Impact of salivary flow inhibition on masticatory behaviours in healthy individuals.

BACKGROUND: It remains unclear how the salivary flow and the fat content of food affect bolus formation during mastication. OBJECTIVES: We aimed to clarify: (1) how hyposalivation affects jaw-closing and hyoid-elevating muscle activities in bolus formation, and (2) if the effect of hyposalivation on muscle activity depends on the fat content of food. METHODS: Eighteen healthy male volunteers were instructed to freely ingest four test foods: Plain, Fat without seasoning, Fat with seasoning, and Soft rice crackers. Masseter and suprahyoid electromyographic activities were recorded before and 30 min after the administration of atropine sulfate, a muscarinic receptor antagonist that induces hyposalivation. RESULTS: Hyposalivation extended the masticatory duration significantly in all the test foods except Fat with seasoning. Masticatory cycle time was significantly longer with vs without hyposalivation for the Soft (p = .011). Suprahyoid activity/cycle was significantly greater with vs without hyposalivation (p = .013). Masticatory cycle time was significantly longer at the late stage with vs without hyposalivation for the Soft (p < .001). Suprahyoid activity/cycle was significantly greater at the middle (p = .045) and late stages (p = .002) with vs without hyposalivation for the Soft and greater at the late stage with vs without hyposalivation for the Plain (p = .043). Changes in masticatory cycle time and suprahyoid activity/cycle for these foods had significantly positive relationship (p < .001). CONCLUSION: Hyposalivation-induced changes in masticatory behaviours resulted from the middle and late stage suprahyoid activity. Fat content and seasoning compensate for salivary flow inhibition.

Crispness, the Key for the Palatability of "Kakinotane": A Sensory Study with Onomatopoeic Words.

Crispness is among the most important food textures that contribute significantly to palatability. This study investigated the association between the perceived crispness and palatability of five types of Japanese rice crackers known as "kakinotane." Two experiments were conducted using the temporal dominance of sensations (TDS) and temporal drivers of liking (TDL) methods. As descriptors for the TDS evaluation, we used 10 Japanese onomatopoeias to indicate various attributes of crispness. We also measured the mastication sounds and electromyography (EMG) activity during mastication. Principal component analysis data revealed that principal component 1, representing moisture characteristics, contributed more than 60% in both experiments. The palatability of the stimulus, which was described as having a very soft, moist, and sticky texture, BETA-BETA, was significantly lower than the others. However, there was no significant relationship between the amplitude of mastication sound or EMG activity and palatability. We demonstrated that naïve university students can discriminate the fine nuances of the crispness of "kakinotane" using the TDS and TDL methods. Our findings also suggested that the onomatopoeias used as descriptors in the TDS method had a greater influence on describing the nuances of food texture than the physiological data.

Age-related changes in functional adaptation to bolus characteristics during chewing.

We investigated how the physical properties of food affect chewing kinematics, and examined the effects of aging on behavior. Twenty young and 21 older volunteers were asked to freely chew rice crackers and spit the food out at their average chewing duration. We compared chewing characteristics among the conditions (age × rice cracker), and examined the area of rectified masseter and suprahyoid electromyographic bursts per chewing cycle. We also evaluated temporal changes in those values. In addition, the bolus properties at the end of chewing were compared. The harder/larger the rice cracker, the longer the chewing duration and the greater the number of chewing cycles. These values also increased with age. Chewing cycle time was not affected by age and rice cracker properties, except in one condition: for the rice cracker with the lowest hardness and density, the chewing cycle time was longer than for the other rice crackers. Chewing cycle time decreased at the middle stage of chewing, followed by an increase, with increasing suprahyoid electromyographic activity at the late stage. The physical properties of the bolus at the end of chewing did not differ between age groups, and depended on the initial properties. The water absorption rate of the bolus was significantly greater for the rice cracker with the lowest hardness and density compared with other rice crackers. The results demonstrated that not only hardness, but also other factors, such as density, significantly affected chewing behaviors.

Effects of rheological properties of rice dough during manufacture of rice cracker on the quality of the end product.

Influence of the viscoelastic properties of rice dough on the mechanical properties and the microstructure of rice crackers was experimentally investigated to predict and control the quality of the rice cracker in the early stage of the lengthy manufacturing process. Various rice doughs steamed for 5, 30, or 60 min and kneaded for 5, 10, or 15 min were examined. Longer steaming and kneading resulted in lower G' and G″ and higher tan δ, specific volume of the rice crackers, decreased nonuniform and deficient network, and thinner cell wall in rice cracker sections. There was a high correlation between tan δ of rice dough and specific volume of the rice cracker samples (R2 > 0.79). The hardness of the rice crackers increased with extending the kneading time for 5 and 30 min as the tan δ increased, while those of the rice crackers made from the rice doughs steamed for 60 min decreased inversely. These results indicated that qualities of rice crackers can be predicted and quantified by measuring viscoelasticity of actual rice doughs during the process. PRACTICAL APPLICATIONS: Improved methods to control quality of end product in manufacturing process and to develop new products with unique textures are desired. We established the new method to quantify the rice dough and this method has already been used for confirming equivalency or improvement of rice dough during manufacture of rice crackers when instrument or condition have changed.

New potato micro-tuber-inducing cyclohexene compounds related to theobroxide from Lasiodiplodia theobromae.

Two new cyclohexene compounds related to theobroxide (3) were isolated from the mycelia of Lasiodiplodia theobromae OCS71. The structures of these compounds were determined to be (4S,5S)-4,5-dihydroxy-2-methyl-cyclohex-2-enone (1) and (3aS,4R,5S,7aR)-4,5-dihydroxy-7-methyl-3a,4,5,7a-tetrahydrobenzo[1,3]dioxol-2-one (2) by means of spectroscopic analyses and chemical correlation to 3. Compound 2 was shown to take up the carbonate ion to form a carbonic acid ester non-enzymatically. The compounds also showed potato micro-tuber-inducing activities at a concentration of 10(-3) M, using a culture of single-node segments of potato stems in vitro.

Voltage-gated channel properties of epithelial cells in porcine vomeronasal organ.

Bipolar vomeronasal sensory neurons (VSNs) in the vomeronasal organ (VNO) are believed to detect pheromones in most mammals. The vomeronasal sensory epithelium (VSE) is composed of VSNs and supporting cells. There are morphological differences in VNOs between species. Many electrophysiological experiments have been performed on rodent VSEs but few on other mammals. We therefore investigated voltage-gated channel properties of cells in the porcine VSE using slice whole-cell voltage-clamp techniques. In immunohistochemical study of the porcine VSE, most PGP9.5-immunoreactive cells were found between the middle and basal region, and negative cells were distributed in the apical to middle region. Depolarizing pulses to epithelial cells from -90mV produced transient inward Na+ channel currents and sustained outward K+ channel currents with various amplitudes. The distribution of cells having high and low Na+ current densities was mostly consistent with the histological distribution of VSNs and supporting cells, respectively. The half-inactivation voltage of voltage-gated Na+ channels in supporting cells was 26mV more negative than that in VSNs. Voltage-gated K+ channel currents in both cell types were suppressed by tetraethylammonium to the same extent. VSNs possessed TTX-sensitive voltage-gated Na+ channels and Ni2+ -sensitive T-type Ca2+ channels. These results suggest that the histological distribution of porcine vomeronasal epithelial cells is more similar to the dog and goat than to rodents, and that the electrophysiological characteristics of porcine vomeronasal epithelial cells are similar to those of rodents. It is also suggested that porcine VSNs detecting pheromones generate action potentials through these channels.

Biosynthesis of theobroxide and its related compounds, metabolites of Lasiodiplodia theobromae.

Administration of (13)C labeled acetates ([1-(13)C], [2-(13)C] and [1,2-(13)C(2)] to Lasiodiplodia theobromae showed the tetraketide origins of both theobroxide, a potato-tuber inducing substance [1, (1S, 2R, 5S, 6R)-3-methyl-7-oxa-bicyclo[4.1.0]hept-3-en-2,5-diol]) and its carbonyldioxy derivative [2, (1S, 4R, 5S, 6R)-7,9-dioxa-3-methyl-8-oxobicyclo [4.3.0]-2-nonene-4,5-diol]. The incorporation of acetate-derived hydrogen into 1 and 2 was studied using [2-(2)H(3), 2-(13)C]acetate. Three and one deuterium atoms were incorporated at one methyl and epoxy carbons, respectively. The observed loss of deuterium atoms from the methyl group suggests a considerable amount of exchange from the methyl group of [2-(2)H(3), 2-(13)C]acetate during biosynthesis of 1 and 2. Incorporation of [1-(13)C]- and [1,2-(13)C(2)]acetates indicates the carbonyl carbon of the carbonyldioxy derivative is derived from the carboxy carbon of the precursor.