Aqueous foams stabilized by chitin nanocrystals

Abstract

The aim of the present study was to explore the potential use of chitin nanocrystals, as colloidal rod-like particles, to stabilize aqueous foams. Chitin nanocrystals (ChN) were prepared by acid hydrolysis of crude chitin and foams were generated mainly by sonicating the respective dispersions. The foamability of the chitin nanocrystals was evaluated and the resulting foams were assessed for their stability, in terms of foam volume reduction and serum release patterns, during storage. Additionally, the samples were studied with light scattering and optical microscopy in order to explore the bubble size distribution and morphology of the foam. Nanocrystal concentration and charge density was varied to alter the packing of the crystals at the interface. At low concentrations of ChNs, foams were stable against coalescence and disproportionation for a period of three hours, whereas at higher concentrations, the foams were stable for several days. The enhanced stability of foams prepared with ChNs, compared to surfactant-stabilized foams, can be mainly attributed to the irreversible adsorption of the ChNs at the air-water interface, thereby providing Pickering stabilization. Both foam volume and stability of the foam were increased with an increase in ChNs concentration, and at pH values around the chitin's pKa (pH 7.0). Under these conditions, the ChNs show minimal electrostatic repulsion and therefore a higher packing of the nanocrystals is promoted. Moreover, decreased electrostatic repulsion enhances network formation between the ChNs in the aqueous films, thereby providing additional stability by gel formation. Overall, ChNs were proven to be effective in stabilizing foams, and may be useful in the design of Pickering-stabilized food grade foams.

Controlling the Self-Assembly Behavior of Aqueous Chitin Nanocrystal Suspensions

“…Chitin (from shrimp shells, practical grade, powder) was purified by sodium hydroxide treatment (5 wt%, 80 °C, 3 h), followed by acidic bleaching in sodium chlorite (0.3 wt%, 80 °C, 3 h). 18 These purification steps were repeated three times each before dialyzing against Milli-Q water (Regenerated Cellulose 6 dialysis tubing, MWCO 12-14 kDa), and subsequent isolation by centrifugation to form a pellet (25,000g, 4 °C, 30 min), as described in detail in the ESI.…”

“…The purified chitin pellet (~10 wt% chitin in water) was hydrolyzed in hydrochloric acid (HCl, 3.0 -5.0 M) under reflux (104 °C, 90 -540 min, Table 1) as adapted from previously reported protocols. 3,18,19 The reaction mixture was quenched by diluting with ice-cold Milli-Q water and washed twice by centrifugation (as above). The produced ChNC suspension was then dialyzed against Milli-Q water until the conductivity of the surrounding bath remained stable for two days.…”

Oil-in-oil emulsions stabilised solely by solid particles

“…It has been well documented that a variety of solid particles can adsorb at fluid interfaces 1 and hence stabilise emulsions and foams as well as enabling the preparation of novel materials like dry water, [2][3][4] dry oil, [5][6][7] liquid marbles [8][9][10][11] and powdered emulsions. 12 The fluid pairs include oil and water (Pickering emulsions), 13 air and water (particle-stabilised aqueous foams), 14 air and oil (particle-stabilised oil foams) 15 and water and water (Pickering emulsions). 16 This paper is concerned with mixtures of immiscible oils stabilised by particles, so-called oil-inoil, o/o, emulsions.…”

Estudio de las propiedades fisicoquímicas y biológicas de microencapsulados de compuestos bioactivos de Neem en matrices de quitosano

“…En la actualidad y en busca de compuestos de origen natural, se han formulado nanopartículas de quitina (CT) que sirvan como solidos capaces de estabilizar emulsiones (Tzoumaki et al, 2011(Tzoumaki et al, , 2015Gülseren & Corredig, 2013;Perrin et al, 2014;Ifuku et al, 2009Ifuku et al, , 2015Pang et al, 2017, Demina et al, 2018Barkhordari & Fathi, 2018;Larbi et al, 2018).…”

“…Los nanocristales (NCT) y nanofibrillas (NF) de CT, han cobrado interés debido a que se pueden aplicar en áreas alimenticias, farmacéuticas o cosméticas. Las NCT de manera convencional son obtenidos por hidrolisis ácida (Tzoumaki et al, 2011(Tzoumaki et al, , 2015Gülseren & Corredig, 2013;Perrin et al, 2014;Demina et al, 2018;Barkhordari & Fathi, 2018;Larbi et al, 2018), mientras que las NF pueden obtenerse por la oxidación mediada por TEMPO (Ifuku et al, 2015;Pang et al, 2017) o bien por métodos mecánicos (Ifuku et al, 2009;2014;Larbi et al, 2018). Si bien, tanto NCT como NF han sido empleadas para estabilizar emulsiones tipo Pickering, Larbi et al (2018) evaluaron las diferencias entre el uso de ambas, observando que las NF tienen una mejor capacidad de estabilización de emulsiones O/W debido a que tienen mayor viscosidad y mejor estabilidad térmica que los NCT que solo presentaron mayor grado de transparencia.…”