The antioxidant activity of vitamin E (α-tocopherol) during the peroxidation of unsaturated lipids has been reviewed based on its reaction products. Free-radical scavenging reactions of α-tocopherol take place via the α-tocopheroxyl radical as an intermediate. If a suitable free radical is present, a non-radical product can be formed from the coupling of the free radical with the α-tocopheroxyl radical. The reaction products of α-tocopherol with lipid-peroxyl radicals are 8a-(lipid-dioxy)-α-tocopherones which are hydrolyzed to α-tocopherylquinone. If the supply of oxygen is insufficient, α-tocopherol can trap the carbon-centered radicals of lipids to form 6-O-(lipid-alkyl)-α-tocopherols. On the other hand, the dimer and trimer of α-tocopherol is formed by the bimolecular self-reaction of the α-tocopheroxyl radical in a reaction mixture containing a large amount of α-tocopherol. The other product-forming pathway yields isomeric epoxy-α-tocopherylquinones and their precursors, epoxyhydroperoxy-α-tocopherones, but the mechanism of this pathway remains unknown. The reaction products of other vitamin E compounds (γ- and δ-tocopherols) during lipid peroxidation are almost the same as those formed from the α-tocopherol. The tocopheroxyl radicals of γ- and δ-tocopherols prefer to react with each other to form dimeric products that are still effective as antioxidants.
Actomyosin gel prepared from frozen-stored carp showed the increase of the creep compliance and the decrease of instantaneous elasticity when compared with the gel prepared from non-stored fish. However, actomyosin gel prepared from frozen-stored piranha did not show the change of these rheological parameters and remained unchanged in texture. The addition of transglutaminase resulted in decreasing the creep compliance, by increasing the instantaneous elasticity, retarded elasticity, and Newtonian viscosity whether the gel was prepared from non-stored fish or from frozen-stored fish. The transglutaminase addition resulted in increasing the percentage of the compliance of instantaneous elasticity and decreasing the percentages of the compliances of retarded elasticity and Newtonian viscosity of the gels. Therefore, it was considered that the transglutaminase formed the cross-links more easily between the polypeptide chains which were located very closely each other to get entangled, while some part of polypeptide chains remained without cross-links. As the result, the actomyosin gels became highly elastic.
To investigate heat transfer phenomena in cylindrical foods of different dielectric properties with microwave heating, the dielectric constant, loss factor and the temperature distributions of samples were measured. The temperature distributions changed with their dielectric properties (dielectric constant, loss factor and penetration depth). As the penetration depth increased, the region of high temperature moved from the surroundings of the cylinder to the center. To describe these phenomena theoretically, the temperature distributions in the samples were calculated under the same conditions as those in the experiments using the mathematical model. The calculated results agreed closely with the experimental values.
Progressive freeze-concentration utilizes the concentration phenomena of a solute at the ice-solution interface moving from one end of a vessel to the other end. It is characterized by having only a single ice crystal in the system so that the separation of the ice crystal from the concentrated solution is very easy compared with the conventional method of freeze-concentration. Progressive freeze-concentration was applied to a solution containing glucose and/or blue dextran as a model liquid food. The freeze-concentration ratio and apparent partition coefficient of a solute between the ice and the solution phases were strongly dependent on the moving speed of the freezing front and the stirring speed at the ice-solution interface. A lower moving speed and a higher stirring speed produced a better freeze-concentration ratio.
Lipase modification by addition of lipid is a simple and effective way to greatly improve enzyme activity for n-hexane based interesterification and hydrolysis reactions. The ranges of modifying lipids and lipases were evaluated, with stearic acid and lipase Saiken 100 (Rhizopus japonicus) investigated in more detail. Enzyme protein recovery and activity were influenced by the quantity of stearic acid addition and the pH of the aqueous preparation phase. Modified lipase protein was characterized using SDS-PAGE electrophoresis. In addition, modified lipase was immobilized within alginate beads allowing for easy biocatalyst separation and re-use for hydrolysis reactions in n-hexane.
A vegetable model was constructed in order to evaluate its apparent absorption coefficient and penetration of infrared radiation within it. Carrot, daikon (Japanese radish), eggplant, potato, pumpkin and sweet potato were prepared as the test vegetables. This vegetable model was composed of the dry vegetable material, liquid and gas, and its apparent absorption coefficient was calculated with their absorption coefficients and volumetric fractions. The volumetric fraction of the voids (void fraction) was obtained experimentally by a method provided in this study. Thus the damping of infrared rays within the vegetable model irradiated by near-infrared (NIR) or far-infrared (FIR) radiation was estimated in consideration of the spectral distribution of the radiation. The infrared radiation absorbed by the vegetable model was indicated to be damped to 1/100 of the initial value at a depth of 0.21 to 2.54 mm, and the penetration depth in the case of NIR irradiation was deeper than that of FIR irradiation. Moreover, the calculation results suggested that the penetration depth of infrared radiation became deeper with a decrease in the water content.
The effects of a 2% sucrose palmitic acid ester coating were studied on the internal oxygen, carbon dioxide and ethylene concentrations of banana fruits in relation to ripening, respiration and ethylene production during storage at 20°C after treatment with 100 ppm ethylene for 12 h. The 2% sucrose palmitic acid ester coating on the bananas covered the stomatal aperture, suppressed initial respiration and decreased the rate of ethylene production which ultimately retarded degreening and significantly delayed (P<0.01) ripening. The internal oxygen concentration of the bananas was significantly (P<0.05) reduced by the coating treatment without elevation of the internal carbon dioxide level. Low internal oxygen concentration significantly reduced (P<0.01) the rate of ethylene production of the coated bananas during 9 days in storage. These observations indicated that coating with the sucrose palmitic acid ester modified the internal atmosphere of banana fruits and suppressed initial respiration in a manner analogous to modified atmosphere storage.
An ultrafiltration unit, the ES-30 membrane (molecular weight cut-off 30,000) was used to recover the proteins from the wastewater produced during mungbean starch processing. During ultrafiltration, the permeate flux of the unit decreased from 108.5 to 4.0 l/m2/h due to fouling and concentration polarization. The flux could be restored to 10.8, 40.7, 50.0, and 82.4 l/m2/h by washing individually with tap water, 0.5% NaOH, 0.2N HCl, and 0.75% Terg-A-enzyme, respectively. The cleaning effect was significantly affected by the cleaning agents and their concentrations. The cleaning effect of NaOH was enhanced by mixing with 0.1% Triton X-100 (a surfactant). After ultrafiltration, continuous circulation with tap water for 10 min, followed by 0.3% NaOH mixed with 0.1% Triton X-100 for 10 min, 0.2 N HCl for 10 min, and by 0.75% Terg-A-enzyme at 50°C for 30 min nearly restored the original flux of the unit. Circulation with water was immediately required after each washing with cleaning agents, especially with acid or basic solution. One and a half hours was sufficient to complete the washing process.
A new fermented soy protein (SP) food was manufactured, employing a new starter, Bacillus subtilis (natto), isolated from jang. The new fermented SP food manufactured with textured soy protein and triple distilled water contained similar constituents of jang manufactured with the same jang starter. The relative viscosity, γ-glutamyl transpeptidase activity and elastase activity were 2.5 to 3.0, 2.0 and 3.7 to 5.5 times higher than those of jang, respectively. Furthermore, the optimum conditions to produce the relative viscosity and enzymes were investigated. The new fermented SP food had a higher elastase activity than did jang and natto, while the constituents were similar to those in jang and natto.
The leaf oil components in hybrid seedlings of ‘Seto unshiu’ (Citrus unshiu MARC.) crossed with ‘Morita ponkan’ (Citrus reticulata BLANCO) as the pollen parent were examined. The leaf and peel oil components in the hybrid seedlings were also compared with those of their parents. Twenty eight of the 32 peaks found in the hydrocarbon fraction of the leaf oils were identified. The major compounds were γ-terpinene and β-caryophyllene in ‘Seto unshiu’ and sabinene and β-ocimene in ‘Morita ponkan.’ All 40 peaks found in the oxygenated compound fraction of the leaf oils were identified. The major compounds were linalool, (Z)-3-hexenal, and (Z)-2-hexenal. There was a correlation between the leaf oil and peel oil in the percentage of the oxygenated compound fraction in the hybrid seedlings. A similar correlation was found for the parents. When the hybrids were classified according to the major kinds of monoterpenes, such as sabinene and γ-terpinene, and thymol and α-sinensal, the same groupings were obtained with the leaf and peel oils. These results suggested that the flavor of the fruit can be predicted by analyzing the oil in the leaf, which can be sampled much earlier than the fruit.
The antihypertensive action of protease hydrolysates derived from chum salmon head was investigated by oral administration to spontaneously hypertensive rats (SHR), and the angiotensin I-converting enzyme (ACE) [EC 22.214.171.124] inhibitory peptides were isolated from them. Hydrolysates by Biopurase SP-10 showed the highest ACE inhibitory activity in vitro. The systolic blood pressure of SHR treated with the hydrolysates orally decreased from 200.6±5.0 to 177.2±9.9 (0.05<p<0.1) 24 h after administration. From the hydrolysates, two peptides having ACE inhibitory activity were isolated. Their amino acid sequence was Gly-Ile-Gly and Asp-Trp and had the IC50 values of 730 μM and 13 μM, respectively. Asp-Trp was one of the strongest ACE inhibitory dipeptides ever reported in food protein hydrolysates.
Four main theaflavins:-theaflavin, theaflavin-3-gallate, theaflavin-3'-gallate and theaflavin-3,3'-digallate are produced during black tea processing. For tea fermented for same duration the relative composition of the individual theaflavins varied with clones, but were not affected by agronomic practices like nitrogenous fertilizer rates, planting density, and plucking standards. The relative composition of the theaflavins therefore provides a semiquantitative method of discriminating between clones with large genetic variations and can be used as a quality selection criteria in breeding/clonal selection of black tea.
2-Thioxo-3-pyrrolidinecarbaldehyde (TPC), a major product generated from the pungent principle of radish in an aqueous medium was studied to characterize the mode of antimicrobial action. The minimum inhibitory concentration (MIC) of TPC was measured using 25 strains of microbes. The MICs against fungi and bacteria ranged from 50 to 400 μg/ml, while yeasts were more resistant. The effects of TPC on the growth of spores and mycelia of Eurotium chevalieri and on the survival of Staphylococcus epidermidis were investigated, which suggested that the antifungal and antibacterial actions were due to the sporicidal and bactericidal activities. Also, the effects of TPC on uptake of oxygen and radioactive precursors for RNA, DNA, proteins, peptideglycans, and lipids were examined in S. epidermidis. A dose-dependent inhibition of the uptakes of both oxygen and the precursors was observed, suggesting that TPC caused damage to the mitochondrial functions and biosynthetic systems of the biological materials.
The effect of wasabi leafstalk (Wasabia japonica MATSUM.) extract on bone metabolism in a tissue culture system using mouse calvaria in vitro was investigated. The calvaria tissues obtained from normal mice were cultured for 48 h at 37°C in 5% CO2/95% air in Dulbecco's modified Eagle's medium (high glucose, 4.5g/dl) containing either vehicle or wasabi leafstalk extract (10, 50 and 250 μg/ml of medium). Wasabi leafstalk extract was obtained from a homogenate with 20% ethanol. The presence of wasabi leafstalk extract (10 μg/ml) caused a significant increase in calcium content and alkaline phosphatase activity in the bone tissues. With higher concentrations (50 and 250 μg/ml), however, the effect was weakened. The bone deoxyribonucleic acid (DNA) content was not significantly altered by the presence of wasabi leafstalk extract (10 and 50 μg/ml). The wasabi leafstalk extract-induced increase in bone calcium content was completely prevented by the coexistence of cycloheximide (10-6 M), an inhibitor of protein synthesis, suggesting that the effect of wasabi leafstalk extract is based on a newly synthesized protein component. Meanwhile, the anabolic effect on bone calcium content was not seen in the presence of the ethanol extract (50 μg/ml) from loquat leaf, cherry leaf, dried shiitake, gabaron tea, green tea (sencha), muskmelon, satsuma mandarin, tomato, blueberry, and soy bean. The present study demonstrates that wasabi leafstalk extract has an anabolic effect on bone calcification, in vitro.
Enzymatic activities in cecal contents were studied on rats fed on high cholesterol diets with ferulic acid arabinoxylan ester (FAX) and arabinoxylan (AX); both were processed from refined corn bran (RCB) and were compared with those of cellulose(CE)- and RCB-fed rats. The enzymatic activities in the ceca changed according to the diets. Xylanase activity, arabinofuranosidase activity and ferulic acid esterase activity appeared in the cecum of the FAX- and AX-fed rats, but these activities were not observed in the cecum of CE- and RCB-fed rats. FAX and AX showed a tendency to decrease serum cholesterol levels. At first, xylanase and arabinofuranosidase were supposed to attack the FAX and AX main chain and side chain, and thus high molecular weight FAX and AX became lower molecular weight fragments. At that time, ferulic acid esterase was presumed to attack and FAX was degraded lower. These enzymes might act synergistically.
The difference in reaction conditions between the syntheses of mono- and diacylglycerols (MAG and DAG) was elucidated in terms of the enzymatic glycerolysis of high-oleic sunflower oil containing 89% oleic acid. The most efficient lipases were Pseudomonas lipoprotein lipase and the lipase from Pseudomonas cepacia for the MAG and DAG syntheses, respectively. In each case, the glycerol amount to be added to maximize the yield was 1.5-fold larger than the stoichiometric amount that is necessary to complete the glycerolysis reaction. The addition of a small amount of acetone to the reaction mixture was only slightly effective on the yield of MAG. The control of the reaction temperature was very important, and the critical temperature, below which the yield of MAG or DAG is significantly increased, was found to be lower for DAG synthesis than for MAG synthesis. The reaction time that was required to obtain a maximum yield was about 80 h for MAG synthesis, while it was 6-fold longer for DAG synthesis. The content of MAG and monooleoylglycerol approached 90 and 80% in the lipid reaction products, respectively. On the other hand, the content of DAG was 82%, of which the fatty acid composition was similar to that of the original oil.
An alginate lyase was purified from an extracellular enzyme (commercial preparation) of Flavobacterium multivolum K-11 by successive column chromatographies, such as cation exchange, chromatofocusing, and gel filtration. The purified enzyme migrated as a single band on SDS-PAGE and analytical isoelectric focusing. The molecular weight of the enzyme was 32,000 by SDS-PAGE and 33,000 by HPLC gel filtration chromatography, and the pI of the enzyme was 8.2 on isoelectric focusing. The enzyme exhibited maximum activity at pH 7.5 and 40°C, and was stable between pH 6.0 and 9.0, and at temperatures up to 20°C. The enzyme activity was remarkably inhibited by chemical compounds such as SDS, MIA, TNBS, and N-bromosuccinimide, while EDTA and PCMB had no effect on the enzyme activity. The enzyme decomposed both the G-block (guluronic acid content; 89%) and the M-block (mannuronic content; 92%) at nearly equal rates, and produced several kinds of unsaturated oligomers. Because such activity of alginate lyase has not been reported, we believe that this is a novel alginate lyase.
The enantioselective analysis of the volatile components in Citrus sudachi peel oils was achieved using an enantioselective capillary gas chromatography (enantio-cGC) with α- and β-cyclodextrin columns. The two isomers of linalool and α-pinene showed highly significant differences in both odor detection thresholds and odor qualities. The other investigated compounds also differed either in the odor intensities or in the odor qualities. According to limited odor units (ratio of the concentration of each component to the odor threshold), (3S)-(+)-linalool, (3R)-(—)-linalool, octanal, (4R)-(+)-limonene, (1R,5R)-(+)-α-pinene, p-cymene, γ-terpinene, myrcene, 1,8-cineole, (3R)-(+)-citronellal, decanal, α-phellandrene and dodecanal contributed to the Citrus sudachi aroma.
Inhibitors of lipid accumulation in Lipomyces starkeyi were screened from various kinds of foods from the point of anti-obesity. An extract of black pepper showed inhibition of lipid accumulation with apparently weak repression of its growth. An active component was isolated from black pepper and was identified as 2(E),4(E)-decadienoic acid by instrumental analyses. Pepper contains about 20 mg/100 g of 2(E),4(E)-decadienoic acid. The minimum inhibitory concentrations of 2(E),4(E)-decadienoic acid against microbial growth ranged from 60 to 1000 μg/ml. The acid inhibited the growth of L. starkeyi at 100 μg/ml and the lipid accumulation at 12-50 μg/ml. The repression of lipid accumulation in L. starkeyi by 2(E),4(E)-decadienoic acid seemed to be due to the inhibition of glycerol-3-phosphate dehydrogenase and growth.
Near infrared (NIR) diffuse reflectance spectrophotometry was applied to measure stored milled rice by focusing on the outer layer flour. Rice grains milled 90% were stored at 37°C and 75% humidity for 0-45 days. NIR and chemical analyses were performed separately on the outer and inner layers and whole flours of the sample. The most sensitive variation during storage of the absorption intensity by NIR is found on the outer layer flour at the near-infrared region of 2300-2310 nm which corresponds to fats; the fat content of the outer layer extracted by ether was about 15 times that of the whole layer flour.
The anitigenic activity of ovomucoid (OM) remaining in bread samples containing egg white was analyzed at several stages of bread making; dough preparation, kneading, fermentation and baking. Change in OM antigenicity at each stage was examined using competitive ELISA with rabbit anti-OM serum. OM antigenicity was remarkably reduced by baking but not by kneading and fermentation. The antigenicity completely disappeared in the breads baked at 150°C for 4 min or more, even though it substantially remained when egg white was heated alone under the same condition. OM in the baked bread samples was solubilized with SDS/2-ME-containing solution but not with the solution containing SDS alone, suggesting that baking with wheat flour induced irreversible denaturation of OM with a disulfide exchange reaction leading to the loss of its antigenic activity.
Whey syrup was prepared by immobilized β-galactosidase and its specific rotation was determined. The rate of lactose hydrolysis and the specific rotation of whey syrup increased as the reaction time increased. The specific rotation of whey was +52.41°and that of whey syrup markedly increased and finally reached +78.82°by enzymatic reaction. The increase in specific rotation in the whey syrup indicates that its sweetness increases, and therefore, the whey syrup can be used in such foods as canned fruit, soft drinks, ice cream, and frozen yogurt as a sweetener. There was a positive correlation between the changes in specific rotation and the rate of lactose hydrolysis within a definite reaction time; therefore, a novel method based on the measurement of specific rotation can be used to calculate the rate of lactose hydrolysis and sweetness in the process of whey syrup production. Changes in specific rotation coincided with the changes in galactose content during the reaction; thus, galactose production is the most important factor which determines the changes in specific rotation in the whey syrup.