Reflectance at 610 nanometers estimates oxymyoglobin content on the surface of ground beef

This research evaluated the utility of direct (K/S 610÷K/S 525) and indirect (100%-% deoxymyoglobin+% metmyoglobin) methods for estimation of oxymyoglobin (OMb) on the surface of ground beef. Direct estimation was highly correlated to visual color scores (r=-0.93), indirect determination of OMb (r=0.98), and % metmyoglobin (r=-0.98). Since indirect OMb was based partially on % deoxymyoglobin, which was poorly correlated to visual color scores, the accuracy of the subtraction method may be limited. Both direct and indirect methods produced similar variability when estimating OMb. All calculations for pigment forms produced outliers, which were adjusted to 0 and 100% to more precisely represent surface pigment concentrations. This work suggests that the K/S 610÷K/S 525 method is accurate and repeatable and can be used to quantify surface OMb concentration and discoloration of ground beef.     

Utilization of image processing to quantitate surface metmyoglobin on fresh beef

Ground beef patties were manufactured with various combinations of ascorbic acid and mechanically recovered neck bone lean (MRNL) to study the use of image processing in predicting percentage surface metmyoglobin (metMb) on fresh beef. Ascorbic acid and MRNL cause various color phenomena that resulted in a wide range of variation in surface color. Patties were also stored over six days of retail display to cause further color changes. Surface color was assessed by several different accepted methods. A prediction equation for percentage surface metMb included mean values for hue, saturation and intensity. Root mean square error, R-square and Mallow's Cp statistic were used as selection criteria for choosing the best predictive model. Image processing hue, saturation and intensity accounted for 93% of the variation in percentage surface metMb. Since hue, saturation and intensity each contribute to overall color profile it is logical that these parameters are good predictors. These data indicate that image processing is capable of objectively measuring percentage surface metMb.     

Factors affecting the rate of metmyoglobin accumulation in pre-packaged beef

Factors affecting the rate of discoloration of pre-packaged beef have been compared quantitatively in a number of experimental animals. Inter-muscular variability is the most important single factor and ranges from the stable M. longissimus dorsi to the unstable M. psoas major, the degree of discoloration of the latter muscle being almost eight times greater after 96 h storage at 0°C. Among other intrinsic factors studied, age post mortem has a slight accelerating effect while pH, within the narrow range exhibited by experimental animals, has no effect. Inter-animal variability also has an effect, but only a slight one.

Of the extrinsic factors studied, temperature is most important from a practical standpoint, the degree of discoloration after 96 h storage at 10°C ranging from two to five times that at 0°C, depending on the muscle. Light produces only a minor accelerating effect but UV produces serious discoloration in all muscles within hours, even at 0°C. Slight differences exist between packaging films but these are not commercially significant.     

The effects of freeze-thaw and sonication on mitochondrial oxygen consumption, electron transport chain-linked metmyoglobin reduction, lipid oxidation, and oxymyoglobin oxidation

Mitochondria potentially influence Mb redox stability in meat by (1) decreasing partial oxygen pressure via oxygen consumption, (2) mitochondrial electron transport chain (ETC)-linked reduction of MetMb, and/or (3) oxidation of mitochondrial membrane lipid. The objective of this study was to investigate the effect of freeze-thaw and sonication treatments on mitochondrial oxygen consumption, ETC-dependent MetMb reducing activity, lipid oxidation, and Mb redox stability. Mitochondria were frozen and thawed (-18°C for 2h and 4°C for 0.5h) for 3 cycles, or sonicated for 30s with a sonic dismembrator. State III oxygen consumption rate (OCR) was decreased by both treatments at pH 7.2, and by sonication only at pH 5.6 (P<0.05). There was no effect on state IV OCR (P>0.05). Respiratory control ratio (RCR) was decreased by freeze-thaw and sonication at pH 7.2 and 5.6 (P<0.05). Sonication increased mitochondrial lipid oxidation and MetMb formation (P<0.05); a similar effect was observed in sonicated samples in the presence of ascorbic acid and ferric chloride (P<0.05). Sonication also decreased mitochondrial ETC-dependent MetMb reduction (P<0.05). These results suggested that sonication treatment had the potential to affect Mb stability via mitochondrial lipid oxidation and/or ETC-mediated MetMb reduction, but the effect on myoglobin stability by freeze-thaw treatment was minimal.     

Inhibition of metmyoglobin formation in fresh beef by pressure treatment

Application of pressures of 80-100 MPa for 20 min improved the colour stability, as measured by rate of metmyoglobin formation, of longissimus dorsi and psoas major beef muscles exposed to air 2 days post-slaughter. However, pressure treatment of these muscles at 7-20 days post-slaughter did not improve their colour stability. It is suggested that pressure inhibits, at least partially, the mechanism(s) responsible for the low colour stability of very fresh beef.     

Relative role of catalysts and reductants in the formation of metmyoglobin in aerobically stored beef

The formation of metmyoglobin (metMb) in sterile minced and intact slices of beef has been determined during storage at 1°C. The oxidation of oxymyoglobin in minced beef is first order, the rate constants for different muscles, although being pH dependent, are similar for all the muscles studied. The rate is about four or five times faster than that reported for oxymyoglobin in solution, indicating that catalysis occurs. In intact slices the reaction profile is more complex as a pseudoequilibrium level of metmyoglobin forms after a few days at 1°C, the concentration of metMb remaining constant for several days and then being followed by further rapid oxidation to 100% metMb. Due to variations in an aerobic reducing system present in intact beef the duration of the pseudoequilibrium varies markedly from muscle to muscle; this reducing system is destroyed by mincing. The rate of metMb formation in intact muscles varies with sample shape, thin slices being more colour stable ones. Reasons for this dependence on sample shape are discussed.     

Biochemical factors influencing metmyoglobin formation on beef from muscles of differing colour stability

Biochemical parameters, such as oxygen consumption rate by muscle post mortem (OCR), depth of oxygen penetration into meat, rates of myoglobin oxygenation and deoxygenation and myoglobin content and succinic dehydrogenase activity, were determined for muscles of differing colour stability. Metmyoglobin reduction, in anoxia following oxidation with ferricyanide (MRA) and aerobically following oxidation with low pO(2) (ARA), were also determined. M. psoas major (poor colour stability) has higher enzymic activity than M. longissimus dorsi (good colour stability). This difference, together with the low myoglobin content in M. psoas major, results in relatively high OCR with consequent low oxygen penetration and rapid conversion of oxymyoglobin to myoglobin in M. psoas major, disposing it to rapid formation of metmyoglobin. Metmyoglobin reduction occurs both under anaerobic and aerobic conditions but no significant correlation is found between actual metmyoglobin reduction and rate of discoloration of different muscles. The most significant factor affecting colour stability of beef muscles appears to be their enzymic activity which determines the rate of myoglobin oxidation.     

Lipid oxidation induced by oxymyoglobin and metmyoglobin with involvement of H(2)O(2) and superoxide anion

The role of oxymyoglobin oxidation in lipid oxidation was studied in a myoglobin-liposome system. The pro-oxidant effect of oxymyoglobin towards lipid oxidation was concentration-dependent. At equimolar concentrations, oxymyoglobin showed higher pro-oxidative activity towards lipid than metmyoglobin (p < 0.05). These results suggested that the process of oxymyoglobin oxidation is involved in catalyzing lipid oxidation. The addition of catalase into the oxymyoglobin-liposome system resulted in significantly decreased oxidation of oxymyoglobin and lipid (p < 0.05) suggesting a role for H(2)O(2) in the interaction between oxymyoglobin and lipid. The addition of Superoxide dismutase was without effect (p > 0.05) suggesting that Superoxide anion was not directly involved in mediating oxidation of oxymyoglobin and lipid. Albumin was added as a control for a non-specific protein antioxidant; it did not affect oxymyoglobin or lipid oxidation (p > 0.05). Our in vitro results support the hypothesis that the actual process of oxymyoglobin oxidation is a catalyst of lipid oxidation with H(2)O(2) a major factor.     

The rate of metmyoglobin formation in beef, pork, and turkey meat as influenced by pH, sodium chloride, and sodium tripolyphosphate

This study investigated the effects of pH (5·5 to 7·0), sodium chloride concentration (0·0-3·0%), and sodium tripolyphosphate concentration (0·0 and 0·5%) on the rate of metmyoglobin formation in ground beef, pork and turkey meat during refrigerated storage. Increasing the sodium chloride concentration produced a progressive increase in the rate of metmyoglobin formation in ground beef. Increasing the pH between pH 5·5 and 6·5 had no effect on the rate of metmyoglobin formation with ground beef and turkey meat, but produced a marked decrease between pH 6·5 and 7·0. In contrast pH had no consistent effect on the rate of metmyoglobin formation of ground pork and the rate of formation remained low at all pH levels. When ground beef contained 0·5% sodium tripolyphosphate, the effect of pH was reversed and the rate of metmyoglobin formation was lowest at pH 5·5, increased as the pH increased to 6·5 and then plateaued.     

A survey of pH values at the surface of beef and lamb carcasses,stored in a chiller

The surface pH values of lamb and beef carcasses stored at 5 ºC have been measured over a 5-day period. In both types of animal, muscle surfaces were at or near their minimum pH at 3 days, when the overall mean was pH 6.4. In the subsequent 2 days some sites showed no change in pH, while at others a small drop or a rise occurred. Rises in pH tended to be more common and greater on the beef. In lamb, intact muscle surfaces varied only from pH 6.3 to 6.6 at 3 days, while beef muscles varied widely, from pH 5.8 to 7.1. Muscle surfaces cut during dressing fell much more rapidly in pH, particularly in beef. Fatty sites fell from near pH 8.0 to near pH 7.0. The pH of beef surfaces chilled to -3 ºC fell more rapidly to lower final values than those at 5 ºC. At 5 ºC there was little multiplication of bacteria on fat surfaces, whereas on muscle they grew moderately, irrespective of pH.     

Prediction of the soluble myoglobin content of cooked burgers

The time-temperature profiles for cooking in-house made beef and lamb burgers were determined using a thermocouple placed in the centre of the burger. From these data the soluble myoglobin remaining in the burger was predicted using kinetic data from previously reported model experiments. First order kinetics were assumed for the denaturation of the myoglobin. A good correlation between observed and predicted data was observed. Thus the "degree of doneness"of different meats can be predicted when cooked under specified conditions.     

Quantitative determination of myoglobin and haemoglobin in beef by high-performance liquid chromatography

Three different HPLC columns were tested for their suitability for the analysis of myoglobin and haemoglobin in beef. Complete separation of the two proteins was obtained with an anion exchange column and a column based on hydrophobic interaction. With the latter column a recovery close to 100% was obtained for both proteins when they were added to meat extracts. For both proteins, the standard error of the mean for repeated analyses of ground beef was less than 2% of the detected amount. The method is considered as suited for quantitative routine analysis of myoglobin and haemoglobin in beef and beef products.     

Moisture content relative humidity equilibrium, at different temperatures, of some oilseeds of economic importance

Equilibrium relative humidity relationships at temperatures from 10° to 40°C are presented in graph form for soya beans, sunflower seed, linseed, groundnuts and copra.     

Pre-slaughter injection of sodium ascorbate as a method of inhibiting metmyoglobin formation in fresh beef

Colour deterioration, measured by metmyoglobin accumulation, in four muscles, from 10 beef animals, intravenously injected pre-slaughter with sodium ascorbate, is compared with similar muscles from 10 control animals, at 0 °C and 5 °C. Meat from sodium ascorbate treated animals has significantly better colour stability, particularly M. psoas major and M. gluteus medius at the higher storage temperature.     

Dietary tea reduces the iron content of beef

We hypothesized that the lightness of Japanese beef was related to the concentration of heme iron. In Experiment 1, six Japanese Black heifers were allotted randomly to one of three treatment groups: a basal concentrate ration (40% flaked corn) or the same diet and either 2 kg/d wheat bran or 0.5 kg/d green tea. After feeding the diets for 174 d, the cattle were slaughtered and the M. longissimus thoracis, M. semimembranosus, and M. gluteus medius were sampled for meat color, iron, and lipid content. The iron content of the M. semimembranosus from the tea-fed cattle was lower than in M. semimembranosus from the control cattle, and a* (redness) and √(a^*2+b^*2) (saturation) values were lower in M. semimembranosus from bran- and tea-fed cattle than in control cattle. Treatment main effects (across muscles) indicated that inclusion of tea in the diet increased intramuscular lipid and reduced the muscle iron content. There was a significant negative correlation (r²=0.79) between muscle iron content and L^* value (lightness). For Experiment 2, the effect of beef breed type on meat color and iron content of M. longissimus thoracis was investigated using stored meat samples from six breeds from a previous fattening experiment done under a high nutritional plane. Muscle iron content was significantly lower in Japanese Black cattle than in Japanese Black × Holstein or Japanese Black × Japanese Black/Holstein. There was no relationship between muscle iron content and intramuscular lipid content (r²=0.001). In Experiment 3, samples of M. longissimus dorsi were obtained from 17 Wagyu crossbred and 3 Angus crossbred cattle fed a corn concentrate diet in the USA for 148 d. Iron content of the M. longissimus thoracis from Japanese Black and Japanese Brown × Holstein cattle fattened in Japan was significantly less than the iron content of M. longissimus dorsi from cattle raised in the USA. Overall, the data indicate that it is possible to lower muscle iron, and lighten muscle color, by feeding green tea to Japanese cattle; also, there may be a genetic basis for the lower iron, and lighter color, of beef produced in Japan.     

Antioxidant enzyme activities in beef in relation to oxidation of lipid and myoglobin

Lipid- and oxy-free radical generation has been implicated in oxidative processes which occur during meat maturation but the importance of the antioxidant enzyme (AOE) activity in these processes is not known. It was shown that metmyoglobin (MetMb) % and lipofuscin content were higher in colour-unstable muscles such as psoas major (PM) and diaphragma (D) compared to longissimus lumborum (LL) and tensor fasciae latae (TFL). Although Superoxide dismutase (SOD) activity is higher post mortem in PM and D muscles than in LL and TFL muscles, catalase and glutathione peroxidase (GPx) activities were higher only in D muscle. The higher AOE activity in colour-unstable muscles such as PM and D was not sufficient to prevent increased formation of MetMb and lipofuscin in these muscles compared to LL and TFL muscles.