Number: 2005-041-2-500
Title: Determination of selenomethionine in selenized yeast
supplements
Task Group
Chairman: Zoltan Mester
Members: Chunying
Chen, Heidi
Goenaga-Infante, Joanna
Szpunar, and Wayne Wolf
Objective:
To provide the analytical, nutrition- and health- science community
with clear guidelines on the determination of selenomethionine (the
most abundant Se species) in yeast and yeast-based products.
Description:
Consumption of Se enriched food and feed supplements has increased dramatically
as a result of the numerous health benefits reported, including protection
of cells against the effects of free radicals, the normal functioning
of the immune system and thyroid gland as well as protection against
various forms of cancers. Yeast based supplements have emerged as an
acknowledged means of alleviating selenium nutrient deficiencies, but
it is evident from earlier studies that they are inconsistent in their
makeup relative to label indications. Production of yeast-supplements,
both animal and human, is a rapidly growing industry. IUPAC had already
addressed the methodology of selenium speciation in biological materials
in a report (Pure
Appl. Chem.,
Vol. 72, No. 3, pp. 447-461, 2000). The report had a decent impact
on the research community having obtained over 60 citations (Source:
ISI)
Since then the concerns have focused around the determination of selenomethionine
(SeMet) which is the dominant Se species in yeast based Se supplements.
It is easier bioavailable and less toxic than selenite. Significant
efforts have been made in the development of analytical methods for
the speciation of Se in yeast in five recent years. Extraction procedures
used are of paramount importance for the accurate determination of SeMet
in yeast or other solid samples. Numerous extraction techniques have
been developed for the extraction of SeMet in yeast. Despite this recent
round-robin exercises show huge discrepancies among the results obtained
by different methods published in peer-review literature. As much as
10-fold difference in the measured amount of SeMet was observed which
is an amazingly poor performance for the measurement of a nutritional
supplement ingredient. There is still a lack of consensus regarding
whether there are forms of selenium other than selenomethionine in yeast
but any of the procedures accounted for more than 80% of selenomethionine
so far. Consequently, the major 4 industrial companies producing selenized
yeast boast their selenomethionine content as a proof of the quality
of their yeast without that a consensus exists on the methodology used
and the validity of the measurements supplied.
The purpose of this project is to examine critically the existing methodology
published in peer reviewed journals, and issue recommendations on the
determination of this extremely important nutritional supplement. The
task group is composed of scientists having a considerable experience
in the field and a record of collaborations with different industrial
companies interested in this issue. The work is going to be carried
out in close collaboration with the potential stakeholders: the four
major companies on the market: Alltech, Lallemand, Lesaffre and PharmaNord.
Progress:
Last Update: 6 June 2006
<project announcement published in
Chem. Int.
Sep-Oct 2006>