Voltammetric Method for Manganese Analysis in Indian Traditional Leafy Vegetables and Medicinal Plants Collected Around Tirupati Town, a Famous Pilgrim Center in India: The Catalytic Hydrogen Wave (CHW) Technique

Cost-effective, rapid, sensitive, and novel catalytic hydrogen wave technique (CHW) was developed for the analysis of manganese(II) in NH₄Cl–NH₄OH medium at pH 6.2 and produced catalytic hydrogen waves at −0.60 and −0.56 V Vs SCE with ammonium piperidine dithiocarbamate and ammonium morpholine dithiocarbamate, respectively, in various leafy vegetables and medicinal plants collected around Tirupati, Chittoor District, Andhra Pradesh which is one the famous pilgrim centers in India. Different optimal parameters like effect of pH, supporting electrolyte (NH₄Cl–NH₄OH) concentration, ligand and metal ion concentrations, and effect of adverse ions on peak height were studied to improve the sensitivity, selectivity, and detection limits CHW technique. This technique was compared in terms of Student t test and variance ratio f test with differential pulse polarography (DPP) method. The technique was applied for the analysis of manganese(II) in leafy vegetables and medicinal plants. The results obtained are in good agreement with DPP.     

A new amperometric biosensor for hydrogen peroxide determination based on HRP-nanogold-PTH-nanogold-modified carbon paste electrodes

A new strategy for immobilization of horseradish peroxidase (HRP) has been developed by self-assembling gold nanoparticles to multiporous polythionine (PTH) film modified carbon paste interface. A thionine film was initially electropolymerized onto carbon paste interface in a mildly acidic thionine solution at a bias voltage of −1.0 to 1.5 V. This process is accompanied by the hydrogen evolution reaction, and the released hydrogen gas made the PTH film with multiporous structure. The multiporous PTH film provided a biocompatible microenvironment for gold nanoparticles and enzyme molecules, and greatly amplified the coverage of HRP molecules on the electrode surface. Voltammetric and time-based amperometric techniques were employed to characterize the properties of the derived biosensor. The performance and factors influencing the performance of the biosensor were also proposed. The immobilized HRP displayed a catalytic property to the reduction of H₂O₂. The H₂O₂ biosensor achieved 95% of the steady-state current within 2 s, and exhibited a linear range of 9.6×10⁻⁶ to 1.2×10⁻³ M H₂O₂ with a detection limit of 7.5×10⁻⁷ M (S/N = 3). Furthermore, the biosensor remained at about 90% of its original sensitivity after 2 weeks’ storage.     

A Sensitive, Selective New Analytical Reagent, 2, 6-Diacetylpyridine bis-4-phenyl-3-thiosemicarbazone for Extractive Spectrophotometric Determination of Mo(VI) in Food Samples

Synthesized a new reagent 2, 6-Diacetylpyridine bis-4-phenyl-3-thiosemicarbazone (2, 6-DAPBPTSC) characterized and is proposed as a sensitive and selective analytical reagent for the extractive spectrophotometric determination of molybdenum(VI) at pH 3.5 to form a yellowish orange colored 1:1 chelate complex. The absorbance was measured at a maximum wavelength, 500 nm. This method obeys Beer’s law in the concentration range 0.90–9.00 μg mL⁻¹ and the correlation coefficient of Mo(VI)–2,6-DAPBPTSC complex is 0.954, which indicates an adequate linearity between the two variables with good molar absorptivity and Sandell’s sensitivity, 1.212 × 10⁴ L mol⁻¹cm⁻¹, 0.0079 μg cm⁻², respectively. The precision and accuracy of the method is checked with calculation of relative standard deviation (n = 5), 0.894% and the detection limit value is 0.0056 μg mL⁻¹. The instability constant of the method has been calculated by Asmus’ method as 6.476 × 10^–5, at room temperature. The interfering effect of various cations and anions has also been studied. The method was successfully applied for the determination of Mo(VI) in food and water samples. The validity of the present method was evaluated in terms of Student ‘t’ test and Variance ‘f’ test, which indicates the significance of the present method an inter comparison of the experimental values, using atomic absorption spectrometer.     

Fluorphosphate—eine neue Wirkstoffgruppe für Holzschutzmittel

The effectiveness of monofluoromonophosphates of sodium, potassium, ammonium, copper and zinc against wood destroying fungi and insects is described. In the field of non-fixing wood preservatives the alcali monofluoromonophosphates. M₂PO₃F, (M=Na, K, NH₄) may be a suitable alternative of trademark active substances. The fluorophosphates Cu₂K(OH((PO₃F)₂·H₂O and ZnPO₃F·2,5 H₂O are fixed in the timber without any admixture of chromium. The use of these compounds in form of a new mixture of salts of the type KFPZ is recommended. To get wider the field of biological activity further studies will be carried out.     

ABILITY OF VARIOUS CHEMICALS TO REDUCE COPPER AND TO INACTIVATE MUSHROOM TYROSINASE1

Treatment of mushroom tyrosinase with reducing agents such as hydrogen peroxide, ascorbic acid, phenylhydrazine, gallic acid, ferrocyanide and NH₂OH resulted in inactivation of the enzyme. Under the conditions tested, 50% inactivation of the enzyme was obtained with 4 μM H₂O₂, 20 μM ascorbic acid, 40μM phenylhydrazine, 6 mM gallic acid, 12 mM ferrocyanide and 22 mM NH₂OH. The ability of the reducing agents to reduce Cu²⁺ in a chemical model system was determined and it was found that gallic acid, phenylhydrazine, ascorbic acid and NH₂OH are relatively good reductants of Cu²⁺ while H₂O₂ and ferrocyanide are relatively poor ones. The copper content of mushroom tyrosinase before and after inactivation by each of the reducing agents was determined. The copper content of the enzyme inactivated by H₂O₂, NH₂OH, phenylhydrazine, ferrocyanide, gallic acid and ascorbic acid was 100%, 90%, 90%, 85%, 85% and 76% compared to that of the control (enzyme not treated). It was concluded that the degree of inactivation of mushroom tyrosinase by the reducing agents was not correlated with the decrease in the copper content of the enzyme nor with their ability to reduce Cu²⁺ in a chemical model system.     

Decomposition of sinigrin by methanol/ammonia/water treatment in model systems and mustard (Brassica nigra L.) seed meal

 Sinigrin (allylglucosinolate) was stored at 20  °C, 40  °C, and 60  °C in solutions containing 10% ammonia in 95% methanol (CH₃OH/NH₃/H₂O). The individual samples were analyzed for their contents of sinigrin, its decomposition product allyl isothiocyanate (AITC) and other reaction products. The major reaction products were allyl thiourea, methyl ester of N-allyl thiocarbamoyl acid and allyl cyanide. A newly identified decomposition product of sinigrin was ethylcyanide. Defatted Brassica nigra seed meal was treated by the CH₃OH/NH₃/H₂O mixture to simulate the procedure used for rape and mustard seed meal detoxification. suspensions of the meal in the above mixture of solvents were heated at 20  °C, 40  °C and 60  °C, respectively. The major reaction products were the same as those arising from sinigrin. Minor products identified were 4-hydroxybenzyl isothiocyanate formed from sinalbin and 2-hydroxy-butenyl cyanide which arises from progoitrin. In all cases, AITC was very rapidly decomposed. Mechanisms explaining sinigrin decomposition are presented and discussed. Received: 3 May 1999     

Effects of starch acryloylation on the grafting efficiency,adhesion, and film properties of acryloylated starch‐g‐poly(acrylic acid) for warp sizing

In order to enhance the grafting efficiency of graft copolymerization of granular cornstarch with acrylic acid (AA) for improving the adhesion and film properties of starch‐g‐poly(acrylic acid) used as sizing agent, the esterification of hydrolyzed starch with acryloyl chloride was applied before graft copolymerization. The influence of three common initiators on the copolymerization were also studied. The initiators included ceric ammonium nitrate [Ce(NH₄)₂(NO₃)₆], hydrogen peroxide/ferrous ammonium sulfate [H₂O₂/FeSO₄ · (NH₄)₂SO₄], and potassium persulfate/sodium bisulfite [K₂S₂O₈/NaHSO₃]. It was found that acryloylation of starch before the copolymerization was an effective method for substantially enhancing the grafting efficiency and improving the performances such as adhesion‐to‐fibers and mechanical properties of grafted starch film. The acryloylation could increase the efficiency to 67–81% when the degree of substitution (DS) of acryloylated starch ranged from 0.010 to 0.036. The adhesion to polyester and cotton fibers reached their maximum at DS = 0.010 and 0.022, respectively. Strong and tough film was obtained when the DS value was in a range of 0.010–0.022. H₂O₂/FeSO₄ · (NH₄)₂SO₄ redox system was more appropriate for initiating the copolymerization of acryloylated starch with AA.     

Influence of nitrogen form on yield and nitrate content of subirrigated early potato

Potato is classified among the vegetables with low nitrate content but, in diet, it contributes most to the daily intake of nitrate, because of its high per capita consumption. Two trials were carried out in winter–spring and autumn–winter cycles using a trough bench subirrigation system. Potato seedlings were transplanted into pots containing peat, pumice and vermiculite in a 3:1:1 volume ratio. Both trials were carried out to compare three nutrient solutions having the same nitrogen concentration (6.4 mM ), but different ammonium:nitrate (NH₄‐N:NO₃‐N) percentage ratios (100:0, 50:50 and 0:100). In the winter–spring cycle, tubers were lower in weight and were more numerous than in the autumn–winter cycle. The tuber yield of ammonium‐fed plants was lower than with the mixed form and 100% NO₃‐N, but only in the trial carried out in the winter–spring period. Nitrate‐fed plants yielded a number of tubers almost 3‐fold higher than ammonium‐fed plants. The NO₃ content of tubers harvested in spring in the presence of 100% NH₄‐N in the nutrient solution was a 25% of that in nitrate‐fed plants (44 vs 169 mg kg^?1 of fresh mass); in tubers harvested in winter, with worse light conditions, nitrate content increased with increasing NO₃‐N in the nutrient solution (26, 109, and 225 mg kg^?1 of fresh mass with NH₄‐N:NO₃‐N 100:0, 50:50 and 0:100, respectively). The substrate electrical conductivity increased with increasing ammonium concentration in the nutrient solution, and was higher in the upper layer of the substrate. Copyright © 2004 Society of Chemical Industry     

Determination of nonylphenol ethoxylate metabolites in vegetables and crops by high performance liquid chromatography-tandem mass spectrometry

A method has been developed for the simultaneous determination of the concentration of nonylphenol (4-NP), nonylphenol monoethoxylates (NP₁EO) and nonylphenol diethoxylates (NP₂EO) in vegetables and crops by liquid chromatography-tandem quadrupole mass spectrometry (HPLC-MS/MS). These target compounds were extracted from vegetable and crop samples with acetonitrile, and then the extracts were cleaned using solid phase extraction with graphitised carbon black tandem primary secondary amine (PSA) cartridges. The MS method enabled highly reliable identification by monitoring the corresponding ammonium adduct [M+NH₄]⁺ in the positive mode for NP₁EO and NP₂EO, and the deprotonated molecule [M−H]⁻ in the negative mode for 4-NP. Recoveries for the spiked samples ranged from 65% to 118%. The limit of detection (LOD) of 4-NP, NP₁EO and NP₂EO was 3, 5 and 0.1 μg kg⁻¹, respectively. This method would be useful for the quick and routine detection of the residues of 4-NP, NP₁EO and NP₂EO in vegetables and crops.     

Antioxidant peptides isolated from sea cucumber Stichopus Japonicus

The sea cucumber Stichopus japonicus protein was hydrolyzed by pepsin, trypsin, papain, acid protease and neutral protease, respectively, to get five kinds of peptide fractions: pepsin peptides (PP), trypsin peptides (TP), acid protease peptides (AP), neutral protease peptides (NP) and papain peptide (PAP). Antioxidative activities of all peptide fractions were evaluated by hydroxyl radical– (·OH) and Superoxide anion (O₂ ^{· −} )–scavenging activity. Trypsin peptide (TP) exhibited the highest antioxidative activity compared to other peptide fractions. In considering scavenging effects on hydroxyl radicals (·OH) and Superoxide anions (O₂ ^{· −} ), TP was employed for isolation, purification and identification of antioxidant peptide. To purify and characterize antioxidative peptide, two steps gel filtration, one-step ion-exchange column chromatography and reversed-phase high-performance liquid chromatography (RP-HPLC) were used. The purified antioxidative peptide TP2b-1 was a novel peptide and was sequenced as GPEPTGPTGAPQWLR, in which the low molecular weight and some amino acid constituents played important role in the radical-scavenging effects according reports. The IC₅₀ values of TP2b-1 were 138.9 μM on ·OH and 353.9 μM on O₂ ^{· −} .     

Maintaining quality of wild vegetables (Aster glehni and Aruncus dioicus var. kamtschaticus) from Ulleungdo(Island), Korea by modified atmosphere packaging

Wild vegetables, Aster glehni and Aruncus dioicus var. kamtschaticus, produced from Ulleungdo (Island), Korea were packaged with 30 μm polypropylene (PP), 30 μm antifogging oriented polypropylene (A-OPP), 30 μm microperforated antifogging oriented polypropylene (MiA-OPP), 30 μm macroperforated low density polyethylene (Ma-LDPE), and 20 μm macroperforated high density polyethylene (Ma-HDPE), stored at 4, 10, and 20°C. Concentrations of O₂ and CO₂ in the packages were not modified by Ma-LDPE and Ma-HDPE. Weight loss was retarded by PP, A-OPP, MiA-OPP, especially as storage temperature decreased. Soluble solids were not affected by packaging materials. pH slightly decreased in LDPE and Ma-HDPE. Appearance, color, and overall acceptability of both vegetables stored at 4°C in PP or MiA-OPP showed the highest sensory score. These results suggest that packaging with PP or MiA-OPP films and storage at 4°C could be a useful method to maintain quality of the wild vegetables.     

Evaluation of A Modified Gradient Feed Culturing System for Growth of Lactobacillus plantarum Sausage Starter Organism

An internally controlled gradient feed culturing technique, where a nutrient gradient was initiated and subsequently controlled by the lactic acid synthesis, was compared to conventional batch culturing for growth of a sausage starter organism, Lactobacillus plantarum. Significantly higher cell densities (p < 0.01) were observed with twice the culturing time for gradient feed culturing compared to batch culturing. Cell yields within batch or gradient feed culturing system were not affected by pH control at 5.8 or 6.0. Significantly higher (p < 0.05) cell yields, however, were obtained for gradient feed cultures (pH 6.0) with NH₄OH addition at 50% theoretical lactic acid (TLA) level than were obtained at 10% TLA or without NH₄OH addition.     

Sensitive Determination of Decoquinate in Milk by High-Performance Liquid Chromatographic Coupled to Laser-Induced Fluorescence Detection

A new and sensitive method based on high performance liquid chromatography with laser-induced fluorescence detection has been developed for the determination of decoquinate in milk. Laser source was obtained with a He–Cd laser using a continuous excitation wavelength at 325 nm. Decoquinate exhibits moderate fluorescence, but it is increased using Ca(NO₃)₂ in the mobile phase. The chromatographic separation was performed on a Luna C₁₈ 5-mm reversed phase column, which solves the broadening of peaks and peak tailing compared with other columns tested. The mobile phase, delivered at 1 ml min⁻¹, consisted of methanol–calcium nitrate (0.025 M)–acetonitrile (83/13/4 v/v/v). Decoquinate was successfully cleaned up from milk by solid-phase extraction using C₁₈ cartridges. The method was found to be linear between 0.16 and 16.33 ng ml⁻¹. The results of recovery studies were found to be satisfactory; an average recovery rate of 88.7% was obtained. The LOQ of decoquinate in milk was 0.16 ng ml⁻¹. The intraday relative standard deviation (RSD) was 4%, and interday assay gave an RSD of 4.4%.     

A non-destructive ammonium detection method as indicator for freshness for packed fish: Application on cod

This paper introduces a non-destructive method for monitoring headspace ammonium as an indicator for changes in the freshness status of packed fish. Electrodes in an aqueous phase in the package monitor changes in the concentration of ammonia produced in/on the packed fish and released in the headspace. The outputs of an ammonium ion-selective electrode (NH₄⁺-ISE) were compared with the volatile amines content of the fish fillets. The method was tested in triplicate with fresh cod fillets stored between −0.5 and 1.9 °C. Changes in the ammonia content of the fish could be monitored in the aqueous phase with the NH₄⁺-ISE. The changes in the NH₄⁺-ISE signal correlated with the content of volatile amines (TVB-N) in the cod fillets. This non-destructive method might be the basis for the development of an intelligent packaging for monitoring freshness of packed fish.     

Optimization of Trace Metals Concentration on Citric Acid Production by Aspergillus niger NRRL 2001

Citric acid is nowadays produced by submerged fermentation of Aspergillus niger. The process yield depends on the composition of the medium, as well as on the microorganism strain. In this work, the effect of Fe⁺³, Zn⁺², and Mn⁺² on citric acid production by A. niger NRRL 2001 is presented. The culture medium composition was glucose (120 g/L) KH₂PO₄ (1.0 g/L); K₂HPO₄ (1.0 g/L), MgSO₄.7H₂O (0.5 g/L), (NH₄)₂SO₄ (3.0 g/L). The ions Fe⁺³, Zn⁺², and Mn⁺² had their concentrations changed according to an experimental design. The experiments were carried out in an orbital shaker at 200 rpm and 30°C. The strain produced an extracellular polysaccharide that was also quantified. The optimum experimental condition was found using 7.0 mg/L of Fe⁺³ and 6.5 mg/L of Zn⁺² in absence of Mn⁺². No oxalic acid formation was observed using this experimental condition. Metal contents were not significant for the production of the polysaccharide. The highest production rate (2.95 g L⁻¹ day⁻¹) was reached after 10 days of fermentation. After this period, the productivity decreased slightly. In 20 days, the citric acid production rate (2.44 g L⁻¹ day⁻¹) was 82% of the highest productivity. The conversion into citric acid increased continuously, yielding 45.8% in 20 days of fermentation.     

Integrated control of postharvest diseases of pear fruits using antagonistic yeasts in combination with ammonium molybdate

The effect of ammonium molybdate (NH₄Mo) as an additive to improve biocontrol efficacy of antagonistic yeasts Rhodotorula glutinis and Trichosporon sp. against blue mold and Alternaria rot of pear fruits caused by Penicillium expansum and Alternaria alternata, respectively, was evaluated. Biocontrol activity of R. glutinis was enhanced in combination with NH₄Mo, whereas the efficacy of Trichosporon sp. was not improved. Combining R. glutinis with 1 mmol l^?1 NH₄Mo provided a more effective control on P. expansum and A. alternata than applying the yeast or NH₄Mo alone. Addition of 1 mmol l^?1 NH₄Mo significantly affected the growth of R. glutinis and Trichosporon sp. in nutrient yeast dextrose broth medium, but did not affect the growth of R. glutinis and Trichosporon sp. in pear wounds. Thus, it appears that the use of NH₄Mo is a useful approach to improve the efficacy of R. glutinis for postharvest disease control. Copyright © 2005 Society of Chemical Industry     

Properties of <Emphasis Type="Italic">Aspergillus subolivaceus</Emphasis> free and immobilized dextranase

Aspergillus subolivaceus dextranase is immobilized on several carriers by entrapment and covalent binding with cross-linking. Dextranase immobilized on BSA with a cross-linking agent shows the highest activity and considerable immobilization yield (66.7%). The optimum pH of the immobilized enzyme is shifted to pH 6.0 as compared with the free enzyme (pH 5.5). The optimum temperature of the reaction is resulted at 60 °C for both free and immobilized enzyme. Thermal and pH stability are significantly improved by the immobilization process. The calculated K _m of the immobilized dextranase (14.24 mg mL⁻¹) is higher than that of the free dextranase (11.47 mg mL⁻¹), while V _max of the immobilized enzyme (2.80 U μg protein⁻¹) is lower than that of the free dextranase (11.75 U μg protein⁻¹). The immobilized enzyme was able to retain 76% of the initial catalytic activity after 5.0 cycles.     

Sensitive determination of nitrite in food samples using voltammetric techniques

A [5,10,15,20-tetrakis (4-methoxyphenyl) porphyrinato] manganese (III)chloride (TMOPPMn(III)Cl)-modified gold electrode sensor was developed for the determination of nitrite in food samples. The developed sensor showed an excellent catalytic activity and stability for nitrite oxidation. Under optimized conditions, nitrite concentration as low as 2.9 × 10⁻⁹ M can be determined in various food samples using the developed sensor. Effect of common interfering ions have been investigated in simulated mixtures containing high levels of interfering ions and the sensor was found to be tolerant against these ions. The determination of nitrite in food samples such as chicken ham, sausage and pickled vegetables with the proposed sensor was in good agreement with those obtained by standard spectrophotometric method.     

Characterization and inhibition of <Emphasis Type="Italic">Rosmarinus officinalis</Emphasis> L. polyphenoloxidase

Polyphenoloxidase (PPO) from Rosmarinus officinalis L. was fractionated by ammonium sulfate ((NH₄)₂SO₄) precipitation and dialysis, and then some of its kinetic properties such as optimum pH and temperature, substrate specificity, thermal inactivation, and inhibition were investigated using 4-methylcatechol, catechol, and pyrogallol as substrates. The protein content of Rosmarinus officinalis L. extracts was determined according to Bradford’s method. Kinetic parameters, K _m and V _max, were calculated from Lineweaver–Burk plots. According to V _max/K _m ratio, 4-methylcatechol was the most suitable substrate. The optimum temperature and pH values were 20, 30 and 30 °C, and 7, 8 and 8 for 4-methylcatechol, catechol, and pyrogallol substrates, respectively. The thermal inactivation of PPO was investigated at 35, 55, and 75 °C. The enzyme activity decreased with increasing temperature. The effect of different inhibitors on partly purified Rosmarinus officinalis L. PPO was spectrophotometrically investigated. For this purpose, ascorbic acid and l-cysteine were used to inhibit the activity of Rosmarinus officinalis L. PPO at different concentrations. From the experimental results, it was found that l-cysteine is a more effective inhibitor than ascorbic acid due to lower K _i values.     

Use of Metals and Anion Species with Chemometrics Tools for Classification of Unprocessed and Processed Coconut Waters

Coconut water is a natural isotonic, nutritive, and low-caloric drink. Preservation process is necessary to increase its shelf life outside the fruit and to improve commercialization. However, the influence of the conservation processes, antioxidant addition, maturation time, and soil where coconut is cultivated on the chemical composition of coconut water has had few arguments and studies. For these reasons, an evaluation of coconut waters (unprocessed and processed) was carried out using Ca, Cu, Fe, K, Mg, Mn, Na, Zn, chloride, sulfate, phosphate, malate, and ascorbate concentrations and chemometric tools. The quantitative determinations were performed by electrothermal atomic absorption spectrometry, inductively coupled plasma optical emission spectrometry, and capillary electrophoresis. The results showed that Ca, K, and Zn concentrations did not present significant alterations between the samples. The ranges of Cu, Fe, Mg, Mn, PO₄³⁻, and SO₄²⁻ concentrations were as follows: Cu (3.1–120 μg L⁻¹), Fe (60–330 μg L⁻¹), Mg (48–123 mg L⁻¹), Mn (0.4–4.0 mg L⁻¹), PO₄³⁻ (55–212 mg L⁻¹), and SO₄²⁻ (19–136 mg L⁻¹). The principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied to differentiate unprocessed and processed samples. Multivariated analysis (PCA and HCA) were compared through one-way analysis of variance with Tukey–Kramer multiple comparisons test, and p values less than 0.05 were considered to be significant.