Determination of L- and D-methionine and L- and D-valine in soy isolate and soy flour samples

L to D isomerization of amino acids in a commercially prepared alkali-treated food-grade soy isolate was investigated. A soy flour product was also investigated as a control which had not been alkali treated. Methionine and valine collected from two soy flour and two soy isolate samples were coupled with L-leucine-N-carboxyanhydride. If both D- and L-forms were present this would produce diastereomeric dipeptide derivatives. The derivatives were separated by ion-exchange chromatography using a TSM Amino Acid Analyzer. Comparison of the sample methionine and valine dipeptide peaks to standard dipeptide peaks revealed the presence of L-valine, L-methionine and D-methionine in both soy flour and soy isolate samples. Methionine was substantially isomerized in both products. D-valine was not observed in either soy flour or soy isolate samples. Thus, isomerization of methionine appeared to occur at a faster rate than valine. Acid hydrolysis, toasting of soy meal, and alkaline treatment are all conditions which may be responsible for the isomerization of methionine.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Human Nutrition and Foods

Department dc:contributor.department

Human Nutrition and Foods

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1977

Author dc:creator

• Gilbert, Laura Marcella

Chair dc:contributor.committeechair

• Marable, Nina L.

Committee members dc:contributor.committeemember

• Korslund, Mary K.
• Sanzone, George

• alkaline treatment
• toasting of soy meal
• isomerization of methionine
• L-methionine and D-methionine

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-07282010-020132

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/43937