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

 

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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



Am 09.01.2014 10:43, Anders Møller schrieb:
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]

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