Water is an overwhelmingly major component in food so that the freezing behavior is very important in food processing. Effective thermal conductivity of frozen food is strongly dependent on temperature and is described well by the Maxwell-Eucken model with ice phase dispersed. Ice crystal structure size in frozen food is inversely proportional to the advance rate of ice front, reflecting the important role of the molecular diffusion of water in the process of ice crystal growth. In the freezing preservation of living cells, the water permeability in the plasma membrane seriously affects freezing tolerance of cells. Plant cells, in general, have much lower water permeability in the membrane as compared with animal and microbial cells so that the membrane structure of plant cells is easily destroyed by freezing. This lower freezing tolerance of plant cells is applicable to the waste treatment of kitchen refuses such as vegetables and fruits. 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.
An advanced oven system, which generates superheated steam containing micro-droplets of hot water (Aqua-gas) by spraying heated water into its heating chamber, has been developed. It was expected that the micro-droplets made the heat transfer coefficient of the heating medium larger and they prevented deteriorations of foods due to drying during the heating process. The heat transfer coefficients of the Aqua-gas, superheated steam and hot air maintained at 115°C were measured changing a surface temperature of a heat flowmeter. Specific differences in the dependency of the heat transfer coefficients on the temperature at the heat transfer boundary have been found between each heating medium. Drying rate of a model food sample in each heating medium has been examined also. The drying rate of the sample in the Aqua-gas was lower, and it was shown that the micro-droplets in the Aqua-gas prevented the desiccation of the food sample. In addition, the micro-droplets in the Aqua-gas were recorded by a high speed camera. The micro-droplets were observed in the Aqua-gas, and it was supported that the micro-droplets efficiently enlarged the heat transfer coefficient of the heating medium and they prevented the drying of the food sample.
A wetted starch ball as a model sample was treated in high temperature gases over a wide range of humidity, using hot air, humid air and superheated steam. The effect of gas humidity on the drying process and product condition was investigated by continuous measurement of the material core temperature and weight changes during treatment. From experimental results, the sample kept its shape during treatment in low humidity gas. Whereas, in the case of high humidity air, the sample burst accompanied both by temperature and mass drops during the treatment. In superheated steam, the sample puffed near the surface. The gas conditions are shown on the steam partial pressure-gas temperature chart, and it shows the important values of dew point temperature as determined by simple estimation technique using wet-bulb temperature and gas temperature. With this chart, we can see that the relationships of initial sample temperature, boiling point, dew point, wet-bulb, dry-bulb and gelatinizing temperatures for food processing of starches are important in order to achieve the desired results.
Considerable attention has been paid to the bio-treatment of lipid-rich wastewater discharged from the kitchens of many kinds of restaurants, but it is still technologically undeveloped in terms of lipid-degrading microorganisms' abilities, cost performance and wastewater treatment system, etc. In this study, for developing the practical system of bio-treatment of such a lipid-rich wastewater, we isolated bacteria capable of strongly assimilating lipids (salad oil, lard, beef tallow, and olive oil) from soil samples. The bacterium, strain AIK, with the highest lipid degradation ability was identified as Burkholdia cepacia and also confirmed to be a non-pathogenic and safe bacterium based on animal tests and so on. The CSL medium containing 3% CSL (corn steep liquor) and 1% glycerol was favorable and effective for the growth of the bacterium and its lipid-degrading activity. Fieldworks at drainage facilities of practical fast food restaurants were successfully done by using the strain AIK and our developed system with the water pump which is instantly applicable to existing facilities and is reasonable in terms of cost. As an example of it, we report here a representative example of a fast food restaurant showing that lipid concentration was rapidly decreased from 1100mg/L to 100mg/L.
Although a phase transition such as crystallization for food related lipid would play an important role on the stability or various properties of food, there are many unclear issues. Especially, the researches about the phase transition on multi component system including lipid are few. As well as, the knowledge for the phase behavior of their emulsion is limited. In this work, the effect of the composition on the crystallization temperature Tc, i.e. nucleation, and the melting temperatures Tm, for the binary systems, triglyceride binary system and hydrocarbon binary system, was investigated. It was found that both of the crystallization and melting temperature depress logarithmically with the ratio of its composition. Also, there was a linear relationship between the Tc and Tm. These behaviors could be observed not only for the bulky state, but also for the oil-in-water emulsified state. However, it should be noted that, although the Tm for emulsified and bulky lipids gave the same value, the Tc for emulsified lipid exhibited remarkable lower temperature than that for bulky lipid. It is thought that these findings give a kind of quantitative method to understand the physicochemical properties for food related lipid.
New potential application of kitchen refuse, succinic acid fermentation by Actinobacillus succinogenes ATCC 55618 to produce raw material of poly (butylene succinate) (PBS) was studied in this work. Preparation of kitchen refuse as media for succinic acid fermentation by A. succinogenes has been established. Succinic acid production and growth of A. succinogenes using kitchen refuse as substrate were significantly affected by additional nitrogen source and external gas composition The optimal kitchen refuse medium for maximal succinic acid production was 4% (w/v) glucose and 0.2% (w/v) yeast extract, biotin which support enzyme (Phosphoenolpyruvate carboxykinase) reaction in succinic acid fermentation was not essential. At optimal media and external CO2 supply, the highest succinic acid production was 68.3±0.7% (w/w) (based on glucose consumption) in flask reaction size with shaking rate of 65 rpm at 39°C, after 48 h. Succinic acid production with 68.5% (w/w) and 30.4 g/L of final concentration, resulted in productivity with 0.6 g/L/h were obtained when conducted in 1-L of bioreactor (Under controlled pH at 6.5 by 5 M NaOH, agitation speed of 100 rpm, a CO2 gas sparge rate of 1.0 vvm and at 39°C) . Kitchen refuse utilization for succinic acid by A. succinogenes suggested a promising practical way to produce substrate for biodegradable plastic synthesis.
Though many kinds of machineries are needed for the automated food processing, the designing method for food machineries is not well developed. This is due to the complexity of the heat transfer characteristics in foodstuff, and the stir-frying process is the most complicated one that includes simultaneous heat and material transfer. In this article, heat transfer mechanism in stir-frying process is studied in detail. Temperature distribution in static bulk of sprouts is measured and the obtained data reveal the fact that the temperature hardly rise in the pieces that do not touch the heating surface. This fact notice us the stirring operation has an extremely important roll even in heat transfer since it substitute the thermal diffusion by its material dispersion. On the basis of these disclosures, thermal characteristics of a static bulk is estimated by introducing 2 parameters; one-layer thickness and fraction of contacting pieces. In addition, thermal diffusion due to stirring operation is modeled by introducing the parameter named stirring frequency. These enabled to establish the calculation method that can predict the temperature rise in stir-fried bulk. From one of calculation results, heat transfer coefficient between bulk and heating surface is estimated as 155 W/m2K.
A salting-out precipitation of sodium succinate was investigated by adding various predetermined amount of methanol or ethanol as an antisolvent to model solutions containing 5-25wt% of the sodium succinate and sodium succinate solutions (KRFBs) which are concentrated from kitchen-refuse fermentation broth. In case of KRFBs, the powder recovered was refined by sequential purifications with 1.5 and 2.0 mass ratio of ethanol/water (EtOH/H2O), respectively. Sodium succinate purity and impurities such as sodium salts of by-product organic acids, sugar, and protein in the powder derived from each step are evaluated. Ethanol as an antisolvent shows higher and more stable succinate recovery rate than methanol in both model solution and KRFBs. Over 95% of succinate recovery rate was obtained from each KRFB at more than 1.5 EtOH/H2O mass ratios. A protein, a major impurity after a recovery step, was dramatically removed by the first purification. Sodium salts of by-product organic acids almost remained in EtOH/H2O solution and were not detected in the powder after purification steps. More than 96wt% of sodium succinate purities were achieved from individual KRFB by salting-out precipitation using antisolvent, ethanol.
The discoloration of L-ascorbic acid (vitamin C) powders with a water content of 1 to 10% (w/w) during storage at a temperature of 60 to 90°C was investigated by monitoring the absorbance of L -ascorbic acid solutions at 360, 450 and 500 nm. The discoloration reaction of the L-ascorbic acid powders was expressed by the modified Weibull equation under any condition. The rate constant, the shape constant and the maximum absorbance were estimated based on the equation. The temperature dependence of the rate constant was expressed by the Arrhenius equation under every storage condition, and the values of the activation energy and frequency factor increased with the increase in the water content. Although the shape constant depended on the wavelength at which the discoloration was observed, it was independent of the temperature. The maximum absorbance at every wavelength was expressed as functions of the water content of L-ascorbic acid powders and the storage temperature. These results enable us to estimate the discoloration of L-ascorbic acid powders under any condition, while the water content and the temperature would be limited in the ranges of 0 to 10% (w/w) and 60 to 90°C, respectively.
Solubilization of hemicellulose (xylan) by Hot-compressed-water (HCW) followed by enzymatic saccharification was performed to obtain xylobiose and xylotriose in high yield. 32.9wt% of the chinquapin was converted to solubilized products by HCW treatment using percolator type reactor at about 200°C. The obtained solubilized products could be easily changed to xylobiose and xylotriose by enzymatic saccharification. The maximum yield of xylobiose was 35.6wt% (dry hemicellulose base) and that of xylotriose was 21.3wt% (dry hemicellulose base) .
After a high-fat diets (with a fat content of 40 g), 3.0 g of mannooligosaccharides from coffee mannan (MOS) was administered to subjects, the change over time of the triglyceride concentration in the blood serum was examined. The concentration of triglycerides in the blood serum showed a rapid rise right after the consumption of the diets, for both the MOS and placebo groups, and peaked between 120 to 180 minutes after consumption. The MOS group, in comparison with the placebo group, showed a trend towards a reduced concentration of triglycerides from 120 to 300 minutes after consumption, with a significantly lower concentration at 180 minutes after consumption (p<0.05) . The results suggested that the intake of MOS was a factor in inhibiting lipid absorption.
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