A new histopathology scoring protocol reveals myopathy features in PSE-like pork.

Pale, Soft, and Exudative (PSE)-like pork defects are associated with fiber destruction and pale discoloration and have become a severe economic burden for the European meat sector. However, robust detection of PSE-like pork and its diverse features is challenging and makes studies into defect causation difficult. Implementation of histological examination may improve our knowledge about less-known features linked to PSE-like defects. Here we evaluate if a new histological protocol can reveal how myopathy in ham may be associated with visual and traditional physicochemical anomalies of PSE-like pork. We first created a list of pathological features, quantified them, and integrated them into a myodegeneration scoring scheme (MYO) for semimembranosus muscle sections. We then explored potential associations between overall MYO scoring and individual histology features with visual PSE-like defect scoring (DES) and with individual meat quality variables [pHu, color: L*, a*, b* (CIELAB), bioimpedance, and near-infrared spectroscopy (NIR)]. As the primary finding of this study, we show a significant association between overall myopathy (MYO) scoring and PSE-like defect (DES) scores. We also found associations of specific myopathy features with DES scores, and of overall MYO scoring with specific quality variables. In all, our data suggest links between signs of acute myodegeneration and PSE-like defects. Our data, hence, supports the implementation of semi-quantitative histopathological approaches for diagnosing PSE-like pork features and may help identify the underlying mechanisms behind these defects.

Lipid oxidation in minced beef meat with added Krebs cycle substrates to stabilise colour.

Krebs cycle substrates (KCS) can stabilise the colour of packaged meat by oxygen reduction. This study tested whether this reduction releases reactive oxygen species that may lead to lipid oxidation in minced meat under two different storage conditions. KCS combinations of succinate and glutamate increased peroxide forming potential (PFP, 1.18-1.32 mmol peroxides/kg mince) and thiobarbituric acid reactive substances (TBARS, 0.30-0.38 mg malondialdehyde (MDA) equivalents/kg mince) under low oxygen storage conditions. Both succinate and glutamate were metabolised. Moreover, under high oxygen (75%) storage conditions, KCS combinations of glutamate, citrate and malate increased PFP (from 1.22 to 1.29 mmol peroxides/kg) and TBARS (from 0.37 to 0.40 mg MDA equivalents/kg mince). Only glutamate was metabolised. The KCS combinations that were added to stabilise colour were metabolised during storage, and acted as pro-oxidants that promoted lipid oxidation in both high and low oxygen conditions.

Protein expression and oxygen consumption rate of early postmortem mitochondria relate to meat tenderness.

Oxygen consumption rate (OCR) of muscle fibers from bovine semimembranosus muscle of 41 animals was investigated 3 to 4 h and 3 wk postmortem. Significant relations (P < 0.05) were found between OCR measurements and Warner-Bratzler shear force measurement. Muscles with high mitochondrial OCR after 3 to 4 h and low nonmitochondrial oxygen consumption gave more tender meat. Tender (22.92 ± 2.2 N/cm2) and tough (72.98 ± 7.2 N/cm2) meat samples (4 samples each), separated based on their OCR measurements, were selected for proteomic studies using mitochondria isolated approximately 2.5 h postmortem. Twenty-six differently expressed proteins (P < 0.05) were identified in tender meat and 19 in tough meat. In tender meat, the more prevalent antioxidant and chaperon enzymes may reduce reactive oxygen species and prolong oxygen removal by the electron transport system (ETS). Glycolytic, Krebs cycle, and ETS enzymes were also more abundant in tender meat

Mitochondrial oxygen consumption in permeabilized fibers and its link to colour changes in bovine M. semimembranosus muscle.

Animal and muscle characteristics were recorded for 41 cattle. The oxygen consumption rate (OCR) of M. semimembranosus was measured between 3.0-6.4h post mortem (PM3-6) and after 3 weeks in a vacuum pack at 4°C. Colour change measurements were performed following the 3 weeks using reflectance spectra (400-1,100 nm) and the colour coordinates L, a and b, with the samples being packaged in oxygen permeable film and stored at 4°C for 167 h. Significant individual animal differences in OCR at PM3-6 were found for mitochondrial complexes I and II. OCR of complex I declined with increased temperature and time PM, while residual oxygen-consuming side-reactions (ROX) did not. OCR of stored muscles was dominated by complex II respiration. A three-way regression between samples, colour variables collected upon air exposure and OCR of 3 weeks old fibres revealed a positive relationship between OCR and complex II activity and also between OCR and OCR(ROX). The presence of complex I and ß-oxidation activities increased metmyoglobin formation.

Flavor release of the tomato flavor enhancer, 2-isobutylthiazole, from whey protein stabilized model dressings.

A tomato flavor enhancer, 2-isobutylthiazole (IBT), was added (5 mg/kg) to dressings emulsified with either a whey protein concentrate-80 (WPC-80), a WPC-80 hydrolysate or ß-lactoglobulin at high pressure (70 MPa) at either 20 or 75 °C. The short (2-4 min), high-temperature treatment left the proteins essentially unchanged. IBT addition gave a dominant, green tomato flavor that masked the intrinsic odor of the WPC-80 hydrolysate but enhanced bitter flavor. The sensory IBT odor intensity was determined by oil level (5-30%) and pH; pH 4.0 gave higher IBT odor than pH 6.5. The green (IBT) odor release correlated with the sensory viscosity (p = 0.001) and with instrumentally determined complex modulus (p = 0.001), but not to the dressings' microstructure. The presence of small (<<1.5 µm) oil particles that were difficult to identify from images may explain why no correlation between green odor and microstructure was found. Headspace analysis significantly detected differences in the release of IBT from the different protein types: WPC-80 dressings released the most and ß-lactoglobulin the least amounts of IBT into headspace. As this difference in release of IBT among proteins could not be verified by sensory analysis, it may bear no relevance for perception.

Norwegian consumers' acceptability of boar tainted meat with different levels of androstenone or skatole as related to their androstenone sensitivity.

The aim of work was to study Norwegian consumers' acceptance of pork meat with different levels of skatole and androstenone. One group of androstenone sensitive consumers (N=46) and one group of non sensitive consumers (N=55) participated in a home test and evaluated 11 samples with different skatole (range 0-0.35 ppm) and androstenone (range 0-9.0 ppm) levels. Liking of odour during frying and odour and flavour of the fried meat were evaluated. Results showed that the non sensitive consumers accepted all levels of androstenone in the samples. Sensitive consumers gave a significantly lower liking score for androstenone samples containing 3 ppm (and more) than the reference sample when evaluating these samples above the frying pan, but no significant difference were found between 3 ppm samples and reference samples when liking of fried meat was evaluated. This indicated that the sensitive consumers accepted 3 ppm in fried meat, but not if 3 ppm was present in the sample during the frying process. The same consumer's differentiated skatole samples with regard to flavour at 0.15 ppm. The Norwegian established practise with a threshold value of 0.21 ppm skatole is higher than the value accepted by the consumers.

Nondestructive analysis of salt, water, and protein in dried salted cod using computed tomography.

Computed X-ray tomography (CT) was used to determine NaCl, water, and protein levels in dried salted cod. Cod fillets were salted and dried, and CT was conducted several times during the process. Also, homogenized cod samples with a chemical composition covering the typical composition of cod during salting and drying were produced, and CT scanned. Chemical composition of fillet and model samples was predicted from CT images acquired at 80, 110, and 130 kV. The best average prediction errors (RMSECV) obtained for homogenized samples were 0.6% NaCl, 1.3% water, and 1.5% protein; all explained variances were R2= 0.99 or above. The best RMSECVs and explained variances for cod fillet samples were 0.9% NaCl (R2= 0.96), 0.8% water (R2= 0.99), and 1.4% protein (R2= 0.79). Combining CT values from 2 or 3 voltages gave the best predictions except when predicting salt in cod fillet, where 1 voltage was sufficient.

Prediction of fat, muscle and value in Norwegian lamb carcasses using EUROP classification, carcass shape and length measurements, visible light reflectance and computer tomography (CT).

One hundred and twenty carcasses were sampled to compare different techniques or methods for prediction of lamb carcass composition and value. Four methods that are used at the Norwegian Meat Research Centre, Animalia, were selected. These were the basic EUROP classification, the advanced EUROP classification using carcass shape and length measurements, visible light reflectance probing (GP) and Computer Tomography (CT). The different technologies were tested using an iterative approach, selecting calibration and validation data sets from the 120 carcasses randomly, where 90 carcasses were used for calibration, and 30 for validation. The best prediction models were obtained using CT, with respect to prediction error and correlation between predicted and measured value of carcass fat and muscle (in kg), and value (in NOK). Due to high cost and low operating speeds of CT, optical probing (GP) may be the second best solution of the technologies used in this study, combined with a CT dissection reference as an alternative to manual dissection.

Determination of sodium chloride in pork meat by computed tomography at different voltages.

Ground pork samples simulating the widely different chemical composition of hams during dry-cured ham production were produced and scanned by x-ray computed tomography (CT). Chemical composition accounted for most of the variation in CT values (97%). Tube voltage (80, 110, and 130 kV) affected CT value and the effect varied between different types of tissue. Sodium chloride (NaCl) was predicted in the ground samples with average prediction errors (RMSEP) as low as 0.2% to 1.0% NaCl. NaCl was also predicted in small samples of raw to dry-cured ham. When dry and fat ham samples were left out of the models, NaCl was predicted with a high precision (RMSEP 0.2% to 0.4% NaCl, R(2) > 0.99). CT can be used as a valuable, nondestructive tool to analyze distribution of and quantify NaCl in ham during dry-curing.

Marinating as a technology to shift sensory thresholds in ready-to-eat entire male pork meat.

This study investigated the effect of marinades in improving the eating quality in ready-to-eat boar meat. Neck chops with fat content below 18.9%, skatole ⩽1.1ppm (range 0.03-1.1) and androstenone ⩽5.6ppm (range 0.01-5.6) were used. In a screening experiment different marinades were tested for their ability to mask boar taint (defined as manure and urine odour and flavour). Liquid smoke and oregano extracts appeared to have the best potential for masking, and were studied in detail. Results from the study indicated that marinated chops with skatole content of approximately 0.4ppm appeared similar to castrates in boar taint. Chops with skatole contents above 0.7ppm remained unmasked despite the use of strongly flavoured marinades. Unmarinated chops served at 60°C were more tainted than those served at 15°C, but scored lower for boar taint when reheated, although the concentrations of androstenone and skatole remained the same. The fat content of the chops was not well correlated to the perception of boar taint. The attributes manure and urine were correlated with the level of skatole, but urine attribute was not a good indicator of the androstenone level.

Characterization of volatile compounds in a fermented and dried fish product during cold storage.

The northern European production technique for dry-cured meat sausages was used to produce a sliceable, fermented, and dried fish product rich in omega-3 polyunsaturated fatty acids (PUFA). The fatty fish Atlantic salmon (Salmo salar), the lean fish saithe (Pollachius virens) (1:1, w/w), Lactobacillus sakei, and 4 different milk protein-based ingredients were used in the recipes. The changes in the volatile compounds during cold storage (+4 degrees C) of vacuum-packed dried sausages were studied by dynamic headspace gas chromatography-mass spectrometer (GC-MS). Of the 117 volatile compounds identified, alcohols, alkanes, esters, aldehydes, ketones, and compounds derived from amino acids were the most prevalent groups of volatiles. Thirty volatiles decreased and 17 increased significantly (P < 0.1) during storage for 15 wk. Despite the high content of PUFA, amino acid catabolism and ester synthesis led to larger changes in the composition of volatiles in the fish product than did lipid oxidation reactions. The milk-protein-based powders that were used to physically stabilize the fish oil did not affect the lipid oxidation compounds.

Control of lightness and firmness of cold and reheated frankfurter-type sausages using different spectroscopic methods applied to raw batter.

Muscle types and collagen, fat, and muscle protein minus collagen were varied in cooked frankfurter-type sausages made from beef and pork meat as well as pork backfat. The content of collagen was fixed at preset levels with pork rind. The amount of total muscle protein in the sausages varied between 5.9% and 11.9% and the fat between 16.1% and 22.1%. The collagen content varied between 1.3% and 4%. Spectroscopic measurements (near-infrared reflectance spectra 1100 to 2500 nm; front-face autofluorescence emission spectra 360 to 640 nm) on raw batters were used to predict the amounts of total muscle protein minus collagen, collagen, myoglobin, and fat (biochemical components), L* values from a Minolta chromameter, and firmness of cold (22 degrees C) and reheated sausages (60 degrees C). Lightness of sausages was most accurately determined from the batter data with a Minolta chromameter or the autofluorescence measurement system. Firmness of cold sausages could be described by the amounts of biochemical components plus the type of muscle used in the sausage. The 2nd-best approach was to use the shape of the near-infrared spectra to determine firmness. This was possible as the shape of near-infrared spectra depended on total protein content, and total protein content largely determined the firmness of cold sausages. If the sausages were reheated to 60 degrees C, near-infrared spectroscopy alone determined firmness of the sausages with a lower accuracy than a combined solution of fluorescence and near-infrared spectroscopy. The 2 spectroscopic techniques could thus be used to estimate the amount of biochemical components in sausages. Once these components were known, firmness could be calculated from a model between the amounts of biochemical components and firmness. For reheated sausages, as opposed to cold ones, there was a need to differentiate between collagen and the other muscle proteins in order to determine firmness. This was optimally achieved by using both autofluorescence and near-infrared spectroscopy.

Computed tomography for quantitative determination of sodium chloride in ground pork and dry-cured hams.

Seventy-five ground meat and fat samples of pork with varying composition of sodium chloride (0% to 16%), fat (1% to 82%), protein (1% to 46%), and water (13% to 76%) were scanned by X-ray computed tomography (CT) at 110 kV. The dependency of CT value on chemical composition and the linear relationships between sodium chloride (NaCl) and CT value were modeled. When all ground samples were used for modeling and no information of chemical composition was included in the model, the prediction error for NaCl was 2.8%. Adding information on fat or protein content to the model reduced the error to 1.6%. A minimal prediction error of 0.2% for NaCl was found when the variation in chemical composition was strongly reduced. In addition, 22 samples of dry-cured ham lean and fat tissues at different processing stages were CT scanned; their chemical compositions were 0% to 14% NaCl, 1% to 85% fat, 5% to 33% protein, and 7% to 76% water. The NaCl content in dry-cured ham samples was modeled with prediction errors of 0.6% to 2.1%, depending on which chemical component was included in the models. In general, predictions were improved if either the range of concentrations was reduced or information of chemical composition was included in the models. Important sources of error in the models were the reproduction error for ground samples, and for ham samples the analytical errors in determining the chemical composition.

Calcium binding and concomitant changes in the structure and heat stability of calprotectin (L1 protein).

Aim-To obtain further data on the structure and conformation of calprotectin, a prominent leucocyte protein found in many species.Methods-The binding of Ca(2+) to calprotectin was studied by means of equilibrium dialysis using (45)Ca as tracer. The thermal stability and denaturation kinetics of calprotectin were studied by means of differential scanning calorimetry. Con-comitant alterations in optical activity resulting from different conditions were measured. A computer program calculated the parameters to fit different models of protein structure. Ultraviolet spectroscopy gave absorbtion spectra. Sedimentation velocity studies and molecular weight determinations by the low speed (sedimentation) equilibrium technique were performed.Results-A maximum of six calcium ions were bound per calprotectin molecule at 0.7 mM calcium chloride. The apparent dissociation constants were calculated. Ca(2+) ions increased the denaturation temperature by 26 degrees K. The enthalpy of denaturation was also increased by Ca(2+). Addition of Ca(2+) to the buffers caused a gradual change in the near UV circular dichroism spectrum, while only minor changes were seen at wavelengths of 210-240 nm. A gradual increase in the sedimentation coefficient was observed on addition of calcium chloride. The extinction coefficient at 279nm was determined: E(279)= 2.53.10(4) M(-1) cm(-1).Conclusions-Calprotectin can bind six calcium ions. Upon binding, the protein shows distinct conformational changes and increased thermal stability. The former may be of importance for its function, while the biological significance of the latter is unknown.

Rheological parameters as predictors of protein functionality: A model study using myofibrils of different fibre-type composition.

The rheology of myofibrils from a typical red muscle, m. masseter, and a typical white muscle, m. cutaneus trunci, has been studied at different pH values and salt and myofibrillar-protein concentrations. The storage modulus G' and the phase angle δ were related to the parameters pH, salt, and muscle, by using partial-least-square-two-block modelling. At high and low temperatures, G' was largely affected by pH and salt, respectively. For δ, the reverse was observed. The peak G' observed at temperatures between 40 and 60°C is an indicator of salt addition above the physiological salt level for both types of myofibrillar system. The magnitude of the change in G' per degree, in the temperature range 40-60°C, was the most muscle-specific parameter observed, and the peak was larger for cutaneus trunci than masseter myofibrils. At high temperatures (80°C), the cutaneus trunci myofibrils, for technical relevant conditions, formed stronger gels than masseter myofibrils. The cutaneus trunci systems also aggregated more strongly and exuded more water than systems of masseter myofibrils. The effect of strain on G' was generally larger for cutaneus trunci than for masseter myofibrillar systems. Many observations on myofibrillar systems were transferable to real-meat systems, which were also examined.

The denaturing action of lysophosphatidylcholine as studied by calorimetric and rheological techniques.

The potency of lysophosphatidylcholine to perturb protein structure was investigated by differential scanning calorimetry and rheological measurements using myosin as a model protein. At physiological ionic strength (0.15 M NaCl) 5mM lysophosphatidylcholine produced a detectable reduction in the protein's enthalpy of denaturation, while concentrations less than or equal to 2 mM had no effect. At higher salt concentrations (0.6 M NaCl) lower concentrations of lysophosphatidylcholine were needed in order to reduce the enthalpy of denaturation. Also, the changes in myosin conformation, as judged from calorimetric measurements, became more extensive as the incubation temperature for myosin-lysophosphatidylcholine systems was increased from 10 degrees to 30 degrees C. Rheological techniques allowed detection of changes in the structure of filaments of myosin (in 0.15 M) upon addition of 0.2 mM lysophosphatidylcholine. The denaturing action of lysophosphatidylcholine is compared to the more familiar detergent sodium dodecyl sulphate.

Conformation and structure of mildly heat-treated ovalbumin in dilute solutions and gel formation at higher protein concentrations.

The conformation of heat-denatured ovalbumin aggregates has been examined at several concentrations and pH values, using measurements of optical rotation dispersion (ORD), circular dichroism (CD) and viscosity. The protein was subjected to heating at relatively low temperatures, ranging from 48.5 to 76 degrees; the particular temperature chosen depended on pH. The heat treatment was sufficient to remove the ability of the molecules to absorb heat on re-heating. The denatured molecules were shown to be rather compact, i.e. not much larger than the native molecule, and to retain a significant amount of secondary structure; this was also the case for molecules present in small aggregates. It is suggested that this type of ovalbumin monomer builds three-dimensional networks in denatured solutions at higher concentrations, and that gelation should be looked upon as arising from surface contacts between hydrated globules. The present results also imply that such globules have gelation properties which depend on whether pH is acidic or basic compared to the isoelectric point of the protein.

Effects of electrical stimulation and ageing of beef on the gelation properties and protein extractability of isolated myofibrils.

The gelation properties of bovine myofibrils, as evaluated by dynamic rheological measurements, were shown to be very sensitive to the variables investigated: stimulation and/or ageing of the meat used, presence of 5 mM pyrophosphate and 5 mM MgCl(2) (PP) and concentration of NaCl (0·3 or 0·M). Statistical evaluation of final gel storage moduli (determined at 70°C) revealed ageing to have a consistent detrimental effect. Fresh, stimulated processing of meat), gave gels of about 40% lower elasticity (storage modulus) than did non-stimulated myofibrils; when PP was included in the gel-forming mixture no effect from electrical stimulation was seen. In spite of the negative effects observed for gel elasticity, the myofibrils in question displayed enhanced protein extractability prior to heating. Electrophoretic results suggest myosin degradation to be partly responsible.

Effect of alkylation with different sized substituents on the conformation of ovomucoid, lysozyme and ovotransferrin.

Conformational changes induced in ovomucoid, lysozyme and ovotransferrin on reductive addition of different sized substituents have been studied employing differential scanning calorimetry (DSC) and circular dichroic spectroscopy (CD). The thermograms obtained by DSC revealed that extensive introduction of methyl, isopropyl, cyclopentyl, cyclohexyl, benzyl or n-butyl groups has a detrimental effect on thermal stability (enthalpy of denaturation); the effect generally increases with the size of the substituent. Circular dichroic spectra were affected only to a very limited extent by the modifications, near-u.v. spectra remaining much the same while far-u.v. spectra displayed minor changes. The general conclusion drawn is that the modifications had only limited effects on the conformation of the proteins while, nonetheless, perturbing (or breaking) long-range intramolecular interactions so as to destabilize the structure. Derivatization of lysozyme and ovotransferrin with some of the larger groups has been reported to result in spontaneous precipitation of the proteins [Fretheim, K., Iwai, S. & Feeney, R.E. (1979) Int. J. Peptide Protein Res. 14, 451-456]. The present investigation indicates that precipitation was caused by (partial) denaturation (and ensuing aggregation) as a consequence of modification.

Immunological monitoring in patients with end-stage renal disease.

Parameters of cell-mediated immune function were determined in 76 patients with end-stage renal disease. Lymphocyte subpopulations (OKT3, OKT4, OKT8, OKIa1, OKM1, OKT9, OKT10), natural killer (NK)-cell activity (percentage 51Cr release from K562 targets), and delayed cutaneous hypersensitivity were measured and correlated with other variables. The results indicate that (1) uremic patients have a significant diminution in the OKT4-lymphocyte subpopulation and OKT4/OKT8 (helper/suppressor) ratio compared to normal controls; (2 blood transfusions do not induce significant alterations in the helper/suppressor-cell ratio; (3) uremic patients have a significant increase in OKM1 cells compared to normal controls; (4) the majority of uremic patients in this series developed delayed cutaneous hypersensitivity responses to recall antigens and could be de novo sensitized to 2,4-dinitrochlorobenzene (DNCB); (5) skin-test reactivity could not be correlated with total circulating T cells or levels of any lymphocyte subpopulations; and (6) NK-cell activity in uremic patients is not significantly different from that in normal controls. These results highlight the varying levels and function of different lymphocyte subsets in patients with end-stage renal disease when they are treated with chronic maintenance hemodialysis.