The purposes of this study are to examine texture changes of Japanese radish under high hydrostatic pressure and to clarify a mechanism of the changes. Fracture load and strain of Japanese radish were measured by a Rheoner. Both values increased with an increase in pressure to attain equilibrium above 4000kg/cm². In addition, a similar tendency was observed by increasing standing time after pressurizing. The pressurized samples absorbed more sodium chloride than the untreated sample when these samples were soaked in 0.5% sodium chloride solution. Impedance at a low frequency region decreased b0y pressurizing. The amount of Ca linked with pectin in the tissue increased with pressurizing time. Pectin esterase remained its activity and the degree of esterification of pectin decreased by pressurizing. The amount of water soluble pectin decreased, while that of hexametaphosphate soluble pectin increased. These changes enhanced with standing time after pressurizing. It was presumed that the function of cell membra e was lost by pressurizing in a short time, then the reaction between components in the tissue progressed with time and, as a result, resulted in the changes in the texture of Japanese radish.

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For measuring and controlling of coagulation process of soymilk, a new computerized measurement of rotational viscosity change of soymilk was investigated by use of the reformed Blabender Viscograph. The coagulant, 1M calcium chloride solution, was continuously added into soy milk which was contained in the rotating vessel of Viscograph. The three parameters, MV (maximum viscosity), FV (flat viscosity) and MVT (time For MV) were adopted to evaluate coagulation process of soy milk. The increased coagulation temperaure lowered both MV and MVT, but increased FV. A rotation speed of the reaction vessel much affected MVT, though MV was kept almost constant. Neither pottasium chloride nor sucrose which were previously added to soy milk affected MVT, comparable to their effects on Xml, "point of critical concentration of coagulant", in the electrochemical experiments reported previously. The concentration of soymilk was also found to be an important factor affecting these parameters. Further, a relationship between the viscographic parameters and Xml was investigated for a series of soymilks prepared from 19 varieties of soybeans, demonstrating that MVT correlated with Xml (r=0.862, p<0.01). The significance of MV as well as FV with respect to hardness of tofu was also discussed.

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This study was conducted to investigate the effects of chemical constituents in soymilk on the value of MVT (time for maximum viscosity) obtained from the torque measurement of coagulating soymilk with Brabender Viscograph. (1) A series of soymilk were prepared from each of 19 varieties of soybeans in order to know a relationship between the chemical constituents and the MVT value. (2) In model coagulation systems using a water extract of defatted soybean meal as well as adid-precipitated protein solution, the effects of concentration of protein and lipids and pH on MVT, MV (maximum viscosity) and FV (flat viscosity) were examined. Dialysis of the water extract of defatted soybean meal reduced MVT. On the contrary, addition of whey to the acid precipitated protein solution increased MVT. These results suggested that 65% of coagulant was consumed by protein fraction and 35% by whey fraction in coagulation process of soymilk. (3) MVT measurements as well as the chemical analyses were done using the whey dialyzed through membranes having molecular weight cut off 100-1000 daltons. It was revealed that the coagulant-consuming substances in the whey fraction were such substances of 300 to 1000 daltons that were assumed to be citric acid, phosphorus compounds, peptides, or their complexes.

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The contents of nickel and other heavy metals in cacao beans and its processed products was studied. For the study, 26 samples of cacao beans, 14 of cacao mass (bitter chocolate), 10 of cacao butter, 14 of commercially available chocolate (black, 9; white, 5) and 4 of powdered cocoa were collected. (1) On the average, the content of nickel was about 5 ppm in both cacao beans and cacao mass, while only 0.03 ppm in cacao butter. The contents of iron and copper were also observed little differences between cacao beans (x: 112.4ppm Fe, 24.7ppm Cu) and cacao mass (x: 82.5ppm Fe, 26.7ppm Cu), while markedly low in cacao butter (x: 0.30ppm Fe, 0.04ppm Cu). (2) Nickel was detected 1.09 ppm on average in the black type of the chocolate, while only 0.14ppm or less in the white type. Powdered cocoa contained 12.7ppm of nickel on average, much higher than the content in cacao mass. Such tendency was also observed in the cases of iron and copper: black type, white type of chocolate and powdered cocoa contained, on average, 24.4, 0.82 and 362.5ppm of iron and 5.36, 0.16 and 43.9ppm of copper, respectively. Meanwhile, lead and arsenic were not detected in all samples. (3) As reference samples, shea and Borneo nuts and coffee beans contained 0.58, 0.45 and 0.55 ppm of nickel, 85.4, 137.1 and 67.0ppm of iron and 0.72, 10.8 and 13.3ppm of copper on average.

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Changes in the distribution of low molecular weight carbohydrates, polysaccarides, and organic acids in the vegetative mycelia of Agrocybe cyklindracea (Fr.) Maire (yanagimatsu- take mushroom) were studied through the vegetative growth. The low molecular weight carbohydrate content was in the range of 1.1-11.6% in dry materials. In the vegetative mycelia, trehalose, mannitol, glucose, fructose, myo-inositol, arabitol and glycerol were identified, and trehalose was found to be major among them. It was supposed that trehalose might act as a major respiratory substrate. The polysaccharide content was in the range of 47.8-55.5% in dry materials. Glycogen accumulated in the vegetative mycelia was thought to be served as a reserve carbohydrate. The organic acid content was in the range of 0.6-3.3% in dry materials, and ten organic acids were detected. Malic, citric, pyroglutamic and fumaric acids were found to be predominant.

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Frozen tofu prepared by using both pressure-shift freezing and air-blast methods was examined in terms of inside ice crystals and texture as the physical and chemical structure of tofu is easily changed during freezing. The ice crystals made by pressure-shift freezing were granular in form, and smaller in size than those by the other method. The tofu's components, except ice crystals, were kept between ice crystals, so that the components enclosed each ice crystal like a wall. The pressure-shift frozen wall was 1-3μm thick at -18°C, and in the air-blast frozen tofu, it was 30-100μm thick. Thawed at room temperature, the air-blast frozen tofu dripped and deformed while maintaining a rigid central core. On the other hand, the pressure-shift frozen tofu did not deform and maintained a homogeneous structure, suggesting that phase change during freezing occurred nearly simultaneously throughout the tofu. Futhemore, the appearance, taste and resistance to the teeth of the sample, which is frozen by pressure-shift f eezing method at -18°C, were about the same as those before freezing.

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In order to judge the freshness of ground coffee easyly, we studied on several simple methods. We found a relationship between the time course of titratable acidity of coffee brew and the time when fresh-roasted flavor of ground coffee disappered. Titratable acidity was measured by potentiometric automatic titrator. The ground coffee samples were stored at 25°C and 37°C. The coffee brews of samples was judged for their fresh-roasted flavor by sensory evaluation test with just roasted comparing sample. Titratable acidity of ground coffee brew decreased in several days, then it reached an unchanging state. The time at this knick point of titratable acidity was clossely related to the time at which fresh flavor of coffee disappered. The time of knick point of titratable acidity was 7 days and 4 days for stored tempretures 25°C and 37°C, respectively. It will be expected that measuring the titratable acidity of coffee brew can replace sesory evaluation test to judge freshness of ground coffee.

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A flow injection analytical system for the determination of L-tyrosine was developed. The system included an immobilized enzyme reactor, in which L-tyrosinase was immobilized on controlled pore glass supports. The system was applied to the L-tyrosine determination in oyster extracts which were treated with proteolytic enzyme. Oxygen consumption involved in L-tyrosinase enzyme reaction was monitored. The carrier solution used was 0.1M phosphate buffer (pH 7.2). The detection limit was 0.01mM, and the range for determination was 0.1-1.0mM. The relative standard deviakion was 1.9% for 10 successive determinations at 0.5mM level. When the system was applied to the determination of L-tyrosine in oyster extracts, the results were in good agreement witht hose obtained by the HPLC method. The system appeared to be useful for monitoring of L-tyrosine in oysker exkract treaked with proteolytic enzyme.

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Extraction of hemicellulose from corn bran under alkaline conditions using a twin screw extruder was examined. Extruding pressure was adjusted by a volume of NaOH solution added to the corn bran. Samples were supplied into the extruder by gravity feed. The pressure increased from l to 16 kg/cm² with decreasing water content in corn bran. In the case that the amount of NaOH was fixed, extraction rates of hemicellulose did not increase against increasing pressure. The best extraction rate was attained when 0.5 or 1.0N NaOH was added at 2-2.5 times weights of corn bran. These results suggest that mixing and dispersion effects with viscosity fall inner the twin screw extruder are more important factors for extraction of hemicellulose than high pressure.

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Enzymatic treatment has been reported to be useful for improving cooking qualities of old crop rice grains. This paper deals with improving mechanical qualities of the enzymatically treated grains for handling and transportation. Steaming and gelatin- coating were applied on the enzymatically treated grains. The steamed grains were dried by hot air blow. The gelatin-coated grains were dehydrated with ethanol followed by cold air drying. Both of the procedures mechanically strengthened the enzymatically treated grains and, as a result, decreased broken grains. The steamed and gelatin-coated grains gave cooked rice samples with favorable texture and sensory properties.

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As foods are easily infected with one or more fungi, contamination by different mycotoxins may occur. High-performance liquid chromatographic (HPLC) methods were examined for separation and detection of coexistent mycotoxins. Mycotoxins were devided into two groups by amino type (BOND ELUTE NH₂) mini-column chromatography, and each mycotoxin in both groups was analyzed using reversed-phase HPLC with ultraviolet and photo diode-array detectors. These results were confirmed by HPLC and normal-phase thin layer chromatography. Mycotoxins belonging to group-1 and group-2 are as follows: group-1: aflatoxin B₁, B₂, G₁, G₂, M₁, M₂, ochratoxin A, citrinin, patulin, sterigmatocystin and zearalenone, group-2: deoxynivalenol, nivalenol and fusarenon X. Recoveries of 11 mycotoxins of group-1 and 3 mycotoxins of group-2 spiked to rice and corn at the level of 50 ppb were 70-94% and 50-71%, respectively.

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In order to reduce an amount of wastes in water exhausted by production of minced fish meat, treatments of high pressure was examined. The amounts of protein and solid matters could be reduced considerably by the pressurization up to 300MPa accompaning with filtration, centrifugation, pH adjustment and coagulation with sodium polyacrylate or aluminum sulfate. The best condition for the effective use of recovered materials was at 400MPa, followed by the adjustment to pH 5 and centrifugation at 3000×g for 5 minutes. This treatment reduced BOD, COD, solid and fat contents of the water and increased the transparency. Surfactant such as SDS inhibited the effects of high pressure. E. coli was completely killed and other general microorganisms were drastically reduced at 300MPa.

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