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Correlation between amino acid racemization and processing conditions for various wheat products, oil seed press cakes and lignin samples

Paper ID Volume ID Publish Year Pages File Format Full-Text
18971 43038 2014 14 PDF Available
Title
Correlation between amino acid racemization and processing conditions for various wheat products, oil seed press cakes and lignin samples
Abstract

•Investigation of naturally occurring and processing induced d-amino acid formation.•Chiral GC–Iontrap MS analysis of protein-bound and free amino acids using enantiomer labeling.•d-Amino acid patterns for Ile, allo-Ile, Thr, allo-Thr and cis/trans-hydroxyproline.

The occurrence of d-amino acids in native and processed plant products is brought into context with the harshness of their treatment condition. It was found that already a small increase in processing harshness such as the milling efficiency of wheat straw or the increased pressure and duration of pumpkin seed oil extraction leads to traceable changes in the overall amino acid content as well as the racemization rate of free and protein bound amino acids. In the top position of our process harshness scale lies the strong alkali and heat-induced extraction of polyphenolic compound lignin from wood and other cellulose-rich plant fibers, e.g. wheat straw, during paper production. Since lignin accumulates in large quantities and its transformation into value-added “bio” products necessitates the recovery of native, functionally preserved lignin, milder pulping methods gain increasing interest. An unexpected drawback of such mild extraction conditions is however the high nitrogen content of such lignin products, which further increase with increasing mildness of the pulping procedure. The presence of amide bands in the FT-IR spectra of such mildly processed lignin has revealed that this nitrogen originated from co-extracted proteins and peptides. The total amino acid content as well as the free amino acid content and the degree of racemization was determined by gas chromatography–ion trap mass spectrometry (GC–Iontrap MS) employing enantiomer labeling for quantification. Cross-determination of the average amino acid content was calculated from nitrogen values obtained by elemental analysis and correlation factors were calculated from measured and calculated data. Since those amino acids with two chiral centers, such as isoleucine, threonine and hydroxyproline exhibit the highest possible diversity in terms of their relative amount to one another as well as their internal enantiomer distribution, this set of two-centered amino acids provided very distinct amino acid pattern, which proofed to be characteristic for the type of plant material as well as the harshness of the different processing conditions.

Graphical abstractComparison of d- and l-amino acid patterns of Ile, allo-Ile, Thr, allo-Thr and cis/trans-hydroxyproline for wheat related products including wheat straw, wheat flour and wheat straw lignin, pumpkin seed press cakes and various Kraft lignins.Figure optionsDownload full-size imageDownload high-quality image (254 K)Download as PowerPoint slide

Keywords
d-Amino acids; Allo-Isoleucine; Allo-threonine; cis/trans-Hydroxyproline; Wheat straw; Lignin
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Correlation between amino acid racemization and processing conditions for various wheat products, oil seed press cakes and lignin samples
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Publisher
Database: Elsevier - ScienceDirect
Journal: Food and Bioproducts Processing - Volume 92, Issue 4, October 2014, Pages 355–368
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us