Phospholipase D catalyzes the transfer reaction by which the phoshatidic acid moiety of phospholipid substrate is transferred to an acceptor alcohol. When the acceptor alcohol is highly hydrophilic, the reaction product is amphiphilic. Using the reaction, phosphatidyl derivatives of ethyleneglycol, diethyleneglycol, triethyleneglycol, glucose, glycerol, serine and ethanolamine were synthesized, and some emulsifying properties of them were compared with that of phosphatidylcholine, which is a natural surface active compound. All of the modified phospholipids were soluble in chloroform, and insoluble in water and soybean oil. Phosphatidylethanolamine, phosphatidylserine and phosphatidylglucose were insoluble also in kerosine. All the emulsions prepared with the synthesized compounds were O/W type, except the case of phosphatidylserine. The degree of oil and water separation from the emulsions prepared with phosphatidylethyleneglycol, phosphatidyltriethyleneglycol and phosphatidylglucose were smaller than the o hers. Phosphatidyldiethyleneglycol, phos phatidyltriethyleneglycol and phosphatidylglucose lowered the interfacial tention at water/ kerosine interface greater than the others. Therefore, phosphatidyltriethyleneglycol and phosphatidylglucoseshowed to be good surface active agents.

View full abstract

The influence of temperature on the quality of broccoli (Brassica oleracea L. italica group) under modified atmosphere packaging was studied. Samples were prepared as follows; (1) broccoli was packed with a perforated low density polyethylene film pouch of 0.03mm thickness at 10°C and stored at 10°C, (1) broccoli was packed with a non-perforated polyethylene film pouch of 0.03mm of thickness (PE 30) at 10°C and stored at 10°C, (1) broccoli was packed with PE 30 at 10°C and stored at 10°C for 2 days, and then transferred to 30°C for lday, and stored at 10°C again, (1) broccoli was packed with PE 30 after precooling (5°C) and stored at 10°C, (5) broccoli was kept at 30°C for 4 hours before packaging with PE 30, and stored at 10°C. The O₂/CO₂ concentration in the pouches of samples (1), (2), (3), and (5) after 8 days of storage were 18.4/0.5, 1.2/5.3, 0.4/10.8, 1.8/6.6, 0.3/9.0%, respectively. These results reflect the influence of the temperature on the respiration rate of broccoli. The sample (1) deteriorated visually in 4 days, and its chlorophyll and ascorbic acid contents decreased rapidly. No apparent changes in color had occurred in other samples. However, an unpleasant odor was detected in the samples (3) and (5) The develop ment of undesirable odors was mainly due to ethanol emanation under anaerobic condition. The sugar and ascorbic acid contents in the sample (3) decreased drastically after transferring of broccoli to 30°C. Among the sample conditions tested, marked effects on retaining sensory quality and on the delay of losses of chlorophyll, ascorbic acid and sugar were observed in the samples (2) and (4).

View full abstract

Thirty-seven samples of SHIITAKE mushroom [Lentinus edodes (Berk.) SING.] cultivated on logs and 19 samples of the mushroom cultivated on sawdust substrate beds paired with their substrate beds, which were all of unambiguous origins, were obtained. Comparisons of proximate and mineral compositions of the mushroom groups were conducted. Effects of the sawdust substrate composition on the mushroom composition were also examined. The contents of carbohydrate, Ca, Cu, Mn and Hg were significantly high in the mushroom cultivated on logs than that in the mushroom on sawdust substrate beds. On the contrary, the contents of moisture, protein, ash, K, P and Zn were high in the mushrooms cultivated on sawdust substrates. Nitrogen content of fruiting bodies cultivated on sawdust substrate was closely related to the content of the substrate. This fact well explained the difference in nitrogen contents between mushrooms cultivated on logs or sawdust substrates. Concentra- tions of elements to fruiting bodies From the sub trate beds were found in K (3.15 times), Na (1.68times), P (1.21 times) and Cd (11.58 times) but significant corelation between them was only found in P. Ca and Fe were not concentrated in fruiting bodies from the substrates, however, significant relations between fruiting bodies and substrates were observed.

View full abstract

Preparation and rheological properties of acid-induced gel of whey protein were investigated, using whey protein isolate (WPI) and glucono-δ-lactone (GDL) as an acidulant. A 6% WPI solution, pH7.0, was heated at 65-90°C in the absence of acidulant, then cooled t room temperature for obtaining partially heat-denatured WPI solution. The solution was incubated at 20-50°C in the presence of GDL. During incubation, the WPI solution denatured by heating to a certain extent was found to form gel below pH5.8, whereas undenatured WPI solution did not. The pH of the resultant finally reached 4.3 after incubation. Rheological properties of the acid-induced gel were dependent on temperature and time of the heat treatment of WPI solution, GDLconcentration, and incubation temperature. HPLC analysis indicated the formation of aggregates in heated WPI solution, and scanning electron microscopy showed the presence of finer networks tructure of whey protein aggregates in acid-induced gel with higher incubation temperature. It w s concluded that both the for mation of whey protein soluble aggregates by heating and a decrease of negative charge on the surface of the aggregates arising from a decrease of pH during incubation caused gelation.

View full abstract

Angiotensin I converting enzyme (ACE) inhibitory peptides were prepared from alkaline protease hydrolyzate of heated sardine muscle by applying on a column packed with AMBERLITE XAD-2 resin. The fractions eluted with water and stepwise gradient of ethanol were tested for inhibitory activity against ACE. The most active fraction (AF-1) was obtained by eluting with water and showed the 50% inhibition against ACE at 0.148mg protein/ml. Sensory evaluation revealed that the water soluble fraction (AF-1) had no bitter taste, while fish flavor was perceived as well as that of treatment with ODS resin. Two peptides were isolated from AF-1 by four steps of high-performance liquid chromatography. The amino acid sequences of two peptides identified by Edman degradation were Thr-Tyr and Gly-Trp, and their IC50 values for ACE were 288μM and 86μM, respectively. The yield of two peptides per 20g of sardine muscle were 40.0μg and 74.5μg, respectively, and these were found to be hydrophilic and high polar peptides.

View full abstract

A system consisting of a probe, a vibrator and displacement sensors, and a servo analyzer was developed to evaluate firmness of fruits and vegetables nondestructively. The probe whose top has spherical surface was set with initial loading force of 5 gf to a sample. The sample was vibrated with multi-sine wave which has the frequency ranged from 20 to 200 Hz. Both the displacement (input) and force (output) signals were measured at the same probe and transferred to the servo analyzer. A transfer function was calculated by the servo analyzed. With theoretical consideration, proposed that anti-resonant frequency, f_u, could be used as an index of firmness. The relationship between f_n and dynamic modulus, G', was examined in model specimens made of silicone rubber, which gave a logarithmic relationship with a correlation coefficient of 0.930. As an application to fruits and vegetables, tomatoes and strawberries in several storage conditions were measured by this system. In addition, conventional penetration test was also carried out to each sample. The initial force-displacement rate, w/d, which is equivalent to elastic modulus, was determined by the penetration test. There was the logarithmic relationship between f_n and w/d, which is the same as the model specimens' we observed, and the correlation coefficient was 0.899. These results indicate that this system is available for the easy and intact firmness evaluation for fruits and vegetables.

View full abstract

Antimicrobial property of water-soluble products obtained by degradation of 4-methylthio-3-butenyl isothiocyanate, the pungent principle of radish, was studied using 5 Gramnegative and 5 Gram-positive bacteria, 5 yeasts, and 9 fungi. Two antimicrobial components were found in the water-soluble products, of which the major one was isolated and indentified to be 2-thioxo-3-pyrrolidinecarbaldehyde on the bases of UV, MS, 1H-NMR and 13C-NMR spectral data. The identified compound exhibited a prominent growth-inhibition on the fungi and Gram-positive bacteria. The inhibitory effect on the yeasts and Gramnegative bacteria except for Escherichia coli was the least among the tested microorganisms.

View full abstract

In the course of the development of an industrial recovering system of limonoids from citrus processing waste, an efficient method to recover seeds from the citrus processing waste (peel residue) was developed. The residue was first passed on a vibrating sieve (φ14.5×14.5 mm) to remove peel fragments and other contaminants, and then the remaining material was degraded either chemically or enzymatically. The degraded fraction was sieved with mesh screen (φ4.5×50mm) and 85-90% of the seeds was recovered in optimal condition. The limonoid content in the seeds was not affected when the first fraction was treated with acid or enzyme. However, the content decreased when it was treated with alkali.

View full abstract

Fresh fruit juice including Sudachi, Yuzu, lemon and Kabosu and Ume-zu containing organic acids and Nigari components were using by applying the acid coagulation properties of soybean protein to examine their availability as a coagulation agent in the production of tofu. Tofu products being marketed using a chemically synthesized coagulation agent (calcium sulfate) were also tested as a control. The physical properties of the control products and test products were compared and examined. Production was carried out according to a common method employing automated production on a large-scale. Each fresh fruit juice was added at an amount of from 1.0-3.0% based on the weight of the soybean milk. In the 1.0-2.0% lots, the physical properties of the tofu products were somewhat insufficient, but the 3.0% lot showed good physical properties. The coagulation effects (rates) of the soybean milk prepared using fresh fruit juice as a coagulation agent were elevated with an increase in the addition ratio. They depended on the pH values of the fresh fruit juice per se. Namely, the coagulation effects were elevated under strongly acidic condition and the strongly acidic Ume-zu containing Nigari components showed further enhanced coagulation effects. When the coagulation effects were increased, the physical properties (hardness, penetration, elasticity and sectility) were increased and the products thus obtained scarcely differed from the marketed and control ones. In total, soft tofu products were obtained in these cases. The 3.0% fresh fruit juice lots showed the best results. In particular, excellent tofu products could be obtained in the Ume-zu and Yuzu lots, followed by the Sudachi, Kabosu and lemon lots. These results agreed with the strongly acidic pH values of the fresh fruit juice per se. The surface color tones of tested tofu samples differed greatly from those of the marketed products and the control products in numerical value. However, little difference was observed with the naked eye. Based on the these results, it is concluded that fresh citrus fruit juice are sufficiently applicable to the production of common tofu products from the viewpoint of physical properties.

View full abstract