An assessment of simple referee methods for the prediction of lean in pig carcasses

A study was carried out in which carcass characteristics of 36 gilts were evaluated: 18 originated from the Hungarian 'Hungahyb' cross-breed, another 18, with undefined genetic background, from small private household plots. Two, rather simple substitute reference methods, called referee methods, were evaluated: measurement of carcass weight without skin and subcutaneous fat ('meat + bone'), and measurement of carcass weight without skin, subcutaneous fat and bone ('boneless meat'). Both methods gave a rather close relationship with the Kulmbach reference lean; however, removal of bone had presumably a beneficial effect on stability of prediction. The importance of preliminary information in quantitative form, giving a theoretical background for prediction equations, was presented as an example. Simple material balances could be formulated between reference lean and 'meat + bone' or 'boneless meat' content. Such material balances could not be set up with the indirect, rapid surrogate methods using mainly linear measurements (e.g. fat and muscle thickness, etc.) For this reason, as several other publications demonstrated, these latter methods seem to be more susceptible to bias than the referee methods. By determining the lipid content of the homogenised 'boneless meat' component, a 'lean' value adjusted to 3% fat content could be calculated from data which was compared to the dissected reference lean standardised also to contain 3% fat. These relationships, for several reasons discussed in this paper, were not as close as expected. So, further studies are needed to reveal these discrepancies.     

Comparison of different devices for predicting the lean meat percentage of pig carcasses

Lean meat percentage (LMP) is the criterion for carcass classification and it must be measured on line objectively. The aim of this work was to compare the error of the prediction (RMSEP) of the LMP measured with the following different devices: Fat-O-Meat’er (FOM), UltraFOM (UFOM), AUTOFOM and VCS2000. For this reason the same 99 carcasses were measured using all 4 apparatuses and dissected according to the European Reference Method. Moreover a subsample of the carcasses (n = 77) were fully scanned with X-ray Computed Tomography equipment (CT). The RMSEP calculated with cross validation leave-one-out was lower for FOM and AUTOFOM (1.8% and 1.9%, respectively) and higher for UFOM and VCS2000 (2.3% for both devices). The error obtained with CT was the lowest (0.96%) in accordance with previous results, but CT cannot be used on line. It can be concluded that FOM and AUTOFOM had better accuracy than UFOM and VCS2000.     

Virtual dissection of pig carcasses

This paper proposes the use of computed tomography (CT) as a reference method for estimating the lean meat percentage (LMP) of pig carcasses. The current reference is manual dissection which has a limited accuracy due to variability between butchers. A contextual Bayesian classification scheme is applied to classify volume elements of full body CT-scans of pig carcasses into three tissue types. A linear model describes the relation between voxels and the full weight of the half carcass, which can be determined more accurately than that of the lean meat content. Two hundred and ninety-nine half pig carcasses were weighed and CT-scanned. The explained variance of the model was R²=0.9994 with a root-mean-squared error of prediction of 83.6 g. Applying this method as a reference will ensure a more robust calibration of sensors for measuring the LMP, which is less prone to variation induced by manual intervention.     

Relationships between chemical composition and physically separated tissues of the pig carcass

Data from the physical and chemical dissection analysis of 50 Large White and 50 Hampshire × Large White carcasses, comprising equal numbers of gilts and castrates, slaughtered at 90 kg liveweight, are presented. The right-hand side of each carcass was dissected into lean, fat and bone and the combined tissues were then minced and chemically analysed for moisture, protein, ether extract and ash. Statistical relationships between the two methods of carcass analysis, except those between bone and ash, were not influenced by sex or breed type. Overall regression equations, i.e. ignoring sex and breed type, for the prediction of percentage lean from moisture, protein and ether extract percentages of the carcasses, had residual standard deviations of 1·26, 1·78 and 1·11, respectively, and corresponding values for the prediction of percentage carcass fat were 1·05, 1·68 and 0·74. Residual standard deviations for predicting percentages of moisture and protein in the carcass from percentage lean content were 1·07 and 0·46 and that for the prediction of percentage ether extract from fat percentage of the carcass was 1·20. Corresponding relationships between bone and ash percentages of the carcass were less satisfactory for predictive purposes.     

Enhancement of lean characteristics of veal carcasses by electrical stimulation

Forty Holstein vealers (approximately 16 weeks of age) were slaughtered, skinned, split longitudinally and one side was electrically stimulated (700 V, 2 A and seventeen impulses) for 1 min. Internal temperatures of the rib and round were recorded at 1 h and 24 h post mortem. Approximately 24 h post mortem, lean colour scores were assigned to the cross-section of the longissimus muscle at the 11th-12th rib interface, to the outside surface of the biceps femoris muscle and to the rectus abdominis and transverse abdominis muscles of the flank; lean texture and firmness scores were also assigned to the cut surface of the longissimus muscle. 'House grades' were assigned to each side of each carcass by plant personnel. Initial (1 h) rib and round temperatures were significantly higher for the electrically stimulated sides; however, at 24 h, neither round nor rib temperatures differed between control and electrically stimulated sides. Lean colour, firmness and texture scores for longissimus muscles were significantly (P < 0·0001) improved by electrical stimulation. Electrically stimulated sides also had lighter lean colour scores in the rectus and transverse abdominis and biceps femoris muscles. Electrical stimulation increased the number of carcasses receiving the top 'house grade' and reduced the number of carcasses in the lowest 'house grade'. These data indicate that electrical stimulation will improve lean colour, firmness and texture of veal carcasses when ribbed and evaluated after a 24 h chill.     

Contamination of freshly slaughtered pig carcasses with human pathogenic Yersinia enterocolitica

Evidence is presented for the extent of contamination of freshly slaughtered pig carscasses with human pathogenic Yersinia enterocolitica and shows the significance of faecal contamination as a source of infection. Swab samples collected from the rectum and the surface of a total of 1458 pig carcasses were examined for the presence of human pathogenic Y. enterocolitica Y. enterocolitica, biovar IV, serogroup 0:3, were isolated from the rectum of 360 pigs (24.7%). The organism was isolated from carcass surfaces with varying frequencies depending on the evisceration technique. Manual evisceration was found to correspond with high frequencies of contamination: 26.3% on the medial hind limb and 12.9% on the split sternum. The use of a mechanised bung cutter was found to reduce the rate of contamination, especially when the bung cutter was used in connexion with enclosing the anus and rectum in a plastic bag to minimise faecal contamination. When carcasses were eviscerated in this way, it was possible to reduce carcass contamination to 1.9% on the medial hind limb, 1.0% in the pelvic duct, and 2.2% on the split sternum.     

Prediction of lean and fat composition in swine carcasses from ham area measurements with image analysis

Video images of ham cross-sections were recorded from 71 pork carcasses (ranging in weight from 72 to 119 kg). Three sets of prediction equations were developed to estimate pork carcass lean and fat composition from video image analysis (VIA) of ham cross-sectional area measurements, 10th rib back fat depth (TENFAT) and hot carcass weight (HCKg). Carcass data of dissected lean and fat in the four primal cuts (ham, loin, Boston button and picnic shoulder) were used as dependent variables in establishing regression equations. The first set of equations combined VIA ham measurements and total ham weight (HTKg). Regression models containing the single variable HTKg times ham percentage lean area (Vol. 1) or HTKg times ham percentage fat area (Vol. 2) accounted for 88% and 68% of the variation in total carcass lean weight (CLKg) and total carcass fat weight (CFKg) from the right side of each carcass, respectively. The second set of equations combined VIA ham measurements and TENFAT (cm). Multiple regression models involving TENFAT, Vol. 1, and Vol. 2 accounted for 91% and 90% of the variation in CLKg and CFKg. The third set of equations used VIA ham measurements, TENFAT and HCKg. Carcass lean weight was best predicted by HCKg, TENFAT, and ham lean area (HLA) (R² = .92). Carcass fat weight was best predicted by HCKg, TENFAT, and Vol. 2 (R² = .91). Overall correlations showed a high association between Vol. 1 and CLKg (r = .94, P < .0001) and Vol. 2 and CFKg (r = .83, P < .0001). Ham lean area was related to CLKg (r = .74, P < .0001) and ham fat area to CFKg (r = .81, P < .0001). The results of this study indicated video image analysis of ham cross-section slices combined with backfat depth at the 10th rib can be used for accurate estimation of total carcass lean or fat composition.     

Predicting the weight of lean meat in lamb carcasses and the suitability of this characteristic as a basis for valuing carcasses

The carcasses of 138 lambs were dissected into fat, muscle and bone as the basis for developing a model to estimate the weight of lean meat (muscle and intramuscular fat). The lambs represented two sexes (70 wethers, 68 ewes) and three sire genotypes (67 Poll Dorset, 39 Suffolk, 32 Wiltshire Horn) all from Border Leicester × Polwarth × Booroola type ewes. Hot carcass weight (HWT) was found to explain the majority of the variation in the weight of lean meat. When measures of subcutaneous fat depth at different sites were used as predictors in addition to HWT, the accuracy with which lean meat yield could be estimated was found to increase by a small amount. There was, however, little difference in their individual value as predictors. The area of the M. longissimus thoracis et lumborum at the twelfth-thirteenth rib was found to account for the significant breed type difference between Poll Dorset and Suffolk sired lambs when included in a multiple regression with HWT and the GR measurement (tissue thickness at the twelfth rib 110 mm from the midline). The final model produced an R(2) = 0·92 and an RSD = 0·45 kg for the 106 lambs. Using the model for the 106 lambs, the estimated (from the model) and actual values of lean meat for the Wiltshire Horn sired lambs were compared. The correlation coefficient between the values was r = 0·97 and the RSD was 0·31 kg. This shows that for second cross lambs as used in this study the fitted model exhibits a degree of general validity and stability. An overall model for the 138 lambs produced an R(2) = 0·92 an RSD = 0·43 kg. The potential for pricing meat on the basis of lean meat yield is discussed, with particular emphasis on the current developments in assessment of lamb carcasses in Australia.     

Effect of logistic slaughter on Salmonella contamination on pig carcasses

Previous studies have shown that infected pigs are the source of carcass and slaughterhouse environment contamination by Salmonella. The present study tried to evaluate the effect of a logistic slaughter, organised according to Salmonella seroprevalence, on Salmonella contamination on carcasses. The study was performed at the beginning of slaughtering during three consecutive days. Low risk herds (8 batches) were slaughtered on day I, high risk herds (6 batches) on day II, and finally, moderate risk herds (5 batches) were slaughtered on day III. Each slaughtering day, holding pens, five points of the slaughter line, and 80 carcasses were sampled. The number of positive carcasses on days I, II and III was 7 (8.8%), 5 (6.3%) and 19 (24.4%) respectively. The results evidenced no clear effect of the logistic slaughter on carcass contamination, with a three times higher risk of finding a positive carcass when moderate Salmonella risk batches were slaughtered. Carcass contamination in low risk herds was linked to the contamination of holding pens and the slaughter line activities. On the other hand, Salmonella was not detected in any of the sampled carcasses in three out of six high risk Salmonella batches, showing that proper slaughtering practices can prevent carcass contamination. The experience reported here, demonstrates that apart from an accurate batch separation according to their seroprevalence levels, strict measures for cleaning and disinfection in the lairage and the slaughterhouse facilities are needed when logistic slaughter is performed.     

Microbiological contamination of pig and cattle carcasses in different small-scale Swiss abattoirs

A total of 750 pig carcasses and 535 cattle carcasses from 17 small-scale abattoirs were sampled by excision at four sites (pig: neck, belly, back, ham; cattle: neck, brisket, flank, rump). Samples were examined for total viable counts (TVC) and Enterobacteriaceae. Mean TVCs ranged from 2.4 to 4.2 log(10)CFUcm(-2) on pig carcasses and from 2.7 to 3.8 log(10)CFUcm(-2) on cattle carcasses. With regard to EU Regulation (EC) No 2073/2005, TVCs were mainly considered satisfactory (pig: 81.3%; cattle: 71.4%). Amongst sites, the back (pigs) and neck (cattle) tended to yield higher TVCs. Enterobacteriaceae were detected in low counts on 23.9% of pig carcasses and 21.7% of cattle carcasses. Amongst abattoirs, Enterobacteriaceae prevalence on pig and cattle carcasses ranged from 2.0% to 56.0% and from 0.0% to 55.0%, respectively. Consequently, criteria of the EU Regulation proved to be a suitable tool for the appraisal of microbiological results (TVCs) from pig and cattle carcasses from small-scale abattoirs. Because the occurrence of Enterobacteriaceae on carcasses was too infrequent to ensure log normality, frequencies should be compared for these organisms.     

Microbial contamination of carcasses and equipment from an Iberian pig slaughterhouse

The microbial contamination of carcasses and equipment has been studied in an industrial slaughterhouse of Iberian pigs. Samples of the surface of carcasses were taken at different stages of the process and aerobic plate count at 37 degrees C (APC), Enterobacteriaceae-count (E-count) and Escherichia coli-count (EC-count) were determined. It was demonstrated that in scalding and singeing the APC decreased (P < 0.01), while in the dehairing it increased (P < 0.01). The E-count and EC-count decreased in the scalding but increased in the evisceration (P < 0.001). The implementation of good manufacturing practices (GMP) in the stages of closure of the anus and evisceration significantly decreased the EC-count. It changed from 61.1% in carcasses without GMP that had counts higher than 1 log CFU/cm2 to only 7.4% in GMP carcasses. A final wash of the carcasses with potable water at high pressure (the only decontaminating treatment permitted in the European Union) was tested and failed to decrease the counts. It was also demonstrated that cleaning and disinfection of the dehairing and scraping machines is not effective.     

Influence on meat colour of spray-chilling the surface of pig carcasses

The present study examines the influence of spray-chilling on the surface colour of the musculature, skin and spinal spongiosa of swine carcass halves. Thirty swine halves, of the commercial classification U, were divided into six experimental groups and chilled under varying conditions over a period of 20 h. Three of the experimental groups were sprayed periodically with 810 g drinking water within a 4-h chilling phase. The other three served as unsprayed control groups. Oxygenation of the myoglobin to oxymyoglobin was accelerated by spraying the surface of the musculature. Spray-chilling conditions had no influence on the formation of metmyoglobin. The colour of the sprayed ham musculature became lighter after 4 h of chilling. Red- and yellow-values decreased. There were no significant differences in the colour values after 20 h of chilling. The surface of the skin became lighter after spray-chilling. The spraying had no influence on the colour of the spinal spongiosa.     

Characteristics of Staphylococcus hyicus strains isolated from pig carcasses in two different slaughterhouses

In a previous study, we showed that coagulase positive staphylococci, which are often used as indicators for Staphylococcus aureus, are frequently found on pig carcasses. Further characterization of the strains identified only a minor part as S. aureus. Selected non-S. aureus strains were all identified as Staphylococcus hyicus, However, two studies described in this species strains that produce staphylococcal enterotoxins. The aim of the present study was to further characterize such coagulase positive S. hyicus strains isolated from pig carcasses and to assess the results for their food safety relevance. A total of 189 strains from two abattoirs were characterized. Phenotypically, 98.9% showed non-pigmented colonies, 99.5% no haemolysis and 67.7% were egg yolk-positive. DNase activity was found in all but one isolate. Only five of the 189 strains were resistant to the antimicrobials tested. One strain harboured the mecA gene. Exfoliative toxin genes were detected in 31 (16.4%), S. aureus enterotoxin genes in none of the strains.The PFGE genotyping results show only a limited number of clusters. Cluster I included more than 50% of the strains. The fact that similar or closely related PFGE patterns of S. hyicus can be found on carcasses after bleeding in both abattoirs indicates the occurrence of widespread strains in the Swiss pig population. Moreover, the genotyping results revealed a remarkable homogeneity in S. hyicus strains isolated from different process stages in abattoir B, which could indicate a recontamination problem with persisting strains.     

Contamination of carcasses, offals, and the environment with yadA-positive Yersinia enterocolitica in a pig slaughterhouse

This study was carried out in order to evaluate the contamination of the pig-slaughtering line with pathogenic Yersinia enterocolitica carrying the yadA gene. A total of 292 samples were collected from the slaughterhouse; 131 swab samples from pig carcasses, ears, livers, kidneys, and hearts; 89 swab samples from the environment; and 72 sedimentation samples from the air. All surface samples were studied with both the polymerase chain reaction (PCR) and culture methods. The contamination rate of edible pig offals was high with both methods. Using PCR, the detection rates of yadA-positive Y. enterocolitica for livers, kidneys, and hearts were 38, 86, and 63%, respectively, and using the culture method, the detection rates were 31, 69, and 50%, respectively. Pathogenic Y. enterocolitica was also detected from different environmental sites in the slaughterhouse. Using PCR, 13% of the surface samples from the environment were contaminated with yadA-positive Y. enterocolitica. PCR-positive samples were found on the brisket saw, the hook from which the pluck set (heart, lungs, esophagus, trachea, diaphragm, liver, kidneys, and tongue with tonsils) hang, the knife used for evisceration, the floors in the eviscerating area and the weighing area, the meat-cutting table, the aprons used by trimming workers, the computer used in the meat-inspection area, and the coffeemaker used by slaughterhouse workers. The respective detection rate (6%) was considerably lower when we used the culture method. Pathogenic Y. enterocolitica was isolated from the air in the bleeding area. Bioserotype 4/O:3 was the only pathogenic bioserotype isolated in this study. A total of 113 isolates of type 4/O:3 were characterized with pulsed-field gel electrophoresis using NotI and XbaI digests. By combining these profiles, nine different pulsotypes were obtained, the most common of which (1a) was found in 19 (61%) of 31 samples from different sites. This is the same type that has dominated in pig tonsils, which suggests that tonsils may be the source of Y. enterocolitica contamination in the slaughterhouse. The four pulsotypes (1a, 4g, 6g, and 19q) found on edible offals were the same as those found in tonsils, which supports our hypothesis that tonsils are the contamination source for the liver, heart, and kidneys.     

Effect of chilling shrinkage of pig carcasses on yield of Wiltshire bacon

Summary. Twenty pig carcasses were taken fresh from the slaughterline and split into two sides. One-half of each pig was quick-chilled and the other rapidly chilled. Trimming, brine injection and curing were closely controlled and weights at various stages of processing were accurately measured.
Overall, there was no difference in the final weight of bacon produced by the two chilling systems. There was some variation in the curing weight loss of different pigs, pH appearing to be a factor.