Chemical Dip Research Articles

Chemical dips and edible coatings to retard softening and browning of fresh-cut banana

The effects of chemical dips and edible coatings on firmness and colour of fresh-cut banana (cv. Cavendish) from Madeira Island were investigated. Two calcium salts, calcium chloride and calcium lactate, were first investigated for the effects on firmness during four days of storage at 5°C. Firmness and colour were evaluated after a three-minute chemical dipping or chemical dipping followed by coating and during five days of storage at 5°C. The coatings tested consisted of pectin, alginate, carboxymethylcelullose, carrageenan or chitosan solution. Dip with 1% (w/v) calcium chloride, 0.50% (w/v) ascorbic acid and 0.75% (w/v) cysteine was the most efficient treatment in retarding softening and browning of banana slices. This dip also inhibited yeast growth. According to sensory analysis, the edible shelf life of banana slices dipped in such solution was the longest: five days at 5°C. Carrageenan solution was the significantly (p < 0.05) best coating among the ones studied, in preserving firmness and colour of fresh-cut banana during five days at 5°C.

Quantitative analysis of a chemical treatment to reduce roughness of parts fabricated using fused deposition modeling

The surface finish of Fused Deposition Modeled (FDM) parts can be improved by performing chemical dipping based on immersion in a dimethylketone–water solution. The authors aim to gain a more in-depth knowledge of this process, by analyzing and comparing the mechanical properties and the surface quality of treated and untreated FDM parts. Tensile and bending mechanical properties have been investigated by designing and performing four Central Composite Designs (CCDs) of experiments, totalizing about two-hundred tests. The results have been verified by testing an FDM marine turbine blade employed to generate energy.

Improving the Microbial Quality and Shelf Life of Chicken Carcasses by Trisodium Phosphate and Lactic Acid Dipping

This study determined the influence of Trisodium Phosphate (TSP) and Lactic Acid (LA) dipping on the microbial load and shelf life of broiler chicken carcasses during refrigerated storage for 8 days at 2±1 C. The results indicated that both TSP (12%) and LA (2%) dipping significantly reduced the initial o microbial load of Aerobic Plate Counts (APC), Psychrotrophic Counts (PTC), Total Proteolytic Counts (PLC) and Enterobacteriaceae Counts (EBC) just after dipping and throughout the storage period in comparison with the control. At the beginning of storage (day 0), no significant differences in the microbial reductions were detected between TSP and LA treatments. By the day 8 of the storage, however, LA-dipping indicated a higher (p<0.01) mean reductions in APC, PTC and PLC than the corresponding reductions obtained by TSP-dipping. The untreated carcasses would have a refrigerated shelf life between 4 and 5 days while after chemical dipping, the shelf life extended to about 7 days in TSP-treated carcasses and 8 days in LA-treated carcasses. Therefore, both TSP and LA can be applied on poultry carcasses to reduce their microbial load and extend their shelf life during refrigerated storage.

Stable aluminium ohmic contact to surface modified porous silicon

A stable low resistance aluminium (Al) contact to porous silicon (PS) could be achieved by chemically modifying PS surface with palladium chloride (PdCl2) solution. Palladium (Pd) was dispersed over the PS surface by chemical dipping method using very low concentration of PdCl2 solution (0.01M) and for a very short duration of time (5s). Field emission scanning electron microscopy (FESEM) was performed to investigate the morphology of the modified PS surface. Digital X-ray image mapping and energy dispersive X-ray (EDAX) spectras were taken to confirm the dispersion and formation of Pd clusters on the porous silicon surface. X-ray photoemission spectroscopy (XPS) confirms that the presence of oxygen is higher in Pd modified porous silicon than that of unmodified one. Aluminium (Al) was thermally evaporated on Pd modified surfaces and the study of J–V characteristics showed a linear relationship. Therefore the specific contact resistance (ρc) could be measured by transmission line model (TLM) method. Stability of the contact was studied for a time period of around 30days and no significant ageing effect could be observed.

Effect of chemical and biological dipping on acrylamide formation and sensory properties in deep-fried potatoes

The objective of this work was to study the effect of chemical and biological pre-treatments on acrylamide formation in deep-fried potatoes. Prior to deep-frying, potatoes cubes were subjected to lactic acid fermentation in the presence or in the absence of glycine, as well as to immersion in an aqueous solution of the amino acid alone. The effects of each pre-treatment on deep-fried potatoes were compared by evaluating acrylamide formation, browning development as well as sensory attributes and preference. Results showed that deep-fried potatoes subjected to the glycine and fermentation pre-treatments had 35% and 50% less acrylamide content than the water-dipped ones. Lactic acid fermentation in the presence of glycine resulted the most effective in decreasing acrylamide formation up to 70%. Such a pre-treatment did not affect the sensory perceived browning, flavour, sourness and crispness of the deep-fried potatoes. Moreover, according to the results of a pair comparison preference test, no significant differences in preference were found among the samples.

Combined effects of chemical dip and/or carrageenan coating and/or controlled atmosphere on quality of fresh-cut banana

The combined effect of chemical dip and/or edible coating and/or controlled atmosphere (CA) on quality of fresh-cut banana was investigated. Banana slices were subject to a 3-min dip into a solution containing 1% (w/v) calcium chloride, 0.75% (w/v) ascorbic acid and 0.75% (w/v) cysteine and/or combined with a carrageenan coating and/or combined with controlled atmosphere (3% O 2 + 10% CO 2). Physico-chemical and microbiological qualities were evaluated during 5 days of storage at 5 °C. Dip combined with CA treatment prevented product weight loss and increase of polyphenol oxidase activity during the 5 days of storage. Colour, firmness, pH, tritatable acidity and total soluble solids values and total phenolic content presented the smallest changes. Microbial analysis showed that minimally processed bananas were within the acceptable limits during 5 days of storage at 5 °C.

Optimization of growth conditions of ZnO nano thin films by chemical double dip technique

Zinc oxide (ZnO) nano thin films have been deposited by the chemical double-dip technique using aqueous ZnSO4 and NaOH solutions. The ZnO films were characterized in terms of surface morphology by x-ray diffraction, energy-dispersive x-ray analysis (EDX), the use of a scanning electron microscope (SEM) and atomic force microscope (AFM) for surface morphology. The films exhibited a smooth morphology. The chemical states of oxygen and zinc in the ZnO nano thin films were also investigated by x-ray photoelectron spectroscopy (XPS). In the present investigations, highly textured ZnO thin films with a preferential (002)-orientation were prepared on glass substrates. The deposition conditions were optimized to obtain device-quality films for practical applications.

Size-Dependent Gas Sensing Properties of Indium Oxide Nanoparticle Layers

In2O3 nanoparticle layers having an average size of 8, 11, 15, 21, and 29 nm have been deposited using a two-step method consisting of chemical capping and dip coating techniques. The gas sensing properties in terms of sensor response and response time of the nanoparticle layers towards ethanol have been studied as a function of ethanol concentration and operating temperature. It has been observed that the sensor response increases and the response time decreases with decreasing size in the size range of 5-15 nm. The increase in sensor response at smaller nanoparticle size has been explained in terms of the increase in surface area and particle size becoming comparable to the electron Debye length.

Effect of Silver Addition on the Ethanol-Sensing Properties of Indium Oxide Nanoparticle Layers: Optical Absorption Study

In2O3andIn2O3:Ag nanoparticle layers have been deposited using a two-step method consisting of chemical capping and dip coating techniques. The result of optical absorption analysis ofIn2O3:Ag samples shows the presence ofAg2Oand Ag in air-annealed and vacuum-annealed samples, respectively. These results have been correlated with the gas sensing properties of these layers towards ethanol and support the proposed mechanism that increase in sensor response on Ag addition is due to the conversion ofAg2Oto Ag in the presence of ethanol.

Structural, compositional, thermal resistant and hydro-oleophobic properties of fluorine based block-co-polymer films on quartz substrates by wet chemical process

Abstract Crack free and smooth surfaces of poly [4,5-difluoro 2,2-bis (trifluoromethyl)-(1,3 dioxole)- co -tetrafluoroethylene] (TFE- co -TFD) thin films have been deposited by wet chemical dip coating technique on polished quartz and glass slide substrates. The deposited films have been subjected to annealing at different temperatures ranging from 100 to 500 °C for 1 h in argon atmosphere. The elemental composition of the as-deposited (xerogel) thin film as well as film annealed at 400 °C was measured by X-ray photoelectron spectroscopy and observed that there was no change in the composition of the film. X-ray diffraction pattern revealed the amorphous behaviour of both as-deposited and film annealed at 400 °C. Surface morphology and elemental composition of the films have been examined by employing scanning electron microscopy attached with energy dispersive X-ray analyser, respectively. It was found that as the annealing temperature increased from 100 to 400 °C, nano-hemisphere-like structures have been grown, which in turn has shown increase in the water contact angle from 122 o to 148 o and oil (peanut) contact angle from 85° to 96°. No change in the water contact angle (122°) has been observed when the films deposited at room temperature were heated in air from 30 to 80 °C as well as exposed to steam for 8 days for 8 h/day indicating thermal stability of the film.

Unprecedented coloration of rutile titanium dioxide nanocrystalline thin films

In this communication, TiO 2 nanocrystalline thin films synthesized by a room temperature (27 °C) chemical dip process. To our knowledge, this is first report of the preparation of nanoscale rutile TiO 2 particles from common inorganic salt at such low temperature. Interestingly, unprecedented dynamic color change accompanies with titanium dioxide grain size, which can be seen with the naked eye that generated curiosity in our mind to check UV–vis absorption, where significant changes were observed. The room temperature synthesized thin films of rutile titanium dioxide make it a potential candidate for high-compatibility material, which can be used in artificial heart valves.

Chemical deposition of ZnO films from ammonium zincate bath

Zinc oxide (ZnO) thin films were deposited from ammonium zincate bath following a chemical dipping technique. Films in the thickness range 0.25–4.0 μm could be prepared by varying the ammonium zincate bath concentration (in the range 0.03–1.5 M) and number of dipping (0–200). Higher values of bath concentration produced nonadherent and poor quality films. The film growth rate was found to be a sensitive function of bath pH. The critical range of pH value for adherent and good quality films was found to be 11.0–11.1. Structural characterization by scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicate the formation of polycrystalline ZnO with strong c-axis orientation. The films were found to be highly resistive with dark resistivity of the order of 10 5 Ω cm. The electrical conductance was studied in the temperature range 300–650 K. The characteristic effect of chemisorption was found to influence the electrical properties of the films.

Redox and photochemical behaviour of a porphyrin monolayer on an indium-tin oxide electrode

In order to investigate photoluminescence behaviour of an ordered molecular porphyrin monolayer and its quenching properties by oxygen gas, a porphyrin with long alkyl chains, 5,10,15,20-tetrakis[4-(11-carboxylundecane-1-oxy)phenyl]porphyrin ( 4), was synthesized and adsorbed onto an indium-tin oxide (ITO) substrate by a chemical dipping method. Cyclic voltammetry was used to analyze the ITO electrode coated with 4. The peak current of the first oxidation was proportional to the sweep rate, and the surface coverage was estimated to be 2.3–2.5 × 10 −10 mol cm −2. The UV–vis spectrum of the monolayer showed a broadened Soret band, which shifted to longer wavelength. These features suggest that the porphyrin moieties of 4 are packed to form a J-type structure. The oxygen quenching ratio of the porphyrin 4 monolayer on the ITO electrode, I 0/ I 100, was estimated to be 1.25, where I 0 and I 100 are, respectively, luminescence intensity values in 100% argon and 100% oxygen. On repeated step cycling between 100% argon and 100% oxygen atmospheres, the response times of luminescence quenching were 10 s (argon to oxygen) and 23 s (oxygen to argon). These findings suggest that a monolayer of sensing dye is applicable for oxygen sensing system without deterioration of size-accuracy of models.

Effect of slurry pH on the defects induced during the plug isolation chemical mechanical polishing

In the present work, major polishing defects such as micro dishing and polishing residues induced during the landing plug isolation (LPI) chemical mechanical polishing (CMP) were quantitatively examined in slurries with different pH by combining chemical dipping test and analytical method such as scanning electron microscopy and transmission electron microscopy. From the results of the dipping test, we found that the solution alkalinity accelerates micro dishing of borophosphosilicate glass (BPSG) layer to 60 nm in value, which is responsible for preferential accumulation of polishing residue at this site. This is attributed to more rapid chemical dissolution of BPSG than that of nitride film during LPI CMP in alkaline slurry. By introducing acidic slurry, we succeed in the effective reduction in the micro dishing and total number of the polishing residue N r, generated during CMP in conventional silica-based alkaline slurry.

Postprocessing Antimicrobial Treatments To Control Listeria monocytogenes in Commercial Vacuum-Packaged Bologna and Ham Stored at 10°C

The antilisterial effect of chemical dipping solutions on commercial bologna and ham slices, inoculated (3 to 4 log CFU/cm2) after processing, was evaluated during storage in vacuum packages at 10°C. Samples were inoculated with a 10-strain composite of Listeria monocytogenes and subsequently immersed (25 ± 2°C) for 2 min in 2.5% acetic acid (AA), 2.5% lactic acid (LA), 5% potassium benzoate (PB), or 0.5% Nisaplin (commercial form of nisin, equivalent to 5,000 IU/ml of nisin) solutions, either singly or sequentially (Nisaplin plus AA, Nisaplin plus LA, or Nisaplin plus PB), and then vacuum packaged and stored at 10°C for 48 days. In addition to microbiological analysis, sensory evaluations were performed on uninoculated samples treated with AA, LA, or PB. Initial reductions (day 0) of the pathogen, compared with the controls, on bologna and ham samples treated with AA, LA, or PB ranged from 0.4 to 0.7 log CFU/cm2. Higher (P < 0.05) initial reductions (2.4 to 2.9 log CFU/cm2) were obtained for samples treated with Nisaplin alone and when followed by AA, LA, or PB. L. monocytogenes populations on control bologna and ham samples increased from 3.4 log CFU/cm2 (day 0) to 7.4 and 7.8 log CFU/cm2, respectively, in 8 days at 10°C. Listericidal effects were observed for all treatments tested, except for Nisaplin applied on its own, during storage at 10°C. The sequential treatment of Nisaplin plus LA reduced L. monocytogenes to undetectable levels in both products at the end of storage. The sequential treatments were also found to inhibit growth of spoilage micro-organisms. Sensory evaluations indicated that dipping (2 min) of ham samples in AA (2.5%), LA (2.5%), or PB (5%) led to lower sensory scores. However, since results of this study indicated that these treatments caused extensive listericidal effects, there is possibly a potential to reduce the levels of chemicals applied and still achieve adequate antilisterial activity without major negative effects on product quality.

Copper selenide thin films prepared using combination of chemical precipitation and dip coating method

A novel method has been developed for the preparation of copper selenide thin films. The method is based on a combination of chemical precipitation of copper selenide powders and a dip coating technique using this powder. The synthesized powder and deposited thin films at various dip coatings were analyzed using X-ray diffractometry and scanning electron microscopy (SEM). X-ray diffraction data of the thin films indicate formation of polycrystalline materials. The SEM micrographs showed formation of compact and granular morphology for the film deposited after four dip coatings. The thin films produced were found to display p-type semiconductor behavior.

Large area deposition of homogeneous Ag nanoparticles on polymeric surface and their applications

Silver nanoparticles with homogeneous size and density were deposited on the surface of a cellulose triacetate film through chemical dipping and photoreduction. UV-VIS absorption spectra and high resolution transmission electron microscopy (HRTEM) show that spherical silver nanoparticles with 2—5nm diameter were formed effectively at room temperature by properly modulating the concentration. By contact copying technique, holographic gratings were constructed with metallic nanoparticles embedded in the polymer film.

Novel Optoelectronic Sensing System for Thin Polymer Films Glass Transition Investigation

The glass transition zone of thin polystyrene films on silica substrates has been investigated by using a novel optoelectronic integrated sensor involving simultaneous refractive index and temperature measurements. The sensor design is based on the deposition of thin polymer film by chemical dipping on the distal end of a standard silica optical fiber. Direct reflectometric interrogation and fiber-Bragg grating sensor integration have been used to simultaneously retrieve information about the refractive index variation over the glass transition region revealed by a temperature ramping. Sensor modeling and sensitivity have been investigated. The glass transition has been identified by measuring the change of the thermooptic coefficient in cooling down experiments. The comparison between refractive index transition and standard calorimetric analysis has been carried out to test the optoelectronic integrated sensor reliability. The proposed sensing system has demonstrated that it is able to measure the glass transition temperature of thin polymer films; moreover, the system and procedure can be readily implemented to investigate the effect of polymeric sample finite size and specific energetic interactions on the glass transition zone.

Rate control for copper tarnishing

The reduction of copper sulphide and copper oxides originated during artificial tarnishing of copper is studied using potentiodynamic potential/current density experiments. Six copper surface treatments are considered: mechanical polishing; indoor exposure for 7 days; chemical etching in 1.6 M nitric acid; chemical etching and heating at 160 °C; and chemical etching and dipping in a 9 × 10 −4 M or 0.9 M potassium sulphide (K 2S) solution at 70 °C. Cuprite (Cu 2O) and chalcocite (Cu 2S) are the main compounds formed. A linear relationship with the square root of the scan rate ( ν) is obtained by plotting the potentiodynamic potential/current density for the tarnish dissolution processes. A relationship between potential and current density cathodic peaks is not obtained, according to Müller’s model, showing a proportionality factor with the dimensions of a resistance.

Effect of Chemical Treatment, Wax Coating, Oil Dipping and Different Wrapping Materials on Physio-chemical Characteristics and Storage Behavior of Apple (Malus domestica Borkh)

Chemical treatment, wax coating, oil dipping and different wrapping materials have significant role in extending the shelf life of apple. The present investigation was therefore, carried out to extend the shelf life of Banky cultivars of apple by applying the above mentioned treatments. In physical characteristics general appearance (color and shape of fruit), weight loss percentage and organoleptic evaluation were studied during storage. Chemical treatment, total soluble solids, pH, acidity, total sugar, reducing sugar and Vitamin C were analyzed after 15, 30, 45 and 60 days of storage. All the treatment had significant effect on the shelf life of fruits. However, Non-perforated polyethylene was reported superior to all other treatments. Non-perforated polyethylene materials proved very useful for reducing weight loss and shriveling and retained consumer acceptability even after 60 days of storage. Hydroxyquinoline and butter paper wrapping stood second and third positions after non perforated polyethylene wrapping.