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Item Modelling of chewing and aroma release during oral processing : model development, model validation and comprehensive examples for food design : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemical and Bioprocess Engineering, Massey University, Palmerston North, New Zealand(Massey University, 2021) Mohd Firdaus How, Muhammad Syahmeer HowChewing is complex because of its sub-processes and interactions, and inter-individual differences between people. The development of mechanistic models can be a tool to explore these aspects and can lead to the development of foods with controlled digestion outcomes and improved sensory appeal. A mechanistic chewing model was developed based on selection and breakage processes and implemented using a discretised population balance to predict the changes in bolus particle size distribution during chewing. The model was successfully implemented on peanuts, which gave confidence for its implementation to cooked white rice, which is an aromatic food system and has strong correlations with in vitro digestion. The relationship between panellists physiological, chewing and aroma release parameters during mastication of white rice were investigated in vivo to provide insights for model development. The findings showed that the dynamic behaviour of aroma release of all five subjects followed a similar trend with the breakdown pathways where subjects with smaller particles size in their bolus had higher aroma release. The study paved the first step in understanding the role of chewing on aroma release of cooked white rice and provided a range of oral processing behaviours for model validation. A coupled chewing and aroma release model was developed and validated against experimental data. Adjusting the input parameters from the coupled model showed that the portion size, initial concentration of the studied aroma compound, initial liquid volume and the rice pasted fraction were the most sensitive product-related parameters. The oral cavity volume, pharynx volume, nasal cavity volume and the breathing frequency were the most sensitive physiological parameters. The physico-chemical parameter which had the most significant effect was the mass transfer coefficient in the saliva phase. Examples were also given to show the difference in aroma release when aroma compounds of varying partition coefficients were used. The work from this thesis constitutes the first step in the application of mechanistic chewing models as a tool for food design. The next step will be to expand these models to a wider range of food systems and to a larger number of individuals to improve the model reliability.Item Novel methods to characterise texture changes during food breakdown : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosphy in Food Technology at Massey University, New Zealand(Massey University, 2018) Ng, Cui Fang, GraceThe purpose of the mastication process is to break down food for bolus formation so that it can be swallowed safely. Although light has been shed on the criterion for a swallow safe bolus, quantifying these in terms of the bolus properties is not fully understood. There is a lack of suitable measurement techniques to quantify these identified bolus properties. Thus, the purpose of this work was to develop novel techniques that would be useful in in-vitro studies of food breakdown for the characterisation of bolus properties. A mastication robot (MR) had been previously developed to enable the reproducible mastication of food so that masticatory efficiency and food breakdown dynamics can be assessed quantitatively. To evaluate if the MR could be a controllable and reproducible alternative to subjects for food break down studies, a series of experiments involving the mastication of peanuts using a range of machine parameters was conducted. The bolus particle size distributions were used to characterise the breakdown of the peanuts. There were significant differences in the average particle size of the particles chewed by the different chewing trajectories during the initial chews. The performance of the mastication robot was validated against human subjects (n=5) by comparing the particle size distribution (PSD) of peanut boluses collected from subjects and the MR. Although the MR was unable to achieve similar breakdown capability as that for the human subjects, the MR proved to have good reproducibility in bolus preparation. Two novel techniques were developed to characterise bolus properties. The slip extrusion test was developed to characterise two determinant properties for safe swallowing, the bolus deformation and slippage properties. The test measures the force needed to extrude a bolus through a test bag imitating the swallowing action of a bolus. The multiple pin penetrometer was previously developed to measure the spatial distribution of texture in foods exhibiting heterogenous structures. The forces experienced by each pin is measured independently as they pushed through the food, providing a pressure distribution for each food. This allowed the characterisation of fibrous (non-fracturable) foods in a similar way to PSD analysis, offering a method to characterise boluses that do not form discrete particles. The variability in the structure of the boluses was also characterised using the grey level co-occurrence matrix through the image textural features: contrast, energy and homogeneity. Finally, these developed novel techniques were applied to five real foods with varying textures to show how the MR and these techniques may be used to characterise the changes in bolus properties across the mastication stages. Subjects (n=5) were asked to masticate the foods to determine their chewing behaviour and the bolus properties (deformation and slip properties) at swallow point. The chewing parameters from the median subject (subject A) was used to establish the parameters for the mastication robot’s set up for the factorial design of experiments. The developed models from the factorial study were used to optimize the conditions needed for the MR to achieve boluses with similar DR and SR properties as subject A. The five foods were then broken down using the MR configured in this way, and bolus properties were evaluated at various stages of the mastication process through the application of the slip extrusion test, textural mapping using the multiple pin penetrometer, and the back-extrusion test. Factor analysis was applied to the various data collected, which showed that the properties related to the hardness, swallowability and homogeneity attributes were best at describing the changes in the boluses as they were masticated to swallow point. In conclusion, the mastication robot could be used to replicate human chewing trajectories to consistently produce boluses in a controlled trajectory with controlled “simulated saliva” rates throughout the various stages of mastication. Thus, it is relevant as a tool to produce boluses for comparative analysis especially for studies investigating the properties of boluses collected from various stages of the mastication process. In addition, the developed characterisation techniques could be used to track the dynamic changes in the bolus properties for most of the mastication stages from initial chews to the swallow point and beyond that.Item The oral processing of semi-solid and soft-solid foods : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Albany, New Zealand(Massey University, 2014) Yao, HongyanFluid foods are popular in modern life. They are not only enjoyable to consume and provide nutrition, but are also beneficial to special populations, such as those with dysphagia and temporomandibular joint disease or who are edentate. Food rheological properties have an important influence on food oral processing and swallowing. Tongue movement plays a vital role during oral processing of liquid, semi-solid and soft-solid foods. The purpose of this research was to investigate the boundary criteria for categorising liquid, semi-solid and soft-solid foods; identify relationships between food properties and oral processing behaviours; and characterize tongue and lower jaw behaviours during food oral processing, in particular shear stresses generated between the tongue, lower jaw and hard palate. Constant weight samples were served to subjects who were instructed to consume them naturally, whilst movements of the tongue and lower jaw were measured via articulography and masseter and submental muscle activities were measured via electromyography. Food rheological properties (viscosity, flow curve, stretch-ability, storage modulus and loss modulus), pH and moisture content were characterized for each food sample. The oral residence time was found to be an important oral processing behaviour, which is affected by the original food viscosity, viscoelastic properties, moisture content, and stretch-ability. Tongue movements dominate the oral processing of semi-solid and softsolid foods instead of mastication which occurs for hard-solid food. The shear stress of the tongue and lower jaw is the main power during oral processing of semi-solid and soft-solid foods. The maximum shear stress of Greek yoghurt on tongue tip was 123 ± 31 Pa and 151 ± 59 Pa for two subjects; for custard, it was 144 ± 46 Pa and 192 ± 20 Pa. These results agree with estimated data which is currently available for the same food types. Overall, the shear stress tends to increase with increasing food viscosity. The method developed for measuring shear stresses applied in the oral cavity during oral processing was novel and is the closest to measuring real, in – mouth, shear stresses, which has not been possible to date.Item Relating sensory perception to chewing dynamics : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Auckland, New Zealand(Massey University, 2013) Cheong, Jean NeUnderstanding the mechanism behind the dynamic changes of food structure during oral processing is the key area for food texture studies. Food texture is a sensory perception derived from the structure of food, and oral processing plays an important role in this perception. This research aimed to establish a method to explore the relationships between oral processing and sensory perception, using biscuits of varying compositional and structural properties as a model food system. The initial study verified the capability of the Temporal Dominance of Sensations (TDS) technique to describe the textural aspects of a model food system whose structural properties change throughout oral processing. By standardizing the time-axis of the TDS curves from first bite to swallow, the technique was able to discriminate the textural properties of the samples of different sugar to fat ratios over the consumption period. The key differences of this type of standardization method were the attribute dominance rates and range in times to select the first dominant attribute. Moderate training of panellists on the definitions of the attributes showed performance improvement; clearer TDS curves (higher dominance rates) and reduced times to make the first dominant attribute selection (at least 10% faster). It was observed that subjects used a greater number of chewing cycles to process a food sample when they were also performing a sensory task such as TDS. The observation holds regardless of the level of training. When the TDS task was performed initially (the first sample), subjects need time to explore and learn the task hence slower chew frequency. This effect can be eliminated by introducing warm up samples before each session to ensure familiarity to samples and task. Overall, the samples were discriminated in their textural properties throughout chewing. The TDS technique appeared to be relevant to relate to the changing food properties in the mouth. The hardness levels of the sample marked an influence at the early stage of a chewing sequence, influencing the first dominant attributed selected and the oral processing. As food evolves during oral processing, other associated attributes become dominant in response to changing structural properties in the mouth. All samples undergo various structural changes in the mouth before reaching a definite state before swallowing. Two types of masticatory adaptations were present; adaptation to the task performed and adaptation to the altered textural properties in the mouth. The reproducibility of the TDS curves was also performed. This study demonstrated that for a food sample with five attributes to be evaluated in triplicate, at least 10 subjects were needed (i.e. 30 observations). This is true as the TDS technique is based on food evolution in the mouth. Further exploration of the TDS technique was performed using Discrete Point TDS. The technique offered new information that the typical TDS technique could not. The method was capable of differentiating the dominant attribute at each specific stage during mastication. This is not measurable with the conventional TDS technique and is less time consuming. In addition, intensity scores were found to complement the standard TDS data. The present study also showed the need to combine the TDS technique with masticatory recordings to investigate the dynamic mechanisms of the food behaviours throughout food oral processing. The simultaneous recording of the TDS technique, electromyography (EMG), and electromagnetic articulograph (EMA) confirmed that human masticatory apparatus adapted (chew frequency) to the altered textural properties caused by changing food sample composition and structure which also continued to evolve in the mouth. Evaluation of dynamic changes in sensory perception at various mastication stages helped in explaining the food evolution in the mouth and its responding oral processing strategies. The early chewing stage was dedicated to the fracture mechanism of the food where attributes such as hard and crunchy/crispy were most dominant. Mid chewing was dedicated to effort used to masticate food into a bolus which was suitable for swallowing; this included effort to reduce food particle sizes and incorporate saliva and the attributes crumbly and dry were most dominant. The end of chewing was dedicated to removing food materials from around the mouth for swallow, where sticky was most dominant. These associations supported the hypothesis that masticatory parameters are controlled by the sensory input and are linked to food properties, where a range of different food structure is responsible for the changes in the chewing strategies. Findings from this research demonstrated the strong correlation between the TDS profiles and chewing dynamics provided a new and improved technique for the food industry, in particular for designing foods with desired sensory properties. Moreover, the study confirmed that a complete understanding of texture can only be obtained through collaboration among different disciplines.Item Oral processing of dark and milk chocolate : a thesis presented in fulfilment of the requirements for the degree of Master of Technology in Food Technology, the Riddet Institute, Massey University, Palmerston North, New Zealand(Massey University, 2012) Gaikwad, VishThe thesis reports novel scientific understanding and findings generated on the subject of chocolate oral processing. Research was carried out with a view to unravel the role of food (chocolate) - and human-related factors in governing structural and physical transformation of chocolate matrices during human oral processing. Dark and milk chocolate were studied as contrasting model matrices to investigate the influence of composition and physical properties of chocolates on microstructure and physical properties of ready-to-swallow chocolate boluses formed as a consequence of distinct eating and saliva incorporation strategies. Microstructure, and physical/material properties, in particular, particle size distribution, hardness, mechanical and rheological properties of melts, and thermal behaviour and solid fat content (SFC) of the chocolate models were characterised and compared. Differences in particle size distribution between the chocolates, and presence of milk ingredients (milkfat, milk powder, lactose) and surface-active agents (soy lecithin) in the milk chocolate, as opposed to their absence in the dark chocolate, were recognised and discussed as prominent factors contributing to underlying differences in microstructure and physical properties between the chocolate models. The dark chocolate was significantly harder as compared to milk chocolate, and in addition demonstrated greater firmness, consistency, cohesiveness, index of viscosity, yield stress and plastic viscosity of melt. Analysis of melting behaviour suggested that in comparison to milk chocolate, the dark chocolate had a slower melting-rate and greater SFC, and hence demonstrated greater energy requirement for complete liquefaction. This was reflected through the thermal parameters of solid fat index, melting onset, end and peak maximum, and enthalpy of melting assessed using differential scanning calorimetry. A 24 subject human panel study undertaken to investigate eating (mastication and swallowing) strategies of consumers suggested that chocolate eating behaviour varied considerably across consumers. Findings highlighted that chocolate eaters adapted their overall eating strategies in response to differences in physical and related-textural properties of chocolates. In particular, total number of chews and oral processing time for the complete masticatory sequence and until the first perception to swallow, significantly differed between the two chocolates. These eating parameters were greater in the case of dark chocolate as compared to milk chocolate. Furthermore, subjects also conserved their general eating patterns and maintained similar masticatory frequencies between chocolates. Taken together, it was postulated that chocolate composition and physical properties, as well as human-related physiological and behavioural factors influenced dynamics of chocolate oral transformation, and were consequently involved in modulation of mastication and swallowing strategies. Hierarchical cluster analysis and analysis of variance were successfully implemented for segregation of population into three clusters with significant differences in eating parameters. This was followed by principal component analysis which facilitated the selection of 3 test subjects who exercised distinct overall chocolate eating strategies significantly different from each other, and moreover were from a related parent cluster. Regardless of eating strategy, occurrence of several voluntary swallowing events before complete oral clearance of chocolates indicated that only a part of the bolus was ready-to-swallow at the first perception to swallow. Observation of expectorates confirmed that at this point, chocolate boluses constituted a pool of liquid bolus phase (molten chocolate + saliva) as well as cohesive bolus lumps (solid/partially-melted chocolate particles aggregated together by the action of saliva and molten fat). While the liquid phase was swallowed by subjects, cohesive lumps underwent further oral processing to be transformed into a swallowable consistency. Microstructure analysis of bolus liquid phase by optical microscopy and confocal laser scanning microscopy revealed a coarse oil-in-water emulsion microstructure in the case of either chocolate wherein, a relatively denser bolus structure resulting from extensive ingredient and fat globule flocculation was witnessed for dark chocolate boluses. Results further suggested that solid fat content-related physical properties and melting behaviour were related to saliva incorporation. Greater hardness and energy requirements for liquefaction, and slower rate of melting in dark chocolate resulted in relatively longer oral processing time invested by subjects in bolus preparation. This in turn resulted in higher moisture content in ready-to-swallow boluses of dark chocolate (40.25 wt%) as compared to milk chocolate (32.20 wt%). Furthermore, these properties also resulted in cohesive-lumps of dark chocolate boluses being significantly firmer and requiring greater work for compression. In contrast, adhesiveness of milk chocolate boluses was greater in comparison with dark chocolate boluses, and was explained through the presence of milk ingredients in its chocolate matrix. Subjects processed both chocolates to similar cohesiveness of bolus lumps, interestingly indicating that this property may not be chocolate-dependent. Nevertheless, bolus saliva contents at the first point of swallow, and all mechanical properties accept adhesiveness of bolus lumps, were subject-dependent. Results indicated that this effect could be largely related to variation in physiological parameters, in particular oral processing time and salivary flow rates. Interestingly, liquid phase viscosities of milk chocolate boluses were similar to that of dark chocolate within-subjects, while this property was also subject-dependent. Adaptation of eating strategies and saliva incorporation demonstrated by subjects in response to differences in chocolate texture, and the presence of a relatively greater percentage of water-soluble solids in milk chocolate were factors which supported the fact that ready-to-swallow boluses of both chocolates had similar viscosities. Subject-dependency of chocolate bolus viscosity was explained through physiological parameters of eating behaviour and saliva flow rate which influence final moisture content in the bolus liquid phase. Considering the importance of the continuous fat-phase in influencing oral processing and bolus formation of chocolates, effect of storage temperature (0°C, 20°C, 30°C)-induced physical changes in dark and milk chocolate on physical properties of ready-to-swallow boluses, and eating and saliva incorporation strategies of selected subjects was investigated. Thermal analysis revealed mainly SFC-related changes in the physical properties of hardness and enthalpy of melting (ΔHmelt). Relative to 20°C, storage at 0°C resulted in increased hardness and ΔHmelt for both chocolates, while an inverse effect resulted from storage at 30°C. In the case of both chocolates, all subjects adapted their oral processing time, number of chews and saliva incorporation strategies in positive relation to increase/decrease in hardness and ΔHmelt. Again, they conserved their general eating patterns, and maintained similar masticatory frequencies to form boluses suitable for swallowing. In the case of both chocolates, significant softening and relatively greater reduction in ΔHmelt of chocolate stored at 30°C resulted in significantly low firmness and work of spreading of bolus lumps obtained at the point of swallow. Once again, in the case of all subjects, adhesiveness of bolus lumps was independent of these changes in physical properties for either chocolate-type. Lastly, results suggested storage treatments resulted in each subject processing a similar chocolate-type to different endpoints in terms of bolus liquid phase viscosity. Different SFC which governed the relative extent of melting that a chocolate underwent until the point of swallow, may have influenced the degree of bolus dilution, and hence its viscosity. Throughout this study, the excellent within-subject repeatability in eating strategies, saliva incorporation, and rheological properties of ready-to-swallow bolus for a particular chocolate- and/or texture-type was noteworthy.Item The particle size distribution of solid foods after human mastication : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Auckland, New Zealand(Massey University, 2012) Flynn, Christine SandraBolus formation is a complex process for which two theories are generally accepted, both theories describe how food changes through the mastication process which results in specific properties of the bolus being detected in the mouth to initiate swallowing. This research aimed to identify how food type, portion size (2 g and 4 g) and subjects affects the fate of ingested food solids and their particle size distributions, and bolus moisture content at the swallow point. Then the dynamics of bolus formation up to and past the point of natural swallowing were investigated by the use of a single subject to identify key trends. Trials involved up to five processed foods; subjects were asked to chew portions of food and expectorate the bolus at the point they felt ready to swallow, or to expectorate the bolus at a specific number of chewing cycles. The solids loss from the bolus and moisture content of the bolus was determined. Particle size distribution (PSD) was measured for the expectorated bolus, and the debris (solids rinsed from the mouth after the bolus). The food type had the greatest influence on the bolus moisture content, loss of solids from the bolus and PSD of the bolus and debris fractions. Solids are lost from the bolus progressively from the first chew cycle. PSD differed significantly between the bolus and debris fractions, and the PSDs were characteristic for each food type. The rate of change in PSD appears to plateau near the swallow point for some foods, whilst moisture addition continues to increase up to and past the point of swallowing. The bolus moisture content at the swallow point was approximately 50%, despite the differences in chewing strategy between subjects. Saliva does not appear to be added at a constant rate due to no significant effect of portion size. The results from these studies indicate that bolus does not have to meet specific particle size criteria to achieve a safe swallow, and that particles circulate in multiple compartments during mastication. Results suggest a defined moisture content is required for a safe swallow.Item Kinematics, motion control and force estimation of a chewing robot of 6RSS parallel mechanism : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering at Massey University, Palmerston North, New Zealand(Massey University, 2011) Torrance, Jonathan DavidParallel robots have been found in many applications where the work requirements are beyond the capabilities of serial robots. Mouth movements during the chewing of foods are ideally suited to the parallel robot due to relatively high force together with 6 degree of freedom (DOF) motion all occurring in a small workspace. The Massey Robotic Jaw (MRJ) is a life sized mastication robot of 6RSS parallel mechanism designed with human physiology in mind, and to be capable of recreating the movements and forces of human mastication. The MRJ consists of a movable mandible attached to a fixed 'skull' through 6RSS crank mechanisms enabling six degree of freedom motion. In order to perform targeted movements of the MRJ, inverse kinematics of mechanism are solved. Target movements of the lower jaw can then be translated to six individual movements of each actuator. The synchronised motion of all six actuators is implemented using appropriate motion control to create the desired motion at the lower jaw. Motion control in context of the MRJ involves position control during the non-occluding phases of the mastication cycle. The kinematic and dynamic models of a generic 6RSS robot are discussed and are then simplified considering the special features of a practical chewing robot and the requirements of controller design. The issue of dynamic position and force control of a chewing robot with a 6RSS mechanism is addressed. An impedance control scheme is proposed to achieve the position and force control of the robot. A detailed description on the steps to implement the controller is also presented. The application of the 6RSS parallel chewing robot to food chewing experiments was described. The force vector applied on the active molar was calculated from the measured torques applied on the six actuators using an analysis of forces through the linkage mechanism. A series of experiments were carried out using model and real foods. The work shows promise for application of the robot to characterise food texture, however a number of future developments are required. To make the robot more human-like, a tongue, cheek and mouth chamber need to be included. Furthermore, accurate force sensing and position sensing of the mandible in Cartesian space is suggested as a means to validate the impendence control method proposed and to verify the force measurement strategy implemented in chapter 6.Item Oral processing of heterogeneous foods : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Science at Massey University, New Zealand(Massey University, 2011) Hutchings, Scott Christopher; Hutchings, Scott ChristopherFood manufacturers could potentially benefit from foods designed to influence mastication and the breakdown of food into a bolus. Mastication and the properties of the food bolus have been linked to the sensory and nutritional properties of foods. This research aimed to investigate the mastication and particle size distribution of the food bolus of heterogeneous food systems, where one food component is combined with another, with a view to indentifying parameters that influence mastication and the food bolus. A range of matrices of contrasting physical properties, which were embedded with peanut pieces of contrasting physical properties, were investigated. Trials involved serving these heterogeneous foods to subjects standardized by volume (concluded as the most suitable serving method following an investigation of natural bite size). Subjects were asked to chew and expectorate the bolus (where the number of chews and chewing time were recorded) before the matrix of the expectorated bolus was washed away to isolate the peanut particles, and the peanut particle size distributions determined using image analysis. A Rosin-Rammler function was fitted to the cumulative distribution data of each bolus to derive peanut particle size parameters (d50 and broadness (b)). Results demonstrated that in heterogeneous food systems the presence of one food component (the matrices) can alter the breakdown of another food component (the peanuts) embedded inside that matrix. The properties of the matrix influenced mastication, the rate of peanut particle size reduction, and the spread of the distribution of peanut particle size inside the matrix, but did not influence the d50 of the peanut particle size distribution inside the bolus. Peanut properties did not influence mastication, but influenced the d50 of the peanut particle size distribution, the rate of particle size reduction, and the retention of peanuts in the bolus. It is postulated that the properties of the matrices largely influence the probability teeth contact peanut particles (known as the selection function), and the properties of the peanuts largely influence particle fracture per chew (known as the breakage function).Item Chewing behavior and bolus properties as affected by different rice types(World Academy of Science, Engineering and Technology, 2012) Moongngarm A; Bronlund JE; Grigg N; Sriwai N; Wong, ATC; Chin, KS; XU, MMThe study aimed to investigate the effect of rice types on chewing behaviours (chewing time, number of chews, and portion size) and bolus properties (bolus moisture content, solid loss, and particle size distribution (PSD)) in human subjects. Five cooked rice types including brown rice (BR), white rice (WR), parboiled white rice (PR), high amylose white rice (HR) and waxy white rice (WXR) were chewed by six subjects. The chewing behaviours were recorded and the food boluses were collected during mastication. Rice types were found to significantly influence all chewing parameters evaluated. The WXR and BR showed the most pronounced differences compared with other rice types. The initial moisture content of un-chewed WXR was lowest (43.39%) whereas those of other rice types were ranged from 66.86 to 70.33%. The bolus obtained from chewing the WXR contained lowest moisture content (56.43%) whilst its solid loss (22.03%) was not significant different from those of all rice types. In PSD evaluation using Mastersizer S, the diameter of particles measured was ranged between 4 to 3500μm. The particle size of food bolus from BR, HR, and WXR contained much finer particles than those of WR and PR.