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    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, Grace
    The 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.
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    Resolving problems affecting the processing of dried marrowfat peas for fried foods : hard-seededness and cooking temperature and time : a thesis submitted in partial fulfilment of the requirements for the degree of Masters of Food Technology, Massey University, Palmerston North, New Zealand
    (Massey University, 2017) Ayaquil, Froilan T.
    The Midland Seed Ltd, a top agricultural seed producer in New Zealand, wishes to increase their level of technical knowledge regarding the processing of peas to assist with solving production problems. In this study, analyses were conducted to resolve if hard-seeded peas or the frying parameters caused the textural irregularities in fried marrowfat peas. Marrowfat peas (pisum sativum cv. Midichi and Midlea) from 16 different harvest locations and years (2014 to 2017) were subjected to tests such as hydration capacity, and sizing of peas were examined to ascertain how much hard-seeded peas were surfacing in a line batch and in different sizes (<6.7mm, 6.7-7.1 mm, 7.1 – 8.0 mm, and > 8.0mm) upon soaking (in different soaking times 12, 18 and 24 hours) and frying at 160°C for 12 minutes. Furthermore, frying conditions including, oil temperature, pea to oil ratio, were explored at a laboratory scale to obtain the most suitable frying parameters capable of producing fried marrowfat peas with consistent and highly acceptable organoleptic properties. It can be concluded from this study that the very low frequency of hard seeds found in marrowfat peas was not the cause of texture inconsistency generally. However, it was shown that cooling the oil to below 130°C, when peas were added to the oil, slowed temperature recovery of the oil and significantly increased pea hardness to unacceptable levels. Marrowfat peas fried at 160°C for 12 minutes, with a pea to oil ratio of between 1/20 and 1/40 resulted in peas consistently fried to a highly acceptable quality.
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    Evaluation of Massey twist tester for textural assessment of fruits and vegetables : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Agricultural Engineering at Massey University
    (Massey University, 2000) Tautakitaki, Tevita Pasinamu
    The Massey Twist Tester is an instrument developed to assess the texture of fresh fruit and vegetables rapidly. Since its original development in 1990, the Twist Tester has been modified extensively and numerous prototypes have been developed. In principle a small rectangular flat blade is rotated inside the fruit, and the torque required is measured. The current version incorporates a motor driven unit rotating inside a set of needles which hold the fruit firmly. Although measurements of fruit properties have been reported in previous studies, these have all been based on earlier designs, and no data on the new version of the Twist Tester have yet been published. The main aim of this study is to evaluate the performance of the new version of the Twist Tester by comparing it to the standard penetrometer, which has been widely used in many parts of the world for several years. Samples of fruit and vegetables were stored in different conditions to vary the level of firmness in order to expose how well each instrument performed in detecting the changes of textural properties. Generally, both Twist Tester and Penetrometer readings declined with storage time. In the testing of Braeburn apples, the Twist Tester has highly correlated with storage time as compared to penetrometer, The Twist Tester and Texture Analyser produced results for the Royal Gala apples which were highly correlated with those obtained from the penetrometer, suggesting that this test could be used, as it is more reliable for determining the maturity of apples. For plums, the correlation of the Twister with storage time at three storage conditions were high (r =0.92, 0.95 and 0.92), compared to the correlated of penetrometer with storage time which was (r = 0.83, 0.44 and 0.77). The penetrometer has a slightly higher degree of correlation with storage time for pears, compared to the Twist Tester. Pears declined in crushing strength and penetrometer readings with storage time, but over the last 7 days the value of firmness increased. The literature review showed that when water loss from the fruit is extreme, it forms a rubbery texture, produces a higher degree of firmness. Further research work would need to be done to obtain a more reliable result. The Twist Tester performed well in predicting the changes of textural properties of nashi, which showed a stronger correlation with storage time than the penetrometer relationship with storage time. During storage of kiwifruit, the penetrometer could not detect any changes after 14 days, while Twist Tester obtained a reliable result. This showed that penetrometer could not test the firmness of texture of any soft fruits. The relationship between the crushing strength and storage time produced a high coefficient in all three storage conditions (r = 0.91, 0.89, 0.80) while the penetrometer readings showed the following correlations with storage time (r =0.77, 0.76, 0.44). Thus the Twist Tester can determine the maturity of kiwifruit as well as any soft tissue products. Changes in the textural properties of potatoes also were well detected by the Twist Tester, which showed a stronger correlation with storage time than did the penetrometer. Firmness and crispness as measured by both the Twist Tester and penetrometer readings were highly correlated, while other variables showed only a poor relationship with instrumental measurement. Further research is needed to improve these results by using a well-trained taste panel. Changing the speed of Twist Test has no significant effects on the crushing strength of fruit and vegetables within the range of 5-10 rpm. The Twist Tester is more accurate, easy to operate and may be used to determine the quality and maturity of a wider range of products than penetrometer.
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    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, Hongyan
    Fluid 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.
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    Design and development of a food texture analyser : a thesis presented in partial fulfillment of the requirements for the degree of Master of Engineering in Mechatronics at Massey University, Manawatu, New Zealand
    (Massey University, 2015) Shi, Weizhong
    Texture is an important attribute of food and is one of the several dimensions of food quality. In today’s world of sensing and automated measurements, it is becoming increasingly common to analyse food by using a texture analyser. A variety of texture analysers is in use by researchers and industry for the purpose of quality assurance and improvements. This thesis is on the design, development and implementation of a food texture analyser with a focus on enhancing response time, increasing measurement flexibility, and reducing equipment cost. Several enhancements have been done to an existing texture analyser. A high-end 24-bits ADC (Analogue to Digital Convertor) has been used to measure the output of a load cell very accurately. The output of the ADC is coupled to a modern microcontroller using the industry standard SPI bus. A touch screen has been incorporated to provide an easy user interface. A completely new motor controller/driver has been employed for the movement of the robotic arm and an infra-red sensor has been used to detect its position. A unique and novel contribution is in the form of a new command-language that has been developed which makes it extremely flexible for the user to control the motor movements. An enhancement, not found in existing commercial texture analysers, is the real-time graphing of measurement data which is displayed on the PC. Additionally all the data can be saved to a text file or a CSV file for subsequent retrieval and processing. The complete system has been realised and tested. Several different fruits were used for experiments and the measurement data compared with a commercial texture analyser. The system is simple to use, versatile and low cost for use in research and industry.
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    Physiological measures related to crispness perception of extruded snacks : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Albany, New Zealand
    (Massey University, 2003) Duizer, Lisa Marjorie
    Published research for understanding crispness perception has relied on correlations of sensory results to objective measurements. This research was undertaken to evaluate the contribution of physiological responses to the perception of crispness of corn based puffed snacks. Predictive models published in literature relate crispness perception to instrumental force and sounds produced during biting and compression. These models were used as the basis for this research. Air-conducted and bone-conducted sounds were measured using both consumer and trained panelists. A novel analysis technique, fractal analysis, was used to analyse the jagged sound wave patterns produced during biting into extruded snacks. A specialised bite force apparatus was designed for measuring bite forces produced by the incisors. All physiological results were then related to panelists' perception of crispness. To minimise sample variability, extruded snack samples were prepared and used throughout the entire trial. A range of crispness levels were achieved by equilibrating the extrudates over various water activities. Consumer panelists and trained panelists consistently agreed on the relative crispness of the extruded snacks. Air-conducted sounds and bite force showed significant correlations with crispness, while bone-conducted sounds did not. Bite force measures were also shown to relate to instrumental measures of force. For statistical validity, the physiological data from the 39 consumers were used to develop predictive equations for crispness. Analysis of the data showed no significant correlation between the physiological data and crispness. Therefore, it was not possible to develop a predictive equation for crispness based on the physiological measures collected from consumers. While there are reports linking crispness to various instrumental measures, this is the first time in-vivo physiological measures have been collected from a large group of individuals for development of statistically viable models for crispness. The lack of a relationship between crispness and physiological measures indicates that crispness perception across consumers is complex and not adequately explained by bite force and sounds alone.