Adsorption of glyphosate on goethite (alpha-FeOOH): surface complexation modeling combining spectroscopic and adsorption data

N-(phosphonomethyl)glycine (glyphosate, PMG) is the most widely used herbicide, and its adsorption onto soil minerals plays a significant role in its mobility and rate of degradation. In this work, we present the results of the first serious effort to find a realistic surface complexation modelthatfits both adsorption and total proton concentration data for PMG on the common soil mineral, goethite. Special attention was focused on making sure that the final model was in good semiquantitative agreement with previously reported X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopic measurements. Electrostatic effects were accounted for using the Basic Stern model, and the charges of the PMG-containing surface complexes were assumed to be distributed across the 0- and beta-planes. The reactions for the protonation of the goethite surface were described using the 1 pK model. We optimized on the intrinsic formation constants and the charge distributions of the complexes, as well as the initial total proton concentration (I = 0.1 M Na(NO3), 25.0 degrees C), and the following model was obtained. triple bond FeOH(0.5-) + H3L <==> triple bond FeHL(1.5-) + H(+) + H2O Log10beta = 4.70 +/- 0.08, Q0 = -0.18 +/- 0.02 triple bond FeOH(0.5-) + H3L <==> FeL(2.5-) + 2H(+) + H2O Log10beta = -3.9 +/- 0.1, Q0 = -0.7 +/- 0.1 Here, beta is the intrinsic formation constant, Q0 is the charge at the 0-plane, and the errors are reported as one standard deviation. The charge distributions of the complexes are rationalized by considering intramolecular hydrogen bonding between the protons of the amine group and both the phosphonate and carboxylate groups.     

Molecular docking and dynamic insights on the adsorption effects of soy hull polysaccharides on bile acids

Molecular docking is a powerful tool that visualises interactions between receptors and ligands. This technique and experimental studies were used to explore the adsorption effects of soy hull polysaccharides (SHP) on bile acids (BAs). Docking sites and interactions between SHP and six BAs (deoxycholic acid, lycholic acid, taurine cholic acid, chenodeoxycholic acid, glycocholic acid and glycodesoxycholic acid) were identified by molecular docking. The docking sites were mainly O and H atoms, and interaction forces were mainly facilitated by hydrogen bonds and hydrophobic interactions, with hydrogen bonds being the main bond type. BAs-binding studies, Fourier-transform infrared spectroscopy and zeta potential results showed that hydrogen bonding was the main force mediating SHP and BAs adsorption. The hydrogen bonding was positively proportional to the adsorption capacity of BAs and negatively proportional to the absolute value of zeta potential. The molecular dynamic simulation of glycocholic acid and SHP was also performed. Hydrogen bond spacing and root mean square deviation analyses indicated that the glycocholic acid and SHP combination was stable. This study has the significance of preventing cardiovascular diseases by revealing the adsorption effects of SHP on bile acids BAs.     

Inhibition of Staphylococcus aureus by oleuropein is mediated by hydrogen peroxide

The inhibition of Staphylococcus aureus by oleuropein is shown to be largely due to hydrogen peroxide production by oleuropein. The reaction is initiated by noninhibitory levels of hydrogen peroxide present as a result of tryptone oxidation in the underlying medium. Inhibition is abolished by catalase and anaerobic incubation conditions, and the effect of tryptone can be replicated by exogenous H2O2. S. aureus strains with reduced catalase activity show greater sensitivity to oleuropein. A mechanism for hydrogen peroxide production is proposed. Inhibition is not entirely due to H2O2, since some organisms with similar sensitivity to H2O2 as S. aureus were resistant to oleuropein, suggesting that there may be a cooperative effect between H2O2 and oleuropein itself.     

Zusammenhang zwischen Konformation der Glucopyranoseeinheiten und Molekülkonfiguration der Amylose

Relationship between the Conformation of the Glucopyranoside Units and the Molecular Configuration of Amylose. As a consequence of the tetrahedral valence angle as well as of the interactions between the  H and  OH groups attached to the C atoms the most probable form of D-glucopyranose is the Cl conformation. The rotation around the oxygen-bridge between the two glucopyranose units in maltose is hindered to such an extent that the existence only of that form seems to be probable, in which all similar substituents are placed on the same side of the molecule. The non-bonded interaction between H–1 and H–4′ is diminished by a slight twisting of the plane of the two rings about the glucosidic bond in opposite directions. This arrangement renders possible the forming of O–2… O–3′ hydrogen bonds which contributes to the stabilization of the helical structure. Therefore under such conditions when this H bond is stable, the homologues of maltose – amylose too – achieve a helical molecular configuration.     

自由基氧化对猪肌球蛋白-醛类化合物吸附特性的影响

采用FeCl3/抗坏血酸/H2O2羟自由基氧化体系模拟猪肌球蛋白氧化,研究不同H2O2浓度对肌球蛋白巯基总量、活性巯基、二级结构和表面疏水性的影响及与4?种典型醛类风味物质间的相互作用。结果表明：H2O2浓度对蛋白质构象有显著影响,随着H2O2浓度逐渐增加,活性巯基含量显著下降（P＜0.05）,表面疏水性显著增加（P＜0.05）。当H2O2浓度在0～5?mmol/L之间时,巯基总量、α-螺旋相对含量显著下降（P＜0.05）,蛋白质吸附能力显著增强（P＜0.05）;当H2O2浓度在5～10?mmol/L之间时,α-螺旋相对含量显著上升（P＜0.05）,蛋白质吸附能力显著减弱（P＜0.05）;当H2O2浓度在10～20?mmol/L之间时,蛋白质吸附能力显著增强（P＜0.05）。肌球蛋白与醛类化合物间的作用力主要为氢键和疏水相互作用,氢键和（或）疏水相互作用越强,蛋白质对醛类化合物吸附能力越强。     

Production of cis-1,2-dihydroxy-3-methylcyclohexa-3,5-diene (toluene cis glycol) by Rhodococcus sp. MA 7249

An attractive method for producing cis-1,2-dihydroxy-3-methylcyclohexa-3,5-diene (toluene cis glycol) was developed employing a cis dihydrodiol dehydrogenase "deficient" strain of Rhodococcus (MA 7249). The toluene cis glycol produced was found to have optical rotations of [alpha]D25 = +25.8 (c 0.45, CH3OH) and +72.8 (c 0.42, CHCl3) which indicated an absolute configuration of (1S,2R) when compared with previously published values. When cultivated in laboratory fermentor in the presence of toluene vapors, MA 7249 reached a toluene cis glycol concentration up to 18 g/l in 110 h. Culture MA 7249 also accumulated cis (1S,2R) dihydrodiols from dihydronaphthalene, biphenyl, chlorobenzene, and styrene.     

重组漆酶降解黄曲霉毒素B1分子对接分析及产物结构解析

以重组漆酶lac3基因同源性最高的3KW7作为模板进行同源模建,采用分子对接预测漆酶与黄曲霉毒素B1（aflatoxin B1,AFB1）的结合模式,结果显示漆酶与AFB1可以相互作用,氢键是其关键作用力,漆酶可用于黄曲霉毒素的降解。随后,通过实际的降解实验进行验证,响应面优化获得AFB1降解率最优的条件为底物AFB1 1 μg、孵育时间15 h、孵育温度34 ℃、酶活力2 U,降解率可达91.08%。在此条件下利用超高效液相色谱-飞行时间串联质谱分析AFB1降解产物结构,发现4 个主要降解产物,根据其二级质谱信息和精确分子质量,推测出降解产物的分子式分别为C16H22O4、C14H16N2O2、C7H12N6O和C24H30O6。     

Elimination of Listeria monocytogenes biofilms by ozone, chlorine, and hydrogen peroxide

This study evaluated the efficacy of ozone, chlorine, and hydrogen peroxide to destroy Listeria monocytogenes planktonic cells and biofilms of two test strains, Scott A and 10403S. L. monocytogenes was sensitive to ozone (O3), chlorine, and hydrogen peroxide (H2O2). Planktonic cells of strain Scott A were completely destroyed by exposure to 0.25 ppm O3 (8.29-log reduction, CFU per milliliter). Ozone's destruction of Scott A increased when the concentration was increased, with complete elimination at 4.00 ppm O3 (8.07-log reduction, CFU per chip). A 16-fold increase in sanitizer concentration was required to destroy biofilm cells of L. monocytogenes versus planktonic cells of strain Scott A. Strain 10403S required an ozone concentration of 1.00 ppm to eliminate planktonic cells (8.16-log reduction, CFU per milliliter). Attached cells of the same strain were eliminated at a concentration of 4.00 ppm O3 (7.47-log reduction, CFU per chip). At 100 ppm chlorine at 20 degrees C, the number of planktonic cells of L. monocytogenes 10403S was reduced by 5.77 log CFU/ml after 5 min of exposure and by 6.49 log CFU/ml after 10 min of exposure. Biofilm cells were reduced by 5.79 log CFU per chip following exposure to 100 ppm chlorine at 20 degrees C for 5 min, with complete elimination (6.27 log CFU per chip) after exposure to 150 ppm at 20 degrees C for 1 min. A 3% H2O2 solution reduced the initial concentration of L. monocytogenes Scott A planktonic cells by 6.0 log CFU/ml after 10 min of exposure at 20 degrees C, and a 3.5% H2O2 solution reduced the planktonic population by 5.4 and 8.7 log CFU/ml (complete elimination) after 5 and 10 min of exposure at 20 degrees C, respectively. Exposure of cells grown as biofilms to 5% H2O2 resulted in a 4.14-log CFU per chip reduction after 10 min of exposure at 20 degrees C and in a 5.58-log CFU per chip reduction (complete elimination) after 15 min of exposure.     

Photocatalytic oxidation of gaseous 2-chloroethyl ethyl sulfide over TiO2

Photocatalytic oxidation of gaseous 2-chloroethyl ethyl sulfide (2-CEES, ClCH2CH2SCH2CH3) over TiO2 illuminated with UV light and maintained at 25 or 80 degrees C in air has been investigated. 2-CEES was found to suffer progressive oxidation to yield ethylene (CH2CH2), chloroethylene (ClCHCH2), ethanol (CH3CH2OH), acetaldehyde (CH3C(O)H), chloroacetaldehyde (ClCH2C(O)H), diethyl disulfide (CH3CH2S2CH2CH3), 2-chloroethyl ethyl disulfide (ClCH2CH2S2CH2CH3), and bis(2-chloroethyl) disulfide (ClCH2CH2S2CH2CH2Cl) as the main primary intermediates, and water (H2O), carbon dioxide (CO2), sulfur dioxide (SO2), surface sulfate ions (SO4(2-)), and hydrogen chloride (HCl) as the final products. Trace concentrations of gaseous 2-chloroethanol (ClCH2CH2OH), ethanesulfonyl chloride (CH3CH2SO2Cl), ethyl thioacetate (CH3CH2SC(O)CH3), and considerable amounts of acetic acid (CH3C(O)OH), crotonaldehyde (CH3CHCHC(O)H), methyl acetate (CH3C(O)OCH3), and methyl formate (CH3OC(O)H) were also detected in the gas phase during the photooxidation conducted at 80 degrees C. Increase in temperature from 25 to 80 degrees C accelerates formation of gaseous ethanol, acetaldehyde, chloroacetaldehyde, diethyl disulfide, 2-chloroethyl ethyl disulfide, and bis(2-chloroethyl) disulfide but suppresses ethylene and chloroethylene production at initial stages of the process. Some aspects of the possible reaction mechanism leading to this wide array of intermediates and final products are discussed.     

低温加热状态下烤烟气溶胶释放量及其影响因素

为考察烟草在低温加热状态下气溶胶释放特性,采用自制稳态热解装置和烟密度计联用测试系统(SSTF-SDG)建立了可定量表征气溶胶释放量的烟草质量光密度(D_m)测试方法,考察了全国不同产区、品种、部位共34种烤烟样品在低温加热状态下的D_m,并对D_m与烤烟主要元素及常规化学成分的关系进行了统计分析。结果表明:①基于SSTF-SDG,该方法可分析低温加热状态下烟草D_m。②D_m与烟草中碳、氢、氮、烟碱均在0.01水平显著正相关,与钾硫比、钾氮比、(碳+氢)/氧以及糖碱比均在0.01水平显著负相关。③D_m各影响因素重要性排序依次为:碳 > 烟碱 > 钾硫比 > 氮 > 钾氮比 > 氢 > (碳+氢)/氧 > 糖碱比 > 硫 > 钾 > 总糖 > 氧 > 还原糖 > 氯 > 钾氯比。④由碳、氮和钾硫比为自变量的回归方程可较好地评价烤烟烟叶低温加热状态下气溶胶释放量。      

The Effects of Plasticizers Containing Amide Groups on the Properties of Thermoplastic Starch

Several amide groups‐containing plasticizers for thermoplastic starch (TPS), such as formamide, acetamide, and urea, were studied in this paper with glycerol as reference. The hydrogen bond interaction between starch and plasticizers in TPS was tested by Fourier transform infrared (FT‐IR) spectroscopy. Both the oxygen of the C‐O‐H group and the oxygen of the C‐O‐C group in starch could form hydrogen bonds with these plasticizers. The order of the hydrogen bond‐forming abilities is as follows: urea > formamide > acetamide > polyols. The retrogradation of formamide‐plasticized TPS (FPTPS), acetamide‐plasticized TPS (APTPS) and urea‐plasticized TPS (UPTPS) was investigated at three levels of relative humidity (RH=0, 50 and 100%) using X‐ray diffractometry. Urea and formamide could effectively improve the resistance of TPS towards retrogradation. The studied mechanical properties demonstrated that FPTPS had a good breaking strain but poor breaking stress, while UPTPS had opposite characteristics. The properties of TPS mainly relied on the hydrogen bond‐forming abilities between plasticizers and the starch matrix. On the other hand, the water resistance of TPS mainly depended on the plasticizer. The higher the water absorption of the plasticizer was, the better was the water resistance of the TPS.     

Changes in properties of white shrimp (<Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>) protein during thermal denaturation

Changes in white shrimp (Litopenaeus vannamei) protein during thermal denaturation were studied using Raman spectroscopy and isotopic H/D exchange. Denaturation of shrimp protein began after heating for 10 min at 50°C. A decrease in the percentage of α-helices accompanied by an increase in the percentage of β-sheets occurred while the total percentage of disordered structures increased. With extension of the exchange time, the relative intensity of the O-D bond increased, accompanied by a higher relative O-D bond intensity for heated shrimp, compared with unheated shrimp. H/D exchange revealed a higher rate of deuteration kinetics in heated shrimp than for unheated shrimp, especially during the first 2 h, consistent with water loss from denatured white shrimp protein. Physical property changes in muscle tissue can be caused by changes in hydrogen bonding and hydrophobicity during thermal processes.     

大肠杆菌抗氧化基因突变对内源过氧化氢的影响

为了阐明大肠杆菌(E.coli)抗氧化基因(ahp C/F、kat E/G、oxyR ahp C/F、sod A/B)对细菌内源过氧化氢(H2O2)调控中的协同作用,本研究以E.coli抗氧化基因突变株及其野生型菌株为研究对象,通过紫外分光光度法分析过氧化氢酶活性变化,荧光法检测内源H2O2浓度变化,组织化学法对细胞内H2O2进行定量和定位分析,光密度法分析菌株生长规律。结果表明,与野生型菌株相比,突变体JI367、JI370和AS240生长过程中过氧化氢酶活性总体升高,整个生长周期内H2O2浓度降低,而LC74过氧化氢酶活性降低,整个生长周期中内源H2O2浓度升高;组织化学染色法表明各菌株内源H2O2有显著差异(p<0.05),LC74内源H2O2累积量最多;JI367、JI370和AS240生长迟缓,LC74对数期后期生长速度较野生型快。结果说明,当H2O2浓度累积到高于大约5.4μmol/L时促进E.coli生长,不同的抗氧化基因之间受调控子蛋白OxyR调控存在补偿性表达作用,抗氧化酶Ahp C/F在降解内源H2O2方面起主要作用。本实验为细菌内源H2O2的调控机制的系统研究提供了新的证据。      

Density functional theory studies on the structures and water-exchange reactions of aqueous Al(III)-oxalate complexes

The structures and water-exchange reactions of aqueous aluminum-oxalate complexes are investigated using density functional theory. The present work includes (1) The structures of Al(C(2)O(4))(H(2)O)(4)(+) and Al(C(2)O(4))(2)(H(2)O)(2)(-) were optimized at the level of B3LYP/6-311+G(d,p). The geometries obtained suggest that the Al-OH(2) bond lengths trans to C(2)O(4)(2-) ligand in Al(C(2)O(4))(H(2)O)(4)(+) are much longer than the Al-OH(2) bond lengths cis to C(2)O(4)(2-). For Al(C(2)O(4))(2)(H(2)O)(2)(-), the close energies between cis and trans isomers imply the coexistence in aqueous solution. The (27)Al NMR and (13)C NMR chemical shifts computed with the consideration of sufficient solvent effect using HF GIAO method and 6-311+G(d,p) basis set are in agreement with the experimental values available, indicating the appropriateness of the applied models; (2) The water-exchange reactions of Al(III)-oxalate complexes were simulated at the same computational level. The results show that water exchange proceeds via dissociative pathway and the activation energy barriers are sensitive to the solvent effect. The energy barriers obtained indicate that the coordinated H(2)O cis to C(2)O(4)(2-) in Al(C(2)O(4))(H(2)O)(4)(+) is more labile than trans H(2)O. The water-exchange rate constants (k(ex)) of trans- and cis-Al(C(2)O(4))(2)(H(2)O)(2)(-) were estimated by four methods and their respective characteristics were explored; (3) The significance of the study on the aqueous aluminum-oxalate complexes to environmental chemistry is discussed. The influences of ubiquitous organic ligands in environment on aluminum chemistry behavior can be elucidated by extending this study to a series of Al(III)-organic system.     

Production of hydrogen sulfide from tetrathionate by the iron-oxidizing bacterium Thiobacillus ferrooxidans NASF-1

When incubated under anaerobic conditions, five strains of Thiobacillus ferrooxidans tested produced hydrogen sulfide (H2S) from elemental sulfur at pH 1.5. However, among the strains, T. ferrooxidans NASF-1 and AP19-3 were able to use both elemental sulfur and tetrathionate as electron acceptors for H2S production at pH 1.5. The mechanism of H2S production from tetrathionate was studied with intact cells of strain NASF-1. Strain NASF-1 was unable to use dithionate, trithionate, or pentathionate as an electron acceptor. After 12 h of incubation under anaerobic conditions at 30 degrees C, 1.3 micromol of tetrathionate in the reaction mixture was decomposed, and 0.78 micromol of H2S and 0.6 micromol of trithionate were produced. Thiosulfate and sulfite were not detected in the reaction mixture. From these results, we propose that H2S is produced at pH 1.5 from tetrathionate by T. ferrooxidans NASF-1, via the following two-step reaction, in which AH2 represents an unknown electron donor in NASF-1 cells. Namely, tetrathionate is decomposed by tetrathionate-decomposing enzyme to give trithionate and elemental sulfur (S4O6(2-)-->S3O6(2-) + S(o), Eq. 1), and the elemental sulfur thus produced is reduced by sulfur reductase using electrons from AH2 to give H2S (S(o) + AH2-->H2S + A, Eq. 2). The optimum pH and temperature for H2S production from tetrathionate under argon gas were 1.5 and 30 degrees C, respectively. Under argon gas, the H2S production from tetrathionate stopped after 1 d of incubation, producing a total of 2.5 micromol of H2S/5 mg protein. In contrast, under H2 conditions, H2S production continued for 6 d, producing a total of 10.0 micromol of H2S/5 mg protein. These results suggest that electrons from H2 were used to reduce elemental sulfur produced as an intermediate to give H2S. Potassium cyanide at 0.5 mM slightly inhibited H2S production from tetrathionate, but increased that from elemental sulfur 3-fold. 2,4-Dinitrophenol at 0.05 mM, carbonylcyanide-m-chlorophenyl- hydrazone at 0.01 mM, mercury chloride at 0.05 mM, and sodium selenate at 1.0 mM almost completely inhibited H2S production from tetrathionate, but not from elemental sulfur.     

活性炭负载磷钨酸催化合成香料苹果酯-B

制备了环境友好催化剂活性炭负载磷钨酸H3PW12O40/C，并以H3PW12O40/C为催化剂催化合成了香料苹果酯-B。得到了苹果酯-B合成的适宜工艺条件：n（1，2-丙二醇）：n（乙酰乙酸乙酯）=1．5：1，H3PW12O40/C负载量为23．1％，H3PW12O40/C用量为反应物总质量的1．0％，反应时间为120min，苹果酯-B的收率为84．8％，目的产物经红外光谱、质谱和元素分析确证。     

Al_2O_3无机膜的制备及表面自由能计算

以异丙醇铝(AIP)为前驱体,采用溶胶-凝胶法制备Al_2O_3无机膜,并对不同温度焙烧的Al_2O_3无机膜进行接触角测试及表面自由能计算.结果表明,蒸馏水在膜材料表面接触角均小于90°,膜材料表现为亲水特性;随着焙烧温度的升高,Al_2O_3无机膜的表面自由能先减小后增大,当焙烧温度为350℃时,表面润湿性最弱,表面自由能达到最小值54.95×10~(-5)N·cm~(-1),其色散、偶极矩以及氢键分量分别为26.53×10~(-5),14.62×10~(-5)和13.80×10~(-5)N·cm~(-1).     

双氧水氧化脱毛机理及工艺条件优化

观察了双氧水对毛的作用，并测定了脱毛过程中双氧水对生皮及皮胶原的影响。数据显示，毛的破坏是双氧水和NaDH共同作用的结果。脱毛时，毛根首先被溶解，因而有利于保毛脱毛法的实施。在碱性环境中，双氧水不会对生皮产生破坏作用，反而显示出对皮胶原纤维有一定的保护作用，这种保护作用可能是由于双氧水引发了胶原纤维间的交联反应，它导致成革抗张强度提高、伸长率降低。与传统Na2S脱毛相比，双氧水脱毛后，裸皮的等电点更高，可能是由于双氧水的氧化作用导致皮胶原衍生出了更多的阴离子基团，如羧基。这一变化使双氧水脱毛后铬鞣革的铬含量增加。基于这些研究结果，提出了双氧水毁毛脱毛法和双氧水保毛脱毛法的优化工艺条件。     

The effect of pH on thiosulfate formation in a biotechnological process for the removal of hydrogen sulfide from gas streams

In a biotechnological process for hydrogen sulfide (H2S) removal from gas streams, operating at natronophilic conditions, formation of thiosulfate (S2O3(2-)) is unfavorable, as it leads to a reduced sulfur production. Thiosulfate formation was studied in gas-lift bioreactors, using natronophilic biomass at [Na+] + [K+] = 2 mol L(-1). The results show that at sulfur producing conditions, selectivity for S2O3(2-) formation mainly depends on the equilibrium between free sulfide (HS(-)) and polysulfide (Sx(2-)), which can be controlled via the pH. At pH 8.6, 21% of the total dissolved sulfide is present as Sx(2-) and selectivity for S2O3(2-) formation is 3.9-5.5%. At pH 10, 87% of the total dissolved sulfide is present as Sx(2-) and 20-22% of the supplied H2S is converted to S2O3(2-), independent of the H2S loading rate. Based on results of bioreactor experiments and biomass activity tests, a mechanistic model is proposed to describe the relation between S2O3(2-) formation and pH.     

Inactivation of Escherichia coli O157:H7, Salmonella enterica serotype enteritidis,and Listeria monocytogenes on lettuce by hydrogen peroxide and lactic acid and by hydrogen peroxide with mild heat

Iceberg lettuce is a major component in vegetable salad and has been associated with many outbreaks of foodborne illnesses. In this study, several combinations of lactic acid and hydrogen peroxide were tested to obtain effective antibacterial activity without adverse effects on sensory characteristics. A five-strain mixture of Escherichia coli O157:H7, Salmonella enterica serotype Enteritidis, and Listeria monocytogenes was inoculated separately onto fresh-cut lettuce leaves, which were later treated with 1.5% lactic acid plus 1.5% hydrogen peroxide (H2O2) at 40 degrees C for 15 min, 1.5% lactic acid plus 2% H2O2 at 22 degrees C for 5 min, and 2% H2O2 at 50 degrees C for 60 or 90 s. Control lettuce leaves were treated with deionized water under the same conditions. A 4-log reduction was obtained for lettuce treated with the combinations of lactic acid and H2O2 for E. coli O157:H7 and Salmonella Enteritidis, and a 3-log reduction was obtained for L. monocytogenes. However, the sensory characteristics of lettuce were compromised by these treatments. The treatment of lettuce leaves with 2% H2O2 at 50 degrees C was effective not only in reducing pathogenic bacteria but also in maintaining good sensory quality for up to 15 days. A < or = 4-log reduction of E. coli O157:H7 and Salmonella Enteritidis was achieved with the 2% H2O2 treatment, whereas a 3-log reduction of L. monocytogenes was obtained. There was no significant difference (P > 0.05) between pathogen population reductions obtained with 2% H2O2 with 60- and 90-s exposure times. Hydrogen peroxide residue was undetectable (the minimum level of sensitivity was 2 ppm) on lettuce surfaces after the treated lettuce was rinsed with cold water and centrifuged with a salad spinner. Hence, the treatment of lettuce with 2% H2O2 at 50 degrees C for 60 s is effective in initially reducing substantial populations of foodborne pathogens and maintaining high product quality.