Structure and functionality of whey protein, pea protein, and mixed whey and pea proteins treated by pH shift or high-intensity ultrasound.

Three modifications (pH shift, ultrasound, combined pH shift and ultrasound) induced alterations in pure whey protein isolate (WPI), pea protein isolate (PPI), and mixed whey and pea protein (WPI-PPI) were investigated. The processing effect was related to the protein type and technique used. Solubility of WPI remained unchanged by various treatments. Particle size was enlarged by pH shift while reduced by ultrasound and combined approach. All methods exposed more surface hydrophobic groups on WPI, while pH shift and joint processing was detrimental to its emulsifying activity. The PPI and mixture exhibited similar responses toward the modifications. Solubility of PPI and the blend enhanced in the sequence of pH shift and ultrasound > ultrasound > pH shift. Individual approach expanded while co-handling diminished the particle diameter. Treatments also caused more disclosure of hydrophobic regions in PPI and WPI-PPI and emulsifying activity was ameliorated in the order of pH shift and ultrasound > ultrasound > pH shift.

Complexation of bovine lactoferrin with selected phenolic acids via noncovalent interactions: Binding mechanism and altered functionality.

Noncovalent interactions of 4 selected phenolic acids, including gallic acid (GA), caffeic acid (CA), chlorogenic acid (CGA), and rosmarinic acid (RA) with lactoferrin (LF) were investigated. Compound combined with LF in the binding constant of CA > GA > RA > CGA, driven by van der Waals and hydrogen bonding for GA, and hydrophobic forces for others. Conformation of LF was affected at secondary and ternary structure levels. Molecular docking indicated that GA and CA located in the same site near the iron of the C-lobe, whereas RA and CGA bound to the C2 and N-lobe, respectively. Significantly enhanced antioxidant activity of complexes was found compared with pure LF, as demonstrated by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis(2-ethylbenzothiazoline-6-sulfonate) (ABTS), and ferric reducing antioxidant power (FRAP) models. Caffeic acid, CGA, and RA significantly decreased the emulsifying stability index and improved foam ability of LF, and the effect of CA and RA was the most remarkable, respectively.

Proteomic characterization and comparison of milk fat globule membrane proteins of Saanen goat milk from 3 habitats in China using SWATH-MS technique.

Saanen goats are among the major dairy goats in China. In present study, variation of milk fat globule membrane proteins profile of Saanen goat milk caused by geographic location was investigated using sequential window acquisition of all theoretical fragment ions data-independent acquisition mass spectrometry based proteomic approach. A total of 1,001 proteins were quantified in goat milk collected from 3 habitats of China [Guangdong (GD); Inner Mongolia (IM); Shannxi (SX)]. Most of the proteins were found to act cellular process of biological process, cell of cellular component, binding of molecular function after Gene Ontology annotation and metabolic of pathway indicated by Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Differentially expressed proteins (DEP) for GD versus IM, GD versus SX, IM versus SX were identified to be 81, 91, and 44, respectively. Gene Ontology enrichment analysis showed that the greatest DEP for 3 groups (GD vs. IM, GD vs. SX, IM vs. SX) were cellular process, cellular process and organonitrogen compound biosynthetic process/immune system process for biological process. For cellular component, the largest number of DEP for 3 comparison groups were organelle, organelle and organelle/intracellular. For molecular function, DEP of the 3 comparison groups were expressed most in structural molecule activity, binding and anion binding, respectively. Pathways with the majority of DEP were ribosome, systemic lupus erythematosus and primary immunodeficiency/systemic lupus erythematosus/amoebiasis/PI3K-Akt signaling pathway for GD versus IM, GD versus SX and IM versus SX, severally. Protein-protein interaction network analysis showed that DEP interacted most were 40S ribosomal protein S5, fibronectin and Cytochrome b-c1 complex subunit 2, mitochondrial for GD versus IM, GD versus SX and IM versus SX, separately. Data may give useful information for goat milk selection and milk authenticity in China.

Towards understanding the interaction between ultrasound-pretreated ß-lactoglobulin monomer with resveratrol.

Increasingly, studies are using ultrasound to elevate the functional properties of proteins, so the interaction between phenolic compounds and proteins induced by ultrasound needs to be further understood. ß-Lactoglobulin (ß-LG) at pH 8.1, which exists mainly as monomers, was ultrasound treated at 20 kHz ultrasonic intensity and 30% amplitude for 0-5 min and subsequently interacted with resveratrol. Fluorescence data showed that ultrasound pretreatment improved binding constant (Ka ) from (1.62 ± 0.45) × 105 to (9.43 ± 0.55) × 105 M-1 and binding number from 1.13 ± 0.09 to 1.28 ± 0.11 in a static quenching mode. Fluorescence resonance energy transfer (FRET) analysis indicated that resveratrol bound to the surface hydrophobic pocket of native and treated proteins with no obvious changes in energy transfer efficiency (E) and Föster's distance (r). Thermodynamic parameters indicated that ultrasonication shifted the main driving force from the hydrophobic force for native and 1-min treated ß-LG to van der Waals forces and hydrogen bonding for both 3-min and 5-min treated proteins. Ultrasonication and resveratrol addition generated significant differences in surface hydrophobicity and the surface charge of the protein (P < 0.05), whereas they had little influence on the secondary structure of ß-LG. Compared with the native ß-LG/resveratrol complex, ultrasound-treated protein complexes showed significantly stronger 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) scavenging capacity (P < 0.05), and kept relatively stable after 180-min irradiation. Data provided by this study can lead to a better comprehension of the structure and molecular events occurring during the complexing process between an ultrasound-pretreated protein with polyphenol.

Formation and characterization of noncovalent ternary complexes based on whey protein concentrate, high methoxyl pectin, and phenolic acid.

Protein-polysaccharide-polyphenol noncovalent ternary complexes possess unique physicochemical, structural, and functional properties. In the present study, ternary complexes based on whey protein concentrate (WPC; 2%, wt/vol) and high methoxyl pectin (HMP; 0.5%, wt/vol) complexes and 0.2 to 0.6% (wt/vol) chlorogenic acid (CA) or rosmarinic acid (RA) were formed and characterized at 3 pH values (4, 4.5, and 5). The pH conditions were decided according to phase diagram of WPC and HMP during acidification. Fluorescence quenching experiments indicated that WPC-HMP complexes bound RA stronger than CA and the binding constant increased with increasing pH for both phenolic acids. Particle size of ternary complexes decreased and absolute ζ-potential increased with pH values changing from 4 to 5, and RA influenced the particle size of WPC-HMP complexes greater than CA. The CA and RA in ternary complexes showed good stability against UV light with pH order of pH 5 > pH 4.5 > pH 4. Fourier-transform infrared spectroscopy spectra indicated the involvement of hydrogen bonding between WPC-HMP and CA or RA. Antibacterial tests showed that ternary complexes had good antibacterial activity against Staphylococcus aureus and Escherichia coli at concentrations of 6.2 mg/mL and the ability increased with decreasing pH values. All ternary complexes possessed strong scavenging radical capacities with median inhibitory concentration (IC50) values ranging from 2.71 ± 0.05 to 6.20 ± 0.41 µg/mL. Antioxidative ability of ternary complexes increased as pH went up and WPC-HMP-RA showed significantly higher antioxidative property compared with WPC-HMP-CA. Data may provide useful information for rational design of ternary complexes and applications of the formed complexes in food matrices such as beverages and emulsions.

Fabrication and characterization of a cannabidiol-loaded emulsion stabilized by a whey protein-maltodextrin conjugate and rosmarinic acid complex.

A cannabidiol (CBD)-loaded oil-in-water emulsion stabilized by a whey protein (WP)-maltodextrin (MD) conjugate and rosmarinic acid (RA) complex was fabricated, and its stability characteristics were investigated under various environmental conditions. The WP-MD conjugates were formed via dry-heating. The interaction between WP and MD was assessed by browning intensity, reduced amount of free amino groups, the formation of high molecular weight components in sodium dodecyl sulfate-PAGE, and changes in secondary structure of whey proteins. The WP-MD-RA noncovalent complex was prepared and confirmed by fluorescence quenching and Fourier-transform infrared spectroscopy spectra. Emulsions stabilized by WP, WP-MD, and WP-RA were used as references to evaluate the effect of WP-MD-RA as a novel emulsifier. Results showed that WP-MD-RA was an effective emulsifier to produce fine droplets for a CBD-loaded emulsion and remarkably improved the pH and salt stabilities of emulsions in comparison with WP. An emulsion prepared with WP-MD-RA showed the highest protection of CBD against UV and heat-induced degradation among all emulsions. The ternary complex kept emulsions in small particle size during storage at 4°C. Data from the current study may offer useful information for designing emulsion-based delivery systems which can protect active substance against environmental stresses.

Comparative analysis of caseins in Saanen goat milk from 3 different regions of China using quantitative proteomics.

A quantitative proteomic technique based on data-independent acquisition (DIA) was used to analyze differentially expressed caseins of Saanen goat milk samples collected from 3 regions in China (Guangdong, GD; Inner Mongolia, IM; Shaanxi, SX). A total of 345 proteins were quantified in each sample. Gene Ontology (GO) analysis showed that proteins were mainly involved in cellular process and cell and binding functions. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that proteins were mainly involved in metabolic pathways. Differentially expressed proteins (DEP) between goat milk from 3 comparison groups composed of paired regions were compared and analyzed. The number of DEP was 114, 69, and 79 for GD versus IM, GD versus SX, and IM versus SX, respectively. The GO enrichment analysis of the 3 comparison groups showed that differences were mainly related to the regulation of biological quality, biological regulation, and response to stimulus in terms of biological process; extracellular region for cellular component; and binding function for molecular function. Pathways in which DEP of GD versus IM, GD versus SX, and IM versus SX were mostly protein processing in endoplasmic reticulum for the first 2 groups and metabolic pathways for the last. Protein-protein interaction network analysis demonstrated that the most prominent DEP was heat shock protein 90 ß family member 1 for both the GD versus IM and the GD versus SX groups, and haptoglobin for the IM versus SX group. Data from this study may offer useful information for further investigation of the protein composition of Saanen goat milk and its application in the dairy industry.

Proteomic analysis of differentially expressed whey proteins in Saanen goat milk from different provinces in China using a data-independent acquisition technique.

Whey proteins of Saanen goat milk samples from 3 provinces in China (Guangdong, GD; Inner Mongolia, IM; Shaanxi, SX) were characterized and compared using data-independent acquisition quantitative proteomics technique. A total of 550 proteins were quantified in all 3 samples. There were 44, 44, and 33 differentially expressed proteins (DEP) for GD versus IM, GD versus SX, and IM versus SX, respectively. Gene ontology annotation analysis showed that the largest number of DEP for the 3 comparisons were as follows: for biological processes: response to progesterone, glyceraldehyde-3-phosphate metabolic process, and negative regulation of megakaryocyte differentiation; for molecular functions: antioxidant activity, binding, and peroxiredoxin activity; and for cellular components: the same category of extracellular regions for the 3 comparisons, respectively. Pathways for the DEP of 3 comparisons were (1) disease; (2) synthesis and metabolism; and (3) synthesis, degradation, and metabolism. Protein-protein interaction network analysis showed that DEP for GD versus SX had the most interactions.

Polymerized Whey Protein Concentrate-Based Glutathione Delivery System: Physicochemical Characterization, Bioavailability and Sub-Chronic Toxicity Evaluation.

Glutathione (GSH) is a powerful antioxidant, but its application is limited due to poor storage stability and low bioavailability. A novel nutrient encapsulation and delivery system, consisting of polymerized whey protein concentrate and GSH, was prepared and in vivo bioavailability, antioxidant capacity and toxicity were evaluated. Polymerized whey protein concentrate encapsulated GSH (PWPC-GSH) showed a diameter of roughly 1115 ± 7.07 nm (D50) and zeta potential of 30.37 ± 0.75 mV. Differential scanning calorimetry (DSC) confirmed that GSH was successfully dispersed in PWPC particles. In vivo pharmacokinetics study suggested that PWPC-GSH displayed 2.5-times and 2.6-fold enhancement in maximum concentration (Cmax) and area under the concentration-time curve (AUC) as compared to free GSH. Additionally, compared with plasma of mice gavage with free GSH, significantly increased antioxidant capacity of plasma in mice with PWPC-GSH was observed (p < 0.05). Sub-chronic toxicity evaluation indicated that no adverse toxicological reactions related to oral administration of PWPC-GSH were observed on male and female rats with a diet containing PWPC-GSH up to 4% (w/w). Data indicated that PWPC may be an effective carrier for GSH to improve bioavailability and antioxidant capacity.

Proteomic analysis of whey proteins in the colostrum and mature milk of Xinong Saanen goats.

Xinong Saanen goats are among the major dairy goats in China, and their milk is one of the major milk supplies for the Chinese dairy industry. To explore the whey proteome of Xinong Saanen goat milk, we analyzed the whey proteins of goat colostrum and mature milk using proteomic techniques. We identified a total of 314 and 524 proteins in goat colostrum and mature milk, respectively. Our data showed the first 3 functional categories of signal, disulfide bond, and secreted in both milk types. The most abundant Gene Ontology annotations in both milks were the biological process of positive regulation of extracellular regulated protein kinases (ERK)1 and ERK2 cascade; the cellular component of extracellular exosome; and the molecular function of calcium ion binding. Goat colostrum whey proteins showed more disease-related pathways, and mature milk showed more pathways associated with metabolism. Moreover, we observed several pathways involved in intestinal mucosal immunity only in colostrum. Protein-protein interaction network and module analysis revealed that complement and coagulation cascades and Staphylococcus aureus infection were significant in the whey proteins of both milks, and carbon metabolism was more common for mature milk than for colostrum. These findings could provide useful information for the use of goat milk whey proteins in the Chinese dairy industry.

Characterization of the milk fat globule membrane proteome in colostrum and mature milk of Xinong Saanen goats.

Xinong Saanen goat milk is a major source of milk in the Chinese dairy industry. Milk fat globule membrane (MFGM) proteomes of goat colostrum and mature milk were analyzed and compared using proteomic technology. A total of 543 and 585 proteins were identified in goat colostrum and mature milk, respectively. Functional category analyses revealed that most of the MFGM proteins in both colostrum and mature milk were related to phosphoprotein and acetylation. The biological process of translation, cellular component of extracellular exosome, and molecular function of poly(A) RNA binding were the main gene ontology annotations of both colostrum and mature milk. Pathways associated with disease and genetic information processing involved large number of proteins in colostrum and mature milk, and more metabolism-related pathways were observed in mature milk. Protein-protein interaction network analyses showed that ribosome was abundant in both colostrum and mature milk. Colostrum showed more functions associated with protein processing in the endoplasmic reticulum, whereas mature milk had more oxidative phosphorylation functions. The results could provide further understanding of the unique biological properties of MFGM proteins of goat colostrum and mature milk.

Proteomic analysis of differentially expressed whey proteins in Guanzhong goat milk and Holstein cow milk by iTRAQ coupled with liquid chromatography-tandem mass spectrometry.

Guanzhong goat and Holstein cow milk are the major milks supplied in China. Whey proteins play an important role in immune defense for newborn mammals. This study aimed to analyze the differentially expressed whey proteins of Guanzhong goat milk and Holstein cow milk by using isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomics techniques. A total of 165 whey proteins were quantified, 114 of which differed significantly in abundance in goat and cow milks. According to the "up_keywords," in the online DAVID tool (https://david.ncifcrf.gov/home.jsp), 75% of these differentially expressed whey proteins were related to the category of "signal." Gene Ontology analyses classified these differentially expressed proteins into biological processes, cellular components, and molecular functions. The most common biological process was response to stress, the most common cellular component was related to extracellular region, and the most prevalent molecular function was binding. Kyoto Encyclopedia of Genes and Genomes pathway analyses showed that these proteins were mainly involved in the complement and coagulation cascade pathways. The results improve our understanding of the different biological properties of whey proteins in goat and cow milks.

Effects of High Intensity Ultrasound on Physiochemical and Structural Properties of Goat Milk ß-Lactoglobulin.

This study aimed to compare the effects of high intensity ultrasound (HIU) applied at various amplitudes (20~40%) and for different durations (1~10 min) on the physiochemical and structural properties of goat milk ß-lactoglobulin. No significant change was observed in the protein electrophoretic patterns by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Deconvolution and second derivative of the Fourier transform infrared spectra (FTIR) showed that the percentage of ß-sheet of goat milk ß-lactoglobulin was significantly decreased while those of α-helix and random coils increased after HIU treatment The surface hydrophobicity index and intrinsic fluorescence intensity of samples was enhanced and increased with increasing HIU amplitude or time. Differential scanning calorimetry (DSC) results exhibited that HIU treatments improved the thermal stability of goat milk ß-lactoglobulin. Transmission electron microscopy (TEM) of samples showed that the goat milk ß-lactoglobulin microstructure had changed and it contained larger aggregates when compared with the untreated goat milk ß-lactoglobulin sample. Data suggested that HIU treatments resulted in secondary and tertiary structural changes of goat milk ß-lactoglobulin and improved its thermal stability.

Preparation and Characterization of Whey Protein Isolate-DIM Nanoparticles.

3,3'-Diindolylmethane (DIM) is a bioactive compound found in Cruciferous vegetables that possesses health benefits such as antioxidant, anticancer, and anti-inflammatory effects. However, hydrophobicity and photolabile limit its pharmaceutical applications. This study aims to prepare and characterize DIM-encapsulated whey protein isolate (WPI) nanoparticles mixed at different ratios of WPI and DIM using the combined heating-ultrasound method. Results showed that all the samples showed adequate physicochemical characteristics: The mean particle size of the nanoparticles could be controlled down to 96-157 nm depending on the DIM to WPI ratio used in the preparation with a low polydispersity index (<0.5), higher negative values of zeta potential (>-40 mV) as well as with greater encapsulation efficiency (>82%). Flow behavior indices showed the shear-thinning Non-Newtonian or pseudoplastic (n < 1) behavior of the nanoparticles. The thermal properties were characterized by differential scanning calorimetry (DSC), which showed that DIM was successfully entrapped in WPI nanoparticles. The secondary structure of WPI was changed after DIM incorporation; electrostatic interaction and hydrogen bonding were major facilitating forces for nanoparticles formation, confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Transmission electron microscopy (TEM) micrographs showed that all the samples had a smooth surface and spherical structure. The wall material (WPI) and encapsulation method provide effective protection to DIM against UV light and a broad range of physiologically relevant pH's (2.5, 3.5, 4.5, 5.5, and 7). In conclusion, whey protein isolate (WPI)-based nanoparticles are a promising approach to encapsulate DIM and overcome its physicochemical limitations with improved stability.

Heat-Induced Interactions between Whey Protein and Inulin and Changes in Physicochemical and Antioxidative Properties of the Complexes.

Whey protein and inulin at various weight ratios were dry heated at 60 °C for 5 days under relative humidity of 63%. The heated mixtures were found to have significant changes in browning intensity and zeta-potential compared to untreated mixture. Heated samples showed significantly lower surface hydrophobicity than untreated mixtures. Compared with untreated samples, dry-heated samples showed significantly higher 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) scavenging ability with whey protein to inulin mass ratios of 1:2 and 1:3 and significantly higher 2,2'-Azinobis(2-Ethylbenzothiazoline-6-Sulfonate) (ABTS) scavenging abilities and oxygen radical absorbance capacity (ORAC) at all weight ratios. Dry heat-induced interactions between whey protein and inulin was confirmed by changes in Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) protein profile, Fourier Transform Infrared Spectroscopy (FT-IR) and Far-ultraviolet Circular Dichroism (Far-UV CD) spectra. Dry heating caused physicochemical and structural changes of whey protein and therefore the complexes can be used to improve the antioxidative properties of the mixture under certain conditions.

Effects of Ultrasound Treatment on Extraction and Rheological Properties of Polysaccharides from Auricularia Cornea var. Li.

Auricularia cornea var. Li. is an edible fungi and polysaccharides in Auricularia cornea var. Li. may have bioactive activities. Polysaccharides from Auricularia cornea var. Li. (ACP) was extracted using ultrasound-assisted extraction (UAE) method and compared with hot water extraction (HWE) for extraction yield, extraction rate, purity of polysaccharides, microstructure of residues after extraction, preliminary structure and rheological properties of polysaccharides. Optimum conditions for UAE (particle size of 150⁻200 mesh, water to raw material ratio of 70:1, extraction temperature at 70 °C for 40 min, ultrasonic amplitude of 40%) and HWE (particle size of 150⁻200 mesh, water to raw material ratio of 60:1, extraction temperature at 90 °C for 3.0 h) were obtained via single-factor experiment. Under optimum conditions, extraction yield of polysaccharides by UAE was 30.99 ± 1.93% which showed no significant difference with that by HWE (30.35 ± 1.67%) (P > 0.05). Extraction rate (29.29 ± 1.41%) and purity (88.62 ± 2.80%) of polysaccharides by UAE were higher than those by HWE (extraction rate of 24.95 ± 2.78% and purity of 75.33 ± 6.15%) (P < 0.05). Scanning Electron Microscopy (SEM) images of residues by UAE showed more broken cells than those by HWE. Fourier Transform Infrared (FTIR) spectra showed that the dialyzed ACP extracted by HWE and UAE (DACP-HWE and DACP-UAE) had similar characteristic absorption peaks of polysaccharides. Both DACP-HWE and DACP-UAE solutions showed typical shear thinning and temperature-independent behaviors (25⁻90 °C) and UAE resulted in polysaccharides with remarkably lower viscosity in comparison with HWE. DACP-UAE solutions exhibited more liquid-like state while DACP-HWE solutions solid-like system. Data indicated that ultrasound treatment may be a useful means for extraction of polysaccharides from Auricularia cornea var. Li.

Physicochemical and Microstructural Properties of Polymerized Whey Protein Encapsulated 3,3'-Diindolylmethane Nanoparticles.

The fat-soluble antioxidant 3,3'-diindolylmethane (DIM), is a natural phytochemical found in Brassica vegetables, such as cabbage, broccoli, and Brussels sprouts. The stability of this compound is a major challenge for its applications. Polymerized whey protein (PWP)-based DIM nanoparticles were prepared at different mass ratios of protein and DIM by mixing PWP and DIM followed by ultrasound treatment for 4 min. All the nanoparticles were studied for particle size, zeta potential, rheological and microstructural properties, and storage stability. The mean particle size of the PWP-based nanoparticles was significantly increased (p < 0.05) by the addition of DIM at different mass ratios, ranging from 241.33 ± 14.82 to 270.57 ± 15.28 nm. Zeta potential values of all nanoparticles were highly negative (greater than ±30 mV), suggesting a stable solution due its electrostatic repulsive forces. All samples exhibited shear thinning behavior (n < 1), fitted with Sisko model (R² > 0.997). Fourier Transform Infrared (FTIR)spectra revealed that the secondary structure was changed and the absorption intensity for hydrogen bonding got stronger by further incorporating DIM into PWP. Transmission electronic microscopy (TEM) images showed spherical and smooth surface shape of the PWP-based nanoparticles. DIM encapsulated by PWP showed enhanced stability at 4, 37 and 55 °C for 15 days evidenced by changes in mean particle size and color (a*-value and b*-value) compared with control (DIM only). In conclusion, the polymerized whey protein based 3,3'-diindolylmethane nanoparticles are stable and the encapsulation may protect the core material from oxidation.

Interactions between ß-Lactoglobulin and 3,3'-Diindolylmethane in Model System.

The compound 3,3'-diindolylmethane (DIM) has a broad spectrum of anticancer activities. However, low stability and bioavailability limit its application. Elucidating interactions between DIM and ß-lactoglobulin (ß-LG) may be useful for fabricating whey protein-based protecting systems. Interaction with DIM increased the diameter and absolute zeta potential value of ß-LG. UV-absorption spectra suggested that there was a complex of DIM and ß-LG. ß-LG showed enhanced fluorescence intensity by complexing with DIM with a binding constant of 6.7 × 105 M-1. Upon interaction with DIM, ß-LG was decreased in secondary structure content of helix and turn while increased in ß-sheet and unordered. FT-IR spectra and molecular docking results indicated the roles of hydrophobic interaction and hydrogen bond for the formation of DIM and ß-LG nanocomplexes. Data suggested that ß-LG may be a good vehicle for making a protein-based DIM protection and delivery system due to the tight binding of DIM to ß-LG.

Systematical characterization of physiochemical and rheological properties of thermal-induced polymerized whey protein.

BACKGROUND: Effects of pH (6-8), protein concentration (60-110, g kg-1 ), heating temperature (70-95 °C) and time (5-30 min) on physiochemical and rheological properties of thermal-induced polymerized whey protein isolate (PWP) were systematically investigated. Degree of denaturation, particle size, zeta potential, free sulfhydryl group content, surface hydrophobicity and apparent viscosity were determined. RESULTS: Heating whey protein above 75 °C at pH 7 or 8 resulted in denaturation of 80-90% whey protein. pH variation had a remarkable influence on particle size of samples (P < 0.05), whereas heating temperature and time did not generate significant changes. Zeta potential of PWP samples fell in the range of -30 to -40 mV. Free sulfhydryl group content of PWP samples decreased with increasing level regarding each factor. Surface hydrophobicity analysis showed that samples at higher pH or concentration became less hydrophobic, and increasing heating temperature or time resulted in higher hydrophobicity index. Time sweep test revealed that increasing protein concentration, heating temperature or time led to higher apparent viscosity. Flow behavior of PWP samples approached Newtonian character as protein concentration, heating temperature or time decreased. CONCLUSION: Systematic data may provide helpful information in designing a heating process for dairy products and application of PWP in the food industry. © 2018 Society of Chemical Industry.

Protein digestion properties of Xinong Saanen goat colostrum and mature milk using in vitro digestion model.

BACKGROUND: Xinong Saanen goat milk is a raw material for goat milk-based infant formula production. This study aims to analyze digestion properties of Xinong Saanen goat colostrum and mature milk by simulating infant gastrointestinal digestion. Zeta potential, particles size, protein profile and peptides composition of these two kinds of milk during the digestion process were studied. RESULTS: Zeta-potential values of the digested colostrum were lower than those of mature milk through the whole digestion. Absolute zeta potential of colostrum duodenal digestion samples showed a decrease from 16.63 ± 2.08 to 11.80 ± 2.03 mV while that of mature milk decreased sharply and then increased (P < 0.05). Colostrum had a larger particle size than mature milk and both milks showed decreased particle size with increasing digestion time but an increase for the last 30 min. Colostrum showed more high molecular weight (MW) proteins which cannot be hydrolyzed completely compared with mature milk. Digested peptides (< 10 kDa) were characterized using liquid chromatography combined with tandem mass spectrometry (LC-MS/MS). The casein-derived peptides identified in digested colostrum and mature milk accounted for 76.67% and 59.53%, respectively. ß-Casein was the most abundant in colostrum while that in mature milk was αs1 -casein. Enterotoxin-binding glycoprotein PP20K, butyrophilin subfamily 1 member A1 (BTN1A1) and perilipin (PLIN) were only detected in digested mature milk. CONCLUSION: Differences in digestion properties between goat colostrum and mature milk were mainly shown in duodenal digestion phase. Data may provide useful information about utilization of goat milk for infant formula formulation. © 2019 Society of Chemical Industry.