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The effect of microwaves (MWs) and/or ultrasound (US) to assist alkaline extraction of peanut proteins was evaluated. Isolate extraction yields and purities were obtained as well as functional properties (water solubility and retention, fat absorption, nitrogen solubility, emulsifying activity, and foam activity and stability), in vitro digestibility, free amino nitrogen (FAN), microstructure and secondary structure. In MW-assisted treatments, power (145, 290, 435, 580, and 725 W) and time (2, 4, 6, 8, and 10 min) were evaluated, whereas in US-assisted assays, amplitude (20/100%) and time (15/40 min) were varied. For MW-assisted extraction, 725 W and 8 min yielded an extraction of 55% (100% purity), i.e., 77% more protein when compared with the control, while for US, an increase of 136% and purity of 86% was reached (100% amplitude and 15 min). The sequential use of both technologies was also evaluated, but a synergistic effect in protein extraction was not observed. In terms of functional properties, fat absorption index remained the same for both treatments whereas water absorption, foam activity, emulsifying activity (for MW), and in vitro digestibility (for MW only) improved. In the case of free amino nitrogen, a reduction of 50% for assisted peanut protein isolates was observed. Microstructure was not different among treatments, but secondary structure did change: β-sheet and nonordered structures were higher for experimental treatments compared with the traditional alkaline isolate (up to 8 and 4%, respectively). The use of MW and US favored peanut protein extraction for production of high purity isolates.

The overall goal of this research was to develop plant protein-based lipid composite films by examining the effect of shear (mechanical shear; MS vs. high pressure shear; HPS) and type of legume protein isolates (pea, lentil, soy, and faba bean). Compared to MS, HPS emulsions had smaller droplet size, and HPS emulsions from pea and lentil were more viscous than soy and faba bean. The HPS films were lighter and more green and yellow in colour compared to MS films. HPS also improved the mechanical properties of the films resulting in higher tensile and puncture strength for pea and soy and higher tensile elongation and puncture deformation for most of the legumes. There was an inverse relationship between legumes where overall stronger and less flexible films were prepared from pea and soy, and vice versa from lentil and faba bean. HPS resulted in pea and soy films with less swelling ability and higher water vapour permeability (WVP), indicative of a poorer moisture barrier when homogenized this way. The MS films had similar WVP regardless of legume type, while under HPS it was the lowest for faba bean and highest for soy, despite the high swelling ability for both legumes. In short, pea, lentil, and faba bean protein isolates prepared emulsion films with good mechanical properties and water resistance, suggesting the potential to replace soy as edible packaging materials. HSP films had better mechanical attributes but poorer vapor barrier properties then those produced using MS.

Peanut protein isolate (PPI) solutions were modified by dielectric barrier discharge (DBD) cold plasma (CP) treatment. Effects of CP treatment on the solubility, emulsion stability, and water holding capacity (WHC) of peanut protein were studied. The results showed a significant improvement in solubility, emulsion stability, and WHC following CP treatment. CP treatment resulted in the unfolding of PPI structure, thereby increasing the β-sheet and random coil content and decreasing the α-helix and β-turn content, as analyzed by Fourier-transform infrared spectroscopy. Low-field nuclear magnetic resonance showed an increase in the peak area of T 21 relaxation time by CP treatment and the change in T 21 peak area was in agreement with the result of WHC. This study demonstrated that CP may be successfully applied as a method to modify the functionality of PPI.

Lupin Protein Isolates (L) are considered as promising ingredients. The effects of different solvent extractions of un-defatted (L-U), hot (L-HD) and cold (L-CD) lupin flour on the physicochemical, functional and structural parameters were determined. Hot defatting increased the protein yield and the purity, and increased the particle size, while cold defatting decreased the particle size of lupin isolates. Regarding the amount of free sulfhydryl groups, hot defatting allowed a reduction in free sulfhydryl groups and an increase in the amount of disulfide bridges. Hot and cold defatting resulted in a remarkable decrease in the maximum fluorescence intensity of lupin protein isolates. Regarding the secondary structure determined by mid-infrared, all protein isolates showed similar behavior, although some differences are observed. Hot defatting promoted a significant increase in β-sheet and a decrease in β-turn and aggregates A2 levels. In terms of functionality, L-CD and L-HD behaved fundamentally differently from L-U. Hot defatting leads to protein isolates with improved functional profiles in emulsifying stability index and cold defatting improves significantly solubility, oil adsorption capacity and emulsifying activity index.

Hempseed protein has become a promising candidate as a future alternative protein source due to its high nutritional value. In the current study, hempseed protein isolate (HPI) was obtained using ultrasonic-assisted extraction with the aim to improve the functionality of HPI via protein structure modification. The solubility of HPI could be improved twofold under 20 kHz ultrasound processing compared to conventional alkaline extraction-isoelectric point precipitation. The protein solubility was gradually enhanced as the ultrasonic power improved, whereas excessive ultrasound intensity would cause a decline in protein solubility. Ultrasonic processing was found to have beneficial effects on the other functionalities of the extracted HPI, such as emulsifying and foaming properties. This improvement can be ascribed to the physical effects of acoustic cavitation that changed the secondary and tertiary structures of the protein to enhance surface hydrophobicity and decrease the particle size of the extracted protein aggregates. In addition, more available thiols were observed in US-treated samples, which could be another reason for improved functionality. However, the results of this study also revealed that prolonged high-power ultrasound exposure may eventually have a detrimental impact on HPI functional properties due to protein aggregation. Overall, this study suggests that high intensity ultrasound can enhance the functionality of HPI, which may ultimately improve its value in HPI-based food products.

Isoelectric precipitation and ultrafiltration were investigated for their potential to produce protein products from lentils. Higher protein concentrations were obtained when ultrafiltration was used (> 90%), whereas isoelectric precipitation resulted in higher contents of dietary fibre and some minerals (i.e., sodium and phosphorus). Differences in the functional properties between the two ingredients were found as the isoelectric precipitated ingredient showed lower protein solubilities over the investigated pH range (from 3 to 9) which can be linked to the slightly higher hydrophobicity values (2688.7) and total sulfhydryl groups (23.9 µM/g) found in this sample. In contrast, the protein ingredient obtained by ultrafiltration was superior with regard to its solubility (48.3%; pH 7), fat-binding capacity (2.24 g/g), water holding capacity (3.96 g/g), gelling properties (11%; w/w), and foam-forming capacity (69.6%). The assessment of the environmental performance showed that both LPIs exhibited promising properties and low carbon footprints in comparison to traditional dairy proteins.

The present study aimed to improve the survivability of L. acidophilus encapsulated in alginate-whey protein isolate (AL-WPI) biocomposite under simulated gastric juice (SGJ) and simulated intestinal juice (SIJ). Microcapsules were prepared based on emulsification/internal gelation technique. Optimal compositions of AL and WPI and their ratio in the aqueous phase were evaluated based on minimizing mean diameter (MD) of the microcapsules and maximizing encapsulation efficiency (EE), survivability of cells under SGJ (Viability), and release of viable cells under SIJ (Release) using Box-Behnken experimental design. Optimal composition comprising 4.54% (w/v) AL, 10% (w/v) WPI, and 10% (v/v) AL-WPI gum in the aqueous phase was determined statistically. Physicochemical characteristics of the optimized matrix were investigated by SEM, FTIR, and XRD analysis to determine surface morphology, molecular bonds, and crystalline nature of such hydrocolloid. It could be concluded that the proposed biocomposite is a good promise for nutrients encapsulation in the food industry.

This study evaluated the effects of different levels of ultrasonic power (200, 400, 600 W) and treatment time (0, 10, 15 and 30 min) on the structure, emulsification characteristics, and in vitro digestibility of chickpea protein isolate (CPI). The changes in surface hydrophobicity of CPI indicated that ultrasound treatment exposed more hydrophobic amino acid residues. The analysis of sulfhydryl content and zeta potential showed that ultrasound caused the disulfide bond of CPI to be opened, releasing more negatively charged groups, and the solution was more stable. In addition, Fourier Transform Infrared Spectroscopy (FT-IR) and intrinsic fluorescence spectroscopy showed that ultrasound changes the secondary and tertiary structure of CPI, which is due to molecular expansion and stretching, exposing internal hydrophobic groups. The emulsification and foaming stability of CPI were significantly improved after ultrasonic treatment. Ultrasonic treatment had a minor effect on the solubility, foaming capacity and in vitro digestibility of CPI. All the results revealed that the ultrasound was a promising way to improve the functional properties of CPI.

This study aimed to investigate the properties of heat-induced gels (85 °C for 30 min) of quinoa protein isolate (QPI) in the presence and absence of various polysaccharides including guar gum (GG), locust bean gum (LBG), and xanthan gum (XG) at pH 7. For this purpose, samples with three gum concentrations (0.05, 0.1, and 0.2 wt%) at a fixed QPI concentration (10 wt%) and a fixed ionic strength (50 mM NaCl) were studied in terms of their gelation behaviour, small and large deformation rheological properties, water holding capabilities, and microstructural characteristics. Rheological measurements revealed that all polysaccharides incorporation could improve gel strength (complex modulus, G*) and breaking stress, accelerate gel formations, and more stiffer gels were obtained at greater polysaccharide concentrations. The XG exhibited the most gel strengthening effect followed by LBG and GG. Incorporation of 0.2 wt% XG led to a 15 folds increase in G* compared to the control. Confocal laser scanning microscopy observation revealed that the polysaccharides also altered gel microstructures, with the gels containing XG showing the most compact gel structures. The findings of this study may provide useful information for the fabrication of novel QPI based food gel products with improved texture.

Foaming ability of oat protein isolate (OPI) was analysed at pH 4 and 7. Foaming properties were influenced by partial hydrolysis with trypsin (OPT) and alcalase (OPA). The viscoelasticity of the protein film, the interactions between the protein molecules, and the network forming within the protein film were analysed by interfacial rheology. At pH 7, foams made of OPI and OPT were found to be stable with OPI showing the fastest foaming ability. At pH 4, the foaming properties of OPI were found to be poor due to limited solubility. The specific cleavage pattern of trypsin resulted in peptides with improved foaming properties, especially at pH 4, resulting in a homogenous foam structure, a fast foaming ability, and a highly viscoelastic interfacial film. The formation of a thick steric protein layer at pH 7 and the formation of strong hydrophobic interactions at pH 4 were found to be the dominating foam stabilisation mechanisms. In conclusion, oat protein may serve as a food ingredient with targeted functional properties.