High-pressure processing enhances saltiness perception and sensory acceptability of raw but not of cooked cured pork loins-leveraging salty and umami taste.

The salt (NaCl) content in processed meats must be reduced because of its adverse effects on cardiovascular health. However, reducing salt in meat products typically leads to a lower taste intensity and, thus, consumer acceptability. Industry interventions must reduce salt content while maintaining taste, quality, and consumer acceptability. In this context, high-pressure processing (HPP) has been proposed to enhance saltiness perception, though there are contradictory reports to date. The present work aimed to conduct a targeted experiment to ascertain the influence of HPP (300/600 MPa) and cooking (71°C) on saltiness perception and sensory acceptability of meat products. HPP treatment (300/600 MPa) did enhance those two sensory attributes (approx. +1 on a 9-point hedonic scale) in raw (uncooked) cured pork loins but did not in their cooked counterparts. Further, the partition coefficient of sodium (PNa+), as an estimate of Na+ binding strength to the meat matrix, and the content of umami-taste nucleotides were investigated as potential causes. No effect of cooking (71°C) and HPP (300/600 MPa) could be observed on the PNa+ at equilibrium. However, HPP treatment at 300 MPa increased the inosine-5'-monophosphate (IMP) content in raw cured pork loins. Finally, hypothetical HPP effects on taste-mediating molecular mechanisms are outlined and discussed in light of boosting the sensory perception of raw meat products as a strategy to achieve effective salt reductions while keeping consumer acceptability.

An overlooked compound contributing to boar taint and consumer rejection of meat products: 2-Aminoacetophenone.

Mainly skatole and androstenone have so far been considered causative for boar taint. Using a mixed methods approach it is shown herein that 2-aminoacetophenone (AAP) affects human perception of pork, too. We explored the importance of AAP in four trials: (1) chemical analyses of 221 fat samples from boar carcasses revealed that AAP occurs, on average, in similar quantities as skatole while the levels of androstenone being four-fold. (2) ranking tests with mixtures of androstenone and/or skatole with AAP presented on smell strips to trained sensory assessors showed that AAP amplifies boar odour. In order to study AAP's importance in meat products, four experimental variants of Lyon type sausage were then produced: a control, a product with added skatole (0.075 µg/g fat tissue), with added AAP (0.075 µg/g fat tissue), and with addition of both compounds. (3) results of a consumer discrimination test panel (n = 71) showed that, when added to a sausage system, APP causes a sensory difference of similar size as skatole while the methodology chosen affects the effect size: tetrad tests proved to be more sensitive than duo trio difference tests, in the tetrad test a sensory difference expressed as d' (d-prime) of 1.0 was reached. (4) a hedonic consumer test (n = 121) finally revealed that APP decreased consumer liking of the APP-spiked sausage - even to a stronger extent than skatole. APP caused significant drops in smell, taste, mouth-feel, after-taste and overall liking in Lyoner. Overall the findings suggest that, in the context of pork meat, AAP is of similar olfactory importance as skatole.

Modulation of the porcine intestinal microbiota in the course of Ascaris suum infection.

BACKGROUND: The porcine roundworm Ascaris suum impairs feed conversion and weight gain, but its effects on intestinal microbiota remain largely unexplored. METHODS: Modulation of the intestinal microbiota was assessed in pigs that were infected once with 10,000 A. suum eggs and pigs that received a trickle infection (1000 eggs/day over 10 days), compared with a non-infected control group. Six pigs each were sacrificed per group at days 21, 35 and 49 post-infection (p.i.). Faecal samples taken weekly until slaughter and ingesta samples from different intestinal compartments were subjected to next-generation sequencing of the bacterial 16S rRNA gene. RESULTS: The results revealed marked differences between the single- and the trickle-infected group. Single infection caused a remarkable but transient decrease in microbial diversity in the caecum, which was not observed in the trickle-infected group. However, an increase in short-chain fatty acid-producing genera in the caecum on day 21 p.i., which shifted to a decrease on day 35 p.i., was common to both groups, possibly related to changes in excretory-secretory products following the parasite's final moult. Faecal microbial interaction networks were more similar between the single-infected and control group than the trickle-infected group. In addition, a lower degree of similarity over time indicated that A. suum trickle infection prevented microbiota stabilization. CONCLUSIONS: These different patterns may have important implications regarding the comparability of experimental infections with natural scenarios characterized by continuous exposure, and should be confirmed by further studies.

Sexual Dimorphism of Metabolite Profiles in Pigs Depends on the Genetic Background.

The study aimed to investigate possible systematic effects in the basic underlying variability of individual metabolomic data. In this context, the extent of gender- and genotype-dependent differences reflected in the metabolic composition of three tissues in fattening pigs was determined. The 40 pigs belonged to the genotypes PIx(LWxGL) and PIxGL with gilts and boars, respectively. Blood and tissue samples from M. longissimus dorsi and liver were directly taken at the slaughtering plant and directed to GC × GC qMS metabolite analysis. Differences were observed for various metabolite classes like amino acids, fatty acids, sugars, or organic acids. Gender-specific differences were much more pronounced than genotype-related differences, which could be due to the close genetic relation of the fattening pigs. However, the metabolic dimorphism between gilts and boars was found to be genotype-dependent, and vice versa metabolic differences between genotypes were found to be gender-dependent. Most interestingly, integration into metabolic pathways revealed different patterns for carbon (C) and nitrogen (N) usage in boars and gilts. We suppose a stronger N-recycling and increased energy metabolism in boars, whereas, in gilts, more N is presumably excreted and remaining carbon skeletons channeled into lipogenesis. Associations of metabolites to meat quality factors confirmed the applicability of metabolomics approaches for a better understanding about the impact of drivers (e.g., gender, age, breed) on physiological processes influencing meat quality. Due to the huge complexity of the drivers-traits-network, the derivation of independent biomarkers for meat quality prediction will hardly be possible.

High-pressure processing of meat: Molecular impacts and industrial applications.

High-pressure processing (HPP) has been the most adopted nonthermal processing technology in the food industry with a current ever-growing implementation, and meat products represent about a quarter of the HPP foods. The intensive research conducted in the last decades has described the molecular impacts of HPP on microorganisms and endogenous meat components such as structural proteins, enzyme activities, myoglobin and meat color chemistry, and lipids, resulting in the characterization of the mechanisms responsible for most of the texture, color, and oxidative changes observed when meat is submitted to HPP. These molecular mechanisms with major effect on the safety and quality of muscle foods are comprehensively reviewed. The understanding of the high pressure-induced molecular impacts has permitted a directed use of the HPP technology, and nowadays, HPP is applied as a cold pasteurization method to inactive vegetative spoilage and pathogenic microorganisms in ready-to-eat cold cuts and to extend shelf life, allowing the reduction of food waste and the gain of market boundaries in a globalized economy. Yet, other applications of HPP have been explored in detail, namely, its use for meat tenderization and for structure formation in the manufacturing of processed meats, though these two practices have scarcely been taken up by industry. This review condenses the most pertinent-related knowledge that can unlock the utilization of these two mainstream transformation processes of meat and facilitate the development of healthier clean label processed meats and a rapid method for achieving sous vide tenderness. Finally, scientific and technological challenges still to be overcome are discussed in order to leverage the development of innovative applications using HPP technology for the future meat industry.

Production of dry-cured formed ham with different concentrations of microbial transglutaminase: Mass spectrometric analysis and sensory evaluation.

Dry-cured formed hams were produced with different concentrations of microbial transglutaminase (TG; 0.05, 0.1, 0.2, 0.5, and 0.8% Activa PB) and glucono-delta-lactone as control. A sensory evaluation was performed during a 43-day storage to determine cohesion, cavities, and local separation of dry-cured formed ham. Rising TG concentrations resulted in a slight increase in the evaluation of all sensory parameters, whereas amounts of TG higher than 0.5% led to an only very minor improvement. Dry-cured formed ham samples were analyzed by a sensitive HPLC-MS/MS method for the detection of TG using five tryptic marker peptides. Even very small amounts of Activa PB (0.05%) were detectable unambiguously. A decrease of TG detectability during the storage time of dry-cured formed ham was not observed. Using four marker peptides, no false-positive or -negative results were obtained. The amounts of two marker peptides were calculated using isotope-labeled peptides. They showed high correlations to the amount of Activa PB (R2>0.995).

Localized lipid autoxidation initiated by two-photon irradiation within single oil droplets in oil-in-water emulsions.

The initiation of lipid autoxidation within single oil droplets in Tween-20-stabilized oil-in-water emulsion was achieved by highly focused two-photon (2P) irradiation at excitation wavelength (λex) 700 nm. The radical formation was enhanced by inclusion of the photo-cleavable radical initiator di-tert-butyl peroxide (DTBP) into the droplets, and demonstrated with confocal microscopy using radical-sensitive probe BODIPY(665/676). The radical chain reactions progressed up to 60 µm; however, there were no indications of oxidation in neighboring droplets demonstrating that radicals and oxidized probe molecules were not able to migrate between oil droplets. In addition, the spatial propagation of lipid autoxidation increased with the degree of oil unsaturation.

Evidence for transfer of radicals between oil-in-water emulsion droplets as detected by the probe (E,E)-3,5-bis(4-phenyl-1,3-butadienyl)-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene, BODIPY(665/676.).

(E,E)-3,5-Bis(4-phenyl-1,3-butadienyl)-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene, BODIPY(665/676), is a lipophilic radical-sensitive fluorescent probe that can be used to study radical-driven lipid autoxidation. The sensitivity of BODIPY(665/676) was studied in the presence of radical initiators di-tert-butyl peroxide and 2,2'-azobis(2,4-dimethyl)valeronitrile (AMVN). In both cases the fluorescence of BODIPY(665/676) changed more in saturated medium-chain triglyceride oil than in linseed or sunflower oils, where the high degree of unsaturation is expected to give more pronounced radical-derived lipid oxidation. It was suggested that BODIPY(665/676), as the only available oxidizable substance in the saturated oil, was directly attacked by radicals, resulting in high rates of probe oxidation, while in the unsaturated oils, radicals attacked either unsaturated fatty acids or BODIPY(665/676), resulting in lower rates of probe oxidation. Confocal microscopy studies with BODIPY(665/676) as a radical-sensitive probe combined with oxygen consumption measurements of mixtures of oil-in-water emulsions showed that radicals could be transferred between oil droplets and thereby spread radical-driven oxidation between neighboring droplets.

Detection of radicals in single droplets of oil-in-water emulsions with the lipophilic fluorescent probe BODIPY(665/676) and confocal laser scanning microscopy.

Lipid oxidation is a widespread phenomenon in foods and other systems of biological origin. Detection methods for early stages of lipid oxidation are in demand to understand the progress of oxidation in space and time. The fluorescence spectrum of the nonpolar fluorescent probe BODIPY(665/676) changes upon reacting with peroxyl radicals originating from 2,2'-azobis(2,4-dimethyl)valeronitrile and tert-butoxyl radicals generated from di-tert-butylperoxide. The excitation wavelength of the main peak of BODIPY(665/676) was 675 nm in the fluorometer, and 670 nm under the microscope, and the optimum excitation wavelength for the secondary peak of BODIPY(665/676) was 580 nm. Advantages of using BODIPY(665/676) are fewer problems with autofluorescence and the possibility of combining several fluorescent probes that are excited and emitted at lower wavelengths. However, because of the spectrum of the probe, specific lasers and detectors are needed for optimal imaging under the microscope. Furthermore, BODIPY(665/676) is resistant to photobleaching at both excitation wavelengths, 670 and 580 nm. In diffusion studies, BODIPY(665/676) is highly lipophilic, remaining in the lipid phase and not diffusing into the aqueous phase or between lipid droplets.

Oxidative stabilization of mixed mayonnaises made with linseed oil and saturated medium-chain triglyceride oil.

Mayonnaises, made with either saturated medium chain triglyceride (MCT) oil or unsaturated purified linseed oil (LSO), were mixed. Raman confocal microspectrometry demonstrated that lipid droplets in mixed mayonnaise remained intact containing either MCT oil or LSO. Peroxide formation during storage was lower in mixed mayonnaise compared to LSO mayonnaise, while in mixed oil mayonnaise the level of peroxides was constantly low. Mixed oil mayonnaise had a lower rate of oxygen consumption than mixed mayonnaise, LSO mayonnaise having the highest rate. The decay of water-soluble nitroxyl radicals showed radicals are formed in the aqueous phase with the same rate independent of the lipids. This was also reflected in decay of α-tocopherol during storage being similar in MCT and LSO mayonnaises, but being stable in mixed oil mayonnaise and mixed mayonnaise. Results suggest that other effects than simply diluting unsaturated triglycerides with saturated triglycerides is causing the oxidative stabilization observed for mixed mayonnaise and mixed oil mayonnaise.

Investigation of oxidation in freeze-dried membranes using the fluorescent probe C11-BODIPY(581/591).

Incorporation of the fluorescent probe C11-BODIPY(581/591) in two dried membrane systems, soy bean phosphatidylcholine liposomes freeze-dried in a carbohydrate/protein matrix and Lactobacillus acidophilus (La-5) freeze-dried in a carbohydrate matrix, was successful and could be visualised by Confocal Laser Scanning Microscopy (CLSM). The C11-BODIPY(581/591) probe is a lipid oxidation reporter molecule, which is known to associate with the lipids of biological membranes and exhibit a fluorescence shift from the red range to the green range of the visible spectrum when it is oxidised together with the lipids. The present study is the first to demonstrate that the C11-BODIPY(581/591) probe can be used in dried membrane systems, and that a detection of oxidation is possible by CLSM analysis directly on the dried samples.

Muscle contraction and force: the importance of an ancillary network, nutrient supply and waste removal.

Muscle contraction studies often focus solely on myofibres and the proteins known to be involved in the processes of sarcomere shortening and cross-bridge cycling, but skeletal muscle also comprises a very elaborate ancillary network of capillaries, which not only play a vital role in terms of nutrient delivery and waste product removal, but are also tethered to surrounding fibres by collagen "wires". This paper therefore addresses aspects of the ancillary network of skeletal muscle at both a microscopic and functional level in order to better understand its role holistically as a considerable contributor to force transfer within muscular tissue.

Homogenization conditions affect the oxidative stability of fish oil enriched milk emulsions: oxidation linked to changes in protein composition at the oil-water interface.

Fish oil was incorporated into milk under different homogenization temperatures (50 and 72 degrees C) and pressures (5, 15, and 22.5 MPa). Subsequently, the oxidative stability of the milk and changes in the protein composition of the milk fat globule membrane (MFGM) were examined. Results showed that high pressure and high temperature (72 degrees C and 22.5 MPa) resulted in less lipid oxidation, whereas low pressure and low temperature (50 degrees C and 5 MPa) resulted in faster lipid oxidation. Analysis of protein oxidation indicated that especially casein was prone to oxidation. The level of free thiol groups was increased by high temperature (72 degrees C) and with increasing pressure. Furthermore, SDS-PAGE and confocal laser scanning microscopy (CLSM) indicated that high temperature resulted in an increase in beta-lactoglobulin adsorbed at the oil-water interface. This was even more pronounced with higher pressure. Less casein seemed to be present at the oil-water interface with increasing pressure. Overall, the results indicated that a combination of more beta-lactoglobulin and less casein at the oil-water interface gave the most stable emulsions with respect to lipid oxidation.