We examined the properties of starch, which is the main component of potatoes, separated and purified from potatoes with different specific gravity.
1) The physical properties of the starch were examined. The mean diameter of the starch granules was 41.7μm in the samples with a low specific gravity, and 50.3μm in the samples with a high specific gravity. The temperature at the start of gelatinization was 62.5°C in the samples with a low specific gravity, and 60.0°C in the samples with a high specific gravity. The maximum, minimum and final coefficients of viscosity determined by amylography were higher in the samples with a high specific gravity than in the samples with a low specific gravity. All X-ray diffraction diagrams of the samples were type B, which is a characteristic of the starch obtained from underground parts of plants.
2) The properties of amylose and amylopectin were examined. The percentage of amylose was about 22% in all the samples examined, and the molecular weight of amylose was larger than 1000000. Debranched amylopectin showed 3 peaks with polymerization degree of 28-38, 13-27 and below 12, and the percentage of long chains was higher in the samples with a high specific gravity than in the samples with a low specific gravity.

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To examine the relationship between α-glucosidase and the physical and chemical properties of rice quality for human consumption, we measured α-glucosidase and two other saccharification enzyme activities and physicochemical properties of twenty-four kinds of milled rice originally harvested in 1997. Koshihikari and Akitakomati (modern varieties) had higher α-glucosidase activity than Akamai (Tsushima, local red rice) and Sinriki (old variety). On the other hand, Akage (old variety) and Akamai (Tanegashima, local red rice) had higher α-amylase activity than Koshihikari. α-Glucosidase activity showed a negative correlation with starch-iodine blue value, total solid of residual liquid, expanded volume in cooking quality of milled rice (r=-0.542, r=-0.570, r=-0.460, respectively) and amylose content (r=-0.487). α-Glucosidase activity also showed a positive correlation with maximum viscosity and breakdown (r=0.557 and r=0.633, respectively) in pasting properties of milled rice flours employing a Rapid Visco Analyser. These results suggested that the same activity was indirectly associated with eating quality. From the principal component analysis (PCA) for all examined measurements, the first principal component represented amylose characteristics and the second principal component represented reducing sugar characteristics. The plot of PCA defined by these two factors indicated amylose characteristics, and also a chronological order of rice on the first principal component. Moreover, α-glucosidase had a higher factor loading (0.778) on the first principal component. which suggests that α-glucosidase may be related to some parts of amylopectin synthesis.

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Sensory analysis were conducted to learn if there is any difference in the sensitivity to graininess perception and taste efficiency ratio (TER) between the young (20 years old) and the elderly (more than 65 years old). Cellulose suspensions of five different particle sizes, each of three different concentration were evaluated by panels of young and elderly members for the perception of graininess in the mouth. The young panel responded that the graininess of the sample suspension depended on both the particle size and the concentrations, while for the elderly panel, it only depended on the concentration. The elderly panel could not discriminate the difference in particle size (15-75μm). We then evaluated TER by using devils tongue gel, 1% and 2.5% agar gel, and crackers, each of these samples containing either salt or sugar. The panel members were asked to taste the sample and then a salt or sugar solution, before selecting the saltier or sweeter one from the pair. The salt and sugar solutions were respectively at five and seven different levels of concentration. The results were analyzed by the probit method and indicated that there was no difference in TER sensitivity between the elderly and the young except for the 2.5% agar gel sample containing sugar. The harder and the higher the cohesiveness of the sample, the lower the TER value. While the elderly varied the number of the chews before swallowing according to the texture of the sample, the young did not.

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Antibacterial action of protamine combined with monocaprin against E. coli was investigated. The growth of E. coli Was inhibited by protamine strongly at higher concentrations, and at levels greater than 0.05% (w/w), protamine perfectly suppressed the growth of E. coli during 30°C-incubation for 44h. Monocaprin showed higher antibacterial activity than any other reagents in the presence of protamine (0.003%, w/w). The combined use of protamine and monocaprin greatly suppressed the growth of E. coli during incubation at various temperatures (20-40°C). The suitable pH for antibacterial action of protamine combined with monocaprin was in the pH region of 5-7. Protamine more actively prevented the colony-formation of E. coli than monocaprin. Cell-surface hydrophobicity of E. coli increased by the addition of protamine. Monocaprin caused a leakage of UV-absorbing substances from E. coli. Succinate dehydrogenase activity in the E. coli cell membrane was rapidly reduced by the addition of protamine combined with monocaprin.

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The off-flavor components formed from the beef plasma protein (PP) were investigated by the combined use of solid phase micro-extraction (SPME) and cryo-focusing GC analysis, with cyclohexanol as an internal standard. The presence of 63 peaks was demonstrated in the headspace of the PP solution. The 37 of these peaks were identified by their mass spectra and retention index. Hexanal was predominant component (51%), followed by pentanal (5%) and 3-methyl-butanal (3%) in the order of decreasing concentration. The relation between odor properties and sensory evaluation was also studied by using the model emulsion consisting of salad oil, water and PP (0.2-2.0%). The 25 percentage of panelists could distinguish the model emulsion containing 0.4% PP from that containing 0.2% PP. In 0.4% PP emulsion, the relative area ratio of total headspace components (to the internal standard) and that of hexanal were 79% and 11%, respectively. The addition of vinegar to an emulsion type salad dressing containing 1% PP as an emulsifier was considered to show the masking effect of off-flavor formed from PP.

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The objectives of this study were to develop a evaluation software of microbiological safety of food during microwave heating. The information of thermal inactivation kinetics of potential pathogens in food material is essential for proper thermal process design and operation. Mathematical model was developed to predict the thermal inactivation of microorganisms, Salmonella sp. and Listeria innocua, in chicken breast meat during microwave heating. The model was based on three-dimensional heat transfer with appropriate boundary conditions, and microbiological destruc- tion model. The model was solved numerically using the control volume method. Under the unsteady state, thermal inactivation of microorganism was evaluated at various conditions using the developed software with Visual Basic language.

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The effects of Hatakeshimeji (Lyophyllum decastes Sing.) on serum and hepatic lipid levels were investigated in rats. The fruit body was added at a level of 10% to a diet containing 0.5% cholesterol. Each fraction of hot-water-extract (HWE), crude polysaccharide (CP), and ethanol extract (EE) was added at a level that corresponds to 10% fruit body (7.5, 0.5, and 1%, respectively). Total serum cholesterol in the rats fed the fruit body and HWE was shown to be significantly lower. Levels of hepatic cholesterol in the rats fed the fruit body, HWE, CP or EE also showed significantly lower. Furthermore, feeding of the fruit body of Hatakeshimeji significantly increased the fecal excretion of bile acids. These results suggest that Hatakeshimeji may be a functional food for preventing hypocholesterolemia.

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The aim of this study is to verify the practical effect of starch granules on the mechanical property of some gel foods containing starch at different proportion. Compression elasticity (E_C= stress/strain) for some gels and gel foods containing various starches at the granular state were compared with elasticity modules (G') obtained by gel-dispersed dynamic viscoelasticity measure- ment (GDVM) for those starches in the past study. For the starches except for rice starches, G' obtained at 80°C for 33% starch samples (G_H) correlated with E_C of 33% starch gels at room temperature. E_C of starch-added Kamaboko generally correlated with G' for 10% starch samples (G_L), assumed to be reflected by the volume increase of starch granules, but the effects of starches originated from sweetpotato and green gram were lower than those of the starches indicating equivalent G_L. E_C of sausage was clearly increased by addition of starch, but did not show clear correlation with the GDVM values. A good correlation between E_C and G_H was observed for starch mixtures prepared by addition of various starches into wheat starch at the proportion of 30% (w/w). E_C of starch-added noodles at the same proportion as the starch mixtures also correlated with G_H for those mixtures, assumed to be reflected by average mechanical property of starch granules.

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The desmutagenicity, the radical scavenging activity and the antioxidative activity of coffee and teas consumed in Japan were compared. Coffee and subsequently black tea exhibited strong desmutagenicity against AF-2, and black tea and coffee exhibited against Trp-P-1. Sencha showed the strongest radical scavenging activity and coffee and another teas followed. Coffee, Sencha, black tea, Genmaicha, Oolong tea and Houjicha showed the antioxidative activities against linoleic acid. Sencha, Genmaicha and coffee also inhibited the carotene bleaching. Differences of activities may come from the differences of quantities and kinds of components of coffee and teas. The main component of coffee which exhibits these activities is considered to be chlorogenic acid and those of green tea, Oolong tea and black tea are catechin and its derivatives. The results of this study made clear that coffee and teas produced from tea leaf have almost the same desmutagenicity, radical scavenging activity and antioxidative activity, even though quantities and kinds of components are different.

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