The degradation of chlorophyll pigments in dairy silage: the timeline of anaerobic fermentation

BACKGROUND Detection of chlorophyll metabolites in milk has recently been suggested to be an indicator of a grass‐fed diet fed for cattle. Such a means of detection, however, is complicated when the grazing season is over because cattle can be fed fermented silage ingredients, such as alfalfa and co...

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Bibliographic Details
Published in:Journal of the science of food and agriculture 2021-05, Vol.101 (7), p.2863-2868
Main Authors: Santra, Kalyan, Song, Anthony, Petrich, Jacob W, Rasmussen, Mark A
Format: Article
Language:English
Subjects:
absorption
Absorption spectra
Alfalfa
Anaerobiosis
Animal Feed - analysis
Animals
Cattle
Cattle - metabolism
Chlorophyll
Chlorophyll - chemistry
Chlorophyll - metabolism
Corn silage
Cow's milk
Dairy cattle
Degradation
Degradation products
Digestion
Female
Fermentation
Fluorescence
Grasses
Lactic acid
Magnesium
Medicago sativa - chemistry
Medicago sativa - metabolism
Metabolites
Milk
Milk - chemistry
Milk - metabolism
Pasture
Phaeophytin
Phytol
Pigments
Rumen - chemistry
Rumen - metabolism
Silage
Silage - analysis
Spectrophotometry, Atomic
Zea mays - chemistry
Zea mays - metabolism
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Summary:BACKGROUND Detection of chlorophyll metabolites in milk has recently been suggested to be an indicator of a grass‐fed diet fed for cattle. Such a means of detection, however, is complicated when the grazing season is over because cattle can be fed fermented silage ingredients, such as alfalfa and corn silage. During fermentation, chlorophyll compounds and other pigments undergo degradation due to the accumulation of lactic acid and the resultant decline in pH. RESULTS We monitored degradation of chlorophyll compounds by measuring the fluorescence and absorption spectra of silage extracts. The spectroscopic evidence supports the hypothesis that chlorophylls are converted into fluorescent products, such as pheophytin, and further cleaved into pheophorbide. The degradation starts with dechelation and removal of the magnesium ion to produce pheophytin. Further removal of the phytol chain from pheophytin results in the production of pheophorbide. CONCLUSIONS The fluorescence intensity of these degradation products is reduced compared to that of the parent molecule. These findings are important in understanding the fluorescent signal in milk when cows consume silage rather than fresh pasture grass. © 2020 Society of Chemical Industry
ISSN:0022-5142
1097-0010
DOI:10.1002/jsfa.10917