Effects of salting processes and time on the chemical composition, textural properties, and microstructure of cooked duck egg

Chemical composition, textural properties, and microstructure of cooked duck egg salted by 2 methods (coating and immersing) were determined during 4 wk of salting. As the salting time increased, moisture content increased and salt content decreased for both cooked salted egg white and yolk. Oil exudation of cooked yolk and expressible water content of cooked egg white obtained from both salting methods increased as salting proceeded (P < 0.05). After cooking, oil exudation accompanied by the solubilized pigments, especially at the outer layer of yolk, was obtained. At week 3 of salting, egg yolk from coating method had the higher egg exudation than that from immersing method. As the salting times increased, the lower hardness, springiness, gumminess, chewiness, and resilience with higher adhesiveness and cohesiveness were generally found in cooked salted egg white (P < 0.05), irrespective of salting methods. Conversely, the hardness of cooked yolk increased continuously and reached the maximum at week 2 and 2 to 3 for immersing and coating method (P < 0.05), respectively. Confocal laser scanning micrographs revealed the smaller yolk granules with more release of free lipid in salted egg after heating, compared with the fresh counterpart. As visualized by scanning electron microscope, gel of cooked salted egg white was coagulum type with larger voids. Salting methods determined oil exudation in egg yolk and texture profile of egg white gel after cooking; however, those attributes were also governed by the salting time. PRACTICAL APPLICATION: Salted duck egg can be made by 2 methods (coating and immersing) affecting the characteristic of salted egg white and yolk after cooking. Desirable cooked salted egg having the red yolk with hardness and high oil exudation could be obtained when salting was carried out for 3 and 4 wk for immersing and coating method, respectively.     

Effect of salting processes on chemical composition,textural properties and microstructure of duck egg

BACKGROUND: Salted eggs have been produced in Thailand and consumed nationwide. Salted egg can be made by brining eggs in saturated saline or by coating the egg with soil paste mixed with salt. The achievement of salting is generally indicated by the textural development of egg yolk. Yolk property is therefore a prime factor governing consumer acceptability and market demand. The objective of this study was to determine chemical composition, textural properties and microstructure of duck egg obtained from the coating and immersing methods at different salting times. RESULTS: Decreases in moisture content with coincidental increases in salt content in both egg white and yolk were observed during salting, regardless of salting process. However, no difference in salt content was noticeable in yolks (P > 0.05). The paste coating method tended to yield greater oil exudation of egg yolk than the immersing method. Maximum transition temperature (T_max) of egg proteins and thiobarbituric acid‐reactive substance (TBARS) value in yolk increased with increasing salting time. A similar hardening ratio of yolk was observed in both processes. Higher hardness and adhesiveness were found in yolk with the paste coating method, whereas greater fracturability, springiness, gumminess and chewiness were observed with the immersing method. Nevertheless, both processes rendered the yolk with similar cohesiveness. Yolk granules were aligned closely when salting proceeded, irrespective of salting process. CONCLUSION: Dehydration and release of lipids in egg yolk increased with increasing salting time and were more pronounced with the paste coating method. Therefore salting processes affected the properties of salted eggs. Copyright © 2009 Society of Chemical Industry     

Comparison of Rapid Methods for Detection of Giardia spp. and Cryptosporidium spp. (Oo)cysts Using Transportable Instrumentation in a Field Deployment

Reliable, sensitive, quantitative, and mobile rapid screening methods for pathogenic organisms are not yet readily available, but would provide a great benefit to humanitarian intervention units in disaster situations. We compared three different methods (immunofluorescent microscopy, IFM; flow cytometry, FCM; polymerase chain reaction, PCR) for the rapid and quantitative detection of Giardia lamblia and Cryptosporidium parvum (oo)cysts in a field campaign. For this we deployed our mobile instrumentation and sampled canal water and vegetables during a 2 week field study in Thailand. For purification and concentrations of (oo)cysts, we used filtration and immunomagnetic separation. We were able to detect considerably high oo(cysts) concentrations (ranges: 15-855 and 0-240 oo(cysts)/liter for Giardia and Cryptosporidium, respectively) in 85 to 300 min, with FCM being fastest, followed by PCR, and IFM being slowest due to the long analysis time per sample. FCM and IFM performed consistently well, whereas PCR reactions often failed. The recovery, established by FCM, was around 30% for Giardia and 13% for Cryptosporidium (oo)cysts. It was possible to track (oo)cysts from the wastewater further downstream to irrigation waters and confirm contamination of salads and water vegetables. We believe that rapid detection, in particular FCM-based methods, can substantially help in disaster management and outbreak prevention.     

Effect of Acetic Acid and Commercial Protease Pretreatment on Salting and Characteristics of Salted Duck Egg

Salting of duck egg pretreated with 5% acetic acid and different commercial proteases (flavourzyme, protamex, alcalase, and neutrase) was studied. After 2 weeks of salting, duck eggs soaked in 5% acetic acid for 30 min, followed by soaking in 5% (w/v) flavourzyme and neutrase had the highest hardening ratio (90.14 ± 2.43%, 90.25 ± 1.23%) with the coincidental increase in salt content in egg white and decrease in moisture content of yolk, compared with those from other treatments (p < 0.05). However, similar hardening ratio of the sample treated with alcalase was obtained to that of sample treated with either flavourzyme or neutrase (P > 0.05). After 1 week of salting, protamex showed the similar effect on hardening ratio to other proteases (p > 0.05). When eggs were pretreated with neutrase at different concentrations (0.25%, 0.5%, and 0.75%, w/v) for different times (30, 60, and 90 min), those pretreated with 0.25% (w/v) neutrase for 90 min had the shorter salting time, while soaking time did not have the impact on hardening ratio for egg treated with 0.5% and 0.75% neutrase (P > 0.05). The oil exudation of egg treated with 0.25% neutrase had the higher oil exudates than the control at week 2 and 3 of salting (P < 0.05). Treatment of neutrase had no impact on viscosity of egg white, regardless of salting time (P > 0.05). Microstructure study revealed that shell of salted egg pretreated with acetic acid had rough and porous surfaces when compared with control, whereas no changes in microstructure and FTIR spectra of shell membrane were found. Therefore, pretreatment of egg with 5% acetic acid for 30 min, followed by 0.25% neutrase for 90 min prior to salting could expedite the salting process and yielded egg yolk with hardening ratio and oil exudates, comparable to the traditionally salted egg.     

Effect of Sodium Chloride and Osmotic Dehydration on Viscoelastic Properties and Thermal-Induced Transitions of Duck Egg Yolk

The effects of NaCl and osmotic dehydration on the linear viscoelastic behavior of duck egg yolk were evaluated. An increase in NaCl concentrations from 0% to 3.0% (w/w) resulted in a remarkable change in the linear viscoelastic behavior by inducing a sol–gel transition, specifically. The transition was more pronounced when 1.5% (w/w) NaCl was incorporated. The effect of dehydration on aggregation and network formation was predominant than that of the NaCl addition. Nevertheless, at a lower degree of dehydration, the addition of NaCl could modulate the viscoelastic behavior of duck egg yolk, resulting in a well-developed gel network. Addition of NaCl into duck egg yolk could stabilize the protein molecules as evidenced by an increase in denaturation temperature as well as a delay in gel network formation. As visualized by a scanning electron microscope, the denser network with smaller voids was observed in duck egg yolk gel with increasing NaCl concentration and degree of dehydration.     

Effect of NaCl on thermal aggregation of egg white proteins from duck egg

Thermal aggregation of duck egg white solution (1 mg protein/ml, pH 7) was monitored in the presence of different NaCl concentrations (0–6%, w/w) across the temperature range of 20–90 °C. Duck egg white solution exhibited higher turbidity with coincidental increases in surface hydrophobicity and decreases in sulfhydryl group content as temperatures increased from 70 to 90 °C (p < 0.05). As NaCl concentration increased, the negative charge decreased, with coincidental increases in particle size of aggregate after heating to 90 °C. As visualised by confocal laser scanning microscopy, larger clusters of protein aggregates were observed with increasing NaCl concentrations. Major duck egg white protein with molecular mass of 45 kDa disappeared in the presence of 2–6% NaCl after heating above 80 °C, regardless of concentrations. Therefore, NaCl, especially at high concentrations, could induce thermal aggregation of duck egg white protein, which could determine the characteristics of salted egg white after heating.     

A lightweight and secure NFC‐base mobile payment protocol ensuring fair exchange based on a hybrid encryption algorithm with formal verification

During the past few years, many near‐field communication (NFC) mobile payment protocols have been widely used and received more and more attentions. This could be an essential factor for the growth of the world economy and leads to the improvement of the quality of life for human beings. The NFC mobile payment is one prominent approach in allowing m‐commerce to conduct a sales transaction. However, fair exchange and information security are significant concerns in creating trust among the parties participating in the transaction. Many NFC mobile payment protocols have been introduced by researchers. But, most of them still lack some crucial properties of information security and fair exchange, and this can be an obstacle to their uses. In this article, we propose an NFC mobile payment protocol that possesses comprehensive properties of both information security and fair exchange for sales transaction processing. The protocol employs both symmetric and asymmetric encryptions, hash function, and the technique of offline session key generation, in order to improve the security while maintaining the lightweight property. The fairness analysis shows that the proposed protocol is more competent and effective than others. It can resolve any dispute in case one party misbehaves. Finally, the proposed protocol's security has been successfully verified using both Burrows, Abadi and Needham (BAN logic) and the Scyther tool.     

Protein Hydrolysate of Salted Duck Egg White as a Substitute of Phosphate and Its Effect on Quality of Pacific White Shrimp (Litopenaeus Vannamei)

ABSTRACT:  Protein hydrolysate from salted egg white (PHSEW) with different degrees of hydrolysis (DH) (3%, 6%, and 9%) was produced using pepsin. Disappearance of proteins with molecular weight (MW) of 108 and 85 kDa with the concomitant formation of proteins with MW of 23, 20, 13, and 5 kDa was observed in PHSEW. The use of PHSEW for quality improvement of Pacific white shrimp ( Litopenaeus vannamei ) was investigated. Shrimp soaked in 4% NaCl containing 7% PHSEW and 2.5% mixed phosphates (0.625% sodium acid pyrophosphate [SAPP] and 1.875% tetrasodium pyrophosphate [TSPP]) had the highest cooking yield with the lowest cooking loss ( P  < 0.05), compared with shrimps with other treatments. Nevertheless, no difference in weight gain was obtained in comparison with those treated with 4% NaCl containing 3.5% mixed phosphate ( P  > 0.05). Cooked shrimp treated with 4% NaCl containing 7% PHSEW and 2.5% mixed phosphate or those treated with 4% NaCl containing 3.5% mixed phosphate had the higher score of appearance, texture, and overall likeness but less shear force, in comparison with the control (no treatment) ( P  < 0.05). Microstructure study revealed that muscle fibers of cooked shrimp from both treatments had the swollen fibrils and gaps, while the control had the swollen compact structure. Therefore, use of PHSEW could reduce phosphate residue in shrimps without an adverse effect on sensory properties.     

Influence of sand layer depth and percolate impounding regime on nitrogen transformation in vertical-flow constructed wetlands treating faecal sludge

Four laboratory-scale units of vertical-flow constructed wetlands (VFCW) were fed once a week with faecal sludge (FS) at a constant solids loading rate (SLR) of 250 kg TS/(m².year) (equivalent to 260-300 g N/(m².week)) for a period of 12 weeks to study: i) the nitrification and denitrification potential of the sand layer of VFCWs and ii) the effect of percolate impounding regime (permanent or batch-impounding) on nitrogen transformation. The TN content of raw FS was characterised by 65% org-N, 34% NH₄-N and 1% NO_x-N. After FS application and a six-day impounding period, 8-13% TN were recovered in the percolate exhibiting the following composition: 70-80% NH₄-N, 25-30% org-N and <1% NO_x-N. A large fraction of the influent organic N (55%) was filtered in the bed and 24-29% of initial NH₄-N were lost due to nitrification and volatilisation. In permanent impounding systems, 8-11% TN were recovered in the percolate versus 13% in batch-operated beds. N loss was increased with sand layer depth (20-40 cm) under permanent impounding regimes.     

Magnetoimpedance of Electroplated Wires with Large Core Diameters

Monolayered Co and trilayered Co/Cu/Co were electroplated on 485 μm-diameter Cu wires using the bath pH 2.5. These wires can be functioned as magnetic sensors owing to their magnetoimpedance (MI) effect. By measuring at four different frequencies (100, 250, 500, and 1000 kHz) and Co thicknesses (2.5, 5.0, 10.0, and 25.0μm), the MI ratio of electroplated Co on Cu wires tended to increase with increasing Co thickness and frequency of the driving current. The Co/Cu/Co on Cu wires exhibited even higher MI ratio...