The application of glass transition in the field of Food Science & Technology was reviewed. As examples of research investigating the relationship between physical and chemical properties of food and glass transition, glass transition of Katsuobusi (boiled and dried bonito fish stick) and stability of frozen food quality during storage was described in detail. In addition, the relation between water diffusion coefficient in freeze-concentrated matrix and recrystallization rate of ice crystals in several sugar solutions was also explained in terms of molecular mobility. The Katsuobushi in the market showed glass transition behavior. Also, it was reported that specific shaving energy of the rubber Katsuobushi was less than that of the glassy one. In the researches of stability of frozen food quality during storage, the enzymatic reactions in frozen tuna meat and recrystallization of ice crystals in sucrose solution were greatly suppressed if their freeze-concentrated matrixes were in glassy state. This fact indicates that utilization of frozen storage temperature lower than glass transition temperature has a potential of effective and long-term excellent storage stability of frozen foods. The recrystallization rate of ice crystals in several sugar solutions increased with increasing the diffusion coefficient of water molecules in freeze-concentrated matrix. From this result, it was suggested that mobility of water component in freeze-concentrated matrix is an important factors controlling recrystallization rate in sugar solution relevant to frozen dessert.
The oxidation kinetics of unsaturated lipids was examined in bulk, emulsion and micelle systems, and the related literature was also summarized. A kinetic equation of the autocatalytic type was applicable for the lipid oxidation in all these systems. The oxidation of a lipid is affected by many factors. In a dispersion system, such as an emulsion and micelle, the size of the dispersion phase is one of these factors. In spite of a higher specific surface area, the lipid was more slowly oxidized in both the emulsion and micelle systems containing smaller particles in the dispersion phase. This fact could be explained by dilution of the substrate by the hydrophobic moiety of a surfactant for both systems.
The flow conditions of a new dryer for by-product of tofu proposed in the previous paper are examined. Its drying capacity is relatively small and to know the internal flow is necessary to develop larger capacity machines. Firstly, the interior of drying drum and classifying chamber were observed using high speed video. Wet materials returning from upper chamber are colliding with the materials and ceramic balls moving along the surface of the drying drum entrained in the hot air and dispersed. In the classifying chamber counterclockwise circulating flows are formed. Then numerical simulation was carried out for the flow of this dryer using FLUENT. Necessary nodes were about 800,000 to describe the whole machine. Obtained path lines are almost consistent with the video images showing the validity of the simulation method. To get the suitable geometry for 5 times larger machine, flow conditions were compared for three types of geometry of the entrance to classifying chamber and the best geometry was determined. The chamber height was then determined so that the velocities at the ceiling are below 3 m/s to avoid adhesion of the wet materials to the wall. Based on the obtained results 300 kg/h machine was build and it was successfully operated.
The inactivation of Escherichia coli K-12 was investigated in a system using a pulsed electric field (PEF) and a spiral silver wire electrode. The survival ratios of E. coli K-12 decreased with increasing voltage. The sterilization effect was greater with a high-voltage silver wire electrode than with a stainless steel electrode. This result was attributed to the enhancement of PEF inactivation by the lethal effect of silver. The PEF inactivation effect with electrochemically eluted silver was higher than that with silver nitrate solution, though the silver concentrations were almost the same. These results suggest that simultaneous treatment of E. coli cells with PEF inactivation and silver electrochemical elution improves inactivation efficiency.
It is said that a cause of sudden rise in price of foods is partly due to the production of bio-ethanol from biomass of foods origin. If an arable land is newly obtained by clearing such as forest etc. to prevent this social issue, it causes reverse effect to original purposes to reduce carbon dioxide emission. These difficulties are assessed at for the two cases of productions of bio-ethanol using existing arable land and newly cleared land under the available statistical data and a simple model introduced. Even if the bio-ethanol production is conducted using entire cereals produced per year in the world, the product substitutes only about 43% of gasoline consumed because human beings consume enormous amount of gasoline per year. In the case of Japan, it is only 5.5%. This suggests the sudden rise of food price is inevitable. If the bio-ethanol is produced using newly cleared land, it is concluded that the effect on reduction in carbon dioxide emission never appear until several 10 years to a few hundred years later.
High-pressure effect on the properties of onion was investigated. The dielectric properties of high-pressure treated onion were measured at 50 Hz- 5 MHz. Radius of Cole-Cole arcs of high-pressure treated samples were smaller than untreated. Radius of treated onion completely disappeared at 400 MPa. This indicated that cell structure would be damaged by high-pressure treatment. Next influences of high-pressure treatment on functional properties were analyzed. Antioxidative activities of high-pressure treated onion at 200 or 400 MPa were increased during storage at 25℃. The constituents of high-pressure treated onion were analyzed by HPLC. Scatter plot between high-pressure treated and untreated peak area ratio (sample peak area/internal standard peak area) were analyzed. Area ratios of untreated samples were plotted on x-axis and those of high-pressure treated were on y-axis according to the retention time. The slope with the retention time of 27.3 min was over 1.0. This indicated that the slope over 1.0 was positive-affected by high-pressure treatment. The ingredient with the retention time of 27.3 min was identified as quercetin. Scatter plot was a novel tool to extract the high-pressure effected substances from multiple and unidentified data. These changes of structural and functional properties of foodstuffs are defined as “High-Pressure Induced Transformation (Hi-Pit).”
The bacteriocins produced by Lactococcuslactis subsp. lactis C101910 (C101910) and NBRC 12007 (NBRC 12007) were used to prevent the growth of Lactobacillus hilgardii, a hiochi bacterium, at the mizu-koji stage in the sake brewing process. The bacteriocins produced by C101910 and NBRC 12007 were slowly inactivated in the koji extract by proteases, depending on the pH and temperature of the koji extract. However, the activities of bacteriocins from C101910 and NBRC 12007 remained about 50% and 70% of the initial values, respectively, even after incubation at pH 3 and 10℃ for 12 h. By adding the bacteriocin solutions, prepared according to the method reported previously, from C101910 and NBRC 12007 to koji extract (pH 3 and 10℃) at a volume ratio of 5% (v/v) and 1% (v/v), respectively, the number of viable L. hilgardii cells decreased to below the detection limit (1.0×102 cells/ml) from the initial concentration (3.2×105 cells/ml) within 12 h. In mizu-koji consisting of rice koji and lactic acid solution at pH 3 and 10℃, the growth-inhibitory effect of bacteriocins from C101910 and NBRC 12007 on L. hilgardii decreased as compared with that in koji extract. However, the number of viable L. hilgardii cells decreased by more than two orders of magnitude as compared with the initial value (1.0×105 cells/ml) by adding the bacteriocin solution at a volume ratio of 10% (v/v).
The addition of the supernatant derived from enzyme (protease M) - treated rice washing drainage to purified rice starch showed highest sediment ability of starch particles. Besides, phosphate ion discharges from solid particles to the supernatant that were promoted by the addition of protease M, the decrease of the supernatant phosphate concentration after additions of purified rice starch was also observed. Moreover, to determine the dissociation of phosphate ions in relation to flocculation and sedimentation of purified rice starch, these processes were observed with the same pH range under the existing dissociate form of phosphate. In addition, as the results of FT-IR analysis of the solid surface of purified rice starch show, using the same pH the transmittance decrease of the P-O group and the flocculation and sedimentation ability of purified rice starch particles were observed. These results suggest that the occurrence of flocculation and sedimentation of purified rice starch particles as a result of pH dependent dissociate form of phosphate joins with the surface of the starch particles and form negative electron charges derived from the dissociate form of phosphate on the surface of starch particles, respectively. Finally, macromolecules of starch particles were formed by constructing bridges by electrostatic interaction.
Freezing and thawing (FT) method has been known as an effective technique for removing suspended solid (SS) from suspensions including sewage sludge. In this study, saccharification solution produced from kitchen garbage has been chosen as sample solution, and FT technique has applied to the solution for the removal of SS in the solution. After the FT application for the saccharification solution (SS: 52700 ppm), SS in the solution have been reduced to 1300 ppm. And much clearer supernatant with lower SS content was obtained when FT solution kept at static condition overnight. Consequently, keeping FT solution at static condition overnight for SS sedimentation can remove over 99% of the SS from original kitchen garbage saccharification liquor. Saccharification liquor is easily damaged due to its characteristics. It should be kept frozen till its use as raw material for fermentation. Freezing and thawing offers good option both for SS removal and storage.
Straight-through microchannel (MC) arrays consisting of numerous oblong straight-through holes are promising MC emulsification devices for producing monodisperse emulsions in large droplet-production scales. We investigated the effects of MC dimensions and velocity of a cross-flowing continuous phase on the production of soybean oil-in-water emulsions using straight-through MC arrays made of single-crystal silicon. The aspect ratio of oblong MCs with equivalent diameters of 21μm to 22μm significantly affected droplet generation and the sensitivity of droplet size to continuous-phase velocity. Uniform oil droplets with diameters of about 100μm and coefficients of variation of less than 3% were generated using large oblong MCs with equivalent diameters of 54μm to 55μm. Data analysis demonstrated that oblong MCs with aspect ratios exceeding a threshold of 3 were necessary to generate uniform oil droplets in a wide range of MC cross-sectional sizes. Moreover, the cross-flow of the continuous phase did not affect the size of the droplets generated using oblong MCs with a large aspect ratio.