The author has already reported that the paste of heated soy protein isolate changed to the gel (cold-gel) during cold storage. In this paper, effects of emulsifiers, fatty acids and alcohols on the gelation of the soy protein isolate during cold storage were investigated. The effects of emulsifiers on gel texture of the cold-gel were dependent on their types. The hydrophobic groups of emulsifiers were more related with the gelation phenomena than their hydrophilic groups, but the hydrophile-lipophile balance (HLB) of sucrose fatty acid esters had no effect on the gelation of the soy protein. Fatty acids prevented the gelation of the protein, and especially unsaturated fatty acids prevented the gelation compared with saturated fatty acids. Alcohols also prevented the gelation of the protein. However, there were no significant differences on jelly strength and deformation among alcohols-added cold-gels. From the results mentioned above, it was suggested that the prevention effects of fatty acids and alcohols against soy protein gelation were attributable to the hydrophobic interaction between these molecules and the protein molecules, and were caused by interference of hydrophobic interaction among the protein molecules.

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We investigated about the cause of foaming and the mechanism of its stabilization during frying held in ordinary home kitchen. An extent of foaming was measured by frying sliced potato and estimating the height of bubble layer by placing a cylinder over it. The sliced potato was found to increase bubbling greatly when treated with wheat flour, an egg and crumb. Analysis of the easily bubbling oil revealed that the coexistence of phospholipid and glycolipid accelerated bubbling. Thus it has been elucidated that the phospholipid extracted from an egg and the glycolipid from wheat flour are the major cause of bubbling. Fluorescent measurements using fluorescent probe-bearing phospholipids showed that phospholipids could adsorb at the interface between oil and water, and form molecular assemblies. From scanning electrical microscopic observation of bubble films, a multilayer structure of polar lipid was found to exist. When bubbles developed over oil surface were cooled to separate water, these polar lipids adsorbed to form a multilayer, lamella-type structure, which was presumed to stabilize the bubble film.

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Salted ume fruit (Japanese Apricot, Prunus mume Sieb. et Zucc. var. microcarpa Makino) is one of the traditional food produced in Japan. Two kinds of salted ume-processed products, ‘Ume-boshi’ and ‘Ume-zuke’ are known. There is currently great importance for the prevention of contamination with film-forming yeasts on ‘Ume-boshi’ and ‘Ume-zuke’ in the recent trend of reducing salt content in foods. So, we investigated on the ingredient changes of products contaminated with film-forming yeasts. And, isolation, identification and characterization of contaminated yeasts were performed. According to the progress of contamination with yeasts, organic acids chiefly contained in salted ume-processed products were observed a significant decrease, by which the pH risen. And, the hardness of the flesh of a ume fruit of ‘Ume-zuke’ deteriorated and pectin related compounds were decomposed. It was suggested that these loss of organic acids and decomposition of pectin related compounds were mainly caused by contaminated yeasts. Seventy five of yeasts strains were obtained by isolation and purification of yeast strains from decomposing products contaminated with yeasts. Respective twenty five isolates were identified on the basis of standard morphological and biochemical tests as strains of Debaryomyces hansenii (4 isolates), Pichia anomala (1 isolate), Pichia membranaefaciens (3 isolates), Torulaspora delbrueckii (1 isolate), Kloeckera apiculata (2 isolates), Candida famata (1 isolate), Candida krusei (3 isolates), Candida pelliculosa (3 isolates) and other unidentified Candida sp. (7 isolates) designated as Candida sp. UME-A, Candida sp. UME-B and Candida sp. UME-C. As the results of characterization of yeasts isolates, strains of C. fatama, Candida sp. UME-A, Candida UME-B showed a high salt tolerance (halophilic) which could grow in YM liquid media contained 20% NaC1 and showed a high acid tolerance which could grow at ume-vinegar solution (contained of 1.58% citric acid, 0.76% malic acid and 7.97% NaC1) adjusted at pH 2.0. And, strains which were resist to low pH had a high ability of assimilation of organic acid and induced rise of the pH of ume-vinegar. In conclusion, it was suggested that these strains which had a high ability of assimilation of organic acid in ume-vinegar solution were main yeast contaminant in salted ume-processed products.

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We examined inhibitory effects of a sausage containing soy protein isolate on increase in serum lipid levels in 13 adult male subjects (27-62 years old) induced by high fat diet with 110% of total energy (25-30% of fat energy ratio) to the safe and adequate daily intake for each subject. Serum total cholesterol (p<0.01), free cholesterol (p<0.01), triglyceride (p<0.01) and phospholipid (p<0.05) levels were significantly decreased and HDL-cholesterol level (p<0.001) was significantly increased by the intake of the sausage (9.9g/person/day) containing soy protein isolate (about 9.9g/135 g) added to daily conventional high fat meals for 2 weeks. Daily dietary intakes of animal fat, plant fat, saturated, polyunsaturated, ω-3 and ω-6 fatty acids, cholesterol, animal protein, plant protein, carbohydrate and total energy and ratios of polyunsaturated to saturated fatty acids (P/S) and ω-6 to ω-3 fatty acids (ω-6/ω-3) were not significantly altered during test (sausage intake) period for 2 weeks and two control periods fed high fat diets for 1 week before and after the test period (p>0.05). There were no clinical findings and no remarkable change in body weight by the intake of the sausage. These results suggest that a sausage containing soy protein isolate may suppress the increase in serum total cholesterol and other lipid levels and the decrease in HDL-cholesterol level induced by high fat diet in adult male subjects.

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The cytotoxicity of foods was determined on the base of the rate of vitamin K₃-catalyzed H₂0₂production by mammalian cells. Vitamin K₃-catalyzed H₂₀2 production and the chemiluminescent assay of H₂0₂ require 10min and 5 s, respectively. This cytotoxicity test was useful for the rapid detection of weak cytotoxic antioxidants such as BHA and BHT, and the preservatives such as esters of p-hydroxybenzoate. These cytotoxic effects were observed a few hours after the incubation with NIH/3 T 3 cells. The cytotoxic effects of alcoholic drinks, non-alcoholic drinks and liquid foods were also observed 24 h after the addition of drinks or foods to NIH/3 T 3 cells.

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The relation between tasting substances and results of organoleptic tasting test was studied to evaluate properly umami taste of toasted nori. Dried nori produced at Ariake Sea in Kyushyu in 1995, was toasted at 200°C for 5 sec, and the tasting substances were extracted with water at 35°C for 30 sec, considering actual eating condition. Free amino acids and nucleotides of the warm water-extract were analyzed by HPLC, and the taste of the same sample was evaluated by ten inspectors. It was thus concluded that the analysis of the tasting substances in the warm water-extract was proper to study the tasting of toasted nori as compared with that in an ordinary hot 80% ethanol extract. The correlation coefficient (r) between 5' -inosinic acid in the warm water-extract and the score of tasting test (taste score) was high (r=0.839), as compared with those for the other tasting substances (less than r=0.496). The taste index was defined by authors as follows: taste index=(glutamic acid contentx IMP content)/1000, because of taste synergism with L-glutamate and 5'-IMP in which the umami taste is enhanced. This index demonstrated a good linear relation (r=0.873) with the taste score, providing a new possibility for the taste evaluation of toasted nori.

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The nutrient status of vitamin D in human is evaluated on the basis of the 25(OH)D concentration in plasma. Therefore, after taking the vitamin D-fortified eggs, the 25(OH)D concentrations in plasma of healthy subjects were determined. Twelve healthy male volunteers, aged of 25 years to 38 years, were equally divided into two groups : one group was administrated with vitamin D-fortified eggs and the other administrated with vitamin D tablets. Fifty grams of omelet containing 9.70 μg of vitamin D₂ and 1.05 μg of vitamin D₃ prepared from vitamin D-fortified eggs was supplied for 15 days. While a tablet containing 10.83 μg of vitamin D₂ was supplied for 15 days. 25(OH)D₂ was not initially detected in plasma but was detected in both groups at the end of the feeding period. Thus, it was suggested that vitamin D₂ in the eggs was absorbed in the body and then transformed to 25(OH)D₂. Whole 25(OH)D concentrations in both groups increased, and 25(OH)D₂ occupied around 20% in total 25(OH)D. These results suggested that vitamin D-fortified eggs contributed to improving the nutritional status of vitamin D in healthy subjects as vitamin D tablets did.

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Production of the vitamin D₂-fortified shiitake mushroom powder in an industrial scale was attempted. The optimum UV irradiation condition such as the irradiation time, UV beam energy and particle size of shiitake mushroom powder were investigated using an industrial scale machine. A vibration feeder was used to uniformly vibrate and agitate shiitake mushroom powder. Shiitake mushroom powder was spread in uniform thickness by this feeder so that the mushroom could be uniformly irradiated. Vitamin D₂ in shiitake mushroom increased proportionally to the irradiating time when the supplying volume of raw material was constant. For manufacturing shiitake mushroom powder containing a sufficient amount of vitamin D₂, supplying volume of raw material should be controlled or the irradiating time should be extended. Consequently, the manufacturing capacity of this machine for producing the vitamin D₂-fortified shiitake mushroom containing 200 μg/g was about 10 kg/h. By examining the conversion efficiency of ergosterol into vitamin D₂ in shiitake mushroom with this machine, the yield of vitamin D₂ per UV energy was estimated to be 6.9 ng/ mW·sec. Although the vitamin D₂ content slightly increased when the mean particle diameter of the mushroom became smaller, the relative surface area of the particle was not the significant determinant for the vitamin D₂ content. These results suggested that fine shiitake mushroom powder was not sufficiently agitated by this machine.

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