EFFECTS OF ENDPOINT TEMPERATURE, pH, AND STORAGE TIME ON COOKED INTERNAL COLOR REVERSION OF PORK LONGISSIMUS CHOPS

The color of fresh pork: Consumers expectations, underlying farm-to-fork factors, myoglobin chemistry and contribution of proteomics to decipher the biochemical mechanisms

The color of fresh pork is a crucial quality attribute that significantly influences consumer perception and purchase decisions. This review first explores consumer expectations and discrimination regarding pork color, as well as an overview of the underlying factors that, from farm-to-fork, contribute to its variation. Understanding the husbandry factors, peri- and post-mortem factors and consumer preferences is essential for the pork industry to meet market demands effectively. This review then delves into current knowledge of pork myoglobin chemistry, its modifications and pork discoloration. Pork myoglobin, which has certain peculiarities comparted to other meat species, plays a weak role in determining pork color, and a thorough understanding of the biochemical changes it undergoes is crucial to understand and improve color stability. Furthermore, the growing role of proteomics as a high-throughput approach and its application as a powerful research tool in meat research, mainly to decipher the biochemical mechanisms involved in pork color determination and identify protein biomarkers, are highlighted. Based on an integrative muscle biology approach, the available proteomics studies on pork color have enabled us to provide the first repertoire of pork color biomarkers, to shortlist and propose a list of proteins for evaluation, and to provide valuable insights into the interconnected biochemical processes implicated in pork color determination. By highlighting the contributions of proteomics in elucidating the biochemical mechanisms underlying pork color determination, the knowledge gained hold significant potential for the pork industry to effectively meet market demands, enhance product quality, and ensure consistent and appealing pork color.

Effects of chitosan-based coatings incorporated with ɛ-polylysine and ascorbic acid on the shelf-life of pork

Chitosan is a food thickener with film-forming ability and antibacterial activity. ɛ-Polylysine is a preservative with broad-spectrum antibacterial activity. Ascorbic acid is a food antioxidant. In this study, pork chunks were treated with four dipping solutions, i.e. purified water (control), 0.2% ascorbic acid (treatment-1), 0.02% ɛ-polylysine (treatment-2), and 0.4% chitosan + 0.02% ɛ-polylysine + 0.2% ascorbic acid (treatment-3), and stored at 3 °C for 12 days. All treatments suppressed bacterial growth, increases in pH and total volatile basic nitrogen (TVB-N) and thiobarbituric acid reactive substances and decreases in the red indices of pork chunks compared with the control during refrigeration. Based on the national standards of total bacterial number and TVB-N of pork, treatment-3 extended the shelf-life of pork chunks by six days compared with the control. The results verified that chitosan-based coatings may be a practical method for the preservation of pork chunks during refrigeration.

Characteristics of Pork Muscles Cooked to Varying End-Point Temperatures

M. biceps femoris (BF), m. semimembranosus (SM) and m. semitendinosus (ST) from fresh pork ham were evaluated for characteristics of quality after cooking to an internal endpoint temperature of 62 °C or 73 °C. Fresh ham muscles from the left side (N = 68) were cut into 2.54 cm thick chops and allocated to cooking loss, Warner–Bratzler shear force (WBSF), pH and instrumental cooked color analysis. Cooking losses were greater (p < 0.0001) for SM and chops cooked to an internal temperature of 73 °C (p < 0.0001), whereas WBSF did not differ (p = 0.2509) among the three muscles, but was greater (p < 0.0001) in chops cooked to 73 °C. Fresh muscle’s pH was greater (p < 0.05) in ST than BF or SM. Lastly, the interactive effect (p < 0.05) of muscle × endpoint temperature for ST chops cooked to 73 °C was lighter (L*), but, when cooked to 62 °C, they were more red (a*), more yellow (b*) and incurred less color change from red to brown than BF or SM. The current results suggest it is plausible for BF, SM and ST to be considered for alternative uses instead of traditional value-added manufacturing.

The intrinsic cause of color fading in sliced cooked cured beef during chilled storage

The relationship between color change and other physical and chemical characteristics of sliced cooked cured beef (SCCB) during chilled storage were investigated using principal components analysis (PCA) to determine the color fading causes. Samples were prepared and stored at 8°C for up to 35 days in a vacuum package to simulate a supermarket storage environment; related indicators were measured periodically every week. The results showed that the first PC explained 59.82% of the total variation, and the second explained 22.28%. PC1 was a concentrated reflection of color changes of SCCB during storage and PC2 was an environment factor causing the change of color. The change in apparent redness is mainly caused by redox reaction of the nitroso hemochromogen (NH) (eigenvectors of a*, C and NH in PC1 were all the maximum value of 0.28); a* was correlated with NH (0.96), free sulfhydryls (0.98), carbonyl derivatives (-0.95) formed during protein oxidation, and malondialdehyde (-0.98) and dienes (-0.92) formed by lipid oxidation. Color fading was significantly correlated with oxidizing and reducing power, existing forms of nitrogen and with the pH of the meat matrix. Changes in the internal environment of the sample initially influenced L* and b* values, and subsequently a*.

Studies on meat color, myoglobin content, enzyme activities, and genes associated with oxidative potential of pigs slaughtered at different growth stages

Objective

This experiment investigated meat color, myoglobin content, enzyme activities, and expression of genes associated with oxidative potential of pigs slaughtered at different growth stages.

Methods

Sixty 4-week-old Duroc×Landrace×Yorkshire pigs were assigned to 6 replicate groups, each containing 10 pigs. One pig from each group was sacrificed at day 35, 63, 98, and 161 to isolate longissimus dorsi and triceps muscles.

Results

Meat color scores were higher in pigs at 35 d than those at 63 d and 98 d (p<0.05), and those at 98 d were lower than those at 161 d (p<0.05). The total myoglobin was higher on 161 d compared with those at 63 d and 98 d (p<0.05). Increase in the proportions of metmyoglobin and deoxymyoglobin and a decrease in oxymyoglobin were observed between days 35 and 161 (p<0.05). Meat color scores were correlated to the proportion of oxymyoglobin (r = 0.59, p<0.01), and negatively correlated with deoxymyoglobin and metmyoglobin content (r = −0.48 and −0.62, p<0.05). Malate dehydrogenase (MDH) activity at 35 d and 98 d was higher than that at 161 d (p<0.05). The highest lactate dehydrogenase/MDH ratio was achieved at 161 d (p<0.05). Calcineurin mRNA expression decreased at 35 d compared to that at 63 d and 98 d (p<0.05). Myocyte enhancer factor 2 mRNA results indicated a higher expression at 161 d than that at 63 d and 98 d (p<0.05).

Conclusion

Porcine meat color, myoglobin content, enzyme activities, and genes associated with oxidative potential varied at different stages.

Current research in meat color

This review surveyed recent literature focused on factors that affect myoglobin chemistry, meat color, pigment redox stability, and methodology used to evaluate these properties. The appearance of meat and meat products is a complex topic involving animal genetics, ante- and postmortem conditions, fundamental muscle chemistry, and many factors related to meat processing, packaging, distribution, storage, display, and final preparation for consumption. These factors vary globally, but the variables that affect basic pigment chemistry are reasonably consistent between countries. Essential for maximizing meat color life is an understanding of the combined effects of two fundamental muscle traits, oxygen consumption and metmyoglobin reduction. In the antemortem sector of research, meat color is being related to genomic quantitative loci, numerous pre-harvest nutritional regimens, and housing and harvest environment. Our knowledge of postmortem chilling and pH effects, atmospheres used for packaging, antimicrobial interventions, and quality and safety of cooked color are now more clearly defined. The etiology of bone discoloration is now available. New color measurement methodology, especially digital imaging techniques, and improved modifications to existing methodology are now available. Nevertheless, unanswered questions regarding meat color remain. Meat scientists should continue to develop novel ways of improving muscle color and color stability while also focusing on the basic principles of myoglobin chemistry.

Fresh and cooked color of dark-cutting beef can be altered by post-rigor enhancement with lactic acid

Fresh and cooked color of dark-cutting (DC) beef strip loins (mean pH=6.56) enhanced with 0.25, 0.50, 0.75 or 1.00% lactic acid (LA) were compared to non-enhanced DC and normal pH (NpH; mean pH=5.43) strip loins. Even though NpH steaks received the most (P<0.05) desirable fresh color scores, color scores for steaks from DC sections enhanced with 0.25% LA approached those of NpH steaks after the first day of retail display. Discoloration scores were also similar (P>0.05) among NpH and 0.25% LA-enhanced DC steaks throughout the 5 d of display. Fresh steaks from NpH strip loins were redder, as evidenced by greater (P<0.05) a(∗) values and lower (P<0.05) hue angles, than DC steaks and DC steaks enhanced with LA, regardless of concentration. However, cooked color scores and proportions of denatured myoglobin were similar (P>0.05) between untreated NpH steaks and DC steaks enhanced with 0.25% LA. Results from this study indicate that enhancing DC beef with LA may lead to the brightening of the fresh color and prevention of the persistent red cooked color, approaching that of NpH beef.