The influence of various small plasticisers and malto-oligosaccharides on the retrogradation of (partly) gelatinised starch

Ageing of gelatinised and partly gelatinised potato starch and wheat starch were investigated in the presence of plasticisers with increasing size and number of OH groups (ethylene glycol, glycerol, threitol, xylitol, glucose, and for potato starch also maltose). The influences of these plasticisers and of granular remnants (ghosts) on recrystallisation were determined by using X-ray diffraction. Recrystallisation of potato starch samples in the presence of plasticisers resulted in crystallinity indices of 0.5. The largest reduction in potato starch recrystallisation is found for threitol (4 OH) and xylitol (5 OH). In the plasticiser range examined, the crystallisation inducing effect of granular potato starch remnants is reduced better when the plasticiser contains more OH groups. Wheat starch recrystallises to a lesser extent than potato starch, resulting in crystallinity indices of 0.4. The results for wheat starch do not show clear trends for the influences of plasticiser size and of ghosts. The difference in behaviour of the two starches is probably caused by wheat starch having shorter amylopectin chains. Resulting from these shorter amylopectin chains, the remaining structure in wheat starch ghosts may resemble A-type crystallinity, making it more difficult to form B-type crystals. Alternatively, the trends as found for potato starch may occur, but are less manifest for wheat starch, due to the lower total extent of recrystallisation. Solid state CP/MAS NMR spectra of the wheat starch samples containing ethylene glycol were obtained, in order to compare completely and partly gelatinised systems. The spectra were identical, confirming that the ghost structures do not influence wheat starch recrystallisation. Apparently, wheat starch ghosts do not act as nuclei for crystallisation.

Similarly, the influence of various malto-oligosaccharides in combination with granular remnants (ghosts) was investigated on wheat starch ageing. Gelatinised and partly gelatinised wheat starch were plasticised with maltose, maltotriose, maltotetraose, maltopentaose or maltohexaose. This resulted in crystallinity indices of 0.2, with the largest reduction in recrystallisation for maltotriose and maltotetraose. No trend was found for the influence of ghosts. The presence of ghosts did not influence the ¹³C solid state HP/DEC NMR spectra. Less recrystallisation took place than with the previously mentioned smaller plasticisers that resulted in crystallinity indices of 0.4. The finding that maltose was able to reduce retrogradation better than glucose could be of practical importance.     

Comparison of potato amylopectin starches and potato starches — influence of year and variety

Starches from three potato varieties and their respective transformants producing amylopectin starch were studied over a period of 3 years. The gelatinisation, swelling and dispersion properties were studied using differential scanning calorimetry (DSC), X-ray diffraction, swelling capacity measurements and a Brabender Viscograph.

The potato amylopectin starches (PAP) exhibited higher endothermic temperatures as well as higher enthalpies than the normal potato starches (NPS). PAP samples gave rise to an exceptionally sharp viscosity peak during gelatinisation and a relatively low increase in viscosity on cooling. Swelling capacity measurements showed that PAP granules swelled more rapidly, and that the dispersion of the swollen granules occurred at a lower temperature (85°C). Analysis of variance (ANOVA) also revealed that the year influenced the DSC results, and that both year and variety affect some of the Brabender parameters. Furthermore, the PAP and NPS samples were subjected to heat–moisture treatment at three different moisture levels, and the Brabender viscosity properties were studied.     

Effect of microwave irradiation on the physical properties and morphological structures of cotton cellulose

Microwave heating has been proved to be more rapid, uniform and efficient, and easily penetrate to particle inside. To investigate the effect of microwave irradiation on the physical property and morphological structure of cotton cellulose, cellulose fabric was treated with microwave irradiation at different conditions. The physical properties of the treated cellulose fabric were investigated. The morphological structures and thermal stabilities of the untreated and treated cellulose were investigated with differential scanning calorimetry (DSC) and X-ray diffraction. The results show that the physical properties of the treated cellulose fabrics were improved and the recoverability had not significant change. The thermal stability of the treated cellulose was changed. The crystallinity and preferred orientation of the treated cotton cellulose increased.     

Resistin and RELM-alpha gene expression in white adipose tissue of lactating mice

An ORF2 gene located upstream of the cellulose synthase (bcs) operon of Acetobacter xylinum BPR2001 was disrupted and a mutant (M2-2) was constructed. In static cultivation, the parent strain produced a tough, colorless, and insoluble cellulose pellicle, whereas M2-2 culture produced a thin, yellow, and fragile pellicle. The results of X-ray diffraction and 13C solid-state NMR indicated that the product of M2-2 is a mixture of cellulose I, cellulose II, and amorphous cellulose. The cellulose I to cellulose II ratio of the mixture was evaluated from the signal areas of C6 to be about 1:2. Electron microscopy revealed that the product of M2-2 included ribbon-like cellulose and irregularly shaped particles attached to the ribbons. On the other hand, the mutant complemented with plasmid pSA-ORF2/k containing the ORF2 gene and BPR2001 produced only cellulose I. These results indicate that the ORF2 gene is involved in the production and crystallization of cellulose I microfibrils by this microorganism.     

New starches from traditional Chinese medicine (TCM)--Chinese yam (Dioscorea opposita Thunb.) cultivars

The starches separated from two different Dioscorea opposita Thunb. cultivars were investigated for morphological, thermal and crystal properties. The shape of starch granules separated from different D. opposita Thunb. cultivars varied from round to oval or irregular. The surface of the starch granules appeared to be smooth without any fissures. The average particle diameter of starches from different D. opposita Thunb. cultivars was 40.3 and 38.7mum for D. 47 and D. SXY starch, respectively. The transition temperatures (T(o), T(p) and T(c)) and enthalpy of gelatinization (DeltaH(gel)) were determined using differential scanning calorimetry (DSC). The D. SXY starch showed the lower T(o) (74.2 degrees C) and the broader R (12.4). T(p) and T(c) of starch from D. 47 were higher than that of D. SXY starch. DeltaH(gel) values (11.37J/g) of D. 47 was higher than that of D. SXY starch (10.78J/g). The crystal type of starches separated from two different D. opposita cultivars was a typical C-type pattern. The degree of crystallinity of two D. opposita cultivars starches was about 45.9% and 31.5%, respectively.     

Physicochemical characterization of cellulose from perennial ryegrass leaves (Lolium perenne)

In this study, we investigated the physicochemical properties of the cellulosic preparations obtained from both untreated perennial ryegrass leaves and de-juiced leaves. It was found that treatment at 22 degrees C with 18% NaOH and 18% KOH for 2h, and 10% NaOH and 10% KOH for 16 h yielded 28.2%, 28.8%, 22.7%, 23.4%, respectively, of 'cellulose' residue from untreated ryegrass leaves and 35.7%, 36.8%, 32.8% and 34.6%, respectively, from the de-juiced leaves. For each cellulosic fraction, the glucose content was 71.6%, 69.6%, 67.8%, 66.7%, 69.7%, 68.6%, 63.9% and 61.7%, respectively. The structure of the cellulose samples was examined using FTIR and CP/MAS (13)C NMR spectroscopy and X-ray diffraction. The cellulosic preparations were free of bound lignin except for noticeable amounts of residual hemicelluloses (28.4-38.3%), and had intrinsic viscosities between 275.1 and 361.0 mL/g, along with molecular weights from 144,130 to 194,930 g/mol. This study found that the cellulose samples isolated from both de-juiced ryegrass leaves and the untreated leaves had a much lower percent crystallinity (33.0-38.6%) than that from wood-based fibres (60-70%) and had much shorter fibres (0.35-0.49 mm) than those of either cereal straws, bagasse or wood. In addition, a partial disruption of the hydrogen bonds and microfibrils may occur during the de-juicing process by mechanical activity, which results in a decreased cellulose crystallinity and fibre length. These findings are significant in relation to hydrolysing ryegrass cellulose for bio-ethanol production.     

Phase behaviour and crystallinity of plant cuticular waxes studied by Fourier transform infrared spectroscopy

The phase behaviour of cuticular waxes from leaves of Hedera helix L. and Juglans regia L. was studied by Fourier transform infrared spectroscopy. For this purpose reconstituted waxes, isolated cuticular membranes, dewaxed polymer matrix membranes and whole leaves were studied in the horizontal attenuated total reflection and transmission modes. Melting curves of cuticular waxes were derived from temperature-dependent changes in the absorption maximum of the symmetric stretching mode of CH₂ groups (ν_s, at approx. 2856–2848 cm⁻¹). With increasing temperature absorption band doublets due to CH₂ scissoring (δ_sciss) and rocking (δ_rock) movements (at approx. 1473–1471 and 730–720 cm⁻¹, respectively) indicative of an orthorhombic arrangement of alkyl chains merged into a single peak. The area ratio of the peaks at approx. 720 and 730 cm⁻¹ was used as a measure for aliphatic crystallinity of plant cuticular waxes at a given temperature. The investigations of reconstituted cuticular waxes and those still embedded in isolated cuticles or in situ on the leaf produced comparable results. The findings are discussed in terms of the properties of the cuticular transport barrier. Received: 21 March 1997 / Accepted: 25 April 1997     

Cellulose synthesized by Acetobacter xylinum in the presence of multi-walled carbon nanotubes

The structure of bacterial cellulose is affected by the bacterial strain used, culture media and cultivation conditions. In this study, acid-treated multi-walled carbon nanotubes (MWNTs) were added into a static culture medium and their effect on bacterial cellulose structure was studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), CP/MAS (13)C NMR and X-ray diffractometry. The bacterial cellulose ribbons and the MWNTs interwound and formed a three-dimensional network architecture. Band-like assemblies with sharp bends and rigidity were also produced in the presence of MWNTs. The intermolecular hydrogen bonds in bacterial cellulose produced in the presence of MWNTs were weakened. The crystal structure, cellulose I(alpha) content, crystallinity index (CrI) and crystallite size all changed. The results may suggest that the acid-treated MWNTs containing hydroxyl groups interact with the sub-elementary bacterial cellulose fibrils, subsequently interfering with the aggregation and crystallization.     

Crystalline structure analysis of cellulose treated with sodium hydroxide and carbon dioxide by means of X-ray diffraction and FTIR spectroscopy

Crystalline structures of cellulose (named as Cell 1), NaOH-treated cellulose (Cell 2), and subsequent CO2-treated cellulose (Cell 2-C) were analyzed by wide-angle X-ray diffraction and FTIR spectroscopy. Transformation from cellulose I to cellulose II was observed by X-ray diffraction for Cell 2 treated with 15-20 wt% NaOH. Subsequent treatment with CO2 also transformed the Cell 2-C treated with 5-10 wt% NaOH. Many of the FTIR bands including 2901, 1431, 1282, 1236, 1202, 1165, 1032, and 897 cm(-1) were shifted to higher wave number (by 2-13 cm(-1)). However, the bands at 3352, 1373, and 983 cm(-1) were shifted to lower wave number (by 3-95 cm(-1)). In contrast to the bands at 1337, 1114, and 1058 cm(-1), the absorbances measured at 1263, 993, 897, and 668 cm(-1) were increased. The FTIR spectra of hydrogen-bonded OH stretching vibrations at around 3352 cm(-1) were resolved into three bands for cellulose I and four bands for cellulose II, assuming that all the vibration modes follow Gaussian distribution. The bands of 1 (3518 cm(-1)), 2 (3349 cm(-1)), and 3 (3195 cm(-1)) were related to the sum of valence vibration of an H-bonded OH group and an intramolecular hydrogen bond of 2-OH ...O-6, intramolecular hydrogen bond of 3-OH...O-5 and the intermolecular hydrogen bond of 6-O...HO-3', respectively. Compared with the bands of cellulose I, a new band of 4 (3115 cm(-1)) related to intermolecular hydrogen bond of 2-OH...O-2' and/or intermolecular hydrogen bond of 6-OH...O-2' in cellulose II appeared. The crystallinity index (CI) was obtained by X-ray diffraction [CI(XD)] and FTIR spectroscopy [CI(IR)]. Including absorbance ratios such as A1431,1419/A897,894 and A1263/A1202,1200, the CI(IR) was evaluated by the absorbance ratios using all the characteristic absorbances of cellulose. The CI(XD) was calculated by the method of Jayme and Knolle. In addition, X-ray diffraction curves, with and without amorphous halo correction, were resolved into portions of cellulose I and cellulose II lattice. From the ratio of the peak area, that is, peak area of cellulose I (or cellulose II)/total peak area, CI(XD) were divided into CI(XD-CI) for cellulose I and CI(XD-CII) for cellulose II. The correlation between CI(XD-CI) (or CI(XD-CII)) and CI(IR) was evaluated, and the bands at 2901 (2802), 1373 (1376), 897 (894), 1263, 668 cm(-1) were good for the internal standard (or denominator) of CI(IR), which increased the correlation coefficient. Both fraction of the absorbances showing peak shift were assigned as the alternate components of CI(IR). The crystallite size was decreased to constant value for Cell 2 treated at >or= 15 wt% NaOH. The crystallite size of Cell 2-C (cellulose II) was smaller than that of Cell 2 (cellulose I) treated at 5-10 wt% NaOH. But the crystallite size of Cell 2-C (cellulose II) was larger than that of Cell 2 (cellulose II) treated at 15-20 wt% NaOH.     

Structure–properties relationship in cross-linked high amylose starch cast films

Cross-linked high amylose starch cast films were prepared to study the effect of cross-linking degree on various properties in normal environmental conditions. Mechanical tensile properties (Young's modulus, elongation at break, tensile strength), water vapour transmission rate (WVTR) and oxygen permeability coefficients of cast films were determined as a function of cross-linking degree and percentage of free humidity. Cross-linking degree and degree of crystallinity are closely related and seem to have non-negligible opposite effect on the properties of interest. By using increased amounts of cross-linking agents, the effect of cross-linking degree tends to reduce the degree of crystallinity modulating thus mechanical properties, water vapour permeability and oxygen permeability coefficients. Yield strength, tensile strength at break, WVTR versus cross-linking degree showed a non-monotonous behaviour. Maximal values for these properties were reached for moderate cross-linking degree. Optimal crystalline/amorphous ratio in the films may induce interactions and balanced effects, which would be responsible for the non-linear behaviour of some of the investigated properties. By cross-linking with epichlorohydrin in the range 1–10 g crosslinker/100 g polymer, the mechanical properties of films are still related to water content and water vapour permeability remains high compared to some synthetic polymeric materials.