Effects of Frozen Storage and Cooking on Lipid Oxidation in Chicken Meat

Fresh chicken breast and leg meat samples, which were frozen for 3 months or 6 months at −18°C, were cooked in microwave and convection ovens and then tested for levels of lipid oxidation. After 6 months storage, malonaldehyde in fat from meat samples, as measured by a TBA assay, modified to avoid sample autoxidation, increased 2.5 fold, while the fluorescence excitation (360 nm) and emission (440 nm) spectra increased an average of 34%. Fat from meat cooked in a convection oven averaged 83% higher malonaldehyde concentration and 21% higher fluorescence compared to levels before cooking. Levels of lipid oxidation products in fat from chicken breast and leg meat were not significantly different in microwave compared to convection oven cooking; but certain secondary fluorescent products were higher in meats cooked by convection oven.     

Quantification of Connective Tissue (Hydroxyproline) in Ground Beef by Autofluorescence Spectroscopy

Autofluorescence spectra (excitation wavelengths 300, 332, 365, 380 and 400 nm) were obtained by an optical system to determine collagenous connective tissue (hydroxyproline) and fat content in ground beef. Chemically determined contents ranged from 0.72–7.12% connective tissue and 1.5–17.7% fat. Partial least squares regression (66 samples) resulted in the lowest root mean square error of 0.37% connective tissue (R=0.97) and 1.89% fat (R=0.84) for excitation wavelengths 380 and 332 nm, respectively. The wavelength 332 nm may be feasible for simultaneous determination of fat and connective tissue. Autofluorescence spectroscopy might be well suited for rapid on-line determination of collagen in ground beef.     

Quality characteristics of low fat ostrich meat patties formulated with either pork lard or modified corn starch, soya isolate and water

A trained taste panel could not distinguish (P>0.05) between ostrich meat patties containing either 10% pork lard or 10% of a modified starch/protein isolate (fat replacer) mixture. The panel could distinguish between the types of ostrich muscle/meat cuts used with a significant (P<0.05) number preferring ostrich patties made from meat containing a higher collagen content (±3% vs <1%). The chemical analysis of the patties showed that within the meat classes (Class fillet-de-membraned, Class A-very lean off-cuts and Class B-off-cuts containing visual connective tissue and some fat), the patties containing the pork fat had a +6% higher total fat content than those containing the fat replacer. The fatty acid profiles of the various products were in accordance with the meat type and fat or fat replacer used. The mineral profile was as expected for lean ostrich meat that had spices added. It is concluded that fat replacers can be used successfully for the production of low fat ostrich patties without any negative quality attributes being perceived.     

Observation of the distribution of Zn protoporphyrin IX (ZPP) in Parma ham by using purple LED and image analysis

We investigated the distribution of Zn protoporphyrin IX (ZPP) in Parma ham by using purple LED light and image analysis in order to elucidate the mechanism of ZPP formation. Autofluorescence spectra of Parma ham revealed that ZPP was present in both lean meat and fat, while red emission other than that of ZPP was hardly detected. Although ZPP was found to be distributed widely in Parma ham, it was more abundant in intermuscular fat and subcutaneous fat than in lean meat. The intensity of red emission was weak in muscles that were exposed during the processing. ZPP in both lean meat and subcutaneous fat tended to be more abundant in the inner region than in the outer region. It was thought that ZPP is transferred from lean meat to fat tissue during the processing, resulting in the small amount of ZPP in the lean meat adjacent to subcutaneous fat. Our results led to a completely new hypothesis that ZPP is formed in lean meat and transferred to fat tissue.     

Carrageenans and their use in meat products

Carrageenans are sulfated linear polysaccharides of D‐galactose and 3,6‐anhydro‐D‐galactose extracted from red seaweeds. They have been used by the food industry for their gelling, thickening, and stabilizing properties, and more recently by the meat industry for reduced fat products. Meat is a complex system of muscle tissue, connective tissue, fat, and water; during processing, numerous interactions occur among all these components. These interactions are responsible for the functional properties of the meat system. In meat products, carrageenans contribute to gel formation and water retention. Their addition is of special interest in low‐fat meat products because fat reduction often leads to unacceptable, tough textures. When carrageenans are incorporated in these formulations, they improve the textural characteristics of the product by decreasing toughness and increasing juiciness. Although carrageenan interactions with milk proteins have been studied extensively, the mechanism by which carrageenans interact with meat proteins and the other meat components is not fully understood.     

Phosphate and Modified Beef Connective Tissue Effects on Reduced Fat, High Water-added Frankfurters

The effects of acidic, neutral and alkaline phosphates and amounts of modified beef connective tissue (0, 10 or 20%) were determined on the characteristics of 20% fat/20% water-added frankfurters or 10% fat/30% water-added frankfurters. Processing yields were lowest in both formulations with acidic phosphate. Cured meat color intensity was higher with the acidic phosphate than with alkaline or neutral phosphates. Alkaline or neutral phosphate samples partially recovered losses in emulsion stability that had occurred due to connective tissue level. The addition of 20% connective tissue improved processing yields and decreased cohe-siveness of 10% fat/30% water added frankfurters. Connective tissue addition had no effect on microbial stability. Acidic phosphates might be more effective in direct treatment of high collagen materials in a preblend rather than in direct addition into a frankfurter formulation.     

Diffusion of NaCl in meat studied by (1)H and (23)Na magnetic resonance imaging

The effect of sodium chloride (NaCl) diffusion into meat was investigated. Proton and sodium magnetic resonance imaging were used to determine the diffusion behaviour of brine (NaCl) in porcine Longissimus dorsi and semitendinosus. NaCl diffusion was visualized through images and diffusion coefficients were determined to be in the range 3-7×10(-10)m(2)s(-1), which is in agreement with values reported in the literature. The diffusion coefficient was found to increase during curing, suggesting microstructural changes in the meat. A supplementary experiment proved that the diffusion behaviour of sodium chloride in regions of meat with connective tissue/fat is distinctive from regions with pure myofilament tissue, as anticipated. Apparent diffusion coefficient (ADC) maps showed that meat microstructures shrunk when cured with 20% (w/w) NaCl brine. ADC across (⊥) the main muscle fiber direction decreased more than ADC along (‖) the main muscle fiber direction. The greater shrinkage in the direction across muscle fibers suggests that the curing induced shrinkage of the transverse structures rather than reduction in longitudinal structures.     

Synchronous Front-Face Fluorescence Spectroscopy Coupled with Parallel Factors (PARAFAC) Analysis to Study the Effects of Cooking Time on Meat

ABSTRACT:  In this study, the potential of synchronous front-face fluorescence coupled with chemometrics has been investigated for the analysis of cooked meat. Bovine meat samples (thin slices of 5 cm diameter) taken from  Longissimus dorsi  muscle were cooked at 237 °C for 0, 1, 2, 5, 7, and 10 min under control conditions. Synchronous front-face fluorescence spectra were collected on meat samples in the excitation wavelength range of 250 to 550 nm using offsets (Δλ) of 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, and 160 nm between excitation and emission wavelengths. The synchronous fluorescence landscape containing 360 spectra was analyzed using PARAFAC. The best PARAFAC model presented 2 components since core consistency values for the first 2 components were 100% and the explained variance was 67.98%. The loading profiles of 1st and 2nd components had an optimal Δλ of 70 and 40 nm, respectively, allowing to determine the excitation (exc.) and emission (em.) maxima wavelengths of 1st (fluorescence band at about exc.: 340 to 400/em.: 410 to 470 nm, and peak at exc.: 468/em.: 538 nm) and 2nd (exc.: 294 nm/em.: 334 nm) components. As the loading profile of the 1st component of PARAFAC was assigned to Maillard-reaction products formed during cooking, the profile of the 2nd component corresponded with the fluorescence characteristics of tryptophan residues in proteins. Loadings and scores of the PARAFAC model developed from the synchronous fluorescence spectra enabled to get information regarding the changes occurring in meat fluorophores during cooking of meat at 237 °C from 0 to 10 min.     

STORAGE STABILITY OF MILKFAT GLOBULE MEMBRANE

To investigate changes in structure and function of milk fat globule membrane (MFGM) components due to oxidation of membrane lipids, freeze-dried MFGM were stored under controlled temperature and relative humidity (RH) conditions. It was found that while membranes underwent extensive lipid oxidation when stored under air, fluorescent compounds were formed. These compounds exhibited fluorescence with excitation maxima at 350 nm and emission maxima at 440 nm; which were similar to those of the fluorescent substances derived from the reaction of oxidized fatty acids and primary amines. Formation of high molecular weight proteins was detected by SDS-PAGE in samples stored under air, but not in samples stored under nitrogen and was also affected by time and relative humidity. Activity of xanthine-oxidase, an important prooxidative agent, was greatly influenced by temperature and complete inactivation was observed when MFGM's were stored at 37°C, 50% RH for 1 day.     

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.     

Measurement of lipid oxidation and porphyrins in high oxygen modified atmosphere and vacuum-packed minced turkey and pork meat by fluorescence spectra and images

This paper illustrates that fluorescence spectroscopy and imaging can be used to measure the extent and distribution of lipid oxidation in meat. Minced turkey thighs and pork semimembranosus muscles were stored for 7 and 12 days at 4°C in high oxygen (O(2)) modified atmosphere packages and vacuum. Turkey meat packed in high O(2) atmosphere was oxidised already after 7 days of storage. The sensory rancid odour score was 4.7 (on a scale from 1 to 9) and the TBARS value was 1.86mg MDA/kg. There was also an increase in fluorescence emission intensity in the 410-550nm region, which arises from lipid oxidation products. The combination of unsaturated fatty acids and access to O(2) resulted in lipid oxidation gradients in the turkey meat samples, and these gradients were clearly visualised by fluorescence images. In comparison, pork meat was more stable against lipid oxidation, with TBARS values <0.2mg MDA/kg and no development of fluorescent lipid oxidation products was detected. The fluorescence spectra measured in the present experiment suggest that turkey thighs and pork semimembranosus muscle in addition to protoporphyrin also have a natural content of Zn protoporphyrin. The porphyrin content was higher in pork meat than in turkey meat. It increased during storage time when the meat was packed in vacuum, and it decreased with O(2) availability. The distribution of porphyrins in the meat was visualised by fluorescence imaging.     

肌肉组织学特性与肉品质的关系

畜禽的肉品质受多种因素的影响,其中与肌肉组织学特性关系最为密切。骨骼肌是主要的可食性肉,它由肌纤维、结缔组织和肌内脂肪组成。本文综述了肌纤维类型、肌纤维直径、肌纤维密度、肌纤维面积比例、肌节长度、结缔组织特性、肌内脂肪含量与分布等肌肉组织学特性与畜禽肉品质的关系。     

Use of meat fluorescence emission as a marker of oxidation promoted by cooking

Accumulation of fluorescent pigments in cooked bovine meat (M. Longissimus thoracis) was studied in relationship with the heating parameters (time and temperature). Muscles were aged at 4 °C for 11 days under vacuum before cooking. Meat cooking was performed by applying jets of steam. Three different heating treatments were tested: two with constant surface temperatures of 65 and 96 °C for 300 s, and one with a continuously increasing surface temperature up to 207 °C. After extraction in water/dichloromethane/ethanol, fluorescence pigments were distributed between the apolar phase (emission 420–440 nm after excitation at 360 nm) and the polar phase, where two emission peaks were seen (emission 410–430 and 515 nm after excitation at 360 nm). Fluorescence in the two phases was little affected by heating at the two constant temperatures while it increased exponentially after 1 min of treatment, as the varying temperature reached 141 °C. The maximum fluorescence increases, measured in the extreme conditions of cooking (207 °C/300 s), were of 5000% in the apolar phase and 1700% in the polar phase. Thiobarbituric acid reactive substances (TBARS) and protein carbonyls were measured in parallel. The correlations between these two parameters and the fluorescence emission demonstrated that the interaction between proteins and aldehyde products of lipid peroxidation was mainly involved in the production of fluorescent pigments in cooked meat.     

The effect of cooking temperature on mechanical properties of whole meat, single muscle fibres and perimysial connective tissue

The structural changes in beef semitendinosus caused by cooking were studied by performing tensile tests of the isolated meat components (i.e. single muscle fibres and perimysial connective tissue) and related to the toughness of the whole meat. Whole meat toughness was found to increase in two separate phases upon cooking from 40-50°C, and again from 60 to 80°C with a decrease in meat toughness between 50 and 60°C, in agreement with previous studies. The changes in whole meat toughness at temperatures below 60°C were found to correspond to changes in the mechanical properties of the perimysial connective tissue, whereas changes of whole meat toughness at temperatures above 60°C were found to correspond to increased breaking strength of single muscle fibres. The myofibrillar component explained approximately 47% of the variation in whole meat toughness upon cooking whereas inclusion of the connective tissue component increased the goodness of fit.     

A study on the possibilities of using 3-methylhistidine to quantify skeletal proteins in meat trimmings

The aim of the study was to ascertain whether the amino acid 3-methylhistidine can be used to quantify skeletal meat protein in meat trimmings. 3-Methyhistidine from different carcass trimmings was quantified by a fluorescent HPLC method. Four trimmings with three subsamples each were examined. The subsamples were analysed in duplicate. The results showed high analytical variations between duplicates and subsamples. The average concentration of 3-methylhistidine in the four trimmings was 135 μg/g fat-free and connective tissue-free meat. Compared to earlier studies this value is high. Because of the rather high analytical variation, further research must be done to evaluate the use of 3-methylhistidine as an indicator for skeletal meat proteins in whole carcass trimmings.     

Development of a rapid method based on front face fluorescence spectroscopy for the monitoring of egg freshness: 1—evolution of thick and thin egg albumens

In this preliminary study, the intrinsic fluorescence of thick and thin egg albumens was evaluated as a possible rapid method for the monitoring of egg freshness. The fluorescence emission spectra of tryptophan residues (excitation: 290 nm; emission: 305–430 nm) of proteins and fluorescent Maillard reaction products (excitation: 360; emission: 380–580 nm) were recorded directly on thick and thin albumen samples within 2–3, 4, 5, 9, 10, 12, 16, 18, 23, 25 and 29 days of storage. Principal component analysis (PCA) and factorial discriminant analysis (FDA) were applied to the spectra data sets. Considering tryptophan fluorescence spectra recorded on thick egg albumen, correct classification was observed for 62.8 and 54.3% for the calibration and the validation sets, respectively. Better classification was obtained from thin egg albumen since 67.3 and 69.1% of samples were correctly classified. Considering fluorescent Maillard reaction products, the similarity map determined by the principal components (PCs) 1 and 2 showed a discrimination of eggs as a function of their storage time on both thick and thin albumens. The percentage of samples correctly classified into four groups by the FDA was 97.4 and 91.4% for the calibration and validation thick albumen samples, respectively. It was concluded that fluorescent Maillard reaction products could be considered as fingerprints that may allow the discrimination between fresh and aged eggs.     

Technology for meat-grinding systems to improve removal of hard particles from ground meat

With increased consumption of ground meat, especially ground beef, quality issues for these products have become more important to industry and consumers alike. Ground meats are usually obtained from relatively low-value cuts and trimmings, and may on occasion contain undesirable hard particles. Hard particles in coarse-ground meat products may include bone chips or fragments, cartilage and dense connective tissue; all of which are considered undesirable defects and which can be reduced by utilizing hard-particle removal systems during grinding operations. This review discusses the principles of hard-particle separation from ground meat, the factors which influence performance of particle separation and some commercially available particle removal systems. Product and processing parameters such as initial bone and connective tissue content, fat content, temperature, pre-grinding size and grinder knife design are considered important for removing hard particles effectively. Pressure gradient on the grinder knife/plate interface was found to play a significant role in particle separation from soft (fat and lean) tissue. Various commercial systems, which are classified as central removal and periphery removal systems, are also discussed. Finally, the authors suggest some processing considerations for meat grinding to help achieve the best quality ground meat for consumers' satisfaction.     

POSSIBLE RELATIONSHIPS BETWEEN SHEAR, TENSILE, AND ADHESION PROPERTIES OF MEAT AND MEAT STRUCTURE

Contributions to the structural strength of meat samples by the myofibrillar and connective tissue components were altered by varying the myofibrillar contraction state, muscle type and the cooking temperature. Shear, tensile and adhesion measurements were used to evaluate quantitatively changes in the properties of the samples. Detailed examination of shear and tensile force-deformation curves suggested that the initial effect of shear, compression or tensile force was to produce a yield in the myofibrillar structure. After the initial yield, the applied force was probably resisted mainly by the connective tissue structure. Adhesion and tensile values showed changes which indicated a probable rearrangement of the collagen fibers in the connective tissue network as it adjusted to accommodate changes in the myofibrillar contraction state.     

Effect of Extraction Procedures on Fluorescent Chromophores in Milk

The oxidation of membrane lipids of freeze-dried Milk Fat Globule Membranes (MFGM) was studied using a fluorescence technique involving two different extraction procedures to obtain lipophilic fluorescent chromophores. MFGM underwent extensive lipid oxidation when stored under air, at controlled temperature and humidity and fluorescent compounds were formed with excitation maxima at 350 nm and emission maxima at 440 nm. Direct extraction of fluorescent compounds with an organic solvent mixture (Cl₃CH:CH₃OH 2:1 v/v) gave reproducible results reflecting well the progress of oxidation. Solvent extraction after previous reconstitution (to original water content) of the dry samples was less satisfactory.     

Front-face fluorescence spectroscopy as a tool to classify seven bovine muscles according to their chemical and rheological characteristics

Potential of front-face fluorescence spectroscopy was evaluated to classify muscles according to their chemical and rheological characteristics. Seven bovine muscles (Semitendinosus, Semimembranosus, Tensor fasciae latae, Rectus abdominis, Longissimus thoracis et lumborum, Triceps branchii and Infraspinatus) were taken from 14 animals of the Charolais breed. Chemical characteristics and rheological properties of the meat were determined including dry matter, fat, collagen, protein, peak load, energy required to rupture and cooking loss. Emission spectra in the 305–400 nm, 340–540 nm and 410–700 nm ranges were recorded using front-face fluorescence spectroscopy by fixing the excitation wavelengths at 290, 322 and 382 nm, respectively. Analysis of variance (ANOVA) applied on chemical and rheological parameters showed that these muscles were significantly different (P < 0.01) from each other. Chemical and rheological data were divided into low, medium and high range groups for each variable. The results of PLSDA showed that 305–400 nm spectra were responsible for 67% (calibration), 53% (validation), 96% (calibration) and 55% (validation) of good classification for protein and cooking loss, respectively, while 340–540 nm spectra allowed 75% of good classification (validation samples) for fat content.