PIGMENTS MODIFICATIONS DURING FREEZING and FROZEN STORAGE of PACKAGED BEEF

Muscle pigment modifications during freezing and frozen storage of beef wrapped in high (polyethylene) and low (EVA/SARAN/EVA) gaseous permeability films were analyzed. Myo (Mb), oxy (MbO²) and metmyoglobin (MetMb) concentrations were determined using reflectance spectrophotometry. Results indicated that in polyethylene wrapped samples myoglobin oxygenation took place during freezing and the only reaction observed throughout frozen storage was MetMb production from MbO₂. Autoxidation was interpreted as a first order kinetic reaction. Storage temperature effect on kinetic and equilibrium constants was analyzed; reaction enthalpy and activation energy were calculated. MbO₂ and MetMb production during beef oxygenation was represented as a consecutive first order reaction system determining previous vacuum storage time and temperature influence on oxygenation capacity. Vacuum packaging of frozen beef increased color stability maintaining MetMb concentration levels lower than those corresponding to just frozen samples wrapped in polyethylene.     

Isolation,characterisation and stability of myoglobin from Eastern little tuna (Euthynnus affinis) dark muscle

This study aimed to purify and characterise the myoglobin from the dark muscle of Eastern little tuna (Euthynnus affinis). Myoglobin purified by ammonium sulphate precipitation (65–100% saturation), followed by Sephadex G-75 chromatography had a molecular weight of 15,680 Da. The isoelectric point (pI) of both oxymyoglobin (OxyMb) and metmyoglobin (MetMb) was estimated to be 5.25, as determined by zeta potential analysis. Transition temperatures were 61 and 60 °C, for OxyMb and MetMb, respectively. The colour values (L∗, a∗ and b∗) and absorption spectra of the myoglobin solutions differed significantly, depending upon the form of myoglobin. OxyMb and MetMb had the Soret bands at 413 and 407 nm, respectively. The pH and thermal stability of myoglobin were tested under a pH range of 3–11 and a temperature range of 4–70 °C, respectively. Loss of haem–globin complex and autoxidation were dominant at pH 3, as evidenced by the disappearance of the Soret band and the formation of MetMb. Heating at temperature above 60 °C had a great impact on myoglobin denaturation. With increasing temperature and incubation time, OxyMb was susceptible to oxidation and conformational changes, whilst MetMb tended to be more stable. Thus, the form of myoglobin governed its properties and stability.     

Modelling the effect of different sterilisation treatments on antioxidant activity and colour of carrot slices during storage

The effect of F₀ treatment time (min) and storage on the antioxidant activity and Hunter colour parameters (L*, a*, b*) of carrot slices was investigated. Carrot slices were sterilised for 0 (control), 3, 15 and 50 min and subsequently stored for 0, 3 and 6 months. Significant differences were observed in colour values of carrot slices with no significant difference beyond F₀ treatment of 3 min. Regression modelling was used to investigate the main effects of treatment time and storage. Treatment time and storage period was found to be significant. Predicted models were found to be significant (p < 0.05) with low standard error and high coefficients of determination (R²). This study proposes the predicted models for quality parameters of sterilised carrot slices.     

The relevance of different near infrared technologies and sample treatments for predicting meat quality traits in commercial beef cuts

Visible and near infrared reflectance (Vis-NIR, 350 to 1800 nm), and near infrared transmittance (NIT, 850 to 1050 nm) spectroscopy were used to predict beef quality traits of intact and ground meat samples. Calibration equations were developed from reference data (n = 312) of pH, color traits (L*, a*, and b*), ageing loss (%), cooking loss (%), and Warner–Bratzler shear force (WBSF, N) using partial least squares regressions. Predictive ability of the models was assessed by coefficient of determination of cross-validation (R²_CV) and root mean square error of cross-validation. Quality traits were better predicted on intact than on ground samples, and the best results were obtained using Vis-NIR spectroscopy. Predictions were good (R²_CV = 0.62 to 0.73) for pH, L*, and a*, hardly sufficient (R²_CV = 0.34 to 0.60) for b*, cooking loss, and WBSF, and unsatisfactory for ageing loss (R²_CV = 0.15). Vis-NIR spectroscopy might be used to predict some physical beef quality traits on intact meat samples.     

High pressure effect on the color of minced cured restructured ham at different levels of drying, pH, and NaCl

Color changes of minced cured restructured ham was studied considering the effects of high pressure (HP) treatment (600 MPa, 13 °C, 5 min), raw meat pH₂₄ (low, normal, high), salt content (15, 30 g/kg), and drying (20%, 50% weight loss). Raw hams were selected based on pH₂₄ in Semimembranosus, mixed with additives, frozen, sliced, and dried using the Quick-Dry-Slice® process. Meat color (CIE 1976 L*a*b*) and reflectance spectra were measured before and after HP treatment. HP significantly increased L*, decreased a*, and decreased b* for restructured ham dried to 20% weight loss, regardless of salt content and pH₂₄. L* and a* were best preserved in high pH/high salt restructured ham. HP had no effect on the color of restructured ham dried to 50% weight loss. HP had no effect on the shape of reflectance curves, indicating that the pigment responsible for minced cured restructured ham color did not change due to HP.     

Association mapping of quantitative trait loci for carcass and meat quality traits at the central part of chromosome 2 in Italian Large White pigs

Association mapping of the central part of porcine chromosome 2 harboring QTLs for carcass and meat quality traits was performed with 17 gene-tagged SNPs located between 44.0 and 77.5 Mb on a physical map (Sscrofa10.2) in Italian Large White pigs. For the analyzed animals records of estimated breeding values for average daily gain, back fat thickness, lean cuts, ham weight, feed conversion ratio, pH₁, pH_u, CIE L*, CIE a*, CIE b* and drip loss were available. A significant QTL for fat deposition (adjusted P = 0.0081) and pH₁ (adjusted P = 0.0972) to MYOD1 at position 44.4 Mb and a QTL for growth and meatiness (adjusted P = 0.0238–0.0601) to UBL5 at position 68.9 Mb were mapped. These results from association mapping are much more accurate than those from linkage mapping and facilitate further search for position candidate genes and causative mutations needed for application of markers through marker assisted selection.     

Effects of malate,lactate, and pyruvate on myoglobin redox stability in homogenates of three bovine muscles

We investigated the effects of glycolytic and tricarboxylic acid cycle metabolic intermediates on myoglobin redox forms and meat colour stability. Eighteen combinations of malate (M), lactate (L), and pyruvate (P) were added to beef Longissimus lumborum, Psoas major, and Semitendinosus muscle homogenates to study their effect on metmyoglobin formation during incubation at 25 °C. Changes in surface colour at 0, 2, 4, 8, and 12 h were evaluated by using reflecto-spectrophotometry [both L*, a*, and b* and wavelengths specific for metmyoglobin (MMb)]. Addition of M, L, and P alone or in combinations stabilized (P < 0.05) L*, a*, and b* values and myoglobin redox forms in muscle homogenates; however, there was a trend for P to be least effective. At the 2% concentrations for the individual metabolites, L was most effective at retarding MMb formation in the Semitendinosus (M was intermediate and P was least effective), and M was most effective in the Psoas major and L. lumborum muscles (L was intermediate and P was least effective). Metmyoglobin was reduced most effectively with a combination of metabolites (M + L > M + P > L + P). Enhancing meat with these metabolites can effectively extend colour life of post-rigor meat, apparently by providing more reducing conditions for myoglobin, thus increasing myoglobin redox form stability.     

Detection of 4-hydroxy-2-nonenal adducts of turkey and chicken myoglobins using mass spectrometry

4-Hydroxy-2-nonenal (HNE), an unsaturated aldehyde generated by peroxidation of polyunsaturated fatty acids, is highly reactive and destabilizes myoglobin (Mb) redox state, affecting meat colour. Our objective was to characterise the adduction of HNE to turkey and chicken Mbs using tandem mass spectrometry (MS/MS). Turkey and chicken oxymyoglobins (OxyMbs) were incubated with HNE at 25 °C, pH 5.8 or 7.4. MetMb formation was greater in the presence of HNE than controls (p < 0.05). Electrospray ionisation-Q-TOF mass spectrometry of HNE-reacted Mbs revealed covalent adduction of HNE to both turkey and chicken Mbs via Michael addition. LC–ESI-MS/MS of chicken Mb reacted with HNE identified covalent adduction of histidine (His) residues 64 and 93 at pH 7.4, whereas at pH 5.8 only His 64 was adducted. These results suggest that HNE accelerates chicken OxyMb oxidation in vitro by covalent modification at histidine residues.     

Influence of sonication on Warner-Bratzler shear force,colour and myoglobin of beef (<Emphasis Type="Italic">m. semimembranosus</Emphasis>)

Research in the past few decades has shown the potential benefits of using ultrasound treatment as a technique to enhance tenderness and sensory properties of meat and its sub-products. The objective of current study was to assess whether the low-frequency, low-intensity ultrasound treatment at 24 h postmortem affects the pH, Warner-Bratzler shear force (WBSF), colour (CIE L^*a^*b^*c^*H°), and relative proportions of myoglobin (Mb) redox forms and total Mb concentration during 96 h of beef (musculus semimembranosus) storage. Muscles were obtained from young bulls (n = 15) of Lowland Black and White breed slaughtered at a live weight of 475 (SD 16.1) kg. Ultrasound treatment did not have a statistically significant (p < 0.05) effect on the pH of meat directly after sonication (24 h postmortem), or at 72 and 96 h postmortem. Sonicated meat sample (S) was characterized by higher, but not statistically significant (p < 0.05), L* coordinate values 24, 48 and 72 h postmortem. During the whole storage period, colour coordinates a*b*c* and H° were not significantly (p < 0.05) affected by sonication. Ultrasound treatment accelerated the total colour change ΔE, limited the formation of MbO₂ and slowed down the formation of MetMb. Measurements carried out 48 and 72 h after slaughter revealed that the ultrasound treatment significantly (p < 0.05) reduced the WBSF. This study demonstrates the potential of low-frequency, low-intensity ultrasound treatment at 24 h postmortem for beef tenderization without detrimental effects on its CIE colour parameters and relative proportions of Mb redox forms.     

Potassium Sorbate Effect on Pigment Concentration of Refrigerated Beef

The influence of potassium sorbate (SorK) on the relative concentrations of myo (Mb), oxi (MbO₂,) and metamyoglobin (MetMb) of raw beef samples wrapped in plastic films of differcnt gaseous permeability was determined at 0°C and 4°C. Diffuse rcflectance spectrophotometry was applied to determine muscle pigmcnts concentrations. Kinetics constants for Mbo₂, and MetMb production during acrobic storage (polyethylene film) were statistically analyzed and compared with constants corresponding to sterilc and untreated meat. Influence of vacuum storage time, temperature and SorK levels on oxygenation capacity of samples packaged in EVA-SARAN-EVA was studied considering losses of cnzymatic activity and microbial growth. Shelf life of vacuum-packaged beef trcatcd with SorK solutions was significantly increased without affecting oxygenation capacity; use of SorK in meat wrapped in high permeability films was not convcnient since MetMb accumulation was faster than in untreated muscle.     

Feasibility of Vis/NIR spectroscopy for detection of flaws in hazelnut kernels

The feasibility of Vis/NIR spectroscopy for detection of flaws in hazelnut kernels (Corylus avellana L. cv. Tonda Gentile Romana) is demonstrated. Feature datasets comprising raw absorbance values, raw absorbance ratios (Abs[λ₁]:Abs[λ₂]) and differences (Abs[λ₁] − Abs[λ₂]) for all possible pairs of wavelengths from 306.5 nm to 1710.9 nm were extracted from the spectra for use in an iterative LDA routine. For each dataset, several spectral pretreatments were tested. Each group of features selected was subjected to Partial Least Squares Discriminant Analysis (PLS-DA), Receiver Operating Characteristics (ROCs) analysis, and evaluation of performance through the Area Under ROC Curve. The best result (5.4% false negative, 5.0% false positive, 5.2% total error) was obtained using a Savitzky–Golay second derivative on the dataset of raw absorbance differences. The optimal features were Abs[564 nm]–Abs[600 nm], Abs[1223 nm]–Abs[1338 nm] and Abs[1283 nm]–Abs[1338 nm]. The results indicate the feasibility of a rapid, online detection system.     

Mass spectrometric characterization and thermostability of turkey myoglobin

Pink color defect (PCD) is a major quality problem in the turkey industry leading to pink appearance of pre-cooked, uncured turkey. The present study determined the molecular mass of turkey myoglobin (Mb) using mass spectrometry and characterized the thermostability of turkey Mb, in comparison with beef Mb, to elucidate the molecular basis of PCD. Purified turkey and beef myoglobins were analyzed using Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry. The thermostability of turkey and beef oxymyoglobins was examined at pH and Mb concentrations (pH 6.2 and 0.04 mmol/L for turkey; pH 5.6 and 0.15 mmol/L for beef) reflecting inherent conditions in these meats. Turkey and beef oxymyoglobins were incubated at 71, 75, and 80 °C and percentage myoglobin denaturation (PMD) was determined. Molecular mass of turkey Mb (17,295 Da) was 346 Da greater than beef Mb (16,949 Da) and was approximately 300-350 Da greater than those of other red meat myoglobins, suggesting its unique primary structure. PMD was lower (P < 0.05) in turkey Mb than in beef Mb during incubation at 71, 75 and 80 °C, indicating that in-situ turkey Mb is less susceptible to heat-induced denaturation than beef Mb at typical meat cooking conditions. The observed greater thermostability of turkey Mb compared to beef Mb could be, partially, due to inherent greater pH in turkey than in beef. Possible unique primary structure of turkey Mb could have contributed to its greater thermostability, which is one of the reasons for PCD.     

Oxidative modification of amino acids in porcine myofibrillar protein isolates exposed to three oxidizing systems

Susceptibility of amino acids in myofibrillar protein isolate (MPI) exposed to three oxidizing matrixes commonly encountered in muscle foods was compared. MPI suspensions (20 mg protein/mL) in 15 mM piperazine-N,N bis(2-ethane sulphonic acid) buffer (pH 6.0) were oxidized with an iron-catalyzed oxidizing system (IOS, 0.01 mM FeCl₃, 0.1 mM ascorbic acid, 0.0–10.0 mM H₂O₂), a lipid-oxidizing system (LOS, 0.0–10.0 mM linoleic acid, 3750 units of lipoxidase/mL), or a metmyoglobin (MetMb) oxidizing system (MOS, 0.0–0.5 mM H₂O₂/MetMb) for 24 h at 4 °C. Changes were quantitatively analyzed by determining amino acids on a reverse-phase liquid chromatographic (LC) system. In IOS, the amount of cysteine, methionine and tyrosine decreased (P < 0.05) with increasing [H₂O₂]. In LOS, only cysteine and methionine were lowered at increasing linoleic acid concentrations. In MOS, the quantity of alanine, cysteine, glycine, histidine, leucine and lysine, as well as the total amount of amino acids were significantly reduced at high concentrations of MetMb/H₂O₂. The results suggest that under typical meat processing conditions, iron- and metmyoglobin-catalyzed reactions play a major role in the oxidation of amino acids in muscle proteins.     

Colour values of cooked top-round beef juices as affected by endpoint temperatures,frozen storage of cooked samples and storage of expressed juices

Juices from beef semimembranosus/adductor tissue, cooked to endpoint temperatures (EPTs) of 76, 78, 80, 82 and 84°C in a model heat-treating system, were evaluated for changes in CIELAB L*a*b*, chroma (C) and hue angle (H) values before and after storage of the cooked meat at -20°C for 3 weeks and after storage of the expressed juices under N₂ at 3°C for 72 h. Increases in EPTs altered all colour values of the juices. Lightness (L*) increased while yellowness (b*) decreased; redness (a*) and C decreased progressively while H increased toward the vertical axis. Storage of the expressed juices at 3°C under N₂ did not inhibit changes in a*, b*, C and H values. Regression coefficients of changes in relation to EPTs and time of storage of the expressed juices under N₂ were established. Storage of the cooked meats for 3 weeks at -20°C did not change any of the colour values of the juices. These data indicate that evaluations of cooked beef for doneness by colour of expressed juices must be performed immediately after expression of the juices before oxidation of the myoglobin pigments occurs. Storage of cooked meat at -20°C does not alter the colour of the juices, therefore, valid assays for doneness of meat in relation to juice colour can be made after frozen storage. © 1997 This article is a US Government work and, as such, is in the public domain in the United States of America     

The effect of pH on shelf-life of pork during aging and simulated retail display

The pork industry uses pH to differentiate product of varying quality; thus, the effect of pH on shelf-life is important as time during transport is extended. The objective was to develop regression equations to predict shelf-life over a range of ultimate pH (5.42–6.26). Shelf-life was evaluated after vacuum aging pork loin sections 0, 7, 14, 21, or 28 d and during 3 d of simulated retail display (4.5 °C) for pork loin chops. Correlation coefficients indicated a strong relationship between pH and quality measurements. Regression analysis with Aging Day and pH was able to explain 87% of the variation in aerobic plate counts for pork. After 28 d of vacuum aging, loin sections from the upper end of the pH distribution had about a 3 log(1000X) greater aerobic plate count than did the lower end pH product. An increase in pH resulted in pork with lower L*, a*, b* and R₆₃₀ − R₅₈₀ values and as Aging Day increased, instrumental measurements of color increased slightly. Although higher pH is associated with improved pork quality, higher pH and longer aging periods will result in increased microbial proliferation and decreased shelf-life. Thus, an intermediate pH may provide the most desirable combination of quality and shelf-life when extensive aging is used.     

Effects of stress by unfamiliar sounds on carcass and meat traits in bulls from three continental beef cattle breeds at different ageing times

One-hundred-and-twenty-four young bulls of three Continental beef cattle breeds were used to study the effect of pre-slaughter stress by unfamiliar sounds on carcass traits and quality characteristics of beef aged for three different periods. Stress due to unfamiliar noises had a moderately negative effect on carcass and meat quality. Carcasses from group Stressed had higher (P < 0.05) values of pH₀, pH₂₄, a*, and Warner-Bratzler shear force, and lower (P < 0.05) values of L*, b* and pressure losses than from Unstressed animals. There were significant differences (P < 0.05) among breeds in L*, a* and pressure losses. The ageing time had a significant effect on chromatic variables, WBSF and pressure losses. The cooking losses were not significantly affected by any of the three factors discussed. These results emphasize the importance of implementing appropriate management practices during pre-slaughter handling of cattle in order to reduce any possible risk factor for stress, as well as the different sensitivity of the breeds to similar stimuli.     

Effects of L- or D-lactate-enhancement on the internal cooked colour development and biochemical characteristics of beef steaks in high-oxygen modified atmosphere

The effects of L- or D-lactate on internal cooked colour development of steaks packaged in high-oxygen (80% O₂/20% CO₂) modified atmosphere packaging (MAP) was investigated. Ten USDA Select beef strip loins were divided individually into 4 equal-width sections, and one of four treatments (control, 0.3% sodium tripolyphosphate, 2.5% L-lactate + 0.3% sodium tripolyphosphate, and 2.5% D-lactate + 0.3% sodium tripolyphosphate) was assigned randomly to the loin sections. Loin sections were injected to approximately 10% of their raw weight. Steaks packaged in high-oxygen MAP were stored in the dark at 1 °C for 10 days. Instrumental internal colour of raw and cooked steaks (70 °C), total reducing activity (TRA), NADH concentration, and percent myoglobin denaturation (PMD) were measured. Cooked steaks enhanced with 2.5% L-lactate/phosphate maintained higher a*/b* ratios, lower hue values, higher TRA and NADH concentration, and lower PMD than the control and D-lactate-injected steaks, whereas enhancement with 2.5% D-lactate did not affect cooked colour, TRA, NADH, or PMD. Thus, inclusion of an L-lactate/alkaline phosphate blend increased the reducing activity of muscle tissues by replenishing NADH and subsequently decreased the thermal denaturation of myoglobin by maintaining the reduced state of myoglobin in the high-oxygen package.     

Retardation of myoglobin and haemoglobin-mediated lipid oxidation in washed bighead carp by phenolic compounds

Antioxidative activities of phenolic compounds (caffeic acid, gallic acid and tannic acid; 200 ppm) in washed mince (pH 6), with added myoglobin (Mb) and haemoglobin (Hb), from bighead carp (Hypophthalmichthys nobilis), during 9 days of iced storage, were studied. Tannic acid exhibited the preventive effect on discolouration of washed mince containing Mb or Hb during storage (P < 0.05). High peroxide value (PV) was found and large amount of, thiobarbituric acid-reactive substances (TBARS) and hexanal were formed in washed mince containing haem proteins, especially Hb. As determined by apo Streptococcal haem-associated protein, Hb had the lower haem affinity than Mb. Phenolic compounds, especially caffeic acid and gallic acid, could lower lipid oxidation induced by Mb or Hb throughout storage (P < 0.05). Prevention of haem release, as well as inhibition of lipid oxidation induced by haem proteins with selected phenolic compounds, should be an alternative means in lowering discolouration and lipid oxidation in fish muscle.     

Characterization of acid-soluble collagen from the skin of walleye pollock (Theragra chalcogramma)

Acid-soluble collagen (ASC) was extracted from the skin of walleye pollock (Theragra chalcogramma) and partially characterized. It exhibited a maximum absorbance at 220 nm, but little absorbance near to 280 nm. Amino acid composition and SDS-PAGE suggested that the collagen might be classified as type I collagen. Moreover, FTIR investigations showed the existence of helical arrangements of collagen. The denaturation temperature (T_d) and shrinkage temperature (T_s) were 24.6 °C and 47 °C, respectively, both lower than those of mammalian collagens. However, T_d of walleye pollock skin collagen was higher than that of cod skin collagen reported previously. These results indicate that walleye pollock skin is a potential source of collagen and provide the theoretical basis for further research.     

Physicochemical properties and bioactive compounds of selected seed oils

The physicochemical properties and chemical composition of oil extracted from five varieties of plant seeds (bittermelon, Kalahari melon, kenaf, pumpkin and roselle seeds) were examined by established methods. The thermal properties of extracted oils by differential scanning calorimetry were also evaluated. Sensorial profiles of these seed oils were defined through the CieLab (L*, a*, b*) colour. Most of the quality indices and fatty acid compositions showed significant (P < 0.05) variations among the extracted oils. Physicochemical properties of the oils extracted were iodine value, 86.0-125.0 g I₂/100 g oil; saponification value, 171.0-190.7 mg of KOH/g of oil; acid value, 1.1-12.9 mg of KOH/g of oil, free fatty acid, 0.6-6.5 g/100 g of oil, and peroxide value 1.5-6.5 meq of O₂/kg of oil. Palmitic, oleic and linoleic acids were the major fatty acids in all of the extracted seed oils except for bittermelon, where eleostearic acid was the major fatty acid. Gallic, protocatechuic, p-hydroxybenzoic, vanillic, caffeic, syringic, p-coumaric and ferulic acids were identified in the extracted plant oils. Among these, vanillic acid was predominant in all extracted oils. The oils were rich in tocopherols with γ-tocopherol as the major components in all oil samples. Among the phytosterols, sitosterol was the major phytosterol extracted from the five plant seed oils. The seeds of these plants contain a great number of valuable minor compounds, which have a potential high value as food and for production of non-food products.