Ultra-processed foods: Processing versus formulation.

The four-tiered NOVA food classification defines foods based on their degree of processing and ranges from native unprocessed foods to so-called "ultra-processed" foods. Recent publications have suggested that foods classified as ultra-processed are unhealthy and contribute to the obesity epidemic. It is important to distinguish between formulation and processing of a food. In most cases it is the formulation more than the processing that results in foods that are not recommended as part of a healthy diet. Such "ultra-formulated" foods are unhealthy because they are high in added sugar and other caloric sweeteners, refined flours saturated fats and salt to increase palatability. The understanding that processing and formulation are distinct will assist health professionals in identifying the types of foods that are unhealthy and contribute to overconsumption and obesity. It furthermore will help to destigmatize food technology and promote discussions amongst health professionals, food scientists, corporate scientists, government officials and the general public. Novel food processing techniques are urgently needed in times of population growth, climate change and war-induced food shortages.

Texturization of pea protein isolate by micro compounding.

Twin-screw micro compounding is introduced as a novel technique to process and characterize small plant protein samples under conditions that are relevant for meat analogue processing. Small samples of pea protein isolate (PPI) (5 cm3, corresponding to ∼7 g of hydrated sample) are batch-processed at water contents between 40 and 70 % w/w and temperatures between 90 and 120 °C. Screw speed (100-400 rpm) and residence time (1-9 min) are varied resulting in values of the specific mechanical energy (SME) between ∼20 and 2000 kJ/kg, which is the range relevant for plant protein extrusion. Micro compounding process data provides information on several aspects of the rheological behavior of PPI. Shear thinning behavior is observed for PPI. The viscosity of the PPI during micro compounding was found to exponentially decrease with water content. The temperature dependence is consistent with an Arrhenius-type model. The extruded strands (length: ∼15 cm; diameter: 3.0 ± 0.2 mm) are characterized by scanning electron microscopy (SEM), differential solubility, water holding capacity (WHC), and texture profile analysis (TPA). The hardness as determined from TPA increases linearly with screw speed and residence time, jumps to higher values above the denaturation temperature of the PPI and decreases exponentially with the water content during processing. Micro compounding is found to be a useful technique to convert small plant protein samples at water contents between about 40 and 60 % w/w into texturized matrices and investigate the rheological behavior of plant protein isolates under conditions that are relevant for extrusion processing.

Rheology of carbohydrate blends close to the glass transition: Temperature and water content dependence of the viscosity in relation to fragility and strength.

Several modifications of the Williams-Landel-Ferry (WLF) equation that incorporate the water-content dependence of the viscosity are introduced and applied to the fitting the zero-shear viscosity of a systematic series of maltopolymer-maltose blends for water contents w between 4% and 70% (M. Dupas-Langlet et al., Carbohydrate Polymers 213 (2019) 147-158). These models include a previously published model that addresses the water-content dependence of the viscosity via a Gordon-Taylor-type modification of the C2 coefficient of the WLF equation. New models that are based on two simple assumptions are introduced: 1. The viscosity at the glass transition temperature Tg decreases exponentially with the water content and 2. The WLF coefficient C2 depends linearly on the water content. The modified WLF models allow to extract the so-called isoviscosity lines, that connect points of varying temperature and water content that are characterized by the same viscosity. Based on data obtained between T = -15 °C and 70 °C using shear rheology (w = 30-70% w/w) and dynamic mechanical thermal analysis (w = 4-9% w/w), we conclude that the models provide a good fit of the experimental data, and that additional data, specifically very close to the glass transition line, is needed, to assess the hypotheses underlying the various modified WLF models. It is established that the viscosity at Tg is dependent on the composition and decreases with the content of maltose and water. The modified WLF models are used to determine Angell's fragility parameter m and Roos' strength parameter S. m and S are observed to increase, respectively decrease with increasing water and maltose content, signifying an increasing temperature dependence of the viscosity close to Tg with decreasing diluent content. The application of the isoviscosity concept to unit operations in the food and pharmaceutical industry is discussed. Specifically, we show how to analyze atomization, agglomeration, sintering and compaction using the isoviscosity concept.

Antiplasticization and phase behavior in phase-separated modified starch-sucrose blends: A positron lifetime and solid-state NMR study.

Interactions, organization and dynamics within phase-separated ternary blends of hydrophobically modified starch (HMS), sucrose and water are investigated using solid-state NMR and positron annihilation lifetime spectroscopy (PALS). Antiplasticization of HMS by sucrose is demonstrated by PALS and 1H NMR T1 measurements. Selective solid-state 13C NMR experiments show that a large fraction of sucrose is in molecular contact with HMS even at high sucrose contents, indicating that the HMS-sucrose phase separation is only partial. Sucrose is observed to migrate away from the HMS-rich domains at temperatures that are above the lower Tg, but still below the upper Tg. 1H spin diffusion experiments indicate that phase separation occurs on a nanometric scale, in line with recent theory (Van der Sman, Food Hydrocolloids87, 360-370 (2019)). We infer that the nanoscale structure of the HMS-rich phase allows for intimate molecular contact between the HMS-rich and the sucrose-rich phases and explains the unusual dynamic behavior.

Influence of blend ratio and water content on the rheology and fragility of maltopolymer/maltose blends.

The rheological behavior of blends of a fractionated maltopolymer (Mw = 1.4⋅104 Da) and the disaccharide maltose is investigated as a function of water content and temperature, with emphasis on the viscosity and molecular relaxations in the approach to the glass transition. Shear rheology is combined with dynamic mechanical thermal analysis to probe viscosities between 1 mPa s and 1012 Pa s. Differential scanning calorimetry is used to determine glass transition and enthalpy relaxation of the carbohydrate blends. The rheology data are fitted with a modified version of Williams-Landel-Ferry equation (Williams et al., 1955). The fragility of the blends is quantified using Angell's fragility parameters m and F1/2 (Angell, 1991) and Roos' strength parameter S (Roos, 1995b). The increase in fragility of the maltopolymer systems with increasing water and maltose contents is interpreted as a reduction of the entanglement density and an interference of water molecules with the hydrogen bonding between the carbohydrate chains.

Water vapor sorption and glass transition temperatures of phase-separated amorphous blends of hydrophobically-modified starch and sucrose.

This article contains water vapor sorption data obtained on amorphous blends of octenyl succinic acid-modified (denoted as hydrophobically modified starch; HMS) and sucrose (S) in the anhydrous weight HMS/S ratios between 100/0 and 27/75. The water vapor sorption data was obtained gravimetrically. The amorphous state of the blends was confirmed by X-ray diffraction. The glass transition temperatures of the phase-separated blends are listed; the blends show phase separation into a sucrose-rich phase and a HMS-rich phase, the composition of which varies with the blend ratios. The sucrose-rich phase is characterized by a glass transition temperature T g,lower that is 40 to 90 K lower than the glass transition temperature T g,upper of the HMS-rich phase.

Phase separation in amorphous hydrophobically modified starch-sucrose blends: Glass transition, matrix dynamics and phase behavior.

The phase behavior and matrix dynamics of amorphous blends of octenyl succinic anhydride (OSA) modified starch and sucrose was studied as function of blend composition and water content. Phase separation into two amorphous phases, one enriched in OSA starch and the other in sucrose, was confirmed by differential scanning calorimetry (DSC). DSC and 1H solid-state NMR show that the phase separation is only partial. The glass transition temperature (Tg) of the OSA starch-rich phase was found to be ∼30-100 K higher than the Tg of the sucrose-rich phase, depending on blend composition and water content. A novel type of coupling between changes in physical state of the sucrose-rich phase and plasticizer redistribution is proposed, leading to an unexpected increase of the glass transition temperature of the modified starch-rich phase at higher matrix water contents. A quantitative model for the phase separation of the anhydrous blends into two amorphous phases is presented. The model predicts that, with increasing blend sucrose content, the weight fraction of the sucrose-rich phase decreases, while the sucrose content of both the OSA starch-rich phase and the sucrose-rich phase increases. This novel phenomenon is relevant in the understanding of the stability and performance of multiphase food and pharmaceutical components.

Structural and thermodynamic aspects of plasticization and antiplasticization in glassy encapsulation and biostabilization matrices.

The structural and thermodynamic properties of glassy carbohydrate matrices for the encapsulation and biostabilization of sensitive bioactive compounds, such as pharmaceutically active proteins and oxidation-sensitive compounds, are reviewed in the context of the plasticization and antiplasticization of glassy carbohydrates of intermediate and high molecular weight by low molecular weight diluents. Plasticization and antiplasticization may be monitored either by dynamic measures or by structural and thermodynamic features of the glassy matrices. Specifically, it is demonstrated that the decrease in size of the molecular free volume holes with increasing diluent content, as determined by positron annihilation lifetime spectroscopy (PALS), is related to the antiplasticization of glassy carbohydrate matrices, resulting in increased barrier properties of the glassy matrix. As far as could be ascertained from the available data, the regimes as identified by PALS map on those detected by neutron scattering and dielectric spectroscopy for glassy matrices consisting of trehalose and the diluent glycerol. The review is concluded by a survey of the published results on the stability of bioactive compounds encapsulated in carbohydrate glasses and an overview of outstanding questions.

Hydrogen bonding in maltooligomer-glycerol-water matrices: Relation to physical state and molecular free volume.

We use Fourier Transform Infra Red (FTIR) Spectroscopy to explore the effects of water and glycerol on the hydrogen bonding of low water content maltooligomer matrices by monitoring the shifts in the position of the peak associated with the fundamental stretching vibration of the hydroxyl groups, νOH. Changes in hydrogen bonding are investigated in relation to the physical state and the molecular packing of the maltooligomer matrices, which are measured by Positron Annihilation Lifetime Spectroscopy (PALS). In the concentration range studied (0-20 wt.%), glycerol acts as an anti-plasticizer whereby it reduces the average molecular hole size, vh, while modulating the hydrogen bond network of the carbohydrate matrices. Depending on the level of hydration, water can cause anti-plasticization or plasticization of the maltooligomer-glycerol matrices. For water contents below ∼ 5 wt.%, water acts as an anti-plasticizer, whereby it reduces vh and we measure a reduction νOH. At higher water contents, water acts as a plasticizer, causing a systematic increase in vh, while νOH continues to decrease as a function of increasing water content.

Soft matter approaches to structured foods: from "cook-and-look" to rational food design?

Developments in soft matter physics are discussed within the context of food structuring. An overview is given of soft matter-based approaches used in food, and a relation is established between soft matter approaches and food technology, food creation, product development and nutrition. Advances in food complexity and food sustainability are discussed from a physical perspective, and the potential for future developments is highlighted.

Delivery of Functionality in Complex Food Systems: Physically Inspired Approaches from Nanoscale to Microscale, Wageningen 18-21 October 2009.

The Wageningen Delivery of Functionality symposium covered all aspects involved with food structural design to arrive at high-quality foods which meet demanding customer expectations and regulatory requirements. The symposium integrated aspects from the structural organization of foods at molecular and supramolecular scales to dedicated techniques required to describe and visualize such structures, the gastro-intestinal events and how to model these in a laboratory setting, and finally the impact those food structures and ingredients have on the consumer's physiology and on the human perception. As an interdisciplinary platform, bringing together more than 160 researchers from academia and industry, the symposium meanwhile fulfills an important role in the food science community.

Plasticization, antiplasticization, and molecular packing in amorphous carbohydrate-glycerol matrices.

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.

Specific volume-hole volume correlations in amorphous carbohydrates: effect of temperature, molecular weight, and water content.

The specific volume and the nanostructure of the free volume of amorphous blends of maltose with a narrow molecular weight distribution maltopolymer were systematically studied as a function of temperature, water content, pressure, and blend composition. Correlations between the hole free volume and the specific volume were investigated in the glassy and rubbery phases and in solution using positron annihilation lifetime spectroscopy (PALS) and pressure-volume-temperature (PVT) measurements, with the aim to provide a consolidated mechanistic understanding of the relation between changes in molecular packing and at the molecular level and the behavior of the specific volume at the macrolevel. Both specific volume and hole volume show a linear dependence on the temperature, but with a slope which is higher in the rubbery state than in the glassy state. As a function of temperature, the hole volume and the specific volume are linearly related, with no discontinuity at the glass transition temperature (T(g)). In the glassy state, both the specific volume and the hole volume decrease nonlinearly with the addition of maltose to the maltopolymer matrix, due to a more efficient molecular packing. For variations in carbohydrate composition, a linear dependence between the hole volume and the specific volume was again observed. The role of water was found to be significantly more complex, with increasing water content causing an increase in density in both the glassy and rubbery phases indicating that water exists in a highly dispersed state with a significantly lower specific molar volume than in bulk water. At very low water contents, the hole volume and the specific volume both decrease with increasing water content, which suggests that water acts as both a hole filler and a plasticizer. In the glassy state at slightly higher water contents, the specific volume continues to slowly decrease, but the hole size passes through a minimum before it starts to increase. This gives rise to a negative correlation between the hole volume and the specific volume which has not previously been observed and which can be interpreted in terms of water molecules which are dispersed within the glassy carbohydrate matrix and which thereby influence the hydrogen bonding between the carbohydrate molecules.

Food structure and functionality: a soft matter perspective.

The structure and functionality of foods are described from the perspective of recent advances in soft condensed matter physics. An overview is given of the structure and properties of food materials in terms of the physically relevant length scales. Recent developments in the understanding of the physics of gels, micelles, liquid crystals, biopolymer complexes and amorphous carbohydrates are presented.

Molecular packing in amorphous carbohydrate matrixes.

The molecular packing of bidisperse matrixes of amorphous carbohydrates consisting of a fractionated maltopolymer supplemented with various amounts of the disaccharide maltose is investigated by combining Positron Annihilation Lifetime Spectroscopy (PALS) with specific volume measurements. The maltopolymer-maltose blends are equilibrated at a range of water activities between 0 and 0.75 at 25 degrees C in order to investigate the effect of water content and carbohydrate molecular weight distribution on the size of the molecular free volume holes in both the glassy and rubbery states. In the rubbery state, the size of the intermolecular holes is only very weakly dependent on the carbohydrate molecular weight, provided that the carbohydrate blends are analyzed at the same water content. In contrast, in the glassy state, significant differences in the size of the free volume holes are observed between the various blends at constant water content. Both the specific volume and the hole volume decrease with increasing maltose content, initially rapidly up to a maltose content of about 40 wt % on total carbohydrate. In addition, we find that the role of water as a plasticizer and matrix constituent is a complex one. At very low water contents, water acts by filling the free volume holes between the carbohydrate molecules. This hole-filling mechanism could well be related to the phenomenon of anti-plasticization observed before. At higher water contents, corresponding generally to water activities above 0.11 at 25 degrees C, water conversely increases the average hole volume in the carbohydrate matrixes, most likely caused by water interfering with the hydrogen bonding between the carbohydrate molecules, leading to a local expansion of the molecular packing.

Sorption of water by bidisperse mixtures of carbohydrates in glassy and rubbery states.

Water sorption by bidisperse carbohydrate mixtures consisting of varying ratios of a narrow-molecular-weight distribution maltopolymer and the disaccharide maltose is investigated to establish a quantitative relation between the composition of the carbohydrate system and the water sorption isotherm. The sorption of water is approached from two limiting cases: the glassy state at low water content and the dilute aqueous carbohydrate solution. In the glassy state, the water content at a given water activity decreases with increasing maltose content of the matrix, whereas in the rubbery state it increases with increasing maltose content. The water sorption behavior in the glassy state is quantified using a variety of models, including the often-utilized but physically poorly founded Guggenheim-Anderson-de Boer model, several variants of the free-volume theory of sorption by glassy polymers, and a two-state sorption model introduced in the present paper. It is demonstrated that both the free-volume models and the two-state sorption model, which all encompass the Flory-Huggins theory for the rubbery-state sorption but which differ in their modeling of the glassy-state sorption, provide a physically consistent foundation for the analysis of water sorption by the carbohydrate matrixes.

Organization and mobility of water in amorphous and crystalline trehalose.

The disaccharide trehalose is accumulated by microorganisms, such as yeasts, and multicellular organisms, such as tardigrades, when conditions of extreme drought occur. In this way these organisms can withstand dehydration through the formation of an intracellular carbohydrate glass, which, with its high viscosity and hydrogen-bonding interactions, stabilizes and protects the integrity of complex biological structures and molecules. This property of trehalose can also be harnessed in the stabilization of liposomes, proteins and in the preservation of red blood cells, but the underlying mechanism of bioprotection is not yet fully understood. Here we use positron annihilation lifetime spectroscopy to probe the free volume of trehalose matrices; specifically, we develop a molecular picture of the organization and mobility of water in both amorphous and crystalline states. Whereas in amorphous matrices, water increases the average intermolecular hole size, in the crystalline dihydrate it is organized as a confined one-dimensional fluid in channels of fixed diameter that allow activated diffusion of water in and out of the crystallites. We present direct real-time evidence of water molecules unloading reversibly from these channels, thereby acting as both a sink and a source of water in low-moisture systems. We postulate that this behaviour may provide the overall stability required to keep organisms viable through dehydration conditions.

Influence of fermentation medium composition on physicochemical surface properties of Lactobacillus acidophilus.

The effect of the simple and complex basic components of a fermentation medium on the surface properties of Lactobacillus acidophilus NCC2628 is studied by physicochemical methods, such as electrophoresis, interfacial adhesion, and X-ray photonelectron spectroscopy, and by transmission electron microscopy. Starting from an optimized complete medium, the effect of carbohydrates, peptones, and yeast extracts on the physicochemical properties of the cell wall is systematically investigated by consecutively omitting one of the principal components from the fermentation medium at the time. The physicochemical properties and structure of the bacterial cell wall remain largely unchanged if the carbohydrate content of the fermentation medium is strongly reduced, although the concentration of surface proteins increases slightly. Both peptone and yeast extract have a considerable influence on the bacterial cell wall, as witnessed by changes in surface charge, hydrophobicity, and the nitrogen-to-carbon ratio. Both zeta potential and the cell wall hydrophobicity show a positive correlation with the nitrogen-to-carbon ratio of the bacterial surfaces, indicative of the important role of surface proteins in the overall surface physical chemistry. The hydrophobicity of the cell wall, which is low for the cultures grown in the complete medium and in the absence of carbohydrates, becomes fairly high for the cultures grown in the medium without peptones and the medium without yeast extract. UV spectrophotometry and sodium dodecyl sulfate-polyacrylamide gel electrophoresis combined with liquid chromatography-tandem mass spectrometry are used to analyze the effect of medium composition on LiCl-extractable cell wall proteins, confirming the major change in protein composition of the cell wall for the culture fermented in the medium without peptones. In particular, it is found that expression of the S-layer protein is dependent on the protein source of the fermentation medium.

Probing bacterial interactions: integrated approaches combining atomic force microscopy, electron microscopy and biophysical techniques.

Recent developments in the application of Atomic Force Microscopy (AFM) and other biophysical techniques for the study of bacterial interactions and adhesion are discussed in the light of established biological and microscopic approaches. Whereas molecular-biological techniques combined with electron microscopy allow the identification and localization of surface constituents mediating bacterial interactions, with AFM it has become possible to actually measure the forces involved in bacterial interactions. Combined with the flexibility of AFM in probing various types of physical interactions, such as electrostatic interactions, specific ligand-receptor interactions and the elastic forces of deformation and extension of bacterial surface polymers and cell wall, this provides prospects for the elucidation of the biophysical mechanism of bacterial interaction. However, because of the biochemical and a biophysical complexity of the bacterial cell wall, integrated approaches combining AFM with electron microscopy and biophysical techniques are needed to elucidate the mechanism by which a bacterium interacts with a host or material surface. The literature on electron microscopy of the bacterial cell wall is reviewed, with particular emphasis on the staining of specific classes of cell-wall constituents. The application of AFM in the analysis of bacterial surfaces is discussed, including AFM operating modes, sample preparation methods and results obtained on various strains. For various bacterial strains, the integration of EM and AFM data is discussed. Various biophysical aspects of the analysis of bacterial surface structure and interactions are discussed, including the theory of colloidal interactions and Bell's theory of cell-to-cell adhesion. An overview is given of biophysical techniques used in the analysis of the properties of bacterial surfaces and bacterial surface constituents and their integration with AFM. Finally, we discuss recent progress in the understanding of the role of bacterial interactions in medicine within the framework of the techniques and concepts discussed in the paper.