The lignin fraction of animal feeding‐stuffs. II—Investigation of lignin determination procedures and development of a method for ‘acid‐insoluble lignin’

Moon, F. E.; Abou-raya, A. K.

doi:10.1002/jsfa.2740030906

Cited by 14 publications

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References 6 publications

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“…Furfurals produce pseudo-lignin when they react with proteins (29) . Earlier nutritional studies regarded the precipitate found on dilution and heating in the KL procedure as nonlignin matter (4,30) .…”

Section: Discussionmentioning

confidence: 99%

Klason lignin is a nutritionally heterogeneous fraction unsuitable for the prediction of forage neutral-detergent fibre digestibility in ruminants

et al. 2020

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Although lignin has been negatively correlated with neutral-detergent fibre (NDF) digestibility (NDFD) in ruminants and used to predict potential extent of NDF digestion of forages, selection of an analysis, Klason lignin (KL) or acid-detergent lignin (ADL), to describe that the nutritionally relevant lignin has not been resolved. Dismissed as an artifact is the difference between KL and ADL (ΔL). A question is whether ΔL influences NDFD. We evaluated the relationships of ΔL, KL and ADL with NDFD in order to determine the nutritionally homogeneous or heterogeneous nature of KL. Data sets from two laboratories (DS1 and DS2) were used that included ADL, KL and in vitro NDFD at 48 h (NDFD48). DS1 contained seven C3 grasses, seventeen C4 maize forages and nineteen alfalfas, and DS2 had fifteen C3 grasses, eight C4 forages and six alfalfas. Mean ΔL was greater than ADL in C3 and C4 samples and less in alfalfas. Within forage type and laboratory, ΔL was not correlated with NDFD48 (r −0·34–0·49; all P > 0·17). ADL was more consistently correlated with NDFD48 (r −0·47–−0·95; P < 0·01–0·21) than with KL (r 0·03–−0·91; P < 0·01–0·94). ΔL as a proportion of KL was correlated with NDFD48 in C3 and C4 samples (r 0·44–0·76; P < 0·01–0·08). The differing behaviours of ΔL and ADL relative to NDFD48 indicate that KL is a nutritionally heterogeneous fraction, the behaviour of which may vary by forage type and ratios of ADL and ΔL present.

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Section: Discussionmentioning

confidence: 99%

Klason lignin is a nutritionally heterogeneous fraction unsuitable for the prediction of forage neutral-detergent fibre digestibility in ruminants

et al. 2020

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Analytical studies on the carbohydrates of grasses and clovers. V.—Development of a method for the estimation of cell‐wall polysaccharides

Harwood

1954

J Sci Food Agric

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The cell-wall polysaccharides, i.e. the carbohydrate fraction of herbage that is insoluble in alcohol and cold water, are determined by a two-stage acid-hydrolysis procedure. In the first stage, treatment with N-sulphuric acid effects solution and hydrolysis of the greater part of the hemicellulose fraction, .with a maximum variability in any one sugar of 7% of the total hydrolysed. The remaining ' cellulose ' residue is saccharified with 72% sulphuric acid during the second stage, with agreement within 5%. IntroductionIn a review of the carbohydrate components of herbage Percivall divides this fraction into the non-structural components comprising monosaccharides, oligosaccharides and fructosan, and the structural carbohydrates cellulose, pentosans, galactan, pectin and glucosan. Two of the earlier papers in this series21 have dealt with the estimation of the monosaccharides and oligosaccharides soluble in 80% ethanol and the fructosan soluble in cold water. The present paper deals with the remaining structural or cell-wall polysaccharides.Schemes for the analysis of the cell-wall polysaccharides fall into two classes : those involving extraction of the pectins and hemicelluloses by various solvents ranging from hot water to strong alkalis, and those involving the complete hydrolysis of the whole polysaccharide fraction. Extraction procedures are of more benefit where a structural investigation is envisaged and generally follow a delignification step. Since there is some evidence that carbohydrates are lost during delignifi~ation,~-~ such a scheme appears unlikely to lead to a quantitative method of analysis. Hydrolysis procedures have the main drawback that a specific sugar may be destroyed by the acid conditions used. Such is the case with fructose-containing oligosaccharide~.~ This destruction may be avoided by a pre-hydrolysis with a weaker acid, the effect of which is to remove and hydrolyse many of the carbohydrate components present in smaller quantity7*The present investigation has led to a method involving a pre-hydrolysis with N-sulphuric acid followed by the complete hydrolysis of the carbohydrates in this solution. The residue

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The lignin fraction of animal feeding‐stuffs. IV.—The preparation of ‘reference’liganin by extraction with ethyl acetoacetate

Moon

Abou-raya

1954

J Sci Food Agric

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Ethyl acetoacetate was found t o be a satisfactory solvent for lignin, but not highly selective. The purest ' ester lignins ' were obtained from the residues after alkali extraction, and when mature plant materials were used these lignins showed little variation in methoxyl content. It is suggested that the percentage of methoxyl in pure lignin is not affected by plant maturity and that the true lignin present in a crude preparation may be determined from the methoxyl content by the use of an appropriate conversion factor. IntroductionThe determination of the lignin contents of plant materials by the attempted removal of all other substances and the weighing of the residues gives results that are far from satisfactory. Even when corrected for ash, there is still an unpredictable degree of contamination in the residue, due to both nitrogenous and non-nitrogenous substances, so that the true lignin content remains highly conjectural. From the results given in an earlier paper1 it appears that the total methoxyl in the crude lignin residue may be the best measure of the true lignin content, but although this may be useful in comparative work, such as digestibility measurements, it cannot be used to determine the absolute lignin content of any sample without a knowledge of the methoxyl content of the pure lignin. Moreover, it is generally believed that the methoxyl content of lignin is not constant, but varies with the age of the ~l a n t~-~ and with the species;5 the evidence on these points is far from conclusive, however. It was considered that, before further progress could be made with methods for the determination of lignin, some lignins of as Ggh a purity as possible should be prepared for reference purposes.Methoxyl and nitrogen contents were taken as the most reliable criteria of the purity of the various preparations. Crude lignin invariably has a high nitrogen content, but until there is satisfactory evidence to the contrary it is reasonable .to assume that pure lignin is nitrogen-free.Meyer & Bondi6 believe that the lignin molecule of plants contains nitrogen to the extent of 1-15%, but we have made about 20 different preparations of acid lignin from rye-grass hay and found them to have nitrogen contents varying from 0.3 to 5.6% according to the pretreatment, the nitrogen content of the material treated with 72% sulphuric acid and the degree of contamination with non-nitrogenous substances ; the nitrogen in lignin preparations is thus as variable as the mineral content and may equally be regarded as being due to contamination. Nitrogen content alone, however, is an inadequate index of purity, since contamination with carbohydrates may be quite considerable. If suitable pretreatments are employed to remove methoxyl-containing substances other than lignin, then the methoxyl content of the final preparation may serve as an index of freedom from carbohydrate contamination, and preparations with maximal methoxyl and minimal nitrogen contents are presumably the most pure.Brauns' extraction procedure for wood7 d...

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The lignin fraction of animal feeding‐stuffs. II—Investigation of lignin determination procedures and development of a method for ‘acid‐insoluble lignin’

Cited by 14 publications

References 6 publications

Klason lignin is a nutritionally heterogeneous fraction unsuitable for the prediction of forage neutral-detergent fibre digestibility in ruminants

Klason lignin is a nutritionally heterogeneous fraction unsuitable for the prediction of forage neutral-detergent fibre digestibility in ruminants

Analytical studies on the carbohydrates of grasses and clovers. V.—Development of a method for the estimation of cell‐wall polysaccharides

The lignin fraction of animal feeding‐stuffs. IV.—The preparation of ‘reference’liganin by extraction with ethyl acetoacetate

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