Interference of Condensed Tannin in Lignin Analyses of Dry Bean and Forage Crops

Abstract

Legumes with high concentrations of condensed tannin (pinto bean [Phaseolus vulgaris L.], sainfoin [Onobrychis viciifolia Scop.], and big trefoil [Lotus uliginosus Hoff.]), were compared to a selection of forages, with low or zero condensed tannin (smooth bromegrass [ Bromus inermis Leyss], Lotus japonicus [Regel] K. Larsen, and alfalfa [Medicago sativa L.]), using four methods to estimate fiber or lignin. Protocols were validated by using semipurified condensed tannin polymers in adulteration assays that tested low-lignin tissue with polyphenolic-enriched samples. The effect on lignin assay methods by condensed tannin concentration was interpreted using a multivariate analysis. There was an overestimation of fiber or lignin in the presence of condensed tannin in the acid detergent fiber (ADF) and Klason lignin (KL) assays compared to that in the thioglycolic acid (TGA) and acid detergent lignin (ADL) methods. Sulfite reagents (present in TGA lignin method) or sequential acidic digests at high temperatures (ADF followed by ADL) were required to eliminate condensed tannin. The ADF (alone) and KL protocols are not recommended to screen nonwoody plants, such as forages, where condensed tannin has accumulated in the tissue.

Fermentation kinetics of sainfoin hay with and without PEG

“…phenols). Indeed, forages containing polyphenolic compounds, such as CTs, may be problematic in the measurement of lignin (Marles et al., 2008). In particular, the authors evaluated the sensitivity assay to CT interference by processing sainfoin CT polymer alone with the following methods: spectrophotometric thiologlycol acid lignin, Klason lignin (KL) and ADL (Goering and Van Soest, 1970).…”

Genotypic abundance of carotenoids and polyphenolics in the hull of field pea (Pisum sativum L.)

“…The polyphenolics extraction was a sequential method using three different solvents: (i) 80% aqueous MeOH followed by 100% MeOH; (ii) 100% acetone followed by 70% aqueous acetone. Flavonoids and phenolic acids are soluble in the former two MeOH solvents (depending on whether they are glycosylated or occur as aglycones) . Condensed tannin (CT) is soluble in 70% but is not eluted in 100% acetone , …”

“…Generally, these specific changes are subject to the plant species and environmental effects , . Cross‐linking to other cellular products (proteins, cell wall matrices) renders changes to extractability and detection, particularly for CT …”

Comparing lignocellulose physiochemistry after decomposition by brown rot fungi with distinct evolutionary origins

“…(Cowling, 1961). These by-products can co-precipitate with acid-insoluble lignin during acid treatment, inflating the apparent lignin content of the sample in an irreproducible manner (Dean, 1997;Marles et al, 2008;Sluiter et al, 2008). Although brown rot fungi are typically associated with conifers, brown rot-angiosperm associations are common, with Laetiporus sulphureus on oak and P. betulinus on birch as examples.…”

“…Products of lignin oxidation like benzoic acids, benzaldehydes and phenylglycerols (Yelle et al ., ) are likely removed during ethanol extraction, a step that was not included in early chronological studies of brown rot component loss (Cowling, ). These by‐products can co‐precipitate with acid‐insoluble lignin during acid treatment, inflating the apparent lignin content of the sample in an irreproducible manner (Dean, ; Marles et al ., ; Sluiter et al ., ). Although brown rot fungi are typically associated with conifers, brown rot‐angiosperm associations are common, with Laetiporus sulphureus on oak and P. betulinus on birch as examples.…”