Evaluation of digestibility, solubility, and surface properties of trehalose-conjugated quinoa proteins prepared via pH shifting technique.

Soluble trehalose-conjugated quinoa proteins (T-QPs) were effectively prepared using the pH-shifting mechanism. The structural properties of the T-QPs were evaluated using a comparative evaluation, which included analyzing the amide I, surface charge and hydrophobicity, protein conformation, thermal stability, and protein structures. The results suggested that the development of the T-QPs was influenced mainly by no-covalent bonds. These interactions significantly influenced (P < 0.05) the quinoa proteins' conformation and higher-protein structure. T-QP had significant (P < 0.05) surface properties. Furthermore, the T-QPs exhibited improved solubility (79.7 to 88.4%) and digestibility (79.8 to 85.1%). Therefore, quinoa protein proved an excellent plant-based protein for conjugation with disaccharides. These findings provide significant insight into the potential development of modified proteins with enhanced solubility and digestibility by creating trehalose-conjugated plant-based proteins.

Molecular forces driving protein complexation of lentil and whey proteins: Structure-function relationships of trehalose-conjugated protein complexes on protein digestibility and solubility.

Plant-based proteins are often associated with a range of health benefits. Most research primarily investigates pea and soy proteins, while lentil proteins received minimal attention. This study evaluates the effect of protein complexation (using the pH-shifting technique) coupled with trehalose conjugation on lentil and whey proteins. The protein structures after the modification were analysed using spectroscopic methods: Fourier-transform infrared, ultraviolet spectra, and fluorescence spectra. The amide group I, conformation protein, and tertiary structure of the trehalose-conjugated lentil-whey protein complexes (T-LWPs) showed significant changes (P < 0.05). Moreover, the surface properties (surface hydrophobicity and charges) of T-LWPs were significantly modified (P < 0.05), from 457 to 324 a.u and from 36 to -40 mV, respectively. Due to these modifications on the protein structures, the protein digestibility (80-86%) and water solubility (90-94.5%) of T-LWPs increased significantly (P < 0.05) with the increase in the trehalose concentration, from 0 (control) to 5% (w/w), respectively. This study suggested that coupling protein complexation and trehalose conjugation can enhance the overall properties of lentil-based protein complexes. With this enhancement, more opportunities in the utilisation of lentils are to be expected.

Trehalose-conjugated lentil-casein protein complexes prepared by structural interaction: Effects on water solubility and protein digestibility.

The two limiting factors for lentil protein utilization are water solubility and digestibility. In this study, we utilized two non-thermal techniques: (1) protein complexation of lentil and casein proteins using the pH-shifting method and (2) protein conjugation with trehalose to produce trehalose-conjugated lentil-casein protein complexes (T-CPs) with enhanced water solubility and digestibility. The protein structure of the T-CPs was analyzed for secondary protein structure, conformation protein, and tertiary protein structure using Fourier-transform infrared, UV, and fluorescence spectroscopies, respectively. The surface hydrophobicity and surface charge of T-CPs solution at pH 7.0 changed significantly (P < 0.05). Using these two non-thermal techniques, the water solubility and digestibility of T-CPs increased significantly (P < 0.05) by 85 to 89 % and 80 to 85 %, respectively. The results of this study suggested that these non-thermal techniques could enhance the surface and protein structure properties, improving water solubility and digestibility.

Evaluation of structure, quality, physicochemical properties, and phenolics content of pea proteins: A novel strategy through the incorporation of fermentation.

The utilization of pea proteins (PPs) is limited due to their relatively low protein digestibility (∼81%) compared to animal-based proteins, such as whey. The present investigation involved the fermentation of PPs at a concentration of 1% (w/v) using 5% (w/v) water kefir for 60 h at 25°C to improve the functional properties of PPs. The results showed a significant (p < 0.05) increase in lactic acid and acetic acid production during fermentation. These findings suggest that PPs can be effectively fermented using water kefir as a starter culture for the increased protein digestibility of PPs. The PP conformation underwent modifications, including secondary and tertiary protein structure alterations. The total phenolic compounds increased throughout the fermentation, reaching around 695.32 ± 15 mg gallic acid equivalent/100 g after 24 h of fermentation. Furthermore, the fermentation process has culminated in significant (p < 0.05) changes in the surface charge and hydrophobic properties of the fermented PPs, from -38.1 to -45.73 and 362.7 to 550.2, respectively. Fermentation using water kefir is a promising technique for improving the digestibility, protein structure, and nutritional values of PPs.

Characterisation of the protein quality and composition of water kefir-fermented casein.

This study aimed to assess the technique of natural fermentation by applying water kefir to the casein protein. The diverse microorganisms and their enzymes found naturally in the water kefir can influence casein's characteristics. The fermented casein's protein quality (digestibility and secondary protein structure) and composition (total soluble solids and nutritive and non-nutritive substances) were investigated. Our findings revealed that the fermented casein's protein digestibility and total phenolic content increased from 82.46 to 88.60 % and 7.6 to 8.0 mg gallic acid equivalent/100 g, respectively. In addition, their surface charge and hydrophobicity changed from -30.06 to -34.93 mV and 286.9 to 213.7, respectively. Furthermore, the fermented casein's secondary protein components, α-helix (decreased from 13.66 to 8.21 %) and random coil (increased from 16.88 to 19.61 %), were also altered during the fermentation. Based on these findings, the water kefir fermentation approach could be an effective, practical, non-thermal approach for improving casein's protein quality and composition.