Phase separation in mixtures of ovalbumin and konjac glucomannan: Physicochemical and microscopic investigations

Elucidation of interactions between myofibrillar proteins and κ-carrageenan as mediated by NaCl level: Perspectives on multiple spectroscopy and molecular docking

The present study was aimed to investigate the intermolecular interaction between myofibrillar proteins (MP) and κ-carrageenan (KC) as mediated by KC concentration (0.1, 0.2, 0.3, and 0.4 %, w/w) and NaCl levels (0.3 and 0.6 M) based on the multiple spectroscopy and molecular docking. The results showed that the incorporation of KC increased the turbidity, zeta-potential, and surface hydrophobicity of MP-KC mixed sols with a dose-dependent manner, as well as significantly decreasing the protein solubility (P < 0.05), which indicated that the interaction between KC and MP promoted the expansion of protein structure and exposed more hydrophobic groups. Fluorescence spectra result revealed that the interaction between MP and KC was a static quenching in the fluorescence quenching process, which affected the aromatic amino acids residue microenvironment of MP. Moreover, the existence of KC decreased the α-helix contents of MP (P < 0.05), contributing to the transformation from random structure to organized configuration of MP. In addition, molecular forces, the molecular docking and thermodynamic parameters indicated that hydrophobic interactions, van der Waals force, and hydrogen bonding were considered as the main interaction forces between MP and KC. Furthermore, 0.6 M NaCl level rendered higher solubility and particle size, as well as lower turbidity and the surface hydrophobicity of MP-KC mixed sols than those with 0.3 M NaCl level (P < 0.05), which promoted the unfolding of MP molecule and subsequently increased the numbers of binding sites between MP and KC, facilitating the intermolecular interactions between MP and KC in mixed sols.

Segregative phase separation of gelatin and tragacanth gum solution and Mickering stabilization of their water-in-water emulsion with microgel particles prepared by complex coacervation

This study aimed to investigate the segregative interaction of gelatin (G) and tragacanth gum (TG) and the stabilization of their water-in-water (W/W) emulsion by G-TG complex coacervate particles. Segregation was studied at different pHs, ionic strengths and biopolymer concentrations. Results showed that incompatibility was affected by increasing the biopolymer concentrations. So, three reigns were demonstrated in the phase diagram of the salt-free samples. NaCl significantly changed the phase behavior via enhancement of self-association of polysaccharide and changing solvent quality due to the charge screening effect of ions. The W/W emulsion prepared from these two biopolymers and stabilized with G-TG complex particles was stable for at least one week. The microgel particles improved emulsion stability by adsorption to the interface and creating a physical barrier. A fibrous and network-like structure of the G-TG microgels was observed by scanning electron microscopy images suggesting the Mickering emulsion stabilization mechanism. It was confirmed that the bridging flocculation between the microgel polymers led to phase separation after the stability period. Biopolymer incompatibility investigation is a useful tool to obtain beneficial knowledge for preparation new food formulation, especially no contain oil emulsions for low- calorie diets.

Dietary glycerol monolaurate supplementation for the modification of functional properties of egg white protein

BACKGROUND

Understanding the interactions between feed additives and the functional properties of egg white protein (EWP) may offer novel insights into the effects of feed additives on laying hens and may provide an alternative for modification of the functional properties of EWP by using laying hens as bioreactors. Glycerol monolaurate (GML) is widely used in the food industry as an effective antibacterial emulsifier. In this work, the effects of three doses of dietary GML supplementation (150, 300, and 450 mg kg^-1 hen) on the functional properties of EWP were investigated.

RESULTS

The hardness of EWP gels was significantly improved by 300 and 450 mg kg^-1 GML supplementation. Foaming capacity (FC) and foaming stability (FS) were increased after GML treatment; 450 mg kg^-1 GML supplementation showed the most significant improvements, with 44.82% in FC and 23.39% in FS. Stabilization of EWP-oil emulsions was also improved, supported by a slowed creaming process and the formation of smaller oil droplets. The heat denaturation temperature and rheological properties were also modified by dietary GML supplementation, implying improved thermal stability.

CONCLUSION

Our study demonstrated that GML supplementation has the potential to modify the functional properties of EWP, broadening the application of GML and providing a new perspective for evaluation of the efficacy of feed additives. © 2019 Society of Chemical Industry.

Degradation of konjac glucomannan by Thermobifida fusca thermostable β-mannanase from yeast transformant

Native konjac glucomannan was used as the substrate for thermophilic actinomycetes, Thermobifida fusca BCRC19214, to produce β-mannanase. The β-mannanase was purified and five internal amino acid sequences were determined by LC-MS/MS. These sequences had high homology with the β-mannanase from T. fusca YX. The tfm gene which encoded the β-mannanase was cloned, sequenced and heterologous expressed in Yarrowia lipolytica P01 g expression system. Recombinant heterologous expression resulted in extracellular β-mannanase production at levels as high as 3.16 U/ml in the culture broth within 48 h cultivation. The recombinant β-mannanase from Y. lipolytica transformant had superior thermal property. The optimal temperature of the recombinant β-mannanase from Y. lipolytica transformant (pYLSC1-tfm) was 80°C. When native konjac glucomannan was incubated with the recombinant β-mannanase from Y. lipolytica transformant (pYLSC1-tfm) at 50°C, there was a fast decrease of viscosity happen during the initial phase of reaction. This viscosity reduction was accompanied by an increase of reducing sugars. The surface of konjac glucomannan film became smooth. After 24h of treatment, the DPw of native konjac glucomannan decreased from 6,435,139 to 3089.