriaceae in the samples from MPF were significantly lower than those from PPF. At 7 days, 'L' value for the control and 'a' value for PPF were significantly lower, and ΔE values for the control were significantly higher than other samples. During storage time, percentage weight loss was the most in the control samples with MPF following and PPF the least. Accordingly, water contents decreased highest in the control samples followed by those from MPF and PPF. TBA values increased with storage time, however no significant differences were observed among treatments. Sensory evaluation analyses showed that MPF samples were generally better evaluated in all parameters over the storage time. Therefore, it has been concluded that MPF could be used as an effective packaging technology since it extends the shelf life of fresh meat by controlling the microbial growth and evaporation at a moderate level.     

Sensory and consumer evaluation of pork loins from crossbreeds between Danish Landrace,Yorkshire, Duroc,Iberian and Mangalitza

Iberian (I) and Mangalitza (M) boars were crossed with Duroc (D) and Landrace/Yorkshire (LY) sows and compared with the traditional crossbreed DLY. The sensory attributes were analysed, and consumers evaluated the fried loins. Gas chromatography (GC) aroma analysis was performed on the fried meat, and fatty acid composition was determined on the loin and the subcutaneous fat, respectively. No marked differences were found in odour, appearance or flavour/taste between the alternative crossbreeds and DLY; however, the alternative crossbreeds had improved textural properties. Consumer evaluation revealed that the alternative crossbreeds obtained positive associations compared with DLY, and MD was ranked best or second best by almost 60% of the consumers. No pronounced differences were found in the aroma compounds between the different crossbreeds. Correlations were found between the fatty acid composition and sensory attributes. In conclusion, by crossing the alternative breeds Iberian and Mangalitza with traditional Danish pig breeds it is possible to produce pork with attractive sensory attributes.     

Effects of dietary magnesium and duration of refrigerated storage on the quality of vacuum-packaged, boneless pork loins

Quality data were initially collected on 78 pork loins from crossbred pigs fed diets containing 0, 1.25 or 2.5% magnesium mica (MM). Loins were then vacuum-packaged, and randomly assigned to either 4 or 8 weeks of storage at 2°C. Dietary MM had no (P > 0.05) effect on moisture loss/retention or subjective and objective color measurements. Purge volume increased (P<0.05) and drip loss decreased (P<0.05) as storage time increased. Moreover, longissimus thoracis et lumborum (LM) chops became lighter (P<0.05), redder (P<0.05), and more yellow (P<0.05) during 8 weeks of storage. Although TBARS values increased linearly (P<0.001) during extended storage, LM chops from pigs fed 2.5% MM tended to have lower (P<0.07) TBARS values after 4 weeks of storage than chops from pigs fed 0 and 1.25% MM. After 8 weeks of storage, however, there was a tendency for TBARS values of chops from pigs fed 1.25% MM to be lower (P<0.07) than chops from pigs fed 2.5% MM. Even though feeding swine diets containing MM did not affect color and water-holding capacity of pork loins during storage, the data indicated inclusion of MM in swine diets may retard onset of oxidative rancidity in vacuum-packaged pork loins.     

Tensile properties of cooked beef in relation to rigor temperature and tenderness

A study of the tensile properties of cooked strips from beef sternomandibularis which had gone into rigor at various temperatures showed no clear relationships with earlier observed variations in shear force with rigor temperature. A consistent feature of the load extension curves was a sudden increase in extensibility at a ‘change point’ of about 1 kg/cm². Some curves, particularly those for strips cooked under restraint, showed a third intermediate extensibility. Evidence points to modification of a myofibrillar component as the reason for the sudden changes.     

不同包装方式对冷鲜猪肉的保鲜效果

研究了普通托盘包装、真空包装、高氧气调包装(70%O2+30%CO2)和一氧化碳气调包装(0.4%CO+30%CO2+69.6%N2)对冷鲜猪肉的保鲜效果。通过对不同包装方式下冷鲜猪肉在贮藏期的色泽、汁液流失、挥发性盐基氮和微生物的分析,发现真空包装、高氧气调包装和一氧化碳气调包装均显著抑制了冷却肉中微生物的生长,提高了贮藏期间的色泽品质,但是真空包装汁液流失严重,且抑菌效果不如2种气调包装;高氧气调包装虽然有较好的护色效果和抑菌效果,但易使肉后期色泽变暗;一氧化碳包装既能维持贮藏期内较好的肉色,又能起到较好的抑菌效果,对冷却猪肉具有较理想的保鲜效果。     

Effect of dietary ractopamine on tenderness and postmortem protein degradation of pork muscle

Twenty-four finishing pigs with a mean starting weight of 82 kg were assigned to two dietary regimens: (1) a corn–soybean meal basal diet (control; n = 12), and (2) the basal diet supplemented with 20 ppm ractopamine HCl (RAC; n = 12). After 28–30 days on the feeding trial, pigs were slaughtered, and the growth and carcass characteristics were measured. Furthermore, the 3rd–13th rib section of longissimus muscle was excised at 48 h postmortem, sliced into 19-mm thick chops, vacuum packaged, stored at 2 °C, and subjected to Warner–Bratzler shear force (WBSF) and electrophoretic tests after 2, 4, 7, 10, 14, and 21 days (postmortem). RAC feeding increased (P < 0.01) pig carcass weight and percent lean, but it also increased the day-2 muscle WBSF by 20% (P < 0.01). The shear force difference between control and RAC pig muscles gradually decreased and vanished by day 10 (P > 0.05) when both muscle groups became more tender. The muscle from RAC-fed pigs exhibited a slower protein degradation rate than muscle from the control animals, notably for proteins in the 15–45 kDa range. The results suggested that the tenderness difference between ractopamine-treated and control pig muscles was related to the proteolysis rate, and could be diminished with adequate postmortem ageing.     

Effects of pork muscle quality on bacterial growth and retail case life

The effects of muscle quality (PSE, normal, DFD) upon the bacteriology and retail case life of pork chops were determined. Pork loin chops were processed from boneless backs after 90 days of frozen storage at -30°C. Variation in bacterial numbers was due to a highly significant (p < 0·001) storage time by muscle quality interaction. During simulated retail display, total psychrotrophs, Pseudomonas spp., Brochothrix thermosphacta and Enterobacteriaceae were lowest on PSE pork and highest on DFD pork in comparison to normal pork. Differences in bacterial densities were due to a longer lag phase in PSE pork and a shorter lag phase in DFD pork than in normal pork. Of the three muscle quality groups, DFD was most susceptible to the development of spoilage odours, while PSE pork was most sensitive to deterioration in appearance.     

The relation of blood glucose level to muscle fiber characteristics and pork quality traits

The purpose of this study was to examine the relationships between blood glucose level, muscle fiber characteristics, and pork quality. Muscle samples were classified into three groups based on blood glucose level measured at slaughter. Pigs with higher area percentages of fiber type IIB showed higher blood glucose levels compared to pigs with lower area percentages of fiber type IIB. The high blood glucose level group presented lower pH values at 45 min and 24 h postmortem, and also had higher L^∗ values and reduced water holding capacity. In addition, blood glucose level had a negative relationship with pH_45 min and the solubility of sarcoplasmic and myofibrillar proteins, whereas it had a positive relationship with drip loss and filter-paper fluid uptake. In conclusion, blood glucose level was related to muscle fiber area composition and could partially indicate ultimate pork quality.     

Effects of soybean oil and linseed oil on fatty acid compositions of muscle lipids and cooked pork flavour

This study was conducted to investigate the effects of dietary oil on the fatty acid compositions of the longissimus and biceps brachii muscles and its effects on cooked muscles flavour. Seventy-two crossbred barrows (Duroc×Landrace×Large White), were blocked by weight and randomly assigned to one of three treatments. The three dietary treatments were: (a) no oil supplement (CON); (b) 3% soybean oil supplement (SO3); (c) 3% linseed oil supplement (LO3). Dietary linseed oil and soybean oil significantly increased the contents of C18:3 and C18:2 in the neutral lipids and phospholipids in both longissimus muscle and biceps brachii muscle, respectively. Aroma compounds analysis indicated only few aroma compounds were affected significantly by dietary oil in both cooked longissimus muscle and biceps brachii muscle. The flavour attributes of cooked longissimus muscle and biceps brachii muscle were not influenced by feeding 3% soybean oil. Feeding 3% linseed oil did not deleteriously affect the flavour of cooked longissimus muscle but cooked biceps brachii muscle from LO3 had significantly lower pork flavour and higher abnormal flavour than CON and SO3.     

Mechanical and structural characteristics of single muscle fibres and fibre groups from raw and cooked pork longissimus muscle

The aim of this study was to analyse the mechanisms that determine why small groups of muscle fibres may have different mechanical properties than single muscle fibres. The method used combined light microscopy and tensile testing on single fibres and small groups of fibres from raw and cooked (80 °C) meat, from both conditioned and unconditioned porcine longissimus muscle. The results showed that small groups of fibres had different breaking properties than constituent single fibres in raw muscle, but that these differences diminished on cooking. Raw groups of fibres showed a more uniform lengthening along their entire length and a higher extension to rupture than single fibres. Conditioning increased maximum strains in both single fibres and small fibre groups. In unconditioned cooked meat, single fibres and fibre groups showed comparable breaking stresses and extensions. Conditioning resulted in a lower strength in fibre groups than in single fibres. These results show that (endomysial) connective tissue linkages between adjacent muscle fibres in a small group significantly alter the breaking behaviour of single fibres. The effects of these connective tissue linkages are not reduced by conditioning alone, but are largely diminished by cooking to 80 °C.     

Effects of meat quality and storage on the breakdown of adenosine triphosphate in muscle from swine

The quality of pork is dependent on animal genotype, pre-slaughter handling, processing, maturation, and storage. We investigated the pattern of adenosine triphosphate (ATP) breakdown as it related to these factors. Samples of the thoracis portion of the longissimus dorsi muscle were obtained from 19 randomly selected German Landrace-Pietrain crossbreed swine. Based on their 40 min post-mortem pH and electrical conductances, three groups were classified: (1) PSE meat, pH ≤ 5·6 and conductance >10 mS (n = 7); (2) intermediate quality, pH 5·6-6·0 and conductance between 4 and 10 mS (n = 5); and (3) normal quality, pH ≥ 6·0 and conductance < mS (n = 7). Hence, the animals investigated included those susceptible to malignant hyperthermia (porcine stress-syndrome). Twenty-four hours post mortem samples were evaluated for the following parameters: ATP metabolism, pH values, electrical conductance, meat colour, water binding capacity, shear force and general composition (i.e. total protein, fat, mineral and water contents). Muscle composition was the same in each group, but for the other parameters there were clear differences. Following different storage periods and conditions (1 or 5 days at 4°C and 27 days at -18°C), the degree of ATP metabolism as well as general meat quality (i.e. including sensory evaluation) were reassessed. Samples from the pre-selected groups became less discernible following prolonged storage. In all animals, the pattern of ATP breakdown was similar, the major metabolites including inosine monophosphate, hypoxanthine, adenosine monophosphate, and inosine. The degree of breakdown was dependent on the duration and temperature of storage, but not on animal type. The muscular samples for the intermediate and normal muscle groups, which were stored for 27 days at -18°C, were given the highest sensory evaluation scores. The simple HPLC measurement of ATP metabolism was considered as a useful means to assess appropriate storage.     

Influence of rosemary-tocopherol/packaging combination on meat quality and the survival of pathogens in restructured irradiated pork loins

Irradiated restructured pork loins treated with rosemary-tocopherol/double-packaging had lower TBARS values than vacuum-packaged control after 10 days of refrigerated storage. The rosemary-tocopherol combination, however, had no effect on the production of sulfur volatiles responsible for the irradiation off-odor, and color changes in irradiated pork. V7/A3 double-packaging was effective in reducing the sulfur volatiles significantly. Rosemary-tocopherol combination was highly effective in reducing the volatile hexanal in irradiated restructure pork. Irradiation was effective in reducing Listeria monocytogenes and Salmonella typhimurium inoculated on the surface of restructured pork loin in dose-dependent manner. The irradiation D(10) values for L. monocytogenes and S. typhimurium were 0.58 and 0.55kGy, respectively. During the 20 days of refrigerated storage, L. monocytogenes in both nonirradiated and irradiated samples grew gradually, but the number of S. typhimurium decreased. The added rosemary-tocopherol, however, showed little bacteriocidal effects to L. monocytogenes and S. typhimurium.