Firmness of mume (Japanese apricot) fruits packaged with polyethylene bags and inclusion of ethylene absorbent were measured and relationships with pectic substances, respiration rate and ethylene production were determined. (1) The firmness of the fruits packaged with ethylene absorbent was held at higher level during at 20°C, whereas those of the fruits packaged with perforated or sealed bags lowered rapidly. The sealed-package delayed the occurrence of climacteric rise and lowered the increase of ethylene production from the fruits. The inclusion of ethylene absorbent in the bag markedly enhanced the suppressive effects. (2) The ratios of water soluble-pectin (WP), sodium hexamethaphosphate soluble-pectin, and hydrochloric acid soluble-pectin (HP) contents to total pectin content in the fruits were 29%, 3%, and 68%, respectively, at harvest during the storage at 20°C, total pectin content did not change obviously but increase of WP and decrease of HP occurred markedly as the softening of fruits advanced. Inclusion of ethylene absorbent conspicuously retarded these changes. (3) changes of Sephacryl S-300 gel filtration pattern revealed that higher molecular pectins in HP and WP fractions were decomposed into lower molecular pectins with advance of softening of mume fruit during ripening and these decomposition of pectins was suppressed in the fruit packaged with ethylene absorbent.

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Manufacturing conditions for the processed cheeses possessing fibrous structure using a twin screw extruder and a conventional kettle-type cooker were investigated. Two types of cheeses, Gouda cheese ripened for 2 weeks and Emmental cheese ripened for 8 months, were used, and whey protein concentrate (WPC, protein conc. 75%) was added to each cheese at optimum concentration to obtain fibrous structure. In extrusion cooking, each ground cheese blended with WPC was fed into a barrel and cooked at 70-90°C. The extruded thermoplastic mass was cooled to approx. 45°C in a low-shear kneader and stretched to obtain fibrous structure. In both cheese types, fibrousness of the resultant products cooked at 70 and 80°C was satisfactory and superior to that at 90°C. Observation of the products under an optical microscope indicated that cooking temperature was correlated with fibrousness. A decrease of fibrousness, occurred when cheese was cooked at 90°C, was due to mutual adhesion of protein strand by heat. When kettle-type cooker was employed, fibrousness of the product cooked at 80°C for 0 min was inferior to that cooked at the same temperature by the extruder, and an increase of holding time at 80°C during cooking was also found to affect fibrousness adversely. A twin screw extruder which can complete cooking in short residence time was indicated to be suitable for manufacturing processed cheese possessing fibrous structure.

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Protein-bound fluorescence was examined for dried foods containing lipids such as soybean flour, peanut flour, Kori-tofu (dried soybean curd), and Yuba (dried soymilk skin) by solid sample fluorescence spectrophotometry. All samples gave fluorescence spectra with the excitation wavelength at 430-440nm and the emission wavelength at 500-510nm, and the fluorescence intensity were increased during storage. Formation of the fluorescence was derived from lipid peroxidation in foods because it was inhibited by extraction of lipids or addition of BHT. Although the fluorescence intensity depended on varieties of dried lipid foods, it was positively correlative to carbonyl value of extracted lipids. These observations showed that determination of protein-bound fluorescence intensity is simple and available for evaluating the oxidative deterioration of lipids in dried foods.

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Stability of green tea catechins during processing of canned green tea drink including sterilization by a retort or a heat exchanger was investigated. From the simulation test of the process of canned green tea drink, it was found that, (1) catechins decreased in almost all of process including holding in a filler bowl (95°C) or a reservoir (55°C), (2) the largest decrease of catechins occurred during retort sterilization, (3) an addition of small amount of L-ascorbic acid (AsA) was effective on the stabilization of catechins in green tea drink. For example, in the case of retort sterilization at 121°C for 6min. (lethality, F₀=4), the decrease of catechins in green tea drink was restrained 45% by an addition of AsA (20mg/100ml). Moreover, the decrease of catechins was negligible by an addition of AsA (20mg/100ml) in the case of the sterilization at 135°C for 32 sec. (F₀=4) by heat exchanger. Therefore, avoiding excess heating through the processing and adjusting pH of tea infusion slightly acidic by an addition of small amount of acid such as AsA are required to retain catechins in canned green tea drink.

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Texture of "nori" (a kind of seaweed products) was evaluated by both sensory test and instrumental measurement using texturometer and correlations among scores obtained by both evaluation methods were examined. Three textural parameters, toughness, easiness to maceration, and crispness, were adopted in sensory test. In case of hoshi-nori, a sort of dried "nori", three sensory parameters showed good correlation with each other, and in case of yaki-nori, a sort of roasted ones, good correlations were observed except for correlation between toughness and crispness of yaki-nori. It can be concluded that it is more difficult to macerate and bite off the tougher "nori" by teeth. Although the toughness by texturometer showed good correlations with both sensory toughness and easiness to maceration, but less correlated with sensory crispness. Since toughness by texturometer of hoshi-nori showed good correlations with that of yaki-nori, texture of yaki-nori can be estimated from that of hoshi-nori. Moreover, there was good correlation between the texturometer toughness and the contents of porphyran in"nori", which is said to be a factor of toughness of "nori" thalus itself.

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The effect of an added amount of egg yolk or egg white on the consistency of new emulsified product prepared from fish was investigated. The flow property of the emulsified product was expressed by the power law equation including the exponent, n. In the product with yolk-ratios of 0.1 and 0.2, the structure breakdown was significant during the rotational measurement of flow property, since the difference in yield stress value was large between the increasing and decreasing shear rate determinations; the shear stress was large in the increasing shear rate depending on large n values and it was small in the decreasing shear rate depending on small n values. The absolute values of yield stress obtained from the compressive measurement of the flow property were almost the same as those from the rotational measurement of the flow property. The hysteresis loop area surrounded by the increasing and decreasing shear rate curves was large for a yolk-ratio of 0.1 while it was small for a yolk-ratio between 0.3 and 0.6. The product with a yolk ratio of 0.2 was in the transition state from a shear-unstable emulsion to a shear-stable one. Both storage modulus, G', and loss modulus, G", decreased with the increase of yolk-ratio. The G" value was larger than the G' value for the product with any yolk-ratio. It was found from the above results that with yolk-ratio of 0.3 or more, the shear-stable emulsion was prepared.
In the white-added product, the yield stress obtained from the compressive measurement of the flow property increased with the increase in white-ratio from 0.2 to 0.5 and decreased with the ratio of 0.6. This tendency coincided with that observed in the hysteresis loop area obtained from the rotational measurement of the flow property. For the white-ratios from 0.2 to 0.5, the yield stress values obtained from the compressive measurement of the flow property were almost the same as those obtained from the increasing shear rate determination of the rotational flow property. However, for the ratio of 0.6, the former yield stress value was one-half of the latter. Both the storage modulus, G' and loss modulus, G", increased with the increase in white-ratio from 0.2 to 0.5 but decreased for the ratio of 0.6. For the ratios of 0.2 and 0.3, the G' value was almost equal to the G" value while for the ratio of 0.4 or more, the former value was larger than the latter. The white-added product was brittle, as shown in these results.

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The effect of n-butanol addition and ultrasonication on the thermal gelation of yellowfin tuna myofibrillar proteins was investigated in connection with protein denaturation. The thermal gelation of yellowfin tuna myofibrillar paste was greatly enhanced by the addition of 0.2M-0.6M n-butanol. When the pastes were ultrasonicated, the effect of added n-butanol on the gel-strength was heightened. During ultrasonication, a rapid desalting from the paste occurred. The amount of precipitated actomyosin at low ionic strength increased with n-butanol addition. Though the actomyosin ATPase activities decreased rapidly by the addition of 0.6M n-butanol, a marked thermal activation of the Mg-ATPase was observed in the presence of 0.2 M n-butanol. The significant role of the myosin tail portion in the thermal gelation was discussed.

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The solubilities of Bb (soyasaponin I), one of the major monodesmoside saponins in soybean seeds, were measured in aqueous ethanol and buffer. Bb showed the highest solubility in 60% ethanol, and was more soluble in alkaline region in buffers prepared at various pHs. On the other hand, Bb'(soyasaponin III) and B-G (3-O-β-D-glucuronopyranosyl soyasapogenol B) were almost insoluble in buffer. Solubilities of Bb, Bb'and B-G in buffer were increased by the addition of Ab (acetyl-soyasaponin A1), which is one of the major bisdesmoside saponins in soybean seed hypocotyl. The solubilizing effects of bisdesmoside saponins on monodesmosides, which are responsible for some physiological effects in soybean, may be important for processing beneficial foods using saponins for human consumpution.

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[in Japanese]

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