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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The method previously developed by us for the pure-culture fermentation of brined cucumbers and other vegetables has been applied successfully to Manzanillo variety olives. Field-run grade fruit was processed first by conventional procedures to remove most of the bitterness. Then the relative abilities of Lactobacillus plantarum, L. brevis, Pediococcus cerevisiae, and Leuconostoc mesenteroides to become established and produce acid in both heat-shocked (74 C for 3 min) and unheated olives, brined at 4.7 to 5.9% NaCl (w/v basis), were evaluated. The heat-shock treatment not only proved effective in ridding the fruit of naturally occurring, interfering, and competitive microbial groups prior to brining and inoculation, but also made the olives highly fermentable with respect to growth and acid production by the introduced culture, particularly L. plantarum. Of the four species used as inocula, L. plantarum was by far the most vigorous in fermentation ability. It consistently produced the highest levels of brine acidity (1.0 to 1.2% calculated as lactic acid) and the lowest pH values (3.8 to 3.9) during the fermentation of heat-shocked olives. Also, L. plantarum completely dominated fermentations when used in two-species (with P. cerevisiae) and three-species (with P. cerevisiae and L. brevis) combinations as inocula. In contrast, when L. plantarum was inoculated into the brines of unheated olives it failed to become properly established; the same was true for the other species tested, but even to a more pronounced degree. L. brevis was the only species used that failed to develop in brines of both heat-shocked and unheated olives. Modification of the curing brine by the addition of lactic acid at the outset, either with or without dextrose, led to a much earlier onset of fermentation with accompanying acid development, as compared to treatments with dextrose alone or nonadditive controls. Reasons for the marked improvement of the fermentability of Manzanillo olives receiving the prebrining heat-shock treatment are discussed.
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PMID:Pure culture fermentation of green olives. 1634 74

The physicochemical properties of 8,8-methylmethine catechin-malvidin 3-O-glucoside isomers, commonly referred to as catechin-ethyl-malvidin 3-O-glucoside, have been studied in aqueous solutions and compared with those of the parent anthocyanin (malvidin 3-O-glucoside). The hydration and acidity constants (pKh and pKa) of the catechin-ethyl-malvidin 3-O-glucoside pigments and malvidin 3-O-glucoside were determined by UV-visible spectroscopic measurements. The ethyl-linked catechin-malvidin 3-O-glucoside pigments present higher stability toward hydration than the parent anthocyanin. The high resistance of these ethyl-linked pigments toward the hydration is related to the self-association that offers optimal protection from the nucleophilic attack of water. Moreover, the ethyl link may confer to the molecule enough flexibility to undergo intramolecular interaction, further protecting it from hydration and bisulfite discoloration. In the wine pH range (3.2-4.0), due to the low pKa and high pKh values, the ethyl-linked pigments are present as colored forms (flavylium cation and quinonoid bases).
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PMID:UV-visible spectroscopic investigation of the 8,8-methylmethine catechin-malvidin 3-glucoside pigments in aqueous solution: structural transformations and molecular complexation with chlorogenic acid. 1639 Jan 98

Chitosan, a binary heteropolysaccharide consisting of 2-acetamide-2-deoxy-beta-D-glucopyranose and 2-amino-2-deoxy-beta-D-glucopyranose residues linked in different proportions via beta-glycosidic bonds. The presence of a primary amino group in the chitosan structure allows for the synthesis of various derivatives. The procedure of obtaining activated N-hydroxysuccinimide esters with the use of lactobionic acid was applied to obtain galactosylated derivatives of low-molecular-weight chitosan with a substitution degree varying from 8 to 23%. The properties of these derivatives (viscosity, solubility, and biodegradability) were studied. These derivatives are well soluble at pH values greater than the acidity constant of amino groups of chitosan (6.5). Broadening the pH range towards increase and the presence of galactose residues allows these derivatives to be used in working with biological objects.
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PMID:[Galactosylated derivatives of low-molecular-weight chitosan: production and properties]. 1734 64

The relationships between grapevine (Vitis vinifera) vigor variation and resulting fruit anthocyanin accumulation and composition were investigated. The study was conducted in a commercial vineyard consisting of the same clone, rootstock, age, and vineyard management practices. The experimental design involved assigning vigor zones in two vineyard sites based upon differences in vine growth. Fruits and wines were analyzed by HPLC from designated vigor zones in 2003 and 2004. Average berry weight (grams), average dry skin weight (milligrams), degrees Brix, and pH were higher and titratable acidity (grams per liter) was lower in 2003 compared to 2004. In 2003, only the highest and lowest vigor zones had differences in berry weight, whereas there were no differences in 2004. In both years, high vigor zones had lower degrees Brix and higher titratable acidity (milligrams per liter). Accumulation of anthocyanins (milligrams per berry) was greater in 2003 compared to 2004. There was a trend for lower anthocyanin concentration (milligrams per berry) in high vigor zones in both years. In 2004 compared to 2003, there was a higher proportion of malvidin-3-O-glucoside and lower proportions of the other four anthocyanins (delphinidin-, cyanidin-, petunidin-, and peonidin-3-O-glucosides) found in Pinot Noir. In both years, site A had proportionally higher peonidin-3-O-glucoside and lower malvidin-3-O-glucoside than site B. Some of these differences may be related to the higher exposure and temperatures found in site B compared to site A and also in the low vigor zones.
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PMID:Influence of vine vigor on grape (Vitis vinifera L. Cv. Pinot Noir) anthocyanins. 1. Anthocyanin concentration and composition in fruit. 1763 33

The effect of glucose and 2-deoxy-D-glucose on pre-steady state kinetics of ATP hydrolysis by Na,K-ATPase has been investigated by following pH transients in a stopped-flow spectrophotometer. A typical pre-steady state signal showed an initial decrease then subsequent increase in acidity. Under optimal Na+ (120 mM) and K+ (30 mM) concentrations, magnitudes of both H+ release and H+ absorption were found to be approximately 1.0/ATPase molecule. The presence of 1 mM glucose significantly decreased H+ absorption at high Na+ concentrations, whereas it was ineffective at low Na+. H+ release was decreased significantly in the presence of 1 mM glucose at Na+ concentrations ranging from 30 mM to 120 mM. Similar to the control, K+ did not show any effect on either H+ release or H+ absorption at all tested combinations of Na+ and K+ concentrations. Pre-steady state H+ signal obtained in the presence of 2-deoxy-D-glucose did not vary significantly as compared with glucose. Delayed addition of K+ (by 30 ms) to the mixture (enzyme+120 mM Na++ATP+glucose) showed that only small fractions of population absorb H+ in the absence of K+. No H+ absorption was observed in the absence of Na+. Delayed mixing of Na+ or K+ did not have any effect on H+ release. Effect of 2-deoxy-D-glucose on H+ absorption and release was almost the same as that of glucose at all combinations of Na+ and K+ concentrations. Results obtained have been discussed in terms of an extended kinetic scheme which shows that, in the presence of either glucose or 2-deoxy-D-glucose, significantly fewer enzyme molecules reached the E-P(3Na+) stage and that K+ plays an important role in the conversion of E1.ADP.P(3Na+) to H+.E1~(3Na+) complex.
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PMID:Glucose regulation of pre-steady state kinetics of ATP hydrolysis by Na,K-ATPase. 1768 93

Four lactic acid bacteria (LAB), Lactobacillus paraplantarum KM, Enterococcus durans KH, Streptococcus salivarius HM and Weissella confusa JY, were isolated from humans and tested for their capabilities of converting isoflavone glucosides to aglycones in soymilk. Changes in growth, pH, and titratable acidity (TA) were investigated during fermentation at 37 degrees C for 12 h. After 6 to 9 h of fermentation, each population of 4 LAB reached 10(8) to 10(9) CFU/mL. The initial pH of 6.3 +/- 0.1 decreased while the TA of 0.13%+/- 0.01% increased as fermentation proceeded, resulting in the final range between 4.1 +/- 0.2 and 4.6 +/- 0.1 for pH and between 0.51%+/- 0.02% and 0.67%+/- 0.06% for TA after the 12 h of fermentation. The glucoside concentrations were significantly decreased in soymilks fermented with either L. paraplantarum KM, S. salivarius HM, or W. confusa JY with fermentation time (P < 0.05). L. paraplantarum KM was the best in percent conversion of glucosides to corresponding aglycones, resulting in 100%, 90%, and 61% hydrolysis of genistin, daidzin, and glycitin, respectively, in 6 h. Consequently, the aglycone concentrations in soymilk fermented with L. paraplantarum KM were 6 and 7-fold higher than the initial levels of daidzein and genistein, respectively, after 6 h of fermentation. Changes in the daidzin and genistin levels were not significant in soymilk fermented with E. durans KH. The rates of hydrolysis of glucosides varied depending on the species of LAB. Especially, L. paraplantarum KM seems to be a promising starter for bioactive-fermented soymilk based on its growth, acid production, and isoflavone conversion within a short time.
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PMID:Conversion of isoflavone glucosides to aglycones in soymilk by fermentation with lactic acid bacteria. 1799 40

The objective of this study was to understand the respective impact of ripening stage, temperature, and irradiance on seasonal variations of tomato fruit quality. During ripening, concentrations in reducing sugars, carotenes, ascorbate, rutin, and caffeic acid derivates increased, whereas those in titratable acidity, chlorophylls, and chlorogenic acid content decreased. Fruit temperature and irradiance affected final fruit composition. Sugars and acids (linked to fruit gustative quality) were not considerably modified, but secondary metabolites with antioxidant properties were very sensitive to fruit environment. Increased fruit irradiance enhanced ascorbate, lycopene, beta-carotene, rutin, and caffeic acid derivate concentrations and the disappearance of oxidized ascorbate and chlorophylls. Increasing the temperature from 21 to 26 degrees C reduced total carotene content without affecting lycopene content. A further temperature increase from 27 to 32 degrees C reduced ascorbate, lycopene, and its precursor's content, but enhanced rutin, caffeic acid derivates, and glucoside contents. The regulation by light and temperature of the biosynthesis pathways of secondary metabolites is discussed.
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PMID:How does tomato quality (sugar, acid, and nutritional quality) vary with ripening stage, temperature, and irradiance? 1823 31

Lactobacillus rhamnosus CRL981 showed the highest levels of beta-glucosidase and was selected to characterize this enzyme system, among 63 strains of different Lactobacillus species. The maximum activity was obtained at pH 6.4 and 42 degrees C. The enzyme showed weak resistance to thermal inactivation maintaining only 20% of the initial activity when it was exposed at 50 degrees C for 5 min. It also, showed stability when stored at 4 degrees C for 60 days. Afterwards, L. rhamnosus was evaluated for hydrolysis of isoflavones to aglycones, cell population, residual sugars and organic acid produced during fermentation on soymilk (37 degrees C for 24 h). Higher viable counts were obtained after 12 h of fermentation (8.85 log CFUml(-1)) followed by a drop of pH and an increase of acidity during fermentation due the production of organic acids. L. rhamnosus CRL981 was able to proliferate in soymilk and produce a high beta-glucosidase activity achieving a complete hydrolysis of glucoside isoflavones after 12 h of fermentation. The present study indicates that L. rhamnosus CRL981 could be used in the development of different aglycone-rich functional soy beverages.
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PMID:Aglycone production by Lactobacillus rhamnosus CRL981 during soymilk fermentation. 1926 78

Various carbohydrates have been added to the fluid cultures of different strains of spirochetes in order to determine the behavior of the latter toward the carbohydrates. In the present experiment, amygdalin, arabinose, beerwort, dextrin, galactose, glycogen, glucose, inulin, lactose, levulose, maltose, mannite, raffinose, saccharose, and starch were tested with seven strains of Treponema pallidum and one strain each of Treponema calligyrum, Treponema microdentium, Treponema mucosum, and Spirochata refringens. The results may be summarized as follows: 1. In the media containing glycogen and glucose, Treponema microdentium did not grow as vigorously as in other sugar media, and an earlier degeneration set in. One strain of the pallidum and the calligyrum and mucosum showed a poor growth in the glycogen medium. Similarly, there was little growth in the second transfer of these spirochetes in the glucose medium. The growth of the spirochetes in the media containing carbohydrates other than those Just mentioned was generally good, and no difference could be distinguished between these and the control cultures without any carbohydrate. The only phenomenon which might be interpreted as indicating a favorable influence of these media upon growth was the abundant growth of the mucosum, which showed uniform length, regular curves, and active motility somewhat better than in the sugar-free medium. 2. The height of acidity was found in the cultures containing glycogen and glucose in the microdentium, amounting to 0.1 N 4.8 cc. for 10 cc. of the fluid culture. In the other sugar media the acidity varied between 0.1 N 2 cc. and 0.1 N 3.2 cc. for the same amount. In the control cultures, the acidity fluctuated from 0.1 N 0.8 cc. to 0.1 N 2 cc. There was no visible alteration in the appearance of the media after the spirochetes had grown for 3 or 4 weeks. In the case of Treponema microdenlium, a slight opalescence developed in the glycogen and glucose media after several weeks' standing, but there was no precipitation or coagulation of the proteins of the culture media. 3. There was no unusual morphological change in the spirochetes grown in the media containing any of the carbohydrates employed. The only phenomena which should be mentioned are (a) the frequent presence of the terminal appendages (or projections) in the refringens, and in most of the pallidum strains, and (b) the appearance of minute, retractile spherical bodies along the side of the spirochetes in the microdenlium cultivated in the glucose or glycogen media. Judging from the earlier degeneration of the species in the above mentioned media, these peculiar bodies may be interpreted as indicating a phase of plasmoptysis associated with the unfavorable surroundings prior to degeneration. Experimental evidence was not found for considering these spherules as a resistant or spore form of the spirochete.
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PMID:THE INFLUENCE OF CARBOHYDRATES ON THE CULTIVATION OF SPIROCHETES. 1986 95

1. The optimum hydrogen ion concentration for growth of pneumococcus is pH 7.8. 2. In broth cultures growth of pneumococcus continues until a final hydrogen ion concentration of about pH 5.0 is reached, if sufficient fermentable carbohydrate' (above 0.4 per cent) is present. Apparently this acidity is sufficient in itself to stop growth. 3. If less carbohydrate is present in the medium growth ceases at a lower hydrogen ion concentration, apparently because of exhaustion of carbohydrate. If no carbohydrate is present save that extracted from the meat of which the broth is made (plain broth medium), growth initiated at pH 7.8 (optimum reaction) ceases at about pH 7.0. 4. If bacteria-free filtrates of plain broth cultures in which growth has ceased are readjusted to pH 7.8 and reinoculated with pneumococcus, no growth occurs unless carbohydrate is added. However, if bacteria-free filtrates of dextrose broth cultures in which growth has ceased (pH 5) are readjusted to pH 7.8 and reinoculated with pneumococcus growth occurs. 5. Cultures of pneumococcus with all the carbohydrates which were fermentable under the conditions used, namely maltose, saccharose, lactose, galactose, raffinose, dextrose, and inulin, gave identical results in the rate of reaction change, and final hydrogen ion concentration (pH 5.0) attained. 6. The different immunological types of pneumococcus, for the limited number of strains studied, behaved alike in fermenting the carbohydrates mentioned above.
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PMID:HYDROGEN ION CONCENTRATION OF CULTURES OF PNEUMOCOCCI OF THE DIFFERENT TYPES IN CARBOHYDRATE MEDIA. 1986 64


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