Differences in recognition of physical properties of food in food science and engineering and the influence of water on them were discussed. The physical properties, “Bussei” in Japanese, can be usually defined in food engineering and physics as “the physical quantities that characterize a substance and do not depend on the shape and size of the material.” There seem, however, to be other interpretations of the physical properties among food researchers and technologists. For example, some researchers such as food chemists and cooking scientists refer to the dynamic properties and the texture of foods as the “Bussei; ” whereas others such as technologists in food companies refer to it as the physical characteristics of foods reflecting some physical phenomena in food manufacturing and preservation processes. Most of the latter two types of “Bussei” are influenced by the size and shape of materials and are not, therefore, the true physical properties. The type of “Bussei” useful for food researchers and engineers would, however, vary depending on the situation or problem to be solved. Physical properties of foods are used for several purposes: first, they are indispensable parameters in the engineering models for predicting the optimal conditions for food manufacturing; second, the inner structure or state of food materials can be estimated from the behaviors of some of their physical properties. For example, water interacts with many food components; and thus the amount and/or state of water considerably influences the physical properties of foods, for example, by causing a change in the dynamic properties during sol-gel transition and the glass-rubber transition by the plasticizing effect of water.
Bamboo powder (particle size 0.2 mm) and three cube-shaped woods (1mm, 2mm and 3mm) were carbonized in the superheated steam (SHS) combined with far infrared heating (FIH), and the effect of sample size on carbonization rate was investigated. Carbonization temperature was adjusted at 270, 280, 290, and 300°C by regulating the SHS temperature at 180°C with the FIH temperatures at 375, 400, 425, and 450°C . Carbonization energies for the combined treatment were also compared with those for the carbonization treatment in SHS alone at 255, 265, 275, and 285°C . The generation rate of the SHS was the same for both carbonization treatments. The carbonization rate of each sample obeyed a first order reaction rate equation. Average values of the activation energy for the combined treatment of SHS with FIB and for the treatment in SHS alone were 137 kJ/mol and 149 kJ/mol, respectively. These values were almost the same as the activation energies for thermal decomposition of starch and cellulose under nitrogen gas. The relationship between the logarithmic values of the sample sizes and those of the carbonization rate constants was expressed as a linear curve at each carbonization temperature. Compared with the carbonization in the SHS alone, the combine treatment of SHS and FIB was much easier to make the carbonization apparatus in high carbonization temperature conditions with small additional heat. The higher the FIB temperature, the smaller the carbonization energy was obtained, because of shortening the carbonization time significantly.
The antibiotic activity produced in the co-cultures of Rhizopus peka P8 and Bacillus subtilis IF03335 (inhibition zone of 25 mm) was higher than that in each of the pure cultures (inhibition zones of 0-15 mm) . Both the concentration of B. subtilis and its mixing time with R. peka influenced the antibiotic production. The optimum condition was when the culture was inoculated at the same time with equal numbers of viable B. subtilis cells and R. peka spores. When the cell free culture broth of one was mixed with either the cell free culture broth or the cell free extract of the other and incubated at 30°C for 18 h, the antibiotic activity in the mixture was higher than that in the individual culture broth or cell extract. There was no antibiotic activity in a mixture that was not incubated at 30°C. Furthermore, the antibiotic activity was lost when either the cell free culture broth or the cell free extract was heat-treated (121°C, 20 min), indicating the involvement of an enzyme from B. subtilis in producing the active antibiotic from R. peka. Thus, the presence of B. subtilis in the culture effectively influences the production of the antibiotic from R. peka.
This paper describes the elution behavior of metals during hydrothermal decomposition of rice hulls at 200°C using a percolation type reactor. Through that treatment, the rice hulls were converted to solubilized products at 45.9wt% yield. The solubilized products were mainly arabinose, xylose, and xylooligosaccharides derived from hemicellulose. While, cellulose was not decomposed in this treatment. Results showed that the elution behavior of metals with hydrothermal treatment is classifiable into two patterns. First, alkali metals, phosphorus, boron, and aluminum elution did not depend upon the temperature, but rather on the treatment time. On the other hand, elution of heavy metals, alkaline earth metals, and arsenic depends upon temperature. That is to say, raising the purity of organic matter might be possible by lengthening the time of the 1st fraction and inducing full elution to obtain high-quality organic matter with few metals in the 4th and the 5th fraction.
Solubilization and saccharization of barely straw by hot-compressed water (HCW) treatment were carried out aiming at effective use of agricultural waste. Hemicellulose (arabinoxylan) was mainly hydrolyzied to arabinose, xylose and xylooligosaccarides at the temperature range of 160-220°C. However, cellulose was not hydrolyzed in this range. As a result, cumulative yields of solubllzzed products were less than 55 % . While, the cumulative yields of solubilized products exceeded 55wt % at the temperature range of 240-280°C. Particularly, the yield reached 95% at 280°C. This figure reflects that inorganic component, mainly silica, was also solubilized. In these conditions, glucose and cellooligosacharides were thought to be derived from cellulose as well as hemicellulose. It was suggested the HCW was found to be useful for solubilization and saccharization of barely straw. The products obtained were thought to be able used as feedstock for chemicals and ethanol-fermentation.