Muscle characteristics only partially explain color variations in fresh hams

Time of dehairing alters pork quality development

Studies investigating the effect of scald time on pork quality are confounded with time of dehairing. To understand better pork quality development and two-toning in hams, twenty-four carcasses were assigned to an 8- or 16-min dwell time prior to the dehairing, with or without scalding (n = 6 per trt). Semimembranosus (SM) muscles were collected following dehairing and at 24 h postmortem. Protracted time to dehair improved ultimate pH (pH_u; P < 0.005) and reduced (P < 0.05) color variation. One hundred forty-two carcasses were then subjected to protracted (control, 10-min) dwell times (15-min, or 20-min) in an industrial setting. Lightness was improved with 15-min dwell times compared to control, however 20-min dwell decreased the pH_u (P < 0.001), increased lightness (P < 0.05), and percent purge (P < 0.001) in the SM. Also, lightness of the longissimus muscle (LM) increased (P < 0.001) with dwell time. These data show time to dehairing impacts pork quality development and suggest dehairing may be critical to quality development in a muscle-dependent manner.

Effect of rosemary addition on the sensorial and physicochemical qualities of dry-cured ham slices. Measurement of camphor transfer

This study determined the effect of three concentrations (R1: high, R2: medium and R3: low) of rosemary added to dry-cured ham slices vacuum packaged. pH and the colour parameters were evaluated at 0, 7, 14, 28 and 60 days of storage; visual appearance, odour, flavour and camphor content were assessed at days 7, 14, 28 and 60. The rosemary concentration changed the colour parameters, significantly altering the visual appearance (p < 0.001 at 7 and 14 days; p < 0.5 at day 28), but did not affect the pH, neither odour nor flavour. Nevertheless, significant differences were found with the time on R1 and R2 in odour (p < 0.01 and p < 0.001, respectively) and in flavour (p < 0.001). Camphor content was similar in all samples but changed over the time in R1 (p < 0.001) and R2 (p < 0.01). In conclusion, despite the differences observed, it is evident that the addition of this spice was to the liking of the panellists, in any of the concentrations used.

Reduced scald time does not influence ultimate pork quality

Fresh pork color is a function of pigment, and the pH and temperature conditions in the carcass postmortem. To explore the role of scald on color development, carcasses (n = 16) were subjected to either a 4- or 8-min scald. Semimembranosus (SM) muscle samples were collected before and after scalding, and at 24 h postmortem. A 50% reduction in scald time resulted in lighter color (L*) across the muscle early postmortem (P < 0.001), yet the 8-min scald treatment was lighter (P = 0.001) at 24 h. An interaction between scald time and sampling time showed in an increase in L* values at 4-min immediately following scald (P < 0.001). Two-hundred carcasses were then subjected to a modified scald time (6.5 min, or 7.5 min) in an industrial setting. Lowering scald time failed to recapitulate results. In fact, darker meat (L* value; P = 0.0166) was noted in the SM across longer scalds. These data suggest modest changes in scald time may not be responsible for changes in pork quality development.

Inherent factors influence color variations in semimembranosus muscle of pigs

Variations in color, though a quality frustration, are common across the face of fresh and processed hams. Herein, we measured objective color across the semimembranosus (SM) muscle early postmortem and at 1440 min, then compared these differences against biochemical and metabolic characteristics responsible for pork quality development. Color (L*, a*) differed (P < 0.001) by zone and time but no interaction was evident. Lactate content and pH were highly correlated (R² = 0.92) at 30 min, but weakened (R² = 0.161412) by 1440 min. Lactate anaplerosis was not responsible for this lack of relationship. Glycolytic potential also differed across zone (P < 0.001) and time (P < 0.005). Differences in myoglobin expression and abundance, as well as mitochondrial DNA were notable (P < 0.05) across zone. These data suggest inherent differences in SM muscle are key determinants of ham color variation, while postmortem metabolism may play a lesser role in driving this quality attribute.

Transcriptomic analysis for pork color – the ham halo effect in biceps femoris

Pork color is a major indicator of product quality that guides consumerpurchasing decisions. Recently, industry has received an increase in consumercomplaints about the lightness and non-uniformity of ham color, primarilylighter color in the periphery termed “ham halo” that is not caused bymanufacturing procedures. This effect is seen in fresh and processed hams andthe outer, lighter muscle is associated with lower myoglobin concentration, pHand type I fibers. The objective of this study was to identify differences ingene expression profiles between light and normal colored portions of biceps femoris muscle from pork hams.RNA-sequencing was performed for paired light and normal colored muscle samplesfrom 10 animals showing the ham halo effect. Over 50 million paired-end reads(2x75bp) per library were obtained. An average of 99.74% of trimmed high-qualityreads were mapped to the Sscrofa 11.1 genome assembly. Differentially expressedgenes (DEGs) were identified using both the DESeq2 and GFOLD software packages.A total of 14,049 genes were expressed in bicepsfemoris; 13,907 were expressed in both light and normal muscle, while 56and 86 genes were only expressed in light and normal muscle, respectively. Analysiswith DESeq2 identified 392 DEGs with 359 genes being more highly expressed innormal colored muscle. A total of 61 DEGs were identified in the DESeq2analysis and also were identified in at least 7 of the 10 individual animalanalyses. All 61 of these DEGs were up-regulated in normal colored muscle. Geneontology (GO) enrichment analysis of DEGs identified the transition betweenfast and slow fibers, and skeletal muscle adaptation and contraction as themost significant biological process terms. The evaluation of gene expression byRNA-Seq identified DEGs between regions of the biceps femoris with the ham halo effect that are associated with thevariation in pork color.

New Insights in Muscle Biology that Alter Meat Quality

Fresh meat quality is greatly determined through biochemical changes occurring in the muscle during its conversion to meat. These changes are key to imparting a unique set of characteristics on fresh meat, including its appearance, ability to retain moisture, and texture. Skeletal muscle is an extremely heterogeneous tissue composed of different types of fibers that have distinct contractile and metabolic properties. Fiber type composition determines the overall biochemical and functional properties of the muscle tissue and, subsequently, its quality as fresh meat. Therefore, changing muscle fiber profile in living animals through genetic selection or environmental factors has the potential to modulate fresh meat quality. We provide an overview of the biochemical processes responsible for the development of meat quality attributes and an overall understanding of the strong relationship between muscle fiber profile and meat quality in different meat species.

Sire Variation in the Severity of the Ham Halo Condition

A study was conducted to examine genetic variation in the ham halo condition. The distal portion of the biceps femoris was sampled by taking cores (2.54-cm diameter) from progeny (n = 1,016) from a Duroc meat quality–focused line. Commission Internationale de l ́Éclairage (CIE; “International Commission on Illumination”) color-space values (L*, a*, and b*) and myoglobin concentration were measured on the halo (“Halo”) and inside (“Inside”) portion of each core. The Halo portion of the biceps femoris had greater L* and b* and lesser a* and myoglobin content (all P &lt; 0.001) than the Inside portion. Sires with 11 or more progeny were compared. The sire × muscle-location interaction affected (P &lt; 0.001), L*, a*, and myoglobin concentration. Sire progeny groups differed for each trait in both portions of the muscle, but differences in the Halo portion of the muscle were not mirrored in the Inside portion of the muscle. Similarly, sire group affected the magnitude of the difference in L* (P = 1.4 × 10−4) and a* (P = 9.0 × 10−6) between the Halo and Inside portions of the muscle and tended (P = 0.08) to affect myoglobin content. However, the largest sire-group differences were not necessarily seen in the sires with the highest means for these attributes. Thus, selecting for myoglobin concentration, L*, or a* content in the Halo portion of the biceps femoris muscle would be an effective strategy for reducing the severity of the ham halo condition.