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At least 1,711 records · Page 95Linked to original sources
PubMed2006

Sourdough products for convenient use in baking.

Sourdough fermentations require a specific knowledge on the effects of process parameters, raw materials and micro-organisms in order to obtain a specific, reproducible sourdough and bread quality. This knowledge is not necessarily available in bakeries. Sourdough starter cultures, either active sourdoughs (Reinzuchtsauerteig) or freeze-dried micro-organisms are used to start sourdough fermentation with the required micro-flora. As sourdough fermentation is a labour-intensive and a time-consuming process, a growing demand for convenient products arised early. First organic acids (lactic acid, acetic acid, citric acid) and mixtures thereof came in use. These agents were used directly without or in combination with a sourdough; however, flavour and taste of the resulting breads were unsatisfactory. Based on modified and optimized traditional sourdough processes, dried, pasty and liquid sourdoughs were developed. Companies which produce such ready-to-use products, claim for a convenient, direct production of baked goods in constant quality, in combination with all advantages of a biological sourdough fermentation, e.g. flavour and taste, fresh keeping and prolonged microbial shelf-life. Currently, a broad variety of sourdough products with different fermented cereals is available on the market. In order to obtain a stable product, it is a necessity to inactivate the sourdough micro-biota by e.g. pasteurization, drying or autosterilization.

Bread↗
PubMed2005

Fatty acid composition, cell morphology and responses to challenge by organic acid and sodium chloride of heat-shocked Vibrio parahaemolyticus.

Vibrio parahaemolyticus 690, a clinical strain, was subjected to heat shock at 42 degrees C for 45 min. The fatty acid profile and recovery of the heat-shocked cells of V. parahaemolyticus on TSA-3.0% NaCl, APS agar (Alkaline peptone salt broth supplemented with 1.5% agar) and TCBS (Thiosulfate-citrate-bile salts-sucrose agar) were compared with those of the nonheat-shocked cells. Furthermore, the morphology of V. parahaemolyticus and survival in the presence of various organic acids (25 mM acetic acid, lactic acid, citric acid or tartaric acid) and NaCl (0.1% and 20.0%) as influenced by heat shock treatment were also investigated. It was found that heat shock caused a change in the proportions of the unsaturated and saturated fatty acid. The ratio of saturated fatty acids to unsaturated fatty acids observed on heat-shocked V. parahaemolyticus cells was significantly (p<0.05) higher than that on the control cells. Extensive cell-wall pitting and cell disruption, representing cell-surface damage, were also observed on the cells which were subjected to heat shock treatment. Recovery of heat-shocked cells of V. parahaemolyticus was significantly less on TCBS and APS agar than on TSA-3.0% NaCl. Heat shock decreased the tolerance of V. parahaemolyticus to organic acids. The extent of decreased acid tolerance observed on heat-shocked cells varied with the organic acid tested. While heat shock increased the survival of V. parahaemolyticus in the presence of 0.1% NaCl and made the test organism more susceptible to 20.0% NaCl than the control cells.

Acids↗
PubMed2006

Computer aided boar semen motility analysis for cereulide detection in different food matrices.

Computer Aided Semen Analysis (CASA) study of the boar semen motility has been demonstrated to be an appropriate assay for detection of cereulide (Bacillus cereus emetic toxin). Application of the boar semen bio-assay to detect cereulide directly in foods requires investigation of potential interference of food components, preservatives and other microbial and chemical food contaminants with the bio-assay. Current study provides evidence that none of included Staphylococcus aureus enterotoxins A, B, C and D nor B. cereus Hemolysin BL (HBL) and non-hemolytic enterotoxin (NHE) and three mycotoxins (Sterigmatocystin, Fumonisin B1 and Patulin) exhibited a toxic impact on semen progressive motility. Aflatoxin M1, M3 and zearalenone impaired semen motility only at concentrations (0.004 mg ml(-1), 0.1 mg ml(-1) and 10 mg ml(-1), respectively) much higher than those found in foods and those permitted by legislation, in comparison to cereulide which induces motility cease at concentrations lower than 20 ng ml(-1). Ten commonly used preservatives, namely potassium sorbate, sodium benzoate, (DL) malic acid, citric acid, (L+) tartaric acid, acetic acid, (DL) lactic acid, (L+) ascorbic acid, sodium chloride and sucrose induced no cease in spermatozoa motility even at preservative concentrations higher than permitted by legislation. Dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and acrylamide had no acute effect on spermatozoa motility at concentrations of 500 and 10,000 mg ml(-1), respectively. Robustness of computer aided boar semen motility analysis, tested with 14 different foods inoculated with cereulide producing B. cereus, showed distinct cereulide production in seven samples (although B. cereus growth to counts higher than 8 log CFU g(-1) was noted in 11 samples), in amounts close to those reported in foodborne outbreaks. Test evaluation in 33 samples suspected to hold cereulide showed actual cereulide presence in ten samples and no interference of food matrix with the assay.

Animals↗
PubMed2004

Cyclosporin A-induced changes in endogenous metabolites in rat urine: a metabonomic investigation using high field 1H NMR spectroscopy, HPLC-TOF/MS and chemometrics.

The model nephrotoxin cyclosporin A was administered to male Wistar-derived rats daily for 9 days at a dose level of 45 mg/kg per day. Urine samples were collected daily and the excretion pattern of low molecular mass organic molecules in the urine was studied using 1H NMR spectroscopy and HPLC-TOF/MS. Distinct changes in the pattern of endogenous metabolites, as a result of the daily administration of cyclosporin A, were observed by 1H NMR from day 7 onwards. The NMR-detected markers included raised concentrations of glucose, acetate, trimethylamine and succinate and reduced amounts of trimethylamine-N-oxide. In parallel studies by HPLC-TOF/MS a reduction in the quantities of kynurenic acid, xanthurenic acid, citric acid and riboflavin present in the urines was noted, together with reductions in a number of as yet unidentified compounds. In addition, signals resulting from the polyethylene glycol, present in the dosing vehicle, and cyclosporin A metabolites were detected by MS. However, these were excluded from the subsequent multivariate data analysis in order to highlight only changes to the endogenous metabolites. Analysis of both the 1H NMR and HPLC-MS spectroscopic data using pattern recognition techniques clearly identified the onset of changes due to nephrotoxicity.

Animals↗
PubMed2000

Gas chromatographic-mass spectrometric analysis of acids and phenols in distilled alcohol beverages. Application of anion-exchange disk extraction combined with in-vial elution and silylation.

A GC-MS protocol for profiling spirits, based on 19 acids and phenolic compounds, has been proposed and evaluated. The method combined a simple preconcentration procedure based on solid-phase (anion-exchange) disk extraction, and in-vial elution and silylation of the analytes. The derivatized extract was directly injected into the GC-MS system. These analytes were: C6, C8, C10, C12 acids, pyruvic acid, 2-furoic acid, succinic acid, fumaric acid, glutaric acid, lactic acid, glycolic acid, malic acid, tartaric acid, citric acid, vanillin, syringaldehyde, coniferaldehyde, vanillic acid and gallic acid. The profiles of six different spirits were found reproducible from day-to-day with <20% RSD for measurements of most of the analytes at different concentrations. Recoveries of individual analytes appear to be affected by the level of tannins in the spirits, and they varied from sample to sample. The method of standard addition was used to quantify age-related analytes. Good linearity of response with correlation coefficients in the range of 0.992-0.999 was obtained. The results of the study indicate that for spirits of the same brand but of different ages, the amounts of these analytes appear to increase with the ageing period.

Acids↗
PubMed2001

Efficient gene delivery via non-covalent complexes of folic acid and polyethylenimine.

Polyethylenimine (PEI) is a cationic polymer capable of delivering DNA molecules into cultured mammalian cells as charge complexes. The application of PEI polyplexes in gene therapy, however, is hampered by the sensitivity of its transfection activity to the presence of serum. We found that folic acid, in a variety of cell lines, significantly enhanced PEI-mediated transfection activity in the presence of serum, whether the folic acid was added during or after PEI/DNA polyplex formation. The increase in activity could not be produced with other anionic compounds such as cholic acid, citric acid, EDTA, or glutamic acid. This novel formulation provides a reliable, low-cost, and highly efficient method for delivery of genes and may have applications in gene therapy.

DNA↗
PubMed1994

[Physicochemical interactions and mode of storage of Diprivan].

Only few publications consider physio-chemical interactions and stability of propofol. On the basis of current experience, this agent is safe for use in polypropylene or polypropylene/polystyrene syringes, diluted 1 in 5 in 5% dextrose if necessary. The potential hazards are as follows: 1. Propofol may undergo oxidation when not stored under nitrogen, or when in contact with oxidizing agents (active ingredients or excipients of other preparations). 2. The emulsion may be destabilised by contact with mineral or organic cations (calcium, magnesium, dibasic amino acids etc.) or acids (citric acid etc.). 3. Losses of propofol may occur by adsorption-diffusion (surface adherence combined with penetration of plastic material) during storage in PVC bags or during administration by means of PVC infusion sets. Most of these hazards have still to be evaluated under controlled conditions.

Drug Interactions↗
PubMed2001

Characterization of cigar tobaccos by gas chromatographic/mass spectrometric analysis of nonvolatile organic acids: application to the authentication of Cuban cigars.

A reliable method based on gas chromatographic/mass spectrometric (GC/MS) profiling of nonvolatile organic acids is described for the characterization of cigars. The method involves an aqueous extraction of ground tobacco and selective isolation of the acids by simply stirring strong anion exchange (SAX) disks in the aqueous tobacco extract. The acids are then directly silylated on the disk with N-methyl-N-trimethylsilyl-trifluroacetamide (MSTFA) in acetonitrile in an autosampler vial. Elution of the derivatized acids in situ allows the sample to be directly analyzed by GC/MS without further sample handling. Compared to the conventional disk-extraction technique using a vacuum manifold, this method is much less labor intensive, and is desirable for multiple sample analysis. Nicotinic acid, succinic acid, glyceric acid, malic acid, pyroglutamic acid, threonic acid, citric acid, uracil, and an unidentified acid were reproducibly quantified in tobacco samples. Principal component analysis (PCA) of the acid profiles of the filler tobaccos of 18 Cuban cigars and 31 non-Cuban cigars shows separation of the two groups, indicating that the acid profiles are potentially useful in the authentication of Cuban cigars.

Carboxylic Acids↗
PubMed2004

2. In vivo nonvolatile release during eating of a model cheese: relationships with oral parameters.

This study deals with the release kinetics of nonvolatile compounds (NVC) (leucine, phenylalanine, glutamic acid, citric acid, lactic acid, propanoic acid, sodium, potassium, calcium, magnesium, chloride, and phosphates) during the eating of a model cheese and the relationships to some oral (salivary and masticatory) parameters. The aroma release has previously been characterized in similar conditions [Pionnier, E.; Chabanet, C.; Mioche, L.; Le Quéré, J.-L.; Salles, C. J. Agric. Food Chem. 2004, 52, xxx-xxx (1)]. Saliva samples were collected from the tongues of eight assessors at different times during and after the chewing sequence. Atmospheric pressure ionization-mass spectrometry and/or high-performance liquid chromatography analyses have been performed on these samples in order to quantify the 12 NVC released in saliva. The maximum concentration (C(max)) in saliva varied significantly according to the compound. However, there was no significant effect of the compound on the time to reach maximum concentration (T(max)). Interindividual differences were observed for most of the parameters and for all of the NVC studied. The parameters extracted from the release profiles of the NVC were closely correlated. High T(max) and AUC (area under the curve) values could be related to high chewing time and low saliva flow rates, low chewing rates, low masticatory performances, and low swallowing rates.

Amino Acids↗
PubMed2006

Quantitative studies, taste reconstitution, and omission experiments on the key taste compounds in morel mushrooms (Morchella deliciosa Fr.).

Sensory-directed fractionation of an aqueous extract prepared from morel mushrooms led to the identification of gamma-aminobutyric acid as the chemical inducer of the mouth-drying and mouth-coating oral sensation imparted by morels. Additionally, L-glutamic acid, L-aspartic acid, succinic acid, and the previously unknown (S)-malic acid 1-O-beta-D-glucopyranoside, coined (S)-morelid, were detected as additional important umami-like taste compounds. To further bridge the gap between pure structural chemistry and human taste perception, 33 putative taste compounds were quantified in an aqueous morel extract and then rated for their taste contribution on the basis of dose-over-threshold factors. To confirm these quantitative results, an aqueous taste reconstitute was prepared by blending aqueous solutions of 16 amino acids, 6 organic acids, 3 purines, 4 carbohydrates, 3 minerals, and (S)-morelid in their "natural" concentrations. Triangle tests revealed that the taste profile of this biomimetic organoleptic cocktail did not differ significantly from the taste profile of authentic morel extract. To finally narrow down the number of key taste compounds, taste omission experiments were performed demonstrating that (S)-morelid together with L-glutamic acid, L-aspartic acid, malic acid, citric acid, acetic acid, and gamma-aminobutyric acid are the key organoleptics of morel extract. Moreover, sensory experiments with model solutions showed that (S)-morelid not only imparts a sour and umami-like taste but is able to amplify the taste activity of monosodium glutamate, as well as sodium chloride, solutions.

Adult↗
PubMed1999

Chemistry, biochemistry, nutrition, and microbiology of lysinoalanine, lanthionine, and histidinoalanine in food and other proteins.

Heat and alkali treatments of foods, widely used in food processing, result in the formation of dehydro and cross-linked amino acids such as dehydroalanine, methyldehydroalanine, beta-aminoalanine, lysinoalanine (LAL), ornithinoalanine, histidinoalanine (HAL), phenylethylaminoalanine, lanthionine (LAN), and methyl-lanthionine present in proteins and are frequently accompanied by concurrent racemization of L-amino acid isomers to D-analogues. The mechanism of LAL formation is a two-step process: first, hydroxide ion-catalyzed elimination of H(2)S from cystine and H(2)O, phosphate, and glycosidic moieties from serine residues to yield a dehydroalanine intermediate; second, reaction of the double bond of dehydroalanine with the epsilon-NH(2) group of lysine to form LAL. Analogous elimination-addition reactions are postulated to produce the other unusual amino acids. Processing conditions that favor these transformations include high pH, temperature, and exposure time. Factors that minimize LAL formation include the presence of SH-containing amino acids, sodium sulfite, ammonia, biogenic amines, ascorbic acid, citric acid, malic acid, and glucose; dephosphorylation of O-phosphoryl esters; and acylation of epsilon-NH(2) groups of lysine. The presence of LAL residues along a protein chain decreases digestibility and nutritional quality in rodents and primates but enhances nutritional quality in ruminants. LAL has a strong affinity for copper and other metal ions and is reported to induce enlargement of nuclei of rats and mice but not of primate kidney cells. LAL, LAN, and HAL also occur naturally in certain peptide and protein antibiotics (cinnamycin, duramycin, epidermin, nisin, and subtilin) and in body organs and tissues (aorta, bone, collagen, dentin, and eye cataracts), where their formation may be a function of the aging process. These findings are not only of theoretical interest but also have practical implications for nutrition, food safety, and health. Further research needs are suggested for each of these categories. These overlapping aspects are discussed in terms of general concepts for a better understanding of the impact of LAL and related compounds in the diet. Such an understanding can lead to improvement in food quality and safety, nutrition, microbiology, and human health.

Alanine↗
PubMed1980

Phospholipids as the molecular instruments of ion and solute transport in biological membranes.

Partition studies have established that phospholipids generally have the capabilities to mediate the transmembrane transport of the full range of ions and solutes that physiologically cross biological membranes. The list of transportable species includes cations, anions, amino acids, citric acid cycle intermediates, nucleotides, and sugars. Phospholipid-mediated transport can be readily modulated by altering the phospholipid mixture or by addition of detergents, nucleotides, divalent metals, proteins, peptides, or ring compounds. Containment of phospholipid within channels in protein appears to be the precondition for the formation of the micellar structure requisite for solute transport. Phospholipid-mediated transport is postulated to be a central feature of energy coupling, membrane-spanning systems, and membrane-bound, phospholipid-requiring enzymes.

Biological Transport↗
PubMed1976

Preferences by northern grasshopper mice for solutions of sugars, acids, and salts in Richter-type drinking tests.

Taste preferences, as measured in 48-hour, Richter-type drinking tests (test solution opposite distilled water), were determined for northern grasshopper mice (Onychomys leucogaster, ssp. breviauritus). The Ss were nine males and nine females which were individually housed within an environmental chamber. The test solutions were prepared from five sugars (fructose, glucose, lactose, maltose, sucrose) three salts (magnesium sulfate, potassium chloride, sodium chloride), and two acids (citric acid and hydrochloric acid). In randomly assigned order, each sugar and each salt solution was presented at five molar concentrations, and each acid was paired with distilled water at six levels of pH. Strong drinking preferences were shown for all concentrations of the sugars above .05-.10 M, and sugars ranked in order of preference as follows: Maltose = sucrose greater than glucose = fructose greater than lactose. Preferences were also shown for hypotonic concentrations of NaCl. The other salts and both acids, however, were indifferently preferred at low concentrations and were rejected at the higher concentrations. Taste preferences by grasshopper mice for these chemicals were similar to those exhibited by Monogolian gerbils tested with the same items. The similar patterns of preference shown by New World cricetid rodents (grasshopper mice) and Old World cricetid rodents (gerbils) suggest that conclusions concerning disparity in taste sensibilities among animal forms may be premature.

Acids↗
PubMed2003

Taste perception with age: generic or specific losses in supra-threshold intensities of five taste qualities?

The influence of ageing on supra-threshold intensity perception of NaCl, KCl, sucrose, aspartame, acetic acid, citric acid, caffeine, quinine HCl, monosodium glutamate (MSG) and inosine 5'-monophosphate (IMP) dissolved in water and in 'regular' product was studied in 21 young (19-33 years) and 21 elderly (60-75 years) persons. While the relative perception (intensity discrimination) seems to be remarkably resistant to the effect of ageing, the absolute perception (intensity rating) decreased with age for all tastants in water, but only for the salty and sweet tastants in product. When assessed while wearing a nose clip, only the perception of salty tastants was diminished with age. The slopes of the psychophysical functions were flatter in the elderly than in the young for the sweet, bitter and umami tastants in water, and for the sour tastants in product only. The age effects found were almost exclusively generic and never compound-specific within a taste. This study indicates that the relevance of determining intensities of tastants dissolved in water for the 'real life' perception of taste in complex food is rather limited.

Adult↗
PubMed1993

Evaluation of potential strontium chelators in an octanol-water system.

90Sr has a physical half-life of sufficient duration to make it a potentially dangerous contaminant from nuclear accidents and radioactive wastes. In the present study, the efficacy of 16 compounds as potential chelators of strontium was tested in vitro. Strontium solubilization from strontium carbonate and its distribution in an octanol-water system (Do/w) was determined in the absence and presence of alpha-ketoglutaric acid, Kryptofix 222, ethylenglycol-bis-(beta-amino-ethylether)-N,N-tetraacetic acid, diethylentriamine pentaacetic acid, Kryptofix 5, disodium chlodronate, disodium ethidronate, oxaloacetic acid, fumaric acid, D-gluconic acid, succinic acid, citric acid, D,L-2,3-diaminopropionic acid, 1,1-cyclohexanediacetic acid, tartaric acid, and trans-1,2-cy-clohexanediol. Kryptofix 222 and Kryptofix 5 significantly increased solubilized strontium, suggesting strontium chelation potential. Since in previous in vivo studies both compounds were also effective in the removal of strontium following internal contamination, it is concluded that the octanol-water system may be useful screening compounds with strontium chelation potential.

Bridged Bicyclo Compounds↗
PubMed1994

Acid pH crystallization of the basic protein lysin from the spermatozoa of red abalone (Haliotis rufescens).

A new crystal form of dimeric red lysin, a distinctly basic protein (M(r) = 16 070) from the red abalone (Haliotis rufescens), has been obtained using ammonium sulfate as precipitant with a sodium citrate-boric acid-citric acid buffer at pH 4.5. The acid pH crystal form resulted from a study aimed at developing conditions favorable to the sitting-drop vapor-diffusion crystallization of other abalone lysins which do not crystallize at neutral or basic pH conditions. The space group is P222(1) with cell dimensions a = 51.2, b = 47.0, c = 123.8 A and two molecules per asymmetric unit.

Journal Article↗
PubMed2005

Effect of immersion solutions containing enterocin AS-48 on Listeria monocytogenes in vegetable foods.

The effect of immersion solutions containing enterocin AS-48 alone or in combination with chemical preservatives on survival and proliferation of Listeria monocytogenes CECT 4032 inoculated on fresh alfalfa sprouts, soybean sprouts, and green asparagus was tested. Immersion treatments (5 min at room temperature) with AS-48 solutions (25 microg/ml) reduced listeria counts of artificially contaminated alfalfa and soybean sprouts by approximately 2.0 to 2.4 log CFU/g compared to a control immersion treatment in distilled water. The same bacteriocin immersion treatment applied on green asparagus had a very limited effect. During storage of vegetable samples treated with immersion solutions of 12.5 and 25 microg of AS-48/ml, viable listeria counts were reduced below detection limits at days 1 to 7 for alfalfa and soybean sprouts at 6 and 15 degrees C, as well as green asparagus at 15 degrees C. Only a limited inhibition of listeria proliferation was detected during storage of bacteriocin-treated alfalfa sprouts and green asparagus at 22 degrees C. Treatment with solutions containing AS-48 plus lactic acid, sodium lactate, sodium nitrite, sodium nitrate, trisodium phosphate, trisodium trimetaphosphate, sodium thiosulphate, n-propyl p-hydroxybenzoate, p-hydoxybenzoic acid methyl ester, hexadecylpyridinium chloride, peracetic acid, or sodium hypochlorite reduced viable counts of listeria below detection limits (by approximately 2.6 to 2.7 log CFU/g) upon application of the immersion treatment and/or further storage for 24 h, depending of the chemical preservative concentration. Significant increases of antimicrobial activity were also detected for AS-48 plus potassium permanganate and in some combinations with acetic acid, citric acid, sodium propionate, and potassium sorbate.

Bacteriocins↗
PubMed1981

Bacitracin and protease production in relation to sporulation during exponential growth of Bacillus licheniformis on poorly utilized carbon and nitrogen sources.

Growth of Bacillus licheniformis in a chemically defined medium containing glucose and ammonium chloride yielded a doubling time of 1.00 h. Examination of the culture during exponential growth revealed a lack of heat-resistant spores together with a complete absence of detectable concentrations of bacitracin or extracellular serine protease. Replacement of glucose as the sole carbon source by glycerol, pyruvic acid, citric acid, or lactic acid resulted in doubling times of 1.13, 2.00, 3.16, and 3.95 h, respectively. Bacitracin, protease, and heat-resistant spores were produced during exponential growth in amounts related to these doubling times. A qualitatively similar pattern was observed when ammonium chloride was replaced by sodium nitrate, alanine, or glutamic acid which gave doubling times of 1.65, 1.77, and 1.90 h, respectively. Protease, but not bacitracin, concentrations were substantially higher when the growth rate was restricted by use of poor nitrogen rather than poor carbon sources. The relationships between bacitracin production, protease production, and the sporulation process are discussed.

Amino Acids↗