Investigating the effect of temperature on the formation and stabilization of ovalbumin foams

Novel organic-inorganic composite pea protein silica food-grade aerogel materials: Fabrication, mechanisms, high oil-holding property and curcumin delivery capacity

The fragility of the skeleton and poor bioaccessibility limit Silica aerogel's application in the food industry. In this study, composite gels were obtained by cross-linking pea proteins isolate (PPI) with Tetraethoxysilane (TEOS)to improve the bioavailability of silica-derived aerogels. It indicated that TEOS first condensed with H+ to form secondary particles and then complexed with PPI via hydroxyl groups to form a composite aerogel. Meanwhile, the PPI-Si composite aerogel formed a dense mesoporous structure with a specific surface area of 312.5 g/cm3. This resulted in a higher oil holding percentage of 89.67 % for the PPI (10 %)-Si aerogel, which was 34.1 % higher than other studies, leading to a more stable oleogel. Finally, as a delivery system, the composite oleogel not only could significantly increase the bioaccessibility rate by 27.4 % compared with silica aerogel, but also could efficiently inhibit the premature release of curcumin in the simulated gastric fluids, while allowed sustainably release in the simulated intestinal fluids. These results provided a theoretical basis for the application of silica-derived aerogels in food and non-food applications.

Tilapia head gelatins to stabilize fish oil emulsions and the effect of extraction methods

The preparation and use of gelatins from fish by-products have attracted much attention in the field of food science. Herein, four types of tilapia head gelatins were extracted and characterized: hot water-pretreated gelatin (HWG), acetic acid-pretreated gelatin (AAG), sodium hydroxide-pretreated gelatin (SHG), and pepsin enzyme-pretreated gelatin (PEG). The gel strength values followed the order: PEG (74 ± 1 Bloom) > AAG (66 ± 1) > HWG (59 ± 1) > SHG (34 ± 1). The foaming properties, fish oil emulsion viscosity, emulsion activity, and emulsion stabilization ability followed this order: PEG > HWG ≥ AAG > SHG. The effect mechanisms of extraction methods and gelatin concentrations on the emulsion stability involved the interfacial tension, emulsion viscosity, and fat-binding capacity. This work provided important knowledge for analyzing the relations between the structure and function of gelatin. It also provided a high-value application method of fish wastes.

Investigating the effects of ultrafine bubbles on bacterial growth

Several previous studies have considered ultrafine bubbles as a potential research target because their properties can be applied in many different research areas. In particular, the interaction between UFBs and microorganisms has always been one of the aspects that receives much attention due to the high difficulty in controlling a living system. The properties of UFBs, as mobile air-water interfaces, are greatly determined by their gas cores which play a critical role in regulating microbial growth. This study aims to investigate the effects of ultrafine bubbles on bacterial growth. Two well-studied organisms were chosen as models - Escherichia coli and Staphylococcus aureus. Their growing behavior was examined based on the growth rate, phenotype and biomass. Three types of Luria-Bertani cultures were tested, including a standard culture containing distilled water, an air ultrafine bubble culture, and a hydrogen ultrafine bubble culture. The UFBs were generated via ultrasonic cavitation and stabilized by 50 μM SDS, which was proven to have negligible effects on bacterial growth. By comparing among the three cultivation conditions, the bacterial growth rates were observed to be the highest in exposure to HUFBs. The results also signified that UFBs had an enhancement on cell proliferation. On the other hand, while proposing an increase in cell density, bacteria cultured in HUFB media have their sizes decreased uniformly and significantly (p-value < 0.05). This study confirmed that bacterial growth was promoted by UFBs; and better effects recorded were due to the HUFB present in the culture media. However, the average morphological size of bacteria was in negative correlation with their population size.

Effect of Temperature, Pressure, and Type of Gas Injected on the Formation and Decay of Mineral Oil-Based Foams

In three-phase gravity separators used in gas and oil production, foaming can occur by either depressurization or injection of gas in the equipment. This formed foam can be harmful, causing various problems such as liquid carry-over, gas carry-under, decreased capacity, and difficulty in level measurement. The mechanism of foam formation by gas injection in separators motivated the present study. Thus, this work proposes the analysis of the influence of certain physical-chemical parameters such as temperature (20-40 °C), pressure (1-10 bar), and types of gases (nitrogen and methane) on the formation of the column and stability of the foam formed, in ISO14 mineral oil + sodium laureth sulfate + water, through gas injection in separator conditions. To carry out this analysis, an experimental apparatus was designed and assembled consisting of a transparent foam formation cell of 0.5 m height and 5 cm internal diameter. Parameters such as foamability, foaminess, and the collapse curve were also evaluated to characterize the foam formed. In addition, simplified models of foam formation and decay by gas injection were proposed based on models already available in the literature, which were validated with the experimentally obtained results. The experimental results showed good agreement when compared to the literature, referring to the behavior of temperature (higher temperature, lower stability), pressure (higher pressure, higher stability), and type of injected gas (dependency on solubility). In addition, maximum errors of 26% (in height) and 11% (decay phase) were obtained for the formation and decay models, respectively.

Variations in foam collapse and thin film stability with constant interfacial and bulk properties

The stability of foams is commonly linked to the interfacial properties of the proteins and other surfactants used. This study aimed to use these relationships to explain differences in foam stability observed among similar beer samples from different breweries. The foam stability was different for each sample (Nibem foam stability ranged from 206 to 300 s), but ranking was similar for all three foaming methods used, thus independent of the method, gas, etc. Differences in foam stability were dominated by differences in coalescence, as illustrated by the correlation with the stability of single bubbles and thin liquid films. The differences in coalescence stability could not be explained by the measured interfacial properties (e.g. surface pressure, adsorption rate, dilatational modulus and surface shear viscosity), or the bulk properties (concentration, pH, ionic strength, viscosity), since they were similar for all samples. The drainage rates and disjoining pressure isotherms measured in thin liquid films were also similar for all samples, further limiting the options to explain the differences in foam stability using known arguments. The differences in coalescence stability of the thin films was shown to depend on the liquid in between the adsorbed layers of the thin film, using a modified capillary cell to exchange this liquid (to a buffer, or one of the other samples). This illustrates the need to review our current understanding and to develop new methods both for experimental study and theoretical description, to better understand foam stability in the future.

Succinylation Modified Ovalbumin: Structural, Interfacial, and Functional Properties

In this study, ovalbumin (OVA) was succinylated with the addition of different levels of succinic anhydride, and the structural and functional properties of succinylated OVA (SOVA) were investigated. SDS−PAGE and FTIR spectrum confirmed the covalent attachment of the succinyl group to OVA. Thermal stability and the absolute value of zeta potential (pH 6.0) of SOVA were enhanced by 14.90% and 76.77% higher than that of the native OVA (NOVA), respectively. Circular dichroism (CD) spectra demonstrated that the succinylation decreased the α−helix and increased β−sheet content to 21.31% and 43.28%, respectively. The content of free sulfhydryl groups increased and intrinsic fluorescence spectra suggested the SOVA became more unfolded and flexible as the degree of succinylation enhanced. Furthermore, succinylation effectively enhanced the solubility and decreased the interface tension (oil−water and air−water interface) of OVA. Compared to NOVA, the emulsifying activity and stability of SOVA were increased by 1.6 times and 1.2 times, respectively, and foaming capacity and stability were enhanced by 2.7 times and 1.5 times, respectively.

Hydrophobicity Enhances the Formation of Protein-Stabilized Foams

Screening proteins for their potential use in foam applications is very laborious and time consuming. It would be beneficial if the foam properties could be predicted based on their molecular properties, but this is currently not possible. For protein-stabilized emulsions, a model was recently introduced to predict the emulsion properties from the protein molecular properties. Since the fundamental mechanisms for foam and emulsion formation are very similar, it is of interest to determine whether the link to molecular properties defined in that model is also applicable to foams. This study aims to link the exposed hydrophobicity with the foam ability and foam stability, using lysozyme variants with altered hydrophobicity, obtained from controlled heat treatment (77 °C for 0-120 min). To establish this link, the molecular characteristics, interfacial properties, and foam ability and stability (at different concentrations) were analysed. The increasing hydrophobicity resulted in an increased adsorption rate constant, and for concentrations in the protein-poor regime, the increasing hydrophobicity enhanced foam ability (i.e., interfacial area created). At higher relative exposed hydrophobicity (i.e., ~2-5 times higher than native lysozyme), the adsorption rate constant and foam ability became independent of hydrophobicity. The foam stability (i.e., foam collapse) was affected by the initial foam structure. In the protein-rich regime-with nearly identical foam structure-the hydrophobicity did not affect the foam stability. The link between exposed hydrophobicity and foam ability confirms the similarity between protein-stabilized foams and emulsions, and thereby indicates that the model proposed for emulsions can be used to predict foam properties in the future.

Effect of germination, roasting, and variety on physicochemical, techno-functional, and antioxidant properties of chickpea (Cicer arietinum L.) protein isolate powder

Chickpeas are a very important part of the human diet due to their nutritional and bioactive composition. Ethiopia is one of the top chickpea producers and consumers of chickpea-based products daily. However, limited studies were conducted on the effect of common processing methods, roasting and germination, on techno-functional and nutritional properties of chickpea protein isolates. Two varieties of chickpea, Arerti (Kabuli type) and Natoli (Desi type), were selected and treated with different roasting temperature (150 and 180 °C) and germination time (24, 48, and 72 h). The protein was isolated with alkaline-solubilization followed by isoelectric precipitation. Freeze-dried isolates were investigated for proximate composition, techno-functional properties, antioxidant properties, and antinutritional content. Chickpea protein isolates (CPIs) mean protein content was between 79.72 and 87.43%, comparatively lower for those from roasted and higher for those from germinated chickpea. Mean values of CPIs’ water holding capacity (WHC), oil holding capacity (OHC), protein solubility (PS), foaming capacity (FC), and Emulsifying capacity (EC) for both varieties were in a range of 1.07–2.47 g/g, 1.40–2.21 g/g, 43.88–69.99%, 14.00–94.00%, and 56.44–84.16%, respectively. Roasting at 150 °C improved most of the techno-functional properties (WHC, OHC, PS, and FC) while roasting at 180 °C negatively affected almost all the techno-functional properties. Both heat treatments significantly increased the antioxidant properties of the isolates. Germination for 72 h was the best treatment in improving all antioxidant properties. CPIs from treated chickpea had lower antinutritional content than those from native chickpea except for phytate on Natoli variety where no statistical difference (p > 0.05) was observed. The finding showed that based on the intended use the different techno-functional properties of the isolates can be altered by applying those treatments. Proximate, techno-functional, antioxidant, and antinutritional characters indicated that CPIs can be a good ingredient for the food industry to formulate functional foods.

Preparation of Acyclovir-Containing Solid Foam by Ultrasonic Batch Technology

In recent years, the application of solid foams has become widespread. Solid foams are not only used in the aerospace field but also in everyday life. Although foams are promising dosage forms in the pharmaceutical industry, their usage is not prevalent due to decreased stability of the solid foam structure. These special dosage forms can result in increased bioavailability of drugs. Low-density floating formulations can also increase the gastric residence time of drugs; therefore, drug release will be sustained. Our aim was to produce a stable floating formula by foaming. Matrix components, PEG 4000 and stearic acid type 50, were selected with the criteria of low gastric irritation, a melting range below 70 °C, and well-known use in oral drug formulations. This matrix was melted at 54 °C in order to produce a dispersion of active substance and was foamed by different gases at atmospheric pressure using an ultrasonic homogenizer. The density of the molded solid foam was studied by the pycnometer method, and its structure was investigated by SEM and micro-CT. The prolonged drug release and mucoadhesive properties were proved in a pH 1.2 buffer. According to our experiments, a stable foam could be produced by rapid homogenization (less than 1 min) without any surfactant material.

Study on structural, rheological and foaming properties of ovalbumin by ultrasound-assisted glycation with xylose

This study was to evaluate the effect of ultrasound-assisted glycation with xylose on the foaming properties, physicochemical and structural characteristics of ovalbumin (OVA). The number of free amino groups in the glycated OVA (sOVA-X) significantly decreased with the increase of treatment time. The results obtained by circular dichroism (CD) and spectrofluorimetric measurements showed that there were slight changes on the subunits and secondary structure of OVA, indicating that the tertiary structure became more flexible and loose after the sonicated glycation treatment. The glycated OVA had higher solubility and foaming properties than the untreated samples. Therefore, ultrasound improved the glycation extent, and the changes in molecular structure were responsible for their different foaming ability and foaming stability. Our study also provided principle knowledge to understand how the viscosity and rheology were related to the foaming properties of OVA glycation by xylose. The results indicated that ultrasound-assisted glycation could be an excellent approach to improve the functional properties of OVA and promote its application in food industry.

Separation of Protein-Binding Anthraquinones from Semen Cassiae Using Two-Stage Foam Fractionation

Anthraquinones are compounds of high medicinal value in many plants. Based on their good protein binding affinity, foam fractionation was attempted to separate them using proteins in the aqueous extract of Semen Cassiae as collectors. Firstly, the interaction between anthraquinones and Semen Cassiae proteins has been analyzed by the Stem–Volmer equation with physcion as a standard. The results show that physcion had good interaction with the proteins via hydrophobic forces. More importantly, the proteins effectively assisted the foam fractionation of several anthraquinones including aurantio-obtusifolin, aloe-emodin, rhein, emodin, chrysophanol, and physcion. On this basis, a two-stage foam fractionation technology was developed for process intensification using a foam fractionation with vertical sieve trays (VSTs). VSTs, initial feed concentration of total anthraquinones, temperature, volumetric air flow rate and pore diameter of gas distributor had significant effects on enrichment ratio and recovery yield of anthraquinones. Under suitable conditions, the enrichment ratio of total anthraquinones reached 47.0 ± 4.5 with a concentration of 939 ± 94 mg/L in the foamate while their total recovery percentage reached more than 47.7%. In addition, foam fractionation also increased the purity and hydroxyl radical scavenging activity of total anthraquinones. The results had significant implications for the separation of anthraquinones from Semen Cassiae.