Postmortem proteome changes of porcine muscle related to tenderness

Proteome analysis was used to investigate the relation between changes in postmortem proteome of porcine muscle and tenderness development. Muscle samples were taken at slaughter and 72 h postmortem, and the registered changes in the proteome were related to Warner-Bratzler shear force. One hundred and three protein spots were found to change significantly (P < 0.01) over time, and of these the 27 most pronounced changes were identified. Eleven out of the 27 changes were fragments of actin. Other identified myofibril proteins or fragments included myosin heavy chain, titin, myosin light chain I, myosin light II, CapZ, and cofilin. Correlation analysis revealed significant correlations between three of the identified actin fragments and the myosin heavy chain fragment to shear force. Moreover, myosin light chain II and triose phosphate isomerase I were also found to correlate significantly to shear force. The results clearly demonstrate that postmortem degradation of actin and myosin heavy chain is related to meat tenderness.     

A capillary electrophoresis method to study postmortem proteolysis in relation to pork tenderness

Identification of factors that determine meat tenderness is of high priority. The aim of this work was to develop a method that can detect indicators of proteolysis in meat early postmortem. The method was validated on pork samples. A procedure to detect differences of extractable lower molecular weight compounds after a prerigor freeze/thaw cycle of meat was developed using capillary electrophoresis. The procedure was able to separate 39 peaks in the electropherograms. Eight of the peaks were correlated (P < 0.1) to Warner-Bratzler shear forces 1 day postmortem (WB1). A multiple linear regression model explained 69% of the variation in WB1 using the areas of four peaks. Several of the peaks used in modeling WB1 were related to the at-slaughter activity of the calpain system. The results presented show that the developed method is able to detect indicators of proteolysis and tenderness at an early time point after slaughter. The method is a new tool intended for studies regarding the mechanisms of postmortem proteolysis and tenderization.     

Model studies on the efficacy of protein homogenates from raw pork muscle and dry-cured ham in binding selected flavor compounds

The binding of sarcoplasmic and myofibrillar proteins extracted from postrigor pork muscle and from 7 and 12 months dry-cured hams with volatile compounds such as 3-methyl-butanal, 2-methyl-butanal, 2-pentanone, hexanal, methional, and octanal was studied using solid phase microextraction and gas chromatography analysis. The binding ability of sarcoplasmic proteins from pork muscle was higher than the ability shown by 7 and 12 months dry-cured ham sarcoplasmic homogenates and also higher than the binding ability of myofibrillar homogenates. The effect of the ionic strength on the binding was also studied. This effect was more important on myofibrillar proteins due to its ability to produce changes on the protein conformation that affect their binding ability. However, the sarcoplasmic protein binding ability was more related to the small compounds present in this homogenate than with the aqueous phase ionic strength.     

Ionic strength and pH-induced changes in the immunoreactivity of purified soybean glycinin and its relation to protein molecular structure

This study examined the immunogenic response of glycinin under varying conditions of pH and ionic strength using enzyme-linked immunosorbent assay. Differential scanning calorimetric (DSC) analysis and Fourier transform infrared spectroscopy (FTIR) were used to investigate the conformational changes induced as a result of these conditions, and the correlation with the changes observed in glycinin immunoreactivity were determined. A highly purified glycinin obtained by isoelectric precipitation followed by native preparative continuous flow electrophoresis was used for these studies. Purity was confirmed by two-dimensional-polyacrylamide gel electrophoresis and mass spectroscopy. DSC and FTIR results suggest that glycinin immunoreactivity is affected by changes in the tertiary and secondary packing of the protein, when flexibility, stability, and accessibility of certain substructures are modified. Aggregation and/or increased compactness of glycinin subcomponents could have potentially prevented epitopes from reacting with the IgG antibodies.     

Studies on the rhizosphere microflora of onion plants in relation to temperature changes

A study was made of the changes in the rhizosphere microflora of onion seedlings grown under controlled conditions at either 25, 18 or 16°C. In plants grown at the lower temperatures there was a very small rhizosphere effect for the bacteria compared with that for plants grown at 25°C. A series of tests on bacteria isolated from both rhizosphere and root-free soil showed the rhizosphere isolates from seedlings grown at 25°C to be more active physiologically than those from seedlings grown at the lower temperatures. In particular, the ammonifying bacteria were greatly increased in the rhizosphere of plants grown at 25°C. Numbers of rhizosphere fungi were also greater at the higher temperature but the rhizosphere effect was not as great as that for bacteria. Contrary to expectation the greatest rhizosphere effect did not occur at the optimum temperature for growth of the onions.     

不同气调包装方式的冷却猪肉在冷藏过程中的微生物变化

冷却猪肉分别采用真空包装、CO-MAP(CO+CO₂+N₂)包装、高氧-MAP(高浓度O₂+CO₂+N₂)和低氧-MAP(低浓度O₂+CO₂+N₂)包装后，在(4±1)℃贮存3周，每周测定各项微生物变化。结果表明：1)CO-MAP组可抑制腐败细菌的生长，除对乳酸菌抑制作用较弱外，对假单胞菌、肠杆菌科菌和热死环丝菌均具有很强的抑制作用     

Clay dispersion in relation to changes in the electrolyte composition of dialysed red-brown earths

Dialysis and re-suspension of red-brown earths showed dispersion in distilled water independent of the adsorbed cations. Whenever the electrolyte concentration is below the critical coagulation concentration the soil and clay will disperse. Mechanical disturbance greatly enhances the dispersion process. The experiments suggest that the dispersion was influenced by the released salt in the suspensions. The changes with time in the electrolyte composition of dialysed soils and clays showed that the ‘homoionic’ systems are unstable with possible interference with clay dispersion by the generated electrolytes. The importance of free electrolytes, especially calcium, in the management of dispersive red-brown earths is indicated.     

Loess erosion in relation to land-use changes in the ganspoel catchment,central Belgium

This paper examines the changes of land uses and landscape patterns in the Ganspoel Catchment, central Belgium, using aerial photography interpretation (photographs taken in 1947, 1969 and 1986). The comparison of land cover areal changes and a transition matrix were used to assess land-use changes in time and space. The size, fractal dimension and elongation index of patches were quantified for landscape pattern analysis. Grassland increased and farmland decreased in the study area from the 1940s to the 1980s. Forest increased from 1947 to 1969 and decreased from 1969 to 1986. About 49 per cent of the study area experienced changes of land use between 1947 and 1969, and about 36 per cent between 1969 and 1986. The landscape of the study area is more fragmented than it was in the 1940s. Patches have generally increased in number and decreased in size, although the landscape was most fragmented in 1969; fractal dimension of patches are lower, indicating less complex shapes. From 1969 to 1986, 59 per cent of the area of change was on 0–3 degree slopes, and from 1969 to 1986 6.7 per cent was on >8 degree slopes. Changing land uses and landscape patterns may have important ecological implications.     

Maillard reaction and protein cross-linking in relation to the solubility of milk powders

Protein changes in relation to solubility, Maillard reaction (MR), and protein cross-linking in whole milk powder (WMP), skim milk powder (SMP), and whey protein concentrate (WPC) stored at different relative humidities (RHs) were investigated by chemical and electrophoretic methods. WMP and SMP reached minimum solubility rapidly, while WPC showed no change in solubility. The loss of solubility corresponded with development of high-molecular-weight protein complexes observed by two-dimensional electrophoresis. The maximal MR rate occurred at 66% RH for WMP and SMP (high lactose/protein ratios) and 84% RH for WPC (low lactose/protein ratios) based on the furosine and hydroxymethylfurfural contents. However, browning was greatest at 84% RH in all powders. The minimum solubility corresponded with the casein and fat contents. The retention of solubility and minimal protein cross-linking of WPC compared to casein-containing powders suggest that the casein content and cross-linking strongly influence the decrease in the solubility of milk powder.     

Natural variations of precursors in pig meat affect the yield of heterocyclic amines--effects of RN genotype, feeding regime, and sex

Pig meat shows natural variations in the concentrations of precursors of heterocyclic amines (HCAs), which may affect formation of HCAs in cooked pig meat. To study this, 26 pigs with an inherent genetic variation (carriers and noncarriers of the RN(-) allele) were subjected to different feeding regimes (conventional feed compared with feed composed according to organic standards). In addition, the effect of sex (castrated males or females) was considered when assessing chemical and technological meat quality parameters. Concentrations of precursors of HCAs, i.e., creatine, residual glycogen, dipeptides, and free amino acids, were analyzed in the raw meat, and the levels of some HCAs (4,8-DiMeIQx, MeIQx, PhIP, harman, and norharman) were then determined in fried meat patties prepared from these pigs. The RN genotype most affected technological meat quality parameters and the level of precursors of HCAs, especially the level of residual glycogen, where carriers of the RN(-) allele showed levels four times as high as those of noncarriers (75.3 +/- 2.6 compared with 17.2 +/- 2.4 micromol/g meat, least-squares means +/- SE). The increased level of residual glycogen resulted in about 50% lower amounts of total mutagenic HCAs in cooked meat compared with cooked meat from normal pigs. Fried meat from carriers of the RN(-) allele obtained darker crust color than meat from noncarriers. Feeding regime and sex did not significantly affect the chemical composition of the meat or the formation of HCAs.     

Morphological examinations of oxidatively stressed pork muscle and myofibrils upon salt marination and cooking to elucidate the water-binding potential

Pork longissimus muscle samples were subjected to the following three marination conditions: (A) oxidation (40 min) in hydroxyl radical-generating solutions (HRGS; 10 μM FeCl(3)/100 μM ascorbate with 5 or 20 mM H(2)O(2), pH 6.2) containing 0.1 M NaCl and then marination (40 min) in 0.6 M NaCl with 15 mM pyrophosphate (PP); (B) simultaneous oxidation/marination (40 min) in HRGS containing 0.6 M NaCl and 15 mM PP; or (C) the same as condition B except that PP was omitted. Protein oxidation, measured by the carbonyl and tryptophan fluorescence changes, enhanced hydration but increased cooking loss of meat. Light microscopy revealed a dense muscle structure characterized by swollen fibers and reduced intercellular spacing in intermediately oxidized muscle samples marinated with 0.6 M NaCl and 15 mM PP. However, oxidized fibers were more susceptible to transverse shrinkage upon cooking than nonoxidized fibers, which was supported by the dynamic ultrastructural changes in myofibrils observed using phase contrast microscopy. These findings provide a further understanding of the complex impact of oxidation on meat hydration and water-binding.     

Heat-induced changes in myofibrillar protein structures and myowater of two pork qualities. A combined FT-IR spectroscopy and low-field NMR relaxometry study

Low-field NMR T(2) and Fourier transform infrared (FT-IR) measurements were performed on meat samples of two qualities (normal and high ultimate pH) during cooking from 28 degrees C to 81 degrees C. Pronounced changes in both T(2) relaxation data and FT-IR spectroscopic data were observed during cooking, revealing severe changes in the water properties and structural organization of proteins. The FT-IR data revealed major changes in bands in the amide I region (1700-1600 cm(-)(1)), and a tentative assignment of these is discussed. Distributed NMR T(2) relaxation data and FT-IR spectra were compared by partial least-squares regression. This revealed a correlation between the FT-IR peaks reflecting beta-sheet and alpha-helix structures and the NMR relaxation populations reflecting hydration water (T(2B) approximately 0-10 ms), myofibrillar water (T(21) approximately 35-50 ms), and also expelled "bulk" water (T(2) relaxation times >1000 ms). Accordingly, the present study demonstrates that definite structural changes in proteins during cooking of meat are associated with simultaneous alterations in the chemical-physical properties of the water within the meat.     

Dynamics of the microaggregate composition of chernozem in relation to changes in the content of organic matter

Monitoring of soil dispersivity and humus state has been performed in the stationary profile of ordinary chernozem in the Botanic Garden of the Southern Federal University in 2009–2014. The contents of physical clay and sand are almost stable in time, which indicates a quasi-static (climax) equilibrium in the soil. Another (reversible dynamic) process occurs simultaneously: seasonal and annual variation in the mass fractions of clay and silt in physical clay. Variations of humus content in the whole soil and in its physical clay are also observed on the background of seasonal changes in precipitation and temperature. A procedure has been developed for the analysis of the polydisperse soil system with consideration for the quasi-static and dynamic equilibriums. A two-vector coordinate system has been introduced, which consists of scales for changes in the contents of physical clay and physical sand in 100 g of soil and changes in the fractions of clay and silt in 100 g of physical clay. Co-measurements of two dispersivity series of soil samples—actual dynamic and calculated under quasi-static equilibrium (ideal)—have been performed. Dynamic equilibrium coefficients, which cumulatively reflect the varying proportions of physical clay and physical sand in the soil and the mass fractions of clay and silt in physical clay, have been calculated.     

Salt-induced changes in pork myofibrillar tissue investigated by FT-IR microspectroscopy and light microscopy

FT-IR microspectroscopy and light microscopy were used to investigate pork muscle musculus semitendinosus samples, taken from three animals, that were subjected to brine salting at different concentrations (0.9, 3, 6, and 9% NaCl). Differences in spectral characteristics and in microstructure were observed in meat from animals differing in initial pH and varying salt concentrations. The FT-IR data displayed changes in the amide I region from 1700 to 1600 cm(-1). This spectral range was analyzed by principal component analysis (PCA) and partial least-squares regression (PLSR). These methods revealed correlations between the spectral data and the different animals, salt content, moisture content, pH value, and myofiber diameter. A shrinking share of alpha-helical components was related to an increase in salt concentration in the muscle. At the same time, a greater share in nonhydrogenated C=O groups (1668 cm(-1)) was related to an increase in salt concentration in the meat. The share of aggregated beta-strands differed with respect to the different animals but was not influenced by salt concentration. The meat at higher pHs (>6) had less aggregated beta-strands than that at lower pHs (5.6-5.7). It could be demonstrated that simultaneous with changes in microstructure, pH value, salt, and moisture content were alterations in the protein amide I region as measured by FT-IR microspectroscopy, revealing a relationship between these biophysical and chemical parameters and secondary protein structure attributes.     

Soil microbial biomass C and N changes in relation to forest conversion in the Northwestern Turkey

Tree species differ in their effect on soil development and nutrient cycling. Conversion of beech coppice to pine plantations can alter soil physical and chemical properties, which in turn may have significant impacts on soil microbial biomass C and N (C_mic, N_mic). The major objective of this study was to evaluate soil quality changes associated with the forest conversion in humid NW Turkey. Results from this study showed that levels of soil organic carbon (C_org), total nitrogen (N_t), moisture, C_mic and N_mic under beech coppice were consistently higher but levels of pH, CaCO₃ and EC were lower compared to pine plantation. Differences between the forest stands in C_mic and N_mic were mainly related to the size of the C_org stores in soil and to tree species. In addition, high level of CaCO₃ is likely to reduce pools of soil organic C and possibly even microbial biomass C and N in pine forests. The average C_mic:N_mic ratios were higher in soils under beech coppice than pine plantation, while C_mic:C_org and N_mic:N_t percentages were similar in both forest types. These results revealed the differences in microbial community structure associated with different tree species and the complex interrelationships between microbial biomass, soil characteristics, litter quantity and quality. Copyright © 2008 John Wiley & Sons, Ltd.     

Magnetic susceptibility changes in relation to pedogenesis in a Xeralf chronosequence in northwestern Spain

Pedogenesis under aerobic conditions is usually associated with an increase in magnetic susceptibility (χ, mass‐specific), which results from the formation of nano‐sized magnetite and/or maghaemite. In this study, we systematically investigated the χ trend in Xeralfs from a chronosequence of 13 river terraces in an area with a Mediterranean climate in Spain. The soils in the younger terraces are well drained and reddened, but those of the older terraces exhibit redoximorphic features and reduced χ values, because of the presence of a perched water table. In the well‐drained members of the chronosequence, the frequency dependent magnetic susceptibility, χ_FD, which is a proxy for the concentration of nano‐sized pedogenic ferrimagnets such as maghaemite, was highly correlated with the concentration of haematite (Hm), but not with that of goethite (Gt). Also, the peak χ_FD increased with increasing age in the younger freely drained soils, indicating that no steady state had been reached, and decreased with increasing depth. The formation of maghaemite can be explained by either or both of two formation models, namely: (i) ferrihydrite → maghaemite → haematite solid state transformations; and (ii) the reaction of bacterially produced Fe(II) with an Fe hydroxide phase to form magnetite, which is later oxidized to maghaemite. Comparison between these soils and those in other climatic regions indicates that the Hm/χ_FD ratio increases with increasing soil temperature and with the degree of weathering. In the horizons exhibiting redoximorphic features on the higher terraces, there was significantly less Hm and χ_FD in clay than in the well‐drained younger soils, possibly because of reductive dissolution of haematite and maghaemite. Laboratory experiments showed that susceptibility to reductive dissolution increased in the sequence goethite < maghaemite < haematite, which is consistent with the relative abundance of these minerals in the redoximorphic horizons.     

基于绿色荧光蛋白的冷鲜猪肉中大肠杆菌预测模型的构建

为了预测和监控冷鲜猪肉储存过程中腐败细菌大肠杆菌的变化规律,评估产品货架期,建立微生物生长预测模型。该研究将绿色荧光蛋白质粒pGFP转入大肠杆菌DH5α,构建GFP的标记大肠杆菌。基于绿色荧光蛋白报告基因和氨苄青霉素抗性,采用稀释平板法定量追踪检测0～24 ℃条件下冷鲜猪肉中DH5α生长变化。采用Gompertz模型、平方根模型和响应面方程进行数据拟合,构建数学预测模型。结果表明Gompertz模型拟合效果良好,0～20 ℃条件下决定系数R2为0.96～0.99。温度与最大比生长速率平方根、延迟期倒数平方根模型R2分别为0.862、0.948。响应面模型揭示时间、温度对大肠杆菌的生长影响显著(P<0.05),二者交互作用明显,响应面模型R2为0.815。模型能够有效拟合冷鲜猪肉中与温度、时间相关的大肠杆菌的生长变化规律,研究结果为产品储存过程中细菌变化预测提供理论依据。     

Functional and structural properties of 2S soy protein in relation to other molecular protein fractions

The purpose of this investigation is to develop a better understanding of the structure-function relationship of the 2S fraction of soy protein that has not been considered in earnest by the research community. Defatted soy flour was used to extract the three major fractions of the protein (2S, 7S, and 11S). It was found that 2S exhibits better foaming and emulsification properties than the other two molecular fractions. Work was extended to structural properties, which were monitored using spectrophotometry, atomic force microscopy, scanning electron microscopy, small-deformation dynamic oscillation on shear, and large-deformation compression testing. An experimental protocol utilizing glucono-delta-lactone (GDL), GDL with N-ethylmaleimide, or GDL with urea was capable of identifying the nature of molecular interactions responsible for gelation. Surprisingly, it was found that in the initial stages of structure formation, 2S fared better than 7S, with 11S exhibiting the highest rates of aggregation. Given time, however, 7S produced a firmer network with a better water-holding capacity than that of 2S. Non-covalent interactions, as opposed to disulfide bridging, were found to be largely responsible for the changing functionality of the molecular fractions throughout the experimentation from the formation of a vestigial structure to that of a mature gel.     

Management history in relation to changes in the flora of different habitats on an Oxfordshire Estate,England

Comprehensive species lists of the vascular flora of ht eWytham estate near Oxford have been made at several times between 1880 and 1985. These lists were used to assess the effects of particular changes in management on the flora. The data were also used to estimate maximal values for natural (with no change in management) species turnover in different habitats.Natural turnover, except among arable weeds, was very small compared to the rates of change arising from new management practices. The development of modern farming and forestry caused many extinctions. Declines of traditional woodland use, such as coppicing, and in rabbit grazing had less effect, but nevertheless gave rise to some extinctions. When appropriate management was resumed, many plants reappeared which had been considered extinct; new ones also appeared. Even the cutting of scrub on limestone grasslands (cheap and easy compared to artificial grazing) prevented extinctions there.The results suggest that, at least in British habitats with a long history of human use, management considerations are much more important than island biogeography phenomena are to the choice and design of nature reserves.