Strength Of Alkali Research Articles

Fractionation and characterisation of arabinoxylans from brewers' spent grain and wheat bran

Two agro-industrial co-products, brewers' spent grain and wheat bran, were fractionated by sequentially extracting with alkali of increasing strength. Over 60% of the brewers' grain biomass was solubilised by these treatments, compared with only 25% for wheat bran. The carbohydrate and phenolic composition of the solubilised fractions were determined, highlighting two compositionally different sets of fractions. In both co-products arabinoxylan was the main polysaccharide released. The degree of arabinose substitution of the extracted arabinoxylan diminished as the alkali strength increased. Insoluble residues contained both cellulose and non-cellulosic polysaccharides. In spent grain, the composition of the arabinoxylan in the residue was similar to that of the starting material. In wheat bran, the residual xylan was very highly substituted with arabinose. Both ferulic acid and three forms of diferulic acid (5,5′, 8- O-4′ and 8,5′) were present in the solubilised material, even after treatment with 4 M KOH. Esterified acetate was also present on polymers solubilised with KOH at concentrations up to 1 M. The more soluble fractions of spent grain represented a heterogeneous aggregation of feruloylated arabinoxylans with a broad molecular mass range, but the fractions extracted with stronger base were separated into low molecular weight moieties, presumably due to cleavage of covalent cross-links. Potential food and non-food uses for the isolated fractions from the cereal co-products are discussed.

The influence of different parameters on the hydration process of binders based on alkali activated slag

The influence of certain types of activators (water glass Na2O.nSiO2 and sodium-metasilicate Na2SiO3.5H2O) on the hydration process of alkali activated slag was investigated in this study. The influence of activator concentration, specific surface area of the slag and the modulus n of the water glass (mass ratio between SiO2 and Na2O) on the kinetics of the hydration process i.e., the change of compressive strength were also investigated. Poorly crystallized low base calcium silicate hydrate C-S-H (I) is the main hydration product of alkali activated slag regardless of the activator used. This is the reason for the rapid increase in the strength of alkali activated slag and also of the very high strength values. The strength growth rate and strength values were significantly higher when sodium-metasilicate was used as the activator than when water glass was used. The specific surface area of the slag and the activator concentration are parameters which have a closely connected influence on strength and their action is cumulative. The modulus n of water glass does not have an explicit influence on the strength of alkali activated slag.

Thermal stability of texture in Chinese water chestnut may be dependent on 8,8'-diferulic acid (aryltetralyn form).

Ferulic acid (FA) cross-links have been implicated in the thermal stability of texture in Chinese water chestnut (CWC) tissues. The aim of the current study has been to investigate this concept further. CWC tissue strips were measured for their mechanical properties before and after extraction in increasing strengths of alkali. The mechanical properties were related to the associated mode of fracture (cell separation or breakage) at the fracture surfaces and the phenolic composition of the cell walls. CWC tissue softened after prolonged extraction in cold alkali due to an increase in the ease of cell separation. Analysis of wall-bound phenolics demonstrated that most FA moieties, including five of the six dehydrodimers, were released before tissue strength was reduced. Loss of strength was, however, coincident with the loss of 8,8'-diferulic acid, aryltetralin (AT) form. It has been suggested that this dehydrodimer may be particularly concentrated at the edge of the cell faces. These results provide further evidence for the involvement of this dehydrodimer in conferring thermal stability of cell-cell adhesion and hence texture in CWC. However, they do not exclude the other diferulates from involvement in cell adhesion.

The systematic study of aluminium speciation in medium concentrated aqueous solutions

Industrial applications and environmental problems involving the aqueous chemistry of aluminium require an understanding of the speciation of this metal ion at a wide range of concentrations. The formation of polynuclear species is of special interest due to the complexity of the hydrolysis mechanisms and the diversity of the hydrolysis products. Kinetic aspects of speciation are also important considering the different stability ranges of polycationic species formed during the hydrolysis process. In the present paper we report results of systematic studies on the formation of aluminium polycations at room temperature. Automated potentiometric titrations have been used to study the hydrolysis of aluminium-ions in solutions (0.01–0.2 M) on a short time scale (2 min between titrant additions). 27Al NMR spectroscopy and dynamic light scattering have been used for investigations on a longer time scale (24 h). The effects of alkali strength (KOH, NH 4OH and KHCO 3) and concentration (0.45–2.0 M), counterion identity (Cl −, NO 3 −, SO 4 2−) and ionic strength have been investigated. Optimum conditions for the generation of Al 13-mer are proposed on short and long time scales. On a short time scale, aluminium chloride and nitrate should be used as starting materials, KOH and KHCO 3 should be used for hydrolysis and experiments conducted at low ionic strength. For solutions that have been left to age, there is a considerable hydrolysis window that can be used to generate significant quantities of the Al 13-mer that vary little with the alkali used. Al 13-mer species are not generated from alum as the precursor. The presence of sulphate ions alters the pathway of aluminium polymerisation to form polymeric and solid materials. On the basis of the potentiometric titration data, dynamic light scattering and 27Al NMR measurements evidence is provided for the detrimental role of sulphate-ions in the formation of Al 13-mer and an alternative mechanism of aluminium ion polycondensation is proposed, based on the increased stability of monomeric and oligomeric species (dimer and trimer) in the presence of sulphate-ions.

31P MAS-NMR study of R′ xR″ yP 6O 18.nH 2O cyclohexaphosphates

Several alkali/alkaline-earth R x +R y 2+P 6O 18.nH 2O cyclohexaphosphates, with R +=Li, Na, K, Cs, NH 4, Tl, DBA; R 2+=Ca, Zn, Cd, have been analyzed by 31P MAS-NMR spectroscopy. From their NMR spectra, the number and the multiplicity of crystallographic sites have been analyzed and compared with those deduced by symmetry considerations from X-ray diffraction data. A linear dependence of the isotropic chemical shift values of NMR components on the POP angles of cycles has been obtained. However, some influence of the charge and polarizing strength of alkali and alkaline-earth cations has also been detected. Finally, principal values of the chemical shift tensor of P atoms have been analysed in terms of local symmetry and tetrahedral ring distortions.

Effect of refining of crude rice bran oil on the retention of oryzanol in the refined oil

AbstractThe effect of different processing steps of refining on retention or the availability of oryzanol in refined oil and the oryzanol composition of Indian paddy cultivars and commercial products of the rice bran oil (RBO) industry were investigated. Degumming and dewaxing of crude RBO removed only 1.1 and 5.9% of oryzanol while the alkali treatment removed 93.0 to 94.6% of oryzanol from the original crude oil. Irrespective of the strength of alkali (12 to 20° Be studied), retention of oryzanol in the refined RBO was only 5.4–17.2% for crude oil, 5.9–15.0% for degummed oil, and 7.0 to 9.7% for degummed and dewaxed oil. The oryzanol content of oil extracted from the bran of 18 Indian paddy cultivars ranged from 1.63 to 2.72%, which is the first report of its kind in the literature on oryzanol content. The oryzanol content ranged from 1.1 to 1.74% for physically refined RBO while for alkali‐refined oil it was 0.19–0.20%. The oil subjected to physical refining (commercial sample) retained the original amount of oryzanol after refining (1.60 and 1.74%), whereas the chemically refined oil showed a considerably lower amount (0.19%). Thus, the oryzanol, which is lost during the chemical refining process, has been carried into the soapstock. The content of oryzanol of the commercial RBO, soapstock, acid oil, and deodorizer distillate were in the range: 1.7–2.1, 6.3–6.9, 3.3–7.4, and 0.79%, respectively. These results showed that the processing steps—viz., degumming (1.1%), dewaxing (5.9%), physical refining (0%), bleaching and deodorization of the oil—did not affect the content of oryzanol appreciably, while 83–95% of it was lost during alkali refining. The oryzanol composition of crude oil and soapstock as determined by high‐performance liquid chromatography indicated 24‐methylene cycloartanyl ferulate (30–38%) and campesteryl ferulate (24.4–26.9%) as the major ferulates. The results presented here are probably the first systematic report on oryzanol availability in differently processed RBO, soapstocks, acid oils, and for oils of Indian paddy cultivars.

A modified method for determining free fatty acids from small soybean oil sample sizes

AbstractA modification of the AOCS Official Method Ca 5a‐40 for determination of free fatty acids (FFA) in 0.3 to 6.0‐g samples of refined and crude soybean oil is described. The modified method uses only about 10% of the weight of oil sample, alcohol volume, and alkali strength recommended in the Official Method. Standard solutions of refined and crude soybean oil with FFA concentrations between 0.01 and 75% were prepared by adding known weights of oleic acid. The FFA concentrations, determined from small sample sizes with the modified method, were compared with FFA percentages determined from larger sample sizes with the Official Method. Relationships among determinations obtained by the modified and official methods, for both refined and crude oils, were described by linear functions. The relationship for refined soybean oil had an R2 value of 0.997 and a slope of 0.99±0.031. The values for crude soybean oil are defined by a line with R2=0.9996 and a slope of 1.01±0.013.

The mixed alkali effect and thermodynamic state of glasses

The mixed alkali effect, a pronounced reduction in electric conductivity when two or more dissimilar alkali ions coexist, is most conspicuous under a d.c. electric field while it diminishes under high frequency. Correspondingly, low d.c. conductivity of the mixed alkali glass is accompanied by a large dielectric relaxation strength (dielectric loss and static dielectric constant). This larger dielectric relaxation strength of mixed alkali glasses compared with the corresponding single alkali glasses appears due to a negative enthalpy of mixing of two dissimilar alkali species. This fact has been experimentally confirmed. Correspondingly, the activity coefficient of one alkali component decreases drastically by the addition of a second alkali component and this behavior appears to be analogous to the pronounced decrease of a tracer diffusion coefficient when a second alkali component is added. The thermodynamic state of glasses is controlled, primarily, by the charge interactions. The apparent correlation between the thermodynamics and the transport phenomena, as well as other features of the mixed alkali effect, such as the diminishing mixed alkali effect in a high electric field, can be explained, at least qualitatively, using the electrolyte theory based upon the Coulombic interactions of charged species originally developed by Debye and Hückel.

The Influence of Pretreatment on Humic Acid Yield and 14C Age of Carex Peat

The object of the study was to assess the effects of a range of pretreatment/extraction schemes on the yields of humic acid and humin obtained from peat and the subsequent radiocarbon ages. We analyzed peat from Flókadalur in northern Iceland, collecting material from a profile containing seven visible tephra horizons in the upper 3 m, whose form and extent indicated little disturbance to the section over the last 4000 yr. The results of a range of pretreatments demonstrated that time rather than the strength of alkali is the more important factor governing the extraction of humic acid. An increase in alkali molarity did not correspond to any systematic increase in yield, whereas an increase in time did, implying that the extraction is kinetically controlled. We found no evidence of variability in 14C age due to pretreatment scheme or between different geochemical fractions of the peat. Further implications from this study are that bog stability and ecological simplicity produce a favorable environment for 14C dating.

The Wall-Bound Phenolics of Chinese Water Chestnut (Eleocharisdulcis)

Chinese water chestnut (CWC) is a vegetable in which the edible storage parenchyma exhibits thermal stability to texture. This property has been attributed to the presence of large quantities of simple phenolics which exhibit pH-dependent autofluorescence. The identities of the major phenolic components were assessed by reverse-phase HPLC after sequentially extracting them with increasing strengths of alkali from purified CWC cell wall material. The levels of cold-alkali-liberated phenolics were very high (12.2 mg g -1 cell wall material). Ferulic acid dominated the monomeric phenol fraction (7.2 mg g -1 ), although small quantities of aldehydes were also released. A number of different diferulic acids were also identified, of which the 8-0-4'-linked form was the major component (2.8 mg g -1 ), with 8,5'-diferulic acid and the familiar 5,5'-form also present in smaller quantities (910 and 988 μg g -1 , respectively). Hence, approximately 40% of the ferulic acid in the wall was present as dimers which are potentially available to form extensive, heat-resistant cross-links between polysaccharides within the wall, and between cells.

Potato xyloglucan is built from XXGG-type subunits

Extraction of potato cell-wall material with solutions of increasing strength of alkali yielded a xyloglucan-rich fraction which was further purified by anion-exchange chromatography and treatment with α-amylase and endogalactanase. Methylation analysis indicated that the purified xyloglucan contained a high percentage of unsubstituted glucosyl residues compared to, for instance, apple xyloglucan, and equal amounts of Xyl-(1 → 6)-, Gal-(1 → 2)-Xyl-(1 → 6)-, and Ara-(1 → 2)-Xyl-(1 → 6)-sidechains. This xyloglucan was degraded with endoglucanase (endoV), purified from Trichoderma viride. The resulting digest was fractionated by BioGel P-2 chromatography, followed by preparative high-performance anion-exchange chromatography of the pentamer to nonamer fractions. The purified oligosaccharides were characterized by monosaccharide analysis, mass spectrometry, and degradation with an exoglucanase. Degradation of potato xyloglucan by another endoglucanase (endoIV) of Trichoderma viride yielded a different set of products. EndoIV released predominantly oligosaccharides with two unbranched glucosyl residues at the reducing terminus, whereas endoV also released products containing unbranched glucosyl residues on both ends of the molecule. A difference in the mode of action of endoglucanases with xyloglucan-degrading activity is demonstrated.

Towards a structural interpretation of fragility and decoupling trends in borate systems

Qualitative correlations are established between the fragility, decoupling index, glass transition temperature and structure of xMO(1-x)B 2O 3.gif"> systems (M = Li 2, Na 2, Ba, Sr, Ca). Despite the similarities between the cationic field strengths of alkali and alkaline earth cations, the latter have a higher cross-linking efficiency than the former. Therefore, they ‘freeze’ the liquid structure at higher glass transition temperatures and arrest a less polymerized borate network. The competition between the cross-linking induced by the B-O and the M-O bonds leaves the fragility index relatively independent of M. The enhanced participation of the bivalent ions in network formation results in a decrease of the decoupling index at T g.

The nutritive value of alkali-treated cocoa husk meal in broiler chick diets

The effect of alkali concentration and treatment on the chemical composition of cocoapod husk (CPH) was investigated. This was followed by the incorporation of the alkalitreated CPH (TCPH) in broiler starter diets to investigate its nutritive value. Alkali was obtained from cocoa-pod ash, 7.35 g of which was found to be equivalent in alkali strength to 1 g sodium hydroxide. Longer alkali treatment time (48 h) yielded similar effects to those produced after 24 h. Increasing alkali concentration (5, 10, 15 and 20 g kg −1) decreased the amounts of crude fibre, hemicellulose, cellulose and crude protein, but increased total ash, Na, Cu, Fe, Mn and Zn contents of CPH. An alkali concentration of 10 g kg −1 (which appeared most balanced in its effect on the chemical contents of CPH) was employed in a 24 h-treatment of the husks used in the feeding trial. TCPH was included in the diets at concentrations of 0, 50, 100 and 150 g kg −1. Each diet was fed to triplicate groups of 15, day-old broiler chicks for 28 days. The results showed that increasing TCPH level up to 100 g kg −1 did not significantly reduce growth performance and apparent digestibility of nutrients. Dietary inclusion of TCPH at 150 g kg −1 significantly ( P < 0.05) reduced weight gain and feed efficiency compared with those on the control diet (weight gain, 497.0 g vs. 520.3 g; feed efficiency, 2.61 vs. 2.12, respectively). Also the apparent digestibilities of crude protein (0.80) and crude fat (0.90) for the control diet decreased significantly ( P < 0.05) to 0.75 and 0.84, respectively, for the 150 g kg −1 TCPH diet. Water consumption of chicks increased with increasing TCPH level. It was concluded that in order to effect the potential upgrading of the nutritive value of CPH, it is necessary to remove salt deposition and residual alkali, which may have masked the effect of alkali treatment.

Factors affecting the strength of alkali-activated slag

The effect of several factors on the strength of alkali activated slags has been investigated. The most important factors were found to be: the type of alkaline activator, the means of adding activator, the dosage of alkali, the type and fineness of slag, SiO 2/Na 2O ratio (modulus, Ms) when using waterglass solution, curing temperature, liquid/slag or water/slag ratio and additive. Some of these factors are interdependent and the effect of changing more than one is usually not additive. The optimum range for each factor is suggested through reviewing previous work and our recent results of a full factorial range strength study. The interaction of factors is considered and discussed throughout the paper, hoping to gain a better understanding of the processing of alkali-activated slag (AAS) cement and concrete.

Cell wall changes in immature Asparagus stem tissue after excision

Cell wall material (CWM) was prepared from sections of fresh and aerobically-stored asparagus ( Asparagus officinalis, L. cv. Connovor Collossus) stems. Polymers were solubilized from the CWM by successive extraction with cyclohexane- trans-1,2-diamine- NNN′N′-tetraacetate (CDTA), Na 2CO 3 and KOH to leave the α-cellulose residue which contained a significant amount of cross-linked pectic polysaccharides. The polymers were fractionated by anion-exchange chromatography and selected fractions were subjected to methylation analysis. The storage-related decrease in (1–4)-linked Gal p was detected in all the fractions rich in pectic polysaccharides, particularly in the CDTA, Na 2CO 3, 0.5 M KOH fractions and α-cellulose residue. A smaller decrease in Ara f was also observed. This was mainly due to a decrease in (1–5)-linked Ara f in the Na 2CO 3-1-soluble polymers, and terminal Ara f in the α-cellulose residue. There was evidence for the occurrence of significant amounts of complexes containing pectic polysaccharides and xylans having a relatively low degree of polymerization in the dilute alkali-soluble polymers, and some of these contained phenolic compounds; the storage-induced increase in (1–4)-linked Xyl p was confined to these polymers. Interestingly, no free acidic xylans could be detected in the 1 M and 4 M KOH-soluble polymers; instead, the bulk of the hemicellulosic polysaccharides appeared to be mixtures of xyloglucans and xylans in which the ratio of xyloglucan to xylan increased with increasing strength of alkali used for extraction of the polymers. The non-degradative extraction and fractionation procedures revealed heterogeneity in pectic polysaccharides, pectic polysaccharide-xylan complexes and xyloglucans in close association with xylans. The possible relationship between pectic polysaccharide-xylan-phenolic complexes and the onset of lignification in maturing tissues is discussed.

Mechanism of the mixed alkali effect based upon the thermodynamic state of glass

A new mechanism for the mixed alkali effect of dc conductivity is proposed. It was shown earlier that the high frequency conductivity shows very little mixed alkali effect and that mixed alkali glasses show a much larger dielectric relaxation strength than single alkali glasses, indicating that the mixed alkali effect in dc conductivity is related to the difference in the dielectric relaxation strength. An expression for dielectric relaxation strength in terms of the thermodynamic state was experimentally verified for single alkali glasses. An analogous equation for dielectric relaxation strength of mixed alkali glasses was derived. Using the regular solution model, it was shown that the dielectric relaxation strength for mixed alkali glasses can show a large maximum if the enthalpy of mixing between the two alkalis is negative. A large negative enthalpy of mixing between the two alkali species was found experimentally from ion-exchange equilibrium, which, it is suggested, originates from the stress due to their ionic size difference. The proposed mechanism appears to be consistent with many experimental observations.

Structural features of cellulosic change in alkali‐treated jute stick: An infrared absorption study

AbstractThe cellulosic change has been discussed in terms of absorption ratio of certain infrared bands. It is shown that the absorption of O—H and C—H stretching frequencies decreases up to 25% alkali treatment and the absorption of β‐glucosidic band increases with increasing alkali strength in swelling. The anomalous behavior in the absorption of these bands at 18% alkali treatment might be due to partial mercerization. A new type of hydrogen bonding is proposed where C6 hydroxyl groups are involved in a bifurcated six‐membered hydrogen bonding system giving more crystalline nature to mixed lattice of cellulose. The O2 hydroxyl proton forms hydrogen bond with O3 of the same unit and with O'2H of its antiparallel chain. It is also noted that the presence of lignin has no significant effect on cellulosic transition.

Electron paramagnetic resonance characteristics of the humic acids from a podzol

A study has been made of solid and solution electron paramagnetic resonance (EPR) spectra of humic acids from different horizons in a podzolic soil. Hyperfine splitting was observed in the solution spectra of humic acids from all horizons and depended on the strength of alkali and the period of dissolution. The upper organic horizons L, F and O 1 contained humic acids with some spectral characteristics in common with lignin. Humic acid from the lower horizons showed different spectra. At least 5 different radical signals were present.

Property Variation in Alkali Alkaline-Earth Metaphosphate Glasses

Coefficients of helium migration, coefficients of thermal expansion, and glass-transition temperatures were measured for several series of alkali alkaline-earth phosphate glasses. The helium permeability decreases with the field strength of alkali or alkaline-earth ions in the order Na+ > Li+ and Mg2+ > Ca2+ > Ba2+. The glass-transition temperature increases and coefficient of thermal expansion decreases with increasing field strength of alkali or alkaline-earth ions. The relationship of lower molar volume, corresponding to decreased coefficients of helium diffusivity reported for other glass-forming systems, occurs in the phosphate glasses.

Alkali Gelatinization of Flours

AbstractFlours from 12 different species of grain, pod seed, and tuber plants were gelatinized with aqueous sodium hydroxide at room temperature. Changes in physical appearances and viscosity patterns were noted over a 7‐day quiescent period in graded‐strength alkali solutions in sealed jars. The alkali strength, 0.07–0.85‐N, was sufficient to peptize proteins and hemicelluloses. Color development was strong and rapid and several flours evolved notable amounts of ammonia and perhaps amines. No two flours produced the same viscosity development patterns as time progressed. From the observed visual and viscosity changes, it was apparent that alkali gelatinization of the flours generally was complete within several hours at levels of 2.82‐3.52 meq NaOH/g flour. Some discussion centers on differences between flours, between some species of flours and the starches obtained from those species, and the possible role of other flour constituents on the gelatinization behavior.