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Degradability of phenolic acid‐hemicellulose esters: A model system
Author(s) -
Jung HansJoachim G,
Ralph John,
Hatfield Ronald D
Publication year - 1991
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740560407
Subject(s) - hemicellulose , ferulic acid , chemistry , organic chemistry , xylose , cellulose , phenolic acid , lignin , food science , chromatography , biochemistry , fermentation , antioxidant
A synthetic model system containing p‐coumaric and ferulic acids esterified to hemicellulose was used to study polysaccharide degradability. Oatspelts xylan was fractionated into A linear , B linear and B ranched fractions prior to synthetic esterification with phenolic acids at treatment concentrations of 0, 25, 50, 75 and 100 g phenolic acid per kg hemicellulose. Concentrations of phenolic acids esterified to the hemicellulose fractions were determined by alkaline hydrolysis. In‐vitro dry matter disappearance (IVDMD) and degradability of hemicellulose neutral sugars were measured after 48 h ruminal fermentations. Esterification efficiency of the phenolic acids to the hemicellulose fractions was low (0.3 to 13.9%) and greater for p‐coumaric than ferulic acid (4.7 vs 3.1%, respectively). Concentration of esterified phenolic acids was negatively correlated with IVDMD for the A linear and B branched fractions. Ferulic acid appeared to be more inhibitory to IVDMD than p‐coumaric acid. Generally the degradability of the side chain sugars of the hemicellulose fractions was negatively correlated with esterified phenolic acid concentrations. Xylose degradation was only correlated with esterified ferulic acid level in the A linear fraction. The in‐vitro ruminal fermentations resulted in the degradation of the majority of the phenolic acid esters. Analysis of the synthetic phenolic acid‐hemicellulose esters by 13 C NMR and FTIR was unable to prove the presence of monomeric phenolic acid esters. The presence of phenolic acid polyesters was unlikely because of the solubility of the synthetic phenolic acid‐hemicellulose esters. The neutral sugar degradation data suggest that esterification of the phenolic acids was limited to sugars with primary hydroxyl groups. While this model system was useful for studying cell wall degradation, future studies must employ model systems in which the chemical constituents being tested accurately model those found in nature.