Tea and coffee drinks canned or bottled in polyethylene terephthalate (PET) containers are the most important commercial soft drinks in Japan, and a high-quality favor is desirable. However, it has been difficult to realize this, especially in terms of providing a natural and characteristic flavor and maintaining the fresh flavor of homemade tea infusions and coffee brews. Scientific knowledge of the chemistry of tea and coffee drink flavors has made much progress in recent years. This paper reviews the progress of the flavor chemistry of potent odorants in Japanese green (Sen-cha) infusion and roasted coffee brew, and the deterioration of tea and coffee flavors during the manufacturing process of commercial drinks.
The production of high concentrations of physiologically active pentameric and hexameric chitosan oligosaccharides was investigated. Chitosanase directly immobilized on an agar gel-coated multidisk impeller was used for the hydrolysis of chitosan. As hydrolysis proceeded, the concentration of chitosan was increased from the saturation concentration (20kg/m3) to 50kg/m3 by stepwise addition of chitosan powder with pH control. The timing of the addition of the chitosan powder was determined by monitoring the change in the torque required to agitate the reaction solution. The target products were produced more efficiently when the chitosan powder was added over a short interval rather than a long interval. When hydrolysis of a 50kg/m3 chitosan solution at 50°C was repeated three times using the same immobilized enzyme, the target products were obtained in high concentrations (20kg/m3) from each of the three reactions with no reduction in the activity of the immobilized enzyme.
We investigated whether the physical properties (rheological properties) of various bread doughs, obtained from a linear Kelvin four-element model of visco-elasticity, could be used to express the expansion ability of the dough during bread-making. The physical properties τ0 and τ1 (relaxation and retardation time, respectively) were determined from the creep. The stress relaxation curves derived from the τ0 values of various doughs, such as Victoria INTA (extra strong flour), Camellia (strong flour), and Hokushin (semi-strong flour), approximated the experimental results well. By analyzing the relationship between each coefficient in this model and the expansion ability of bread dough (specific loaf volume and gas retention), it was proven that τ0 and τ1 were positively and negatively correlated, respectively, to the expansion of bread dough to a statistically significant extent. From these results, it was suggested that dough with more elastic properties shows greater expansion. It is known experientially that adequate dough elasticity is necessary for good expansion, and the results of this study support the previous data.
Spectral analysis and image processing of the spectral images of blueberries and several foreign substances clarified that plant organs could be detected by the second derivative absorbance image at 680nm, which is an absorption band of chlorophyll. As a feasibility study, spectral images of blueberries and plant organs placed in the 160×120mm area were acquired at 660, 680 and 700nm in order to develop a second derivative absorbance image at 680nm. Then the second derivative absorbances of 52 blueberries and 26 plant organs in the image and their mean values were calculated. Using these data, the probability of being a plant organ, p, was calculated for each pixel of the second derivative absorbance image in order to develop a plant organ detection image. In the detection image, a pixel with p value larger than 0.95 was judged as a plant organ. The positions of pixels judged as plant organs in the detection image were in good agreement with the actual locations where plant organs had been placed. Therefore, it could be concluded that plant organs contaminated raw blueberry materials could be detected using the method developed in this research.
The effects of lactic acid bacteria used as a substitute for nitrite for meat processing were studied. We added lactic acid bacteria starter culture to brine to cure pork loin without nitrite. The cured pork loin was then smoked, sliced, vacuum-packaged, and stored at 2°C for two weeks and at 7°C for additional weeks. A preservative effect of the added lactic bacteria was observed. A homo-fermentative lactic acid bacteria Lactobacillus sakei M32 was a good starter culture to control the microflora of products without nitrite. Bright red color development and propagation between some samples were observed during the cold storage in vacuum packages. This color development is not yet practical for industrial application as a substitute for nitrite. The samples, which had turned clear red in cold storage after two weeks, were further analyzed. In these samples, free arginine markedly decreased, while other free amino acids slightly increased. Although the residual nitrite in the samples was less than one ppm, the degree of color formation of the samples was similar to that of the positive nitrite-added control samples. The results suggested formation of bright red myoglobin derivatives, such as nitrosylmyoglobin from arginine, in the samples.
A method to predict the chromaticity of many kinds of raw soy sauce after pasteurization from main chemical constituents was studied. The raw soy sauce pasteurization temperatures were set at three levels in the range of 65 to 90°C and at five time levels in the range of 0 to 60min. A spectral absorption of the raw and pasteurized soy sauces in the wavelength range of 380 to 780nm was used to obtain optical density at 450nm (E450), and chromaticity was measured. It was confirmed that relationship between browning rate constant calculated from change in E450 over the studied time and temperature range was applicable to the Arrhenius equation. A pioneer non-linear mathematical model to predict the chromaticity of soy sauce after pasteurization from the main chemical constituents was generated by the multiple regression and least square methods. Effectiveness of the proposed models was confirmed using actual data.
The changes in the quality of three vegetable oils : soybean oil, corn oil and cotton seed oil, occurring during heating in superheated steam (SHS) were compared with the changes occurring during heating in hot air (HA). The temperature of both the SHS and the HA was 180°C, and the heating time ranged from 30 to 180minutes. The quality of the oils was investigated by evaluating the acid value, peroxide value, viscosity, color and odor. The acid value, the peroxide value and the viscosity of the oils heated in SHS were lower than those of the oils heated in HA. SHS-treated oils retained their fresh oil color and odor, whereas HA-treated oils changed their color and odor remarkably. Therefore, the influence of the SHS treatment on the oil quality was not significant.
We attempted to remove musty odor causing components in drinking water by a method of continuous flow extraction using microbubbles of supercritical carbon dioxide (SC-CO2 method), which has been developed as an extraction technique for volatile compounds from foods. Both the SC-CO2 method (10MPa, 35°C, 39% CO2/sample flow rate, 7min exposure time) and a powdered activated carbon method were effective in removing more than 90% of the two musty odor components, 1,2,7,7-tetramethylnorbornan-2-ol (2-methyl isoborneol ; 2-MIB) and Geosmin (GEO), in the prepared model water. Moreover, foul odors such as the sludgy odor of actual reservoir and city tap water samples were almost completely destroyed by the SC-CO2 method (20MPa, 35°C, 71% CO2/sample flow rate, 13min exposure time). Thus, we concluded that the SC-CO2 method was very effective for removing foul odor components of water such as those that produce a musty odor.
The formation of zinc protoporphyrin IX (ZPP) in porcine heart extract was investigated by visible absorption and fluorescent spectral analysis. Characteristic absorption peaks of ZPP were observed at 417, 546, and 584nm after anaerobic incubation of the extract with metmyoglobin and ZnCl2 in the dark at 30°C for 72h. In the fluorescent spectra (excitation : 410nm), a strong peak due to ZPP was obtained at 589nm. The time-course study showed that ZPP formation greatly increased after a lag period, during which metmyoglobin was reduced. ZPP formation was significantly facilitated by the use of oxymyoglobin. Zinc chelatase activity in the extract was estimated as 138mU/mL-extract and its specific activity was 2.95mU/mg-protein. The difference in activities with aerobic and anaerobic incubation was not significant. Measurements at pH 5.5-7.0 showed that activities were higher at lower pH. The activity of zinc chelatase was stimulated by the presence of ATP, and the highest activity was obtained at an ATP concentration of 2.5mg/mL.
Chardonnay wine produced in the conventional manner contained 69.8 to 108mg/L soluble proteins including nondialyzable polypeptides ; with an average of 87.2mg/L. Proteins were separated by precipitation with ammonium sulfate, and fractionated into two fractions, F1 (mainly invertase and proteoglycans) and F2 (glycoproteins), by Sephadex G-100 column chromatography. The fractions were further separated by two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) [isoelectric focusing and SDS-polyacrylamide gel electrophoresis]. More than 160 and 150 protein spots were detected on the 2-D PAGE maps of F1 and F2, respectively. The major proteins or polypeptides were determined to be fruit proteins, such as thaumatin- and osmotin-like proteins, invertase, lipid transfer protein (LTP), and their hydrolysis products. This is first report on the existence of LTP (or its hydrolysis product) and the hydrolysis products of major grape proteins (invertase, osmotin-like protein, and thaumatin-like protein) in wine.
To elucidate the history of human exposure of psicose, a determination method of psicose (D/L-psicose) in various food products has been developed : post column high-performance liquid chromatography (HPLC) using gel permeation column in ligand exchange mode coupled with pulsed amperometric detection (PAD). The calibration curve of D-psicose was linear in a concentration range of 5 to 150μg/ml with a correlation coefficient of 0.9999. With ultrasonic extraction and C18 Sep-pack filtration methods, the samples for HPLC analysis could be prepared from various food products within 0.5-1.5h without any interference materials. The psicose recovery (n=5) from coffee and corn-snack was found to be 96.6% with relative standard deviation (R.S.D.) of 1.9% and 96.7% with R.S.D. of 3.0%, respectively. The resultant psicose content varied from 0.5mg/100g (coffee) to 130.6mg/100g (Worcester sauce). In particular, confectionery products and seasoning sauces exhibited higher psicose content than other studied products. In high sugar food products, heat processing had a marked effect on the production of psicose. The psicose formation due to heating was suggested to be a non-enzymatic reaction.
To clarify immunoregulatory activity of “Shiranui Himekiku” (Chrysanthemum indicam×Erigeron annus), we examined the effect on tumor necrosis factor α (TNF-α) production by mouse macrophage-like cell line RAW264.7. The dried chrysanthemum flower (CF) petals were extracted with water, and the cells were cultured in the presence of the extract. CF extract significantly enhanced TNF-α production of the cells by the dose-dependent manner. Diluted CF solution did not significantly affect the cell number and viability ; however, non-diluted solution suppressed the cell proliferation and decreased the cell viability. Heating CF extract at 100°C for 30min enhanced the activity of water extract markedly, and freeze-thawing only moderately. The TNF-α production enhancing activity of the extract was observed within 3h. These results suggest that the TNF-α production enhancing activity of CF extract can be recovered efficiently by hot water extraction and preserved stably by freezing.
A compound with 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, produced in the course of roasting coffee beans, was isolated from instant coffee. The chemical structure of this compound was elucidated to be 3-pyridinol on the basis of various spectra analyses. It prevented cytotoxicity induced by D-galactosamine in primary cultured rat hepatocytes, indicating that this compound may prevent liver injury partly induced by the action of radicals.
Culture medium containing dipicolinic acid at final concentrations of 0, 1, 2 and 4mM were inoculated with the Miyagino strain of Bacillus subtilis natto, the bacteria used for the production of natto, and subjected to stationary culture for 24 hours, after which the activity of nattokinase was investigated using two methods : a standard fibrin plate method, and the synthetic substrate Suc-Ala-Ala-Pro-Phe-pNA. Using the standard fibrin plate method, it was confirmed that nattokinase activity rose to 12.5FU/ml in the samples containing 2mM dipicolinic acid, a value 5.6 times greater than that of the sample containing no dipicolinic acid (2.25FU/ml). Colorimetric measurements using the synthetic substrate showed that the activity level was highest (168.5nmol/min/ml) with addition of 2mM dipicolinic acid, about 4.3 times the activity of the sample with no dipicolinic acid (39.6nmol/min/ml). The effects of dipicolinic acid were also clear for the Naruse strain of Bacillus subtilis natto. Based on the results of comparison tests using DPA and nine structurally related compounds, including nicotinic acid, it appears that dipicolinic acid is capable of enhancing specific nattokinase production to a considerable extent.
Orange-fleshed sweet potato (OR-SP) cultivars rich in β-carotene are considered to exhibit higher antioxidant capacity than yellow-fleshed sweet potato (YE-SP) cultivars, consumed commonly in Japan. However, little information exists on the contribution of β-carotene to the antioxidant property. In this study, 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) cation radical (ABTS•+) scavenging capacity in eight OR-SP cultivars and three YE-SP cultivars were measured and compared. The radical scavenging capacity of OR-SP ranged from 493 to 969μmol Trolox equivalent (TE)/kg fresh weight (FW), and that of YE-SP ranged from 254 to 728μmol TE/kg FW. The β-carotene content in OR-SP ranged from 139 to 330μmol/kg FW and it exhibited 1.66 times higher radical scavenging capacity than a Trolox standard. The contribution of β-carotene to the total radical scavenging capacity was estimated to be in a range of 36.3 to 79.6% in OR-SP. Moreover, by staining the TLC plate with an ABTS•+ solution after separating the constituents, it was suggested that a species of radical scavengers were common to all cultivars.