The large differences in thermal properties between water and ice cause thermal properties of frozen food to be strongly dependent on ice fraction, which is a function of solute concentration and temperature. Effective thermal conductivity of frozen food is described well by the dispersed model with ice phase dispersed in consideration of ice fraction. Ice crystal structure size in frozen food is determined by the advance rate of ice front reflecting the important role of the molecular diffusion of water in the mechanism of ice crystal growth. Supercooling causes the formation of very fine ice structure through the very high freezing rate at the moment of the cease of supercooling but the similar effect is realized by the pressure-shift freezing as a thermodynamically controllable process. By controlling the ice crystal structure size very large, the progressive freeze-concentration becomes possible. This method is very effective to make the freeze concentration system much simpler as compared with the conventional method of suspension crystallization to reduce the cost of freeze concentration substantially.
For a long time, it had been considered that soybean storage proteins play only a role as traditional nutrients and other soybean minor constituents such as isoflavones, saponins, trypsin inhibitors, phytic acid, lectin, etc., act as antinutrient factors. At present, however, these substances have all been recognized to have exciting roles in the prevention of heart disease, cancer, osteoporosis, etc. Besides these physiological effects, soybean storage proteins exhibit excellent functional properties physicochemically in food systems, such as gelation, binding, emulsification, fat and water absorption, etc. On the other hand, there are some substances having undesirable properties in soybeans, such as off-flavors, allergens, etc. Recently, there was a great progress in the research of a molecular basis on these functionalities, off-flavors, and allergenicities. By applying these results for soybean breeding, the creation of the new cultivars or lines having more improved properties is in progress. Another highlight in soybean research is the success of the crystallization of β-conglycinin and glycinin and the subsequent complete determination of their three-dimensional molecular structures through X-ray crystallographic analysis. This paper overviews these recent investgations.
Masticatory pressure caused by chewing with molars was measured using a multiple-point sheet sensor. The sensor system is useful to directly indicate masticatory force and contact area with various subjects. Mastication of kelp snack, which is difficult to cut in several chewing strokes and thus seems to be a good food for masticatory training, was analyzed. Peak force, contact area at peak, peak pressure, duration, cycle time and impulse were highly varied among subjects, but were not influenced by the breaking force of the kelp. The experimental results show that humans did not change their masticatory pattern at least during the first several chews of the kelp samples which are difficult to cut with teeth. In the first chew, masticatory pressure is lower and duration and cycle time are longer than the following several chews. This suggests that subjects are afraid of an unknown sample texture. Individual peak force in mastication was independent of the contact area, but highly correlated with the peak pressure. Subjects with a high impulse value, corresponding to a large amount of work in mastication, had a high masticatory force, but did not show long duration.
Transfructosylation catalyzed by fructooligosaccharide-producing b-fructofuranosidase from Aspergillus niger ATCC 20611 was kinetically studied and a reaction model of transfructosylation was proposed. Kinetic parameters (Vm, Km, and Ki) were determined from experimental data on the transfructosylation rates at various substrate concentrations with and without addition of glucose. Transfructosylation reaction was found to be inhibited non-competitively (Ki=0.12 mol l−1) by glucose. Simulation results in sugar composition due to the action of a β-fructofuranosidase were in good agreement with the experimental data. In order to get higher reaction conversion with a simultaneous removal of glucose, a membrane reactor system was developed using nano-filtration membrane, through which glucose permeated but sucrose and fructooligosaccharides did not permeate. Fructooligosaccharide percentage of the reaction product was increased to above 90%, which was much higher than that of the batch reaction product (55–60%) and comparable to that of the chromatography processed product. The membrane reactor system will be applicable for production of fructooligosaccharides.
This study was undertaken to generate useful information regarding the change of quality of parboiled rice for different processing conditions through the change of physical properties and to search for correlation among the quality indicators. Physical properties, namely, maximum viscosity, hardness of brown rice, hardness and adhesion of cooked rice, volume expansion ratio and solid content were investigated. A first order kinetic model predicted well the effect of processing conditions on the maximum viscosity and hardness of brown rice, indicating the quality index and rate of change of quality with their respective final and reaction rate constant values. The effect of steaming period was found to be greater on the quality indicators of cooked rice, such as adhesion, volume expansion ratio and solid content. Good linear correlation of gelatinization property with the cooking quality and rheological property of parboiled rice was achieved. The positive correlation between adhesion and solid content is assumed to be responsible for producing a less sticky product.
Conditions for preparing W/O/W emulsions with a polymer in the aqueous phase as a possible entrapping agent to produce powdery multiple emulsions were investigated for food applications of W/O/W emulsions. The stability of these emulsions prepared using various types of emulsifiers was evaluated by the encapsulation efficiency of a hydrophilic marker molecule in the inner aqueous phase. Combinations of hexaglycerin polyricinoleate (Sunsoft 818SX) and soybean lecithin or gum arabic used in the first and second emulsification steps were suitable to prepare stable W/O/W emulsions. Emulsions containing.10% (w/v) polymers in the outer aqueous phase were successfully prepared using these emulsifier pairs by adding the polymers to the emulsions after homogenization. Addition of polymer to the inner aqueous phase did not have a significant effect on emulsion stability in spite of expected alleviation of osmotic pressure difference between the inner and outer aqueous phases.
Linoleic acid was encapsulated with gum arabic, maltodextrin and pullulan at different weight ratios by hot-air-drying and freeze-drying. The autoxidation processes of the encapsulated linoleic acid were observed at 37°C and at various relative humidities. Linoleic acid encapsulated by hot-air-drying was more stable at the lower humidities regardless of the kind of wall material. Linoleic acid encapsulated with gum arabic by freeze-drying also showed a similar dependence on the humidity. Linoleic acid in the microcapsules freeze-dried with maltodextrin and pullulan was very stable against autoxidation at intermediate humidities, while it was very easily autoxidized at low or high humidity. This tendency was remarkable for microcapsules prepared with pullulan.
Antioxidative activities of thirty kinds of citrus essential oils and their fourteen components against linoleic acid oxidation were examined by a thiocyanate method. The tocopherol contents of these oils were determined by high-performance liquid chromatography monitored at 290 nm. All the citrus essential oils and the flavor components showed inhibitory effects against linoleic acid oxidation. Highest antioxidative ability was observed in the essential oils of yuzu, lemon, hassaku, sudachi, mochiyu, yuko and Tarocco orange. Antioxidative activities of β-pinene, myrcene, α-terpinene, γ-terpinene and decanal were higher or similar to that of d-tocopherol. Tocopherols were contained abundantly in the essential oils of limes, Valencia orange, yuzu and lemons. However, there was little correlation between tocopherol contents and antioxidative activities in citrus essential oils. The composition of terpene compounds seems to be a major factor in the antioxidative activities of these oils.
The gel strength of charcoal-treated bovine serum and porcine serum proteins at a concentration of 8% was determined with different concentrations of NaCl after heating at 80°C for 15 min at pH 7.0. The charcoal treatment considerably enhanced the gel strength of porcine serum protein, and also improved gel strength of bovine serum protein at NaCl concentrations between 75 mM and 150 mM. The gel strength of commercial PSA and BSA and that of fractionated bovine and porcine proteins by ion-exchange chromatography were also determined at a constant NaCl concentration. With the charcoal treatment, the gel strength of fractions containing albumin increased, while that containing globulin decreased. The gel strength of charcoal-treated bovine serum and porcine serum remarkably increased by the addition of the egg white, ovalbumin and glutathione. The promotion of gel formation with glutathione and ovalbumin seemed to result from the interaction between sulfhydryl groups in glutathione and ovalbumin and intramolecular disulfide bonds in the serum protein, thereby resulting in the highly organized matrix.
We measured the contents of anti-tumor polysaccharides in certain mushrooms using the two kinds of antibodies that specifically recognize lentinan and GGF, which were isolated from Lentinus edodes and Grifola frondosa, respectively, as β-glucans of these polysaccharides. To determine which mushrooms showed immunomodulating activity, the TNF-α and NO productions of mouse peritoneal macrophages and the subset analysis of splenic lymphocytes stimulated with a polysaccharide from each mushroom were examined. It was ascertained that polysaccharides from mushrooms that enhanced NO production also elicited TNF-α production and that mushrooms containing the positive polysaccharides to anti-lentinan and anti-GGF antibodies at least augmented the production of TNF-α and NO. Furthermore, the polysaccharides from Fammulina velutipes and Meripilus giganteu increased lymphocyte T cell subsets. Therefore, we demonstrated that those polysaccharides had high levels of immunomodulating activity.
Heat stable ovomucoid (OM) is a major allergenic protein of chicken eggs, which are widely used in wheat flour processed food. PBS soluble OM remained in the cookies prepared by the usual method. A procedure for insolubilizing OM in batter was designed for cookies supplemented with egg white. Immunoblotting and ELISA competitive inhibition using rabbit anti-OM serum were used to analyze soluble OM in the cookies. PBS soluble OM remained both in the batter and the dough as observed in control egg white solution. Soluble OM in the cookies made from batter baked at 180°C for 8 min decreased to about one-tenth of the batter, while it decreased to almost nothing in bread made from dough baked at 180°C for 8 min. When the batter was mixed for 15 min before baking at 180°C for 12 min, PBS soluble OM disappeared in the cookies as in bread. OM in the cookies was soluble with SDS2-ME solution, but with neither the PBS nor SDS solution. This suggests that a disulfide exchange reaction between OM and wheat components is induced in the cookies. Both mixing and baking time of batter played an important role in the elimination of PBS soluble OM in the cookies. This simple method is useful for insolubilization of OM in processed foods made from batter supplemented with egg white.
The volatile components of Tosa-buntan (Citrus grandis Osbeck forma Tosa) cold-pressed peel oil were studied by GC and GC-MS. The characteristic aroma compounds were investigated by GC-olfactometry in which a semi-bore capillary column, DB-Wax, was used for effective separation of the volatile components of the oil. Hydrocarbons including mono and sesquiterpenes of the oil accounted for about 98% of the volatile components. The characteristic flavor was also present in the oxygenated fraction. Flavor dilution (FD) factors of the volatile flavor components of the cold-pressed oil were determined by aroma extraction dilution analysis. The relative flavor activity derived from FD-factor and peak area percent was used in this experiment. It was suggested that compounds with higher relative flavor activity such as decanoic acid, heptyl acetate, a-bisabolol, nonanal, cis, trans-farnesol, trans-nerolidol and 2-dodecenal would contribute to Tosa-buntan flavor. Careful sniff testing revealed 2-dodecenal to be a characteristic or key compound of Tosa-buntan aroma. A solution of this authentic compound below 2 ppm gave a pleasant and refreshing aroma similar to Tosa-buntan flavor.
12GP2 and 14GP2, synthetic cationic amphiphiles, were examined in Sprague-Dawley rats for their adjuvant activity with ovalbumin (OVA) as antigen. Findings were compared with the activity of complete Freund’s adjuvant (CFA) and aluminum hydroxide (Alum). Both amphiphiles induced OVA specific IgG comparable to the conventional adjuvants CFA or Alum, and total IgG levels of 12GP2 and 14GP2 groups were lower than the levels of other conventional adjuvants or with no adjuvant. Induction of OVA specific IgA and IgM were not observed. Examination of the effect of these adjuvants on T cell population of spleen lymphocytes showed that. CD4+/CD8+ ratio, CD4+ populations and CD8+ populations in rats immunized with the four adjuvants differed. Therefore, these adjuvants have different mechanisms for exerting immunoadjuvant activities.
The lysozyme-dextran complex (LDC) was prepared in the liquid state using high pressure treatment. This method was able to shorten the reaction period for the preparation of LDC and to suppress the formation of melanoidin, although the production rate of LDC was decreased. The maximum production rate of LDC was attained by 20 experiments using the random-centroid optimization (RCO) method. The optimum condition for the preparation of LDC was pH 4.5, 0.1 M NaCl, 192 MPa, 19.3°C and the treatment time was 88 min, under which one-tenth of the lysozyme formed the complex. Optimization by the RCO method was successful in this study, and is reasonably expected to be a practical and powerful tool in various research fields.
In general, Saccharomyces cerevisiae is a main microorganism in beer brewing, because this microbe has potent ability to produce alcohol dehydrogenase. Recently, we discovered that some genera of mushroom produce alcohol de-hydrogenase, and made a beer-like drink using a mushroom in place of S. cerevisiae. The highest alcohol concentration in this drink was achieved with Tricholoma matsutake (1069 mM, 4.6%). This beer-like drink contained about 0.17% ß-D-glucan, which is known to have preventive effects against cancer. The drink showed thrombosis preventing activity: prolonged thrombin clotting time 2.3 fold that of control. Thus, the beer-like drink made using mushroom seems to be a healthful alcoholic beverage.
Dehydrated nystose was prepared by thermal dehydration of nystose trihydrate, recrystallized from a commercially available syrup of fructooligosaccharides. Dehydrated nystose was found to have the ability to absorb moisture and the ability to maintain water activity (Aw) at a low level during its rehydration. These characteristics remained evident until an 8% (w/w) increase in weight had occurred, corresponding to the restoration of three molecules of crystallization water. As an application of these characteristics, we found that by addition of dehydrated nystose to sucrose powder the Aw is reduced to an appropriate value and the survival of lyophilized Bifidobacterium in the mixture is thereby maintained.
The purification method was improved and ADH-1 from skipjack liver was purified and characterized. This enzyme was a tetramer with subunit molecular weight of 33 kDa and distinct from mammalian ADHs. This enzyme was a SH-enzyme that was inhibited by SH-blocking reagents and had a higher affinity for butanol and ethanol, but a lower affinity for hexanol and propionaldehyde. Km value of alcohols did not decrease with an increase in the chain length of alcohol as true in mammals. The isozymes were present in skipjack liver as well as mammals and grass carp. However, it was suggested that another type of enzyme may exist in skipjack liver from that in grass carp liver.
The suppressive effects of the extract from sake cake on the SOS response of Salmonella typhimurium TA 1535/pSK1002 induced by AF-2, 4NQO, Trp-P-1, Trp-P-2, IQ and MeIQx were investigated for the purpose of finding antimutagenic substances in sake cake. The water-extract and methanol-extract from sake cake strongly suppressed SOS response induced by IQ in the presence of S9 mix in a dose dependent manner. The molecular weight of a suppressive compound in the water-extract was less than 3000 in an analysis of gel filtration. Several suppressive compounds also seemed to exist in the methanol-extract from sake cake.
The essential oil in the peel and pulp of a popular green Thai mango, Khieo Sawoei cultivar (Mangifera indica L.) has been characterized by means of the odor thresholds. γ-Terpinene, (E)-β-ocimene, (E)-2-hexenal, hexanal, and (Z)-3-hexen-1-ol were the major components. These major components differed from those of African mangoes, Florida mangoes, Indian mangoes and yellow Thai mangoes. The volatile oils from the pulp and the peel showed a high similarity of the volatile components in both sites. Odor unit values (Uo) of volatile components in both parts let us find out the aroma potent components in the Khieo Sawoei mango. Thus, nine compounds: hexanal (Uo189) and (E)-2-hexenal (Uo132) in the pulp showed higher Uo values (more than 1), while sixteen compounds: 2,4-decadienal (Uo279), (E)-2-decenal (Uo132), γ-terpinene (Uo125), (E)-β-ocimene (Uo119), (E)-2-hexenal (Uo116), and hexanal (Uo115) showed higher Uo values in the peel. Odor spectrum values calculated by these odor unit values characterized the aroma quality of Khieo Sawoei mango.
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