An egg albumin solution (10w/v%) was subjected to Ohmic heating at 50Hz-10kHz under constant 10V/cm. The heating rate of solution was almost constant and slightly increased as the frequency increased. The gel formation was observed at about 75°C and the heating rate was considerably/appreciably increased above this temperature irrespective of frequency used. The solution and the gel showed almost the same impedance in the examined temperature range (20-90°C). When the concentration of egg albumin was reduced to 2w/v%, this solution gave no gel formation and showed the constant heating rate at temperatures below and above 75°C. Little difference in breaking strength was detected between the gels prepared by boiling water and by Ohmic heating. These results suggest that the liquid components are not compartmentalized in the gel and that the steep rise of heating rate above 75°C will be caused by the reduction of heat transfer of the gel attributable to phase transformation. Ohmic heating was also examined for fresh egg white at the same conditions as those for the egg albumin solution. The fresh egg white did not show any sudden increase of heating rate up to 90°C. However, the homogenized fresh egg white and thin egg white separated beforehand showed the slightly reduced heating rate and its abrupt increase at about 60°C. These results suggest that the gelatinous component, thick egg white, represses the transfer of generated heat during Ohmic heating.

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Mechanical characteristics of the korean noodle “Reimen” extruder which utilized frictional heat were investigated. The residence time ranged from 38 to 284 s. Puffing ratio gradually decreased as the increases of apparent viscosity of dough. Ordinarily, its maximum value was three times as much as the diameter of the hole of die. Volumetric flow rate, Q was represented by the equation Q=KN, where N was the rotational speed of the screw. Theoretical extruding energy, E₁ was given by the equation of E₁=1.810N²_ηap. Power number, N_p, was in the form of the product of Froude number, Fr, and Reynolds number, Re, namely, N_p=2.3×10³(Fr)^-0.46(Re)^-0.45. Heat by friction due to extruding comprised about 70% of all the practical heat.

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Factors affecting consumers' reaction to the informations on food safety were studied by questionnaire survey and interviews. (1) The subjects were classified into two groups, one is composed of those who reacted to and the other did not react to the safety informations of foods by using principal component analysis. (2) According to the questionnaire survey, the subjects who reacted to the safety informations had stronger interest in social problems, such as environment, welfare and politics than those who did not. (3) According to the interviews, the subjects who reacted to the safety informations showed more idealistic attitude to environmental conservation and more nervous attitude to the safety of food than those who did not. Through the above results, the primary factors affecting the consumers' reaction to safety of food seemed to be those concerned with values.

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To elucidate the components contributing to the strong antioxidative activity of roasted sesame seed oil, the oil roasted at 230°C for 15 min was diluted with n-hexane and passed through an Amberlite XAD-7 column. Most of the antioxidative products were adsorbed and could be separated from the major oil components. These were eluted with ethyl acetate as brown products. The products were then chromatographed on silica gel column and separated from the three known antioxidative components in the oil, i.e. γ-tocopherol, sesamol and sesamin (newly identified as a weak antioxidant), to give ethyl acetate-eluate and methanol-eluate brown products. Each of these products, as well as the three known antioxidative components, showed antioxidative activity, but, the activity of each alone was not so strong to explain the activity of the oil. Thus the synergistic effect of various combinations of the brown methanol-eluates and the three previous known components was examined. Synergistic effect was significantly observed when γ-tocopherol was involved in the combinations. The highest antioxidative activity was obtained with the combination of the brown product, γ-tocopherol, sesamol, and sesamin. These results suggest the importance of the synergistic effect in the activity of roasted sesame oil. (Received Feb. 13, 1996)

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The adsorption behavior of sucrose stearate (S170 : S, 200 ppm) to foam film in a casein solution (C, 0.87 wt%) at high temperatures around 60°C was investigated from dynamic surface tension measure-ments. Interfacial tensions between sucrose laurate (L195 : L, 200 ppm) and C at 25°C and 50°C andbetween S and C at 62°C and 88°C were also measured to understand the processes of the spreading and rupturing of the bubble film after adsorption. The dynamic surface tension decreased when 3.3 ppm of sucrose palmitate (P1 670 : P, 0-25 ppm) was added to the casein solution and the average particle size of S was adjusted to 8.7 ηm. These results were similar to those of our previous report of L having an antifoaming action to C at room temperature. A reduction in the dynamic surface tensionof S in C at 62°C, however, was not remarkable as compared with that of L in C at 25°C. The interfacial tensions between L and C and between S and C at their melting points (L : 23°C, S : 62°C)were 1.14 and 2.71 mN/m, respectively. Since these values were very low, the spreading coefficients calculated from the surface tension and interfacial tension were positive at the both temperatures.
From the above results, L and S are found to be able to rupture the foam film at room temperature andat high temperature, respectively. Thus, three parameters, i.e., dynamic surface tension, meltingpoint, and interfacial tension are useful in predicting the antifoaming ability of emulsifiers in C.

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A 3 elements mechanical viscoelastic model based on stress-relaxation curve was applied to evaluate the rheological characteristics of crumb of white bread under a wide variety of baking conditions and the storage time after baking. It was found that the rheological characteristics of crumb changed mainly with the elapse of the storage time rather than the baking temperature or the baking loss ratio defined as the percentage of the mass lost during baking to the initial. During the storage period of 1 hour no remarkable changes in the hardness and relaxation time of crumb were recognized with the different baking conditions. With the elapse of the storage time the relaxation time of crumb decreased rapidly and reached an equilibrium state after 12 hours. For the same mass lost the equilibrium values of the relaxation time indicated higher values with increase in baking temperature. The hardness of crumb increased exponentially with the elapse of storage time. And the maximum value of the hardness was shown for the crumb baked with the standard baking temperature of 220°C.

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Onion juice browned by heating was chromatographed on a Sephadex G-50 column. Browned compounds in the onion juice were fractionated into five peaks designated as A, B, C, D and E according to the elution order. Optical density at 400 nm of peak B increased by browning. Elution volume of peak B was a little larger than that of sugar or amino acid. The yield of non-dialyzable melanoidin of browned onion juice was 1/5 of total melanoidin. These results suggested that themain browned compounds of heated onion juice are low in molecular weight compared with model melanoidin.

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Quercetin, rutinose and an unknown product were produced through rutin degradation in the presence of ethanol by rutin-degrading enzymes (RDEs) I and II from tartary buckwheat (Fagopyrum tataricum Gaertner) seeds. The unknown product was identified as ethyl β-rutinoside by ¹³CNMR analysis. RDE I and II showed the highest activity in 15% (v/v) ethanol and at 50°C. Furthermore, under the conditions of 30% (v/v) ethanol and 1-2% rutin at 40°C, ethyl β-rutinoside was synthesized efficiently. Twenty-three grams of ethyl β-rutinoside was obtained from 50 g rutin upon the conditions. It was found that the addition of ethanol solution to tartary buckwheat flour was effective as a simple method of ethyl β-rutinoside synthesis. One hundred thirty-three milligrams of ethyl β-rutinoside was obtained from 20 g tartary buckwheat flour and 10 ml of 15% ethanol solution.

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To reveal a fundamental function of a volatile humectant such as propylene glycol, binary adsorption equilibria of propylene glycol and water vapors for tobacco leaves were examined with a flow-type multi-component adsorption system. Surface tensions were measured for aqueous solution of propylene glycol. The adsorbed amount of the propylene glycol as well as water increased with an increase in the vapor pressure of propylene glycol, under the constant conditions of temperature and vapor pressure of water. The surface tension for aqueous solution of propylene glycol was greater than that of ethanol. Therefore, propylene glycol was found to have a function of increasing the equilibrium moisture content of the tobacco leaves, causing the more capillary condensation.

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Changes in the contents of main components in tea leaves including dietary fiber were measured to investigate the influence of tea shoot development in the 1st crop season on manufacturing processes (green tea or black tea). With progression of tea shoot development, the SDF (soluble dietary fiber) content decreased, while the IDF (insoluble dietary fiber) content increased. The IDF content in black tea was higher than that in green tea, indicating that the oxidative polymerization during the manufacture of black tea had some influence on the DF content. The contents of sucrose, fructose and glucose increased during development of tea shoots in the 1st crop season, while the content of arabinosyl-inositol decreased. The content of arabinosyl-inositol in black tea was almost the same as that in green tea, suggesting that the content of arabinosyl-inositol becomes a usefulindication in distinguishing the degree of tea shoot development. Similarly, the contents of main free amino acids, epigallocatechin gallate, epicatechin gallate, (+)-catechin and caffeine decreased, while the contents of epigallocatechin, epicatechin and vitamin E increased.

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A score sheet for evaluation of grilled fish was established. The terms describing the general view of grilled fish were collected by interviewing with 5 professional Japanese cook masters, and a final selection of terms was made from answers from 60 professional Japanese cook masters. We then allocated 100 points in total to all the selected terms from interviews with 9 professional Japanese cook masters. After a sensory evaluation of common horse mackerel had been made under various grilling conditions with the trained panel, a multiple regression analysis was conducted. The final score sheet comprises seven terms, with three to five explanatory words for each term. The seven selected terms which are thought to best convey the quality of grilled fish and their assigned importance points are as follows: shape of the whole fish (10 points), condition of the surface (8 points), scorching (6 points), grilled color (20 points), handle with chopsticks (6 points), juiciness (25 points) and taste (25 points). Using this sheet, a sensory evaluation of many kinds of grilled common horse mackerel of various quality was carried out by the consumer panel. The correlation coefficient between the score by the trained panel and that by the consumer panel was 0.98.

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[in Japanese]

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