Transformations of (14C-lignin) cell walls of wheat by rumen microorganisms

The lower halves of apical internodes of wheat harvested at the flowering stage were labelled with [U-¹⁴C] phenylalanine (phe) or with [O¹⁴CH₃] sinapic acid (sin). Cell wall residues (CWR) and saponified residues (SR) were incubated in a fermenter simulating the rumen for 7 days with rumen fluid or without microorganisms (controls). PheCWR was labelled in all lignin units (measured as aldehydes from nitrobenzene oxidation), in phenolic acids and slightly in proteins. Labelling of pheSR was more lignin-specific. SinCWR and sinSR were specifically labelled in syringyl units of lignin. The fermentation of CWR resulted in phenylpropane-derived unit losses in the following decreasing order: ferulic acid>p-coumaric acid>syringaldehyde>vanillin>p-hydroxybenzaldehyde. If allowance is made for slight losses in controls, 61, 52, 61 and 63% of the phenylpropanes of pheCWR, sinCWR, pheSR and sinSR, respectively, were transformed into an acid-precipitable fraction, an acid-soluble fraction and ¹⁴CO_2. The comparison of pheCWR and sinCWR degradation showed that syringyl units were solubilised into acid-precipitable molecules to a greater extent than the other lignin units; demethylation of the syringyl units of lignins was also evident from the different productions of ¹⁴CO₂. Alkali-resistant lignins of SR were mainly transformed into acid-precipitable molecules and were weakly degraded. Lignin solubilisation and degradation seem to be governed by different mechanisms which depend on both cell wall structure and rumen microflora.     

Biological variability in lignification of maize: Expression of the brown midrib bm2 mutation

The cell wall phenolic components in the internodes of three maize genotypes, namely normal, bm2 and bm3 maize, were determined. The bm2 and bm3 brown midrib mutations lowered the lignin content of the bottom, middle and top internodes to a similar extent. However, unlike bm3, the bm2 trait did not induce a sharp reduction of the level of ester-bound p-coumaric acid in maize internodes. The other main alkali labile phenolic acid, ferulic acid, reached similar levels in the three genotypes. The main difference between bm2 and bm3 mutations occurred in the alkyl aryl ether linked structures of the lignin component. In contrast to bm3 lignins, which are characterised by a low syringyl content, the bm2 lignin had a lower content of guaiacyl units than lignin of normal maize internode. Consequently, the syringyl/guaiacyl molar ratio of bm2 lignin gave higher values (2.7–3.2) than those from either normal (0.9–1.5) or bm3 lignins (0.3). The alkali solubility of lignin was also compared between the three genotypes. Incorporation of the bm3 trait in maize led to a high recovery of alkali soluble lignin whereas the bm2 lignin had a similar solubility to the normal one in 2 M NaOH. The monomeric composition of the alkali soluble lignins was consistent with the non-condensed structures of the in-situ polymer. Although the bm3 and bm2 mutations had different effects on lignification, the modification of the cell wall phenolic level was also found in the bm2 maize stem as previously studied.     

Biological variability in lignification of maize: Expression of the brown midrib bm3 mutation in three maize cultivars

Cell wall-linked phenolics were investigated in maize internodes located at three positions of the stem (top-middle-bottom). While the lignin content did not change drastically with position, the amount of cell wall-ester linked p-coumaric acid sharply increased from the top to the bottom internodes of the stem. Conversely, the saponified ferulic acid content remained relatively unchanged along the stem. Moreover, the highest syringyl content of the β-O-4-lignin structures was found in the basal (most mature) internode. Therefore, enhanced p-coumaric esterification of the cell wall and preferential deposition of syringyl units in the lignin polymer might indicate an extended maturity stage of the cell wall of maize internodes. The bm3 mutation in the three maize hybrids is expressed by lignin reduction and ester-bound p-coumaric decrease in the mutant lines. Furthermore, all bm3 hybrids synthesised lignin polymers which were characterised by a very low S/G molar ratio (0.16-0.43). This ratio originates from the substantial reduction of the syringyl unit content in β-O-4-lignin structures compared with the normal lignin. The occurrence in the same range of the 5-hydroxyguaiacyl unit in bm3 lignin from each type of hybrids was noteworthy, demonstrating the high heritability of the bm3 mutation at the molecular level. The alkaline solubility of lignin was greater for the three mutant lines compared to the normal cultivars. Furthermore, the alkali-labile fraction of lignin of both normal and mutant lines had a monomeric composition which was consistent with the non-condensed structures of in-situ lignin.     

Microbial degradation of normal maize and bm3 maize in the rumen observed by scanning electron microscopy

Samples of internodes and leaf blades from normal and bm3 maize (Zea mays L) harvested at dough to glazing stage were studied separately to determine their dry matter content, wall composition (NDF, ADF and ADL) and digestibility in sacco. For examination by light and scanning electron microscope, fragments 0·5 cm long were cut halfway along the internode beneath the female ear and on the corresponding blade. The wall and lignin contents of the bm3 maize were lower than in normal maize. The bm3 maize had a greater extent and faster rate of internode and blade disappearance in the rumen than normal maize samples. The histological structure of the two maizes was the same, but after 24 h in the rumen the parenchyma of the bm3 maize had degraded faster and the secondary walls of the fibres of its vascular bundles were degraded whereas those of normal maize had remained intact. After 72 h in the rumen the sclerenchyma of normal maize had changed little whereas that of the bm3 maize had much thinner walls and was abundantly colonised by rumen bacteria.     

Effect of down-regulation of cinnamyl alcohol dehydrogenase on cell wall composition and on degradability of tobacco stems

The effect of down-regulation of tobacco cinnamyl alcohol dehydrogenase (CAD) on cell wall composition and degradability has been assessed. CAD activity was only 20, 16, 14 and 7%, relative to the controls, in four populations of plants (designated 40-1, 40-2, 48 and 50, respectively) transformed with CAD antisense mRNA. Cell wall residues of stem samples were analysed for polysaccharide composition, gravimetric and acetyl bromide lignins and lignin nitrobenzene oxidation products. In situ disappearance and cellulase solubility of both initial dry matter and CWR were determined. The populations of plants with depressed CAD activity showed no change in lignin content but some consistent changes in cell wall composition and digestibility were identified. The syringyl content of lignins decreased and the syringaldehyde to vanillin ratio (S/V) was consequently reduced. Dry matter degradability, as measured by both methods, was significantly improved in all CAD-depressed samples except for population 40-1, which was the least CAD-depressed. Increased in situ disappearance of cell wall (ISCWD) was found in all plants exhibiting more than 80% CAD down-regulation and was maximal (7 percentage units) in population 50 which had the greatest CAD depression. The rates of ISCWD increased slightly in some populations (40-2 and 50). The relationship between S/V and ISCWD was significant (R = -0·68) only in the samples from a selected population of mature, most depleted plants. Other modifications may therefore also contribute to the improvement in degradability. However the changes in lignin composition that were observed in CAD-depressed tobacco are largely similar to those seen in some maize and sorghum mutants with altered lignification and improved digestibility. These data therefore suggest that depressing CAD activity may be an effective method for improving digestibility in forage crops. © 1998 SCI.     

Characterisation of Lignin from Parenchyma and Sclerenchyma Cell Walls of the Maize Internode

Internodes of maize (Zea mays L, Co125), harvested 5 days after anthesis, were sectioned into five equal parts and samples of sclerenchyma and parenchyma cells mechanically isolated from each section. Phenolic acids and syringyl and guaiacyl degradation products of lignin were released from the walls of the two cell types by microwave digestion with 4 M NaOH. Aryl ether bonded units were selectively released by thioacidolysis. Total phenolic content of cell walls from the youngest (basal) sections were approximately two-thirds of those of the oldest, topmost sections (parenchyma 70·8–99·0 and sclerenchyma 72·5–114·1 mg g^-1) indicating that the process of lignification was already well advanced amongst most of the cell walls of the youngest section. The total phenolic content was marginally, but significantly, greater (P<0·05) in sclerenchyma walls than in parenchyma walls at all stages of maturity. There was no significant difference in phenolic acid concentrations between cell types from the same section but p-coumaric acid concentration increased with maturity (P<0·001) in walls from both cell types. The increase in p-coumarate with age was matched by an increased recovery of syringyl units resulting in a constant coumaroyl: syringyl molar ratio. Recovery of acetosyringone was significantly greater (P<0·001) from sclerenchyma than parenchyma walls and, in sclerenchyma, acetosyringone as a proportion of total syringyl recovery, increased significantly with age (P=0·015). Digestion with NaOH and thioacidolysis released comparable amounts of guaiacyl residues but NaOH digestion released approximately twice the amount of syringyl residues. This difference may be explained by the retention of the ester-bond between p-coumaric acid and syringyl units during thioacidolysis but not during digestion with 4 M alkali. The similarity in phenolic composition suggested that both cell types, despite their considerable anatomical differences, were exposed to a common flux of lignin precursors during the later stages of lignification as illustrated by the internode sections. Differences between cell walls arose because of differences in the regiochemistry of precursor incorporation. © 1997 SCI.     

41—THE MEASUREMENT OF THE MEAN FIBRE DIAMETER OF WOOL SAMPLES BY LIQUID-SCINTILLATION SPECTROMETRY

In wool samples labelled uniformly with ¹⁴C, there is a good correlation between the mean fibre diameter and the proportion of β-radiation absorbed within the fibres. An account is given in this paper of the calibration of a method of measuring the mean fibre diameter, based on this principle, by applying it to a set of eight standard wool tops with known mean diameters. Subsequent tests with 23 other tops showed that the mean fibre diameter of small samples (75–100 mg) could be determined with good precision, the mean 95 % confidence limits for a single measurement on one test specimen being ±0–36 μm.

A test of the sampling and uniformity of the standard tops showed that similar results, within currently accepted limits, were obtained when test specimens (75 mg) were taken from any of ten randomly chosen positions along each top.     

Roles of structural phenylpropanoids in forage cell wall digestion

Phenolic constituents (lignins and phenolic acids) and carbohydrates are assembled in a tight architecture which differs according to the plant species. During cell wall digestion, the hydrolysis kinetics differ between carbohydrates and seem to depend chiefly on the content and organisation of tissue phenolics. Among the phenylpropanoids, ferulic acid is released more quickly than p-coumaric acid. Lignins remain largely in the cell walls. They also undergo transformations, chiefly solubilisation as lignin-carbohydrate complexes. The limiting effect of lignins on cell wall degradation increases with increasing content. However, their effect on degradation might also depend on qualitative factors such as lignin structure and polymer organisation in walls and tissues. When various grasses (normal and selected genotypes), or grasses and legumes are compared, correlations between certain factors such as lignin uncondensed fraction, syringyl units or phenolic acids contents and cell wall degradation emerge but not clear causal relationship has been shown. Nonetheless, other structural characteristics, related to the alkali reactivity of lignins, seem to have a stronger influence on cell wall degradation. Phenylpropanoids seem to act mainly as a physical and (bio)chemical barrier to the action of the microbial enzymes. In addition, their reactivity as phenolic compounds and their hydrophobicity seem to play a role. Digestion is not limited only by phenolics. The factors that limit glycanolysis—the accessibility, crystallinity and capillary structure of cellulose and the branching of hemicelluloses—seem to have little or no effect on cell wall degradation in vivo. In contrast, other antiquality substances (tannins, cutin and silica), plant antomy, environmental factors, factors modulating microbial growth and animal physiology influence cell wall utilisation. Future research in this field should focus on the effects of phenolic structure and of cell wall and tissue organisation on carbohydrate degradation.     

猕猴桃蛋白酶及发酵剂对马肉发酵香肠品质特性的影响

研究发酵剂和猕猴桃蛋白酶对马肉发酵香肠品质的影响。以新鲜马肉为原料,添加发酵剂和猕猴桃蛋白酶进行发酵,检测其对马肉发酵香肠pH值、水分活度（water activity,aw）、水分含量、色差以及硫代巴比妥酸（thiobarbituric acid,TBA）值等的影响,并通过对成品进行感官评价确定发酵剂和猕猴桃蛋白酶对其感官品质的影响。结果表明：与对照组相比,发酵剂处理组（A组）显著降低了马肉发酵香肠的pH值、aw和TBA值,加快了水分含量的下降,提高了亮度值（L*）和红度值（a*）,后期黄度值（b*）略有下降;与A组相比,发酵剂和猕猴桃蛋白酶处理组（B组）提高了其pH值,降低了aw,加快了水分含量的下降,而对a*、L*、b*影响不大,对TBA值无显著影响;对成品的感官评价结果表明,B组马肉发酵香肠的口感较A组和对照组好。     

High pressure treatments on the inactivation of Salmonella Enteritidis and the physicochemical, rheological and color characteristics of sliced vacuum-packaged dry-cured ham

The effect of high pressure (HP) on Salmonella Enteritidis in sliced dry-cured ham stored under temperature abuse (8°C) during 60d was investigated. After treatment, reductions of S. Enteritidis were 1.06, 2.54 and 4.32 log units in ham treated at 400, 500 and 600MPa for 5min at 12°C, compared to non-pressurized samples. After 60d, counts of S. Enteritidis in ham treated at 400 and 500MPa were 2.56 and 2.66 log units lower than in non-treated ham, whereas the pathogen was only detected after enrichment in ham treated at 600MPa. Lipid oxidation increased with storage and pressurization, whereas total free amino acid contents were similar in HP and control samples after 60d. Dry-cured ham treated at the highest pressures exhibited lower shear resistance, whereas the maximum force to compress the sample was slightly changed. Color (L*, a* and b*) varied with pressurization and storage. Changes induced by HP in dry-cured ham were attenuated during storage.     

Fractionation and characterization of ball‐milled and enzyme lignins from abaca fibre

An Erratum has been published for this article in Journal of the Science of Food and Agriculture 79(15) 1999, 2122. Ball‐milled and enzyme lignins were produced from abaca fibre via ball milling for 6 days followed by cellulase treatment for 3 days. The crude lignin preparations were fractionated into milled lignin (ML), enzyme lignin (EL), hemicellulose‐rich milled lignin (HRML), and lignin‐rich enzyme lignin (LREL) fractions using a two‐step precipitation method instead of a traditional ether precipitation procedure. The yield and chemical composition of the resulting lignin samples are reported. The ML and EL fractions contained low amounts of associated neutral sugars (2.0–3.3%) and uronic acids (1.4–1.5%), and showed relatively low average molecular weights (2500–2660), while the LREL and HRML fractions contained large amounts of bound polysaccharides (35.6–38.3%), and showed high molecular weights (8800–25000). The four lignin fractions are composed of a large proportion of syringyl units with fewer guaiacyl and p‐hydroxyphenyl units. The ML is mainly composed of β–O–4 ether bonds between the lignin structural units. The less common β–β, β–5 and 5–5′ carbon–carbon linkages are also present in the lignin molecules. It was found that uronic acids and 41–63% of p‐coumaric acids are esterified to lignin in the three lignin‐rich fractions of ML, EL and LREL. This level increased to over 90% in the hemicellulose‐rich fraction of HRML. For ferulic acids, 92–97% were found to be etherified to lignin in the three lignin‐rich fractions of ML, EL and LREL, while in the hemicellulose‐rich fraction of HRML this reduced to only 13%, suggesting that a majority of the ferulic acids are esterified to hemicelluloses or lignin in this fraction. © 1999 Society of Chemical Industry     

COMPLEX VISCOSITY-TEMPERATURE MASTER CURVE OF CORNSTARCH DISPERSION DURING GELATINIZATION

Complex viscosity (η*) of 8% cornstarch dispersion during gelatinization at oscillatory frequencies (ω): 0.63–47.12 (rad s^?1) was independent of the heating rates: 1.6–6.0 (°C min^?1) when temperature was the independent variable. The influence of ω on η* was scaled by a frequency shift factor resulting in reduced complex viscosity (η*_R) versus temperature (60–95C) master curve. Similar η*_R master curves were derived for data on 6% and 3.5% dispersions. A modified Cox-Merz rule correlated the complex and apparent viscosity data, and a power law model described the effect of concentration of the gelatinized structures.     

Comparison of the Stability of Pelargonidin-based Anthocyanins in Strawberry Juice and Concentrate

Strawberries were processed into juice (8° Brix) and concentrate (65° Brix) and different lots were fortified with pelargonidin 3‐glucoside, pelargonidin 3‐sophoroside, and acylated pelargonidin 3‐sophoroside 5‐glucoside. Changes in pigment concentration, color (CIE L*a*b*) and ascorbic acid content were monitored during storage at 25 °C. Anthocyanin and ascorbic acid degradations followed 1^st order reaction kinetics. Fortification increased the half‐life of the pigments from 3.5 to 5 d in concentrate and from 5 to 12 d in juice. The half‐life of ascorbic acid was 2 d in juice samples and ranged from 3 to 10 d in concentrate samples. Both systems showed changes in chroma and hue angle, but maintained L* values.     

A Comparative Analysis of Colour Measurements of the Seed Coat and Endosperm of Wheat Kernels Performed by Various Techniques

The results of this present studies show that the colour of the seed coat of wheat kernels can be determined by digital image analysis (DIA) instead of spectrophotometry. High linear correlations (p < 0.05) were found between colour measurements of the seed coat performed by these techniques. The colour on the cross-sections of wheat kernels was related to the colour of their seed coat. A high correlation was also observed between the colour of the seed coat and the colour of the endosperm of wheat kernels. In all measurements colour was described by the RGB, XYZ, and L*a*b* models. Colour indices, i.e. hue (h⁰) and saturation (S*) were also calculated.     

Monitoring Phenolic Composition of Maturing Maize Stover by High Performance Liquid Chromatography and Pyrolysis/Gas Chromatography/Mass Spectrometry*

Maize stovers collected every 14 days over an 84-day growth period were subjected to high-performance liquid chromatography with electrochemical detector (HPLC-ED) and pyrolysis/gas chromatography/mass spectrometry (PY/GC/MS) in order to monitor changes in the phenolic composition. Prior to HPLC-ED analyses, ground samples were sequentially extracted with (i) methanol, (ii) 0·1M sodium hydroxide and (iii) 2M sodium hydroxide in the presence of nitrobenzene to separate, respectively, free phenolic monomers, alkali-labile phenolic monomers and alkali-resistant lignin. In turn, solution (ii) was treated with alkaline nitrobenzene to obtain (iv) alkali-labile lignin. Pyrolysis was carried out on ground native samples by using a platinum heated filament pyrolyser. Increases in the absolute phenolic concentrations in the residues of 0·1M sodium hydroxide extraction and in the ratio of alkali-resistant lignin vs total lignin were observed by HPLC-ED during the first 28–42 days of maturation, reaching a steady level in the remaining maturation period. A linear increase of syringyl units vs guaiacyl units was for found the alkali-resistant lignin fraction over the entire period of maturation. Similar trends were showed by PY/GC/MS with regard to relative lignin content and syringyl/guaiacyl ratio. Both techniques showed their usefulness to gauge changes in the phenolic composition during the lignification process.     

The measurement of hair colour

The colour of the hair of 65 subjects was measured using a Minolta Chromameter model CR200. Readings were taken by holding the unit against the back of the subject's head, and recorded using the L*a*b* system of colour co-ordinates.
All subjects had hair in which yellow and red (rather than blue or green) dominated. The lightness (L*) of all hair fell in the range 17–67, the redness (a*) in the range 0–6 and the yellowness (b*) 0–20. These limits can be seen as effectively outlining the range of colours which can be said to be natural.
The chromameter gave rapid and reproducible results on hair in situ and was easy to use. The method should be of use to those who wish to quantify the effects brought about by bleaching or dyeing formulations.     

Characterization of p‐coumarate accumulation,p‐coumaroyl transferase,and cell wall changes during the development of corn stems

BACKGROUND: Developmental changes occur in corn (Zea mays L.) stems from cell initiation to fully mature cell types. During cell wall maturation the lignin is acylated with p‐coumarates (pCA). This work describes characterization studies of the p‐coumaroylation process in relation to corn stem development. RESULTS: Corn plants from three locations were harvested and tissues were analyzed from all nodes and even‐numbered internodes above soil line. Changes in carbohydrates reflect a shift to lignification at the expense of structural polysaccharide synthesis. Accumulation of pCA paralleled the incorporation of lignin while ferulate (FA) remained relatively constant as a proportion of the cell wall (5–7 g kg^?1 CW). The p‐coumaroyl transferase (pCAT), which is responsible for attaching pCA to lignin monomers, displayed maximum levels of activity in the middle region of the stem (internodes 10–12, 2–3 nmol L^?1 min^?1 mg^?1). The syringyl content as a proportion of the total lignin did not change significantly with cell wall maturation although there was a trend towards increased amounts of syringyl units in the more mature cell walls. CONCLUSIONS: Incorporation of pCA into corn cell walls not only mirrored lignification but the pCAT activity as well. Levels of pCAT activity may be an indicator of rapid lignification specifically for syringyl type lignin. Copyright © 2008 Society of Chemical Industry     

Influence of the protein distribution of maize endosperm on ruminal starch degradability

This study was aimed at determining the influence of the protein distribution of maize endosperm on ruminal starch degradation using 14 maizes differing in endosperm texture (eight dent and six flint maizes). Ruminal starch degradability was determined by an in situ technique on ground samples with a particle size of 3 mm. The distribution of endosperm proteins was assayed by a method based on their differential solubilities in solvents. The (α,β,δ)‐zeins and the true glutelins were the predominant proteins in the endosperm. The (α,β,δ)‐zeins (66.1 and 70.1 g kg⁻¹ of recovered protein for dent and flint types respectively) and the true glutelins (21.8 and 18.4 g kg⁻¹ of recovered protein for dent and flint types respectively) were related to the vitreousness, ie the ratio of vitreous to floury endosperm. Ruminal starch degradability averaged 619 and 462 g kg⁻¹ for dent and flint maizes respectively. It was correlated negatively with the (α,β,δ)‐zeins and positively with the true glutelins. The (α,β,δ)‐zeins located in the protein bodies should limit the accessibility of starch granules to ruminal micro‐organisms and, as a consequence, the ruminal starch degradability. © 2000 Society of Chemical Industry     

Effects of brown midrib 3 mutation in corn silage on dry matter intake and productivity of high yielding dairy cows

The effects of enhanced in vitro neutral detergent fiber (NDF) digestibility of corn silage on dry matter intake (DMI) and milk yield were evaluated using 32 Holstein cows in a crossover design with 28-d periods. At the beginning of the experiment, cows were 89 d in milk and yielded 45.6 kg/d of milk. Experimental diets contained either brown midrib (bm3) corn silage or isogenic normal corn silage (control) at 44.6% of DM. The NDF digestibility estimated by 30-h in vitro fermentation was higher for bm3 corn silage by 9.7 units. Contents of NDF and lignin were lower for bm3 corn silage by 1.8 and 0.8 units, respectively. Diets were formulated to contain 19% crude protein and 31% NDF and to have a forage to concentrate ratio of 56:44. Daily DMI, milk yield (3.5% fat-corrected milk), and solids-corrected milk were 2.1, 2.6, and 2.7 kg higher, respectively, for cows fed bm3 corn silage. The milk protein and lactose contents were greater for bm3 treatment, but milk fat content was not. Individual milk yield responses of the cows to bm3 treatment were positively related to pretrial milk yield, and DMI response tended to be positively related to pretrial milk yield. Enhanced in vitro NDF digestibility was associated with higher energy intake, which resulted in increased milk yield.     

SUPERPOSITION OF COMPLEX VISCOSITY CURVES DURING GELATINIZATION OF STARCH DISPERSION AND DOUGH

Complex viscosity (η*) of 8% tapioca starch dispersion (STD) during gelatinization at a specific oscillatory frequency (ω, rad s^?1) was independent of the heating rates: 1.5 to 6.0C min^?1 when plotted against temperature as the independent variable instead of time. The influence of ω in the range: 3.14 to 62.83 rad s^?1 on η* was scaled by a frequency shift factor resulting in a reduced complex viscosity (η*_R) versus temperature (58–88C) master curve. Similar η*_R versus temperature master curves were derived for η* data on a 8% waxy rice STD at the heating rate 2C min^?1 and ω values 1.27 to 125.6 rad s^?1, and a 45.5% waxy rice dough at the heating rate 4C min^?1 and ω values 1.27 to 94.2 rad s^?1. The areas under the η*, at ω=6.28 rad s^?1, versus temperature curves of the tapioca and the waxy rice STDs with different starch concentrations were exponentially related to the concentrations.