Secondary plant metabolites are important native food components, which are becoming more and more interesting due to their physiological effects on human beings. One of the largest groups of these compounds is represented by plant phenols. This review summarizes the structure, classification and distribution of the phenolic compounds in plant foods, their chemistry and signification with regard to food processing and -storage as well as their physiological effects. This work focuses mainly on such reactions of the phenolic substances with proteins and enzymes that lead to covalent bonds. The derivatives formed have been characterized in terms of changes in their physicochemical and structural properties. The effect on the proteolytic in vitro digestion has been also illustrated. Further aspects reported include the influence on enzyme activity and -kinetic parameters. The different aspects of the nutritional-physiological consequences of such reactions in food and body, especially considering their significance to food science and technology are discussed.
In bread-making, baking process is one of the key steps to produce the final product qualities including texture, color and flavor, as a result of several thermal reactions such as nonenzymatic browning reaction, starch gelatinization, protein denaturalization and so on. These thermal reactions are dominated by heat and mass transfer mechanisms inside an oven chamber as well as inside the dough pieces. Mathematical models have been developed to ac-count for the heat and mass transfer phenomena and their consequent impacts on the product qualities. These studies have made the complicated baking process more clearly understood and predictable. As a result, baking process conditions can be optimized. In addition, new baking techniques and oven designs have been proposed in order to im-prove product qualities with better process economics.
A continuous soft X-ray system with a semi-conductor detector was used to detect foreign materials in food samples. Basic properties of transmitted and reflected soft X-ray for some metallic and non-metallic materials were measured using the Si-PIN sensor equipped with a multi-channel analyzer. Soft X-ray spectra in photon energy were obtained for copper, galvanized iron, acrylic, vinyl chloride and glass of different thickness as foreign materials in foods. This detecting system was capable of analyzing intensities of transmitted and reflected X-rays at each energy level in the broadband. The reflected soft X-ray spectra were found to have characteristic spectrum curves for each sample. In order to detect acrylic, vinyl chloride and glass in a hamburger patty, the reflected soft X-ray spectra were analyzed and this technique was found to have the potential for more sensitive detection of foreign materials. The detecting system using properties of transmitted and reflected X-rays at each energy level is considered to be valid for non-metallic foreign materials.
The purpose of this study was to develop a model in which the migration rate of water in tobacco was expressed through the effective diffusion coefficient. The effective diffusion coefficients were calculated over a broad range of water content and temperature from the results of adsorption and desorption curves of water on tobacco. As a result, it was found that the migration of water could be macroscopically represented as one-dimensional diffusion in the thickness direction of tobacco. The effective diffusion coefficients obtained from the diffusion equation were strongly dependent on the water content and temperature. It was shown that the temperature dependence of the effective diffusion coefficients is expressed by Arrhenius equation. Consequently, it became possible to estimate the migration rate of the water at desired temperature and water content. Thus, one of the important factors in determining the processing conditions of tobacco has been clarified.
An electrochemical measurement of yeast cell density and vitality was developed using 2,3,5-trimethyl-1,4-benzoquinone. 2,3,5-Trimethyl-1,4-benzoquinone was reduced most effectively to the corresponding hydroquinone by yeast cells. The hydroquinone produced was detected amperometrically on the glassy carbon electrode. Ethanol was essential for the effective metabolism of quinones by yeast cells. The maximum oxidative current was obtained at the ethanol concentration of 8–10% regardless of the strain of yeast. The promotion of the metabolism of quinones was thought to be based on the increase of plasma membrane permeability by ethanol molecules. A linear relationship between the oxidative current and cell density of yeast was obtained in the range of 6.4103–1.6106 cells/ml assay solution. During the cultivation of yeast cells the oxidative current showed an almost parallel change with that of glucose in yeast growth and fermentation, suggesting that the oxidative current change reflected the vitality of yeast cells.
To develop a new type of Miso, low salt miso-like fermented seasonings were prepared with soybean Oncom(S-Oncom) and Okara Oncom (O-Oncom): those were fermented soybeans and fermented Okara with Neurospora intermedia, respectively. Their antioxidant activity and antimutagenicity were analyzed and both Oncom had higher β-glucosidase activity than Koji (cooked rice molded with Aspergillus oryzae) with or without the presence of 4% salt and 2% ethanol. The strongest 1,1-diphenyl-2-picryl-hydrazyl radical scavenging, superoxide anion scavenging and antimutagenic activities were detected in the extracts prepared from the seasonings with S-Oncom, O-Oncom and Koji with both 70% ethanol and with water. These activities of O-seasoning are attributable to the isoflavone aglycones present and to water soluble substances. Based on these results, O-seasoning is deemed to be healthier than other low salt miso-like fermented seasoning prepared with steamed soybeans and Koji. Furthermore, the dishes prepared using O-seasoning were evaluated as acceptable.
Auricularia polytricha was incubated in potato-sucrose-agar (PSA) and in a sawdust medium supplemented with Ca or Mg salts. The mycelia grew well on the PSA supplemented with Ca sulfate, Ca phosphate, Mg sulfate and Mg chloride. On sawdust medium, the supplementation with Ca phosphate, Ca carbonate, Mg sulfate or Mg carbonate resulted in good mycelial growth. The Ca content of fruit body grown on the sawdust medium was increased 1.1–1.5 times by supplementation of 1–5% of Ca phosphate or Ca carbonate. The Mg content was increased 1.7–2.2 times by 0.5% of Mg carbonate, Mg hydroxide, Mg sulfate and Mg chloride.
Fish protein hydrolysate (FPH) was prepared from scraps of 5 marine species, in order to utilize by-products effectively by protease treatment. Protein was the major component of the FPH ranging 82–86%. The effects of 5% FPH (dried weight/wet weight) on the state of water and the denaturation of lizard fish Saurida wanieso myofibrils were evaluated by desorption isotherm curves, Ca-ATPase activity, and differential scanning calorimetry (DSC) during dehydration. The myofibrils with FPH showed a decreased water activity (Aw), while they exhibited significantly higher Ca-ATPase activity compared to myofibrils without FPH (control). The myofibrils with FPH had higher amount of unfrozen water than the control. These results suggest that the FPH suppressed dehydration-induced denaturation, which seems to be attributable to the stabilization of the hydrated water surrounding the myofibrils.
The flavor of an unheated wheat flour and butter mixture (roux 0) and roux samples heated to between 100°C and 180°C at 20°C intervals (roux I–V) were examined by chemical analyses of the aroma components with gas chromatography (GC) and GC-MS and sensory evaluation of the roux samples. In the chemical analysis, it was determined that large quantitative changes of aroma components with increased heating temperature occurred in the functional groups of ketones, carboxylic acids, furans and pyrazines. Furthermore, a cluster analysis showed that the difference in characteristic flavor between roux II (white roux) and roux IV–V (brown roux) depended on the quite different compositions of their components. On the other hand, sensory analysis of the roux showed that roux II–IV (heated to 120°C–160°C), namely white and brown roux, were highly evaluated for buttery and sweet attributes as well as odor preference. After the relationship between chemical and sensory changes in the roux flavor with increased heating temperature was surveyed by a principal component analysis, a correlation analysis clarified that the sensory odor preference correlated significantly with ketones (mainly methyl ketones) (r=0.900, p<0.05) or with cyclic ketoenols such as maltol (r=0.838, p<0.05). Those compounds also showed a high positive correlation with the evaluation for the sweet attribute. Therefore, methyl ketones or cyclic ketoenols are assumed to play an important role as indicators of the pleasant odor preference in roux heated to various temperatures.
A high performance liquid chromatograph coupled with a tandem mass (MS/MS) detector was used for the analysis of 4-dimethylaminoazobenzene-4-sulfonyl chloride (dabsyl-Cl) derivated amino acids. Apart from dabsyl-Cys and dabsyl-Lys, the other 18 common amino acid derivatives had good linear relationship between the responding peak area and concentrations between 10–250 μM, R2>0.99. The responding peak area of dabsyl-Lys at a low concentration was suppressed by that of dabsyl-Gln in samples of the amino acid mixture, because signals of both amino acid derivatives were present in the same selected reaction monitoring (SRM) channel. A linear regressional curve of dabsyl-Lys was therefore obtained only in the range of 250–1000 μM, R2>0.96. Dabsyl-Cys was destructed to get a unique ion of m/z 290 before entering the MS/MS detector. The regressional curve of the responding peak area and concentration of dabsyl-Cys was therefore obtained with the SRM of m/z 290 to its product ion m/z 225.1. A linear relationship was obtained between 1–10 mM, R2>0.98. The established method was used in the analysis of amino acids in a koji liquid. The results showed better identification of the dabsyl-AA and the method is, therefore, more reliable in analyzing amino acid contents in complex food mediums.
We purified glutamate decarboxylase (GAD) [EC18.104.22.168] from Aspergillus oryzae and characterized its biochemical and kinetic properties. GAD was purified by ammonium sulfate at 30–70% saturation and chromatographies on Sephacryl S-300, DEAE-FF and CM-FF. The purification of GAD from the crude enzyme solution was 40-fold and the recovery rate was 4.9%. About 230 μg of purified enzyme was obtained from 20 g of the mycelia of A.oryzae. The purified preparation of the enzyme showed a single protein band on SDS-PAGE. The molecular weight of purified GAD by SDS-PAGE and gel filtration was estimated to be 48 kDa and 300 kDa, respectively, suggesting that purified GAD had a hexameric structure. The Km value for L-glutamic acid, a substrate of the enzyme, was estimated to be 13 mM. The optimum pH and temperature of GAD were 5.5 and 60°C, respectively. The GAD activity was stable up to 40°C.
Two types of anthocyanin, cyanidin 3-O-β-D-glucopyranoside (cyanidin 3-glucoside) and peonidin 3-O-(6-O-α-L-rhamnopyranosyl-β-D-glucopyranoside) (peonidin 3-rutinoside) were isolated from ginger rhizomes by various chromatographic methods. A comparison of the content of these compounds showed their presence in many kinds of Japanese ginger, but not in Chinese ginger. In particular, peonidin 3-rutinoside, which we identified for the first time in the ginger rhizome, was the main anthocyanin constituent at 0.67–2.38 mg/100 g of fresh ginger rhizome, and its concentration was 2.0–43.4 times higher than that of cyanidin 3-glucoside. These two anthocyanins were only present in the lower stem and rhizome in the ginger plant, and their proportions in the lower stem were different from those in the rhizome, cyanidin 3-glucoside being much more abundant than peonidin 3-rutinoside in the lower stem. These results suggest that the anthocyanin formation in ginger varies according to its variety, the part of the plant, and the place of cultivation.
Physicochemical and conformational changes, water-holding capacity (WHC) and the structure of heat-induced gel of porcine myosin were investigated to elucidate the relationship between denaturation of myosin and gelation properties during postmortem aging. The turbidity of porcine myosin upon heating increased as the period of postmortem aging increased. During postmortem aging, the increased velocity in values of aliphatic hydrophobicity of porcine myosin by heating was prominent, which suggested that porcine head was susceptible to conformational changes during storage. On the other hand, according to the changes in circular dichroism (CD) spectra of heated porcine myosin, the decrease in α-helix content was almost the same during postmortem aging, indicating no conformational changes in porcine myosin rod during aging. WHC values of porcine myosin gels showed a gradual decrease during storage. This coincided with the progressive loosening in its three dimensional ordering with increased postmortem aging period, as was revealed by SEM studies. In conclusion, conformational changes of myosin head by denaturation during postmortem aging of pork could cause a progressive loosening of heat-induced gel of porcine myosin. This result could be, in part, helpful in the subsequent use of pork in meat processing.
The methods of sanitary inspection performed primarily by traditional culture methods are time consuming, laborious, and require complicated laboratory techniques. A number of instrumental methods have been introduced for the rapid determination of viable cells based on the metabolic activities of microorganisms. The DOX system is one of the newly developed rapid inspection methods. It has three independent incubators that hold 60 vials each can estimate viable bacterial cell number by measuring the respiration speed of microorganisms and also has a high correlation between the detection time (Dt) and the viable bacterial cell number. We made a quantification analysis of coliform, and identified the presence of Escherichia coli from various kinds of vegetable samples. A total of 131 vegetable samples were tested to compare the plate count of coliform to the count using the DOX method. The correlation coefficient for the estimation of coliform-bacterial cell number was 0.85, which theoretically suggested that the DOX system was able to detect one cell of coliform-bacteria after 17.7 h of incubation. Among the 131 samples, 20 samples were confirmed for the presence of E. coli-positive cells using the UV-lamp method. This study suggested that the DOX system performs better than the conventional method for the routine inspection of coliform and E. coli from vegetable samples. Therefore, this system could be useful for the rapid detection of coliform and E. coli from vegetable samples with minimum labor and cost.
Bacillus natto is the main microorganism used to make natto (fermented soybeans), because this microbe has good ability to produce protease. However, it is known that some genera of mushroom also produce protease, and in this study we made a fermented soybean using a mushroom mycelia in place of B. natto. We found that the fermented soybean made using mycelia of Flammulina velutipes and Roseofomes subflexibilis showed a thrombosis preventing activity: a prolonged thrombin clotting time 8.2 fold that of control.
We have bred red-fleshed potato from hybrid seedlings between cultivars of Solanum tuberosum ssp. tuberosum and S. tuberosum ssp. andigena. The anthocyanin of red-fleshed potato inactivated both influenza viruses A (IVA) and B (IVB). The IC50 of red-fleshed potato anthocyanin was 48 μg/ml (IVA) and 54 μg/ml (IVB). The IC50 of pelanin was 107 μg/ml (IVA) and 83 μg/ml (IVB). The antiviral activities of pelanin against influenza viruses were lower than the red-fleshed potato anthocyanin. In our previous reports black currant anthocyanins showed an additive antiviral effect. Therefore, we believe that the antiviral activity of the potato anthocyanin comes from the additive or synergistic effect of each anthocyanin pigments and other coexisting pigments.
Soybean protein isolate was hydrolyzed using two proteases (Protease M and Orientase 90N), and the inhibitory activity of angiotensin I-converting enzyme (ACE) and bitterness of the hydrolysates were investigated. The ACE inhibitory activity of the hydrolysates increased with increasing hydrolysis time. Hydrolysates obtained using Protease M for 4 to 10 h and Orientase 90N for 6 to 10 h showed a high ACE inhibitory activity, and the bitterness was negligible. The ACE inhibitory peptides were shown to be oligopeptides composed of 2–5 amino acid residues. These peptides might be useful for therapeutic applications based on the consumption of an anti-hypertensive food.
Japanese horseradish, i.e. wasabi (Wasabia japonica MATSUM.), cultivars are classified as green-stem and red-stem types. It is believed that pungency differs slightly between the types. We analyzed isothiocyanate levels and myrosinase activity in two wasabi cultivars, Maruichi and Mazuma, a green-stem and a red-stem type, respectively. Time-course experiments were performed monthly from May 2001 to October 2002, separating plants into leaves, petioles, and rhizomes. Allyl isothiocyanate production induced by maceration occurred in whole plants in both cultivars, though the major organ producing the isothiocyanate was the rhizome. Levels of myrosinase activity in the rhizome of Maruichi increased in November and December 2001, when allyl isothiocyanate production also increased in Maruichi’s rhizome. Although levels of allyl isothiocyanate did not differ between the two cultivars, Mazuma produced isopropyl isothiocyanate but Maruichi produced little. These results suggest that the difference in pungency between Maruichi and Mazuma may be derived from the isothiocyanate component.