Mastication measurement

The rate of mastication, as measured by changes in plasticity or viscosity, is a complex function of temperature (Figure 11.16) with the rate going through a minimum at about 105°C. Below this temperature the increasing viscosity of the rubber causes increased shearing stresses at constant shearing rates and this... 

Figure 11.16. Efficiency of mastication of rubber at different temperatures. Molecular weights (M) measured after 30-minute mastication of 200 g natural rubber in a size B laboratory Banbury...

Whilst, chemically, SBS triblocks are similar to SBR, for example they do not show measurable breakdown on mastication, they are seriously deficient in one respect, they show a high level of creep. This would indicate that the concept of all the styrene blocks being embedded in the domains with all of the polybutadiene blocks being in the amorphous matrix is rather too simplistic. It has also resulted in these materials not being used extensively in traditional rubber applications. One exception from this is in footwear, where blends of SBS and polystyrene have been used with noted success for crepe soles. 

Fig. 16a-

The release of aroma compounds in the mouth during eating is primarily determined kinetically, rather than thermodynamically, because of the processes occurring when food is consumed. The model-mouth system was developed to study in vitro-like aroma release and considers the bolus volume, volume of the mouth, temperature, salivation, and mastication (van Ruth et al., 1994). Volatile compounds in the effluent of the model mouth are collected on porous polymers, such as Tenax TA. Alternatively, the effluent can be measured on-line by direct mass spectrometry techniques. The model mouth can be used to study the effects of food composition and structure on aroma release, as well as the influence of oral parameters related to eating behavior. 

A considerable problem for both the food industry and sensory scientists is the degree of individual variation in texture perceptions. The differences in breakdown pathways in the mouth for standard samples may underlie some of the variability. Indeed Brown et al31 have demonstrated an influence of chewing behaviour on texture perceptions in a model food system. Even if all individuals shared a common system for assessing a particular textural characteristic, the differences in the way they masticate a sample may cause them to come to different conclusions regarding its texture. However, there is also the real possibility that subjects may use different measuring systems for assessment of a textural characteristic they... 

We can determine what features of the chewing sequence influence assessment of particular textural characteristics of food by using this approach to examine the interaction between food and consumer during the mastication process. We should then be able to develop mathematical models for perception of textural qualities which take into account different texture combinations (for example, assessment of hardness in both elastic and brittle foods), and different breakdown patterns. Although currently at an early stage, mastication analysis shows promise for enhancing our measurement of perceived texture in foods. 

There would be considerable advantage for both sensory scientists and the food industry in knowing what consumers are measuring in order to assess particular textural properties. Despite many real advances in the instrumental measurement of food texture, we are not significantly closer to understanding the sensory cues used in consumer assessment of texture. The mastication process is adjusted to the consistency of the food bolus in real time. From studies of this process is emerging a novel approach to characterisation of food texture. 

The test foods studied here were five kinds of tomatoes. When eating food, humans first masticate the food with their teeth and then taste it. Therefore, we used a mixer in place of teeth and crushed tomatoes before measuring them. The preconditions were established by keeping the electrode immersed in standard juice, i.e., commercial canned tomato juice without NaCl added, for a long period of time. The origin of the output pattern was taken under these preconditions. Standard juice was used for the reference electrical potential pattern. The standard deviations between different lots of membrane were about 3mV. The same set of the eight membranes was used throughout the measurements for all tomatoes. 

When one considers the millions of non-fire-resistive substandard buildings in use today, it appears obvious that the field of opportuniyt is unlimited for marketing a good, reliable fire-retardant paint. A paint that would retard the ignition and spread of fire to a measurable degree would render many of these substandard buildings reasonably safe, and a paint or mastic that would increase the fire-resistance of an ordinary wood-studded, wood lath and plaster partition to 1-hour resistance, would find an immediate demand. 

Brabender Processing. In another series of tests, two commercial (stabilized) resins, unstabilized polypropylene, and the latter with 0.4% DLTDP + 0.1% PPP were masticated for five minutes at 50 r.p.m. and 180 °C. in the Brabender apparatus, then mixed for 25 minutes at 150 r.p.m. and 200°-215°C. Meter-gram torque readings were plotted over the mixing cycle along with temperature, and intrinsic viscosity was measured for each formulation before and after processing. 

Measurement of linear viscolelastic properties is a useful way of gaining information about a food s micro structure and how this influences the food s rheological character (Narine and Marangoni, 1999 Gunsekaran and Ak, 2002). However, many processing operations, and mastication, involve large, rapid deformations during which viscoelastic behavior is nonlinear. 

Lange JH, Thomulka KW. 2000b. An evaluation of personal airborne asbestos exposure measurements during abatement of dry wall and floor tile/mastic. Int J Environ Health Res 10 5-19. 

The effects of a hydrotalcite (magnesium/aluminium hydroxy carbonate) acid scavenger on the thermal stability of barium/zinc-stabilisedpoly(vittyl chloride) containing zinc pyrithione biocide in various proportions were investigated by heat stability, (fynamic thermal stabiUty and Brabender mastication experiments coupled with colour, anti-bacterial and anti-fungal measurements, and the results are discussed. 12 refs. 

Mooney viscosity is used to measure the extent of mastication. Mooney viscosity is the torque required to rotate the disk in the shearing disk viscometer. When the disk or rotor as it is called, is rotating without any load, the Mooney viscosity reading is zero . When a torque of 100 Nm is applied on the rotor the viscosity scale is read as 100. This is the scale in the Mooney viscometer (ASTM D1646 [2]). 

Thus, the Mooney units measure the extent of mastication or the plastic flow of rubber to enable better dispersion and mixing of ingredients and curatives. In addition to this, the Mooney units can give an indication of the curing nature of compounded uncured rubbers. 

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