Recently we developed a new logistic model for prediction of microbial growth in foods. The model is an extended logistic model for expression of microbial growth which shows a sigmoid curve on the semi-log plot. The model could describe and predict bacterial growth at constant and dynamic temperatures in broth, on nutrient agar plate, and in pouched food. Prediction with our model was very similar to that with the Baranyi model, which is well known worldwide. The model also predicted the amount of a metabolite (toxin) by a microorganism. Namely, with the growth model and the kinetics of staphylococcal enterotoxin A production, the amount of the toxin produced by Staphylococcus aureus in milk was successfully predicted. Further, a predictive growth program running on a personal computer was developed with our model for users dealing with food safety. Our model can be a tool in the alert system and the risk assessment for microbial food safety.
The low caffeine processing machine that we developed to have infants, a pregnant woman, and a senior citizen drink ‘Benifuuki’ green tea was able to decrease a caffeine content more than 50% without reducing anti-allergic epigallocatechin-3-O- (3-O-methyl) gallate (EGCG3 Me) content by processing to spray a heated water shower of 95 degrees Celsius on plucked new tea shoots more than 90 seconds. We installed this processing machine before primary tea rolling dryer at a normal processed tea production line, and put plucked new shoot slit in processing machine while adjusting tea leaf to equal thickness and atomized water of normal temperature and cooled off after having sprayed heated water showers more than 95 degrees Celsius while transferring tea leaves with a net conveyer. About 1.8 times establishment areas are necessary in comparison with conventional rotary net drum tea steaming machine (800K) . Quantity of circulation heated water which it is necessary is about 360, 00 L/hr, and include water injection and a rise and a loss share of green leaf temperature, and the heat capacity that it is necessary is approximately 350, 000 kcal/hr. In addition, by this processing, anti-allergic activity of ‘Benifuuki’ green tea did not reduce.
Endothelin-1 (ET-1), a powerful vasoconstrictor and mitogen for melanocytes, might be the underlying cause of pigmentation following ultraviolet (UVB) irradiation. Six botanical extracts were examined for their inhibitory effects on ET-1 secretion in porcine aortic endothelial cells. We observed that the extract of Sechium edule fruit reduces ET-1 secretion in human keratinocytes following UVB irradiation. Therefore, the extract of S. edule fruit may be useful as a whitening agent for the skin.
High Electric Field AC (HEF-AC) is an instantaneous microbial inactivating treatment based on two electrical effects: own-generated Joule heat by electric current flowed into food, and cell membrane injuries caused by applied electric field. In this study, we applied three types of heat-resistant microorganisms: mesophilic-, thermophilic-, and acidophilic organisms, to a device of continuous pressurized HEF-AC. We examined the effect of treatment condition for inactivation against B. subtilis spore. The inactivation effect was improved in proportion to the temperature above 113°C as onset inactivation temperature of B. subtilis. We take D-value as the rise in temperature with decrease the number of bacteria to one tenth. Triple intensity of electric field effected a reduction of D-value and a logarithmic order inactivation at 115°C. On the other hand, Triple electric current had little effect on inactivation. In the comparison with D-value between HEF-AC and UHT, the D-value through the use of HEF-AC was smaller than that of UHT: the inactivation effect through the use of HEF-AC was higher than that of UHT. Double intensity of electric field effected a reduction of D-values and an increase of inactivation of other 4 species of heat resistant microorganisms. It was found that the higher D-value of microorganism spores could be effectively improved the inactivation effect by applying higher electric field. It was found that each microorganism' s onset inactivation temperature through the use of HEF-AC was increased in proportion to logarithm of F-value as an index of heat-resisting properties of the microorganism.
A starchy food that is initially a single-phase body turns into a multiphase body during boiling because of starch gelatinization. Fick's law is applicable only to a homogeneous system and is not applicable to such a multiphase system. Relative Water Content (RWC) model has been proposed as an alternative model that is able to describe water migration in multiphase food systems. In the RWC model, water migration is driven by the gradient of water content divided by the water holding capacity (WI-IC), m/m*. In this study a WHC profile (WHC plotted against water content with which starchy food is heat-treated) was assumed based on information concerning starch gelatinization. Using this WHC profile, the correlation between WHC profile and transient water content profile in a wheat flour dough slab during boiling was examined. A modified WHC profile was found to be applicable for describing certain characteristic features of the transient water content profile in a slab of wheat flour dough during boiling.
The inactivation of Escherichia coli K-12 by pulsed electric field was investigated using textile electrode with combination of polyester fiber and titanium wire. Inactivation effect was depended on the applied voltage, wire gap length of textile electrode, solution conductivity, electrode surface area, and liquid flow rate. The survival ratios of E. coli K-12 decreased with an increase of applied voltage. The Inactivation effect was greatly influenced with solution conductivity, and higher efficiency of PEF was achieved when the solution conductivity was 0.22 mS/cm, but wire diameter did not affect to the inactivation. As the gap length of electrode was becoming narrow, the wire density of textile electrode was higher, the sufficient effect on sterilization of E. coli K-12 was observed. The survival ratio reduction was depended on the liquid flow rate, and the sterilization efficiency with number of recirculation was higher at the liquid flow rate 40 mL/min than at 160 mL/min.
In this study, rice noodles were made from a mixture of gelatinized dough and raw dough by using 6 varieties rice flours with different amylose content produced in Japan and China. Correlations between the physicochemical properties of rice flours and physical properties of cooked noodles as well as the correlations between the physical properties of cooked noodles and sensory evaluations were determined. Furthermore, the rice noodle qualities are discussed. Results showed that the amylose content was the main factor affecting the physical properties of cooked rice noodles. Amylose content was positively correlated to the maximum tensile stress, apparent elasticity and storage modulus of rice noodles, but negatively correlated to the loss tangent. Furthermore, all the rheological properties of rice noodles were significantly correlated to the setback of pasting properties obtained by RVA. The setback appears to be the main parameter for evaluating the physical properties of the rice noodles. The results of sensory evaluation of the rice noodles showed that the total score was positively correlated to the maximum tensile stress, maximum tensile strain, apparent elasticity and storage modulus of rice noodles, but negatively correlated to the loss tangent. The Yumetoiro variety form Japan and the Zhongzao22hao variety form China showed higher scores in sensory evaluation for producing rice noodles than the other varieties.
A new method using a non-rotational concentric cylinder (NRCC) rheometer was used to determine the viscoelasticities of selected viscous liquid foods. The results were compared with those of conventional dynamic viscoelastic measurements. Two two-element models, the Maxwell model and the Voigt model, were used to describe the viscoelastic behavior of model foods measured by the NRCC method, which generates force-time curves. Mayonnaises with 28-36 w/w% water content and the 4 w/w% gelatinized potato starch exhibited Maxwell behavior with convex force-time curves. In contrast, mayonnaises with 20-24 w/w% water content and 5-7 w/w% gelatinized potato starches exhibited Voigt behavior with straight force-time curves. These results were in good agreement with the results given by the dynamic viscoelastic method. The G' value of the Maxwell model-like samples showed frequency dependence, while the G' values of the Voigt model-like samples exhibited less pronounced frequency dependence over the observed range.
This research examined cationic ion participation with flocculation and sedimentation phenomena by the enzyme addition of solid particles derived from rice washing drainage and the electrochemical properties of the solid particle surface. Solid particle removal characteristics by the addition of flocculation and sedimentation ability were also examined. As a result, a solid particle of the supernatant after enzyme treatments and sedimentation obtained by the addition of protease M showed minimum value in all parameters such as mean value, etc. of the particle diameter compared with other enzyme additions. Moreover, to specify the negatively charged functional group using FT-IR analysis, the adsorption increases of hydroxyl (-OH) group was confirmed by protease M treatment. It was thought that the negative electron charges of hydroxyl (-OH) origin in the solid particle surface increased by protease M treatment and decreased the capacity of sludge volume (SV) value. In addition, from the results of the effect of chelate agent additions for sludge volume, flocculation and sedimentation of solid particles deeply depended on cationic ion of solid particle origin. These results suggest the occurrence of flocculation and the sedimentation of solid particles by the addition of protease M as a result of the formation of negative electron charges in solid particle surface and cationic ion discharges from solid particles were promoted by enzyme addition, respectively. Finally, macromolecule was formed by constructing a bridge by electrostatic interaction.
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