Distribution of intramuscular fat content and marbling within the longissimus muscle of pigs

Pork muscle profiling: pH and instrumental color of the longissimus thoracis is not representative of pH and instrumental color of shoulder and ham muscles

From a population of 351 pork carcasses, 3.0-cm thick chops from the 10th rib location of the longissimus thoracis, faced surfaces of the triceps brachii and serratus ventralis muscles from the boneless shoulder, and faced surfaces of the biceps femoris, semitendinosus, semimembranosus, adductor, rectus femoris, and vastus lateralis muscles from the boneless ham were evaluated for pH and instrumental color (Minolta CR-400). Evaluations were conducted for at least three different locations on each of the muscle samples and averaged before data analysis occurred. The longissimus thoracis had the lowest pH and the lightest and least red color compared with the other eight muscles evaluated in this study (mean differences ranged from 0.98 to 8.70 for L*, 3.98 to 12.56 for a*, and 0.026 to 0.409 for pH). Furthermore, regression analysis suggested that pH and color values for the longissimus thoracis were not adequate predictors for pH and color values obtained from other muscles and therefore consideration should be given to the individual muscles that are of interest.

In-Line Estimation of Fat Marbling in Whole Beef Striploins (Longissimus lumborum) by NIR Hyperspectral Imaging. A Closer Look at the Role of Myoglobin

Fat marbling, the amount, and distribution of intramuscular fat, is an important quality trait for beef loin (Longissimus lumborum) and is closely connected to sensory properties such as tenderness, juiciness, and flavor. For meat producers, it would be of value to grade and sort whole loins according to marbling on the production line. The main goal of this study was to evaluate high-speed NIR hyperspectral imaging in interaction mode (760–1047 nm) for in-line measurement of sensory assessed marbling in both intact loins and loin slices. The NIR system was calibrated based on 28 whole striploins and 412 slices. Marbling scores were assessed for all slices on a scale from 1 to 9 by a trained sensory panel. The calibrated NIR system was tested for in-line measurements on 30 loins and 60 slices at a commercial meat producer. Satisfactory accuracy for prediction of marbling was obtained by partial least squares regression for both slices and whole loins (R² = 0.81 & 0.82, RMSEP = 0.95 & 0.88, respectively). The concentration of myoglobin in the meat and its state of oxygenation has a strong impact on the NIR spectra and can give deviations in the estimated marbling scores. This must be carefully considered in industrial implementation.

Effects of chilling duration on USDA Quality Grade of beef carcasses

Two hundred and nine beef carcasses (BW of 361 ± 53 kg) from crossbred, grain-finished cattle were harvested in a commercial abattoir and subjected to a 96-h spray chilling treatment, conducted at 0 to 3°C in a commercial hot box with a wind speed of 3.1 m/s and 153-lux of fluorescent light. At the 24, 48, 72, and 96 h points of the treatment, the carcasses were analyzed for fatty acid composition, marbling score, core temperature (n = 1), pH, shrinkage, color, and aerobic plate count (n = 50). Carcasses reached 3ºC after 12 to 16 h of chilling. There were minimal changes in shrinkage among time point (-0.4 to 1.2%; P ≤ 0.002), pH (5.56 to 5.69; P ≤ 0.001), and aerobic plate count (APC) (0.1 to 0.7 log; P ˂ 0.001). Initial 24-h grading revealed a grade composition of 21.1% Slight (SL, n = 44), 34.0% Small (SM, n = 71), 17.2% Modest (MT, n = 37), 17.7% Moderate (MD, n = 36), and 10.1% Slightly Abundant (SA, n = 21). With marbling score in numeric values between 200 (Practically Devoid00) and 1100 (Abundant00), carcasses that had SM or greater marbling score at 24 h experienced a deduction of 34 to 60 points by the 96th hour of spray chilling (P ≤ 0.042). Comparatively, the marbling scores of the SL carcasses increased from 442 points at 24 h to 469 points at 96 h. Moreover, SL carcasses had a greater percentage of polyunsaturated fats (PUFA) (P < 0.001). Results indicate that spray chilling for 96 h may slightly increase the marbling score of USDA Select, but has minimal impacts on marbling score of greater USDA quality grades.

An image analysis approach to identification and measurement of marbling in the intact pork loin

An image analysis method for identifying marbling on exposed boneless pork loin surfaces was developed, solving the problem of influences from uneven lean colour. Comparing results from RAW and JPEG images of the mid-loin pork chop showed that, except at very high marbling levels, estimation of %IMF (intramuscular fat) was similar with both image types (R² = 0.72 and 0.74 respectively). Marbling calculated from JPEGs was positively related to %IMF, but also diverged as %IMF increased. Estimations of %IMF at the mid-loin chop from JPEGs of external loin sites showed marbling on the posterior face to be the most strongly related (r = 0.72, P < 0.0001), followed by the ventral surface (r = 0.62-0.64, P < 0.0001), and the anterior face (r = 0.56, P < 0.0001). For on-line application, computing speed is important. This study suggested that an image capture system could be reduced to the capture of a cyan-filtered monochrome JPEG image for analysis.

Anatomical and ontogenetic influences on muscle density

Physiological cross-sectional area (PCSA), an important biomechanical variable, is an estimate of a muscle's contractile force potential and is derived from dividing muscle mass by the product of a muscle's average fascicle length and a theoretical constant representing the density of mammalian skeletal muscle. This density constant is usually taken from experimental studies of small samples of several model taxa using tissues collected predominantly from the lower limbs of adult animals. The generalized application of this constant to broader analyses of mammalian myology assumes that muscle density (1) is consistent across anatomical regions and (2) is unaffected by the aging process. To investigate the validity of these assumptions, we studied muscles of rabbits (Oryctolagus cuniculus) in the largest sample heretofore investigated explicitly for these variables, and we did so from numerous anatomical regions and from three different age-cohorts. Differences in muscle density and histology as a consequence of age and anatomical region were evaluated using Tukey's HSD tests. Overall, we observed that older individuals tend to have denser muscles than younger individuals. Our findings also demonstrated significant differences in muscle density between anatomic regions within the older cohorts, though none in the youngest cohort. Approximately 50% of the variation in muscle density can be explained histologically by the average muscle fiber area and the average percent fiber area. That is, muscles with larger average fiber areas and a higher proportion of fiber area tend to be denser. Importantly, using the age and region dependent measurements of muscle density that we provide may increase the accuracy of PCSA estimations. Although we found statistically significant differences related to ontogeny and anatomical region, if density cannot be measured directly, the specific values presented herein should be used to improve accuracy. If a single muscle density constant that has been better validated than the ones presented in the previous literature is preferred, then 1.0558 and 1.0502 g/cm³ would be reasonable constants to use across all adult and juvenile muscles respectively.

Characterizing the amount and variability of intramuscular fat deposition throughout pork loins using barrows and gilts from two sire lines

The objective was to determine the amount and variability of intramuscular fat (IMF) in a pork loin attributable to anatomical chop location, sex, and sire line. Pigs were sired by commercially available terminal Duroc boars selected for meat quality (MQ; n = 96) or lean growth (LG; n = 96) and equally split between barrows and gilts. After slaughter and fabrication, bone-in chops were removed from four locations of each left-side loin (A = 6th rib, B = 10th rib, C = last rib, and D = 4th lumbar vertebrae). An adjacent pair of chops from each location was collected and evaluated for visual color and marbling, subjective firmness, moisture and extractable lipid (IMF) (anterior chop), and Warner-Bratzler shear force (posterior chop). Data were analyzed using the MIXED procedure of SAS as a split-plot design. Homogeneity of variances was tested on raw data using Levene's test of the GLM procedure and found to be heterogeneous. Thus, a two-variance model was fit using the REPEATED statement of the MIXED procedure, grouped by pig. The mivque(0) option of the VARCOMP procedure was used to calculate the proportion of variability that each factor contributed to the total variance. Barrows (3.64%) produced chops with greater (P < 0.01) IMF content than gilts (3.20%), and barrows (2.14) had greater (P < 0.01) IMF variability than gilts (1.23). Chops from MQ pigs (4.02%) exhibited greater (P < 0.01) IMF content than LG (2.82%), and MQ (1.76) had greater IMF variability (P < 0.01) than LG pigs (0.97). Chops from locations A (3.80%) and D (3.77%) had greater IMF than B (3.34%; P < 0.01), and A, B, and D had greater IMF than C (2.77%; P < 0.01). Variances of IMF also differed (A = 1.44, B = 1.59, C = 1.05, and D = 2.18; P = 0.01) across chop locations. Of the variability in IMF, 33.0% was attributed to sire line, 10.16% to chop location, and 4.01% to sex, with 52.83% not accounted for by these three factors. Location A chops were the most (P < 0.01) tender (2.57 kg) and C chops the least (P < 0.01) tender (2.93 kg), while B and D chops were intermediate and not different from each other. No differences in variability (P = 0.40) of tenderness were observed among chop locations (A = 0.31, kg B = 0.24 kg, C = 0.24 kg, and D = 0.23 kg). These results demonstrated that variability in tenderness values did not reflect the variability of IMF. In conclusion, chop location, sex, and sire line all contribute to the amount and variability of pork loin marbling.

Use of Hermetia illucens larvae as a dietary protein source: Effects on growth performance, carcass traits, and meat quality in finishing pigs

This study investigated the effects of feeding Hermetia illucens larvae (0, 4, and 8%; HI0, HI4, and HI8 groups, respectively) on growth performance, carcass traits, and meat quality of finishing pigs. Results showed that the HI4 diet increased (P < .05) final body weight and average daily gain and decreased (P < .05) feed to gain ratio compared with HI0 and HI8 group. HI4 and HI8 diets increased (P < .05) loin-eye area, marbling scores, and inosine monophosphate content of longissimus thoracis (LT) compared with HI0 diet. The intramuscular fat content was greater (P < .05) in HI4 group than in the HI0 group. Furthermore, HI4 diet up-regulated (P < .05) lipogenic genes and MyHC-IIa mRNA levels in LT compared with HI0 diet. Our results indicated that dietary inclusion of H. illucens larvae has a beneficial impact on growth performance and meat quality, and the underlying mechanism may be due to the altered lipogenic potential induced by H. illucens larvae.

Distribution of Marbling Throughout the M. Longissimus Thoracis et Lumborum of Beef Carcasses Using an Instrument-Grading System

Beef Loin, Strip Loins (IMPS #180; n = 20) with marbling scores between Modest00 and Modest30 at the 12th and 13th rib interface of the M. longissimus thoracis et lumborum (LL) were collected. Each strip loin was fabricated into 6 samples taken perpendicular to the long axis of the LL from the 13th thoracic vertebra to the fifth lumbar vertebra with the cut made on the anterior side of the respective vertebra. A Computer Vision System Cold Camera measured the LL cross-section of each sample location for USDA marbling score, marbling distribution, average marbling fleck size, LL area, LL length (distance medial to lateral), and LL width (distance dorsal to ventral). In the present study, mean LL marbling score decreased (P < 0.05) from the second lumbar vertebrae location to the fifth lumbar vertebrae location. Marbling size and marbling distance were the smallest (P < 0.05) in samples from the 13th thoracic vertebrae location. The LL area and width was largest (P < 0.05) for the samples from the most anterior location and thus decreased (P < 0.05) as the samples became more posterior. Samples from the most posterior end of the strip loin were the longest (P < 0.05) in length. It was observed that marbling score, distribution, and size, as well as, LL area, length, and width vary from anterior to posterior in the strip loin which can have potential marketing implications for food service distributors and retailers.

Evaluation of the sensory attributes along rabbit loin by a trained panel

The aim of this study was to evaluate and quantify variation in sensory attributes along the <em>Longissimus dorsi</em> (LD) muscle in rabbits. A descriptive analysis was performed by a panel of 8 assessors previously trained in the evaluation of rabbit meat. Reference standards used in training for the evaluation of rabbit meat are also described. Sensory attributes rabbit and liver odour, rabbit and liver flavour, toughness, juiciness and fibrousness were assessed in 56 rabbits from a divergent selection experiment for intramuscular fat (28 slaughtered at 9 wk and 28 slaughtered at 13 wk). Immediately after cooking, loins were cut lengthwise into 4 equidistant pieces from caudal to cranial end (LD₁, LD₂, LD₃ and LD₄). Assessors were able to detect and quantify a longitudinal sensory variation in muscle LD. Caudal extreme LD₁ was tougher and more fibrous than LD₂, LD₃ and LD₄, and less juicy than LD₃ and LD₄. The greatest variation was found between caudal and cranial ends, with LD₁ being 9% tougher (P=0.99), 11% more fibrous (P=1.00) and 12% less juicy (P=0.99) than LD₄. Assessors found few variations along LD muscle in flavour and odour attributes. Location LD₃ showed 9% greater rabbit odour (P=0.99) and flavour (P=0.97) than LD₄, and 8% greater rabbit odour than LD₂ (P=0.97). Our results highlight the importance of randomisation within muscle location in sensory studies on rabbit LD muscle, as there is considerable sensory variation along this muscle.

Effect of oregano essential oil supplementation to a reduced-protein, amino acid-supplemented diet on meat quality, fatty acid composition, and oxidative stability of Longissimus thoracis muscle in growing-finishing pigs

This study investigated the effects of reduced-protein, amino acid-supplemented diet supplementation with oregano essential oil (OEO) in pigs, from growing period to slaughter, on the meat quality, fatty acid composition, and oxidative stability of Longissimus thoracis (LT) muscle. Thirty-six barrows were randomly divided into three experimental treatments, namely, normal protein diet (NPD), reduced-protein, amino acid-supplemented diet (RPD), and identical RPD supplemented (250mg/kg feed) with OEO (OEO) treatments. Dietary RPD and OEO increased the b*_45min, tenderness, overall acceptance, and intramuscular fat (IMF) content of pork compared with dietary NPD. The percentage of n-3 polyunsaturated fatty acid (n-3 PUFA) and the percentage of monounsaturated fatty acid in OEO muscle were higher and lower than those in RPD muscle, respectively. Dietary OEO improved oxidative stability, total antioxidative capacity, and catalase but decreased drip loss in LT muscle. Results indicated that dietary OEO enhanced the sensory attributes and anti-oxidative status of pork meat by improving IMF and n-3 PUFA proportion and antioxidative capacity.

Identification and characterization of novel single nucleotide polymorphism markers for fat deposition in muscle tissue of pigs using amplified fragment length polymorphism

Objective

This study was conducted to identify and evaluate the effective single nucleotide polymorphism (SNP) markers for fat deposition in the longissimus dorsi muscles of pigs using the amplified fragment length polymorphism (AFLP) approach.

Methods

Sixty-four selective primer combinations were used to identify the AFLP markers in the 20 highest- and 20 lowest-intramuscular fat (IMF) content phenotypes. Five AFLP fragments were converted into simple codominant SNP markers. These SNP markers were tested in terms of their association with IMF content and fatty acid (FA) composition traits in 620 commercially crossbred pigs.

Results

The SSC7 g.4937240C>G marker showed an association with IMF content (p<0.05). The SSC9 g.5496647_5496662insdel marker showed a significant association with IMF content and arachidonic levels (p<0.05). The SSC10 g.71225134G>A marker revealed an association with palmitoleic and ω9 FA levels (p<0.05), while the SSC17 g.61976696G>T marker showed a significant association with IMF content and FA levels of palmitoleic, eicosenoic, arachidonic, monounsaturated fatty acids, and ω9 FA levels. However, no significant association of SSC8 g.47338181G>A was observed with any IMF and FA levels in this study.

Conclusion

Four SNP markers (SSC7 g.4937240C>G, SSC9 g.5496647_5496662insdel, SSC10 g.71225134G>A, and SSC17 g.61976696G>T) were found to be associated with IMF and/or FA content traits in commercially crossbred pigs. These findings provide evidence of the novel SNP markers as being potentially useful for selecting pigs with the desirable IMF content and FA composition.

Effect of Bacillus subtilis Natto on Meat Quality and Skatole Content in TOPIGS Pigs

This study investigated the effect of Bacillus subtilis (B. subtilis) natto on meat quality and skatole in TOPIGS pigs. Sixty TOPIGS pigs were randomly assigned to 3 groups (including 5 pens per group, with 4 pigs in each pen) and fed with basic diet (control group), basic diet plus 0.1% B. subtilis natto (B group), and basic diet plus 0.1% B. subtilis natto plus 0.1% B. coagulans (BB group), respectively. All pigs were sacrificed at 100 kg. Growth performance, meat quality, serum parameters and oxidation status in the three groups were assessed and compared. Most parameters regarding growth performance and meat quality were not significantly different among the three groups. However, compared with the control group, meat pH24, fat and feces skatole and the content of Escherichia coli (E. Coli), Clostridium, NH3-N were significantly reduced in the B and BB groups, while serum total cholesterol, high density lipoprotein, the levels of liver P450, CYP2A6, and CYP2E1, total antioxidant capability (T-AOC) and glutathione peroxidase and Lactobacilli in feces were significantly increased in the B and BB groups. Further, the combined supplementation of B. subtilis natto and B. coagulans showed more significant effects on the parameters above compared with B. subtilis, and Clostridium, and NH3-N. Our results indicate that the supplementation of pig feed with B. subtilis natto significantly improves meat quality and flavor, while its combination with B. coagulans enhanced these effects.

Alternative method for intramuscular fat analysis using common laboratory equipment

A procedure to quantify intramuscular fat was developed using common inexpensive laboratory equipment. Three homogenization methods of lyophilized muscle samples (Ball-mill, Grinder and Mortar) and two extraction methods (Ball-mill or Vortex) were used in turkey meat and pork. Two-hundred mg of lyophilized and homogenized samples were accurately weighed and mixed with 1.5 mL of dichloromethane-methanol (8:2) and shaken either in a Mixer Mill (MM400, Retsch Technology) or in a Vortex. The final mixture was separated by centrifugation. Solvent was evaporated under a nitrogen stream and lipid content was gravimetrically determined. Besides, it was checked that the fatty acid profile was not altered by the protocol used. Moreover, the analysis of 4 replicas from the same sample showed different variation coefficients (16-29%) for the new procedures proposed over a wide range of IMF content. The combination of Grinder and Vortex methodologies can be proposed as a simple and inexpensive alternative to previous ones.

A laboratory efficient method for intramuscular fat analysis

A new procedure to extract intramuscular fat (IMF) was developed to minimize sample amount, solvent use and time of analysis. Lyophilised samples (200mg) were accurately weighed in a safe-lock micro test tube, homogenized in 1.5 mL dichloromethane-methanol (8:2) and mixed in a mixer mill (MM400, Retsch technology). The final biphasic system was separated by centrifugation (8 min, 10,000 rpm). The extraction was repeated three times. Solvent was evaporated under nitrogen stream and lipid content was gravimetrically determined. Results from 64 determinations were compared to those obtained with other referred method and showed a linear response over the whole range of IMF content (1.6-6.9 g/100 g sample). Moreover, the analysis with different methodology of six replica from the same sample showed lowest variability (standard deviation intra-method) for the new methodology proposed over a wide range of IMF content. A cost and time efficient lipid extraction procedure was developed without loss of precision and accuracy and with a fatty acid profile comparable to other protocols.