Dear all,
As you may know from the previous mail we are
looking for flavonoid retention
factors for vegetables, fruits, and
herbs in order to estimate the total flavonoid content after
drying and juicing
the fresh/raw products. We have already received a
number of responses -
thank you very much! - from which we noticed that we may not
have been clear
enough with respect to the information we are seeking.
Our aim is to estimate the overall
flavonoid uptake
from vegetable and fruit consumption. For the estimation we
are using the USDA
Database. Regrettably some values are missing, mainly for
dried fruits, dried
vegetables, dried herbs and fruit juices. In order to be
consistent with the estimation,
we try not to take data from the phenol-explorer to avoid
harmonization issues.
The phenol-explorer includes other analytical methods compared
to the USDA
database such as the folin assay and directly provides the
analytical values. In
addition, the flavonoid information in the phenol-explorer are
sometimes very
detailed for some and then more general for other foods. On
the other hand, the
USDA database includes data from studies which use preferably
HPLC as a method and
moreover, the USDA database converts glycosides into aglycones
to provide
comparable values. Values are provided as means, minimum and
maximum. We
believe that the USDA database is appropriate for our use.
Yet, some values for dried
fruits, dried vegetables
and dried herbs are missing (in both databases). We are looking
for a practical
solution to estimate the total flavonoid content of fruits,
herbs and
vegetables after drying or juicing the fresh/raw products.
The USDA calculates
missing flavonoid values from a
different form (raw/cooked or fresh/dry) of the same food by
using a retention
factor of 85% for all subclasses except 50% for anthocyanidins
(Bhagwat et al.
2013). Despite this statement the USDA gives an example how they
calculated
dried oregano however without further explanation.

(Bhagwat et al. 2013,
Table 3 modified).
Would it be acceptable to
apply the retention factor of
85% to estimate juicing processes?
A recent study found that
higher flavonoid values in
subgroups after drying processes in fruits (Slatnar et al.
2011). The phenol-explorer
shows that the flavonoid retention factors for fresh to dried
figs range from
1.15 to 3.68 (except for Anthocyanidines for which the retention
factor is 0.2)
and fresh to dried plums is 0.81.
From your expertise, would
you regard it justifiable
to
a) use an average from this range for figs and plums
and in a further step to
b) apply the mean of such average retention factors to fruits
for which no
retention factors are available - for example, to estimate the
flavonoid
content of dried dates or cranberries?
Would you suggest to use an overall mean retention factor for
fruits in general
or to generate mean retention factors by fruit subgroups (e.g.
berries, apples,
banana)?
Moreover, would it be a
proper attempt to also use an
average retention for the process of cooking or baking as well?
Thank you very much in advance!!
And have a good weekend.
Kind regards
Gesa Joslowski
***************************************************************************
References
Bhagwata S, Haytowitza DB,
Wasswa-Kintub SI, Holdena
JM. USDA Develops a Database for Flavonoids to Assess Dietary
Intakes. (2013) Procedia
Food Science 2:81–6
Slatnar A, Klancar U,
Stampar F, Veberic R. Effect of
drying of figs (Ficus carica L.) on the contents of sugars,
organic acids, and
phenolic compounds. (2011) Journal
of
Agricultural and Food Chemistry 59:11696-702
Dear Gesa, Happy New Year. Google Scholar searches on "retention of flavonoids heat treatment", "retention of flavonoids thermal processing" and "retention of flavonoids drying" give a few references that should make a start for your further investigations. All the best, Anders -----Original Message----- From: Food Composition Discussion Group [mailto:[log in to unmask]] On Behalf Of Gesa Joslowski Sent: 09 January 2014 10:07 To: [log in to unmask] Subject: Flavonoid retention factors Dear all, I am looking for information on flavonoid retention factors for vegetables, fruits, and herbs in order to estimate the flavonoid content (e.g. isoflavone or anthocyanidine content) after drying and juicing the fresh/raw products. Do you know a good literature source providing this information? It seems that fruits contain more polyphenols after drying. Do you know if that also applies to herbs? I am very grateful for your help! Best regards Gesa Joslowski University of Bonn IEL - Nutritional Epidemiology DONALD Study Heinstück 11 44225 Dortmund Phone: +49 231/7922 10 34 E-Mail: [log in to unmask] ######################################################################## To unsubscribe from the InFoods-Food-Comp-L list, click the following link: https://listserv.fao.org/cgi-bin/wa?SUBED1=InFoods-Food-Comp-L&A=1