JAW MOVEMENT DURING MASTICATION OF FIBROUS AND NONFIBROUS COMPOSITE FOODS BY ADULT SUBJECTS

A cinematographic study was made of subjects during mastication of fibrous and nonfibrous foods. The motion of the jaw was analysed mathematically. Each cycle of the vertical movement of the jaw could be considered as a combination of a sinusoidal motion, chewing phase, and a linear one, jaw opening phase. The lateral movement was not so well defined. On average, females took longer to chew foods and had smaller jaw movements than males. Fibrous foods took longer to chew and the amplitudes were larger than nonfibrous foods. The maximum rate of jaw movement during chewing ranged from 15 mm s⁻¹ to 30 mm s⁻¹, with males chewing at faster rates than females.     

Interrelations among physical characteristics,sensory perception and oral processing of protein-based soft-solid structures

Oral processing is essential in breaking down the physicochemical structure of the food and thus important to the sensory perception of food in the mouth. To have an understanding of protein-based, soft-solid texture perception, a multidisciplinary approach was applied that combined studies of food microstructure with mechanical properties, sensory evaluation, and oral physiology. Model foods were developed by combining ion-induced micro-phase separation and protein-polysaccharide phase separation and inversion. Activities of masseter, anterior temporalis and anterior digastric muscles during oral processing were recorded by electromyography (EMG), while jaw movement amplitudes, durations, and velocities were simultaneously collected by a three-dimensional jaw tracking system (JT-3D). Changes in the microstructure of mixed gels significantly altered the characteristics of the chewing sequence, including the muscle activities, number of chews, chewing duration and chewing frequency. Mechanical attributes related to structural breakdown and sensory perception of firmness were highly correlated with the amount of muscle activity required to transform the initial structure into a bolus ready for swallowing. Chewing frequency was linked to mechanical properties such as recoverable energy, fracture strain and water holding capacity of the gels. Increased adhesiveness and moisture release also resulted in slower chewing frequency. Evaluation of oral processing parameters at various stages (i.e., first cycle, first 5 cycles, and last 3 cycles) was found to be a useful method to investigate the dynamic nature of sensory perception at first bite, during chewing and after swallowing. The study showed that muscle activity and jaw movement can be used to understand the links between physical properties of foods and sensory texture.     

Technical note: Estimation of feed intake while grazing using a wireless system requiring no halter

A simple, compact bite counter was used to record dairy cow jaw movements. This information was used to estimate feed intake. The device is composed of a pendulum, a microcontroller, and a transmitter attached to a collar. The microcontroller memory can store the number of bites over 10-min intervals for up to 3 mo and has a battery life of more than 1 yr. The number of bites measured by personal observation, and the values reported by the counter were compared for 5 multiparous, nonlactating Holstein cows. The correlation was linear with an R² value of 0.9, unaffected by rumination, and little affected by walking. The collar system avoided the problems often experienced with counters attached to halters. The utility of the bite counter recordings in estimating intake was tested using 8 multiparous lactating cows. The slopes of the regression lines relating the number of bites to feed intake were dependent on the level of available pasture mass (120 or 190 g standing dry matter/m²). The feed intake could be estimated by applying linear regression to the number of bite counts versus pasture disappearance. In both cases the R² values of the regression lines were >0.7. Although the counter recorded jaw movements during grazing when the head was down, it did not record rumination or mastication when the head was raised because the counter/collar did not contact the jaw in this position. The bite counters were easy to attach to the cows using the collar and could be used effectively by farmers and researchers.     

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.     

The relationship between chewing activity and food bolus properties obtained from different meat textures

During chewing, a meat sample is mashed under compression and shear bite forces whilst saliva is incorporated. The resulting mixture is shaped into a cohesive bolus by agglomeration of small particles to trigger a swallow. This study aims to investigate the relationship between meat structure before chewing and texture after various chewing durations, according to the subject's chewing behavior. Twenty-five young adults participated. Electromyography activity (EMG) was recorded from surface electrodes on the elevator muscles during mastication of cold beef (5 g). Two different meat textures were obtained by varying aging and cooking temperature. Subjects were asked to chew and then to spit out the bolus either after a constant chewing duration (7 s) or when the bolus was ready to be swallowed. Boluses were then weighed to determine saliva incorporation. Cutting tests were applied to measure maximum shear force and to assess bolus structure homogeneity. From EMG recordings, temporal and amplitude parameters were analyzed. The mechanical shear force was maximal for meat before chewing and decreased for the bolus with the lengthening of the chewing duration. Significant texture differences were found for samples before chewing and for two types of bolus but differences were larger for the bolus after 7 s chewing than for the bolus when ready to be swallowed. The amount of saliva incorporated into the bolus increased with both chewing muscular activity and chewing duration. Finally, the more chewing cycles before swallowing, the more comminuted the meat bolus (lower shear force) and the more saliva was incorporated in it. These results fit with one of the major roles of the saliva, that is, to provide cohesion between particles [Nature 391 (1998) 329] and with the intra-oral management of meat during chewing as analyzed by videofluorography [Arch. Oral Biol. 47 (2002) 267].     

Dynamics of food breakdown during eating in relation to perceptions of texture and preference: a study on biscuits

Combined recording of masticatory muscle activity and jaw movement patterns during eating was used to examine the process of food breakdown in the mouth for a series of “Rich Tea”-type biscuits in 19 ordinary consumers. These data indicated an initial increase in chewing work from the masticatory muscles over the first 5–10 chews followed by a decline over the remainder of the chewing sequence. The work was concentrated in vertical closing of the jaw during the early chews but as this declined over the later chews there was an increase in the amount of work occurring with the teeth in near occlusion. The relative amount of work input into the chewing sequence, the duration of the sequence, and the degree of work undertaken at occlusion, differed among groups of the consumers who were classified according to their chewing efficiency (CE). Subjects from different CE groups appeared to have different understandings of the textural characteristics of the samples which they assessed as “hardness”, “crunchiness” and “crumbliness”. Differences in the oral breakdown patterns for different CE groups may provide an understanding of differences in consumer preferences for the samples. ©     

Technical note--a comparison of methods used to measure eating and ruminating activity in confined dairy cattle

Detailed knowledge of chewing and rumination activities is critical to fully understand the dietary factors affecting normal rumen function. An automatic system for the digital recording of the jaw movements in free-ranging grazing cattle has been described, but its ability to measure chewing activity of cattle housed in confinement and fed total mixed rations has not yet been evaluated. The eating and ruminating behaviors of eight lactating dairy cows were recorded simultaneously by a wireless automatic system and by 5-min interval observation over 24-h periods. Results indicated that both methods agreed on identification of eating and ruminating bouts. Mean differences between methods for total time eating (8.7 min +/- 12.8) and ruminating (42.9 min +/- 12.0) were significantly different. The time recorded by observation in both eating and rumination was 3.6 and 10.3% higher compared with the automatic system. Differences indicate inaccuracies in the observational method itself. The automatic system may prove useful in further studies examining eating and rumination activities in cattle.     

Technical note: A noninvasive urine collection device for female cattle: Modification of the urine cup collection method

Total urine collection from female cattle requires the use of indwelling urinary catheters or an external device requiring secure attachment with adhesive to the animal; neither method is ideal for the welfare of the cattle. A urine collection device was developed to enable total urine collection in female dairy cattle without the use of adhesive to attach the device to the vulva of the animal; the device was a modification of one described previously for female cattle. The urine collection device was made from polypropylene with maximum dimensions (height × width × depth) of 17.5 × 11.0 × 6.0 cm and an opening of approximately 42 cm² to cover the vulva. The device was secured using a commercially available udder support harness that provided snap-fasteners and support for the device to be positioned at the level of the vulva. At the point of attachment, a metal brace surrounded the device and was connected to the udder support by metal rings, which kept the urine cup in proper position as the animal arched to urinate. A metal O-clamp and pieces of rubber, serving as leak-proof washers, connected the bottom of the device to Gooch tubing. Another metal clamp was attached to a polyvinyl chloride adapter that was connected to a rubber hose, and urine was collected into carboys located on the floor approximately 1.5 m behind the animals. This modification of a urine cup allows several noninvasive total feces and urine collection studies of unrestricted length to be undertaken without the use of adhesive to attach the device. The floor-level collection system is a practical, portable, and handy system that will permit researchers to perform nutrient balance and metabolic studies on female cattle.     

口腔加工过程中传统干腌肉咸味释放规律

招募50 名食品专业在校学生,筛选、培训10 人组成感官评定小组,10 名感官评定员在自由咀嚼状态下咀嚼干腌肉样品并在不同咀嚼阶段收集食团及唾液。通过测定咀嚼过程中食团的水分含量、pH值、NaCl含量和唾液pH值、电导率以及使用电子舌检测分析其味觉特征,研究口腔加工过程中传统干腌肉的咸味释放规律。结果表明：咀嚼过程中食团的水分含量显著增加,NaCl含量持续降低,pH值无显著变化;从咀嚼开始到咀嚼终点唾液分泌量显著上升,唾液电导率持续升高;由电子舌检测分析可知,干腌肉咀嚼过程中,咸味的释放规律为先上升后下降趋势,且在30%咀嚼阶段咸味释放达到最高值。     

Association between chewing efficiency and mastication patterns for meat, and influence on tenderness perception

The aim of this study was to investigate whether individuals' chewing patterns were related to their chewing efficiency, and influenced their perceptions of meat tenderness. Chewing efficiency was measured using two methods. Subjects continuously assessed the tenderness of a range of samples throughout the chewing sequence using Time Intensity. At the same time electromyographs (EMGs) were recorded from their masticatory muscles.

Subjects were subdivided into four groups with respect to their chewing efficiencies with the two methods. These subgroups differed significantly in the number of chews, total chewing time and chew work, both for the initial chews and the complete chewing sequence, for the meat samples. No significant difference was found in the dentition between the groups. Significant differences were found between the groups in their temporal perceptions of tenderness.     

帘子布浸胶处理速度比微机监测系统的研制

在帘子布生产过程中,为了实现对速度比的动态监测,研制开发了帘子布浸胶处理速度比微机监测系统。系统的硬件组成包括脉冲检测与整形电路、逻辑控制电路、ＳＴＤ工业控制机、速度比上下限设定电路、计数器及其控制电路、模拟脉冲发生电路;软件采用ＭＣＳ－５１汇编语言编程,包括主程序和中断服务程序。实践证明,该系统对纺织行业的诸如上浆过程的速度比监测有较好的借鉴意义。     

Effects of supplemental hay and corn silage versus full-time grazing on ruminal pH and chewing activity of dairy cows

Grazing young, highly digestible swards with and without supplemental hay or corn silage (5.5 kg of DM/d) offered overnight was tested for its effects on ruminal pH and chewing activity. A double 3 x 3 Latin square arrangement with 6 rumen-cannulated Brown Swiss cows (29 kg/d of milk) was applied. Herbage intake was quantified by controlled-release alkane capsules. Chewing activity was determined using an automatic microcomputer-based system for digital recording of the jaw movements. Except during milking, ruminal pH was measured continuously over 7 d by applying a device consisting of an indwelling pH electrode and a data-recording unit integrated in the cannula's cover. The grazing system had no significant effect on body weight, milk yield or composition (except milk urea), or total DM intake (13.5, 13.8, and 15.7 kg/d with full-time grazing, hay, and corn silage supplementation). No differences occurred for ruminating time per day and time per kilogram of DM intake. Full-time grazing cows spent more time eating per day (+26%) and time per kilogram of DM intake (+31%) than the other cows. Ruminal pH and time with pH <5.8 at night did not differ. Throughout the day, hay-supplemented cows had a significantly lower pH (-0.23) than full-time grazing cows, and the period of pH <5.8 was longer compared with corn-silage fed cows (77 vs. 11 min). Nocturnal supplement feeding gave no advantage over full-time grazing, and supplemental hay led to lower daytime pH.     

Impact of texture TDS and flavour TDS tasks and of chocolate-chip biscuit characteristics on oral processing features

The objective of the present study was to investigate differences in oral activity when biscuits of the same type but with subtle composition differences are consumed and how performing a Temporal Dominance of Sensations (TDS) task modifies the way one eats. In addition, comparisons were made between performing a texture TDS (T-TDS) and a flavour TDS (F-TDS). Oral activity while eating biscuits with and without conducting a TDS task was recorded using a 3.dimensional motion capture system to monitor the evolution of jaw movements.The results showed that oral activity evolved over the consumption time, differed depending on the texture of the sample and was affected to a small but significant extent when a TDS task was performed simultaneously (the differences averaged <4 cycles, 1 s in duration, 0.1 cycles/s in frequency, and 1 mm in lateral displacement). The biscuit samples were affected equally. Almost no differences were found on comparing oral activity during the execution of the T-TDS and the F-TDS tasks.Overall, the present results show differences in oral activity even for food products of the same category with subtle differences in composition. Performing TDS tasks (regardless of their modality) during sample consumption affected the total number, frequency and lateral amplitude of the chewing movements which should be taken into account for future research. However, these differences were small and affected both samples equally.     

Relations among mechanical properties, human bite parameters, and ease of chewing of solid foods with various textures

This study clarified relations among human bite parameters, mechanical properties, and sensory-determined ease of chewing for 11 solid foods having various textures. A multiple-point sheet sensor measured the human bite force, pressure, and impulse between molars during the first chew. Foods were categorized into four classes based on the shapes and magnitudes of human bite force–time curves. The bite parameters and mechanical parameters shared, in most cases, a non-linear relation, for which a power law model was usually representative. Bite parameters were compared with results of compression and puncture tests obtained using a universal testing machine. The highest correlation was found between the logarithm of the maximum bite force and the logarithm of the puncture force (R = 0.916). Sensory evaluation revealed the optimum correlation between the impulse during the first bite and ease of chewing (R = −0.872). Ease of chewing was assessed during the first bite rather than at the maximum force point because the bite impulse showed a higher correlation than the maximum bite force and pressure. The prediction of ease of chewing was acceptable for use with the work in compression tests (R = −0.689).     

ELECTROMYOGRAPHIC STUDY OF MASTICATION OF KELP SNACK

Electromyograms (EMGs) of mastication of kelp snack were compared with the physical properties measured by a tensile test and sensory assessment. The number of chewing strokes, masticatory time, total muscle activities and total duration for whole mastication agreed with the breaking force in the tensile test and with sensory difficulty of mastication. Amplitude, EMG activity, and duration per chew also showed the same tendency. In the masticatory cycle, significant differences among the samples were not observed. As mastication proceeded, the amplitude and EMG activity decreased, and the EMG-duration shortened. The EMG activity, amplitude, and masticatory rhythm changed significantly, and sample differences decreased from the middle to the late stage of mastication. Just before swallowing, the chewing cycle was lengthened, and no significant difference was observed among samples at the last chew.     

RHYTHMIC AND IRREGULAR MOVEMENT OF THE FIRST MOLAR WHILE EATING FOODS WITH DIFFERENT TEXTURES

The three-dimensional movement of a tooth, any tooth, while naturally eating, was measured by an apparatus developed in our laboratory. The movement of the first molar on the usually used side is reported here. The mastication movements are divided into two parts, namely the rhythmical chewing period during which there are mastication pressure loads on the molar and the irregularly pulsated moving period in preparation for the swallowing followed by the rhythmical one during which there is no more pressure on it. The amplitudes of the up and down movements of the molar are 10–22mm for the rhythmical chewing period which are bigger than those for the irregularly moving period. The rhythmical chewing periods are distributed around 10–40 s depending on 14 kinds of food texture, and also on the size of the food, in a fairly similar manner for the participants. The period is longer for tough foods and bigger samples. The irregularly pulsated moving periods are widely distributed, 2–45s, and depend both on the food texture and on the participant. The irregular moving periods are longer for foods which scatter in the mouth or adhere to the teeth when chewing. The ingestion difficulty of the food was divided into two groups. One is where it is difficult to break down the food with the teeth and the other is where it is difficult to prepare for swallowing.     

FREQUENCY SPECTROGRAPHIC ANALYSIS OF BONE CONDUCTED CHEWING SOUNDS IN PERSONS WITH NATURAL AND ARTIFICIAL DENTITIONS*

Bone conducted chewing sounds picked up by a specially designed device were recorded from three different facial bony locations in two age and sex matched groups of subjects with natural and artificial dentitions. Frequency spectrographic analysis revealed that, although the sounds were louder in subjects with natural dentition, crisp and soggy textures could be equally well differentiated by their noise levels in both groups. The use of a denture adhesive restored the chewing noise of denture wearers to that observed in the natural dentition group. There was a marked degree of mechanical impedance in the transmission of sound from the site of masticatory impact to distant cranial points. Breakdown of particle size during chewing was accompanied by declines in noise levels.