Occurrence of heterocyclic amines in cooked meat products

Heterocyclic amines (HCAs), potent mutagens and a risk factor for human cancers, are produced in meats cooked at high temperature. The aim of this study was to determine the HCA content in cooked meat products (beef, chicken, pork, fish) prepared by various cooking methods (pan frying, oven broiling, and oven baking at 170 to 230 °C) that are preferred by U.S. meat consumers. The primary HCAs in these samples were PhIP (2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine) (1.49-10.89 ng/g), MeIQx (2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline) (not detected-4.0 ng/g), and DiMeIQx (2-amino-3,4,8-trimethyl-imidazo [4,5-f]quinoxaline) (not detected-3.57 ng/g). Type and content of HCAs in cooked meat samples were highly dependent on cooking conditions. The total HCA content in well-done meat was 3.5 times higher than that of medium-rare meat. Fried pork (13.91 ng/g) had higher levels of total HCAs than fried beef (8.92 ng/g) and fried chicken (7.00 ng/g). Among the samples, fried bacon contained the highest total HCA content (17.59 ng/g).     

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 effect of muscle, cooking method and final internal temperature on quality parameters of beef roast

The aim of the study was to evaluate the influence of cooking conditions (dry air and steam) and final internal temperature (75, 85, 95°C) on the physico-chemical properties of beef infraspinatus (INF) and semimembranosus (SEM) muscles as well as their tenderness and juiciness. Cooking method and temperature influenced moisture, total collagen content in cooked meat and cooking loss, whereas muscle type affected fat, total collagen content and cooking loss. Warner-Bratzler shear force values were affected by cooking method, which also influenced juiciness of roasts. Temperature affected tenderness and juiciness, whereas muscle type influenced juiciness. The most desirable tenderness had INF heated in steam and dry air to 95°C. Processing SEM in dry air to 85 and 95°C lowered the juiciness of the roasts. There were significant correlations between physico-chemical, sensorial and image attributes, however high accuracy of prediction (r(2)>0.8) was achieved only for SEM muscle.     

Relationship between meat toughness and properties of connective tissue from cows and young bulls heat treated at low temperatures for prolonged times

The aim of the current study was to elucidate whether cows and young bulls require different combinations of heating temperature and heating time to reduce toughness of the meat. The combined effect of heating temperature and time on toughness of semitendinosus muscle from the two categories of beef was investigated and the relationship to properties of connective tissue was examined. Measurements of toughness, collagen solubility, cathepsin activity and protein denaturation of beef semitendinosus heated at temperatures between 53 °C and 63 °C for up to 19 1/2 h were conducted. The results revealed that slightly higher temperatures and prolonged heating times were required to reduce toughness of semitendinosus from cows to the same level as in young bulls. Reduced toughness of semitendinosus as a result of low temperature for prolonged time is suggested to result from weakening of the connective tissue, caused partly by denaturation or conformational changes of the proteins and/or by solubilization of collagen.     

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.     

压力温度处理对肉制品中微生物的影响

旨在研究压力（300MPa，15rain）、温度（5，20，35，50℃）共同处理灭活肉制品中微生物（细菌总数、乳酸细菌、葡萄球菌、假单胞菌和肠杆菌）的效果。实验表明：压力温度处理可以明显降低猪肉中微生物数量；革兰氏阴性细菌对压力更敏感；当加压温度为50℃时，灭活微生物的效果更好；微生物对高压处理的敏感性与压力处理时的温度，微生物的类群和肉的种类有关。     

The comparison of three β-agonists for growth performance,carcass characteristics and meat quality of feedlot cattle

Forty-eight Bonsmara steers were assigned to three treatment groups and one control group consisting of 12 animals each. The control (C) received no β-agonist, while the three treatment groups received zilpaterol (6 ppm) (Z), ractopamine (30 ppm) (R) or clenbuterol (2 ppm) (Cl) for the last thirty days on feed. Growth performance (final 30 days), USDA quality and yield grades and meat quality (shear force, chemical, histological and biochemical) were compared for the three β-agonist and control groups. Animals responded negatively to Cl treatment during initial stages of supplementation, which was evident in lower feed consumption and initial growth rates. For carcass growth and yield, Cl had greater and more efficient growth rates, higher dressed out yields (proportional), lower USDA yield grades, and reduced marbling compared with C (P < 0.05). For meat quality measurements, the M. longissimus (LL) and M. semitendinosus (ST) were sampled. Cl had the greatest effect (P < 0.05) on WBSF, especially on the LL, followed by Z. Variation in tenderness and ageing effects corresponded with variation in calpastatin activity and myofibrillar fragmentation between treatment groups. While zilpaterol and ractopamine are currently the only products registered for cattle in different countries, it seems that zilpaterol has an advantage in carcass growth efficiency and yield without showing any adaptation problems for animals such as experienced by the more aggressive β-agonist clenbuterol.     

Sensory and physical characteristics of enhanced vs. non-enhanced meat from mature cows

Semitendinosus and longissimus muscles were removed from both sides of 10 mature Simmental cows ranging from 10 to 13 yrs. After aging for 7 days, one side was injected with a commercial salt mixture to a pumped gain of 15%; the other side served as control. Muscles were aged for a further 7 days before analysis. Injection significantly increased meat pH by 0.3 units in longissimus samples and reduced shear force values from about 50N in control samples to 37N for longissimus samples and 42N for semitendinosus samples. Injection also increased juiciness and tenderness scores by approximately 1unit when assessed by a trained sensory panel using 1-8 scales. Beef flavour, however, was more atypical in injected samples, which were also more salty. Injected samples were also pinker during storage and after cooking.     

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.     

Carcass and meat quality characteristics of Brahman cross bulls and steers finished on tropical pastures in Costa Rica

Forty-eight male calves (3/4 Brahman × 1/4 Charolais) were used to determine carcass cutability and meat tenderness of Longissimus lumborum (LL), Gluteus medius (GM), Semitendinosus (ST) and Psoas major (PM) steaks from lighter weight carcasses of bulls and steers castrated at 3, 7, or 12 mo of age grown under tropical pasture conditions. Steaks from steers had lower (more tender) LL Warner–Bratzler shear force (WBSF) values than those from bulls. Steaks from steers castrated at 3 mo had lower GM WBSF than those from bulls. For PM steaks, those aged 28 d had lower WBSF than those aged 2 d. Steaks aged 28 d had the lowest LL and GM WBSF and steaks aged 2 d had the highest LL, GM, and ST WBSF. Castration at younger ages is recommended because it provides improvement in LL and GM tenderness over bulls with no differences in carcass traits or subprimal yields.     

Influence of ultimate pH on bovine meat tenderness during ageing

The aim of this work was to evaluate the influence of ultimate pH and ageing at 2±2°C on the tenderness of beef. The m.longissimus thoracis et lumborum from 23 young bulls excised at 28 h post mortem were grouped into: Normal (pH 5.5 to 5.8) moderate DFD (mod DFD) (5.8p<0.05) lower in the DFD group than in the Normal one and a significant (p<0.001) linear relationship was found between ultimate pH and tenderness as evaluated by both methods. The myofibrillar protein solubility (MPS) at pH 7.0 was significantly higher in the DFD group at all post mortem times whereas for myofibrillar fragmentation index (MFI) higher values (p<0.05) were only found in the DFD group at day 1. In all three groups toughness decreased (p<0.05) from 1 to 6 days, with no further decrease to 13 days. This decrease in toughness was associated with an increase of MFI in all pH groups. Collagen solubility in all three groups was not affected by ageing. No significant (p>0.05) differences in soluble collagen and myofibrillar protein solubility (MPS) at pH 5.5 were found between the pH groups at any time. The tenderness evaluated by both methods was significantly (p<0.05) related to MFI, MPS at pH 7.0, cooking loss and juiciness. Total and soluble collagen, sarcomere length, intramuscular fat and MPS at pH 5.5 were not significantly (p>0.05) related with tenderness.     

Meat quality of young Nellore bulls with low and high residual feed intake

Fifty-nine Nellore bulls from low and high residual feed intake (RFI) levels were studied with the objective of evaluating meat quality traits. Animals were slaughtered when ultrasound-measured backfat thickness reached 4 mm, and samples of Longissimus were collected. A mixed model including RFI as fixed effect and herd and diet as random effects was used, and least square means were compared by t-test. More efficient animals consumed 0.730 kg dry matter/day less than less efficient animals, with similar performance. No significant differences in carcass weight, prime meat cuts proportion, chemical composition, pH, sarcomere length, or color were observed between RFI groups. Shear force, myofibrillar fragmentation index and soluble collagen content were influenced by RFI, with a higher shear force and soluble collagen content and a lower fragmentation index in low RFI animals. Feedlot-finished low RFI young Nellore bulls more efficiently convert feed into meat, presenting carcasses within quality standards.     

Prevalence of Arcobacter species in retail meats and antimicrobial susceptibility of the isolates in Japan

A survey was conducted to examine the prevalence of Arcobacter species among meat samples and to investigate the antimicrobial susceptibility of the isolates in Japan. In 1998 and 1999, samples of beef (n=90), pork (n=100) and chicken meat (n=100) were purchased from seven retail shops. Arcobacter species were isolated from 2.2%, 7.0% and 23.0% of beef, pork and chicken meat samples, respectively. The rate of isolations in chicken meats was shown to be significantly higher than those of beef and pork. Species-specific polymerase chain reaction (PCR) demonstrated that the most dominant Arcobacter species was Arcobacter butzleri among the isolates examined. Multiple contaminations with different Arcobacter species were observed in 5% of the chicken samples. Almost all the strains tested showed resistance to vancomycin (100%) and methicillin (97.5%). Strains resistant to cephalothin, sulfamethoxazole–trimethoprim, nalidixic acid and chloramphenicol were detected at the rate of 81.1%, 67.2%, 53.5% and 24.6%, respectively. All Arcobacter strains examined were susceptible to ampicillin, tetracycline, streptomycin and kanamycin.     

Encapsulated phosphates reduce lipid oxidation in both ground chicken and ground beef during raw and cooked meat storage with some influence on color,pH, and cooking loss

Effects of encapsulated sodium tripolyphosphate (STP), sodium hexametaphosphate (HMP) and sodium pyrophosphate (SPP) on lipid oxidation in uncooked (0, 2, 24 h) and cooked (0, 1, 7 d) ground chicken and beef during storage were determined. Ten phosphate treatments included a control (no phosphate), three unencapsulated (u) at 0.5% and three encapsulated (e) phosphates (0.5%) each at a low (e-low) and high (e-high) coating level. Two heating rates (slow, fast) were investigated. Cooking loss (CL), pH, color, orthophosphate (OP), TBARS and lipid hydroperoxides (LPO) were determined. A fast heating and uSTP resulted in lower CL (p < 0.05). Orthophosphate increased with phosphate incorporation, slow heating and storage (p < 0.05). Encapsulated phosphates and increased coating level reduced OP (p < 0.05). Unencapsulated STP increased CIE a* and pH, whereas uSPP decreased CIE a* and pH (p < 0.05). Encapsulated phosphates and the greater coating level had no effect on the pH in cooked samples. Not increased coating level but encapsulated phosphates decreased lipid oxidation in cooked samples (p < 0.05).     

Tenderness and collagen composition of beef semitendinosus roasts cooked by conventional convective cooking and modeled, multi-stage, convective cooking

Beef semitendinosus roasts were cooked in a forced-air convection oven using conventional or modeled, multi-stage cooking. Conventional cooking was defined as cooking at 163°C to a core endpoint of 65°C. The model method was developed using a finite difference heat and mass transfer model optimized for a three-stage cooking process that included preheating, holding, and finishing. Model cooking resulted in lower (P<0.05) Warner–Bratlzer peak shear force values than conventional cooking (3.3 vs 4.7 kg). Collagen total unaltered fraction was lower (44 vs 55%, P=0.05) and enzyme labile fraction was higher (56 vs 45%, P<0.05) in the model-cooked samples than in conventionally cooked samples. The three-stage cooking process results in a more tender product without adversely affecting product yield.     

Content of heterocyclic amines and polycyclic aromatic hydrocarbons in pork,beef and chicken barbecued at home by Danish consumers

It is a well-known fact that, when meat is barbecued, several harmful components, including heterocyclic amines (HCA) and polycyclic aromatic hydrocarbons (PAH), may be formed. The aim of this study was to determine the HCA and PAH content in meat (pork, chicken and beef) when barbecued at home by Danish consumers according to their normal practice. With regard to HCA, beef contained the highest concentrations of 9H-pyrido[3,4-b]indole (norharman) and 2-methyl-β-carboline (harman), while chicken contained more 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) than pork and beef. The analysis of PAH showed a markedly higher concentration of PAH in beef compared with pork and chicken. In general, a correlation between the HCA content and the surface colour of the meat was found, the darker the colour the higher the HCA concentrations.     

Processing and sensory characteristics of cooked roast beef: effect of breed, age, gender and storage conditions

Two separate experiments investigated the effect of breed (Bos indicus, Bos indicus×and Bos taurus), gender/age and chilled and frozen storage on the processing characteristics of roasts made from inside rounds (semimembranosus, adductor and gracilis muscles). Roasts were injected with a salt/phosphate brine and cooked to an internal temperature of 63 °C. Freezing the meat increased purge lost from the raw meat. Country of origin had no significant effect on cook yield. Sensory evaluations with a US consumer panel indicated only slight sensory differences due to country of origin and breed but a significant effect from storage regime. Tenderness comparisons between breeds were confounded by country of origin and indicated that roast beef from inside rounds from Brahman cattle had lower WBS values than roast beef made from inside rounds from British cattle. Although breed and age/gender often significantly affected processing characteristics of the roasts, differences were small and would have little practical or economic importance for selecting the type of meat for this market sector.     

Influence of dental carcass maturity on carcass traits and meat quality of Nellore bulls

Carcasses of sixty-three Nellore bulls slaughtered at a commercial beef plant were randomly selected by dental classification (2, 4, 6 or 8 permanent incisors) in order to evaluate the influence of dental maturity on carcass traits and meat quality. Carcasses with 8 permanent incisors (p.i.) had greatest values (P<0.05) of carcass weight and longissimus area. Carcasses with 4 and 6 p.i. presented similar values of rib fat thickness being greater (P<0.05) than the other groups. Carcasses with 6 and 8 p.i. presented greater (P<0.05) values of shear force than the other groups. Conversely, carcasses with 2 and 4 p.i. displayed greater (P<0.05) myofibrillar fragmentation index and collagen solubility. Greatest values of thawing loss were observed in carcasses with 2 p.i. (P<0.05) while carcasses with 8 p.i. presented greatest values (P<0.05) of drip loss. Regarding longissimus color, carcasses with 8 p.i presented greatest value (P<0.05) of b*. Data suggests that dental maturity influences carcass traits and meat quality of Nellore bulls.     

Cooked yields, color, tenderness, and sensory traits of beef roasts cooked in an oven with steam generation versus a commercial convection oven to different endpoint temperatures

A CVap steam generation oven was compared with a Blodgett convection oven to examine effects on yields, cooked color, tenderness, and sensory traits of beef Longissimus lumborum (LL), Deep pectoralis (DP), and Biceps femoris (BF) muscles cooked to 1 of 3 temperatures (65.6, 71.1, or 76.7°C). Four roasts were cooked in the CVap for a constant time, and 2 roasts were cooked in the Blodgett until they reached target temperatures (3 replications). Cooking yields were higher (P<0.05) for BF and LL roasts in the CVap. Slice shear force (SSF) for BF roasts was lowest (P<0.05) in the CVap but lowest (P<0.05) for DP roasts in the Blodgett. No oven effect (P>0.05) was found for LL roasts. Sensory tenderness for BF roasts in the CVap was higher (P<0.05) than those in the Blodgett. Juiciness was higher (P<0.05) for LL roasts in the Blodgett. The CVap oven offers some tenderization (BF) and cooking yield advantages (BF and DP) over forced-air convection cooking.     

Multiplex real-time PCR for the detection and quantification of DNA from beef, pork, chicken and turkey

Many meat products are composed of two or more meat species. To determine the proportion of these meat fractions, a quantitative multiplex PCR was developed for the quantification of beef, pork, chicken and turkey. This system proved its applicability, precision and accuracy in examining different meat products from the market. Thus it allows the efficient control of composed meat products in official food control and production control laboratories.