Effect of a novel drying method based on supercritical carbon dioxide on the physicochemical properties of sorghum proteins

The aim of this research was to use supercritical carbon dioxide (SC-CO2) drying as a novel approach for generating sorghum protein concentrates/isolates with enhanced functional properties. Sorghum protein extracts were obtained from white whole-grain sorghum flour and were dried by two methods, namely, freeze-drying and SC-CO2 drying. The collected proteins were characterized for their morphology, color, crystallinity, surface hydrophobicity, emulsifying activity index (EAI), creaming index (CI), foaming capacity (FC), foaming stability (FS), protein solubility, chemical interactions, and viscosity. The SC-CO2-dried proteins exhibited higher porosity compared to the freeze-dried ones with smaller particle sizes (∼5.1 vs. 0.4 μm, respectively). The XRD patterns indicated that the SC-CO2-dried proteins had a lower crystallinity than the freeze-dried proteins. However, the surface hydrophobicities of the freeze-dried and SC-CO2-dried proteins were similar. The EAI results showed that the emulsifying activity of freeze-dried protein powder (40.6) was better than that of SC-CO2-dried protein powder (29.8). Nevertheless, the solubility of SC-CO2-dried proteins was higher than that of freeze-dried proteins in most of the pHs investigated. Overall, the proposed SC-CO2 drying method has the potential to generate porous protein powders with improved solubility that can be used in developing functional foods.

Pea and Soy Protein Stabilized Emulsions: Formulation, Structure, and Stability Studies

During the last decades, there has been a huge consumer concern about animal proteins that has led to their replacement with plant proteins. Most of those proteins exhibit emulsifying properties; thus, the food industry begins their extensive use in various food matrices. In the present study, pea and soy protein isolates (PPI and SPI) were tested as potential candidates for stabilizing food emulsions to encapsulate α-tocopherol and squalene. More specifically, PPI and SPI particles were formulated using the pH modification method. Following, emulsions were prepared using high-shear homogenization and were observed at both a microscopic and macroscopic level. Furthermore, the adsorption of the proteins was measured using the bicinchoninic acid protein assay. The emulsions’ droplet size as well as their antioxidant capacity were also evaluated. It was found that the droplet diameter of the SPI-based emulsions was 60.0 μm, while the PPI ones had a relatively smaller diameter of approximately 57.9 μm. In the presence of the bioactives, both emulsions showed scavenging activity of the 2,20-Azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical cation (ABTS·+) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals, with the ones loaded with α-tocopherol having the greatest antioxidant capacity. Overall, the proposed systems are very good candidates in different food matrices, with applications ranging from vegan milks and soups to meat alternative products.

Determination of the best interaction of inulin with different proteins by using interfacial rheology: the relationship with the emulsion activity and stability in emulsion systems

This study aimed to develop functional emulsions with dietary fibre/proteins and to examine the role of interfacial rheological properties on the emulsion stability. Emulsions with inulin and various animal/vegetable proteins were prepared, and their emulsifying and interfacial rheological properties were appraised for their possible applications in stabilizing oil-in-water emulsions. Interfacial measurements including the frequency, time and strain sweep test were determined depending on the protein differences. The results revealed that the adsorption behaviour of proteins at the two interfaces was quite different. The apparent viscosity (η 50) of the emulsions ranged between 0.006 and 0.037 Pa s. The highest interfacial viscosity (η i) values at low shear rates were determined in the mixture of egg protein-inulin at the oil/water interface. In particular, the interfacial properties of egg protein were not similar to those of other proteins. This study indicated that interfacial rheological properties and emulsifying properties of the proteins were influenced by the presence of inulin which contributes to the existing body of knowledge on the preparation of the prebiotic emulsions with proteins.

High internal phase oil-in-water emulsions stabilized by supercritical carbon dioxide extruded whey protein concentrate

High Internal Phase Emulsions (HIPEs) were stabilized by functionalized whey protein concentrate (WPC-80). Functionalization of WPC-80 was done by supercritical CO₂ assisted extrusion technology. HIPEs were formed by 80% oil and 1-4 wt% of control (untreated) whey protein concentrate, extruded/functionalized whey protein concentrates (f-WPC-80) at pH 3.0 and 5.4, and sodium caseinate (NaCas) separately and were characterized for their stability at two temperatures (25 and 40 °C) for 20 days. Results indicated that f-WPC-80-pH3.0 formed self-standing gels at 1 wt% concentrations which were more stable, without phase separation, than those stabilized by commercially used stabilizer NaCas and native c-WPC. At 4% concentration of f-WPC-80-pH3.0, the compressed droplets produced emulsions with self-standing and viscoelastic features. While control WPC-80, could not form stable HIPEs at any investigated concentrations. The reported high internal phase oil-in-water emulsions, offer a potential new system for delivery of nutritionally superior and clean-label products of commercial utility.

Electrical conductivity: A simple and sensitive method to determine emulsifying capacity of proteins

Emulsifying capacity (EC) of proteins is a benchmark standard widely used to evaluate the quality of protein ingredients in emulsion foods. EC (mL of oil emulsified per g of protein) is usually measured by a sudden drop in electrical resistance (phase transition) with the continuous addition of oil to a specific protein solution. However, little is known about electrochemical mechanisms behind this process because resistance, measured with an ohmmeter, is not sensitive enough to monitor changes in the concentration of protein electrolytes. Here, pea (PPI), myofibrillar (MPI), and whey (WPI) protein isolates were vigorously homogenized with oil at a series of oil/protein ratios to prepare emulsions with different final protein concentrations. The conductivity was closely monitored using a conductivity meter. A linear relationship was discovered between conductivity and the final protein concentrations. At higher oil fractions, the migration of proteins from the aqueous phase to the oil-water interface limited protein mobility, leading to a conductivity drop. EC was calculated from the regression lines; when the starting protein concentration was raised from 0.5% to 2.0%, the EC of PPI, MPI, and WPI decreased from 717, 782, 1339 to 219, 303, and 540 mL oil/g protein, respectively. The dependence of EC on the initial protein concentration and the sensitivity of conductivity to the depleting protein electrolytes suggest that protein concentration is an important factor to consider when determining EC for a given protein or comparing EC among different proteins. PRACTICAL APPLICATION: The simple and sensitive electrical conductivity test described in this paper allows for the accurate determination of emulsifying capacity of proteins. It may be adopted by the food industry to compare the emulsifying properties of different protein ingredients.

Rendering waste oil as a new source for the synthesis of emulsifier: optimization, purification, and characterization

The enzymatic glycerolysis conditions in the production emulsifier by using the rendering waste oil were optimized in the present study. The effects of changes in duration (1–27 h), temperature (50–80 °C), enzyme (5–20%), and glycerol (5–20%) concentration, addition of solvent (acetone, acetonitrile, chloroform, methanol, ethanol, and tert-butanol) and water addition (3.5% of glycerol rate), and ultrasound application on the enzymatic glycerolysis reaction medium for mono- and diglyceride production were investigated. After determining the optimum conditions, the effects of the ultrasonic bath on the physic-chemical and rheological properties of emulsifier, the oxidation tests were examined. Using the preparative column chromatography method, three different emulsifier compositions were achieved and named E100, E50-50, and E50-40-10 by their monoglyceride, diglyceride, and triglyceride contents, respectively. Then, the post-purification emulsion properties and rheological behaviors of emulsifier samples were determined. E50-40-10 emulsifier was found to be the best sample in terms of rheological properties and emulsion stability.

Comparison Study between Batch and Continuous Processes to Obtain Chitosan-Based High Porous Biomaterial for Biological Applications

Foaming process can be monitored under batch or continuous flows conditions. In the batch process, foaming is time-dependent and the foaming efficiency is controlled by the operator. On the other hand, in the continuous process, the foaming efficiency is only monitored by gas and liquid flow rates. The aim of this work is to compare the two technologies to perform porous scaffold biomaterial based on chitosan (a biocompatible polysaccharide) as well as calcium (Ca2+) and silica (SiO2) (two osteogenesis compounds). Diverse recipes using chitosan (CS) solution (2% (w/v)) in acetic acid (1% (v/v in distilled water)) mixed with whey protein isolate (WPI) (2% (w/v)) as natural surfactant were studied. They were supplemented or not by hydroxyapatite powder (HAp) and tetraethyl orthosilicate (TEOS). A jacketed narrow annular gap unit (NAGU) was used to perform the continuous foaming process. For all experimentations, the mixture flow rate was maintained at 30 mL min-1. The influence of operating conditions such as gas and liquid flow rates was studied to obtain foams and final scaffold material with different densities and porosities. Some other recipes followed foaming under batch conditions. Generally, the recipes were placed in a vessel under mixing allowing the gas phase to come from the roof of the vessel. In this case, it becomes very difficult to control the density and the size distribution of bubbles in the final product. In both cases, liquid foams were analysed (density, bubble size distribution) and then freeze-dried for mechanical and porosity investigations using the dynamic mechanical analysis (DMA) system and scanning electron microscopy (SEM). It has been shown that the controlled injected gas affected the continuous phase, resulting in a lighter and higher porous structure, a more homogeneous appearance, and a more uniform distribution of osteogenesis components compared to one obtained using batch operation. The obtained porous materials exhibited good properties (porosity, interconnectivity, and good HAp and silica distribution) and potential for future bone regeneration applications.

Effect of different homogenisation methods and UHT processing on the stability of pea protein emulsion

Pea protein is a very popular source of edible plant-based protein among legumes. In this study, the stability of ultra high temperature (UHT) processed pea protein emulsion prepared from 0.5 and 1.0% (w/v) pea protein concentrate (PPC) by two different homogenisation methods of microfluidisation (500 Bar) and ultrasonication (ultrasonicated for 1, 3 and 5 min) was investigated. In addition, the emulsion properties (particle and droplet size, flocculation, coalescence, zeta potential, hydrophobicity and creaming index) of PPC emulsions before and after UHT treatment were measured. The overall heat transfer coefficient (OHTC) versus time graphs were stable during UHT processing for both microfluidised and ultrasonicated PPC emulsions that indicates no fouling and good stability under the thermal treatment condition. Freshly prepared emulsion using 0.5 and 1.0% PPC and ultrasonicated for 5 min showed creaming index of 5.73 and 8.39%, particle size of 0.96 and 1.53 μm respectively. In addition, the fat droplet size for the above samples measured 1.05 and 1.85 μm for larger fat droplets and 0.51 and 0.72 μm for smaller fat droplets, respectively. However, after UHT treatment this emulsion destabilised due to protein aggregation as indicated by the high flocculation index (13.22 and 103.35%), particle size (1.59 and 3.23 μm) and droplet size (1.30 and 2.53 μm, for large fat droplets and 0.90 and 1.22 μm, for small fat droplets). After UHT treatment the microfluidised PPC emulsion using 0.5 and 1.0% PPC were the most stable with small particle size (2.85 and 0.36 μm), high zeta potential (-56.36 and - 27.30) and low creaming index (3.87% and 4.97%), respectively as compared to ultrasonicated samples. Overall, this study revealed that UHT treatment improved emulsion properties of the microfluidised PPC emulsion compared to the ultrasonicated PPC emulsion.

Calcium effects on the functionality of a modified whey protein ingredient

The primary objective for this study addressed the effects of supplemental calcium on the functional properties of a modified whey protein ingredient (mWPC), prepared by acidification to pH 3.35, followed by extended heat treatment, gelation, and spray drying. In the presence of added calcium (mWPC-Ca2+), protein solutions showed increased thickening capacity, especially under refrigeration temperatures, compared to dispersions made with mWPC alone. A rheological assessment included the determination of (i) power law parameters, (ii) viscoelastic properties, and (iii) the effects of heating and cooling on these protein systems. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) banding profile suggested that various disulfide-linked molecular forms of beta-lactoglobulin, bovine serum albumin, and immunoglobulin were likely formed during manufacturing of the mWPC ingredient based on the patterns obtained when electrophoresis was performed in the absence of beta-mercaptoethanol compared to those observed with commercial WPC samples. An enhanced water-holding capacity was measured in mWPC-Ca2+ dispersions. Differential scanning calorimetry established that the addition of calcium salts caused a 2-fold increase in the amount of bound or unfreezeable water compared to mWPC controls. The physical appearance of the network structure varied significantly upon visualization with scanning electron microscopy, in which case the formation of large, rounded, spherical structures was noted in mWPC-Ca2+ samples, ascribed to an increased surface tension caused by the higher salt content. Ultimately, such attributes may afford distinct advantages for whey-based ingredients intended for application within food systems, especially under cold processing conditions.

Influence of Processing on Functionality of Milk and Dairy Proteins

The inherent physical functionality of dairy ingredients makes them useful in a range of food applications. These functionalities include their solubility, water binding, viscosity, gelation, heat stability, renneting, foaming, and emulsifying properties. The suitability of dairy ingredients for an application can be further tailored by altering the structure of the proteins using appropriate processes. The processes discussed include physical modification (heat treatment, acidification, addition of mineral slats, homogenization, and shear), enzymatic modification (renneting, hydrolysis, and transglutamination), and chemical modification (use of chemical agents and the Maillard reaction). Emerging food processes (high pressure and ultrasound) are also discussed. The challenges for using dairy ingredients for the delivery of nutrients and bioactive components, while maintaining physical functionality, are also highlighted. There is a need for continued research into the fundamental aspects of milk proteins and their responses to various stresses for further differentiation of milk products and for the delivery of ingredients with consistent quality for target applications.

Variation of saturated surface density of ovalbumin on bubble surface in continuous foam separation

The adsorption of ovalbumin (OA) onto the bubble surfaces was studied with various pHs (3.5, 4.6, 6.0 and 8.0) by a continuous foam separation technique. From the value of the saturated surface density of adsorbed OA, the variation of effective diameter (D) of an OA molecule on the bubble surface was estimated for various pHs (3.5, 4.6, 6.0 and 8.0) of the OA solutions, assuming that the cross section of the OA molecules be circular and that the OA molecules adsorb on the bubble surface in a closest packing structure. The estimated variation of D with pH was attempted to explain based on a model modified from that proposed by Pujar and Zydney. The modified model could well reproduce the variation of the effective diameter with pH; the values of D calculated on the basis of the modified model almost agreed with that estimated from the saturated surface density in the present experimental pH range. From these, conclusion was drawn that the modified model presented in this study can express the variation in the effective diameter with pH.