DIRECT MEASUREMENT OF BITING PRESSURES FOR CRACKERS USING A MULTIPLE-POINT SHEET SENSOR

A multiple-point sheet sensor was used to observe the distribution of surface pressure during the biting of crackers adjusted to various water activities. The textural characteristics were clearly reflected in the three-dimensional displays so obtained. Textural differences between samples were most evident in the first 0.3 s. The magnitude, position and duration of biting pressure varied among subjects. For all subjects, crisp crackers with low water activities showed a large pressure distribution with respect to both time and position. Samples with high water activities displayed a higher maximum force on the area under the incisors than samples with low water activities, and required more work per incision. These results are opposite to the rheometric data measured with a single-point sensor. Using this method, we could directly display textural differences due to the mechanical and geometrical properties of food, and could evaluate their changes in the oral cavity during biting.     

Cellulose Derivatives Effects on Gelatinization and Retrogradation of Sweet Potato Starch

Effects of physically or chemically modified celluloses on gelatinization and retrogradation of sweet potato starch were examined by Theological measurements and differential scanning calorimetry. The mixture of sweet potato starch and four modified celluloses (powdered microcrystalline cellulose, alkaline soluble fibrous cellulose, carboxymethylcellulose and methylcellulose) in the ratio of 9 to 1 was used as a model, because that ratio of starch to cellulose is about the same for sweet potato root. Cellulose derivatives generally did not show important effects on gelatinization temperature and enthalpy of gelatinization. Cellulose derivatives which are not water-soluble increased starch retrogradation, while water-soluble methylcellulose unexpectedly prevented retrogradation.     

EFFECT OF SAMPLE THICKNESS ON THE BITE FORCE FOR APPLES

The thickness of a piece of food and its mechanical properties affected the bite force. A multiple-point sheet sensor was used to measure the bite force applied to apple specimens of various thicknesses during the first bite with incisors. The results of wedge penetration tests on the same samples were compared with results of the bite measurements. The maximum bite force increased with the sample thickness for two apple varieties, though the maximum load measured by the wedge penetration test did not change. Therefore, it is important to consider that not only the mechanical properties but also the thickness of the sample affects the required bite force.     

Induction of adaptive response <i>in utero </i>by ionizing radiation: A radiation quality dependent phenomenon

Investigation on possible induction of adaptive response (AR) by high-liner energy transfer (LET) particle radiation for protection against low-LET photon radiation-induced detrimental effects has not yet been performed in utero. This study verified if an AR could be induced by high-LET particle radiation from accelerated heavy ions against low-LET X-ray radiation-induced detrimental effects on fetal mice. Total body irradiation of pregnant C57BL/6J mice were performed by delivering a priming dose ranging from 10 mGy to 320 mGy of particle radiation on gestation day 11 followed one day later by a challenge dose at 3500 mGy from X-ray radiation. The monoenergetic beams of carbon, silicon and iron with the LET values of about 15, 55, and 200 KeV/μm, respectively, were examined. Significant suppression by the priming radiation of the detrimental effects (fetal death, malformation, or low body weight) was used as the endpoints for judgment of a successful AR induction on gestation day 18. Existence of AR was not observed. On the other hand, the priming dose of high-LET particle radiation, in some cases, even increased the detrimental effects induced by the challenge dose from low-LET X-ray radiation. Although existence of AR induced by high-LET radiation in cultured mammalian cells in vitro and in certain tissues of laboratory mice in vivo was demonstrated, the present study did not suggest that low dose of high-LET particle radiation could induce an AR in fetal mice in utero under the setup of our experimental system.     

Measuring Texture of Crackers with a Multiple-point Sheet Sensor

A multiple-point sheet sensor was used to observe the distribution of pressure on the surface during fracture of food. This multiple-point measurement was compared with a single-point measurement of uniaxial compression for crackers with different water activities. Textural characteristics were clearly reflected in the pressure distribution data successively detected by the multiple-point sensor. Little pressure distribution appeared during compression of a homogeneous sample. Crackers with low water activity showed a wide pressure distribution both with time and at different positions. The multiple-point measurement directly determined textural differences caused by the mechanical and geometrical properties of the crackers.     

Reaction of Strontium Carbonate with Anatase and Rutile

The kinetics of the solid-state reaction of strontium carbonate with anatase and rutile in air and carbon dioxide were studied by use of a thermobalance. The product was single-phase SrTiO₃ in all cases. The relation between fraction reacted and time was fitted to the Jander equation and to the Carter equation for both anatase and rutile. For anatase the rate constant in carbon dioxide did not differ from that in air. The reaction rates for rutile in air and in carbon dioxide were ⅓ and ⅛ that for anatase, respectively. The In k vs 1/ T relation for anatase gave two straight lines with different slopes having a break point at ∼820°C in both air and carbon dioxide. The Jander activation energies for anatase in the higher and lower temperature regions were ∼340 and ∼290 kj · mol⁻¹, respectively, and those for rutile in air and carbon dioxide were 340 and 390 KJ · mol⁻¹, respectively.     

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.     

日本地下管道安装与水处理相关技术

日本下水道协会于 1 998年 7月 2 8日至 3 1日 ,在日本的北九州市举办了第 1 1回下水道展。本文简要介绍了展示会情况 ,以及管路铺设、水处理及污泥处理设施、维修管理等方面所开发的新技术     

ELECTROMYOGRAPHIC STUDY ON COOKED RICE WITH DIFFERENT AMYLOSE CONTENTS

The texture of six varieties of cooked rice with different amylose contents was measured with a Texturometer. Masticatory behavior of the rice was evaluated using electromyography (EMG) of masticatory muscles. Differences in mastication patterns among the seven subjects examined were greater than between rice varieties. Masticatory behavior was more related to the adhesiveness and stickiness of rice as measured using a Texturometer than to the hardness. The number of chews and masticatory time, total duration of mastication and total muscle activities were highly correlated with each other, and were greater in cooked rice with a high amylose content, which showed low adhesiveness and stickiness values using a Texturometer. Cooked rice with a high amylose content was masticated with high masseter muscle activities. The ratio of jaw-opening muscle activity to the preceding jaw-closing muscle activity was low in high-amylose varieties, which corresponds to the ratio of stickiness to hardness using a Texturometer. Between-sample differences in mastication parameters were more apparent in the early stage of mastication, and no significant diference was observed in the late stage.