The aim of this study is to investigate the thermal stress resistance properties of Escherichia coli (E. coli) to construct the optimized sterilization method for the soybean based foods. The samples of E. coli incubated on the soybean extract added LB medium (test sample) and normal LB medium (control sample) were subjected to high temperature stress of 60℃.Soybean extract which is mainly consisted of protein, lipid and water was prepared to add the LB medium. Under high-temperature condition, the survival behaviors of E. coli inoculated by the control and test sample were indicated by the first-order kinetics. And the thermal resistance of E. coli was significantly enhanced by a soybean extract. Moreover the top, middle and bottom part of soybean extract were prepared by the additional centrifugation of soybean extract. Each part is characterized by lipid, phospholipid, and protein, respectively. The thermal resistance of middle part showed the quite similar behavior to that of whole soybean extract. However, those of top and bottom parts were obviously decreased faster than that of middle part. And a significantly increase of the weight of phospholipid in a cell incubated with the middle part was observed comparing with that of control sample. It is therefore very likely that the thermal resistance of E. coli is enhanced by the effect of phospholipid in soybean extract. Furthermore, under the high pressure stress of 150 and 200 MPa, the survival curve of middle part was obviously slower decrease than control sample. Consequently, results obtained in this paper, are successfully revealed that the addition of phospholipid in soybean extract is strengthened the cell membrane or surface structure of E.coli.
Size-controlled preparation of agar gel microbeads using monodisperse water-in-oil (W/O) emulsion was investigated. W/O emulsions were prepared by microchannel (MC) emulsification using three grooved MC plates with different geometries of the MC region. The addition of sodium chloride to the dispersed phase was necessary for stable preparation of monodisperse agar-containing W/O emulsions. The mean droplet size varied from 15 to 34μm depending on MC geometry, while the coefficient of variation was below 10%. Monodisperse agar gel microbeads were obtained by cooling the emulsion droplets prepared at a temperature higher than the gel point of the agar solution. Emulsification conditions (e.g., agar concentration and emulsification temperature) affected droplet diameter and uniformity of the W/O emulsions. Monodisperse and quasi-monodisperse W/O emulsions could be prepared at agar concentrations of 0.5 to 2.0 wt% and at emulsification temperatures of 40 to 50℃, which exceeded the gel point of the agar solution. At temperatures below the gel point, MCs were partly clogged by the to-be-dispersed agar solution, due to partial gelation of the agar solution. However, above 50℃, emulsification was destabilized because of immediate coalescence of droplets formed once downstream of MCs.
In this study, a novel process for efficiently separating and purifying tocotrienols from deodorizer distillate from rice bran oil were developed by combining adsorption and desorption with ion-exchange resins and a simulated moving bed chromatography (SMB). In the vitamin E rich fraction obtained by adsorption and desorption with ion-exchange resins, only free fatty acid was detected as an impurity. The recovery ratios of tocotrienols and tocopherols were 73％ and 100％, respectively and the mass fractions of tocotrienols and tocopherols were 21 wt％ and 42 wt％, respectively. Those results were two times higher than those obtained by the conventional molecular distillation. Next, the purification of tocotrienols by SMB was performed using the vitamin E rich fractions obtained with ion-exchange resins and the conventional molecular distillation. The separation efficiency was improved by 20％ and the required volume of eluent was reduced by 25％ using the vitamin E rich fraction with ion-exchange resin. Thus, the proposed process was very effective to separating and purifying tocotrienols and can reduce the environmental impacts and production cost.
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