Intermediate pH Research Articles

From Beer to Cheese: Characterization of Caseinolytic and Milk-Clotting Activities of Proteases Derived from Brewer’s Spent Grain (BSG)

This study explores the extraction and characterization of proteolytic enzymes from brewer’s spent grain (BSG) and their potential as sustainable coagulants in the dairy industry. BSG samples from various beer types (Blonde Ale, IPA, Kölsch, Honey, and Porter) were obtained from two artisanal breweries in Mar del Plata, Argentina. Optimization of caseinolytic activity (CA) and protein extraction was conducted using a Plackett–Burman design, followed by a Box–Behnken design. Optimal protein concentration was achieved at intermediate pH and high temperature, while CA peaked at pH 8.0. The specific caseinolytic activity (SCA) varied among the extracts, with BSG3 showing the highest activity (99.6 U mg−1) and BSG1 the lowest (60.4 U mg−1). Protease inhibitor assays suggested the presence of aspartic, serine, metallo, and cysteine proteases. BSG3 and BSG4 showed the highest hydrolysis rates for α-casein (70% and 78%). For κ-casein, BSG1, BSG2, and BSG3 demonstrated moderate activity (56.5%, 49%, and 55.8), while BSG4 and BSG5 exhibited the lowest activity. Additionally, the milk-clotting activity (MCA) of BSG extracts was comparable to plant-based coagulants like Cynara cardunculus and Ficus carica. These findings highlight the potential of BSG-derived proteases as alternative coagulants for cheese production, offering a sustainable link between the brewing and dairy industries.

Unraveling the physiochemical characteristics and molecular insights of Zein protein through structural modeling and conformational dynamics: a synergistic approach between machine learning and molecular dynamics simulations

This research article presents a comprehensive investigation into the three-dimensional structure, physicochemical characteristics and conformational stability of the Zein protein. Machine learning (ML) based homology modeling approach, was employed to predict the 3D structure of Zein protein. Convolutional neural networks (CNNs) were utilized for refining the model, capturing complex spatial features and improving decoy refinement. The predicted 3D structure of Zein protein showed a high-confidence score, i.e. C-score of 0.96. Physiochemical characteristic was also analyzed to investigate its protonation and deprotonation behavior across a range of pH values. A comprehensive analysis of the titration curve and electrostatic charges was performed to uncover valuable molecular insights into the zein protein’s charge distribution, electrostatic interactions and potential conformational changes. Molecular dynamics (MD) simulations were performed to analyze the zein structural behavior under different pH values (2.0, 4.5, 6.8, 10.0 and 12.5), ionic strengths (0 mM, 25 mM, 50 mM, 75 mM, 100 mM) and temperatures (300K, 350K, 375K). Our results demonstrated the influence of these factors on zein protein’s stability and conformational dynamics. At extreme pH values of 2.0 and 12.5, the Zein protein exhibited increased structural deviations and potential unfolding, while intermediate pH values closer to the protein’s isoelectric point (pI) demonstrated more compact and stable conformations. Analysis of root mean square deviation, radius of gyration, solvent accessible surface area and Ramachandran plot provided clear understandings of the protein’s compactness and surface exposure, confirming the impact of pH, ionic strength and temperature on the protein’s conformation.

Influence of Environmental Factors and Epiphytic Bacteria on Arsenic Accumulation and Biotransformation in Hydrilla verticillata (L.f.) Royle

Submerged aquatic plants have potential applications in the phytoremediation of aquatic environments contaminated with arsenic (As). However, the role of epiphytic bacteria that grow on the surface of plants in As uptake and metabolism in plants has often been overlooked. An orthogonal experimental design with nine treatments, four factors, and three levels was conducted to inspect the effects of nitrogen (N, KNO3, 2, 4, 10 mg/L), phosphorus (P, NaH2PO4·2H2O, 0.02, 0.2, 1 mg/L), pH (6, 7, 9), and arsenate (As(V), Na3AsO4·12H2O, 15, 75, 375 μg/L) on As accumulation and biotransformation in sterilized plants and to further explore the role of epiphytic bacteria in the metabolism of As by Hydrilla verticillata (L.f.) Royle. The results indicate that low N, intermediate P, and intermediate pH were beneficial for As accumulation (117.2 ± 62.2 μg/g DW) in sterilized plants, and epiphytic bacteria exhibited promotion (68%) in plants. High N promoted As absorption and transformation in non-sterilized plants but reduced As absorption in sterilized plants. Epiphytic bacteria in the medium showed significant As(III) oxidation, which was affected by environmental factors. These findings can promote remediation efficiency by regulating environmental factors for the phytoremediation of As-contaminated waters.

On the mechanism for work function change of gold electrodes by ultrathin polyethyleneimine (PEI) films: Effect of molecular order.

Polyethyleneimine (PEI) is a widely used cationic polyelectrolyte. In organic electronics, it is a universal surface modifier for shifting the electrode work function (Φ) and improving charge injection into electronic devices. This effect may depend on the conformation and dipolar order of the PEI ultrathin film, but their detailed experimental evaluation has not yet been reported. Thus, we used sum-frequency generation (SFG) spectroscopy to probe the net orientation of polar groups of PEI films on glass and gold. The films were fabricated by spin-coating from alcoholic solutions or by dip-coating from aqueous solutions of various pH values, with both branched (b-PEI) and linear (l-PEI) structures. The obtained SFG spectra and atomic force microscopy (AFM) images indicated that the conformational ordering of the PEI layers increases over the period of 14 days after fabrication, being slightly more pronounced for l-PEI vs b-PEI, and for dip-coating vs spin coating fabrication. Furthermore, both the pH of the dip-coating solutions and the substrate nature influence the final morphology and order of the adsorbed films. On glass, they are optimized at an intermediate pH 5, while on gold, the greatest homogeneity is observed at pH 2 and the largest dipolar order is observed at pH 10. The pH dependence of changes in the work function of gold by PEI (|ΔΦ|) suggests that the electronic contribution is dominant. Nevertheless, the evolution of the PEI dipolar ordering was accompanied by small variations of |ΔΦ|, suggesting that it does have a significant contribution, especially at conditions for which the electronic contribution is reduced.

Electrochemical Investigation of Symmetric Aminoquinones

Abstract Quinones have a wide range of valuable properties and potential applications in medicinal chemistry, materials science, optoelectronic devices, and batteries. Molecular redesign using different functional groups, like amines, can optimize their properties and prevent undesired side reactions. However, the synthesis of aminoquinones can be particularly challenging at times, and there is a need for simple and efficient routes to access these compounds without metal catalysts or halogenated starting materials. Here, we demonstrate the synthesis and electrochemical characterization of a series of aminoquinones derived from renewable sources, namely vanillin or 2-methoxyhydroquinone. We employ a series of primary and secondary amines, varying in their electronic situation as well as steric demand. Depending on the type of starting material, either the desired aminoquinone or the related Schiff-base adduct was obtained. The aminoquinones were further explored towards their stability at different pH values. At extreme pH values, the deeply colored aminoquinones decompose, accompanied by decolorization of the solutions within a few minutes (pH 14) or hours (pH 1). At intermediate pH values (3-8) the aminoquinones are stable upon storage in solution, where they feature a quasi-reversible redox chemistry and fast, diffusion limited kinetics.

Comparing methods for detection of gastro-oesophageal reflux in anaesthetized dogs

ObjectiveTo compare the sensitivity and specificity of pH with multichannel intraluminal impedance (pH-MII), pH-metry (pH) alone and MII alone to direct observation of GOR by endoscopy in anaesthetized dogs. Study designA prospective comparative trial in a live canine model. AnimalsA group of 35 (22 females, 13 males) dogs of various breeds. The mean (range) body weight and age were 31.9 (14–40) kg and 5.6 (0.75–12) years, respectively. MethodsAll dogs were premedicated with medetomidine and morphine, anaesthesia was induced with propofol and maintained on isoflurane in oxygen. A monitoring assembly consisting of an endoscopy camera, endotracheal tube and a disposable flexible pH-MII catheter was used to measure oesophageal pH, MII and directly visualize reflux. Visual reflux score was (0–3) and pH was recorded on a data capture sheet. Reflux was considered to have occurred whenever oesophageal pH was < 4.0 or > 7.5, device software analysing MII data detected fluid or a visual reflux score of 2 or 3 were assigned. Receiver operator curves (ROC) analysis was used to determine sensitivity and specificity for each monitoring method to detect GOR. ResultsEndoscopy identified GOR in 20 dogs (57%), pH-MII in 19 dogs (54%), pH alone in 13 dogs (37%) and MII alone in 12 dogs (24%). ROC analysis showed fair accuracy for pH-MII and pH alone, whereas MII demonstrated low accuracy. Conclusions and clinical relevanceIn conclusion, pH-MII is a reliable method for detecting GOR and emerges as a promising tool for future research. Endoscopy is reliable and provides the ability to subjectively quantify the volume of reflux; however, it lacks the ability to discern the pH of refluxate. pH alone misses reflux events with intermediate pH (4.1–7.4). Incorporation of impedance addresses some of the limitations associated with pH alone and enhances diagnostic accuracy.

PH Dependence of Noble Metals Dissolution: Gold

AbstractThe electrochemical applications of gold span the entire pH spectrum. Recently, gold dissolution in acidic and alkaline media has been studied, but less attention has been given to electrolytes at intermediate pH values. To address this gap, this work uses on‐line electrochemical dissolution inductively coupled plasma mass spectrometry (ICP‐MS) to examine gold dissolution across a pH range of 1 to 12.7 using phosphate buffer solutions. All experimental parameters, except pH, are kept constant, enabling a clear investigation of pH effects on anodic (gold oxidation) and cathodic (gold oxide reduction) dissolution processes. Results show that dissolution amounts are lowest at neutral pH values between 3 and 7, varying with the applied potential and exposure time. Anodic and cathodic dissolution dominate in acidic and alkaline electrolytes, respectively. Depending on the highest applied potentials and time exposure, the main dissolution mechanism shifts at pH=5, 7, and 9. The pH dependence of Au dissolution is proposed to be linked to the nature of gold oxides formed, the kinetics of oxide formation/reduction, gold ion redeposition, and the influence of the oxygen evolution reaction (OER) on dissolution. These results provide fundamental insights into gold dissolution under neutral pH conditions.

Probing the Catalyst-Ionomer Interface during Electrochemical CO2 Reduction

The catalyst-ionomer interface can significantly impact the selectivity of the electrochemical CO2 reduction (CO2R) reaction. Ionomers such as Nafion are commonly used in conjunction with nanostructured CO2R catalysts in flow cells and zero-gap devices, with their presumed function being to act as a binder for the catalyst. However, recent studies have reported that ionomers such as Nafion and Sustainion can affect the reaction rate and selectivity of CO2R, and the roles of ionomer in controlling mass transfer and local pH have been hypothesized. We employed in situ Raman spectroscopy to examine CO2R intermediate and local pH on a sputtered copper (sCu) surface with and without an ionomer overlayer. We observed a difference in the potential-dependent formation of surface CO in the presence of Nafion compared to clean sCu. Using a combination of pH-sensitive probe molecules, we also determined the pH at the catalyst-ionomer interface.

An approach for pH-independent release of poorly soluble ionizable drugs using hot-melt extrusion

Hot melt extrudates with combinations of Soluplus® and Aqoat® AS-LF or Eudragit® E PO were investigated to improve drug release and to overcome the pH-dependent release of poorly water-soluble basic (itraconazole, ITZ) and acidic (mefenamic acid, MFA) drugs. The release of ITZ was improved in both 0.1 N HCl and PBS pH 6.8 by hot-melt extrusion with combinations of Soluplus®:Aqoat® AS-LF and can be adjusted by varying the ratio of the polymers. At the ratio Soluplus®:Aqoat® AS®LF 75:25, an almost pH-independent release was achieved without any drop in the drug concentration within 24 h. A pH-independent and extended release (over 24 h) was obtained from milled extrudates when formulated in erodible matrix tablets using 15 % Methocel® K15M as the carrier. The release of MFA from extrudates with Soluplus® was immediate only in PBS pH 6.8. From extrudates with cationic Eudragit® E PO the release of MFA was slow in 0.1 N HCl and PBS pH 6.8, due to poor drug solubility and insoluble Eudragit® EPO, respectively. However, in the medium with an intermediate pH of 5.5, both MFA and Eudragit® E PO are highly ionized, and the release was fast, complete, and stable within 24 h. These release behaviors could be to some degree applicable for immediate or enteric, but not for extended-release formulations.

PH-dependent aggregation of tannic acid: Insights from molecular dynamics simulations

Colloidal fouling of polymeric membranes is still a limiting factor in the use of filtration for polyphenol recovery. In this context, understanding the self-aggregation mechanisms of tannic acid (TA) is of great importance. In this study, molecular dynamics simulations were performed to investigate the effect of pH on TA self-aggregation. The results show a non-monotonic relationship between pH and TA self-aggregation, with different mechanisms observed for different pH conditions. At an intermediate pH, the moderate deprotonation of TAs is associated with electrostatic repulsion between the molecules, resulting in the formation of aggregates composed of a small number of TAs. Then, at lower pH, fully protonated TA molecules promote the aggregation of a larger number of TAs because of the reduced electrostatic repulsion. Conversely, at higher pH, despite the increased negative charge of TAs leading to important electrostatic repulsion, the formation of cationic TA-H3O+-TA bridges favours aggregation, enhancing the number of TAs per aggregate in comparison to an intermediate pH. Finally, analysis of the size and density of the aggregates shows that at higher pH less dense aggregates are formed, because of repulsion between molecules, resulting in colloid particles of larger size compared to aggregates formed from the same number of molecules at low pH. These results provide valuable insights into the pH-dependent mechanisms of TA self-aggregation, which are crucial for adjusting operating conditions to control membrane fouling and for designing effective filtration processes.

Lipid shape and packing are key for optimal design of pH-sensitive mRNA lipid nanoparticles

The ionizable-lipid component of RNA-containing nanoparticles controls the pH-dependent behavior necessary for an efficient delivery of the cargo-the so-called endosomal escape. However, it is still an empirical exercise to identify optimally performing lipids. Here, we study two well-known ionizable lipids, DLin-MC3-DMA and DLin-DMA using a combination of experiments, multiscale computer simulations, and electrostatic theory. All-atom molecular dynamics simulations, and experimentally measured polar headgroup pKa values, are used to develop a coarse-grained representation of the lipids, which enables the investigation of the pH-dependent behavior of lipid nanoparticles (LNPs) through Monte Carlo simulations, in the absence and presence of RNA molecules. Our results show that the charge state of the lipids is determined by the interplay between lipid shape and headgroup chemistry, providing an explanation for the similar pH-dependent ionization state observed for lipids with headgroup pKa values about one-pH-unit apart. The pH dependence of lipid ionization is significantly influenced by the presence of RNA, whereby charge neutrality is achieved by imparting a finite and constant charge per lipid at intermediate pH values. The simulation results are experimentally supported by measurements of α-carbon 13C-NMR chemical shifts for eGFP mRNA LNPs of both DLin-MC3-DMA and DLin-DMA at various pH conditions. Further, we evaluate the applicability of a mean-field Poisson-Boltzmann theory to capture these phenomena.

Assessment of beef sensory attributes and physicochemical characteristics: A comparative study of intermediate versus normal ultimate pH striploin cuts

The quality of beef, defined by key attributes such as the intrinsic sensory qualities texture, flavour, and juiciness, is shaped by various intrinsic and extrinsic factors. This study conducted a detailed examination of Nellore beef, focusing on two categories based on ultimate pH (pHu) levels: intermediate (pHu ≥ 5.8) and normal (pHu < 5.6) beef. A comprehensive approach was taken, involving twenty trained assessors who applied the Optimised Descriptive Profile (ODP) method to evaluate grilled striploin steak samples. In parallel, consumer preferences were measured through a hedonic test and a Check-all-that-apply (CATA) task, involving 135 participants. The ODP results revealed that the intermediate pHu samples were juicier (P < 0.05) compared to the normal pHu group. The CATA analysis highlighted differences in both intermediate and normal pHu beef, especially in juiciness, a crucial factor for consumer satisfaction. Notably, variations in deoxymyoglobin content linked to ageing were observed, with higher levels at the 3rd day compared to the 28th day, especially in the intermediate pHu samples (P < 0.05). Moreover, colour-related aspects such as L*, b*, chroma (C*), and oxymyoglobin were significantly influenced (P < 0.05) by both the pHu category and ageing time. Regarding consumer acceptance, the study found no significant difference in perception between the intermediate and normal pHu groups (P > 0.05). These findings revealed the complex interactions between pHu levels, sensory characteristics, and consumer preferences in beef quality, offering valuable insights for both the industry and research community.

Unusual Shell Morphologies of Responsive Amino Core‐Shell Microgels Induced by pH During Shell Synthesis

AbstractThe properties of pH‐responsive microgels are strongly influenced by the pH value during synthesis. In this work, based on a N‐n‐propylacrylamide (NNPAM) core with N‐3‐(dimethylamino)propylmethacrylamide (DAPMA) as a comonomer, a series of core‐shell microgels with shells from NNPAM and N‐(3‐aminopropyl)methacrylamide hydrochloride (APMH) are synthesized at different pH values. While the swelling behavior is studied with temperature‐ and angle‐dependent photon correlation spectroscopy (PCS), the size and morphology are also investigated by means of atomic force microscopy (AFM) and static light scattering (SLS). At acidic pH, rather monodisperse microgels with a very fuzzy shell are obtained. The microgels evolve particulate structures on their shell at intermediate pH until not only a core‐shell microgel but also a secondary microgel species is produced at basic pH. By altering the synthesis pH, it is possible to influence the morphology of core‐shell microgels to suit future applications like the uptake and release of drugs or surface modification.

Selective oxidation of cyclohexane over nanostructured manganese tungstate: Contribution of Mn and W related sites

Nanostructured MnWO4 catalysts prepared with different initial pH exhibited systematic variation in the activity in the selective oxidation of cyclohexane. 2-propanol TPD showed that the ratio of Mn to W related sites increased with the initial synthesis pH. W sites were found to be mainly active in the formation of CHHP and dehydrogenation of cyclohexanol, while Mn sites appeared to be more active in decomposition of CHHP and deep oxidation, giving a significant selectivity to adipic acid. The high yield of KA oil at intermediate synthesis pH suggests an optimum balance of Mn and W surface sites.

The Influence of pH Dynamics on Modeled Ammonia Emission Patterns of a Naturally Ventilated Dairy Cattle Building

Ammonia emission rates from naturally ventilated livestock housing systems can be estimated in multiple ways. By coupling different modeling approaches towards a semi-mechanistic barn-scale ammonia emission model, we investigated the influence of urine puddle pH dynamics on the (sub)daily and seasonal pattern of ammonia emissions. We compared the simulated ammonia emission patterns using about ten months of on-farm measurements obtained from a naturally ventilated dairy cattle building with a scraped solid floor in Northern Germany. The dataset included gas concentration measurements as well as wind data (ranging from 0 m s−1 to about 8.6 m s−1) and air temperature data (ranging from about −4 ∘C to about 32 ∘C), the average number of housed cows (about 380) and information on the average cow mass (about 700 kg). In addition, the average dry matter intake, total gross energy intake and nitrogen intake were used to model the ammonia emission potential. In the emission modeling, we considered two potential types of pH dynamics in the urine puddles: a saturating scenario and a peaking scenario. For both of them, 21 different combinations of initial pH and maximum pH were considered within a range of 6.5 to 11. We showed that the non-linear interaction of the puddle pH and temperature caused specific emission patterns, where the degree of influence of the two parameters changed over the course of the emission process. Low initial pH values together with high asymptotic pH values were associated with the largest emissions. Considering the same asymptotic pH value, the higher the initial pH value, the lower the observed emissions; especially when assuming peak pH dynamics, the emission values were significantly lower. In natural pH settings (i.e., low to intermediate initial pH and intermediate asymptotic pH), the winter emissions were considerably lower than the summer emissions (i.e., the winter emission was about half of the summer emission, as observed in the on-farm studies). In contrast, artificial pH settings with high pH values led to markedly lower emissions in the summer (i.e., the summer emission was about the same as winter emission), reducing the total annual emission value. Our sensitivity study indicated that the urine puddle alkalizing dynamics play a key role in the overall emission model accuracy in order to capture seasonal and diurnal variability of the ammonia emission of naturally ventilated dairy cattle barns in mechanistic modeling approaches. Thus, future studies should investigate the range of pH dynamics that naturally occur in urine puddles in cattle barns depending on the flooring material, the entry of litter or feed leftovers, the cleaning and cooling system (e.g., in terms of use of water) and so on in order to further refine the emission model.

Simultaneous modulation of CHO cell cytotoxicity, turbidity, and DOC by coagulation with or without pre-oxidation in water from the Pearl River Delta region, China

Coagulation with or without pre-oxidation are important drinking water treatment processes. However, the efficacy of these processes in mitigating water toxicity remains unknown. To further improve drinking water safety, we employed water from the Pearl River Delta region of southern China to investigate a treatment approach consisting of coagulation with or without pre-oxidation to simultaneously modulate health-relevant cytotoxicity to CHO cells, on top of the conventional foci of turbidity and dissolved organic carbon (DOC) during water treatment. Three coagulants (two aluminum-based and one iron-based salts) and three pre-oxidants (ozone, permanganate, and peroxymonosulfate) were studied. For coagulation without pre-oxidation, intermediate coagulant doses and pH reached optimum cytotoxicity to CHO cells, turbidity, and DOC control simultaneously. Introducing oxidants reduced cytotoxicity to CHO cells significantly, enhanced by increasing oxidant concentrations and pre-oxidation duration. The cytotoxicity to CHO cells mitigation capabilities of three pre-oxidants were: ozone > peroxymonosulfate > potassium permanganate. Modulation of water cytotoxicity to CHO cells was mostly attributable to controlling DOC (specifically humic-acid like substances, tyrosine, tryptophan). However, the addition of pre-oxidants led to significant shifts in water cytotoxicity to CHO cells forcing drivers, rendering humic-acid like substances the sole decisive cytotoxicity-inducing fluorophores. For the first time, ‘sweet spots’ were identified to simultaneously monitor cytotoxicity to CHO cells alongside turbidity and DOC. These methods better modulate water cytotoxicity to CHO cells without sacrificing conventional water treatment goals while shedding light onto the mechanisms behind.

The Effects of Lithium Ions and pH on the Function of Polyacrylic Acid Binder for Silicon Anodes

Binder plays a critical role in the performance of silicon anodes for lithium-ion batteries, specifically by connecting particles of active material and promoting adhesion to the current collector. Recent studies have differed on the relative cycle life of silicon anodes made from water-based polyacrylic acid (PAA) vs LiOH-PAA binders. Differences between the two may be due to the pH value or the extra Li+ in the binder, both of which change when LiOH is added to PAA. Here we investigate the impact of these two variables on the performance of silicon anodes. Regarding the effect of Li+, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results confirm our hypothesis that the extra Li+ facilitates ion transport. Regarding pH, we find that high pH in binders is detrimental to the electrode mechanical integrity, as observed in peeling tests and cross-sectional imaging. However, viscosity tests reveal that increased pH benefits the coating and mixing process. Our cycling results show that LiOH-PAA binder maintains greater cell capacity than does PAA, and further that LiOH-PAA at pH 4.5 leads to a cell with the highest capacity. Therefore, an intermediate pH is an optimal compromise between benefits observed for the low and high pH experiments.

The effect of age and sex on carcass traits and body composition of Hungarian yearling farmed red deer (Cervus elaphus hippelaphus)

Carcass characteristics were studied in 80 young Hungarian red deer in different ages (12, 15, 18 and 20 months of age). In all age group 10 male and 10 female were slaughtered. The dressed carcass weight in skin varied between 53.72 and 65.66% of live weight. The first class lean meat varied between 14.3 and 16.6% of live weight.The live weight, carcass weight increased with the age and differed also between sexes. The highest dressing percentages were found at 20 months of age in both sexes (♂: 65.7%, ♀: 62.5%). Mainly the hinds had higher loin, leg and shoulder proportions of carcass at 20 months of age than the stags.The carcass muscle, bone and fat content were measured by computer tomography. These traits were grown and their proportion changed with the age. The bone to muscle ratio gradually decreased with the age while the fat to muscle ratio increased after 15 months of age (♂: from 0.13 to 0.17, ♀: from 0.15 to 0.18). At 18 month of age the hinds had higher bone to muscle and fat to muscle ratio than the stags'.The fat percentage of carcasses increased with the age in both sexes (♂: from 8.01% to 11.04%, ♀: from 8.40% to 11.28%). The hinds had higher values than the stags but it was significant just at 20 months of age.From the meat quality attributes there were found differences between ages in the case of pH, lightness, drip loss, cooking loss and shear force. The highest pH was found at 12 months of age in both sexes. There were found 5% intermediate pH (6.2 < pH < 5.8) at 12 and 15 months of age, all of them were male. The highest lightness values were observed at 18 months of age in both sexes (♂: 13.47, ♀: 14.90). There were differences between sexes in pH at all ages, except 15 months of age, and at 18 months of age in redness and lightness.Based on our results, the optimal slaughtering time for Hungarian red deer is 20 months of age, because this is when the dressing percentage is the best for both sexes. Meat quality traits changed with age, and gender differences sexes were the most pronounced for these traits at 18 months of age.

Interplay of egg white gel pH and intragastric pH: Impact on breakdown kinetics and mass transport processes

Egg white gels have been utilized as a model system to study protein breakdown kinetics based on physical and biochemical breakdown processes during in vitro gastric digestion. Additionally, the impact of regulating intragastric pH on the breakdown kinetic processes was investigated. The present study evaluated the impact of gel pH (based on the pH of protein dispersion prepared at pH 3, 5 and 7.5) and intragastric pH regulation (with or without adjustment to pH 2 during in vitro gastric digestion) on the effective diffusion of gastric juice components (water and HCl), gel softening kinetics during gastric digestion, microstructural analysis using micro- computed tomography and protein hydrolysis in the liquid and solid fraction of egg white gel digesta. Egg white gels were subjected to 30 s oral digestion and 15, 30, 60, 120, 180 or 240 min gastric digestion in a static in vitro gastric digestion model, with or without gastric pH adjustment to pH 2. The gel pH affected all the properties measured during gastric digestion and each gel pH represented a specific driving mechanism for protein breakdown. A lower gel pH (pH 3) demonstrated a higher diffusion of moisture and acid, resulting in faster softening (p < 0.05). An intermediate pH (pH 5) showed greater protein–protein interactions due to the proximity to the isoelectric point of egg white proteins, resulting in very slow softening during digestion (p < 0.05), and a higher pH (pH 7) resulted in higher acid diffusion, intermediate gel hardness and very slow softening kinetics (p < 0.05). The gastric pH adjustment during digestion of egg protein gels affected (p < 0.05) the equilibrium moisture and acid contents as well as protein hydrolysis. The study confirmed that there is an interplay between initial gel pH and the intragastric pH which affected the breakdown kinetics of egg white gels during the gastric digestion process.

Buffer Solutions of known Ionic Strength

pH buffer solutions are those in which minimal pH variations occur when moderate amounts of strong acids or bases are added or diluted. The most common buffers are those used in the intermediate pH zone and are made up of an acid-base conjugate pair (HA/A-), with Ca and Cb as analytical concentrations of acid and base respectively. The buffer capacity of a solution is the measure of its effectiveness in preserving the pH value when adding an acid or a base. Three new programs working under the Windows 10 environment have been developed. The first one, the BUFFER program, allows to prepare buffers of known ionic strength without the need of adding an inert electrolyte, calculating the pH and buffering capacity. On the other hand, the BRÖMSTED method allows calculating the pH of conjugated acid-base systems applying the Newton-Raphson method. In this work two more programs are described, one applying the Brömsted method to monoprotic acids and another new one to diprotic acids.