The results obtained from our studies on several aspects of food pasteurization and sterilization by cross-talk between microbiology and technology were presented. First, we found that the thermal death of Escherichia coli was affected by rising temperature and pre-incubation processes and it was suggested that the phase transition and phase separation of membrane lipids were involved in these phenomena. Second, we analyzed the kinetics of bacterial death by a combined treatment of heating with antimicrobial compounds and we presented two distinct modes depending upon the type of chemicals. Third, new methods for process evaluation and prediction of pasteurization effects, including the growth-delay analysis, the cell motion analysis and the analysis with the fluorescence of green fluorescent protein variants expressed in bacterial cell were proposed. And finally, we constructed the database of thermal death of microorganisms based upon the data which have appeared in articles published in 30 major academic journals. Also, some predictive models on the thermal death of bacterial spores in a buffer and liquid foods were predicted as influenced by several factors such as pH, the sodium chloride concentration and heating temperature.
We developed the taste analyzer to answer market demands for prompt, objective rice taste evaluation. This report explains the development of the analysis equipment for the rice quality evaluation system and introduces the previously unpublished historical background behind the rice taste analyzer. It also explains the logic behind the Total Taste Evaluation System and why it was necessary to develop each piece of equipment (Cooked Rice Taste Analyzer, Fresh Degree Meter, Hardness and Stickiness Meter) that makes up the Total Taste Evaluation System. Finally, this report explains the purpose of the development of the Total Taste Evaluation System and proposes a new concept to segment rice quality according to its use, based on the results from the equipment. This will give the users of the equipment taste values that match more closely with human sensory evaluation, improving evaluation for both cooked and uncooked rice.
Technical knowledge on freeze-grinding of food was reviewed. Fracture mode (Ductile fracture and brittle fracture), temperature dependence of the fracture mode, determining procedure of brittle temperature using Charpy impact testing machine were introduced. Advantages of freeze-grinding of food and applications of freeze-ground food were explained. In freeze-grinding, the food tissue can be separated, when the phenomenon of preferential grinding is utilized. In this review, tissue separation of whole fish which combined freeze-grinding and screening was explained in detail. In addition, fracture-temperature-map was made from the absorbed energy curve of each tissue of the fish, and the method for deciding the optimum freeze-grinding temperature was introduced.
Preparation of nano/micro-dispersion systems via the self-assembly of food materials were investigated. Here, we summarized our recent results on (1) nanoparticle formation via electrostatic and hydrophobic interactions between modified lecithin and chitosan, (2) stabilization of monodisperse O/W emulsions by the addition of charged polysaccharides, and (3) formation of nanoparticles from chitosan and carboxymethylcellulose via the polyelectrolyte complexation. In each system, the preparation procedures were quite simple: two or more materials dissolved or suspended in aqueous media were just only mixed to each other without high energy input nor harmful chemicals addition. The particle size, surface charge and dispersion stability were significantly affected by the mixing ratio of the concerned materials. The results suggested that the nano/micro-dispersions having preferable properties could be designed by adjusting the mixing ratio adequately. These dispersion systems would be useful for developing novel foods having high functionality and good stability.
The homogenizer basically consists of a high-pressure plunger pump usually with triple plungers to minimize pressure fluctuations and a homogenizing valve with a narrow gap. However, the flow within the homogenizing valve is not clarified theoretically. In this paper, the influence of shape modification of the homogenizing valve was investigated in the emulsification action. The experiments using a small homogenizer are conducted. We studied the influence of the flow pattern (pressure distributions, shear stress) on the droplet size distribution obtained in the experiment, and investigated the relation between the shear flow and the emulsification action in the homogenizing valve. In this experiment, two valve types (sharp type and flat type) were applied. The pressure drop in the valve and the parallel gap part length were changed. The droplet size distribution results obtained in the emulsification tests could be analyzed based on the average value of the wall shear stress in the parallel gap part through the above experiments and calculation results.
Slightly acidic electrolyzed water, prepared by electrolyzing dilute hydrochloric acid, has a strong anti-microbial effect, and is widely used for various washing and disinfecting purposes. To obtain the desired effect, it is important to understand quantitatively how operating parameters affect available chlorine concentrations and pH in slightly acidic electrolyzed water. In this paper, the effect of the cell voltages, which was considered as one of the most important factors that controlled the electrochemical reactions, was examined. The previous model was modified to consider the existence of the leakage current and the voltage balance in the electrolysis cells. The calculated results represented well the tendency of the experimental data, which showed a remarkable increase in the current efficiency with a rise of voltages until 1.7 V. The calculated results also described the tendency of experimental data, which showed a decrease in pH with a drop of voltages. The modified model enabled us to predict the consumption rate of a hydrochloric acid in various conditions. With the model modified in this study, the operation conditions for adjusting pH, in which the addition of slightly acidic electrolyzed water to foods was permitted, were proposed in a very high or low hardness.