Studies on the processing and properties of soymilk. 3. Factors affecting concentration of soymilk and its stability during heat sterilisation

Soymilk that has been efficiently heat treated to destroy the trypsin inhibitor is difficult to concentrate because its viscosity increases exponentially with increase of solids content. This imposes a concentration limit of around 17–18% total solids due to the formation of gel-like structure. The possible factors which contribute to this gel formation during concentration were investigated. A sulphydryl-disulphide interchange reaction is mostly responsible for the increase in viscosity of the concentrate up to about 16% total solids but above this concentration other forces predominated. The possibility of gelation through the intermodular cross-linkages by calcium ion was eliminated. Sodium sulphite and N-ethylmaleimide are effective in reducing this viscosity increase to some extent but when the concentrate is sterilised sodium sulphite ceases to have any effect on the viscosity and with N-ethylmaleimide the viscosity of the sterilised concentrate is about 50% of the unstabilised sample. Fore-warming by heating to 115°C for 5 min causes an increase in viscosity during concentration but effectively stabilises the product against further increases in viscosity on sterilisation. Final viscosity of the forewarmed product after sterilisation is about 75% of the unstabilised sample. The conditions necessary for the production of good quality canned soymilk concentrate are presented.     

Studies on the processing and properties of soymilk. II. Effect of processing conditions on the trypsin inhibitor activity and the digestibility in vitro of proteins in various soymilk preparations

Soymilks prepared from beans which had been soaked either in water or 0.4 M sodium carbonate solution for 24 h as a pretreatment were subjected to heat treatment under different conditions for varying lengths of time, to destroy the trypsin inhibitor activity. The rate of inactivation oftrypsia inhibitor in soy milks prepared from carbonate presoaked beans was faster than that of the water presoaked preparation when processed at 98°C and this effect was primarily associated with the change that occurred in the pH of the former system; The effect of alkaline pH's at 98°C on the inactivation of trypsin inhibitor was examined and it was found that the rate of inactivation was changed from zero order at pff 6.8 to first-order kinetics at pH 9.9. Regression equation relating pH of the system and time of heating at 98°C for 100% destruction of the inhibitor activity is presented. This effect of pretreatment was eliminated when both milks were processed at 115°C in cans because of the constancy of pH under these conditions. The influence of heat processing conditions on the enzymic digestibility of proteins in both soymilks was also studied. The pepsin digestion showed no significant differences between milks prepared from the water and the carbonate presoaked soybeans, and was highest in milks which had not been heat treated. With trypsin the digestibility increased with the degree of heal treatment up to the point where the trypsin inhibitor was destroyed, after which further heating resulted in lower digestibilities. A 19% increase in digestibility by trypsin was observed in the milk prepared from carbonate presoaked beans when compared with that from water presoaked beans and after both milks had been heated at 98°C for just sufficient time to destroy the trypsin inhibitor. When the milk prepared from water presoaked beans was autoclaved at 115°C to the same end point, its digestibility increased but it was still about 6% lower than that of the milk prepared by alkali presoaking method and processed at 98°C. The digestibility of casein using pepsin under the conditions used was lower than that of both soymilks. When trypsin was used the digestibility of casein was approximately the same as that of the adequately processed soymilk from carbonate presoaked soybeans or the autoclavtd soymilk from water presoaked beans. Other effects of using a carbonate presoaking treatment far the production of soymilk have also been discussed.     

Plasmonic electro-absorption modulator and polarization selector

Silicon photonics has begun to use index tunable plasmonic materials, such as graphene and indium tin oxide (ITO), because these materials can have their properties tailored by an external voltage. In this article, a compact plasmonic device, which can work as an optical mode controller and electro-absorption (EA) modulator at 1550 nm, is proposed. The performance of the device is theoretically investigated for ITO. Numerical simulations show that, with a suitable applied voltage to thin ITO layers, the proposed structure can select either only one mode (TE/TM) or both modes initially and then modulate the selected mode: a modulation depth of about 30–50 dB/μm is achieved with a proper choice of the dielectric spacer material. In addition, the proposed structure performance is analysed by replacing the waveguide materials with germanium. The proposed nanoscale device, with high modulation bandwidth (f_3 dB = 700–250 GHz) and low-energy consumption (~4.0 fJ/bit), may find applications in the future integrated nanophotonics.     

Experimental methods of actuation, characterization and prototyping of hydrogels for bioMEMS/NEMS applications

As a member of the smart polymer material group, stimuli responsive hydrogels have achieved a wide range of applications in microfluidic devices, micro/nano bio and environmental sensors, biomechanics and drug delivery systems. To optimize the utilization of a hydrogel in various micro and nano applications it is essential to have a better understanding of its mechanical and electrical properties. This paper presents a review of the different techniques used to determine a hydrogel's mechanical properties, including tensile strength, compressive strength and shear modulus and the electrical properties including electrical conductivity and dielectric permittivity. Also explored the effect of various prototyping factors and the mechanisms by which these factors are used to alter the mechanical and electrical properties of a hydrogel. Finally, this review discusses a wide range of hydrogel fabrication techniques and methods used, to date, to actuate this family of smart polymer material.     

Fabrication of gold nanoparticle/multi walled carbon nanotube hybrids by in situ reaction in water using poly(acryloyl beta-alanine)

Fabrication of a hybrid consists of gold nanoparticles and multi walled carbon nanotubes (MWCNTs) with the help of poly (amino acid) was investigated. Poly(acryloyl beta-alanine) was synthesized by precipitation polymerization in tetrahydrofuran. The polymers were used to form hybrids with MWCNTs in aqueous media. Subsequently, the polymer functionalized MWCNTs were fabricated by in situ formed gold nanoparticles. The fabrication by gold nanoparticles was confirmed by transmission electron microscopic analyses. The fabrication was attempted with different concentrations of lithium auric chloride solutions in the range of 0.1-1.2 mM in water. The lower concentration of the gold precursor solution resulted in the formation and attachment of gold nanoparticles without aggregation while the higher concentration above 1.0 mM led to the aggregation of gold nanoparticles. The gold nanoparticles were observed only on the surface of MWCNTs and none was in the bulk aqueous phase.     

Studies on the development of infant foods from plant protein sources. Part III. Preparation, processing and properties of various products developed

Studies have been carried out on the development of a low-cost, high-quality infant food of low paste viscosity from rice, chickpea (Cicer arietinum) and cow's milk. In order to improve the overall quality of the product, chickpea was processed by different methods prior to its incorporation. A number of formulations was prepared by mixing 52% rice, 30% each, the processed chickpea sample, and 18% whole milk powder. These mixtures were processed by extrusion cooking or drum drying. In the case of the extrusion cooking method, from the nutritional and technological points of view, it was found advantageous to incorporate milk powder after cooking a mixture of rice and chickpea. The values of net protein ratio (NPR) of the products developed, whether processed by extrusion cooking or drum-drying methods, were statistically equal, and not significantly different from those of casein. Supplementing the product with methionine and threonine showed no effect in improving the NPR value, suggesting that these amino acids were not limiting. There were slight differences in the digestibilities of proteins in the products developed and all were lower than that of casein. Depending on the processing method, differences were observed in paste viscosities of the products. After partial hydrolysis of the products with pounds amylase, both the cold and hot paste viscosities were greatly reduced and were comparable with those of whole milk powder. From the results herein reported, it can be concluded that the drum-dried product prepared using rice:chickpea (carbonate presoaked):milk (52:30:18) is the best of all the products developed. Its amino acid composition compares favorably with that of the milk proteins.     

Studies on the processing and properties of soymilk. I. Effect of preprocessing conditions on the flavour and compositions of soymilks

The effect of presoaking soyabeans in solutions of various chemicals on the reduction of beany flavour in soymilk was investigated. Of the chemicals used, sodium carbonate and sodium hydroxide had a significant effect on the reduction of beany flavour in soymilk. Sodium carbonate soaking at 0.4 M concentration for 18-24 h was significantly better than any other presoak treatment. The activity of lipoxidase as a major source of beany flavour in soymilk is questioned. Soymilk prepared from beans presoaked in carbonate contained more protein and had a higher viscosity than milks prepared from beans presoaked in water or sodium hydroxide. Beans presoaked in carbonate were easier to process than the other two. There was no significant difference in the amino acid pattern of the proteins in the soymilks prepared by the three methods.     

Studies on the development of infant foods from plant protein sources. Part I. Effect of germination of chickpea (Cicer arietinum) on the nutritive value and digestibility of proteins

For the purpose of developing an infant food of improved dispersibility characteristics and high nutritive quality, different treatments and technologies were applied to chickpea (Cicer arietinum). Samples were germinated for two and four days at room temperature (25 - 27 degrees C). One portion of each germinated chickpea sample was boiled for 40 min and the other portion was autoclaved at 15 psi for 15 min. These processed samples were then compared with the corresponding value of raw germinated and ungerminated samples as well as with the ungerminated processed ones for the following characteristics: chemical composition, contents of antiphysiological factors, solubility of proteins, lysine availability, net protein ratio (NPR), and digestibility of proteins. Germination caused an increase in the protein content of the seeds. No appreciable changes were observed in the trypsin inhibitor and tannin contents during germination. Availability of lysine was found slightly lower in the germinated seeds. The solubility of the nitrogenous constituents was markedly increased during germination. Along with processing, germination had no beneficial effect in improving protein quality, although digestibility of the proteins was increased. Boiling was more advantageous in the case of germinated seeds than autoclaving, whereas the reverse was true in the case of ungerminated seeds.     

Metal-insulator-semiconductor structures of InSb/SiO2with very low interface trap density

MIS structures fabricated using InSb and silicon dioxide with an interface trap density as low as 4×10¹⁰ cm^-2 eV^-1 have been achieved. This is about one order of magnitude less than any other reported figure for the InSb MIS system. Both capacitance/voltage and conductance techniques have been employed to study the interface properties of InSb/SiO₂. A low state density of <10¹⁰ cm^-2 was observed and the dielectric breakdown field of the oxide was greater than 4 mV cm^-1      

Controlling the electric field enhancement factor of photonic nanojets by using the magneto-optical effect

In recent years, many researchers have studied photonic nanojets. These nanojets are created when an incident plane wave is focused into a narrow and high intensity emerging optical beam leaving a micro-object (e.g. microcylinder). These narrow beams may find applications in particle imaging and detection, optical sensors, enhanced Raman scattering, and particle manipulation. They also allow the projection of a particle to the far-field where it can be easily visualized. In this paper, it is shown that the electric field enhancement factor can be dynamically controlled by the application of an external intense magnetic flux density.