It is highly important to rheologically characterize the factors and structures of gelatinized rice flour gel (rice cake) to control both the qualities of the final products (rice cracker) and the manufacturing process. Accordingly, attempts were made to analyze the rice cake factors and understand the structure by measuring the shear viscosity development after the onset of steady shear flow of various rice cake samples, which were different both in rice cultivars (the primary factors) and in preparation conditions (the secondary factors). As a result, it is considered that the viscosity and elasticity terms in the linear region and the nonlinear region contribute to the analysis of the primary factors and the secondary factors, respectively and furthermore understanding the relationship of each to the pseudo-network structure of rice cake.
In the manufacturing process, the relationship between the expansibility of glutinous rice crackers and the properties of gelatinized and retrograded rice flour gel (rice cake) has not been fully clarified. We analyzed glutinous paddy rice from various angles using proximate analysis, amylography, measurement of degree of dispersion and differential scanning calorimetry. The tendencies, depending on cultivars, as measured were related. In particular, it was suggested that the amount and strength of intermolecular hydrogen bonds in rice was related to the expansion volume of rice cake because the enthalpy and peak temperature of DSC is closely related to its volume. Accordingly, it was suggested that DSC might be usable as a common standard for characterization of the factors affecting the properties of rice cake and its structure from the viewpoint of rice cracker expansibility.
A flow injection method to determine the concentrations of (—)-epigallocatechin gallate (EGCG) in tea infusions was developed. A bioreactor, packed with immobilized tannase, was connected to a pH-ISFET (Ion Sensitive Field Effect Transistor) electrode. The pH decrease, due to the gallic acid produced from EGCG by the enzyme reaction, was monitored by the electrode. The response of this system was linear between 50 mg/l and 1,000 mg/l of EGCG. The sample could be injected every 3 min. The concentrations of EGCG in green tea infusions obtained by this FIA method showed a fairly high correlation with those by HPLC.
A kinetic model including isomerization of fatty acids for soybean oil hydrogenation considering the adsorption of fatty acids on the catalyst surface affecting the hydrogenation rate has been evaluated in this study. The hydrogenation of soybean oil was conducted in a 12 l loop reactor equipped with a venturi nozzle. A reduced nickel catalyst was adopted. The hydrogenation experiment was carried out an experimental design with respect to reaction temperature, flow rate of catalyst-oil mixture, hydrogen pressure and reaction time. Adsorption of fatty acids including trans-acids on the surface of the reduced nickel catalyst significantly affected the reaction rate of the hydrogenation. The adsorption equilibrium coefficients of linolenic and linoleic acids were much greater than those of oleic and elaidic acids, which indicated that the former acids were hydrogenated faster than the latter acids. The time course of fatty acid concentration calculated from the hydrogenation rate constant derived from the kinetic model proposed in this study was in good agreement with those obtained from experiments. The kinetic model explained the hydrogenation totally with consideration of trans-acid formation.
Changes in free amino acid content of γ-irradiated onions during storage were investigated using HPLC analysis. A radiation dose of 0.2 kGy for sprouting inhibition had no influence on the amounts and the patterns of changes in amino acids during storage. The contents of γ-aminobutyric acid (Gaba) and alanine (Ala) of onions remarkably increased with an excess dose of 5 kGy irradiation. The increase in Gaba and Ala of onions stored in nitrogen gas for 4 weeks were similar to that of 5 kGy-irradiated onions stored for 3 weeks after irradiation.
An alginate lyase was purified from a crude enzyme of Flavobacterium multivolum K-11 by successive column chromatographies, such as cation exchange, chromatofocusing, and gel filtration. The enzyme thus obtained migrated as a single band on SDS-PAGE. The relative molecular mass of the enzyme was 43-kDa by SDS-PAGE and 41-kDa by HPLC gel filtration chromatography. The isoelectric point of the enzyme was 8.7. The enzyme exhibited maximum activity at pH 8.0 and 40°C, and was stable in the pH range of 6.0 to 9.0 and at temperatures up to 30°C. The enzyme activity was remarkably inhibited by chemical compounds such as EDTA, PCMB, MIA, TNBS, and N-bromosuccinimide. The enzyme was specific for poly-guluronate and produced several kinds of oligomers. Thus, the results suggested that the enzyme was classified as endo poly (α-L-guluronate) lyase (EC 188.8.131.52).
The physiology and quality of ‘Greenbelt’ broccoli florets (Brassica oleracea L. italica) were monitored during CA storage in 0.5% O2 and 10% CO2 at 0 and 5°C and in 1% O2 and 10% CO2 at 10°C and subsequent air storage at the same temperature. The CA reduced respiration, weight loss, and decay at all temperatures, yellowing and L-ascorbic acid loss at 5 and 10°C, and ethylene production and microbial growth at 10°C. Upon transfer of the florets to air following CA storage for 4, 3, and 1 weeks at 0, 5, and 10°C, respectively, respiration rate increased initially and then remained constant. Ethylene production continually increased. Decay, microbial count, odor, color, and L-ascorbic acid content remained essentially unchanged for a few days after the samples were transferred to air regardless of temperature.
Changes in the sugar content and sucrose metabolizing enzymatic activities of stored green peas were studied. Green pea seeds were removed from their pods, and the pods without seeds or whole peas were stored at 1°C or 20°C. Their sucrose content significantly decreased, especially in seeds without pods stored at 20°C, but the stachyose and verbascose contents increased. Glucose and sucrose were the major components in the pods. The pod sucrose content significantly decreased, especially in pods with seeds stored at 20°C. Sucrose synthase (sucrose synthesis, sucrose cleavage) and invertase activities in the seeds decreased during storage, but sucrose phosphate synthase activity increased after 1 or 2 days of storage and then decreased. According to these results, we suggest that sucrose might be utilized not only in the synthesis of starch, but also in the synthesis of the raffinose family of oligosaccharides such as stachyose and verbascose.
The tetrapeptide originating from a peptide synergist consisting of 21 amino acid residues (peptide C-1) was found to increase the antioxidative activity of α-tocopherol (Toc) and sodium ascorbate (AsA). Peptide C-1, which had been previously isolated from bovine serum albumin hydrolysates, was again hydrolyzed with a lysyl endopeptidase to give three peptide fragments. Each fragment was tested for its synergistic effect with Toc and AsA, and only one fragment had a potent synergism comparable to the original peptide, C-1. The structure of the active fragment was confirmed as the tetrapeptide, Asp-Thr-His-Lys, by amino acid analysis and sequence determination. In addition, peptide C-1 and its active fragment corresponded to residues 1 to 21 and 1 to 4 of BSA, respectively.
To estimate the effect of food processing on allergen content in dairy products, β-lactoglobulin (β-LG) contents of 4 milks, 5 yogurts and 6 cheeses were compared using inhibition ELISA (enzyme-linked immunosorbent assay), SDS-PAGE and immunoblotting. Results of the inhibition ELISA suggested that low temperature-pasteurized milk contained several times higher levels of β-LG than high temperature-pasteurized milk, and that yogurts contain a lower amount of β-LG than milks. On the contrary, results of SDS-PAGE and immunoblotting suggested that the degradation of milk proteins including β-LG during yogurt manufacturing was not very extensive. These results suggest that yogurts contain factor(s) which interfere some reactions of inhibition ELISA. β-LG was also detected in cheeses, though the level was lower than that of milks. Though milk proteins were degraded most extensively in Roquefort cheese, its β-LG level was the highest. Among them, processed cheese had the lowest amount of β-LG, followed by Emmental cheese. These results suggest that an appropriate application of specific bacteria is useful for the preparation of low allergenic dairy products.
Sardine moist meals were inoculated with Aspergillus oryzae IFO 4202 seed and fermented. Accompanying the growth of the fungus, the chemical composition of the meals significantly changed during incubation. The fermentation contributed to antioxidation of lipids and reduction of histamine. Glucose supplement during fermentation was effective in inhibiting the production of volatile basic nitrogenous compounds. Fermented meals maintained superior quality of the proteins, protecting amino acid residues during incubation. The initial bacterial cell counts in meals were 3×102 CFU/g and reached 108 CFU/g in 72-h incubation. The Gram-negative rod-shaped bacteria, Pseudomonas spp., Moraxella spp. and Acinetobacter spp., were predominant in the initial meals. Gram-positive bacteria, especially Micrococcus spp., gradually became predominant during incubation. Fermentation and glucose supplement enhanced this predominancy of Micrococcus spp. during incubation. Fermentation with Aspergillus oryzae in the presence of glucose was considered to be effective for improvement of the chemical, nutritional and microbiological quality of fish meals.
Refined, bleached and deodorized palm oil, its purified palm triacylglycerol (PTG), palm olein (PO), palm stearin (PS) and high melting palm stearin (HMPS) fractions as well as randomized palm oil (RP) and its high melting randomized palm stearin (HMRPS) fractions were solidified at 5°C and kept isothermally at 10, 20 and 30°C for 60 days. X-ray diffraction showed that PTG was in β' form crystals, while palm oil and RP were in both α- and β' forms at 5°C. In HMPS and HMRPS, the higher percentage of β-transformation was observed with a higher content of trisaturated triacylglycerols and at a higher temperature. RP transformed from β' to the intermediate form crystals during prolonged storage. Other fats were stable in β' form crystals. Palm oil, RP, HMPS and HMRPS exhibited long-spacing values between those of tripalmitin and tristearin in α, β' and β modifications, respectively. This confirms that palm oil and its modified oils form a double-chain-length conformation.
An antioxidant was isolated from the peel and juice of lemon fruit (Citrus limon BURM. f.). It was identified as eriocitrin (eriodictyol 7-rutinoside) of the flavanone glycoside by HPLC, 1H-NMR and 13C-NMR analyses. The purified eriocitrin was readily soluble in water, methanol, and ethanol. A water solution of 0.05% eriocitrin was weakly acidic (pH 4.2). Eriocitrin was found to be stable even at high temperature (121°C, 15 min) in acidic solution (pH 3.5). The distribution of eriocitrin in citrus fruits was found to be especially abundant in lemons and limes, however, it was scarcely found in other citrus fruits. In the case of lemon fruit, eriocitrin was primarily distributed in the peel (about 1,500 ppm) composed of the albedo (mesocarp), flavedo (epicarp), and pulp vesicles. It was also significantly present in the juice (about 200 ppm) but was not detected in the seed. Two varieties of lemon fruits, eureka and lisbon, almost had the same eriocitrin content. The antioxidative activity of eriocitrin in the linoleic acid autoxidation system was equal to that of α-tocopherol, and it was enhanced when used together with citric acid. The eriocitrin had a synergistic effect on α-tocopherol.
Headspace gas chromatography (GC) analysis was used on three brands of Philippine fish sauces (patis) with a non-adjusted pH and pH 11.0. Under alkalized conditions, large amounts of trimethylamine and dimethyl disulfide were detected in samples A and B. Since the pH value of sample B was 0.3 unit higher than sample A, the volatilities of these two compounds were estimated to be about 2 times higher in sample B than in sample A. This estimation could explain the good, fishy smell of sample A and the very fishy and disagreeable smell of sample B. Sample C also included both compounds at low levels, but had higher amounts of pyrazines as compared to samples A and B. The burnt and sweet smell of sample C could be attributed to these compounds combined with large amounts of ketones and alcohols.
A trial device was made to measure the buffer capacity of foods using a personal computer. This device differs from the conventional analog-treated buffer capacity apparatus, so that the buffer capacity of dilute samples, such as 10-4 mol l-1, can be measured with high stability. The buffer capacity of water is subtracted automatically from that of the sample. The output signal is automatically converted to the buffer capacity value, so that the data obtained can be easily treated. Thus buffer capacity measurement becomes an easy determination.
Igisu-ryôri was prepared with the seaweed Amikusa (Ceramium boydenii). Amikusa was boiled and dissolved in the rice bran water extracts, and the sol was coagulated by cooling. Major inorganic ions contained in the rice bran water extracts were K+, Mg2+, Ca2+, and PO43-. The effects of metallic cations on the gelling properties of Amikusa were examined by dissolving Amikusa in a solution of KCl, MaCl2 or CaCl2 containing 0.06% acetic acid during the boiling process. The increases in the concentration of KCl correlated with the increased Amikusa gel strength, but MaCl2 and CaCl2 had no significant effect. Amikusa was readily dissolved by NaH2PO4 or Na-phytate solution, which are compounds of phosphoric acid, but a gel did not form unless KCl was added to it. These results indicated that during the process of boiling the seaweed in the rice bran water extracts, the phosphoric acid radical of phytic acid affected the solubility of the seaweed, and the sol changed to a gel by cooling in the presence of K+.
The inhibitory effects of some constituents which were previously isolated from the MeOH extract of Foeniculi Fructus (Fruit of Foeniculum vulgare MILLER) were investigated on the oxidation of linoleic acid and on the activation of inactive hyaluronidase induced by compound 48/80. Among the test compounds, six stilbene trimers, miyabenol C, cis-miyabenol C, foeniculoside I, foeniculoside II, foeniculoside III and foeniculoside IV, exhibited greater antioxidative activities than BHA. Furthermore, miyabenol C and cis-miyabenol C showed strong hyaluronidase inhibitory effects.
We assessed the inhibitory effects of curcumin and its chemically modified homologues against H2O2-induced cytotoxicity toward Chinese hamster lung fibroblasts V79 cells with a colony formation assay. Among 4 curcuminoids, dihydroxycurcumin and dihydroxytetrahydrocurcumin suppressed H2O2-induced cytotoxicity. On the contrary, neither curcumin nor tetrahydrocurcumin showed any suppressive effects. These results support our empirical rule that the o-dihydroxy (catechol) moiety is essential for the inhibitory effects.
The inhibitory effect of bean extracts (Phaseolus vulgaris L.), which showed antioxidative activity on mushroom tyrosinase activity, was investigated. A significant inhibitory effect was achieved by the extracts prepared from colored bean seed coats. This finding indicates that the pigments contained in the seed coats are strongly associated with the inhibition of tyrosinase, therefore, the inhibitory effect of three anthocyanins isolated from red and black beans as antioxidants and their aglycons on tyrosinase activity was determined. Cyanidin 3-O-β-D-glucoside and cyanidin were the best inhibitors of tyrosinase activity. These results indicate that significant inhibitory activity is achieved by a structure which has two hydroxyl groups on the B-ring.