DIVERSITY OF PERCEPTIONS OF MEAT TENDERNESS AND JUICINESS BY CONSUMERS: A TIME-INTENSITY STUDY

Seven judges, untrained in sensory assessment, were trained in the use of Time Intensity (TI) and asked to monitor the tenderness and juiciness of a range of cooked beef and pork samples. The subjects were given no definitions concerning sensory cues to monitor in their assessments, nor did they confer with each other. The shapes of the TI curves they recorded for tenderness and juiciness differed between individuals, although there were similarities in the curve shapes for the 2 attributes for each individual. Correlations between the intensity parameters of the curves (maximum intensity and area under curve) and the chewing time were not significant for the subjects as a group for tenderness, although significant correlations were found for some of the subjects when examined individually. The results indicate that subjects differ in their concepts of sensory tenderness and juiciness, and that perceived tenderness does not correlate with chewing time for all subjects. In more general terms the study supports the use of TI assessments for interpreting individual differences in sensory perceptions.     

METHOD TO INVESTIGATE DIFFERENCES IN CHEWING BEHAVIOUR IN HUMANS

This study examines whether the patterns of muscle activity measured from the masticatory muscles during a chew are sufficiently reproducible to form the basis of a characterisation of chewing behaviour, and whether they express the degree of variation evident between individuals. Electromyograph (EMG) readings of the repetitive activity involved in chewing gum were analyzed for 10 subjects, each on three separate occasions. For each individual the temporal aspects of the chew cycle (duration of the activity burst, period between bursts of activity and duration of the complete cycle) were reproducible between EMG recording sessions. Consistency was also found for amplitude aspects of the EMG record: mean voltage within the activity burst, maximum voltage, and the area under the EMG trace. For all six parameters there was significant variation between subjects. The study showed that variations in the chewing pattern, as occur for chewing on opposite sides of the mouth, were reflected in the 6 EMG parameters examined, and that the changes elicited were different for each individual. Moreover, encouraging subjects to concentrate on the act of chewing caused them to modify their chewing pattern, highlighting the importance of avoiding such attention when assessing habitual chewing behaviour.     

CHARACTERISATION OF PATTERNS OF CHEWING BEHAVIOUR IN HUMAN SUBJECTS AND THEIR INFLUENCE ON TEXTURE PERCEPTION

Electromyography was used as a noninvasive and unobtrusive technique to characterise chewing patterns for a range of foods. Differences between subjects for a variety of aspects of chewing sequence are recorded for a range of foods (carrot, apple, roast pork, salami, biscuit and toast). Identifiable subgroups of subjects differing in chewing behaviour existed within the random sample of 52 dentate subjects. The five subgroups accounted for 52%, 21%, 11%, 10% and 6% of the sample population. Major discriminating factors between the behavioural groups lie in their chewing time and the muscle work rate during chewing. Sensory ratings for firmness and rubberiness of model foods differed significantly between the subjects exhibiting different chewing behaviours. Chewing behaviour may influence consumers' perceptions about the texture of a food.     

WEAKENING STRONG BLACK POLITICAL EMPOWERMENT: IMPLICATIONS FROM ATLANTA'S 2009 MAYORAL ELECTION

Atlanta is perhaps the city with the greatest degree of black political empowerment (BPE) in the United States. Yet in 2009 a relatively weak white mayoral candidate nearly won the general and runoff elections over a field of stronger black candidates. Why? Treating Atlanta as a prototypical case, the article examines factors that undermine the capacity of blacks to retain control of mayoralties in strong BPE cities, with an emphasis on disruptions to black electorates, discontent among black citizens, and reinvestment in electoral politics by whites at the local level.     

Interference between independent processes

The first time independent, parallel processes consisting of two alternating renewal functions, say function zero and one, will be in phase zero together under equilibrium and non-equilibrium starting conditions is found. With function one an exponential distribution and function zero a non-lattice type, the distribution of the aforementioned time is found by taking advantage of a point of renewal. Further results are derived when both functions are exponential with the same parameter value by likening the situation to an Ehrenfest model

The results are applicable to many situations. Examples taken from machine interference, reliability with redundancy, queueing at parallel stations, ‘ channel ’ interference in computer systems and communications nets are included.     

Comparison of three‐dimensional analysis and stereological techniques for quantifying lithium‐ion battery electrode microstructures

Lithium‐ion battery performance is intrinsically linked to electrode microstructure. Quantitative measurement of key structural parameters of lithium‐ion battery electrode microstructures will enable optimization as well as motivate systematic numerical studies for the improvement of battery performance. With the rapid development of 3‐D imaging techniques, quantitative assessment of 3‐D microstructures from 2‐D image sections by stereological methods appears outmoded; however, in spite of the proliferation of tomographic imaging techniques, it remains significantly easier to obtain two‐dimensional (2‐D) data sets. In this study, stereological prediction and three‐dimensional (3‐D) analysis techniques for quantitative assessment of key geometric parameters for characterizing battery electrode microstructures are examined and compared. Lithium‐ion battery electrodes were imaged using synchrotron‐based X‐ray tomographic microscopy. For each electrode sample investigated, stereological analysis was performed on reconstructed 2‐D image sections generated from tomographic imaging, whereas direct 3‐D analysis was performed on reconstructed image volumes. The analysis showed that geometric parameter estimation using 2‐D image sections is bound to be associated with ambiguity and that volume‐based 3‐D characterization of nonconvex, irregular and interconnected particles can be used to more accurately quantify spatially‐dependent parameters, such as tortuosity and pore‐phase connectivity.     

Influence of Dynamic Calcination on Crystallite Growth of Submicron Rare-Earth Oxides

The crystallite growth of rare-earth oxide powders with particle sizes of 10 to 30 Å obtained by the hydrolytic decomposition of alkoxides was investigated. These powders were compared with commercially available powders with average particle sizes from 1000 Å to 10 μm. Static and dynamic atmosphere tests were made, the latter by continuous tumbling during calcination. Dynamic calcination controlled crystallite growth effectively while maintaining uniform particle size. Typical arithmetic mean particle sizes were 250 Å for powders calcined at 800°C for 24 h with tumbling and ∼400 Å for powders calcined under identical conditions without tumbling. TGA, X-ray diffraction, and emission spectrographic analyses were used to characterize the powders. Electron microscopy and BET surface area measurements demonstrated the importance of the dynamic calcination method in the growth of primary crystallites into larger particles during the presintering stage of the processing of these powders.