Melvin C. Hunt

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.

Effects of calcium salts on beef longissimus quality.

The objective of this research was to evaluate the effects of injection marination with calcium salts on beef longissimus quality traits. Strip loins were injected (11% by weight) with distilled water or a 0.1, 0.2, or 0.3 M solution of calcium ascorbate, calcium chloride, or calcium lactate. Non-injected loins served as controls. Visual and instrumental color evaluations indicated that calcium ascorbate accelerated myoglobin oxidation, and increasing molar concentration of any calcium salt caused faster (P<0.05) discoloration. Aerobic microbial plate counts were lower (P<0.05) for treatments containing calcium lactate than those with calcium chloride or calcium ascorbate. Calcium ascorbate inhibited lipid oxidation whereas calcium lactate and calcium chloride appeared to be pro-oxidants of lipid oxidation. No differences for Warner-Bratzler shear force or sensory panel tenderness were found among the calcium salts; however, 0.3 M treatments had lower shear values and were judged more tender than 0.1 M treatments. Calcium ascorbate and calcium chloride treatments resulted in less (P<0.05) beef flavor and more (P<0.05) off-flavors than calcium lactate treatments. In addition, 0.1 M treatments had higher (P<0.05) beef flavor scores while 0.3 M treatments had higher (P<0.05) off-flavor scores. Considering the effects on color life, microbial inhibition, shear force, and sensory traits, we recommend injecting beef longissimus with a 0.1 M solution of calcium lactate to enhance both uncooked and cooked quality.

Effects of enhancing beef longissimus with phosphate plus salt, or calcium lactate plus non-phosphate water binders plus rosemary extract.

Beef strip loins (n=36) were enhanced with a sodium phosphate plus salt solution (PS); or with a calcium lactate solution (Ca) plus 1% or 2% beef broth (Br) plus natural flavoring (N) containing rosemary extract; or with 1% or 2% kappa carrageenan (Cr) plus N to determine effects of ingredients on color life, water-binding ability, and palatability traits. Enhancement with PS resulted in higher pH, higher pumped yields, greater water-binding ability, and higher tenderness and juiciness scores than enhancement with Ca (all p<0.05). Enhancement with Ca resulted in less color deterioration, less metmyoglobin discoloration, higher L (∗), a (∗), and b (∗) values, higher beef flavor intensity scores and lower off-flavor scores than enhancement with PS (all p<0.05). Warner-Bratzler shear values did not differ among treatments. Steaks enhanced with Br had less color deterioration, less metmyoglobin discoloration, and higher L (∗) values than those enhanced with Cr (all p<0.05). Pumped yields were not different between loins enhanced with Br or Cr. The N flavoring containing rosemary extract decreased (p<0.05) discoloration. Enhancing beef longissimus with PS increased water-binding capacity and sensory tenderness traits, but reduced color stability and increased off-flavors, whereas Ca preserved color stability and enhanced flavor at the expense of pumped yields. The use of Br or Cr had no influence on tenderness or palatability traits.

Effects of modified gas atmosphere packaging on pork loin colour, display life and drip loss.

Boneless loins from both sides of 20 pig carcasses were divided into five sections each and assigned equally to five packaging treatments: 100 % CO(2); 50 % CO(2)/50 % N(2); 25 % CO(2)/ 75 % N(2); 25 % CO(2)/65 % N(2)/10 % O(2) and vacuum. Loin sections were packaged in bags of low O(2) permeability, then stored in darkness at 1 °C for up to 22 days. Retail chops were cut from the sections and displayed in oxygen-permeable film under light at 3 °C for 3 additional days. The O(2) concentrations in packages with nominally anoxic atmospheres were 0.1-0.4 %. Sections stored in 25 % CO(2)/65 % N(2)/10 % O(2) had more surface greying and greening, stronger off-odour and psychrotropic counts after storage were more than one log(10) higher compared to sections from the other four treatments. Displayed chops from sections stored in 25 % CO(2)/65 % N(2)/10 % O(2) also had greying/greening at an outer layer of the chops. Off-odour of chops was most pronounced for treatments with 10 % O(2) and vacuum. Drip loss from loin sections was highest for those in 100 % CO(2) (4.2 %) and lowest for those in vacuum (3.2 %). In conclusion, storage in CO(2) or CO (2)N (2) atmospheres benefitted the overall shelf life of pork.

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) (1.49-10.89ng/g), MeIQx (2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline) (not detected-4.0ng/g), and DiMeIQx (2-amino-3,4,8-trimethyl-imidazo [4,5-f]quinoxaline) (not detected-3.57ng/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 (13.91ng/g) had higher levels of total HCAs than fried beef (8.92ng/g) and fried chicken (7.00ng/g). Among the samples, fried bacon contained the highest total HCA content (17.59ng/g).

Effects of Ascorbic Acid on Display Life of Ground Beef

Fresh ground beef containing 20 and 25% fat was either treated with 0.01, 0.05 or 0.10% crystalline ascorbic acid or remained as non-treated controls. Samples were displayed in polyvinyl chloride (PVC) film for up to 10 d (24 h/d) at 2 to 3°C under 1076 lux G. E. Natural light. Measures of display life included visual color scores, reflectance measurements, sensory panel scores, thiobarbituric acid (TBA) values and microbial standard plate counts (SPC). At days 1, 3 and 5 of display, average and worst point visual color scores were judged brighter for all ascorbic acid treatments compared to controls. Lower metmyoglobin percentages, higher %R630nm/%R580nm and higher CIE a* readings at days 3, 5 and 10 for the ascorbic acid-treated product supported visual color results. Higher fat (25%) and higher ascorbic acid levels (0.05 and 0.10%) gave brighter visual color responses at 5 d of display than the 20% fat product and that containing 0.01% ascorbic acid. More intense sensory panel beef flavor was associated with the 0.05 and 0.10% ascorbic acid treatments. More off-flavor was found in the higher fat product (25%). TBA values were not different for fat level comparisons, but were lower for the 0.05 and 0.10% ascorbic acid treatments. At day 5 of display, SPC were not affected by ascorbic acid treatment. The 25% fat product had lower SPC at day 5.

Effects of low-voltage electrical stimulation during exsanguination on meat quality and display colour stability.

Five steers from each of four slaughter groups were randomly assigned to a low-voltage electrical stimulation (LVES) treatment during exsanguination (within 5 min after stunning) and five served as controls (C). LVES consisted of 50V of 60 Hz alternating current (1 s on and 1 s off for 2 min). At 28 h, LVES longissimus (LM) was lighter in colour, softer, coarser in texture and tended to have lower marbling estimates than C. LVES LM steaks were lighter red at 0 and 1 days, but more discoloured at 5 days, of display than C steaks. Both the deep (DSM) and superficial (SSM) portions of LVES semimembranosus (SM) steaks were lighter red at 0 and 1 days of display than C steaks. Water-holding capacity for LVES LM and DSM steaks was lower than for C steaks. A trained sensory panel found LVES LM steaks to be less juicy and less tender than C steaks. Also, LVES LM steaks had greater cooking losses than C steaks in two of the four slaughter groups. We conclude that LVES during exsanguination, coupled with relatively slow initial chilling, may be detrimental to muscle quality.

Influence of carbon monoxide in package atmospheres containing oxygen on colour, reducing activity, and oxygen consumption of five bovine muscles

Steaks from five bovine muscles [psoas major (PM), longissimus lumborum (LL), deep semimembranosus (DSM), superficial semimembranosus (SSM), and semitendinosus (ST)] were packaged in atmospheres containing 20% or 80% oxygen, with and without 0.4% carbon monoxide. Steaks were evaluated on d 0, 4, and 7 of retail display for instrumental (CIE L(∗), a(∗), and b(∗)) and visual colour, total- and metmyoglobin-reducing activity, and oxygen consumption rate. Combining carbon monoxide with either oxygen level had no effect (P>0.05) on any measured attribute. Using higher oxygen levels increased colour stability and reduced variability (P<0.05) among muscles for all measured attributes. In general, colour stability and reducing activity for the muscles were LL>ST>SSM>PM>DSM. Including 0.4% carbon monoxide with 20% or 80% oxygen may not have impacted colour, due to preferential formation of oxymyoglobin, rather than carboxymyoglobin, at these oxygen levels.

Effects of potassium lactate, sodium chloride, sodium tripolyphosphate, and sodium acetate on colour, colour stability, and oxidative properties of injection-enhanced beef rib steaks.

This study determined the effects of potassium lactate (KL), sodium chloride, sodium tripolyphosphate, and sodium acetate on colour, colour stability, and oxidative properties of injection-enhanced beef rib steaks. Enhancement solutions (8.5% pump) contained combinations of KL (0% or 1.5%), sodium chloride (0.3% or 0.6%), sodium tripolyphosphate (0% or 0.3%), and sodium acetate (0% or 0.1%). Steaks were packaged in a high-oxygen modified atmosphere (80% O(2)/20% CO(2)). Steaks with KL or KL and sodium acetate were darker but more colour stable (P<0.05) than control steaks. Steaks had less glossy surfaces when they contained acetate (P<0.05) and KL (P<0.11). Increasing sodium chloride content resulted in darker, less colour-stable steaks (P<0.05). Removing phosphate had little impact on colour (P>0.05). Both KL and sodium acetate improved visual appearance of injection-enhanced beef rib steaks, whereas the greater salt level were detrimental.

Improving beef color stability: practical strategies and underlying mechanisms.

This paper overviewed the current literature on strategies to improve beef color and attempted to logically explain the fundamental mechanisms involved. Surface color and its stability are critical traits governing the marketability of fresh beef when sold, whereas internal cooked color is utilized as an indicator for doneness at the point of consumption. A multitude of exogenous and endogenous factors interact with the redox biochemistry of myoglobin in post-mortem skeletal muscles. The scientific principles of these biomolecular interactions are applied by the meat industry as interventions for pre-harvest (i.e. diet, animal management) and post-harvest (i.e. packaging, aging, antioxidants) strategies to improve color stability in fresh and cooked beef. Current research suggests that the effects of several of these strategies are specific to type of animal, feeding regimen, packaging system, and muscle source. Meat scientists should explore novel ways to manipulate these factors using a biosystems approach to achieve improved beef color stability, satisfy consumer perception, and increase market profitability.