Application of proteomics to understand the molecular mechanisms behind meat quality

The proteome is expressed from the genome, influenced by environmental and processing conditions, and can be seen as the molecular link between the genome and the functional quality characteristics of the meat. In contrast to traditional biochemical methods where one protein is studied at a time, several hundred proteins can be studied simultaneously. Proteomics is a promising and powerful tool in meat science and this is reflected by the increasing number of studies emerging in the literature using proteomics as the key tool to unleash the molecular mechanisms behind different genetic backgrounds or processing techniques of meat. Thus understanding the variations and different components of the proteome with regard to a certain meat quality or process parameter will lead to knowledge that can be used in optimising the conversion of muscles to meat. At present, there has been focus on development of techniques and mapping of proteomes according to genotypes and muscle types. In the future, focus should be more towards understanding and finding markers for meat quality traits. This review will focus on the methods used in the published proteome analyses of meat, with emphasis on the challenges related to statistical analysis of proteome data, and on the different topics of meat science that are investigated.     

Relationships between storage protein composition,protein content,growing season and flour quality of bread wheat

The storage protein composition from the Glu‐1, Glu‐3 and Gli‐1 loci encoding high and low molecular weight glutenin subunits (HMW‐GS and LMW‐GS) and gliadins, respectively, was determined on 30 wheat (T aestivum L) genotypes from three growing seasons. The gliadins and the LMW‐GS were identified as gliadin/LMW‐GS pairs. All samples were analysed by two one‐dimensional electrophoretic techniques, and selected samples were also subjected to two‐dimensional electrophoretic separation. Different statistical/data‐analytical techniques were evaluated in the study of how the presence or absence of the protein alleles, the protein content and the growing seasons are related to flour quality. The year of growth had a large impact on mixograph peak time. When predicting mixograph peak time from the presence or absence of significant proteins and the year of growth, 70% of the variability in mixograph peak time could be explained, whereas only 49% of the variability could be explained when the year of growth was deleted from the model. Protein had no effect on mixograph peak time as expected, and the well‐known positive effect of HMW‐GS 5 + 10, and the negative effects of 2 + 12 and 6 + 8 was observed. Furthermore, some of the gliadin/LMW‐GS combinations influenced mixograph peak time significantly. The gliadin/LMW‐GS at the combined Gli‐A1, Glu‐A3 loci b; ?? was positively related to mixograph peak time, whereas ??; ?? and a;a was negatively related. Although the LMW‐GS component ?? of the alleles b; ?? and ??; ?? alleles appear similar on one‐dimensional gels, two‐dimensional separation of selected samples may suggest that the ?? components in these alleles are different proteins. Cross‐validated partial least squares regression combined with empirical uncertainty estimates (jack‐knifing) of the parameters estimated in the model, gave similar results to ANOVA in identifying quality related protein alleles. The applicability of the multivariate approach in proteomics is, however, much wider. Copyright © 2004 Society of Chemical Industry     

Influence of salt concentration on the salting kinetics of cod loin (Gadus morhua) during brine salting

The influence of different salt concentrations of 6%, 15%, 18% and 24% (w/w) on mass transfer of water and salt during brine salting of cod loins was studied. An increase in salt concentration accelerated water exudation and salt diffusion in the cod loins. Weight gain of the cod loins increased with decreasing salt concentration and the cod loins in the 6% brine had the highest process yield. The salting kinetic parameter values for total and water weight changes decreased with increasing salt concentration. Inversely, higher salting kinetic parameter values for salt weight changes were observed for higher brine concentrations. The samples brined at 18% and 24% had identical effective diffusion coefficients and the highest effective diffusion value was found in the cod loins brined at 15%.     

Widerstand gegen abrasiven verschleiss und dynamische bruchzähigkeit weisser vanadingusseisen

The wear behaviour under abrasive sliding loading, the structure and dynamic fracture toughness of white cast iron containing (4 – 6)% V are considered in this paper. In wear systems containing hard abrasive particles (silicon carbide), the dynamic fracture toughness and wear resistance increase with increasing austenite content in the structure. In systems with less hard abrasive particles (e.g. flint, garnet) these alloys exhibit a combination of high fracture toughness and high wear resistance. The vanadium-alloyed white cast irons with a predominantly austenitic matrix show more favourable values with respect to both dynamic fracture toughness and wear resistance in comparison with a simultaneously tested chromium white cast iron.     

Quantification of total and specific gram-negative histamine-producing bacteria species in fish using an MPN real-time PCR method

Quantification of histamine-producing bacteria (HPB) is necessary in order to elucidate the role that HPB play in scombrotoxin (histamine) fish poisoning. We report here the evaluation of a real-time PCR method for the quantification of total and specific Gram-negative HPB species in fish using a most probable number (MPN) format. The species-specific real-time PCR assay was 100% inclusive for independently detecting Morganella morganii, Enterobacter aerogenes, Raoultella planticola/ornithinolytica and Photobacterium damselae and did not cross react with other histamine- or non- histamine-producing bacteria. The efficiency of the reactions in the absence and presence of Spanish mackerel enrichment containing 1 × 10⁶ CFU/ml of background microflora were 93-104 and 92-99%, respectively. The MPN-real-time PCR assay accurately quantified total and specific HPB in spiked mahi-mahi (Coryphaena hippurus) and Spanish mackerel (Scomberomorus maculates) samples. These methods were used to quantify total and specific HPB in naturally contaminated, decomposing mahi-mahi, Spanish mackerel and tuna (Thunnus albacares) samples. The results of this study indicate that MPN-real-time PCR assays can be used to accurately enumerate total and specific HPB in fish samples. These assays can be applied to assess the effectiveness of mitigation strategies and understand the relationship between HPB and histamine production in decomposing fish.     

Separating the Role of Particles and the Suspending Fluid for the Flow of Soy Milks

The paper describes a model and a simple experimental method to determine suspension transport properties, separating the role of particles from the suspending fluid. Shear stresses are described as consisting of 2 components: 1st, a shear stress caused by the flow of the suspending fluid and 2nd, a shear stress caused by direct interaction between suspended particles. We show that the determination of these shear stresses of a complex (food) suspension is largely independent of the definition of its suspending fluid. The rheological behavior of soy milks at low and intermediate moisture contents was studied, and results are compared with those obtained previously. The method evidences that the high viscosity of soy milks is predominantly caused by direct particle interaction.     

The effects of salt concentration on conformational changes in cod (Gadus morhua) proteins during brine salting

The effects of different salt concentrations (6%, 15%, 18% and 24% NaCl (w/w)) on the conformational changes of cod muscle proteins during brine salting were examined in this study. Proteins were extracted from the brine salted samples with solutions of 1 M (5.9%) and 4 M (23.4%) NaCl and the quantity of salt soluble proteins (SSP), disulfide bond (S–S), total sulfhydryl (SH) and available SH content in the soluble fraction were determined. Increased salt concentration in cod muscle promoted protein denaturation and aggregation. The SSP and total SH content decreased, whereas the S–S bond and available SH content increased with increased salt concentration in cod muscle. Disulfide bond formation correlated (r = −0.6) with a decrease in total SH groups. Higher SSP and available SH groups of the samples at lower brine concentrations was explained by smaller concentration gradients and salt diffusion rates, resulting in stronger salting-in at early stages of the brining process. There was a significant difference in conformational changes in proteins extracted with a salt solution of 1 and 4 M, mainly due to a different degree of protein aggregation.     

Predicting adult fish acute lethality with the zebrafish embryo: relevance of test duration, endpoints, compound properties, and exposure concentration analysis

The zebrafish embryo toxicity test has been proposed as an alternative for the acute fish toxicity test, which is required by various regulations for environmental risk assessment of chemicals. We investigated the reliability of the embryo test by probing organic industrial chemicals with a wide range of physicochemical properties, toxicities, and modes of toxic action. Moreover, the relevance of using measured versus nominal (intended) exposure concentrations, inclusion of sublethal endpoints, and different exposure durations for the comparability with reported fish acute toxicity was explored. Our results confirm a very strong correlation of zebrafish embryo to fish acute toxicity. When toxicity values were calculated based on measured exposure concentrations, the slope of the type II regression line was 1 and nearly passed through the origin (1 to 1 correlation). Measured concentrations also explained several apparent outliers. Neither prolonged exposure (up to 120 h) nor consideration of sublethal effects led to a reduced number of outliers. Yet, two types of compounds were less lethal to embryos than to adult fish: a neurotoxic compound acting via sodium channels (permethrin) and a compound requiring metabolic activation (allyl alcohol).     

Determination of a kinetic factor influencing the vaporescence of flavour components from wort

The current article considers the question of whether vaporescence during wort boiling affects evaporation via the vapour side mass transport. Thereby the vaporization of unwanted flavour components (such as dimethyl sulphide or benzaldehyde) can be influenced negatively or positively, which affects the amount of energy needed. The question is pursued by pre‐calculation and experimental validation of the vapour side mass stream at the evaporation surface: for that purpose vaporescence trials were carried out in a plant trial, with both benzaldehyde and water as pure substances and a mixture of benzaldehyde and water in an infinite solution (x_i < 10^?6). Trial parameters were process temperature and volume stream of the gas phase. The results obtained by the trials with pure substances enable pre‐calculation of vapour side mass transport. Then, pre‐calculation is compared with the results of the mixture trials and thus verified. As a result it has to be stated that vaporescence in the brew houses is pre‐calculable and that the mass transport has an impact on the vaporescence at the vapour side boundary layer. Copyright © 2016 The Institute of Brewing & Distilling