Precipitation pH Research Articles

Physicochemical and functional characteristics of a gourd (Cucurbita argyrosperma Huber) seed protein isolate subjected to high-intensity ultrasound

The impact of high-intensity ultrasound (HIU, 20 kHz) on the physicochemical and functional characteristics of gourd seed protein isolate (GoSPI) was studied. GoSPI was prepared from oil-free gourd seed flour through alkaline extraction (pH 11) and subsequent isoelectric precipitation (pH 4). The crude protein concentration of GoSPI ranged from 91.56 ± 0.17 % to 95.43 ± 0.18 %. Aqueous suspensions of GoSPI (1:3.5 w/v) were ultrasonicated at powers of 200, 400, and 600 W for 15 and 30 min. Glutelins (76.18 ± 0.15 %) were the major protein fraction in GoSPI. HIU decreased the moisture, ash, ether extract, and nitrogen-free extract contents and the hue angle, available water and a* and b* color parameters of the GoSPI in some treatments. The L* color parameter increased (7.70 %) after ultrasonication. HIU reduced the bulk density (52.63 %) and particle diameter (39.45 %), as confirmed by scanning electron microscopy, indicating that ultrasonication dissociated macromolecular aggregates in GoSPI. These structural changes enhanced the oil retention capacity and foam stability by up to 62.60 and 6.84 %, respectively, while the increases in the solvability, water retention capacity, and emulsifying activity index of GoSPI were 90.10, 19.80, and 43.34 %, respectively. The gelation, foaming capacity, and stability index of the emulsion showed no improvement due to HIU. HIU altered the secondary structure of GoSPI by decreasing the content of α-helices (49.66 %) and increasing the content of β-sheets (52.00 %) and β-turns (65.00 %). The electrophoretic profile of the GoSPI was not changed by HIU. The ultrasonicated GoSPI had greater functional attributes than those of the control GoSPI and could therefore be used as a functional food component.

The Influence of Substrate and Strain on Protein Quality of Pleurotus ostreatus

Background: The effect of substrate and strain on the nutritional and functional properties of mushroom flours and protein concentrates (PCs) has not thoroughly been investigated. Methods: The proteins of P. ostreatus flours (strains AMRL144 and 150) were isolated following alkaline extraction (pH 12) and isoelectric precipitation (pH 4) as it was determined by the solubility curves. The protein quality of the flours and PCs were evaluated by determining the protein solubility index (PSI) and their functional properties, such as water (WAC) and oil absorption capacity (OAC), foam capacity (FC), foam stability (FS) and emulsion stability (ES). The amino acid (AA) composition of the flours was determined by reversed-phase liquid chromatography after protein hydrolysis and o-phthalaldehyde derivatization. Results: The PSIs of the flours and PCs of P. ostreatus were comparable to those of soy protein flours and protein concentrates. The highest AA concentration was found for both strains when cultivated on the barley and oat straw (BOS) substrate, showing a similar trend as the protein content. A principal component analysis (PCA) indicated an impact of the strain on the functional properties. Conclusions: Both strains can produce high quality proteins especially when cultivated on wheat straw (WS). The FS was positively correlated with the P. ostreatus strain AMRL150 whereas the FC was positively correlated with AMRL144.

Ion Exchange Processes for CO2 Mineralization Using Industrial Waste Streams: Pilot Plant Demonstration and Life Cycle Assessment

AbstractAn attractive technique for removing CO2 from the environment is sequestration within stable carbonate solids (e. g., calcite). However, continuous addition of alkalinity is required to achieve favorable conditions for carbonate precipitation (pH>8) from aqueous streams containing dissolved CO2 (pH<4.5) and Ca2+ ions. In this study, a pH‐swing process using ion exchange was demonstrated to process 300 L of produced water brine per day for CO2 mineralization. Proton titration capacities were quantified for aqueous streams in equilibrium with gas streams at various concentrations of CO2 (pCO2=0.03–0.20 atm) and at various flow rates (0.5–2.0 L min−1). Energy intensities for the process were determined to be between 30 and 65 kWh per tonne of CO2 sequestered depending on the composition of the brine stream. A life cycle assessment was performed to analyze the net carbon emissions of the technology which indicated a net CO2 reduction for pCO2≥0.12 atm (−0.06–−0.39 kg CO2e per kg precipitated CaCO3) utilizing calcium‐rich brines. The results from this study indicate the ion exchange process can be used as a scalable method to provide alkalinity necessary for the capture and storage of CO2 in Ca‐rich waste streams.

The effect of ultrasound on the extraction and foaming properties of proteins from potato trimmings

High-intensity ultrasonication is an emerging technology for plant protein isolation and modification. In this study, the potential of temperature-controlled ultrasonication to enhance the recovery of functional proteins from potato trimmings was assessed. Different ultrasound energy levels [2000–40,000 J/g fresh weight (FW)] were applied during protein extraction at pH 9.0. True protein yields after ultrasonication significantly increased (up to 91%) compared to conventional extraction (33%). Microstructural analysis of the extraction residues showed more disrupted cells as ultrasonication time increased. Ultrasound treatments (10,000 and 20,000 J/g FW) increased the protein yield without affecting the foaming and air-water interfacial properties of protein isolates obtained after isoelectric precipitation (pH 4.0). However, proteins obtained after extended ultrasonication (40,000 J/g FW) had significantly slower early-stage adsorption kinetics. This was attributed to ultrasound-induced aggregation of the protease inhibitor fraction. In conclusion, ultrasonication shows potential to help overcome some challenges associated with plant protein extraction.

Selective removal of Fe(Ⅲ) from HNO3 leach liquor of saprolitic laterite ore: Precipitation efficiency, hydrolysis mechanism, and removal strategy

HNO3 leach liquor of saprolitic laterite ore contains Fe3+, Al3+, Sc3+, Ni2+, Co2+, Mg2+, etc. Efficient removal of Fe3+ while reducing the loss of valuable metals is the key to solution purification. In this paper, a detailed study was carried out on the removal of Fe3+ by hydrolysis precipitation. First, thermodynamic calculations were conducted to analyze the precipitation pH changes and possible hydrolysis products at different temperatures. Subsequently, the experimental results show that more than 99 % Fe can be removed via low-temperature hydrolysis at 25–80 ℃ and pH = 3.0–3.5, but over 40 % Al and 30 % Sc also precipitate together, causing valuable metals losses. Differently, under high-temperature conditions (180 ℃, pH = 1.0, 0.5 h), 99.49 % of Fe can be selectively removed as Fe2O3 product, while other valuable metals hardly precipitate. It was found that the low-temperature Fe removal residue exhibits irregular agglomeration and uneven particle size, and contains 9.48 % NO3– and 25.86 % Fe. The high-temperature Fe removal residue presents a nanoscale spherical shape with uniform particle size and only contains 0.087 % NO3–, and the Fe content is up to 69.07 %. Finally, the Fe3+ hydrolysis mechanism was analyzed and an efficient Fe removal process from the HNO3 system including pH adjustment of leach liquor, selective Fe removal at high temperature, flash evaporation to recover free HNO3, and solid–liquid separation to obtain Fe2O3 products was proposed.

Isolation and Characterization of Indigenous Ureolytic Bacteria from Mindanao, Philippines: Prospects for Microbially Induced Carbonate Precipitation (MICP)

Microbially induced carbonate precipitation (MICP), a widespread phenomenon in nature, is gaining attention as a low-carbon alternative to ordinary Portland cement (OPC) in geotechnical engineering and the construction industry for sustainable development. In the Philippines, however, very few works have been conducted to isolate and identify indigenous, urease-producing (ureolytic) bacteria suitable for MICP. In this study, we isolated seven, ureolytic and potentially useful bacteria for MICP from marine sediments in Iligan City. DNA barcoding using 16s rDNA identified six of them as Pseudomonas stutzeri, Pseudomonas pseudoalcaligenes, Bacillus paralicheniformis, Bacillus altitudinis, Bacillus aryabhattai, and Stutzerimonas stutzeri but the seventh was not identified since it was a bacterial consortium. Bio-cementation assay experiments showed negligible precipitation in the control (without bacteria) at pH 7, 8, and 9. However, precipitates were formed in all seven bacterial isolates, especially between pH 7 and 8 (0.7–4 g). Among the six identified bacterial species, more extensive precipitation (2.3–4 g) and higher final pH were observed in S. stutzeri, and B. aryabhattai, which indicate better urease production and decomposition, higher CO2 generation, and more favorable CaCO3 formation. Characterization of the precipitates by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and attenuated total reflectance Fourier transform spectroscopy (ATR-FTIR) confirmed the formation of three carbonate minerals: calcite, aragonite, and vaterite. Based on these results, all six identified indigenous, ureolytic bacterial species from Iligan City are suitable for MICP provided that the pH is controlled between 7 and 8. To the best of our knowledge, this is the first report of the urease-producing ability and potential for MICP of P. stutzeri, P. pseudoalcaligenes, S. stutzeri, and B. aryabhattai.

Varying precipitation conditions allow directing the composition and physical properties of soy protein concentrates.

Soy protein concentrates (SPCs) are common food ingredients. They typically contain 65% (w/w) protein and ∼30% (w/w) carbohydrate. SPCs can be obtained with various protein precipitation conditions. A systematic study of the impact of these different protein precipitation protocols on the SPC protein composition and physical properties is still lacking. Here, SPCs were prepared via three different protocols, that is, isoelectric (pH 3.5-5.5), aqueous ethanol (50%-70% [v/v]), and Ca2+ ion (5-50mM) based precipitations, and analyzed for (protein) composition, protein thermal properties, dispersibility, and water-holding capacity. SPCs precipitated at pH 5.5 or by adding 15mM Ca2+ ions had a lower 7S/11S globulin ratio (∼0.40) than that (∼0.50) of all other SPC samples. Protein in SPCs obtained by isoelectric precipitation denatured at a significantly higher temperature than those in ethanol- or Ca2+ -precipitated SPCs. Precipitation with 50%-60% (v/v) ethanol resulted in pronounced denaturation of 2S albumin and 7S globulin fractions in SPCs. Additionally, increasing the precipitation pH from 3.5 to 5.5 and increasing the Ca2+ ion concentration from 15 to 50mM caused a strong decrease of both the dispersibility of the protein in SPC and its water-holding capacity at pH 7.0. In conclusion, this study demonstrates that the SPC production process can be directed to obtain ingredients with versatile protein physicochemical properties toward potential food applications. PRACTICAL APPLICATION: This study demonstrates that applying different protein precipitation protocols allows obtaining SPCs that vary widely in (protein) composition and physical properties (such as protein dispersibility and water-holding capacity). These varying traits can greatly influence the suitability of SPCs as functional ingredients for specific applications, such as the production of food foams, emulsions, gels, and plant-based meat alternatives. The generated knowledge may allow targeted production of SPCs for specific applications.

Predicting Cyanide Degradability and Destruction Using Artificial Neural Networks: A Case Study in West Azerbaijan, Iran”

ABSTRACT The presence of cyanide compounds in soil can lead to the formation and evaporation of hydrogen cyanide (HCN), while some of these compounds can undergo conversion by microorganisms present in the soil. However, high concentrations of cyanide can be toxic to soil microorganisms. During the gold extraction of mines, sodium cyanide (NaCN) solution is commonly used which results in a significant amount of cyanide waste that is regarded as an environmental pollutant. Previous studies have proposed physical, chemical, and biological methods to eliminate cyanide, but they have not achieved optimal efficiency. Unfortunately, the potential of artificial intelligence (AI) in this domain has been overlooked. Artificial Neural Network (ANN) models, specifically the multilayer perceptron (MLP) and simple linear regression, can significantly enhance and expedite the cyanide remediation process due to their remarkable predictive capabilities. In this study, an MLP and simple linear regression were employed to predict the biodegradation procedures of cyanide in soil. The study focused on cyanide waste generated by gold extraction factories and utilized environmental factors such as initial waste cyanide concentration, pH, soil and environmental temperature, humidity, chloride concentration, alkaline, electrical conductivity, precipitation, evaporation intensity, cyanide concentration, and initial pH as input data for the artificial neural network. The results of the MLP model revealed that electrical conductivity is the most influential factor in predicting the cyanide rate and initial pH of the waste soil. Conversely, the results of the simple linear regression indicated that the variables with the greatest impact on cyanide concentration are electrical conductivity (0.881), time (0.862), and alkalinity (0.724). By leveraging AI techniques such as ANN, this study demonstrates the potential for improved cyanide remediation. The integration of environmental factors and predictive models can contribute to more effective strategies for addressing cyanide pollution in soil.

A probe into the acid deposition mitigation path in China over the last four decades and beyond.

China currently has the highest acid deposition globally, yet research on its status, impacts, causes and controls is lacking. Here, we compiled data and calculated critical loads regarding acid deposition. The results showed that the abatement measures in China have achieved a sharp decline in the emissions of acidifying pollutants and a continuous recovery of precipitation pH, despite the drastic growth in the economy and energy consumption. However, the risk of ecological acidification and eutrophication showed no significant decrease. With similar emission reductions, the decline in areas at risk of acidification in China (7.0%) lags behind those in Europe (20%) or the USA (15%). This was because, unlike Europe and the USA, China's abatement strategies primarily target air quality improvement rather than mitigating ecological impacts. Given that the area with the risk of eutrophication induced by nitrogen deposition remained at 13% of the country even under the scenario of achieving the dual targets of air quality and carbon dioxide mitigation in 2035, we explored an enhanced ammonia abatement pathway. With a further 27% reduction in ammonia by 2035, China could largely eliminate the impacts of acid deposition. This research serves as a valuable reference for China's future acid deposition control and for other nations facing similar challenges.

Physiochemical and functional properties of Moringa oleifera protein obtained by isoelectric precipitation

The work investigated the effect of extraction pH (10 or 11) and precipitation pH (4 or 4.5) on the physicochemical and functional properties of Moringa oleifera protein. The physicochemical characteristics of Moringa leaf powder were analyzed using proximate quantification based on AOAC standard methods. The thermal, spectral, x-ray diffraction data were collected using the differential scanning calorimetric, Fourier transform infrared spectroscopy (FTIR), and wide-angle x-ray diffraction. The extraction at pH 10 and the precipitation process at pH 4.5 generated the highest protein content of 58.88%. Some of the functional properties of this pH combination were emulsion activity at 29.67%, emulsion stability at 50.45%, protein solubility at 32.36%, and water absorption capacity of 4.78 mL water/g. The thermal properties suggested the denaturation temperature of Moringa protein powder at 75°C, which was comparable to that previously reported plantbased protein isolate. FTIR and x-ray spectra argued the domination of amorphous protein fraction with a trace of lipid and carbohydrate. With these characteristics, protein has great potential to be used for food and drug applications.

Reducing rare earth loss by adding acetic acid in the aluminum removal process of rare earth leaching solution

The ionic-type rare earth ore, abundant in medium and heavy rare earth elements, is a strategic mineral resource. The removal of aluminum from ionic rare earth leaching solution results in over 8% loss of rare earths. Preliminary research has found that adding acetic acid (HAc) during aluminum removal process can effectively reduce the loss of rare earth elements. In this paper, through the calculation of the species distribution in the La2(SO4)3-Al2(SO4)3-HAc-H2O system, it is found that HAc forms an AlOH-Ac+ complex with aluminum ions, with a proportion of up to 70%, which will increase the initial precipitation pH of aluminum hydroxide. Furthermore, HAc and lanthanum form a LaAc2+ complex, and the proportion can reach more than 20%. Moreover, the zeta potential, FT-IR, and XPS tests of aluminum hydroxide, obtained by neutralization precipitation, revealed that the complexation of HAc and aluminum can reduce the precipitation rate of aluminum hydroxide, so that its particle size increases, the specific surface area decreases, and the van der Waals force adsorption sites are reduced. HAc can be chemically adsorbed on aluminum hydroxide, thereby increasing the zeta potential of aluminum hydroxide and ultimately reducing its electrostatic adsorption effect on rare earths. Additionally, the complexation of HAc and rare earth elements can reduce the local supersaturation of rare earth hydroxides and decline the coprecipitation of rare earth elements. Finally, under a precipitation endpoint pH of 5.2, HAc concentration of 0.006 mol/L, aluminum concentration of 0.2 g/L, rare earth concentration of 0.8 g/L, magnesium ion concentration of 0.5 g/L and magnesium oxide slurry concentration of 0.45 mol/L, the aluminum removal efficiency obtained with rare earth leaching solution reached 98.47%, and the rare earth loss efficiency was 2.62%. Compared with the control, the rare earth loss efficiency was reduced by 5.59%. This paper provides guidance for the efficient and green development of ionic-type rare earth ore.

Synergy of Co0-Co2+ in cobalt-based catalysts for CO2 hydrogenation: Quantifying via reduced and exposed atoms fraction

Cobalt (Co)-based catalysts exhibit exceptional versatility in CO2 hydrogenation, yielding valuable fuels and chemicals like methane, methanol, and ethanol. Generally, the Co0–Co2+ synergy plays a vital role in promoting this process, yet a quantifying descriptor remains absent. This study presents a series of CoAl-CO32− layered double hydroxide (LDH) derived catalysts synthesized through coprecipitation. By tuning precipitation pH and reduction temperature, various Co-based catalysts with distinct reduction degrees and dispersions were obtained. By introducing the descriptor "fraction of reduced and surface exposed Co (FCo,r,s)", the Co0–Co2+ synergy is effectively quantified for CO2 hydrogenation. The balanced Co0–Co2+ synergy in catalysts yields a moderate FCo,r,s, resulting in high turnover frequencies (TOFs) for CO2 conversion via HCOO intermediate formed at the Co0–Co2+ interfaces. The HCOO species can be hydrogenated to form methane and methanol, as well as coupled with CHx intermediate followed by hydrogenation to form ethanol. Conversely, catalysts with excessively high or low FCo,r,s display poor Co0–Co2+ synergy and consequently lower TOFs. A clear volcano-shaped relationship between FCo,r,s and TOFs for CO2 conversion, methane, methanol, and ethanol formation underscores its significance as a key determinant of Co-based catalysts' CO2 hydrogenation performance. The catalyst with optimized Co0–Co2+ synergy (precipitated at pH 8.5 and reduced at 750 oC) possesses a high CO2 conversion rate of 26.8 mmol gcat−1 h−1 at a low temperature (i.e., 180 oC).

Fe3+ and Al3+ removal by phosphate and hydroxide precipitation from synthetic NMC Li-ion battery leach solution

The removal of trivalent iron and aluminum was studied from synthetic Li-ion battery leach solution by phosphate and hydroxide precipitation (pH 2.5–4.25, t = 3 h, T = 60 °C). Phosphate precipitation exhibited both crystal nucleation initiation (pH 2 vs. pH 3) as well as complete (~ 99%) Fe and Al removal at lower pH compared to hydroxide precipitation (pH 3 vs. 3.5). The precipitation time of phosphate was shorter (40 min) than that of hydroxide precipitation (80 min). At pH 4 the loss of valuable metals (Li, Ni, Co) in the precipitate was negligible in the phosphate cake, whereas in the hydroxide process the co-precipitation was 4–5% for Li, Ni and Co. The filtration rate of phosphate precipitate was shown to be significantly faster. The presence of fluoride did not have any notable effect on phosphate precipitation, whereas in hydroxide precipitation, it potentially had a negative effect on aluminum extraction.

Wet deposition of sulfur and nitrogen in the Jiuzhaigou World Heritage Site, China: Spatial variations, 2010–2022 trends, and implications for karst ecosystem conservation

Excessive sulfur and nitrogen deposition is a threat to natural ecosystems. This study investigated the spatio-temporal changes of wet sulfur and nitrogen deposition in Jiuzhaigou to understand the responses of wet deposition chemistry to local and national air pollutant emission changes and to assess relevant ecological risks. The results show that local emission sources (e.g., tourism, post-earthquake reconstruction, and vegetation damages) largely elevated the concentrations of SO42−, NO3−, NH4+, and Ca2+ at the non-background sites during 2021–2022; However, the gaps of annual sulfur and nitrogen wet deposition fluxes among the background, semi-background, and non-background sites were reduced by annual precipitation. The pH was also higher at the non-background sites due to stronger acid neutralization capacities from crustal dust there, and acid precipitation (pH < 5.6) was not detected at all the sites. During the 2010 to 2022 period, the wet deposition of SO42− and TIN (i.e. total inorganic nitrogen) and the equivalent ratio of SO42−: NO3− generally presented a declining trend at the background and semi-background sites, as a result of regional and national emission reductions. The TIN reduction from 2015 to 2016 to 2021–2022 at the background site was more from wet NH4+ deposition and the site's NO3− concentrations and fluxes were relatively stable. Compared to the critical loads (CLs) of sulfur and nitrogen for acidification and eutrophication, the annual wet and wet+dry deposition fluxes of sulfur and nitrogen were lower in almost the entire watershed, except for the CLmin of nitrogen for acidification in considerable areas. However, all the wet deposition samples were calcite-unsaturated and had annual TIN concentrations higher than the national environmental standard of total nitrogen for surface water. More field investigations are needed to better assess the ecological risks.

Positive Effects of Organic Amendments on Soil Microbes and Their Functionality in Agro-Ecosystems.

Soil microbial characteristics are considered to be an index for soil quality evaluation. It is generally believed that organic amendments replacing chemical fertilizers have positive effects on changing microbial activity and community structure. However, their effects on different agro-ecosystems on a global scale and their differences in different environmental conditions and experimental durations are unclear. This study performed a meta-analysis based on 94 studies with 204 observations to evaluate the overall effects and their differences in different experimental conditions and duration. The results indicated that compared to chemical fertilizer, organic amendments significantly increased total microbial biomass, bacterial biomass, fungal biomass, Gram-positive bacterial biomass and Gram-negative bacterial biomass, and had no effect on the ratio of fungi to bacteria and ratio of Gram-positive bacteria to Gram-negative bacteria. Meanwhile, land use type, mean annual precipitation and soil initial pH are essential factors affecting microbial activity response. Organic-amendment-induced shifts in microbial biomass can be predominantly explained by soil C and nutrient availability changes. Additionally, we observed positive relationships between microbial functionality and microbial biomass, suggesting that organic-amendment-induced changes in microbial activities improved soil microbial functionality.

Electrophoretic Deposition of Chitosan–Hydroxyapatite Films and Their Electrochemical Behavior in Artificial Plasma

The electrochemical behavior of chitosan–hydroxyapatite films deposited on Ti CP was evaluated. Hydroxyapatite was synthesized from eggshell at different precipitation pH conditions. The films were deposited on the Ti CP surface from chitosan–hydroxyapatite solutions by means of electrophoretic deposition. The hydroxyapatite content of the solutions varied from 0 to 20 g/L. The different films obtained were evaluated by means of electrochemical measurements such as polarization curves, open circuit potential measurements, polarization resistance, and electrochemical impedance. The results obtained showed that regardless of the precipitation pH, it is possible to obtain pure hydroxyapatite from a waste such as eggshell. The incorporation of hydroxyapatite within the chitosan structure allows for improvement of the electrochemical performance of the bare Ti CP surface. It was observed that the passive zone was achieved at lower current densities, and that the stability zone of the passive layer increased. Electrochemical impedance analyzes showed that there is an improvement in corrosion resistance due to a more controlled growth of the passive layer that allows for the formation of a dense and compact film.

Precipitation seasonality and soil pH drive the large-scale distribution of soil invertebrate communities in agricultural ecosystems.

Soil invertebrates contribute significantly to vital ecosystem functions such as the breakdown of organic matter and cycling of essential nutrients, but our knowledge of their large-scale distribution in agricultural systems is limited, which hinders our ability to robustly predict how they will respond to future global change scenarios. Here, we employed metabarcoding analysis of eukaryotic 18S rRNA genes to examine the diversity and community composition of invertebrates in 528 sorghum rhizosphere and bulk soils, collected from 53 experimental field sites across China. Our results revealed that Nematoda, Arthropoda, and Annelida were the dominant soil invertebrate groups in agroecosystems. Among all climatic and soil parameters we examined, precipitation seasonality (i.e. the irregular distribution of precipitation during a normal year) had the strongest relationship with the richness of soil invertebrates, with an increase in soil invertebrate richness predicted with increasing precipitation seasonality. Mean annual precipitation and soil pH were the most important predictors of soil invertebrate community structure, with numerous invertebrate phylotypes showing either significantly positive or negative relationships with these two variables. Our findings suggest that shifts in precipitation patterns and soil pH, induced by future climate change and agricultural practices, will have important consequences for the distribution of soil invertebrate communities, with implications for agricultural ecosystem sustainability.

Subcritical water‐treated soy protein‐gum Arabic core‐shell nanoparticles as phytosterol carriers

SummarySoy protein‐gum Arabic (GA) core‐shell nanoparticles were fabricated as carriers for hydrophobic phytosterol (PS) using an anti‐solvent precipitation (pH 7.0) and then coating GA on the surface of protein‐based PS nanoparticles at pH 4.5. PS nanoparticles stabilised by heat‐treated soy protein isolate (SPI), especially subcritical water‐treated SPI (SW, 120 °C), exhibited higher encapsulation efficiency (EE), loading amount (LA) and colloidal stability than native SPI‐stabilised PS nanoparticles. The highly flexible conformation and more exposed hydrophobic clusters of SW‐treated SPI could result in a quick encapsulation of more PS into the interior of protein molecules during anti‐solvent precipitation. However, for native SPI with rigid globular structure, the loading of PS mainly occurred on the surface hydrophobic sites of protein molecules. After introducing GA (≥5 mg mL−1) to PS nanoparticles fabricated by SW‐treated SPI, submicron‐sized (Dh 250.71~341.76 nm) core‐shell nanoparticles with high acid solubility and thermal stability were formed. The coating of GA decelerated the digestion of SW‐treated SPI, and improved the EE, LA and in vitro bioaccessibility of PS under acidic environment. These results reveal the protein structure dependence of PS encapsulation and provide a simple approach to fabricate biopolymer‐based nanoparticle delivery system for hydrophobic bioactives in acidified functional drinks.

Extraction of proteins from aqueous and salt solutions of porcine edible byproducts using the pH-shifting technique

The use of aqueous and saline solution and the treatment with sodium nitrite in the protein extraction by the pH-shifting technique of edible pig byproducts (heart and liver) were evaluated. Protein solubility curves were obtained, and the optimal pH of solubility (PS) and precipitation (isoelectric point, pI) were defined. The addition of salt increases the solubility in alkaline pH (11.0) for both byproducts, being set at 2.0 for the liver and 3.0 for the heart. The precipitation yields of the total protein were lower in the aqueous heart extracts (71.75%) than in the other extracts (84.23%), but the precipitation yield of total heme pigments (77.63%) was not affected by the treatments or byproduct type. The yield of protein recovery was higher in liver extracts (68.04%) than in heart extracts (49,98%), regardless of the extraction solution used. The increasing additions of nitrite increased the levels of residual nitrite (NO2R) on the precipitates, but lower additions were enough to favor the formation of the pinkish-red color characteristic of cured meat products, by increasing the redness (a*) and reducing the hue angle (h) color. Higher values of NO2R and a* and lower values of h were also observed in the precipitates extracted by the saline solution when compared to those obtained by the aqueous solution. Thus, the use of saline solutions supplemented with 20 mg/mL sodium nitrite proved to be a viable alternative in protein recovery processes in pig byproducts, especially in livers, being a promising alternative to development of techno-functional ingredients to use in meat products.

Study on rheological properties and damage mechanism of asphalt under acid-alkali precipitation corrosion

This research delved into the effects of pH precipitation on asphalt's rheological characteristics and damage mechanisms. We analyzed the shifts in asphalt's acid-alkali corrosion properties through macro and micro tests. To begin with, we conducted three cycles of bitumen corrosion tests using acidic, alkaline, and neutral solutions. Subsequently, the dynamic shear rheological test (DSR) measured the complex shear modulus, phase angle, and rutting factor before and after asphalt corrosion, revealing correlations between corrosion duration, temperature, and asphalt's rheological traits. Additionally, we evaluated post-corrosion changes in asphalt's functional groups through infrared spectrum testing, allowing us to deduce the underlying damage mechanism. Our results showed that asphalt's deformation resistance was directly related to soaking time and inversely related to temperature. The complex shear modulus exhibited an inverse relationship with temperature, while the phase angle demonstrated a direct proportionality to temperature variations. From a chemical perspective, acidic components within asphalt tend to dissolve and ionize, while alkaline substances undergo esterification and neutralization. Notably, asphalt modified with styrene–butadiene–styrene (SBS) exhibits enhanced resistance against acid and alkali corrosion, surpassing the performance of the 90# asphalt. Ultimately, this research established a theoretical framework for exploring acid-base precipitation resistance in asphalt binders, contributing to our understanding of asphalt's binder properties and broadening its applications.