Oral Breakdown Research Articles

Oral structural breakdown and sensory perception of plant-based emulsions

Emulsion-based matrices correspond to an interesting structure for designing healthy and plant-based foods since they can simulate the texture of traditional foods, protect lipids from oxidation, and carry bioactive compounds. However, oral processing could modify their structure, affecting their sensory performance. So, it is necessary to understand the changes that occur during food consumption and their relationship with sensory perception. For that purpose, this research aimed to study the effect of droplet size and thickener type of plant-based emulsions on their structural breakdown under oral conditions and their sensory perception. Four oil-in-water (O/W) emulsions with different droplet sizes (nanoemulsions and conventional emulsions) and thickener types (starch and xanthan gum) were prepared. In vitro oral structural breakdown of emulsions was characterized using a rheological approach (saliva + sharing). The samples were later subjected to a sensory evaluation of aroma, flavor, consistency, and creaminess intensity by multiple paired comparison test (n = 50). Results showed different oral breakdown patterns due to droplet size and thickener type. Xanthan gum matrices were less susceptible to structure breakdown than starch-based matrices, particularly those with microscale droplet size (emulsions), due mainly to salivary α-amylase activity. Regarding sensory perception, xanthan gum-based matrices were perceived to have a higher consistency (nanoemulsion) and creaminess (conventional emulsion) than starch-based ones. Meanwhile, starch-based samples showed higher flavor (nanoemulsion) and aroma intensities (conventional emulsion). Therefore, the sensory characteristics of plant-based emulsions can be modulated by thickener type and droplet size. For example, xanthan gum-based nanoemulsions can increase the perceived consistency, while starch-based emulsions can increase the perceived flavor intensity.

Impact of Lallemantia royleana seed mucilage on the physicochemical, textural, rheological, and in-mouth breakdown behavior properties of cold-set whey protein isolate emulsion-filled gel

This work focused on the Lallemantia royleana seed mucilage (LRSM) effect on the rheological, physicochemical, and microstructural attributes, and the in vivo oral breakdown of cold-set emulsion-filled gel (EFG) based on the whey protein isolate (WPI). Emulsions containing 0.1 and 0.5% LRSM displayed the largest and smallest droplet sizes (3.38 vs. 1.26 μm) and polydispersity index (0.60 vs. 0.23), respectively. Also, the 0.1–0.5% LRSM-WPI EFGs compared to the control had greater elastic modulus in the linear viscoelastic (LVE) region (7006.1–7167.8 vs. 4438.3 Pa), flow-point stress (484.6–540.1 vs. 327.8 Pa), network strength (7227.8–7451.2 vs. 5380.1 Pa.s1z), network extension (10.91–11.44 vs. 10.05), lower LVE limit (1.74–2.26 vs. 2.53 %), same loss tangent (0.17), similar frequency dependence of elastic modulus (0.087–0.091 vs. 0.095), and inhomogeneous microstructures. Hardness, springiness, and chewiness at 0.1% and adhesiveness and cohesiveness at 0.5% LRSM-WPI EFGs were the highest. Raising the LRSM from 0% to 0.5% improved the water-holding capacity (75.49%–87.68%), swelling ratio (0.20%–2.59%), and decreased syneresis (11.08%–9.13%). The 0.5% LRSM-WPI EFG compared to the control needed a higher chew duration (16.22 vs. 11.80 s) and chew cycle (24.76 vs. 18.31), and its bolus had a smaller particle size (0.94 vs. 1.65 mm).

Experimental and computational models for simulating the oral breakdown of food due to the interaction with molar teeth during the first bite

The first bite involves the structural breakdown of foods due to the interaction with teeth and is a crucial process in oral processing. Although in vitro experiments are useful in predicting the oral response of food, they do not facilitate a mechanistic understanding of the relationship between the intrinsic food mechanical properties and the food behaviour in the oral cavity. Computer simulations, on the other hand, allow for such links to be established, offering a promising design alternative that will reduce the need for time consuming and costly in vivo and in vitro trials. Developing virtual models of ductile fracture in soft materials, such as food, with random and non-predefined crack morphology imposes many challenges. One of the most important is to derive results that do not depend on numerical parameters, such as Finite Element (FE) mesh density, but only physical constants obtained through independent standard mechanical tests, such as fracture strain and/or critical energy release rate. We demonstrate here that this challenge can be overcome if a non-local damage approach is used within the FE framework. We develop a first bite FE modelling methodology that provides mesh independent results which are also in agreement with physical first bite experiments performed on chocolate. The model accounts for key features found in chocolate and a wide range of compliant media, such as rate dependent plasticity and pressure dependent fracture initiation strain. As a result, our computational methodology can prove valuable in studying food structure-function relationships that are essential in product development.

In vivo oral breakdown properties of whey protein gels containing OSA-modified-starch-stabilized emulsions: Impact of gel structure

This study investigated the effects of gel structure on the in vivo oral breakdown properties of whey protein gels containing emulsion droplets stabilized by octenyl succinic anhydride (OSA)-modified starches. The gel structure was manipulated by the degree of substitution (DS) of the OSA-modified starch and the salt concentration. Rheological measurements showed that, when the DS or the NaCl concentration increased, the storage modulus, hardness and Young's modulus of the gels increased. Hard gels (100 mM NaCl) required more chewing cycles than soft gels (10 mM NaCl), which led to smaller mean particle size (d50) of the bolus. Correlation analysis showed that d50 had an excellent power-law relationship with hardness and Young's modulus, whereas it had a positive linear relationship with fracture force and fracture strain. This indicated that the physical/mechanical properties of the gel were the critical factors that determined the bolus particle size. During oral processing, there were no significant changes in the microstructures of the gels and only very few oil droplets were released from the protein matrix, suggesting that the OSA-modified-starch-stabilized emulsion droplets remained bound within the whey protein gel matrix.

In-mouth breakdown behaviour and sensory perception of emulsion gels containing active or inactive filler particles loaded with capsaicinoids

This work investigated the effects of active versus inactive filler particles on the structure, rheological properties, in vivo oral breakdown behaviour and sensory perception of emulsion gels containing capsaicinoids (CAPs). CAP-loaded Tween-80-coated emulsion droplets were not bound with the whey protein matrix (i.e. emulsion gels containing inactive filler particles) and appeared to be flocculated and inhomogeneously distributed in the gel matrix, which led to drastically decreased mechanical gel strength. CAP-loaded Tween 80 emulsion gels had significantly lower fracture stress and fracture stain than CAP-loaded whey protein emulsion gels (emulsion gels containing active filler particles), indicating that they were more easily broken down into small fragments in the mouth at small deformations with less chewing (i.e. lower fracture energy, fewer chewing cycles and shorter duration). During mastication, large amounts of oil droplets were released from the gel matrix of the CAP-loaded Tween 80 emulsion gels, which also contributed to their significantly smaller bolus particle size. The released oil droplets from the CAP-loaded Tween 80 emulsion gels facilitated bolus formation through lubrication and decreased the chewing cycles. A higher degree of fragmentation led to greater surface exposure (i.e. new surface area created) during mastication, and therefore to higher mouth burn perception. The large amounts of oil droplets released from the gel matrix during mastication and the inhomogeneous distribution of the oil droplets because of flocculation of the CAP-loaded Tween 80 emulsion gels also contributed to their higher mouth burn perception. The oral processing behaviour of the CAP-loaded emulsion gels and the sensory perception of capsaicinoids could be tuned by manipulating the droplet-matrix interactions and the gel structure.

The dynamics of starch hydrolysis and thickness perception during oral processing

While it is known that salivary amylase changes perceived thickness in starch-based foods, the dynamics of oral breakdown of starch has not been related to that of sensory perception. This work examines the associations between in-mouth oral breakdown of starch by α-amylase and thickness of a semisolid product measured instrumentally and using a sensory panel. Pureed carrots made with added waxy maize (w/w) (0% (control), 0.4% (S0.4) and 0.8% (S0.8)), were tested for dilution and hydrolysis effects with the addition of water and saliva and measuring viscosity (shear of 10 s−1), viscoelasticity (10–0.01 Hz at 0.1% strain) and maltose release. Sensory testing was conducted using progressive profiling. Control and S0.8 pureed carrots showed similar viscosities at 10 s−1 while S0.4 was lower. Addition of saliva had the highest impact on viscosity drop for S0.8. Viscoelastic properties of pureed carrots decreased with starch addition which decreased further with water/saliva incorporation. Starch breakdown measured in terms of maltose release did not change with starch concentration and oral processing times. Unlike instrumental viscosity results, perceived thickness of purees increased with starch concentration. During oral processing, thickness decreased at a constant rate across all samples highlighting the dilution effect of saliva. A relation was observed only between oral viscosity and starch hydrolysis and not rheological measurements. This indicates that changes in starch hydrolysis during oral processing can be used as an indicator of rate of drop in perceived viscosity in starch-based semi-solid foods such as pureed carrots.

Characterization of the oral breakdown, sensory properties, and volatile release during mastication of white bread

The oral breakdown, sensory properties, and volatile release during mastication of white bread were investigated. The results of correlation analysis for white bread’s physical properties and it’s oral physiological parameters during chewing have elucidated that bread’s physical properties determined the oral processing behavior. During chewing of white bread, 15 dominant ions with regularly changing patterns were monitored by proton transfer reaction–mass spectrometry (PTR–MS). These dominant ions derived from 32 volatile compounds were further confirmed by pure standards. Partial least squares regression (PLSR) analysis was used to explore the positive correlations between the sensory analysis and the dominant aroma compounds. Results have shown that 9 aroma compounds were predicted as the potent odorants contributing to the changes in aroma profiles. Finally, 3-hydroxy-2-butanone, 2-methyl-1-propanol, and heptanoic acid were confirmed as the key aroma compounds contributing to the changes in aroma profiles of white bread before and after chewing.

Toughening and stiffening of starch food extrudates through the addition of cellulose fibres and minerals

Pet food, one of the largest type of commercial packaged foods, continuously sets new challenges, amongst them the possibility to enhance palatability via adjusting product composition. This will optimise texture perception across consumer groups of diverse chewing capabilities, as well as improve food oral breakdown efficiency with further impact on metabolic health and nutrient bioavailability in the digestive process. Our aim is to pioneer new methods of controlling texture by answering longstanding questions such as the impact of nutrients on the mechanical properties of foods. The impact of cellulose fibres and minerals on the fracture toughness and stiffness properties of starch food extrudates is investigated for the first time through employing tensile tests and two fracture toughness tests namely Essential Work of Fracture (EWF) and cutting, on four different compositions. Fibres alone are found to increase stiffness (stiffening) and toughness (toughening) whereas minerals decrease stiffness (softening) with a minor influence on toughness. Interestingly, fibres and minerals combined maximise toughening at 28% compared to pure starch, due to the synergistic effect of fibre-matrix de-bonding and fibre breakage mechanisms at the crack tip. These new results indicate that texture can be significantly altered through the addition of minerals and short fibres. Such information is critical in the design of products that need to satisfy both nutritional and textural criteria.

On modeling the large strain fracture behaviour of soft viscous foods

Mastication is responsible for food breakdown with the aid of saliva in order to form a cohesive viscous mass, known as the bolus. This influences the rate at which the ingested food nutrients are later absorbed into the body, which needs to be controlled to aid in epidemic health problems such as obesity, diabetes, and dyspepsia. The aim of our work is to understand and improve food oral breakdown efficiency in both human and pet foods through developing multi-scale models of oral and gastric processing. The latter has been a challenging task and the available technology may be still immature, as foods usually exhibit a complex viscous, compliant, and tough mechanical behaviour. These are all addressed here through establishing a novel material model calibrated through experiments on starch-based food. It includes a new criterion for the onset of material stiffness degradation, a law for the evolution of degradation governed by the true material’s fracture toughness, and a constitutive stress-strain response, all three being a function of the stress state, i.e., compression, shear, and tension. The material model is used in a finite element analysis which reproduces accurately the food separation patterns under a large strain indentation test, which resembles the boundary conditions applied in chewing. The results lend weight to the new methodology as a powerful tool in understanding how different food structures breakdown and in optimising these structures via parametric analyses to satisfy specific chewing and digestion attributes.

Effect of marbling on volatile generation, oral breakdown and in mouth flavor release of grilled beef

While the positive effect of intramuscular fat (IMF) on beef tenderness is well-established, its role in flavor generation and flavor release is less defined. To increase understanding, real-time volatile generation was monitored during grilling of beefsteaks (grass and grain-fed Angus and grass-fed Wagyu) with different amounts of IMF by proton transfer reaction mass spectrometry. Volatile concentration increased significantly (p<0.001) when the IMF was >~10%, but did not differ (p>0.05) at lower IMF levels (5.2–10.2%). In vivo release of volatiles during consumption of grilled steaks was also measured using human subjects. Pre- and postswallow volatile release profiles varied according to marbling level and volatile fat solubility. In-mouth release of key hydrophilic volatiles was significantly greater (p<0.05) in high IMF grilled beef, consistent with more intense sensory flavor. Faster oral breakdown and higher peak saliva concentrations of non-volatile flavor compounds in high IMF grilled beef were consistent with higher tenderness and more intense flavor perception.

Effects of structural and textural properties of brittle cereal foams on mechanisms of oral breakdown and in vitro starch digestibility

Structural and textural properties as well as the dietary fibre content of solid cereal foams influence the oral breakdown of structure, bolus formation and digestibility. The aim of this study was to investigate how structural differences of solid cereal foams (puffs vs. flakes) affect in vivo chewing and in vitro starch digestion. Four extruded puffs and flakes were produced from endosperm rye flour by extrusion processing without or with 10% rye bran (RB) addition. Extruded puffs and flakes were masticated by fifteen healthy females and the process was monitored using electromyography. Extruded puffs were more porous than flakes (97% vs 35%). The two products were also significantly different (p<0.05) in their structural and textural properties such as expansion, hardness, density and crispiness. A negative correlation was observed between hardness and crispiness index (p<0.05, r=−0.950) and density and porosity (p<0.05, r=−0.964). Addition of 10% RB had a significant effect on structural, textural and mastication properties both for puffs and flakes. Mastication of puffs required less total work than flakes (204 vs. 456%) and they were degraded to smaller particles than flakes during mastication. Irrespectively of the considerable differences in structure, texture and oral disintegration process, no significant (p<0.05) differences were observed between puffs and flakes (86.4 vs. 85.1) in terms of starch hydrolysis index. RB addition increased the hydrolysis index of puffs and flakes to 89.7 and 94.5, respectively, which was probably attributable to the increased number of particles in the bolus.

Bolus matters: the influence of food oral breakdown on dynamic texture perception.

This review article focuses on design of food structure, characterisation of oral processing by boli characterisation and dynamic texture perception. Knowledge of the food properties governing bolus formation and bolus properties determining temporal changes in texture perception is of major importance. Such knowledge allows academia to better understand the mechanisms underlying texture perception and food industry to improve product texture. For instance, such knowledge can be used for developing foods with desired texture perception that fit in a healthy diet or that are customized to specific consumer groups. The end point of oral processing is the formation of a safe-to-swallow bolus. The transitions of solid and soft solid foods into bolus are accompanied by tremendous modifications of food properties. The review discusses dynamic changes in bolus properties resulting in dynamic changes of texture perception during oral processing. Studies monitoring chewing behaviour are discussed to complement the relationships between bolus properties and dynamic texture perception. We conclude that texture perception evolves over mastication time and depends on food properties, such as mechanical properties, mainly in the beginning of oral processing. Towards the middle and end of oral processing, bolus properties depend on food properties and explain texture perception better than food properties.

WITHDRAWN: Effects of structural and mechanical textural properties of brittle cereal foams on mechanisms of oral breakdown

WITHDRAWN: Effects of structural and mechanical textural properties of brittle cereal foams on mechanisms of oral breakdown

Investigation of oral gels breakdown using image analysis

Characterizing the dynamics of food oral breakdown is of interest to understand the temporal perception of food products. The present work aimed at studying the possible contribution of artificial vision for studying bolus formation. Four emulsion-filled gels were prepared from two concentrations of agar and gelatin. By combining two different layers of these gels, four samples of homogeneous composition and 6 samples of heterogeneous composition were prepared. The layers were colored independently in order to study their breakdown and mixing during oral processing. Images of spat out boluses were collected at different stages of the chewing process and studied by different image analysis methods: gray-level histograms, histogram of shape area, mathematical morphology and gray level co-occurrence matrix. Methods were compared for their ability in discriminating boluses as function of homogeneous gel composition and mastication time. Three methods were found to be relevant and mathematical morphology provided the best results. Using this method, we further analyzed the impact of heterogeneous gels composition on the evolution of boluses properties. Results showed that when two gel layers of different composition were combined, the agar layer dominated bolus properties and that the presence of gelatin impacted the dynamics of gel breakdown. The results were in agreement with results obtained previously when characterizing the physical properties of the boluses. This study showed that artificial vision provides reliable tools for evaluating the dynamics of bolus formation, which is complementary to the methods commonly used in literature while avoiding extensive manipulation of boluses.

Breakdown pathways during oral processing of different breads: impact of crumb and crust structures

Oral processing during bread consumption is a key process related to the dynamics of texture perceptions, sensory stimuli release and starch digestion. The aim of this study was to determine the respective contribution of bread properties (composition and structure of crumb and crust) and of the oral physiology of subjects to the breakdown pathways in the mouth. The properties of the in vivo bread bolus obtained from eight healthy subjects were studied at three key points in time during their oral processing. The progressive lubrication and breakdown of bread were observed, as well as the beginning of the enzymatic degradation of starch. The study showed that "time" was the factor responsible for the greatest variability in bolus properties. Breakdown pathways were established for crumbs with and without crust. The presence of crust modified the oral processing, increasing, for instance, the heterogeneity of particle size at the middle of the oral processing sequence. Moreover, the hydration capacity of crust contributed to high starch degradation at swallowing time, in comparison with crumb alone. The main subject characteristics impacting bolus properties were the in-mouth duration, the individual masticatory index and the mouth volume, while the main bread properties explaining the bolus properties were the initial composition and the water-absorbing capacity. We concluded that both crumb and crust structures had an impact on the oral processing, affecting the capacity of hydration, the rheology and the breakdown degree of the bolus.

Uncoupling the Impact of Fracture Properties and Composition on Sensory Perception of Emulsion‐Filled Gels

AbstractThe aim of the study is to investigate the effect of fracture properties and composition of emulsion‐filled gels on dynamic texture perception. Twelve emulsion‐filled gels varying in fracture stress (High/Low) and strain (High/Low) were prepared from three binary gel mixtures. Mechanical properties, syneresis, friction properties, microstructure, melting behavior, oral breakdown and texture perception of the gels were determined. Gels varying in composition but exhibiting similar fracture properties were obtained. Serum release, melting in mouth and friction varied between gels differing in composition. Fracture properties and melting of gels impacted oral breakdown. Fracture properties impacted perception of texture attributes at first bite and during chew down. Melting and syneresis impacted chew down perception of gels. We conclude that fracture stress mainly impacted texture perception at first bite, whereas fracture strain impacted perception of chew down texture attributes with high fracture strain gels being perceived creamy. The composition of gels impacted properties such as melting and serum release, which accounted for high variations in perception of moistness and creaminess between samples.Practical ApplicationsFracture properties of food are known to impact the perception of first bite texture attributes. Moreover, they are known to control breakdown of food during oral processing. However, little is known about the impact of fracture properties on perception of chew down texture attributes. The current study highlights the impact of fracture properties on chew down texture perception. It identifies other gel properties depending on gels composition that account for variation in perception between gels. The use of emulsion‐filled gels enabled the investigation of sensory attributes related to fat perception. Such knowledge can be used for food reformulation, for instance formulation of low fat soft solid foods. This study indicates which mechanical properties should be controlled to obtain a desired texture profile of soft solid foods.

Effects of Agar Gel Strength and Fat on Oral Breakdown, Volatile Release, and Sensory Perception Using in Vivo and in Vitro Systems.

The density and composition of a food matrix affect the rates of oral breakdown and in-mouth flavor release as well as the overall sensory experience. Agar gels of increasing concentration (1.0, 1.7, 2.9, and 5% agarose) with and without added fat (0, 2, 5, and 10%) were spiked with seven aroma volatiles. Differences in oral processing and sensory perception were systematically measured by a trained panel using a discrete interval time intensity method. Volatile release was measured in vivo and in vitro by proton transfer reaction mass spectrometry. Greater oral processing was required as agar gel strength increased, and the intensity of flavor-related sensory attributes decreased. Volatile release was inversely related to gel strength, showing that physicochemical phenomena were the main mechanisms underlying the perceived sensory changes. Fat addition reduced the amount of oral processing and had differential effects on release, depending on the fat solubility or lipophilicity of the volatiles.

Oral Breakdown of Texturally Complex Gel‐Based Model Food

AbstractUntil now, the textural complexity of foods and subsequent influence on oral breakdown pathways has not been analyzed. This study evaluated the effect of textural complexity on the oral breakdown of foods by using gel‐based model foods with “built‐in” levels of textural complexity. Twenty subjects chewed and expectorated the model foods at different stages during mastication (chewing cycle). Textural complexity did not significantly impact oral transit time, number of chews or chewing rate. The high complexity (HC) model food followed a significantly different oral breakdown pathway to low complexity and medium complexity samples. During the initial stages of chewing, HC samples broke down into a significantly greater number (P &lt; 0.05) of significantly smaller particles (P &lt; 0.05). The surrounding matrices controlled the release of embedded inclusions, ensuring the HC samples followed a dynamic oral breakdown pathway with changes occurring in particle size and number throughout the whole chewing cycle.Practical ApplicationsThe textural complexity of food is associated with a range of differing texture attributes that from the first bite through to the point of swallowing stimulate the senses, creating a variety of texture perceptions. Little is known on how textural complexity can influence oral breakdown pathways. This study has shown how a high complexity model food follows a dynamic oral breakdown pathway where changes in the bolus occur throughout the whole chewing cycle. These results lend themselves to further study on how these constant changes influence perceivable texture and stimulate the senses during eating. It is also hypothesized by the authors that in foods that are more texturally complex, these perceived textures and potential stimulation might positively affect the satiation response.

Binding of Na+ ions to proteins: Effect on taste perception

This study investigated the relationship between the ionic binding of sodium and salty perception in protein matrices. Protein type (i.e. gelatin, milk protein and soy protein), protein concentration and pH were varied to obtain matrices with distinct compositions and rheological properties. 23Na NMR spectroscopy was used to determine the ratio of sodium ions bound to proteins and the mobility of sodium ions. The results showed that protein type, concentration and pH affected the rheological properties of the protein matrices, the ionic binding of sodium ions and taste intensity. As the protein concentration increased, the mobility of sodium ions decreased and the ratio of bound sodium ions increased. Gelatin matrices displayed the greatest mobility of total sodium ions and the smallest amount of bound sodium. Soy protein had a larger amount of bound sodium than milk protein. Lowering the pH of milk protein matrices tended to decrease the ratio of bound sodium and increase sodium mobility. We suggest that sodium ionic binding is related to the presence of negatively charged groups in proteins. Although changes in matrix composition modified sodium ionic interactions, taste perception was mainly affected by the rheological properties of the protein matrices. As the values of fracture stress or viscosity increased, firmness intensity increased and saltiness intensity decreased. The observed effects of texture on taste could be explained by cross-modal texture-taste interactions and by differences in the oral breakdown behavior of protein matrices.

Taste enhancement in food gels: Effect of fracture properties on oral breakdown, bolus formation and sweetness intensity

This study investigates the effects of fracture strain and fracture stress on oral breakdown, bolus formation and sweetness intensity of semi-solid food gels containing sucrose heterogeneously distributed in layers.The sweetness intensity of gels was mainly affected by the total surface area of gel fragments formed upon chewing. Gels with low values of fracture strain and fracture stress broke down into a large number of small fragments. These gels were perceived sweeter than gels with high values of fracture strain and fracture stress. Fracture strain had a larger impact on oral breakdown behavior and sweetness intensity than fracture stress. Results indicate that the oral breakdown behavior (i.e. formation of a large number of small fragments, which leads to an increase in the total surface area) is the driving factor for taste perception in semi-solid gels that have a heterogeneous distribution of sucrose.We suggest that the differences in sweetness intensity in gels containing sucrose heterogeneously distributed in layers and differing in fracture properties result from differences in the frequency of stimulation of taste receptors. An increase in the total surface area of fragments containing sucrose facilitates the release of tastants and increases the frequency of stimulation of taste receptors. Consequently, the taste intensity of gels is enhanced.