Pickering oil-in-water emulsions stabilized by carboxylated cellulose nanocrystals – Effect of the pH

Use and Understanding of the Role of Spontaneously Formed Nanocellulosic Fiber from Lime (Citrus aurantifolia Swingle) Residues to Improve Stability of Sterilized Coconut Milk

Feasibility of using nanocellulosic fiber (NF) from lime residues as a stabilizer for oil-in-water emulsion was investigated. One-step process to simultaneously prepare an emulsion and NF is proposed. NF could spontaneously form by adding appropriately prepared fiber powder into the test emulsion viz. coconut milk, which was subsequently subject to homogenization and sterilization. Properties of the samples, that is, microstructure, rheological properties, emulsion stability, and color, after sterilization and after 8-week storage at 30 °C were determined. Sterilized samples exhibited pseudoplastic behavior. Samples containing higher NF concentrations exhibited higher viscosity; viscosity remained constant throughout the whole storage period. High emulsion stabilities (>97%) were observed for samples containing 0.4 to 0.8% (w/v) of NF. L^* , C^* , and h^* of the samples were 79 to 80, 8 to 10, and 90, respectively. Three-dimensional network of NF (diameters < 50 nm) attached to fat globule surfaces formed during homogenization is postulated to help stabilize the emulsions. PRACTICAL APPLICATION: One-step process to simultaneously prepare oil-in-water emulsion as well as nanocellulosic fiber (NF) is proposed. Such a formed NF can serve as natural ingredient to stabilize the emulsion. The proposed procedures should be of great interest to an industry producing oil-in-water emulsions (for example, canned coconut milk) that is looking for a natural alternative to synthetic stabilizer.

Role of protein-cellulose nanocrystal interactions in the stabilization of emulsion

HYPOTHESIS

The interactions between two bio-based emulsifiers, namely cellulose nanocrystals (CNC) and the surface active sodium caseinate (CAS), can influence the formation and stability of oil-in-water emulsion (O/W).

EXPERIMENTS

After studying the interactions between CNC and CAS, in bulk, and at air-water and liquid-liquid interfaces, emulsions have been prepared through different routes of addition, at pH 7 and 3, at which CNC and CAS had repulsive and attractive interactions, respectively. The routes of addition were (1) CAS and CNC simultaneously, (2) CAS first followed by CNC in a subsequent emulsification step and (3) CNC first, followed by CAS. The emulsions were characterized by laser diffraction and optical microscopy.

FINDINGS

At pH 7, in the case of repulsive interactions, the surface activity of CAS was balanced by the irreversible adsorption of CNC, irrespectively of the route of emulsification. At pH 3, in the case of attractive interactions, using route (1), the aggregates CAS-CNC provided better emulsification than CNC and CAS alone. For emulsions prepared by route (2) and (3), gelling was observed which could be controlled through the order of addition. Emulsions prepared at pH 7 then adjusted to pH 3 exhibited an increase in viscosity, while the droplet size was not affected.

Adsorption and Assembly of Cellulosic and Lignin Colloids at Oil/Water Interfaces

The surface chemistry and adsorption behavior of submicrometer cellulosic and lignin particles have drawn wide-ranging interest in the scientific community. Here, we introduce their assembly at fluid/fluid interfaces in Pickering systems and discuss their role in reducing the oil/water interfacial tension, limiting flocculation and coalescence, and endowing given functional properties. We discuss the stabilization of multiphase systems by cellulosic and lignin colloids and the opportunities for their adoption. They can be used alone, as dual components, or in combination with amphiphilic molecules for the design of multiphase systems relevant to household products, paints, coatings, pharmaceutical, foodstuff, and cosmetic formulations. This invited feature article summarizes some of our work and that of colleagues to introduce the readers to this fascinating and topical area.

Pickering Emulsions Containing Cellulose Microfibers Produced by Mechanical Treatments as Stabilizer in the Food Industry

Pickering emulsions are emulsions stabilized by solid particles, which generally provide a more stable system than traditional surfactants. Among various solid stabilizers, bio-based particles from renewable resources, such as micro- and nanofibrillated cellulose, may open up new opportunities for the future of Pickering emulsions owing to their properties of nanosize, biodegradability, biocompatibility, and renewability. The aim of this research was to obtain oil-in water (O/W) Pickering emulsions using cellulose microfibers (CMF) produced from cotton cellulose linters by mechanical treatment through a high-pressure homogenizer. The O/W Pickering emulsions were prepared with different O/W ratios by mixing edible oil (sunflower oil) with water containing CMF at concentrations of up to 1.0 wt%. The apparent viscosity of the separated emulsion phase was measured. Results showed the feasibility of using low concentration of CMF for preparing and stabilizing Pickering emulsions, with the apparent viscosity of the emulsion phase increasing 60–90 times with respect to the sunflower oil, for a shear rate of 1 s−1. In addition, theoretical nutrition facts of the emulsions were calculated and compared with other fats used in foods, showing that they can be a promising low-calorie product containing dietary fiber, replacing trans and saturated fats in foods.