The autoxidation of the ethyl esters of n-3 and n-6 fatty acids, abbreviated as PUFAs (polyunsaturated fatty acids), was followed by analysis using thermogravimetry and calorimetry as well as by gas chromatography. The thermogravimetric measurements indicated that the stoichiometric coefficient between n-6 PUFA and oxygen was 1 during the entire autoxidation, and that the coefficient between n-3 PUFA and oxygen was dependent on the unoxidized substrate fraction. For n-3 PUFAs, the coefficient was 1 when the fraction was greater than 0.5, and the coefficient became larger as the autoxidation proceeded (i.e., the unoxidized fraction was less than 0.5). Calorimetric measurements also gave the same results. The heat of the autoxidative reaction based on moles of oxygen consumed was almost constant for both the n-3 and n-6 PUFAs, and it was not dependent on the unoxidized substrate fraction.

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A damped oscillation rheometer was used to observe the gelation process of soy proteins. A small amount (∼1 cm³) of sample sol in a capped container was subjected to repeated rotational oscillations at a high temperature. The logarithmic damping factor (LDF) and the period of the oscillations were derived from the damped oscillation curve. Since the LDF value first increased and then decreased during the gelation, the increase in LDF was a good indication of the initiation of the sol-gel transition.

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A microbial sensor consisting of immobilized Thiobacillus ferrooxidans and an oxygen electrode were prepared for the determination of ascorbic acid (AsA). A linear relationship was obtained between the sensor output and the concentration of AsA below 2.5 mM. The minimum detectable concentration of AsA was 0.1 mM. The response was reproducible with a 4.1% relative standard deviation when 1.5 mM of AsA was measured 20 times. The total time required for an assay was about 5 min. A good agreement was obtained between the microbial sensor and the 2,4-dinitrophenylhydrazine (DNP) method in the analysis of AsA in foods. Organic compounds did not affect the analysis. The activity of the microbial membrane was stable for more than 30 days.

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We investigated the effects of the fermentation with Bacillus natto on the allergenicity ascribed to the major soybean allergen, Gly m Bd 30K. Time dependent decreases in 1) reactivity for IgE antibody from a soybean-sensitive patient and 2) reactivity for a monoclonal antibody were observed during fermentation, and the electrophoretic patterns of the proteins in the fermented soybean showed all the proteins were hydrolyzed to the small fragments with molecular weight below 10,000. These results suggested that the epitopes of the Gly m Bd 30K against the mouse monoclonal IgG and human serum IgE were decomposed by the digestion with the proteases of Bacillus natto during fermentation and that natto might be a hypoallergenic soybean product.

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The compressive fracture stress of lipid-free tofu was measured at temperatures between −20°C and −196°C and compared with that of lipid-containing tofu to examine the effect of lipid on the fracture stress of concentrated amorphous solution (CAS). In the calculation of the fracture stress of the CAS, the compressive fracture stress of food was regarded as a volume-fraction-weighted average of the fracture stress of each component of which the food is composed. The fracture stress value of CAS in frozen full-fat tofu was found to agree with that of lipid-free tofu provided that the frozen tofu was assumed to consist of pure water ice, lipid, and lipid-free CAS. The compressive fracture stress of selected frozen foods other than tofu was also measured.

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Thermogravimetry under nitrogen atmosphere was applied to measure the distribution coefficients of maltooligosaccharides upon a cation-exchange resin. Thermal degradation of the solute occurred at about 200°C and its weight decreased gradually with increases in temperature, while that of the resin occurred above 350°C. The solute distributed in the resin also degraded at that temperature. Thus, it was demonstrated that thermogravimetry was applicable to measurement of the distribution coefficient. The coefficients determined by this method coincided well with those determined by the conventional method. Because the amount of solute distributed in the resin became large when the bulk concentration of solute was high, the thermogravimetric determination of the amount was more accurate. Thus, this technique was useful for the measurement of the coefficient at higher bulk concentrations of solute.

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A new “Ethanol Adsorption Treatment” (EAT) for a filter has been presented to depress the migration of volatile flavor and water in a box of a tobacco product during storage and marketing. The EAT is performed by applying the binary vapor of water and ethanol to the filter tip before connecting it with a tobacco column. During the EAT, ethanol was adsorbed physically on the filter as an additive agent, and thus the water content within the filter tip was controlled to a desirable level at which the water does not migrate. Then during storage, the presence of ethanol vapor depressed the flavor migration mainly by decreasing the amounts of flavors adsorbed on the activated carbon within the filter tip. The EAT was confirmed to be effective for decreasing both the water and flavor migration simultaneously.

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Solutions of soybean protein with and without added oil were freeze-dried, and the measured drying-rate was analyzed using the uniformly retreating ice front (URIF) model to obtain the coefficient of vapor permeability, K. The drying-rate was maintained high when the solution was frozen without supercooling, and the vapor permeability was inversely proportional to the cooling rate. An uncontrollable supercooling occurred even at the low cooling rate resulting in a texture for the frozen sample along with a low vapor permeability. The addition of oil induced a relatively uniform ice structure through out the sample and the drying rate was low but almost remained constant until about 90% of the frozen sample was freeze-dried. The relationship between the supercooling and the ice structure was also confirmed by the temperature distribution in the drying sample and the SEM photographs of the dried sample.

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Hesperidin glycosides are the transglycosylated products of hesperidin by CGTase (cyclodextrin glucanotransferase, EC 2.4.1.19). They are significantly more soluble in water than hesperidin and can be used as the stabilizer of natural pigments against ultraviolet irradiation. Furthermore, it was revealed that hesperidin glycosides could prevent the formation of hesperidin crystals, which cause turbidity in canned mandarin orange syrup or cloud in clarified mandarin orange juice, in aqueous solutions. Hesperidin glycosides were more effective than β-CD in preventing the turbidity in the model syrup of canned mandarin orange, and were also effective in preventing the cloud in the model orange juice. The use of hesperidin glycosides only involves adding them to the solution in order to prevent turbidity or cloud. As they were autoclavable and did not have any taste, hesperidin glycosides could be used as an agent to prevent turbidity in canned mandarin orange syrup or the cloud in clarified mandarin orange juice.

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Multivariate analysis was applied to 35 volatile components and sensory scores of 16 Kenyan black teas made of tea leaves of two clones cultivated at eight areas. Although profiles of volatile components in black teas belonging to a clone deviated according to their harvesting areas, cluster analysis and factor score plots clearly showed differences in the two clones. Multivariate calibration methods provided equations predicting sensory scores using volatile components. Multiple linear regression analysis (MLR) selected 1-penten-3-ol, (E,E)-2,4-heptadienal and linalool oxide as effective components and the resulting multiple correlation coefficient (R) was 0.914. The optimum number of principal components indicated by cross-validation was three in the partial least squares (PLS) regression analysis with an R value of 0.946. A higher correlation of components eluted after linalool, i.e., α-cedrene, 3,7-dimethyl-1,5,7-octatrien-3-ol, cedrol and bovolide, to tea quality was suggested by factor loadings of PLS. Principal component regression (PCR) with four principal components showed the lowest R (0.811) among the three calibration methods.

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UHT-treated milk reduced 3'-{1-[(phenylamino)-carbonyl]-3,4-tetrazolium}-bis(4-methoxy-6-nitro)benzenesulfonic acid hydrate (XTT). The reducibility was caused by the Maillard reaction intermediate between milk protein and lactose. First, the assay procedure of the XTT reduction was optimized using the heated model solution containing casein and lactose and UHT-treated milk. When the XTT reduction assay was applied to two kinds of UHT-treated milks under optimum conditions, the ability of each milk sample to reduce XTT significantly reflected the extent of the heat treatment as well as the evaluation method using the hydroxymethylfurfural (HMF) value. In contrast to the HMF value, the ability of UHT-treated milk gradually decreased depending upon the storage period and temperature. These results suggest not only that the present XTT assay is applicable to estimate the extent of heat treatment but also that the reducibility of the milk sample heat-treated under a given condition can serve to estimate the storage period if the storage temperature is known or vice versa. The method is much simpler (only mixing of the XTT solution containing menadione with milk sample) and quicker (about 20 min) with a satisfactory reproducibility than the conventional methods to estimate the extent of the Maillard reaction such as the lactulose or HMF determination.

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We established a simple method to quantify hydrogen peroxide (H₂O₂) generated during the aerobic heating process of (+)-catechin solution. Using this method, we found that non-enzymatic H₂O₂ formation from catechin depended on pH, temperature, incubation time, and the presence of O₂ in the solution. The formation of oxidized products of (+)-catechin, which was estimated by measuring the absorbance of the solution at 430 nm, also depended on these factors. The H₂O₂ formation was inhibited by various kinds of superoxide dismutase (SOD) with almost the same dose dependency. Although the oxidation of (+)-catechin was enhanced by superoxide (O₂⁻), neither catalase nor H₂O₂ had any effects on the oxidation. These results suggest that O₂⁻, rather than H₂O₂, participated in the autoxidation of (+)-catechin, which was coupled with the H₂O₂ formation.

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Ascorbate oxidase (AAO) obtained from the young fruits of satsuma mandarin was utilized for the enzymatic determination of ascorbic acid (AsA) based on the difference spectral method as a possible new source of AAO, and the result was compared to cucumber AAO. A linear relationship was observed between AAO activity calculated from the maximum peak height of the difference spectra and the concentration of AsA in the range of 0-100 μg/ml. The values of AsA determined by the enzyme were also comparable to the values obtained using cucumber AAO. Thus, AAO from the fruit could provide a cheaper source of the enzyme for AsA determination, making it a potentially viable alternative to a more expensive commercial purified AAO.

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In order to explore the relationship between proteinase and fruit body growth and basidiospore formation in mushrooms, the metallo proteinase from the pilei in the fruit bodies of Enokitake (Flammulina velutipes) was purified and characterized. The metallo proteinase was highly purified (194-fold) with a recovery of 5.90%. The enzyme was the most active at pH 6.5 toward casein, and stable only within the narrow range of pH 6.0 to 8.0 even under mild temperature (37°C, 30 min). The molecular weight and isoelectric point were found to be 18,000 and pI 6.0, respectively. The enzyme was strongly inhibited by MK-I or synthetic metallo proteinase inhibitors such as ethylenediamine-tetraacetic acid and o-phenanthroline. These characteristics were compared with those of other metallo proteinases, and the possible roles of the enzyme are discussed.

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