Search

This research delves into understanding the effects of composition on the rheological response of multi-component food inks for 3D food printing. Accordingly, the motivation is to decouple the nutrient and water content effects on the rheology. We formulated inks by combining pea fractions with water and employing a water-holding-capacity based hydration method. Rheology is characterized by steady shear rate and oscillatory strain amplitude sweeps. Strain sweep curves infer that the deformation response of all inks follows a similar trend, and samples sharing the same macronutrient formulation are mapped to a master curve after scaling with the elastic plateau modulus. Samples sharing the same macronutrient formulation mapped to a master curve after scaling with the elastic modulus. Shear rate testing showed that the inks were shear thinning yield stress materials. Shear rate sweeps also collapsed on a master curve scaled by the yield stress and critical shear rate on the y and x axes. The yield stress and the plateau modulus appeared to be controlled by the water content, while the shear and strain thinning exponents were independent of the formulations, inferring that the rheology is scaled by the water content while preserving the shear thinning response. Observing the independence of the rheological properties from the nutrient composition and scalability of the rheology by the water content provided a step forward in developing formulations with various nutrient content at desired ow properties, which promises personalized nutrition. Furthermore, the study shows the applicability of various rheological techniques, which are expected to contribute to the literature on the rheology of granular pastes.

In this paper, we describe a model for pore formation in food materials during drying. As a proxy for fruits and vegetables, we take a spherical hydrogel, with a stiff elastic skin, and a central cavity filled with air and water vapour. The model describes moisture transport coupled to large deformation mechanics. Both stress and chemical potential are derived from a free energy functional, following the framework developed by Suo and coworkers. We have compared Finite Volume and Finite Element implementations and analytical solutions with each other, and we show that they render similar solutions. The Finite Element solver has a larger range of numerical stability than the Finite Volume solver, and the analytical solution also has a limited range of validity. Since the Finite Element solver operates using the mathematically intricate weak form, we introduce the method in a tutorial manner for food scientists.Subsequently, we have explored the physics of the pore formation problem further with the Finite Element solver. We show that the presence of an elastic skin is a prerequisite for the growth of the central cavity. The elastic skin must have an elastic modulus of at least 10 times that of the hydrogel. An initial pore with 10% of the size of the gel can grow to 5 times its initial size. Such an increase in porosity has been reported in the literature on drying of vegetables, if a dense hard skin is formed, known as case hardening. We discuss that models as presented in this paper, where moisture transport is strongly coupled to large deformation mechanics, are required if one wants to describe pore/structure formation during drying and intensive heating (as baking and frying) of food materials from first principles.

In this paper, we review the physical/chemical phenomena, contributing to the final texture of French fries, as occurs in the whole industrial production chain of frozen par-fried fries. Our discussion is organized following a multiscale hierarchy of these causal factors, where we distinguish the molecular, cellular, microstructural, and product levels. Using the same multiscale framework, we also discuss currently available theoretical knowledge, and experimental methods probing the relevant physical/chemical phenomena. We have identified knowledge gaps, and experimental methods are evaluated in terms of the effort and value of their results. With our overviews, we hope to give promising research directions such to arrive at a multiscale model, encompassing all causal factors relevant to the final texture. This multiscale model is the ultimate tool to evaluate process innovations for effects on final textural quality, which can be balanced against the impacts on sustainability and economics.

In this paper, we review the physicochemical phenomena occurring during the structuring processes in the manufacturing of plant-based meat analogs via high-moisture-extrusion (HME). After the initial discussion on the input materials, we discuss the hypotheses behind the physics of the functional tasks that can be defined for HME. For these hypotheses, we have taken a broader view than only the scientific literature on plant-based meat analogs but incorporated also literature from soft matter physics and patent literature. Many of these hypotheses remain to be proven. Hence, we hope that this overview will inspire researchers to fill the still-open knowledge gaps concerning the multiscale structure of meat analogs.

In this paper we present a Lattice Boltzmann model for food freezing, using the enthalpy method. Simulations are performed using the case study of freezing par-fried french fries. The action of par-frying leads to moisture removal from the crust region, which was treated via the initial conditions for the freezing model. Simulations show that under industrial-relevant freezing conditions, the crust region remains either unfrozen or only partially frozen. This result is important for the practical quality problem of dust, which is the phenomenon of fracturing of the crust during finish-frying.Next to the insight, the Lattice Boltzmann freezing model rendered for the case study of par-fried french fries, we pose that this freezing application is a comprehensive tutorial problem, via which food scientists can be conveniently introduced to the Lattice Boltzmann method. Commonly, the Lattice Boltzmann method has its value in solving complex fluid flow problems, but the complexity of these problems is possibly withholding food scientists to get familiar with the method. Our freezing is solved in 2D, and on a simple square lattice with only 5 particle velocities (a D2Q5 lattice). We hope via this simple tutorial problem, the Lattice Boltzmann method becomes more accessible.

In our quest for novel ingredients to be used in sugar replacement strategies, we have investigated the thermodynamics of polycarboxylic acids, such as citric acid. We have demonstrated the applicability of the Flory-Huggins (FH) theory to describe the thermodynamics of polycarboxylic acids solutions. Moreover, for citric acid we can describe the complete phase diagram with the theory. It shows that polycarboxylic acids have similar plasticizing and hygroscopic properties as sugars and polyols.Regarding mixtures of polycarboxylic acids and carbohydrates, the FH theory is able to describe a) the water activity of the mixtures, b) the solubility of ternary mixtures of acids and sugars, c) the lowering of the deliquescence point for binary mixtures of crystals, and d) the melting point depression in eutectic mixtures. Unexpectingly, our investigations show there is a strong non-zero FH interaction parameter between carboxylic acids and carbohydrates. In our prior sugar replacement strategy we have assumed zero interactions between plasticizers. Here, we will readdress this assumption. Carefull investigations of solid-liquid equilibrium of eutectic mixtures involving polycarboxylic acids and/or carbohydrates, shows nearly zero interaction in eutectic mixtures consisting only of two carbohydrates or two polycarboxylic acids. We now hold the hypothesis that there is strong non-zero interaction if the mixture contains plasticizers strongly differing in the amount of hydrogen bonding groups. This strong interaction explains why these mixtures, like polycarboxylic acids and carbohydrates, are excellent candidates as deep eutectic solvents. Furthermore, we conclude that polycarboxylic acids are useful additions to the toolbox of sugar replacers, albeit that there are some limitations to their amounts used.

In this study we report on the analysis of dust formation, a quality problem arising in the industrial processing of par-fried, frozen french fries. This dust constitutes fractured pieces broken off the crust during finish frying. We claim that this dust problem has many similarities with flaking arising during the final-baking of par-baked french baguettes, i.e. the two problems are governed by the same physical principles. Inspired by the hypotheses behind flaking, we have made an experimental design, where we have perturbed the operating conditions of an industrial processing line of french fries. The measured dust during finish frying is correlated with the physical properties of the crust, measured in the different unit operations of the industrial processing line, and the operating conditions. We have shown that dust is non-linearly correlated to 1) the moisture content of the crust as influenced by drying and par-frying, and 2) the freezing rate in the industrial tunnel freezer. Remarkably, the amount of dust decrease with the increase of frozen storage time, which we have explained via viscoelastic relaxation of locked-in stress - mediated by moisture migrating from core to crust. This decay is shown to be independent of pretreatments, which only determines its starting value. With the given relations industry can in principle control the dust problem, but these measures have to be weighed against their effects on other objectives of the industry.

In this paper we describe the chemical reactions of leavening agents in baking biscuits on a sound thermodynamic basis. The model is part in a sequel targetted at physical understanding of biscuit baking with the purpose of reformulation of biscuits with respect to sucrose and sodium levels. The chemical leavening gases, CO2 and NH3, originate from the dissociation of sodium and ammonium bicarbonate. Next to water vapour, these produced gases create gas bubbles in the biscuit dough. The concentrations of the leavening agents and added salt lead to high ionic strength. Consequently, the activities of ions participating in the leavening reaction deviate strongly from ideality. The non-idealities are described using the Pitzer equations. The values of many parameters of the Pitzer model and equilibrium constants are obtained from the strong developed field of CO2 sequestering in ammonia solutions. The model describing the chemical reactions is coupled to a cell model describing the expansion of gas bubbles. Model simulations show that most of the produced gas originates from the bicarbonate, and the ammonium contributes significantly less. The functionality of ammonium as leavening agent is not quite clear, but it may help in reducing sodium levels.

In this paper, we present the rich physics and chemistry of the gastric digestion of protein gels. Knowledge of this matter is important for the development of sustainable protein foods that are based on novel proteins sources like plant proteins or insects. Their digestibility is an important question in the design of these new protein foods.As polyelectrolyte gels, they can undergo volume changes upon shifts in pH or ionic strengths, as protein gels experience when entering the gastric environment. We show that these volume changes can be modelled using the Flory-Rehner theory, combined with Gibbs-Donnan theory accounting for the distribution of electrolytes over gel and bath. In-vitro experiments of soy protein gels in simulated gastric fluid indeed show intricate swelling behaviour, at first the gels show swelling but at longer times they shrink again. Simulations performed with the Flory-Rehner/Gibbs-Donnan theory reproduce qualitatively similar behaviour. In the final part of the paper, we discuss how the model must be extended to model realistic conditions existing in the in-vivo gastric environment.