Antibacterial activities of six chitosans and six chitosan oligomers with different molecular weights (Mws) were examined against four gram-negative (
Escherichia coli,
Pseudomonas fluorescens,
...Salmonella typhimurium, and
Vibrio parahaemolyticus) and seven gram-positive bacteria (
Listeria monocytogenes,
Bacillus megaterium,
B. cereus,
Staphylococcus aureus,
Lactobacillus plantarum,
L. brevis, and
L. bulgaricus). Chitosans showed higher antibacterial activities than chitosan oligomers and markedly inhibited growth of most bacteria tested although inhibitory effects differed with Mws of chitosan and the particular bacterium. Chitosan generally showed stronger bactericidal effects with gram-positive bacteria than gram-negative bacteria in the presence of 0.1% chitosan. The minimum inhibitory concentration (MIC) of chitosans ranged from 0.05% to >0.1% depending on the bacteria and Mws of chitosan. As a chitosan solvent, 1% acetic acid was effective in inhibiting the growth of most of the bacteria tested except for lactic acid bacteria that were more effectively suppressed with 1% lactic or formic acids. Antibacterial activity of chitosan was inversely affected by pH (pH 4.5–5.9 range tested), with higher activity at lower pH value.
Background: The lifelong exposure of the population to acrylamide has raised concerns about the possible health effects of the chemical. Data on the extent of exposure to acrylamide and its primary ...metabolite, glycidamide, are needed to aid in the assessment of potential health effects. Objectives: The aim of this study was to assess human exposure to acrylamide and glycidamide in the general U.S. population through the measurement of hemoglobin adducts of acrylamide (HbAA) and glycidamide (HbGA). Methods: HbAA and HbGA were measured in 7,166 subjects from the National Health and Nutrition Examination Survey. Stratified HbAA and HbGA data were reported by sex, age groups, race/ethnicity (Mexican American, non-Hispanic black, non-Hispanic white), and smoking status based on serum cotinine levels. Covariate-adjusted geometric means for each demographic group were calculated using multiple regression analysis. Results: HbAA and HbGA levels ranged from 3 to 910 and from 4 to 756 pmol/g hemoglobin, respectively, with smokers having the highest levels overall. Tobacco smoke exposure in nonsmokers had a small but significant effect on HbAA and HbGA levels. Adjusted geometric mean levels for children 3-11 years of age were higher than for adults ≥ 60 years of age mean (95% confidence interval): HbAA, 54.5 (49.1-51.5) and HbGA, 73.9 (71.3-76.6) vs. HbAA, 46.2 (44.3-48.2) and HbGA, 41.8 (38.7-45.2). Levels were highest in Mexican Americans HbAA: 54.8 (51.9-57.8), HbGA: 57.9 (53.7-62.5), whereas non-Hispanic blacks had the lowest HbGA levels 43.5 (41.1-45.9). Conclusions: U.S. population levels of acrylamide and glycidamide adducts are described. The high variability among individuals but modest differences between population subgroups suggest that sex, age, and race/ethnicity do not strongly affect acrylamide exposure. Adduct concentration data can be used to estimate relative exposure and to validate intake estimates.
Physicochemical, binding, and antibacterial properties of chitosans prepared without and with deproteinization (DP) process (5, 10, 15, and 30 min at 15 psi/121 °C) were compared. Chitosan from DP 0 ...min had comparable nitrogen content, lower degree of deacetylation and solubility, but higher molecular weight and viscosity than chitosans from DP 5−30 min. The latter four chitosans showed differences only in molecular weight. Deproteinization treatment resulted in slightly decreased L* values and increased a* and b* values compared with those of DP 0 min. Chitosan from DP 0 min had comparable water and fat-binding capacity (FBC) except for chitosan from DP 15 min, which had a higher FBC but lower dye-binding capacity than those of the four chitosans from DP 5−30 min. The antibacterial activities of chitosans against seven different bacteria showed that the inhibitory effects varied with the deproteinization time and the particular bacterium. Keywords: Chitosan; deproteinization; physicochemical characteristics; binding capacity; antibacterial activity
Physicochemical characteristics and functional properties of five commercially available chitins and five chitosans were investigated. Physicochemical characteristics (nitrogen, ash, degree of ...deacetylation, bulk density, and viscosity) differed with products. In functional properties, dye binding capacity differed depending on the products, although average binding capacity (63%) of chitosans was higher than that (54%) of chitins. Water binding capacity ranged from 381 to 673% for chitins and from 458 to 805% for chitosans. Fat binding capacities of chitins were mostly similar (316−320%) except for one product (563%), whereas chitosans showed dissimilar binding capacities from 314 to 535%. However, significant correlations were observed between water binding capacity and bulk density (r = −0.89, P < 0.01) and between fat binding capacity and viscosity (r = 0.72, P < 0.05) of chitin products. Both water and fat binding capacity of chitosan products were significantly correlated positively with ash (r = 0.81, 0.80) and negatively with bulk density (r = −0.98, −0.95). Emulsifying capacity of egg yolk increased by addition of chitosan compared with the control. No differences in emulsifying capacity of chitosan products were observed at each concentration tested. Keywords: Chitin; chitosan; physicochemical characteristics; functional properties
Internal quality of eggs coated with chitosans prepared under various deproteinization (DP at 0, 5, 15 min) and demineralization (DM at 0, 10, 20, 30 min) times was evaluated. Chitosans prepared ...under DP 0 min/DM 30 min, DP 5 min/DM 30 min, and/or DP 15 min/DM 20 min conditions can be effectively used as an egg-coating material in preserving the internal quality of eggs compared with chitosan prepared under the DP 15 min/DM 30 min condition. The Haugh unit and yolk index values suggested that the chitosan-coated eggs can be preserved for at least 2 wk longer than the control noncoated eggs during 5 wk of storage at 25 degrees C.
Chitosan, a natural biopolymer derived by deacetylation of chitin, has been extensively used in biomedical, agricultural and food applications. The ultimate aim of research effort was to develop ...various economic/simplified chitosan production processes for particular food applications. Therefore, a set of experiments was designed to evaluate the effect of chitosans prepared under various deproteinization (DP) times (at 0, 5 and 15 min) and demineralization (DM) times (at 0, 10, 20 and 30 min) on the growth of soybean sprouts. Chitosan treatment increased the total weight of soybean sprouts by 10.7-13.8% compared with that of the control; the effectiveness of the chitosan treatment was independent of DP and DM times. The increase (12.7%) in the growth of soybean sprouts by chitosan prepared without DP and DM steps was noteworthy. This investigation demonstrates that the elimination of DP and DM steps or a reduction in the reaction time required for optimum DP and DM in the production of chitosan needs further studies before being considered for particular usages.
Summary
The potential of chitosan as a coagulant in commercial tofu preparation was investigated with six chitosans of different molecular weights using various treatments. The following optimum ...processing conditions for tofu preparation were proposed: chitosan with a molecular weight of 28 kDa; chitosan solution type, 1% chitosan/1% acetic acid; chitosan solution to soymilk ratio, 1 : 8; coagulation temperature, 80 °C; coagulation time, 15 min. However, the sensory quality of tofu was notably improved using a 1 : 1 mixture of 1% acetic acid and 1% lactic acid instead of 1% acetic acid alone as a chitosan solvent. Tofu prepared with chitosan had lower ash and higher protein content than those of commercial products tested. In storage tests, the chitosan‐tofu had a longer shelf‐life, about 3 days, than tofu made with CaCl2. This added shelf‐life is significant in view of the magnitude (366 000 tonnes year−1) of tofu produced from commercial tofu plants (1407 plants as of 1998) in Korea.
Volatile compounds were isolated from cooked spiny lobster (Panulirus argue) tail meat by vacuum simultaneous distillation-solvent extraction (V-SDE) and dynamic headspace sampling (DHS). Flavor ...dilution chromatograms of V-SDE and DHS extracts were similar with respect to predominant odorants. The compound 2-acetyl-1-pyrroline, having a nutty, popcorn-like odor, was the most intense odorant in both types of extracts. Other potent odorants included 2,3-butanedione (creamy, buttery), 3-(methylthio)propanal (potato-like, soy sauce-like), 2-acetyl-3-methylpyrazine (burnt, popcorn-like), trimethylamine (fishy, ammonia-like), 1-octen-3-one (earthy, mushroom-like), and (Z)-4-heptenal (rancid, boiled potato-like). Two unidentified compounds described as marine, leather-like, and lobster-like were of relatively low odor intensity
Deacetylation of chitin under autoclaving conditions (15 psi/121 °C) was evaluated for the preparation of chitosan under different NaOH concentrations and reaction times. Deacetylation was ...effectively achieved by treatment of chitin under elevated temperature and pressure with 45% NaOH for 30 min and a solids/solvent ratio of 1:15. Treated chitosan showed similar nitrogen content (7.42%), degree of deacetylation (90.4%), and molecular mass (1560 kDa) but significantly higher viscosity values (2025 cP) compared with those (7.40%, 87.6%, 1304 kDa, and 143 cP, respectively) of a commercial chitosan. Reduction of the solids/solvent ratio from 1:15 to 1:10 did not affect degree of deacetylation, viscosity, and molecular mass of chitosan. Keywords: Chitin; chitosan; deacetylation; autoclaving
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