Effect of Emulsion Droplet Size on Foaming Properties of Milk Fat Emulsions

The bubbly life and death of animal and plant milk foams

Milk foams are fragile objects, readily prepared for frothy cappuccinos and lattes using bovine milk. However, evolving consumer preferences driven by health, climate change, veganism, and sustainability have created a substantial demand for creating frothy beverages using plant-based milk alternatives or plant milks. In this contribution, we characterize maximum foam volume and half-lifetime as metrics for foamability and foam stability and drainage kinetics of two animal milks (cow and goat) and compared them to those of the six most popular, commercially available plant milks: almond, oat, soy, pea, coconut, and rice. We used three set-ups: an electric frother with cold (10 °C) and hot (65 °C) settings to emulate the real-life application of creating foam for cappuccinos, a commercial device called a dynamic foam analyzer or DFA and fizzics-scope, a bespoke device we built. Fizzics-scope visualizes foam creation, evolution, and destruction using an extended prism-based imaging system facilitating the capture of spatiotemporal variation in foam microstructure over a broader range of heights and liquid fractions. Among the chosen eight milks, oat produces the longest-lasting foams, and rice has the lowest amount and stability of foam. Using the hot settings, animal milks produce more foam volume using an electric frother than the top three plant milks in terms of foamability (oat, pea, and soy). Using the cold settings, oat, soy, and almond outperform cow milk in terms of foam volume and lifetime for foams made with the frother and sparging. Most plant milks have higher viscosity due to added polysaccharide thickeners, and in some, lecithin and saponin can supplement globular proteins as emulsifiers. Our studies combining foam creation by frothing or sparging with imaging protocols to track global foam volume and local bubble size changes present opportunities for contrasting the physicochemical properties and functional attributes of animal and plant-based milk and ingredients for engineering better alternatives.

Lattice Boltzmann simulation of deformable fluid-filled bodies: progress and perspectives

With the rapid development of studies involving droplet microfluidics, drug delivery, cell detection, and microparticle synthesis, among others, many scientists have invested significant efforts to model the flow of these fluid-filled bodies. Motivated by the intricate coupling between hydrodynamics and the interactions of fluid-filled bodies, several methods have been developed. The objective of this review is to present a compact foundation of the methods used in the literature in the context of lattice Boltzmann methods. For hydrodynamics, we focus on the lattice Boltzmann method due to its specific ability to treat time- and spatial-dependent boundary conditions and to incorporate new physical models in a computationally efficient way. We split the existing methods into two groups with regard to the interfacial boundary: fluid-structure and fluid-fluid methods. The fluid-structure methods are characterised by the coupling between fluid dynamics and mechanics of the flowing body, often used in applications involving membranes and similar flexible solid boundaries. We further divide fluid-structure-based methods into two subcategories, those which treat the fluid-structure boundary as a continuum medium and those that treat it as a discrete collection of individual springs and particles. Next, we discuss the fluid-fluid methods, particularly useful for the simulations of fluid-fluid interfaces. We focus on models for immiscible droplets and their interaction in a suspending fluid and describe benchmark tests to validate the models for fluid-filled bodies.

Whipping properties of recombined, additive-free creams

There is increasing industrial interest in the use of the milkfat globule membrane as a food ingredient. The objective of this research was to determine whether the aerosol whipping performance of cream separated into butter and buttermilk, and then recombined, would perform in a manner similar to untreated cream. Churning of cream tempered to different solid fat contents was used to separate butter from buttermilk, which were then recombined at the same ratios as the initial extraction yield, or with 25% extra buttermilk. Differences in milkfat globule size distributions among the recombined creams were apparent; however, their whipping behavior and overrun were similar. Importantly, all recombined creams did not yield properties similar to the original cream, indicating that the unique native milkfat globule membrane structure plays a role in cream performance well beyond its simple presence.

Interfacial characteristics, colloidal properties and storage stability of dairy protein-stabilized emulsion as a function of heating and homogenization

This research investigated the influence of processing history on physicochemical properties of dairy protein-stabilized emulsions. Emulsions were heated (UHT) either before or after a single homogenization (UHTSH, SHUHT) or homogenized both before and after heating (double homogenization, DHUHT). The results demonstrated that UHT treatment increased the protein load at the oil/water interface while homogenization prior to UHT (SHUHT) inhibited displacement of protein by surfactant molecules, and this emulsion exhibited higher interfacial protein coverage and wider size distribution compared to the emulsion produced by UHTSH. The use of the double homogenization with UHT resulted in emulsion droplets with the smallest average size and lowest concentration of unabsorbed protein. However, no difference in the protein load in a specific area was noticed between emulsions produced by DHUHT and SHUHT. When changes of surface tension at the air/water interface were measured using a drop tensiometer, SHUHT emulsion showed the fastest decrease of surface tension due to the occurrence of a lower level of surfactant displacement where more surfactant was available for fast adsorption. Emulsions prepared with DHUHT or UHTSH decreased the surface tension in a slower speed than SHUHT. During storage, partial coalescence of emulsion droplets was observed for emulsions produced with single homogenization, regardless of whether this was carried out before or after heating. Double homogenization formed more stable emulsions than single homogenization. This work clearly showed that it is possible to tailor physico-chemical functionalities of dairy protein-based emulsions by controlling the interactions between proteins or with surfactants during processing.

Soft matter food physics--the physics of food and cooking

This review discusses the (soft matter) physics of food. Although food is generally not considered as a typical model system for fundamental (soft matter) physics, a number of basic principles can be found in the interplay between the basic components of foods, water, oil/fat, proteins and carbohydrates. The review starts with the introduction and behavior of food-relevant molecules and discusses food-relevant properties and applications from their fundamental (multiscale) behavior. Typical food aspects from 'hard matter systems', such as chocolates or crystalline fats, to 'soft matter' in emulsions, dough, pasta and meat are covered and can be explained on a molecular basis. An important conclusion is the point that the macroscopic properties and the perception are defined by the molecular interplay on all length and time scales.