A novel application of mesoporous silica material for extraction of pesticides

The mesoporous silica material MCM-41 was prepared by the sol-gel method and characterized using X-ray diffraction (XRD), N₂ adsorption-desorption and thermogravimetric analysis. The material was tested for extraction of trichlorfon, pyrimethanil, tetraconazole, thiabendazole, imazalil and tebuconazole from mango fruit, with analysis using gas chromatography-mass spectrometry (GC/MS). In experiments carried out in triplicate, at a 1.0 mg/kg concentration level, recoveries using the MCM-41 sorbent were in the range 73-103%. Comparison of MCM-41 with commercially available silica gel showed that MCM-41 was a similar extracting phase for the pesticides investigated with a significant cost advantage over this conventional material.     

Anodic substitution in emulsions under phase transfer catalysis conditions. II. Acetoxylation of dimethoxybenzenes

The anodic acetoxylation of 1,2-dimethoxybenzene in H₂O-CH₂Cl₂ emulsions with different phase transfer agents (nBu₄N⁺HSO ₄ ⁻ ,nBuP⁺ φ ₃Br⁻, Aliquat 336, Hyamine 1622 and CTAB) has been investigated. The conversion rates and the electrochemical efficiencies are mainly governed by two parameters: (a) the anode wetting by an organic layer which varies with the nature of the catalyst as shown by the preparative polarization curves; (b) the competitive oxidation of the counter-ions present in the organic phase (CH₂C1₂). The latter point is very important in the case of bromide salts. On the basis of these observations, the use ofnBu{4}N⁺HSO ₄ ⁻ appears to be the best compromise for the case of anodic acetoxylation of aromatic substrates in the media studied.     

Utilisation of pectin coating to enhance spray-dry stability of pea protein-stabilised oil-in-water emulsions

In this study, development of pea (Pisum sativum) protein stabilised dry and reconstituted emulsions is presented. Dry emulsions were prepared by spray-drying liquid emulsions in a laboratory spray-dryer. The effect of drying on the physical stability of oil-in-water emulsions containing pea protein-coated and pea protein/pectin-coated oil droplets has been studied. Oil-in-water emulsions (5 wt.% Miglyol 812 N, 0.25 wt.% pea protein, 11% maltodextrin, pH 2.4) were prepared that contained 0 (primary emulsion) or 0.2 wt.% pectin (secondary emulsion). The emulsions were then subjected to spray-drying and reconstitution (pH 2.4). The stability of the emulsions to dry processing was then analysed using oil droplet size, microstructure, Zeta potential, and creaming measurements. Obtained results showed that the secondary emulsions had better stability to droplet aggregation after drying than primary emulsions. To interpret these results, we propound that pectin, an anionic polysaccharide, formed a less charged protective layer around the protein interfacial film surrounding the oil droplets that improved their stability to spray-drying mainly by increasing steric effects.     

Microbiological,physical and chemical characteristics of freshwater prawns (Macrobrachium rosenbergii) in modified‐atmosphere packaging

This study evaluated the influence of packaging atmosphere (air versus 50% N₂/50% CO₂) on microbiological (mesophiles, psychrotrophs), physical (gas measurement) and chemical (pH, total volatile basic nitrogen [TVB‐N], NH₃, H₂S and biogenic amines) parameters in freshwater prawns during storage at 0 ± 1 °C for 240 h. To select the most appropriate packaging, 21 batches of each treatment were analysed. Both the packaging permeability and the combination of gases affected the shelf life, but the modified‐atmosphere packaging (MAP) was more efficient than air packaging, increasing the shelf life by 40 h. The parameters of pH and TVB‐N showed no statistical difference between the two atmosphere conditions all along the storage period. The biogenic amine agmatine showed potential for use as a quality indicator due to the increased concentration during storage. In further studies, this amine can be applied as an indicator for public health issue.     

Effect of Aqueous Extract of the Seaweed Gracilaria domingensis on the Physicochemical,Microbiological, and Textural Features of Fermented Milks

The effects of the Gracilaria domingensis seaweed aqueous extract in comparison with gelatin on the physicochemical, microbial, and textural characteristics of fermented milks processed with the mixed culture SAB 440 A, composed of Streptococcus thermophilus, Lactobacillus acidophilus, and Bifidobacterium animalis ssp. lactis, were investigated. The addition of G. domingensis aqueous extract did not affect pH, titratable acidity, and microbial viability of fermented milks when compared with the control (with no texture modifier) and the products with added gelatin. Fermented milk with added the seaweed aqueous extract showed firmness, consistency, cohesiveness, and viscosity index at least 10% higher than those observed for the control product (P < 0.05). At 4 h of fermentation, the fermented milks with only G. domingensis extract showed a texture comparable to that observed for products containing only gelatin. At 5 h of fermentation, firmness and consistency increased significantly (P < 0.05) in products with only seaweed extract added, a behavior not observed in products with the full amount of gelatin, probably due to the differences between the interactions of these ingredients with casein during the development of the gel network throughout the acidification of milk. The G. domingensis aqueous extract appears as a promising gelatin alternative to be used as texture modifier in fermented milks and related dairy products.     

Effect of iron chelates on oil–water interface,stabilized by milk proteins: The role of phosphate groups and pH. Prediction of iron transfer from aqueous phase toward fat globule surface by changes of interfacial properties

Iron incorporated into food systems induces oxidation and precipitation. The consequences are reduced bioavailability and a functional modification of other food components such as proteins. The iron-chelates such as ferrous bisglycinate represent a possibility to avoid side effects, since the iron is protected. The aim of this study is to investigate the effects of iron-chelates compounds on the properties of an oil/water interface stabilized by caseinate or β-lacotoglobulin, under environmental conditions at 20 °C. Analyses were performed using dynamic drop tensiometry during 5000 s. The aqueous bulk phase is an imidazole/acetate buffer (0.1 M), containing 0.4 × 10⁻⁶ M protein, and 0.2 × 10^-6 9 M iron-chelates compounds. The results indicate that, under neutral conditions, the addition of some irons salts (NaFe-EDTA or Fe-bisglycinate) do not change the structure of the interface stabilized by a protein containing no phosphate groups (β-lactoglobulin). In the case of caseinate, NaFe-EDTA addition increases the lowering rate of surface tension at pH 6.5. On the contrary, the lowering rate of surface tension with caseinate is inhibited by Fe-bisglycinate at pH 6.5. Such an effect is not observed with β-lactoglobulin. The low transfer of irons ions from the bulk to the interface stabilized by β-lactoglobulin is confirmed by zetameter and FTIR measurements. These results indicate an effective strategy to follow for controlling the physical and chemical stability of an emulsion stabilized with proteins.     

Polyphenol oxidase activity,phenolic acid composition and browning in cashew apple (Anacardium occidentale, L.) after processing

This study describes the extraction and characterisation of cashew apple polyphenol oxidase (PPO) and the effect of wounding on cashew apple phenolic acid composition, PPO activity and fruit browning. Purification factor was 59 at 95% (NH₄)₂SO₄ saturation. For PPO activity, the optimal substrate was catechol and the optimum pH was 6.5. PPO K_m and V_max values were 18.8 mM and 13.6 U min⁻¹ ml⁻¹, respectively. Ascorbic acid, citric acid, sodium sulphite and sodium metabisulphite decreased PPO activity, while sodium chloride increased PPO activity. Wounding at 2 °C and 27 °C for 24 h increased PPO activity but storage at 40 °C reduced PPO activity. Gallic acid, protocatechuic acid and cinnamic acid (free and conjugate) were identified in cashew apple juice. Cutting and subsequent storage at 40 °C hydrolysed cinnamic acid. 5-Hydroxymethylfurfural content in cashew apple juice increased after injury and storage at higher temperatures, indicating non-enzymatic browning.     

Comparison of vacuum impregnation and soaking techniques for addition of the probiotic Lactobacillus acidophilus to minimally processed melon

This study aimed to evaluate the vacuum impregnation (VI) and soaking methods in the addition of Lactobacillus acidophilusLA‐3 to minimally processed melon (MPM). The melons were washed, sanitised in chlorine solution (200 mg L^?1), peeled and cutted into cubes. Lactobacillus acidophilusLA‐3 (1.4 × 10¹⁰ CFU g^?1) were added to the MPM through both techniques. The L. acidophilusLA‐3 count in MPM was similar to those commonly found in dairy products having probiotic claim, but VI was more efficient than soaking in maintaining the viability (8.61 and 7.98 Log CFU g^?1, respectively). The pH, acidity and soluble solids were not affected by probiotic culture and the incorporation technique; however, the VI affected the firmness of fruit. The MPM was within Brazilian standards for their microbiological characteristics. MPM may be used as a carrier of probiotic bacteria, being one more alternative for individuals who consume probiotic products.     

Contribution to the study of carbon deposition in coke ovens

The formation of carbon deposits from coal pyrolysis in a two-stage reactor has been studied for several cracking temperatures from 850 to 1000 °C. The weight of the carbon deposit was monitored continuously during pyrolysis by a thermogravimetric balance. Four successive periods of deposition can be distinguished:

1. (1) no weight uptake;

2. (2) a slow increase in weight;

3. (3) a sharp increase in weight;

4. (4) constant weight.

From the data, three distinct deposition rates have been calculated at different cracking temperatures: germination rate, growth rate and overall deposition rate. The general tendency is an increase in all three deposition rates with temperature. Scanning electron and polarized light micrographs of these deposits show that they have a laminar structure. There are two (sometimes three) cone layers, the first being formed during the liberation of water contained in the coal charge, indicating that water plays the role of an inhibitor in the formation of carbon deposits. The structure of the deposits is independent of the temperature at which deposition takes place. The mechanism of this carbon formation is discussed.     

Updates on biogas enrichment and purification methods: A review

The market for biogas production has been increasing every year all over the world. The use of biogas as an energy vector is accomplished through the most diverse applications, such as direct burning (thermal energy), internal combustion engines, and fuel cells. Besides direct applications, biogas can be used as a raw material for producing high added-value products, such as molecular hydrogen and renewable hydrocarbons, through a new enterprise concept, the biorefineries. Purity and quality control are determinant factors that enable the decision-making regarding the end use of biogas. Physical, chemical, and biological methods can be used in biogas upgrading processes as well as a combination of different techniques. This review aims to deepen the knowledge about relevant technologies for biogas purification. It also addresses the most efficient and feasible methods, challenges to be overcome, and main demands for future studies. Therefore, the presentation, in a detailed way, of the synergistic effects caused by components contained in natural biogas and the combinatorial methods for removing these contaminants, differentiates this from other works that approach only the purification techniques but do not point out their problems and causes more comprehensively. Thus, studies related to the combined effects of contaminants would be interesting in future works.