Ferulic acid esterase activity arose in the ceca of rats that were fed on acid hydrolysate of refined corn bran. The main component of this hydrolysate was soluble ferulic acid arabinoxylan ester. In order to determine the relationship between the ferulic acid esterase activity and intestinal bacteria, the ferulic acid esterase activities from the four kinds of typical bacteria in the intestine were measured. Ferulic acid arabinose ester (LMW) and ferulic acid arabinoxylan ester (HMW) were used as substrates. The enzyme from Lactobacillus acidophilus exhibited the highest activity when LMW was used as a substrate. However, when HMW was used, all enzymes from these bacteria exhibited trace activities. At the same time, Bifidobacterium bifidum showed high xylanase and arabinofuranosidase activities. It was suggested that the xylanase and the arabinofuranosidase from bacteria such as B. bifidum attacked HMW and degraded it to lower molecules at first. The ferulic acid esterase from bacteria such as L. acidophilus might then act to release ferulic acid in the cecum.
Eggplant extract markedly inhibited melanogenesis in B16 mouse melanoma 4A5 cells (B16 cells). To clarify the characteristics of the melanogenesis inhibitor in eggplant, the effective fraction, P1, was separated from the eggplant extract by ammonium sulfate fractionation and Sephadex G-100 column chromatography. The P1 fraction from the eggplant contained 63% protein, 20% neutral sugar and 11% uronic acid. P1 was stable during heating at 60°C for 30 min, and the inhibitory effect remained stable after protease digestion. P1 weakly inhibited tyrosinase activity in crude B16 cell extract in vitro, and tyrosinase activity in B16 cells cultured with P1 was reduced. The regulation of tyrosinase activity in B16 cells was equal to melanogenesis suppression in B16 cells. These results show that the eggplant extract suppresses melanogenesis in B16 cells by regulation of tyrosinase.
The properties of protein adsorption and desorption of alumina ceramic membranes were investigated using several types of proteins. The effect of pH on the protein adsorption was studied by soaking the membrane in protein solution. For basic proteins, the amount of protein adsorbed increased at pHs lower than the isoelectric point due to an electrostatic interaction between the protein and the membrane. A single protein solution was filtered and the protein was adsorbed on the membrane. Most of the adsorbed protein was desorbed and concentrated by changing the ionic strength or pH of the filtered solvent, however, the protein remaining on the membrane was not washed out even by soaking in sodium lauryl sulfate (SDS) solution. The adsorption-desorption experiments were carried out using a binary protein solution of lysozyme and β-galactosidase of pH 3 for the adsorption step and phosphate buffer solution of pH 7 for the desorption step. During the adsorption step, β-galactosidase was adsorbed more than the lysozyme, however, the absolute adsorbed amount was smaller than that in the single protein solution of β-galactosidase since the adsorption site was partially occupied by lysozyme. β-Galactosidase was concentrated seven-fold in the permeate during the desorption step in the first 20 s, while the concentration of lysozyme was one-tenth of its original value.
The enzymatic degradation of sodium alginate was continuously carried out to effectively produce alginate oligosaccharides using immobilized alginate lyase in a CSTR (continuous stirred tank reactor) system. The alginate lyase was immobilized onto the chitosan beads and the reaction was operated at an initial alginate concentration of 10 g l−1 at 35°C and pH 7.0 under the dilution rate of 0.77 to 1.74 h−1. The degradation products mainly consisted of di-, tri-, tetra-, penta-, and hexasaccharides with the highest conversion of 0.34, with the volumetric production rate of the total oligosaccharides dependent on the dilution rate. The production process was mathematically modeled from the basic material balance and the rate equation, and showed agreement between the simulated and experimental results. The present reactor system was found to be effective for obtaining alginate oligosaccharides with a high production rate.
The effects of aged fermented bovine milk produced by a mixture of various lactic acid bacteria and a yeast, or a mixture of the lactic acid bacterium, Bifidobacterium longum, and a yeast on the proliferation activities of human carcinoma cells (DLD-1, MKN-1, and HL-60 cell lines) and human normal fibroblast cells (Fb) were investigated. Nonfermented bovine milk suppressed the proliferation activity in various degrees depending on the cell lines tested, suggesting that bovine milk may contain a component regulating in vivo proliferation of certain cells. The fermented milk produced by a mixture of various lactic acid bacteria and a yeast selectively reduced the proliferation activity of DLD-1 and MKN-1 cells. In contrast, the fermented milk produced by a mixture of B. longum and a yeast was selectively toxic to HL-60 cells, and cell proliferation activity was completely lost. Analysis of this cytotoxicity was revealed to be due to the induction of apoptosis which was demonstrated by the formation of apoptotic bodies and the fragmentation of DNA in treated cells. These findings strongly suggest that the cytotoxic factors affecting the viability of transformed and nontransformed cells are present in latent form in bovine milk, and these factors could be produced from milk by digestion using microbial enzymes.
Digalactosyldiacylglycerol (DGDG) and trigalactosyldiacylglycerol (TGDG) were extracted from pumpkin and then hydrolyzed to the corresponding monoacylglycerols by 1,3-specific lipase from Rhizopus arrhizus. The hydrolyzates from DGDG and TGDG were identified as digalactosylmonoacylglycerol (DGMG) and trigalactosyl-monoacylglycerol (TGMG) by TLC analysis, acid hydrolysis and GC analysis, respectively. The surface tensions of the aqueous DGMG and TGMG solutions significantly decreased up to 0.005% DGMG and TGMG, and then decreased slightly at more than that concentration. The foamabilities increased with the DGMG and TGMG contents. The foamabilities and the foaming stabilities of DGMG and TGMG were superior to those of the other commercial emulsifiers. The interfacial tensions at the water/kerosene interface of DGMG and TGMG significantly decreased up to 0.001% DGMG and TGMG, and then slightly decreased at more than that concentration. The types of water/kerosene (1:1, w/w) emulsions prepared with DGMG and TGMG were O/W, respectively. The creaming stabilities and the strength of the interfacial film of the emulsions increased with the DGMG and TGMG contents. The emulsifying properties of the DGMG and TGMG emulsions were almost equal to those of the commercial emulsifiers.
The tert-butylperoxyl radical (t-BuOO·) scavenging activities of ethanol extracts of 21 sweet potato cultivars with several flesh colors were examined using a tert-butyl hydroperoxide (t-BuOOH)/hemin/luminol system. Among them, sweet potato cultivars with purple flesh, which contained anthocyanins, had the highest t-BuOO· scavenging activities. Those cultivars with purple flesh also had the highest antioxidative activities against lipid peroxidation induced by auto-oxidation of linoleic acid. Most of the sweet potato cultivars with white, white-yellow, yellow and orange flesh had low t-BuOO· scavenging and antioxidative activities; however, some of them had higher activities. In all sweet potato cultivars tested, the t-BuOO· scavenging activities became higher with an increase in the total phenolic content.
We have identified two triterpene carboxylic acids of oleanolic acid and ursolic acid isolated from the leaves of loquat (Eriobotrya) by NMR spectroscopy. We have investigated the effects of oleanolic acid and ursolic acid on the growth of lymphoid leukemia Molt 4B cells and obtained results in which both compounds inhibited the proliferation of Molt 4B cells. In an in vitro experiment, ursolic acid inhibited ornithine decarboxylase (ODC) activity by 25.9% and 39.7% at the concentrations of 1 mM and 2 mM, respectively, while oleanolic acid inhibited ODC activity to a lesser extent than did ursolic acid. Both compounds slightly suppressed S-adenosylmethionine decarboxylase (AdoMetDC) activity. Polyamine contents were decreased in these compound-treated cells. These findings demonstrate that growth suppression of human Iymphoid Molt 4B cells by ursolic acid and oleanolic acid may result from the depletion of polyamines caused by the inhibition of ODC and AdoMetDC activities.
Lactococcus lactis IO-1 isolated in our laboratory produces a peptide antibiotic, a natural nisin variant, nisin Z. Nisin Z was heat stable at acidic pH and showed a bactericidal mode of action against an indicator strain, Bacillus subtilis C1. The effect of proteolytic enzyme treatment on the activity and the antimicrobial spectrum were tested. These results indicated nearly the same characteristics as those of nisin A. In this study, it was found that two nisin variants (nisin Z and nisin A) were practically inactivated by proteinase K and actinase E. Interestingly, nisin-producing strains, L. lactis IO-1 and L. lactis NCDO 497 (a nisin A producer) were sensitive to a high concentration of nisin variants including their own products. The growth of a Gram-negative bacterium, Escherichia coli, was also inhibited by a high concentration of nisin, although nisin producers and Gram-negative bacteria are generally resistant to nisin variants.
Attempts to find a solution to the problem of beer staling have been unremitting: hundreds of articles have been published during the last few years alone. This paper introduces recent developments in brewing science and discusses basic research into the formation of stale flavors, together with measures proposed and adopted to counter them. Included are advances made both in brewing technology and beer distribution systems, which help minimize staling, with an example of product temperature management used by a Japanese company.
The reduction of tetrazolium XTT with the Maillard reaction system containing various sugars or aldehydes and glycine was monitored and compared with the conventional indices of the Maillard reaction such as nitroblue tetrazolium (NBT) and dichlorophenolindophenol (DPI) reducibility, free hydroxymethylfurfural and browning. The change in XTT reducibility against the monosaccharide-glycine system showed a similar behavior as that of NBT and DPI reducibility, indicating that the Amadori product and reductones formed in the Maillard reaction may be involved in the reduction of XTT. In contrast, the XTT reducibility against the disaccharide-glycine system consisting of lactose, lactulose or cellobiose showed a different behavior from those indices. In the system, the reduction of XTT was caused by the substances which have a low reducibility of NBT. Such a property was recognized in some model systems, including the condensation reaction of D-glucosamine, that can form nitrogen-containing heterocyclic compounds such as pyrazinium and pyridinium. The condensation product of D-glucosamine rapidly lost the XTT reducibility with the addition of Cu2+. The phenomenon was also observed in the UHT-treated milk, and the decrease in the XTT reducibility during the storage was suggested to be due to the presence of Cu2+ in milk.
When cream puff paste (CPP) was baked after it was kept at 35°C for 3 h, it did not puff up as much as one baked just after preparation of the CPP. The optimum preparative method for CPP with the least deterioration during storage was found by carrying out random centroid optimization regarding 9 factors, such as the ratio of flour, shortening, yolk, egg white and water as ingredients, and the heating time at the first stage, the temperature of the heated mixture of water, shortening, and flour on the addition of the egg solution, and the time and temperature of the incubation of the yolk as preparative conditions. The optimum values of 18.0%, 14.7%, 13.4%, 25.4%, 28.5%, 106.5s, 53.9°C, 46.7 min, and 63.7°C were obtained, respectively. Each value except the time and temperature for incubating the yolk was similar to that in the standard preparative method of CPP, which brought about deterioration during storage. The incubation of the yolk at 63.7°C for 46.7 min caused a decreased in the specific activity of amylase in the yolk from 1.71±0.43 to 0.20±0.17 μg of maltose/mg of protein but did not affect proteins in the CPP.
Enriching the atmosphere of fermenting "dhool" (macerated leaf) with oxygen led to faster production of some black tea volatile flavor compounds (VFC). There was a general rise in the total amounts of the VFC with long fermentation duration irrespective of whether it was done under enriched oxygen atmosphere or ambient air. The rise was, however faster under enriched oxygen atmosphere than under ambient air. The rise was also faster in the group I VFC than the group II VFC leading to a general decline in the Flavor Index with long fermentation durations. For every fermentation duration, the sum of group I VFC was higher under enriched oxygen atmosphere than under ambient air fermentation. Such variations were only marginal in the group II VFC. As a result, fermentation under enriched oxygen atmosphere reduced the aroma quality of black tea despite increasing the total amounts of VFC. Generally, the VFC which are oxidative products of amino acids and unsaturated fatty acids degradation increased with fermentation durations, while the major terpene alcohols declined under both ambient air and enriched oxygen atmosphere fermentation conditions.
The influence of hop resins on the freeze-thawing resistance of Escherichia coli K-12 IFO3301 was investigated. When the freeze-thawing treatment of the strain was carried out in nutrient broth containing 0.01% of hop resins, a great decrease in the viable cell count was observed. Especially, the decrease in the count on the desoxycholate agar plate was remarkable, and no viable cells were found after 24-h freezing. Further, an extension of the lag phase was observed when the strain after freeze-thawing treatment was incubated in the nutrient broth. Namely, the freeze-thawing injury to the strain was greatly enhanced by the addition of the hop resins. It was thought that the effective utilization of hop resins for hygienic control of frozen foods is feasible.
It is well known that muscle is converted to meat as food during postmortem aging. Meat flavor as well as texture are improved during postmortem aging. The improvement of meat taste in flavor is involved in the increase in free amino acids and peptides in meats during postmortem aging. Especially, the increase in free amino acids is thought to contribute to the enhancement of brothy taste including umami, while the increase in peptides is responsible for giving mildness. The increase in peptides is caused by the action of cathepsins B and L, and calpains on muscle proteins, while the increase in free amino acids is caused by the action of aminopeptidases C, H and P on the peptides during postmortem aging.
This study was conducted to determine the reason why dried rice cakes for non-glutinous rice crackers (Senbei) often break in the production process. Breakage after drying at 40°C for 12 h was found to be due to milling and storage conditions of the rice flour. Gel permeation chromatography revealed that the molecular weight of starch decreased as the extent of breakage increased. Damage to rice flour starch differed according to the milling methods. When press roller milled rice flour was stored at 5-25°C, the activity of α-amylase increased as the temperature became higher. The total water-soluble carbohydrate content of dried rice cake may be a good criterion to judge the extent of breakage. Reduction of the molecular sizes of starch, due to milling and action of α-amylase, is considered to cause the breakage of dried rice cake.
Peptic globin digest (PG) was prepared from porcine blood globin, and the peptides were characterized by separation processes such as gel filtration chromatography, hydrophobic chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Aggregation of the peptides was indicated by high-performance liquid chromatography (HPLC). Two fractions (F1 and F2) were obtained from PG by gel filtration chromatography. Hydrophobic chromatography of fraction F1 was carried out, and a peak corresponding to the aggregate was found in fractions F1b-F1e. These fractions, which showed an aggregate peak by HPLC, were subjected to SDS-PAGE, and two major peptide bands with molecular weight of 5000 and 6000 were found. Amino acid sequence indicated the N-terminal amino acid of these peptides to be 42-47 (Phe-Asp) and 86-92 (Ala-Leu) of β-globin, respectively. Furthermore, it was predicted that the Mw 5000 and 6000 peptides may possibly be 42-85 (Mw 4749) and 86-141 (Mw 6117) of β-globin, respectively, based on the specificity of pepsin.
The adsorption isotherms of some dipeptides composed of un-ionizable side chains were measured at 25°C in a single component system, and all of them obeyed the Langmuir equation. The parameters obtained at pH 7 could be roughly correlated with the hydrophobic and steric parameters of constituent amino acids. To find a method for predicting the amount of dipeptide adsorbed under various conditions, the applicability of the Polanyi adsorption potential theory was examined. The amount of dipeptide adsorbed could be roughly estimated from the adsorption isotherms of the amino acids, although the estimation lacked strictness in a physical sense.
Relationship between the quality of shrimp cracker and the water activity (Aw) was studied by means of a sensory test. Crispness, odor, taste, and total acceptability decreased with the increase in water activity. Critical water activity, defined as a point where total acceptability became negative, was 0.35 Aw. Multiple regression analysis showed that crispness had great responsibility for total acceptability. Apparent breaking strength and breaking energy obtained by instrumental analysis increased with the increase in water activity within the range of 0 to 0.52 Aw. The relationship between the logarithmic value of breaking strength and the intensity of crispness indicated that the analysis of the breaking strength was a useful tool for quality evaluation of the shrimp cracker.
The odor components of six different non-salted fermented soybean products in different parts of the world, Natto (Japan), Thua-nao (Thailand), Pepo (Myanmar), Libi ippa (East Bhutan), Kinema (West Bhutan) and Daddawa (Nigeria) were compared. Especially, the composition of pyrazines contributing to Natto odor was examined in these products. The odor concentrates were prepared by the method using porous polymers and were analyzed by gas chromatography and gas chromatography-mass spectrometry. Pyrazines were considered to contribute to the characteristic odor of the non-salted fermented soybean products because the compounds were detected commonly in all the products except two types of Libi ippa. The total concentration of the pyrazines was lower in Libi ippa, Kinema, and Daddawa and higher in Thua-nao and Pepo when compared with that of Natto. The composition of the pyrazines depended on the products.
