|Title||Leaf phenolics and seaweed tannins : analysis, enzymatic oxidation and non-covalent protein binding|
|Author(s)||Vissers, Anne M.|
|Source||University. Promotor(en): Harry Gruppen; Wouter Hendriks, co-promotor(en): Jean-Paul Vincken. - Wageningen : Wageningen University - ISBN 9789463432023 - 154|
Food Chemistry Group
|Publication type||Dissertation, internally prepared|
|Keyword(s)||phenols - leaves - seaweeds - tannins - beta vulgaris - laminaria - proteins - catechol oxidase - nuclear magnetic resonance spectroscopy - in vitro - mass spectrometry - browning - fermentation - animal feeding - fenolen - bladeren - zeewieren - tanninen - eiwitten - kernmagnetische resonantiespectroscopie - massaspectrometrie - bruinkleuring - fermentatie - diervoedering|
|Categories||Animal Nutrition and Feeding (General)|
Upon extraction of proteins from sugar beet leaves (Beta vulgaris L.) and oarweed (Laminaria digitata) for animal food and feed purposes, endogenous phenolics and proteins can interact with each other, which might affect the protein’s applicability. Sugar beet leaf proteins might become covalently modified by phenolics through polyphenol oxidase (PPO) activity. Oligomeric phenolics from seaweed (so-called phlorotannins (PhT)) might bind non-covalently to protein. The first aim of this thesis was to study factors involved in protein modification by phenolics. The second aim was to investigate the effect of PhT supplementation to feed on in vitro ruminal fermentation.
Besides PPO activity and the amount of low molecular weight phenolic substrates present, brown colour formation in sugar beet leaves was dependent on the amount of phenolics, which do not serve as a substrate of PPO. These non-substrate phenolics can engage in browning reactions by oxidative coupling and subsequent coupled oxidation of the products formed. Similar reactions might also be involved in covalent protein modification by phenolics, and therewith protein properties.