Interfacial and Foaming Properties of Tailor-Made Glycolipids—Influence of the Hydrophilic Head Group and Functional Groups in the Hydrophobic Tail

Abstract

Glycolipids are a class of biodegradable surfactants less harmful to the environment than petrochemically derived surfactants. Here we discuss interfacial properties, foam stability, characterized in terms of transient foam height, gas volume fraction and bubble diameter as well as texture of seven enzymatically synthesized surfactants for the first time. Glycolipids consisting of different head groups, namely glucose, sorbitol, glucuronic acid and sorbose, combined with different C10 acyl chains, namely decanoate, dec-9-enoate and 4-methyl-nonanoate are compared. Equilibrium interfacial tension values vary between 24.3 and 29.6 mN/m, critical micelle concentration varies between 0.7 and 3.0 mM. In both cases highest values were found for the surfactants with unsaturated or branched tail groups. Interfacial elasticity and viscosity, however, were significantly reduced in these cases. Head and tail group both affect foam stability. Foams from glycolipids with sorbose and glucuronic acid derived head groups showed higher stability than those from surfactants with glucose head group, sorbitol provided lowest foam stability. We attribute this to different head group hydration also showing up in the time to reach equilibrium interfacial adsorption. Unsaturated tail groups reduced whereas branching enhanced foam stability compared to the systems with linear, saturated tail. Moreover, the tail group strongly influences foam texture. Glycolipids with unsaturated tail groups produced foams quickly collapsing even at smallest shear loads, whereas the branched tail group yielded a higher modulus than the linear tails. Normalized shear moduli for the systems with different head groups varied in a narrow range, with the highest value found for decylglucuronate.

Comparative study on interfacial and foaming properties of glycolipids in relation to the gas applied for foam generation

“…(2020) (11). Briey, an evaporative light scattering detector from B ÜCHI Labortechnik (Essen, Germany) was used for detection.…”

“…Dynamic interfacial tension was earlier identied as crucial parameter for foam stabilization by glycolipids and non-ionic surfactants. 11,18 Results of interfacial tension measurements are summarized in Table 2. CMC of all investigated glycolipids were considerably lower than for SDS.…”

“…In recent studies glycolipids exhibited high potential as emulsion and foam stabilizing agents but comparisons of their properties with conventional surfactants are still lacking. 11,12 Critical micelle concentration (CMC), dynamic interfacial tension, dilatational interfacial elasticity and dilatational interfacial viscosity are parameters of interest for characterizing interfacial properties as they are correlated with stabilizing effects on disperse systems. [13][14][15][16][17][18] Foams are thermodynamically unstable systems with applications in various elds e.g.…”

Shear modulus and yield stress of foams: contribution of interfacial elasticity

“…Foams were produced in glass filter funnels (16-40 mm pore size VitraPOR s Por.4, Robu) perfused by 60 ml nitrogen per minute as described in ref. 16 and 20, except for the reconstituted whole milk foams, which were produced in a commercial milk whipper (Aeroccino4, Nespresso), as described in. 17 Recording of foam age was started once the filter funnel was completely filled with foam and the nitrogen flow was stopped or the whipper stopped the foaming process.…”

“…À1As described in ref 16. Glycolipid glucose 4-methyl-nonanoate 1.2 g l À1 As described in ref 16. Block copolymer poloxamer 407 (Sigma Aldrich) 0.05, 0.5 and 5 mM poloxamer in 0.1, 50 and 100 mM NaCl, respectivelyDissolved in demineralized water at 20 1C Block copolymer poloxamer 188 (Sigma Aldrich) 0.5 mM poloxamer in 50 mM NaCl Dissolved in demineralized water at 20 1C Guinness stout beer Degassed; at 20 1C Whole milk powder (Nestlé) 10 wt% As described in ref.…”