Determination and Evaluation of the Mineral Composition of Chinese Cabbage (Beta vulgaris)

Inductively coupled plasma optical emission spectrometry was used to determine the elements present in Chinese cabbage (Beta vulgaris). The accuracy of the method was confirmed by analysis of a certified reference material of spinach leaves. The study involved 57 samples that were collected in 13 Brazilian cities. Average concentrations of elements found per gram of Chinese cabbage were as follows: 3.44 mg g⁻¹ sodium, 5.09 mg g⁻¹ potassium, 1.25 mg g⁻¹ phosphorous, 0.85 mg g⁻¹ calcium, 0.49 mg g⁻¹ magnesium, 2.79 μg g⁻¹ manganese, 9.50 μg g⁻¹ iron, 0.74 μg g⁻¹ copper, 14.28 μg g⁻¹ zinc, and 6.44 μg g⁻¹ strontium. Principal component analysis and hierarchical cluster analysis demonstrated that there is no systematic difference in the mineral composition between the cabbage samples that were analyzed.     

Total Mercury, Inorganic Mercury and Methyl Mercury Determination in Red Wine

This study deals with the development of a method for total Hg, inorganic Hg and methylmercury (MeHg) determination in red wine by using flow injection-cold vapour generation–inductively coupled plasma mass spectrometry (FI-CVG-ICP-MS) and gas chromatography-ICP-MS (GC-ICP-MS). For Hg speciation analysis, a derivatization step was carried out using a 1% (m/v) sodium tetraphenylborate (NaBPh₄) solution, followed by extraction of Hg species and their quantification by GC-ICP-MS. The main parameters evaluated were the make-up gas flow rate, volume of the NaBPh₄ solution, time for derivatization reaction/analyte extraction and solvent used for Hg species extraction. Accuracy was evaluated by analyte recovery, whereas recoveries ranged from 99% to 104% for Hg(II) and MeHg. The limits of detection (LODs) for Hg(II) and MeHg were 0.77 and 0.80 μg L⁻¹, respectively. Wine from Argentina, Brazil, Chile and Uruguay were analysed. The wine samples were also acid digested for total Hg determination by FI-CVG-ICP-MS. The LOD of the method used for total Hg determination was 0.01 μg L⁻¹. The concentrations of Hg species in red wine measured by GC-ICP-MS were lower than the respective LODs. Only total Hg was detected in the analysed samples, where the highest concentration of Hg found was 0.55 ± 0.02 μg L⁻¹.     

An approach to improve ACE-inhibitory activity of casein hydrolysates with plastein reaction catalyzed by Alcalase

The preparation method of casein hydrolysates with high ACE-inhibitory activity was studied by Alcalase-catalyzed hydrolysis coupled with plastein reaction. Casein hydrolysates with an IC₅₀ value of about 47 μg mL⁻¹ were first prepared by hydrolysis of casein with Alcalase and then modified with plastein reaction catalyzed by the same enzyme. The impacts of four reaction conditions on plastein reaction of casein hydrolysates were studied, and then optimal conditions were determined using response surface methodology with the decrease of free amino groups in the reaction mixture as response. When the concentration of casein hydrolysates was fixed at 35% by weight, the maximum decrease of free amino groups in the reaction mixture of 181.8 μmol g⁻¹ proteins was obtained. The optimum conditions for the above decrease were found to be an E/S ratio of 7.7 kU g⁻¹ proteins, reaction temperature of 42.7 °C and reaction time of 6 h. Analysis results showed that ACE-inhibitory activity of casein hydrolysates prepared could be improved significantly by plastein reaction. When casein hydrolysates were modified by plastein reaction, with a decrease of free amino groups in the mixture of about 154.7 μmol g⁻¹ proteins and 181.8 μmol g⁻¹ proteins, their IC₅₀ values could be decreased to 0.6 and 0.5 μg mL⁻¹.     

ITS-RFLP characterization of black <Emphasis Type="Italic">Aspergillus</Emphasis> isolates responsible for ochratoxin A contamination in cocoa beans

In the present study, ochratoxigenic mycobiota in cocoa beans was identified at species level by digestion of the ITS products using the endonucleases HhaI, NlaIII and RsaI. Of the 132 isolates of Aspergillus section Nigri collected from cocoa beans, 89 were identified as A. tubingensis, 27 as A. niger, 10 as A. tubingensis-like and 6 as A. carbonarius. No variation was observed between RFLP patterns (C, N, T1 and T2) described previously for grape isolates and those of the cocoa isolates analysed. With respect to OTA-producing fungi, a high percentage of black aspergilli (50.7%) was able to produce OTA. Additionally, most of the OTA-producing isolates were of moderate toxigenicity, producing amounts of OTA from 10 μg g⁻¹ to 100 μg g⁻¹. Percentages of OTA-producing isolates in the A. niger aggregate were higher than in other substrates, ranging from 30% to 51.7%. Furthermore, the detected levels of OTA production in the A. niger aggregate, particularly in A. tubingensis species was higher than in A. carbonarius, ranging from 0.7 μg g⁻¹ to 120 μg g⁻¹ (mean 24.55 μg g⁻¹). Due to the high occurrence, percentage of ocratoxigenic isolates and their ability to produce OTA, isolates belonging to the A. niger aggregate could be considered as the main cause of OTA contamination in cocoa beans used for manufacturing cocoa products.     

Simultaneous and Direct Determination of As, Bi, Pb, Sb, and Se and Co, Cr, Cu, Fe, and Mn in Milk by Electrothermal Atomic Absorption Spectrometry

Tungsten permanent modifier with coinjection of Pd(NO₃)₂ and W–Ru permanent modifiers are proposed for the direct and simultaneous determination of As, Bi, Pb, Sb, and Se (group 1) and Co, Cr, Cu, Fe, and Mn (group 2), respectively, in milk by graphite furnace atomic absorption spectrometry. The performance of modifiers was evaluated by means of thermal behavior of analytes, sensitivity, atomic signal profile, repeatability, graphite tube lifetime, and background intensity. An air-assisted pyrolysis step was necessary to quantitative elimination of the organic matter. After methods optimization, 14 commercial milk samples were analyzed. The found concentrations of As, Bi, Pb, Sb, Se, Co, and Cr were lower than their limit of detection (2.13, 2.21, 1.49, 1.63, 2.05, 1.0, and 1.2 μg L⁻¹, respectively). Concentrations of Cu, Fe, and Mn were in the 1.58–5.74 μg L⁻¹, 9.79–49.3 μg L⁻¹, and 2.25–4.08 μg L⁻¹ intervals, respectively. The limits of detection for Cu, Fe, and Mn were 1.7, 5.3, and 2.0 μg L⁻¹, respectively. The accuracy of methods was checked after analysis of two milk standard materials. Results for Cr, Cu, Fe, Mn, Pb, and Mn were in agreement with certified values of SRMs at the 95% confidence level. Accuracy was also evaluated by addition–recovery tests and recoveries in the 86–127% range were obtained for all elements. The use of pretreat platform of graphite tubes with W or W–Ru allowed enlarging the lifetime of atomizer in 750 heating cycles.     

Micelle-Mediated Extraction and Flame Atomic Absorption Spectrometric Method for Determination of Trace Cobalt Ions in Beverage Samples

A new method has been developed for preconcentration of cobalt at trace levels in beverage samples using calcon carboxylic acid as chelating agent and cetyl pyridinium chloride as an auxiliary ligand and entrapped into Triton X-114 prior to its determination by flame atomic absorption spectrometry (FAAS). The main parameters affecting cloud point extraction (CPE) efficiency such as pH, concentration of the complexing agent, cationic and nonionic surfactant concentration, salt effect, the equilibrium time, and temperature were investigated and optimized. After optimization of the CPE conditions, a preconcentration factor of 60, an enhancement factor of 106, and a detection limit of 0.20 μg L⁻¹ by (R ² = 0.9978) were obtained from a calibration curve constructed in the range of 0.7–100 μg L⁻¹. The proposed preconcentration procedure was successfully applied to the determination of cobalt ions in some real samples including natural drinking water, tap water, and beer and wine samples. The accuracy and validity of the proposed CPE/FAAS method was tested by means of five repeated analysis of reference standard materials (TM-253, a low level fortified water standard for trace elements). A good agreement between analytical results (28.8 and 28.5 μg L⁻¹ with calibration curve and standard addition curve method, respectively) and certified value (27.9 μg L⁻¹) for Co (p < 0.05) were obtained and verified by means of calibration curve and standard addition curve method using CPE procedure.     

Polycyclic aromatic hydrocarbons (PAHs) in traditional and industrial smoked beef and pork ham from Serbia

Smoked beef and pork ham samples were analysed during process of smoking (after packing and storing) for the presence of the 16 EU priority PAHs via Fast GC/HRMS method. This study showed that there are differences in PAH contents between final smoked beef ham samples from traditional smokehouse (TS) (3.9 μg kg⁻¹) and industrial smokehouse (IS), (1.9 μg kg⁻¹). Also there is a difference in PAH contents in final smoked pork ham samples (4.9 μg kg⁻¹, TS; 4.2 μg kg⁻¹, IS). In beef and pork ham samples from the same smokehouse different PAH contents were observed during smoking. The highest content of examined PAHs in all beef and pork ham samples during smoking showed benzo[c]fluorene (BcL) (beef ham: from 0.3 μg kg⁻¹ to 1.5 μg kg⁻¹; pork ham: from 0.2 μg kg⁻¹ to 2.1 μg kg⁻¹).The maximum level for benzo[a]pyrene (BaP) of 5 μg kg⁻¹ in smoked meat products was not exceeded in any samples. Correlation statistic analysis (P < 0.05) of obtained contents from samples both from TS and IS showed that BaP is a good marker both for 16 EU priority PAHs and 12 IARC probably and possibly carcinogenic PAHs (IS: R _BaP/Σ16PAHs = 0.95, R _BaP/Σ12PAHs = 0.96; TS: R _BaP/Σ16PAHs = 0.71, R _BaP/Σ12PAHs = 0.88).     

Preparation of Alcalase-catalyzed casein plasteins in the presence of proline addition and the ACE-inhibitory activity of the plasteins in vitro

Casein hydrolysates were prepared by hydrolysis of casein with alkaline protease Alcalase for 6 h and showed the highest ACE-inhibitory activity in vitro with an IC₅₀ value of 47.1 μg mL⁻¹. Casein hydrolysates prepared were subjected to Alcalase-catalyzed plastein reaction in the presence or absence of proline addition to prepare casein plasteins. Some optimal reaction conditions of plastein reaction in the presence of proline addition were studied using response surface methodology with the decrease in free amino groups in the casein plasteins as response. When the concentration of casein hydrolysates was fixed at 35% (w w⁻¹) and reaction time at 6 h, the optimal conditions were reaction temperature 48 °C, addition level of proline 0.54 mol/mol free amino groups of casein hydrolysates and addition level of Alcalase 9.5 kU g⁻¹ proteins. With these conditions, the maximal decrease in free amino groups in casein plasteins was 195.7 μmol g⁻¹ proteins. The ACE-inhibitory activities of twelve casein plasteins in vitro, prepared in the presence or absence of proline addition with different reaction extents, were evaluated and compared. The results showed that the ACE-inhibitory activity of the casein plasteins prepared in the presence of proline addition changed irregularly, different to that of the casein plasteins prepared in the absence of proline addition, and might relate to the different linking of proline to the peptides in casein hydrolysates during plastein reaction. When the casein plasteins prepared in the presence of proline addition had a decrease in free amino groups 195.7 μmol g⁻¹ proteins, the IC₅₀ value of the casein plasteins was lowered to 0.2 μg mL⁻¹.     

Development of an Analytical Method Based in the Slurry Sampling for Iron Determination in Fortified Milk Powder by HR-CS FAAS

The use of slurry sampling as the procedure for sample preparation provides simplicity, speed, and low consumption of reagents in analytical methods. In this paper, a method based on slurry sampling for the determination of iron in samples of fortified milk powder by high-resolution continuum source flame atomic absorption spectrometry was developed. Multivariate design techniques were applied for the optimization of experimental conditions of the method for a sample mass of 100 mg, final volume of slurry of 10 mL, and using the absorbance signal as response. Initially, a two-level full factorial design was used for the preliminary evaluation of the variables involved in slurry preparation: concentration hydrochloric acid, Triton X-100 concentration, and sonication time. Then, the Doehlert matrix was applied for the determination of the critical conditions: 2.5 mol L⁻¹ hydrochloric acid and sonication time of 20 min. External calibration technique with aqueous standard was used for the quantification of iron. This way, the method allowed iron determination with limits of detection and quantification of 0.9 and 3.0 μg g⁻¹, respectively. The precision expressed as the relative standard deviation was evaluated under repeatability and reproducibility conditions, being 3.2% and 4.0%, respectively. Addition/recovery test was used for assessing the accuracy of the method, and the recovery values achieved were in the range of 90–110%. The method was applied for iron determination in eight samples of fortified milk powder, and the obtained concentrations varied from 95.4 to 295.6 μg g⁻¹. The results were compared with those obtained after acid digestion, and no significant difference was observed applying t test at the 95% confidence level.     

Separation‐preconcentration of Cu,Cd, Pb and Ni in various water and food samples on Sepabeads SP‐207

This study presents a solid phase extraction (SPE) procedure for preconcentration and separation of Cu(II), Cd(II), Pb(II) and Ni(II), as their diethyldithiocarbamate chelates on Sepabeads SP‐207 resin using flame atomic absorption spectrometry. The parameters, including pH, sample volume, eluent type and volume etc., were optimised. The influences of the some alkali, alkali earth and transition metal ions on the involvement of copper(II), cadmium(II), lead(II) and nickel(II) were also examined. The preconcentration factor was calculated as 50. The limit of detections of the analyte ions (k = 3, N = 21) were 0.18 μg L^?1 (Cu), 0.17 μg L^?1 (Cd), 0.55 μg L^?1 (Pb) and 1.67 μg L^?1 (Ni). GBW 07605 Tea and NRCC‐DORM‐2 Dogfish Muscle certificated reference materials were used for confirm of method. The method was successfully performed for determination of Cu(II), Cd(II), Pb(II) and Ni(II) ions in water and food samples. The relative standard deviation was found to be lower than 7%.     

Effect of dynamic high-pressure microfluidization at different temperatures on the antigenic response of bovine β-lactoglobulin

The antigenic response of β-lactoglobulin (β-Lg), treated by dynamic high-pressure microfluidization (DHPM) at different temperatures, was determined by an indirect competitive enzyme-linked immunosorbent assay using polyclonal antibodies from rabbit serum. DHPM treatment causes changes in the protein structure and may influence the antigenicity of β-Lg. DHPM treatment of β-Lg at 90 °C showed significant effects with the antigenic response of 5.2 μg mL⁻¹ (untreated), 45 μg mL⁻¹ (40 MPa), 79 μg mL⁻¹ (80 MPa), 132 μg mL⁻¹ (120 MPa), and 158 μg mL⁻¹ (160 MPa). In combination with temperature treatment (70–90 °C), the antigenic response enhanced as the temperature increased at 160 MPa. The β-Lg antigenicities were about 14, 108, and 158 μg mL⁻¹ at 70, 80, and 90 °C, respectively. However, the influence of DHPM pressures on the antigenic response of β-Lg standards was different. DHPM modified β-Lg standards showed a remarkable increase in antigenicity when treated to 80 MPa. Above 80 MPa, the antigenic response decreased.     

Determination of copper in fish feed by graphite furnace atomic absorption spectrometry using slurry sampling

The present work develops and optimizes a method to determine copper in samples of feces and fish feed by graphite furnace atomic absorption spectrometry (GFAAS) through the direct introduction of slurries of the samples into the spectrometer’s graphite tube coated internally with metallic rhodium and tungsten carbide that acts as chemical modifiers. The limits of detection (LOD) and quantification (LOQ) calculated for 20 readings of the blank of the standard slurries (0.50% m/v of feces or feed devoid of copper) were 0.24 and 0.79 μg L⁻¹ for the standard feces slurries and 0.26 and 0.87 μg L⁻¹ for the standard feed slurries. The proposed method was applied in studies of absorption of copper in different fish feeds and their results proved compatible with that obtained from samples mineralized by acid digestion using microwave oven.     

Chitosan, chitin-glucan and chitin effects on minerals (iron, lead, cadmium) and organic (ochratoxin A) contaminants in wines

Chitosan (F7), chitin (F2), chitin-glucan (F1) and chitin glucan hydrolysate (F5) of fungal origin were tested for removal of mineral (Fe or Pb and Cd) and organic (ochratoxin A: OTA) contaminants in wines. Red, white and sweet wines are spiked with either Fe (20 mg L⁻¹), or Pb (500 μg L⁻¹) and Cd (20 μg L⁻¹) or OTA (5 μg L⁻¹). The wines were then treated with F1, F2, F5 or F7 at doses of 0.1 g, 0.5 and 2 g L⁻¹. After 2 days, the levels of iron, copper, lead and cadmium were measured using a flame and graphite furnace atomic absorption spectrophotometer. Depending on the treatment red wines showed reductions of iron by 73–90%, cadmium by 29–57% and lead by 33–74%. The same treatments with white wine gave reductions for iron of 32–91%, cadmium fell by 11–23%, lead by 50–65%. In the case of sweet wines iron was reduced by 51–90%, cadmium by 17–25%, and lead by 38–84%. For wine enriched in OTA, treatments with F1, F2, F5, F7 were carried out at doses of 2 and 5 g L⁻¹. After 2 days, the levels of OTA in wines were analyzed by HPLC with fluorimetric detection. OTA was reduced by 56.7–83.4% in red wine, by 53.4–64.5% in white wine and 26.1–43.5% in sweet wine. These findings indicate that chitosan, chitin, chitin-glucan, or chitin glucan hydrolysate from fungal origin may be useful ancillaries for wine limpidity prevention by reducing levels of Fe, heavy metals (Pb, Cd) and mycotoxins (OTA) and thereby improving wine safety.     

Study of a microwave digestion method for total arsenic determination in marine mussels by electrothermal atomic absorption spectrometry: application to samples from the Ria de Arousa

Arsenic determination in mussel tissue was performed by electrothermal atomic absorption spectrometry (ETAAS) with Zeeman background correction and using iridium as a chemical modifier. Samples were digested by microwave heating using a mixture of nitric and sulphuric acids. This mixture makes possible the destruction of organoarsenic compounds, specifically arsenobetaine, prior to the graphite furnace determination. Optimum pyrolysis and atomization temperatures were 1,100 and 1,800 °C, respectively. The method was precise (with RSD% < 10), accurate (study of a certified reference material: 18.4 ± 1.4 μg As g⁻¹ vs. a certified content: 18.0 ± 1.1 μg As g⁻¹; recoveries between 90 and 104%) and sensitive (LOD 0.21 μg g⁻¹ on a dry weight basis). The method was applied to the determination of arsenic in aquaculture mussels collected in four sampling campaigns from the productive Ría de Arousa (estuary sited in Galicia, NW of Spain).     

Determination of Melamine in Liquid Milk and Milk Powder by Titania-Based Ligand-Exchange Hydrophilic Interaction Liquid Chromatography

A simple and rapid high-performance liquid chromatography (HPLC) procedure for the analysis of melamine in liquid milk and milk powder has been developed. Decrease of acetonitrile percentage and phosphate buffer concentration in mobile phase, and lowering of buffer pH and column temperature would benefit the retention of melamine on titania. Taking advantage of the ligand-exchange and hydrophilic interaction mixed retention mode on bare titania column, neither complex pretreatment nor ion-pair reagent was required. The whole analysis for one sample including sample pretreatment and HPLC analysis could be accomplished within 30 min. The method presented good linearity (R ² = 0.9998) in a wide range of 0.02–10 μg mL⁻¹. The limit of detection (3σ) and limit of quantification (10σ) of the method were 6 and 20 μg L⁻¹, respectively, which were equivalent to 15 and 50 μg kg⁻¹ melamine in liquid milk, 60 and 200 μg kg⁻¹ melamine in milk powder, respectively. Such sensitivity could be compared with those obtained by HPLC with solid-phase extraction or HPLC coupled with tandem mass spectrometry and was adequate for the screening of melamine in tainted dairy products. The repeatability (RSDs) of the retention times and peak areas of 11 replicate detections of 1.0 μg mL⁻¹ melamine were 0.32% and 2.5%, respectively. The intermediate precision on three consecutive days (RSDs, n = 6) of the retention times and peak areas were 1.1% and 2.3%, respectively. The recovery of spiked melamine in dairy samples ranged from 95.2% to 105%. The simplicity, sensitivity and rapidity of the proposed method make it an effective alternative detecting technique for melamine.     

On-line Solid-Phase Extraction Coupled to Liquid Chromatography–Ion Trap Tandem Mass Spectrometry for Determination of Penicillins in Catfish

A highly selective method was developed for the simultaneous determination of eight penicillins in catfish using automated on-line solid-phase extraction coupled to liquid chromatography–tandem mass spectrometry (XLC–MS/MS). The type of cartridge, equilibration sample volume, volume of solvent to carry the sample into the cartridge, and elution times were studied in order to optimize the XLC operating conditions. MS/MS conditions were also adjusted for better peak resolution. The present method was validated in agreement with the criteria of Commission Decision 2002/657/EC, showing a linear range from 2 to 350 μg kg⁻¹ and regression coefficient higher than 0.995 for the studied penicillins. Decision limits, calculated in the case of substances with no permitted limit, were lower than 0.6 μg kg⁻¹, and detection capability values were lower than 2.0 μg kg⁻¹. Samples spiked at 2.0, 10.0, and 50.0 μg kg⁻¹ showed high recovery (72–92%) and precision values lower than 20% except for amoxicillin. The present method was also applied for the analysis of penicillins in 30 catfish samples bought in local markets.     

Effects of Maillard reaction conditions on the antigenicity of α-lactalbumin and β-lactoglobulin in whey protein conjugated with maltose

The effects of Maillard reaction conditions (weight ratio of protein to sugar, temperature and time) on the antigenicity of α-lactalbumin (α-LA) and β-lactoglobulin (β-LG) in conjugates of whey protein isolate (WPI) with maltose were investigated. Response surface methodology was used to establish models to predict the antigenicity of α-LA and β-LG and find an optimal reaction condition under which the antigenicity of α-LA and β-LG reduces to minimum value. Conjugating WPI with maltose was an effective way to reduce the antigenicity of α-LA and β-LG. The antigenicity of α-LA decreased from 32.25 μg mL⁻¹ to 10.91 μg mL⁻¹. And the antigenicity of β-LG decreased from 272.4 μg mL⁻¹ to 38.17 μg mL⁻¹. Temperature had the greatest effect on the antigenicity of α-LA, while weight ratio of WPI to maltose was the most significant factor on the antigenicity of β-LG.     

Analysis of phenolic compounds and isoflavones in soybean seeds (Glycine max (L.) Merill) and sprouts grown under different conditions

Soybeans (Glycine max (L.) Merill) are popularly known as a healthy food in many Asian countries and are mostly consumed as soymilk, tofu, and fermented products such as miso, temph, and sufu. The objective of this study was to determine the variation and composition of phenolic compounds and isoflavone contents in soybean seeds [Glycine max (L.) Merill] and sprouts [Kongnamul] grown under dark conditions (producing yellow soybean sprouts) and in green and yellow boxes (producing green soybean sprouts). In seven soybean cultivars, the total phenolic content ranged from 6.67 μg⁻¹ in Pureunkong to 72.33 μg⁻¹ in Poongsannamulkong. The average total phenolic content in the green soybean sprouts (48.33 μg⁻¹) was higher than in the yellow soybean sprouts (29.75 μg⁻¹). The total phenolic content in the yellow soybean sprouts varied from 9.88 μg⁻¹ to 47.71 μg⁻¹, and the total phenolic content in the green soybean sprouts varied from 29.21 μg⁻¹ to 79.70 μg⁻¹. Only four phenolic compounds, p-hydroxybenzoic acid, salicylic acid, p-coumaric acid, and ferulic acid, were detected in all soybean cultivars. Syringic acid was not detected in yellow soybean sprouts, and myricetin was only detected in yellow soybean sprouts (4.65 μg⁻¹) from the Pureunkong cultivar grown under dark conditions. The total isoflavone content in soybean seeds ranged from 2.1 μg⁻¹ in Sowonkong to 33.0 μg⁻¹ in Pureunkong, and the mean total isoflavones was 10.61 μg⁻¹. Green soybean sprouts had higher average total isoflavones (1389.4 μg⁻¹) than yellow soybean sprouts (559.2 μg⁻¹), and the total isoflavone content was highest in the Pureunkong yellow soybean sprouts (756.3 μg⁻¹) and the Sowonkong green soybean sprouts (2791.6 μg⁻¹). In soybean sprouts, the higher the (malonyl)-daidzin or (malonyl)-genistein content, the higher the total isoflavone level. Our study suggests that producing soybean sprouts enriched in isoflavones under coloured-light sources is feasible.     

Optimization and Modeling of Process Parameters for Lipase Production by Bacillus brevis

Statistical evaluation of fermentation conditions and nutritional factors by Plackett–Burman two-level factorial design followed by optimization of significant parameters using response surface methodology for lipase production by Bacillus brevis was performed in submerged batch fermentation. Temperature, glucose, and olive oil were found to be the significant factors affecting lipase production. Maximum lipase activity of 5.1 U ml⁻¹ and cell mass of 1.82 g l⁻¹ at 32 h were obtained at the optimized conditions of temperature, 33.7 °C; initial pH, 8; and speed of agitation, 100 rpm, with the medium components: olive oil, 13.73 ml l⁻¹; glucose, 13.98 g l⁻¹; peptone, 2 g l⁻¹; Tween 80, 5 ml l⁻¹; NaCl, 5 g l⁻¹; CH₃COONa, 5 g l⁻¹; KCl, 2 g l⁻¹; CaCl₂·2H₂O, 1 g l⁻¹; MnSO₄·H₂O, 0.5 g l⁻¹; FeSO₄·7H₂O, 0.1 g l⁻¹; and MgSO₄·7H₂O, 0.01 g l⁻¹. The lipase productivity and specific lipase activity were found to be 0.106 U (ml h)⁻¹ and 2.55 U mg⁻¹, respectively. Unstructured kinetic models and artificial neural network models were used to describe the lipase fermentation. The kinetic analysis of the lipase fermentation by B. brevis shows that lipase is a growth-associated product.     

Assay of Total Mercury in Commercial Food Supplements of Marine Origin by Means of DLLME/ICP-AES

In this work, we have developed a sensitive and cost-effective preconcentration and quantification methodology for total mercury (Hg) at trace levels in food supplements of marine origin. Dispersive liquid–liquid microextraction was successfully employed for the preconcentration of mercury at trace levels prior to inductively coupled plasma atomic emission spectrometry. The mercury was extracted as mercury-1, 5-diphenyl-3-formazathiol complex, at pH 1.0 mediated by multidroplet formation of microextraction solvent assisted by disperser solvent. The lower limit of detection obtained under the optimal conditions was 0.24 μg L⁻¹. The calibration graphs were linear up to 500 μg L⁻¹. The precision of the method in terms of relative standard deviation was 4.8% for the concentration of 100 μg L⁻¹. In order to validate the proposed method, a certified reference material RTC-QCI-049 was analyzed with the proposed procedure. Moreover, potential interference by 20 species was also evaluated.