Foodborne microorganisms capable of causing human diseases are exposed to a wide range of physical and chemical stresses in the environment. Exposure of cells to extreme, yet sublethal, preharvest and postharvest conditions can result in habituation or adaptation, which may subsequently afford protection against otherwise lethal stresses. The genetic basis for production of acid-shock proteins and heat-shock proteins as well as other intracellular and extracellular factors that play a role in the development of tolerance and cross protection to environmental stresses has been studied extensively, the focus largely being directed toward Escherichia coli and Salmonella. Less is known about habituation of other foodborne pathogens and spoilage microorganisms in extreme alkaline environments. Exposure of cells to sublethal concentrations of alkaline cleaners and sanitizers routinely used in food processing plants, for example, creates conditions for alkaline habituation which may result in cross protection against heat or other pasteurization or preservation technologies used in the food industry. This paper briefly reviews the genetic basis for development of tolerance of foodborne pathogens to extreme pH conditions and discusses some of the practical implications in foods and food processing environments.
Black tea accounts for almost 80% of the world’s tea production and is the most important source of polyphenol in the world. However, little has been known about the chemistry of black tea polyphenols due to their complexity. Since most of the black tea polyphenols are produced by enzymatic oxidation of green tea catechins, in vitro model fermentation experiments using purified catechins are very useful, and recently structures of some novel oxidation products of theaflavins, black tea pigments, have been elucidated. In addition, accumulation of unstable dimer quinones of epigallocatechin and its gallate during tea fermentation has been demonstrated, and the dimer quinones are converted to theasinensins, another major polyphenol characteristic of black tea, on heating. Formation and degradation of theaflavins and epigallocatechin dimer quinones are major pathways in catechin oxidation during tea fermentation and understanding the chemical mechanism is important in clarifying black tea polyphenols.
Characteristics of silver carp mince mixed with food additives, such as vital gluten, soy protein isolate, polysaccharides (β-1,3-glucan and potato starch), transglutaminase (TG-ase) and cyclodextrin, were studied. After storage at a low temperature or after heat treatment, the breaking strength of the samples was measured using a texture analyzer. The sensory characteristics of binding properties, color and smell were also evaluated. When fish mince was mixed with vital gluten, soy protein isolate, β-1,3-glucan and potato starch, the gel strength of the samples increased after heat treatment. When TG-ase was used, the binding properties improved after storage at the low temperature of 4°C. When cyclodextrin was used, the gelling properties were not improved, however, the earthy smell of the samples was attenuated. Soy protein isolate masked the earthy smell. We concluded that it is possible to utilize silver carp mince as a food material with good gelling properties by mixing with other proteins such as soy protein isolate or vital gluten.
Soft X-ray images were recorded using a super metal image intensifier camera to detect foreign materials in foods, and were analyzed by a computer with an image processor. The basic characteristics of the soft X-ray image were determined using a vinyl chloride and acrylic plate. Steel screws, aluminum rivets, staples, aluminum foil, glass and plastic fragments in a loaf of bread and a hamburger steak were identified, as well as a grasshopper under cabbage leaves. In the original soft X-ray image, it was possible to detect metallic and non-metallic foreign materials more than 1mm in size except for plastic fragments. However, as the original images of the bread and hamburger steak were not clear, it was not easy to detect such foreign materials visually. The unsharped masking treatment of a soft X-ray image was used to detect foreign materials in foods, and various image treatments were applied to detect the grasshopper under the cabbage leaves. The method is believed to be widely applicable for identifying the various kinds of foreign materials and foods.
The interfacial properties and emulsifying properties of diacylglycerol (DAG) were examined for comparison with those of triacylglycerol (TAG). The fatty acid composition and other properties of DAG were adjusted to approximately the same levels as those of TAG. The interfacial tension of DAG was about half that of TAG. When DAG was mixed with TAG, the interfacial tension of the mixture decreased in proportion to the increasing concentration of DAG and showed no breaking point. Mixtures of DAG and water were homogenized with varying oil-water proportions, with and without salt, and with and without an emulsifier. DAG was more easily emulsified than TAG and tended to become a water/oil (w/o) emulsion. The addition of salt markedly increased the stability of the DAG emulsion. DAG mixtures containing 0.25% of an emulsifier having an HLB value of between 4.5 and 13 formed w/o emulsions, while o/w emulsions were formed with TAG under the same conditions.
The limiting partition coefficient is the partition coefficient of a solute at the ice-liquid interface observed at an infinitesimal advance rate of the ice front or infinite mass transfer rate at the interface in progressive freeze-concentration. A method to determine the limiting partition coefficient was proposed based on the concentration polarization model. Electrolytes were concentrated at various operating conditions in advance rate of the ice front (u) and stirring rate (N) in progressive freeze-concentration. The limiting partition coefficients (K0) of NaCl and KCl were obtained from the effective partition coefficients (K) observed under various operating conditions. From K experimentally de-termined, ln(1/K1) was calculated and plotted against u/N0.2. This plot showed a linear line, from which K0 was ob-tained by extrapolation to u/N0.2 → 0. The limiting partition coefficient was dependent both on the solute concentration and the chemical species of solute.
We have studied changes in cadmium concentration during the cooking of rice (Oryza sativa japonica) to estimate actual intake. Samples included highly contaminated rice. Cooking involved washing and soaking rice, then cooking it in an electric ricecooker. Cadmium concentration was determined using ICP-MS. Inorganic element concentrations of P, K, Mg, Ca, Mn, Zn, Fe, and Cu were mainly decreased by washing step. Cadmium concentration was only slightly decreased by cooking and less so than other inorganic elements. In cooking of polished rice, cadmium concentration in cooked rice was about 95% of that in raw rice on a dry basis.
The antioxidative effects of enzymatic hydrolysate of horn and hoof (EHHH) from cow and buffalo, keratin-containing livestock waste, were studied using rat with carbon tetrachloride (CT)-induced liver injury. There was no effect on rat growth such as body weight gain, kidney or liver weight, when rats were fed on a diet containing EHHH. When liver injury was induced in rats using CT, the value of rat liver thiobarbituric acid-reactive substances (TBARS) increased. However, EHHH effectively reduced the value of the liver TBARS. Furthermore, EHHH restored the liver mitochondria catalase activity, which was reduced by CT.
We devised a routine evaluation method for the grain structures of baked breads using MRI. A piece of bread was soaked in Fe31 perchlorite-acetone solution, evacuated to remove the air between the grain networks, and used for measurement of MR images. Fe31 concentrations from 8 to 25 mM stained the crumb grain networks well. A plane resolution of 100 μm100 μm and slice thicknesses from 0.25 to 0.4 mm provided images suitable for analysis. A histogram of the PIXELs versus the gray level exhibited a bimodal pattern. The measurement time was shortened to 20 min per image by using the spin-echo 2D-FT method, which is less than one thirtieth the ordinary 3D image measurement time previously reported. MR images of the crumb grain networks and figures obtained by image analysis, i.e. the total-area/pore-area ratio, pore number detected, average pore size, and pore area distribution patterns, characterized the individual breads. The MR image system used in this study can replace a portion of the visual test in a sensory evaluation of bread quality in practical bread making.
On gelation of soy protein isolate during cold storage, strength, deformation, elasticity E0 and Newtonian viscosity ηN of the gels greatly increased with addition of one unit/g protein of microbial transglutaminase when kept for 3 days at 5°C, while retardation time λ decreased. With addition of 3 units/g protein, the gels were too hard, but became brittle after being kept for 3 days at 5°C. The viscoelasticity of gel treated during cold storage was superior to that of gel heated after having been kept in cold storage. It was assumed that the texture of the gel treated for one day at 5°C was nearly equivalent to that of the gel treated at 40°C for 60 min, on enzyme reactivity of transglutaminase. ε-(γ-glutamyl)lysine bonds in the gels were not formed in the case of the gel without transglutaminase, but increased linearly in the gel with transglutaminase. Contents of the sulfhydryl group of the gel were found to decrease during cold storage, and the degree of decrease was smaller in the gel with transglutaminase than in the gel without transglutaminase. This indicated less contribution of disulfide bonds in the gel treated with transglutaminase during cold storage.
Fermented fresh coffee bean, soybean and rice bran extracts (FCSRE, GuardoxTM) is a mixture of aqueous extract of fresh coffee beans, rice bran, and soybeans fermented with Bacillus subtilis Natto. Superoxide anion and hydroxy radical were effectively trapped by FCSRE, as shown by electron spin resonance experiments. Thiobarbituric acid reacting substance (TBARS) formation in human low-density lipoprotein (LDL) induced by copper ion was inhibited by adding FCSRE (0.1 mg/dl) in vitro. Male New Zealand white rabbits were assigned to two groups, control rabbits (n=8) were fed a diet containing 1% cholesterol for 12 weeks, and experimental rabbits (n=8) were fed a 1% cholesterol diet with added 5% FCSRE(2 g/kg body weight/day). Although plasma cholesterol levels rapidly increased after initiation of the high cholesterol diet, no statistical difference was observed between the control and experimental groups. After 12 weeks, sera were sampled, rabbits were sacrificed, and aortas were removed. TBARS formation in LDL induced by copper ion was significantly lower in the experimental group compared with the control group. Lag time of LDL oxidation was also significantly longer in the experimental group. FCSRE administration significantly inhibited the TBARS formation in the aorta compared with the control animals. There was a significant difference in the aortic area covered with atherosclerotic lesions between the experimental and the control groups (53.7±16.3% vs. 36.2±8.18%, p<0.05). These results suggest that FCSRE may be a promising material for the prevention of atherosclerosis.
To establish an analytical method for phenolic compounds in foodstuffs and tissue samples, we determined five simple polyphenols, five tea polyphenols and five isoflavones using high performance liquid chromatography equipped with a coulometric array detector. When simple polyphenols were detected with eight coulometric array detectors at 350 to 700 mV, trihydroxyphenols gave the highest signal at 350 mV, o- and p-diphenols at 400 mV, and m-diphenol at 700 mV. In tea polyphenols with m-diphenolic A ring and di- or triphenolic B ring, strong signals were detected at 400 and 700 mV. In isoflavone aglycons having monophenolic or m-diphenolic A ring, monophenolic B ring, and C ring with 4-carbonyl group, a strong signal was observed at 500 or 550 mV and at 700 mV. However, equol without 4-carbonyl group gave a single peak at 650 mV. These results suggest that the signal at 350–400 mV is due to the conjugated OH groups present in o- or p-derivative, the signal at 500–550 mV is due to the 4-carbonyl group and the signal at 700 mV to isolated OH groups present in monophenols or m-diphenols.
The participation of lipase in the formation of n-hexanal by homogenization of alfalfa seedlings was investigated. n-Hexanal was increased by the addition of trilinolein, dilinolein or monolinolein to the homogenate of the seedlings. Taurodeoxycholic acid sodium salt (TDCA), an inhibitor of triacylglycerol lipase, inhibited the formation of n-hexanal by 36%. These findings show that the corresponding proportion of n-hexanal was formed through the action of triacylglycerol lipase. n-Hexanal was also increased by adding the total lipids of alfalfa seedlings to the homogenate prepared with TDCA. But, when the lipids removed free fatty acids from the total lipids were added to the homogenate, the increase decreased to 18% as compared with the addition of total lipids. n-Hexanal thus also increased through the pathway, not requiring the action of the lipase and 82% of the increased n-hexanal was formed from preexisting free fatty acids. The formation pathways of n-hexanal in the seedlings were discussed.
Seven known compounds, pyrroside B (1), swertisin (2), isovitexin (3), isoswertiajaponin (4), vomifoliol (blumenol A) (5), (6S,9R)-roseoside (6) and angelicoidenol (7) were isolated from the methanol (MeOH) extract of the aerial part of Piper elongatum VAHL. and their structures were identified on the basis of physical and spectral data. In addition, the antioxidative activity of 1–4 was evaluated by the ferric thiocyanate method. All these compounds showed stronger antioxidative activity than that of α-tocopherol. Furthermore, the scavenging effects on 1,1-diphenyl-2-picrylhydrazyl (DPPH), the antihyaluronidase and the antityrosinase activities of 1–4, asebogenin (8), 2′,6′-dihydroxy-4′-methoxydihydrochalcone (9), 3-geranyl-4-methoxybenzoic acid (10), 3-geranyl-4-hydroxybenzoic acid (11), nervogenic acid (12) and 2,2-dimethyl-6-carboxyl-8-prenyl-chromene (13), which were previously isolated from the MeOH extract were evaluated. Compounds 4, 8 and 9 showed higher radical scavenging effect than that of L-cysteine, and 4, 8 and 11 exhibited stronger inhibition effect on the activation of hyaluronidase than that of tranilast. Compound 8 indicated almost the same antityrosinase activity as that of kojic acid.
The performance of partial least squares (PLS) calibration models developed using NIR and visible transmittance were examined in order to improve the accuracy of the calibration model for amylose content. The regression coefficients in the PLS calibration model developed by a full-cross validation using the wavelength region from 570 to 1000 nm (Model B) were smoother and the fluctuations of the coefficients were smaller than the model developed by a full-cross validation using the wavelength region from 850 to 1048 nm (Model A). Significant peaks in the regression coefficients of Model A were characterized by two absorption bands at 928 and 990 nm, and those of Model B were characterized by four absorption bands at 607, 760, 928 and 990 nm. The samples were separated into calibration sets and validation sets, and PLS calibration and validation were also performed. The statistics performance (standard error of performance (SEP), a coefficient of determination (R2)) of the model developed using the wavelength region from 570 to 1000 nm (Model D), was better than those of the model developed using the wavelength region from 850 to 1048 nm (Model C). The SEP of 0.64% on model D examined here was smaller than that of 0.99% on Model C. Therefore, the absorption bands at 607 and 760 nm play an important function in improving the performance of the PLS calibration model.
We examined the anti-metastatic effect of 6-(methylsulfinyl)hexyl isothiocyanate (6-MITC) isolated from wasabi (Wasabia japonica MATSUM). Pulmonary micrometastasis was quantified using a dependable method to detect the human c-Ha-ras gene, which was carried in the tumor cell line. Mice belonging to the S-1 group were administered 6-MITC continuously for 35 days from the time of tumor cell inoculation, and S-2 group mice were administered 6-MITC for 21 days from the day of amputation. Oral administration of 200 μM 6-MITC solution was effective in preventing metastasis of the experimental tumor. In the S-1 group, 7 out of ten experimental mice have lungs carrying no detectable human c-Ha-ras gene. Amplified human c-Ha-ras bands were detected in only the lungs of three mice; in these, the metastatic indexes of the lungs were respectively 0.60, 0.70 and 0.90. In the S-2 group, the bands were detected in four lungs of 5 experiments, with the metastatic indexes of the lungs in the range 0.36–0.72. Starting the treatment at the time of tumor cell inoculation was more effective in preventing metastasis than beginning the treatment on the day of amputation.
Iyo tangor (Citrus iyo hort. ex Tanaka) seeds contained limonin, nomilin, obacunone and deacetylnomilin, in order of decreasing concentration. They also contained the 17-β-D-glucopyranosides of nomilin, obacunone, limonin, deacetynomilin and nomilinic acid. Total limonoid aglycone concentration in the seeds was 873 mg per 100 g on a dry weight basis and total limonoid glucoside concentration was 446 mg. The composition and relative concentration of each limonoid aglycone and glucoside in Iyo tangor seeds were very similar to those of other citrus species distributed widely in western Japan such as Valencia orange (C. sinensis Osbeck), Sanbokan (C. sulcata hort. ex Tanaka) and Hyuganatsu (C. tamurana hort. ex Tanaka). These data reveal that Iyo tangor taxonomically belongs to the same group as those citrus species.