Interfacially stabilized nonaqueous lipid-based foams, which we name here oleofoams, are rarely encountered as opposed to the large number of aqueous foams stabilized by molecular or particulate emulsifiers. There is no case well described in the literature with a convincing characterization of the interfacial contribution to oleofoam stability. Methods for filling this gap are described here, which reach out to a large part of the lipid phase diagram. We bring here complete evidence that lipidic crystals made of a high fraction of fully soluble monoglyceride (MG) in oil do not only adsorb at the oil-air interface but also can easily form a jammed, closely packed layer of crystals around the bubbles of a foam produced by whipping (Pickering effect). Very fine bubbles, soft textures, or firmer ones such as for shaving foams could be obtained, with a high air fraction (up to 75%), which is unprecedented. A thin, jammed layer of crystals on bubbles can cause bubbles to retain nonspherical shapes in the absence of bulk effects for times much longer than the characteristic capillary relaxation time for bare bubbles, which is actual evidence for Pickering-type interfacial stabilization. By comparing to foams obtained by depressurization, we show that whipping is necessary for bubble wrapping with a layer of crystals. The origin of high stability against Ostwald ripening at long times is also discussed. Furthermore, we show that these Pickering whipped foams have rheological properties dominated by interfacial or film contributions, which is of high interest for food and cosmetics applications because of their high moduli. This system can be considered to be a model of the crystallization behavior of MG in oil, which is similar to that in many fats. Our methods are very general in the context of lipid-based foaming, in particular, from food materials, and were used in patent applications.

The molecular packing of amorphous maltodextrin-glycerol matrices is systematically explored by combining positron annihilation lifetime spectroscopy (PALS) with thermodynamic measurements and dilatometry. Maltodextrin-glycerol matrices are equilibrated at a range of water activities between 0 and 0.54 at T = 25 °C to analyze the effect of both water and glycerol on the average molecular hole size and the specific volume of the matrices. In the glassy state, glycerol results in a systematic reduction of the average molecular hole size. In contrast, water interacts with the carbohydrate matrix in a complex way. Thermodynamic clustering theory shows that, at very low water contents the water molecules are well dispersed and are closely associated with the carbohydrate chains. In this regime water acts as an antiplasticizer, whereby it reduces the size of the molecular holes. Conversely, at higher water contents, while still in the glassy state, water acts as a plasticizer by increasing the average hole volume of the carbohydrate matrices. This plasticization-dominated mechanism is likely to be due to the interplay between the ability of water to form hydrogen bonds with the hydroxyl residues on the carbohydrate chains and its mobility, which is significantly decoupled from the bulk mobility of the matrix. Our findings are of key importance for the understanding of the effect of glycerol on the biostabilization performance of these carbohydrate matrices, as it provides a first insight on how molecular packing can relate to the dynamics in such matrices.

In the treatment of oropharyngeal dysphagia, the link between diagnosis and prescription of thickened liquids that are safe to swallow is not always straightforward. Frequently, the capacity to objectively assess and quantify the rheological properties of diagnostic test fluids and to select “rheologically equivalent” dietary products is missing. Perhaps sometimes the importance of an objective comparison is not fully appreciated because two liquids seem reasonably similar in a subjective comparison (e.g., flow from a spoon). The present study deals with some of these issues. Shear viscosity measurements were used to characterize the flow behavior of videofluoroscopic contrast agents and of thickened fluids prepared with commercial thickening agents. Effects of time and composition of the different fluids were analyzed regarding shear-rate-dependent viscosity. Nearly all materials tested showed a pronounced dependence of viscosity with shear rate (“shear thinning”). Results confirm that it is feasible (but not always straightforward) to “match” the viscosities of diagnostic fluids and thickened beverages if certain precautions are taken. For example, the time required to reach final viscosity levels can be significant for some thickeners, particularly when used with liquids containing contrast agents. It is recommend to use only diagnostic materials and thickening agents for which reliable viscosity data are available.

Positron annihilation lifetime spectroscopy (PALS) is used in conjunction with dilatometry to analyse the effects of water and low molecular weight diluents (maltose and glycerol) on the molecular organisation and density of carbohydrate oligomers commonly used in the pharmaceutical and food industries for the formulation of encapsulation matrices. In the glassy state, both maltose and glycerol act as packing enhancers, causing a non-linear decrease in the average molecular hole size of the carbohydrate matrices. Water exists in a highly non-ideal state in these systems and it alters the molecular organisation of the matrices in a complex manner, whereby it can act either as an anti-plasticiser or a plasticiser, depending on the level of hydration.