Spectro 1-A Potential Spectrophotometer for Measuring Color and Myoglobin Forms in Beef.

The objective of this study was to compare the Color Muse Spectro 1 sensor to the HunterLab MiniScan XE Plus spectrophotometer for evaluating beef color. Color coordinates (lightness (L*), redness (a*), yellowness (b*), chroma (C*), and hue (h*)), myoglobin redox forms (metmyoglobin (MMb), deoxymyoglobin (DMb), and oxymyoglobin (OMb)), and metmyoglobin reducing ability (MRA) were measured on beef steaks over a 5-days storage period. The results indicated that L*, b*, C*, MMb%, OMb%, and MRA% values obtained with Spectro 1 were comparable to those of MiniScan. However, Spectro 1 values for a* were overestimated compared to MiniScan (p < 0.05), whereas those for h* and DMb% were underestimated (p < 0.05). Regardless, Spectro 1 had the capability to detect changes in color coordinates, myoglobin forms, and MRA throughout the storage period. Bland−Altman plots demonstrated that L*, b*, and C* are interchangeable between the two instruments, but it was not the case for a*, h*, myoglobin forms, and MRA. Color coordinates measured by Spectro 1 exhibited excellent stability over time, evidenced by the low total color difference (ΔE*ab) values. Collectively, these findings indicate that Spectro 1 is a potential alternative spectrophotometer for studying meat color and myoglobin redox forms.

Injection of iodoacetic acid into pre-rigor bovine muscle simulates dark cutting conditions.

The purpose of this study was to develop an in situ model for dark cutting beef. Iodoacetic acid (IAA) was injected at different concentrations (0, 0.625, 1.25, 2.5, 3.75, 5, or 10 µmol/g of muscle) into pre-rigor bovine longissimus thoracis et lumborum (LTL) muscle samples, and pH and color were evaluated over a 48 h period. Injection of IAA blunted muscle pH decline and lowered lightness (L*), redness (a*), and yellowness (b*) values (P ≤ 0.05) in a concentration dependent fashion. In a follow-up study, LTL muscle samples were injected with 5 µmol IAA/g of muscle to test whether IAA maintains its effect over a 336 h post-mortem storage period. In addition to inhibiting pH decline and decreasing color values, IAA increased LTL muscle water holding capacity (WHC) and firmness (P ≤ 0.05) throughout the 336 h post-mortem storage period. Collectively, these data suggest that pre-rigor injection of IAA generates beef with dark cutting-like characteristics.

Effect of oxygen concentration in modified atmosphere packaging on color changes of the M. longissimus thoraces et lumborum from dark cutting beef carcasses.

The objective of this study was to investigate the effect of modified atmosphere packaging (MAP) with different oxygen concentrations on color changes of dark-cutting beef steaks from M. longissimus thoraces et lumborum. Four normal-pH (mean pH = 5.52) and four dark-cutting beef carcasses (mean pH = 6.36) were obtained from a commercial abattoir at 48 h post-mortem. The gas compositions in MAP were as follows: (i) 20% O2/20% CO2/60% N2, (ii) 40% O2/20% CO2/40% N2, (iii) 60% O2/20% CO2/20% N2 and (iv) 80% O2/20% CO2. Steaks were stored in the dark at 2 °C for 14 days. Surface color of dark-cutting beef steaks was improved (P < .05) by 60%O2-MAP and 80%O2-MAP after 4 days storage, to a level similar to the initial normal-pH steaks. Steaks in 60%O2-MAP and 80%O2-MAP had lower metmyoglobin reducing activity and higher TBARS values (P < .05), but deeper oxygen penetration depth (P < .05) that may have masked discoloration resulting from metmyoglobin formation under the surface. While both 60%O2-MAP and 80%O2-MAP improved the appearance of dark-cutting beef, 60%O2-MAP may be preferred owing to the lower level of lipid oxidation.

Myoglobin oxidation in a model system as affected by nonheme iron and iron chelating agents.

A model system was used to study the effect of nonheme iron on myoglobin oxidation at pH 5.6 and pH 7.2 at 23 degrees C. The addition of ferrous iron significantly (p < 0.05) increased the rate of myoglobin oxidation in the absence of lipid, demonstrating that iron promoted myoglobin oxidation independent of the effect of lipid oxidation. The addition of the type II, iron chelating antioxidants sodium tripolyphosphate (at pH 7.2) or milk mineral (at pH 5.6) negated the effect of added iron, slowing oxidation of myoglobin. A clear concentration dependence was seen for iron-stimulated myoglobin oxidation, based on both spectral and visual evidence. Further investigation is needed to determine the possible role for nonheme ferrous iron on myoglobin oxidation in vivo or in meat.

Comparison of antioxidant effects of milk mineral, butylated hydroxytoluene and sodium tripolyphosphate in raw and cooked ground pork.

The antioxidant effects of 0.5-2.0% milk mineral (MM) was tested in raw and cooked ground pork stored at 2 °C or -20 °C, compared to butylated hydroxytoluene (BHT) and sodium tripolyphosphate (STP). TBA numbers were low and not different between raw meat treatments. TBA numbers were lower (P<0.01) for cooked treatments with MM or STP compared to controls or treatments with BHT. Experiments were also done to determine acceptability of pork samples with various TBA values, and to determine effect of holding time before serving on TBA values. Cooked pork patties held at 71 °C for 90 or 120 min had higher (P<0.05) TBA values than patties held for 0-60 min. Thus patties could be warmed for 60 min after cooking without significantly increasing TBA number. For paired-preference sensory testing, patties were cooked and stored at 2 °C for 0, 1, 2 and 3 days to obtain TBA numbers of 0.4, 1.5, 3.4 and 3.9 respectively. Panelists preferred (P<0.001) patties with TBA number <0.5, compared to patties with TBA numbers >1.4.