Enhanced foaming and emulsifying properties of high-pressure-jet-processed skim milk

Tri-component hydrocolloid as egg white replacement in meringues: gellan gum with soy protein isolate and maltodextrin

BACKGROUND

In the quest for sustainable food ingredients, the present study delves into the potential of a tri-component hydrocolloid blend, comprising gellan gum (GG), soy protein isolate (SPI) and maltodextrin (MD), as a replacement for egg white in meringue production. The research aims to elucidate the intricate physical properties of meringue containing this tri-component structure, focusing on foaming dynamics, rheological behavior and the textural properties of the resulting meringue cookies.

RESULTS

Experiments were conducted with various hydrocolloids (k-carrageenan, GG, and locust bean gum) and GG was identified as optimal for improving foaming capacity and foaming stability. Rheological evaluations showed a positive correlation between increased GG concentration within the tri-component matrix and an increase in both storage modulus (G') and loss modulus (G"), indicating improved structural integrity. Furthermore, a comparative analysis of the texture profiles of cookies prepared with this blend highlighted the ability of higher GG concentrations to satisfactorily replicate the tactile and visual qualities of traditional egg white-based meringues. This result was particularly evident compared to formulations utilizing solely SPI or the combined SPI-MD configuration.

CONCLUSION

Conclusively, the results of the present study highlight the significant potential of the GG-SPI-MD tri-component structure to closely mimic the critical properties of egg white, thus offering a promising plant-based alternative for meringue production. © 2024 Society of Chemical Industry.

Enhancing casein micelle dissociation in diluted skim milk systems using combined processing techniques

The present work aims to evaluate the dissociation of casein micelles in diluted skim milk (SM) systems after undergoing solvent- or emulsifying salt-based dissociation coupled with ultra-high-pressure homogenization (UHPH). Specifically, Part I evaluated dilute SM solutions combined with varying ethanol concentrations (0- 60%) at varying temperatures (5 - 65°C) in combination with UHPH (100-300 MPa), and Part II evaluated dilute SM solutions combined with varying concentrations (0-100 mM) of either sodium hexametaphosphate (SHMP) or sodium citrate (SC) in combination with UHPH (100-300 MPa). In Part I, high concentrations of ethanol (40-60% vol/vol) at elevated temperatures (45-65°C) achieved extensive dissociation of casein micelles, especially in combination with UHPH at ≥200 MPa, as shown by an ca. 6-fold reduction in sample absorbance and an ca. 3-fold reduction in casein particle size compared with the control (ca. dilute SM, 65°C) under optimum conditions (dilute SM, 60% ethanol, 65°C, ≥ 200 MPa). In Part II, the level of casein micelle dissociation using emulsifying salts (ES) was dependent on the ES type and concentration. Considerable casein micelle dissociation in dilute SM systems was achieved with SHMP concentrations ≥1 mM and SC concentrations ≥10 mM, resulting in decreased sample absorbance (>6-fold decrease in absorbance), bimodal casein size distributions, and increased hydrophobicity (ca. 2-fold increase in intrinsic fluorescence) compared with the control (dilute SM). This dissociation was further enhanced with UHPH (≥200 MPa). These results indicate that both solvent- and ES-based casein dissociation techniques can be optimized when used in combination with UHPH. Together, these processing techniques can be used to extensively dissociate casein micelles with the potential to use these altered systems for value-added applications such as functional ingredients or encapsulation agents.

Preparation of housefly (Musca domestica) larvae protein hydrolysates: Influence of dual-sweeping-frequency ultrasound-assisted enzymatic hydrolysis on yield, antioxidative activity, functional and structural attributes

Dual-sweeping-frequency ultrasound (DSFU) was utilized in the preparation of polypeptides from housefly (Musca domestica) larvae protein (HLP). Results indicated that ultrasonication (20 ± 2/28 ± 2 kHz, 42 W/L, 25 min) significantly increased peptide yield and DPPH scavenging capacity by 8.25 % and 14.83 %, respectively. Solubility, foaming and emulsification properties of polypeptides were improved by 19.89 %, 33.33 % and 38.74 % over the control; along with notable reduction in particle size and increase in zeta potential. Tertiary structural changes of the sonicated hydrolysates were illustrated by UV and fluorescence spectra. FTIR showed that ultrasonication increased α-helix, β-turn, and random coil by 38.23 %, 46.35 % and 16.36 %, respectively, but decreased β-sheet by 48.03 %, indicating partial unfolding in HLP hydrolysate conformation and reduction in intermolecular interactions. The research results demonstrated that dual-sweeping-frequency ultrasonication has a great prospect in industry application for the purpose of improving enzymolysis efficiency and product quality for housefly larvae protein hydrolysates production.

Effects of high-pressure homogenization on the physicochemical, foaming, and emulsifying properties of chickpea protein

In order to expand the utilization of chickpeas in various food products, this study investigated the effects of different homogenization pressures (0-150 MPa) and cycles (1-3) on the physicochemical, and functional properties of chickpea protein. After high-pressure homogenization (HPH) treatment, hydrophobic groups and sulfhydryl groups of chickpea protein was exposed which increased its surface hydrophobicity and decreased its total sulfhydryl content. SDS-PAGE analysis showed that the molecular weight of modified chickpea protein remained unchanged. The particle size and turbidity of chickpea protein significantly decreased with an increase in homogenization pressure and cycles. Furthermore, the solubility, foaming, and emulsifying properties of chickpea protein were all enhanced by HPH treatment. In addition, the emulsions prepared by modified chickpea protein showed better stability capacity due to its smaller particle size and higher zeta potential. Therefore, HPH might be an effective technique to improve the functional properties of chickpea protein.

Effect of shearing-induced lipolysis on foaming properties of milk

BACKGROUND

The attraction of cappuccino-style beverages is attributed to the foam layer, as it greatly improves the texture, appearance, and taste of these products. Typical milk has a low concentration of free fatty acids (FFAs), but their concentration can increase due to lipolysis during processing and storage, which is detrimental to the foamability and foam stability of milk. There are contradictory results in reported studies concerning the effects of FFAs on the foaming properties of milk due to differences in milk sources, methods inducing lipolysis, and methods of creating foam. In this study, the foaming properties and foam structure of milk samples whose lipolysis was induced by ultra-turraxing, homogenisation, and microfluidisation (1.5-3.5 μ-equiv. mL^-1 FFAs) were investigated.

RESULTS

Compared with others, microfluidised milk samples had the smallest particle size, lowest absolute zeta potential, and highest surface tension; thus exhibited high foamability and foam stability, and very small and homogeneous air bubbles in foam structure. For all shearing methods, increasing FFA content from 1.5 to 3.5 μ-equiv. mL^-1 markedly decreased the surface tension, foamability, and foam stability of milk samples. The FFA level that led to undesirable foam structure was 1.5 μ-equiv. mL^-1 for ultra-turraxed milk samples and 2.5 μ-equiv. mL^-1 for homogenised and microfluidised ones.

CONCLUSION

Shearing-induced lipolysis greatly affected the physical properties of milk samples and subsequently their foaming properties and foam structure. At the same FFA level, lipolysis induced by microfluidisation was much less detrimental to the foaming properties of milk than lipolysis induced by ultra-turraxing and homogenisation. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of Ultra-High-Pressure Jet Processing on Casein Structure and Curdling Properties of Skimmed Bovine Milk

Ultra-high-pressure jet processing (UHPJ) is a new non-thermal processing technique that can be employed for the homogenization and the sterilization of dairy products. However, the effects on dairy products are unknown when using UHPJ for homogenization and sterilization. Thus, this study aimed to investigate the effects of UHPJ on the sensory and curdling properties of skimmed milk and the casein structure in skimmed milk. Skimmed bovine milk was treated with UHPJ using different pressures (100, 150, 200, 250, 300 MPa) and casein was extracted by isoelectric precipitation. Subsequently, the average particle size, Zeta potential, contents of free sulfhydryl and disulfide bonds, secondary structure, and surface micromorphology were all used as evaluation indicators to explore the effects of UHPJ on the structure of casein. The results showed that with an increase of pressure, the free sulfhydryl group content changed irregularly, while the disulfide bond content increased from 1.085 to 3.0944 μmol/g. The content of α-helix and random coil in the casein decreased, while the β-sheet content increased at 100, 150, 200 MPa pressure. However, treatment with higher pressures of 250 and 300 MPa had the opposite effect. The average particle size of the casein micelles first decreased to 167.47 nm and then increased up to 174.63 nm; the absolute value of Zeta potential decreased from 28.33 to 23.77 mV. Scanning electron microscopy analysis revealed that the casein micelles had fractured into flat, loose, porous structures under pressure instead of into large clusters. After being ultra-high-pressure jet-processed, the sensory properties of skimmed milk and its fermented curd were analyzed concurrently. The results demonstrated that UHPJ could alter the viscosity and color of skimmed milk, shortening curdling time from 4.5 h to 2.67 h, and that the texture of the curd fermented with this skimmed milk could be improved to varying degrees by changing the structure of casein. Thus, UHPJ has a promising application in the manufacture of fermented milk due to its ability to enhance the curdling efficiency of skimmed milk and improve the texture of fermented milk.

Modifying the physicochemical properties, solubility and foaming capacity of milk proteins by ultrasound-assisted alkaline pH-shifting treatment

This study investigated the effects of different treatment of alkaline pH-shifting on milk protein concentrate (MPC), micellar casein concentrate (MCC) and whey protein isolate (WPI) assisted by the same ultrasound conditions, including changes in the physicochemical properties, solubility and foaming capacity. The solubility of milk proteins had a significant increase with gradual enhancement of ultrasound-assisted alkaline pH-shifting (p < 0.05), especially for MCC up to 99.50 %. Also, treatment made a significant decline in the particle size of MPC and MCC, as well as the turbidity of the proteins (p < 0.05). The foaming capacity of MPC, MCC, and WPI was all improved, especially at pH 11, and at this pH, the milk protein also showed the highest surface hydrophobicity. The best foaming capacity at pH 11 was the result of the combined effect of particle size, potential, protein conformation, solubility, and surface hydrophobicity. In conclusion, ultrasound-assisted pH-shifting treatment was found to be effective in improving the physicochemical properties and solubility and foaming capacity of milk proteins, especially MCC, with promising application prospect in food industry.

Optimization of enzymatic hydrolysis of Pleurotus ostreatus derived proteins through RSM and evaluation of nutritional and functional qualities of mushroom protein hydrolysates

Abstract Pleurotus ostreatus (Jacq.) P. Kumm., the second most widely cultivated oyster mushroom was grown on paddy straw, which is cheap and readily available waste material. After harvesting and drying, nutritional, and antinutritional composition of P. ostreatus were estimated using the standard assay methods. Tannin and phytic acid were present in very negligible amount (0.095 ± 0.027 mg/g and 0.150 ± 0.083 mg/g, respectively), whereas oxalate and cyanide were absent in whole mushroom. In fact, P. ostreatus was hydrolysed with commercially available proteinase K, pepsin and trypsin with different concentrations of the enzymes (0.05%, 0.10% and 0.15%), at different temperatures (30 °C, 40 °C and 50 °C) for different time periods (60, 90 and 120 min) to get the mushroom protein hydrolysates. Degree of hydrolysis and protein content varied from 4.29 ± 1.12% to 99.42 ± 0.02% and from 0.25 ± 0.07 mg/mL to 3.22 ± 0.12 mg/mL, respectively. Maximum degree of hydrolysis and the highest protein content of protein hydrolysate was obtained when using 0.15% proteinase K, at 50 °C for 120 minutes. Mushroom protein hydrolysates thus obtained exhibited improved functional characteristics such as foaming capacity, foaming stability and emulsifying property than the unhydrolysed mushroom. Based on the result of the present study, the mushroom protein hydrolysates could be served as useful ingredient for food and nutraceutical applications.

Characterization of high-pressure jet-induced fat-protein complexation

High-pressure jet (HPJ) processing of various dairy systems has been shown to disrupt fat droplets and casein micelles and cause a strong association between fat and casein proteins. The present work seeks to better describe this association between fat and casein using a model milk formulated from confectionary coating fat (3.6% wt/wt), micellar casein (3.4% wt/wt), and water (93% wt/wt), which was then pasteurized, homogenized, and then either HPJ-treated (400 MPa) or not (non-HPJ-treated, control). Upon ultracentrifugation, fat in the non-HPJ-treated model milk creamed due to its low density. In the HPJ-treated model milk, fat precipitated with protein into a thick bottom layer upon ultracentrifugation, reflecting a strong association between protein and fat. Differential scanning calorimetry (DSC) and time-domain nuclear magnetic resonance of the non-HPJ-treated model milk revealed fat in 2 physical states: (1) fat that is physically similar to the bulk fat and (2) fat that was in smaller droplets (i.e., homogenized) and crystallized at a lower temperature than the bulk fat. In contrast, DSC of HPJ-treated model milks supported the presence of fat in 3 states: (1) fat that is physically similar to the bulk fat, (2) fat in small droplets that required substantial supercooling beyond the non-HPJ-treated model milk to crystallize, and (3) fat in such small domains that it crystallizes in a less stable polymorphic form than the non-HPJ-treated model milk (or does not crystallize at all). The state of fat within the HPJ-treated model milk changed minimally with acidification, indicating that the association is not dependent on the charge on the casein. Cryogenic transmission electron microscopy (Cryo-TEM) of the non-HPJ-treated model milk revealed uniform casein micelles, which likely adsorbed to the surface of fat globules post-homogenization. In contrast, Cryo-TEM of the HPJ-treated model milk revealed a porous protein aggregate that likely had dispersed fat throughout. Together, these results suggest that HPJ treatment causes fat to be entrapped by casein proteins in very small domains.

The effect of high-pressure jet processing on cocoa stability in chocolate milk

Fat-free chocolate milk formulations containing skim milk, cocoa powder, and sugar were thermally treated and then processed using high-pressure jet (HPJ) technology from 125 to 500 MPa. The rheological properties and stability of HPJ-treated chocolate milks were compared with controls (no HPJ processing) prepared both with and without added κ-carrageenan. As expected, carrageenan-free chocolate milk exhibited immediate phase separation of the cocoa powder, whereas formulations containing κ-carrageenan were stable for 14 d. An increased stability was observed with increasing HPJ processing pressure, with a maximum observed when chocolate milk was processed at 500 MPa. The apparent viscosity at 50 s^-1 of HPJ-processed samples increased from ~3 mPa·s to ~9 mPa·s with increasing pressure, and shear-thinning behavior (n < 0.9) was observed for samples processed at HPJ pressures ≥250 MPa. We suggest that HPJ-induced structural changes in casein micelles and new casein-cocoa interactions increased cocoa stability in the chocolate milk. Because casein seemed to be the major component enhancing cocoa stability in HPJ-treated samples, a second study was conducted to determine the effect of additional micellar casein (1, 2, or 4%) and HPJ processing (0-500 MPa) on the stability of fat-free chocolate milk. Formulations with 4% micellar casein processed at 375 and 500 MPa showed no phase separation over a 14-d storage period at 4°C. The addition of micellar casein together with HPJ processing at 500 MPa resulted in a higher apparent viscosity (~17 mPa·s at 50s^-1) and more pronounced shear-thinning behavior (n ≤ 0.81) compared with that without added micellar casein. The use of HPJ technology to improve the dispersion stability of cocoa provides the industry with a processing alternative to produce clean-label, yet stable, chocolate milk.

Functionality of bovine milk proteins and other factors in foaming properties of milk: a review

For many dairy products such as cappuccino-style beverages, the top foam layer determines the overall product quality (e.g. their appearance, texture, mouthfeel and coffee aroma release rate) and the consumer acceptance. Proteins in milk are excellent foaming agents, but the foaming properties of milk are greatly affected by several factors such as the protein content, ratio of caseins to whey proteins, casein micelle size, pH, minerals, proteolysis, presence of low molecular weight compounds (lipids and their hydrolyzed products) and high molecular weight compounds (polysaccharides); milk processing conditions (e.g. homogenization, heat treatment and aging); and foaming method and temperature. These factors either induce changes in the molecular structure, charge and surface activity of the milk proteins; or interfere and/or compete with milk proteins in the formation of highly viscoelastic film to stabilize the foam. Some factors affect the foamability while others determine the foam stability. In this review, functionality of milk proteins in the production and stabilization of liquid foam, under effects of these factors is comprehensively discussed. This will help to control the foaming process of milk on demand for a particular application, which still is difficult and challenging for researchers and the dairy industry.

Freezing kinetics and microstructure of ice cream from high-pressure-jet processing of ice cream mix

The effect of high-pressure-jet (HPJ) processing (0-500 MPa) on low-fat (6% fat) ice cream was studied by evaluating physiochemical properties before freezing, during dynamic freezing, and after hardening. An HPJ treatment ≥400 MPa decreased the density, increased the apparent size of colloidal particles, and altered rheological behavior (increased non-Newtonian behavior and consistency coefficients) of low-fat ice cream mix before freezing. During dynamic freezing, the particle size and consistency coefficient decreased but remained higher in 400 MPa-treated samples vs. non-HPJ-treated controls at the conclusion of freezing. The resulting ice creams (400 and 500 MPa-treated) had similar hardness values (3,372 ± 25 and 3,825 ± 14 g) and increased melting rates (2.91 ± 0.13 and 2.61 ± 0.31 g/min) compared with a control sample containing polysorbate 80 (3,887 ± 2 and 1.62 ± 0.25 g/min). Visualization of ice cream samples using transmission electron microscopy provided evidence of casein micelle and fat droplet disruption by HPJ treatment ≥400 MPa. In the 400 MPa-treated samples, a unique microstructure consisting of dispersed protein congregated around coalesced fat globules likely contributed to the altered physiochemical properties of this ice cream. High-pressure-jet processing can alter the microstructure, rheological properties, and hardness of a low-fat ice cream, and further modification of the formulation and processing parameters may allow the development of products with enhanced properties.

Effect of high-pressure-jet processing on the physiochemical properties of low-fat ice cream mix

The objective of this study was to use high-pressure-jet (HPJ) processing to produce functional properties in a low-fat (4.5% fat) ice cream mix similar to those seen when emulsifiers are used. Ice cream mix or serum (nonfat portion of the ice cream mix) were subjected to 200 or 400 MPa HPJ processing and compared with a non-HPJ-treated control. A similar non-HPJ-treated formulation but containing polysorbate 80 (0.075% wt/wt) was also used as a control. The mix samples were characterized in terms of their particle size, density, flow properties, stability, crystallization kinetics, and fat-protein interactions. The sample from the mix subjected to 400 MPa HPJ processing (HPJ-M-400) had increased consistency coefficient (5°C; 228 ± 102.7 mPa·s) and particle size (D[4,3]; 16.0 ± 2.5 μm) compared with the non-HPJ-treated control sample, with viscosity and particle size (volume-moment mean diameter, D[4,3]) values of 7.5 ± 0.4 mPa·s and 0.50 ± 0.1 μm, respectively. These differences were attributed to an increase in casein-fat interactions and casein-casein interactions caused by the 400 MPa HPJ treatment, which were observed using confocal scanning laser microscopy and inferred from an increase in protein and fat concentrations in the sediment after ultracentrifugation. Interestingly, the density of HPJ-M-400 was also lower (0.79 ± 0.17 g/mL) than that of the control (1.04 ± 0.00 g/mL) because bubbles were trapped within these complexes. The large casein-fat complexes formed in the HPJ-M-400 sample also appeared to act as steric barriers that slowed ice crystal growth during quiescent freezing. The alterations in physiochemical properties and apparent ice crystal growth induced by the 400 MPa treatment of low-fat ice cream mix have many potential applications, including clean-label confections.