[Nhcoll-l] bagging and thawing or thawing and bagging?

[Dirk Neumann]

Hi Rob (and all),

that was my thought, too. Because they are frozen in boxes for 
considerable time now and have been obviously thoroughly sun-dried 
before shipping (they are like wooden boards), the fins in a close to 
freeze-dried condition. By bagging them frozen in small batches (only if 
the fins are free of ice crystals) my intention was to shift the point 
of condensation to the outside of the PE-bag away from the tissue. 
Adding desiccant packets into the bags as recommended by Andy and Thomas 
surely is a good idea, I also planned put desiccant into the boxes to 
keep the bags in a as stable as possible microclimate inside the boxes.

On the points that Paul raised (shrinkage, embrittlement and bacteria 
growth) the first two are absolutely valid - the fins show significant 
signs of shrinkage, but we largely have dorsal, pectoral and pelvic fins 
- which are very sturdy in most sharks - crumbling membranes (or fin 
rays, of course) are not too much of a problem. The third, bacterial 
growth is an interesting one: while we recently had some mould issues on 
prepared bony fish skeletons due our malfunctioning climate control 
systems, there were absolutely no signs of mould or bacterial growth on 
our dry shark jaws or sawfish saws (both are kept dry and open in our 
storage area).

Many thanks for all your thoughtful replies, much appreciated!

With best wishes
Dirk


Am 22.09.2020 um 18:45 schrieb Robert Waller:
>
> Hi Dirk,
>
> Just for clarification, when we have an impermeable barrier between 
> cold and warm, condensation will occur on the warm side of the 
> barrier. In this case, condensation due to a thermal gradient would 
> occur on the outside of the bag. If there is no ice on the specimens 
> then we would expect the RH within the bag to remain moderate to low. 
> Always good to check that by monitoring at least for the first bag you 
> deal with.
>
> Rob
>
> *From:* Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu> *On Behalf Of 
> *Dirk Neumann
> *Sent:* Tuesday, September 22, 2020 6:58 AM
> *To:* nhcoll-l at mailman.yale.edu
> *Subject:* [Nhcoll-l] bagging and thawing or thawing and bagging?
>
> Hi all,
>
> a brief question regarding bagging of dry shark fins that were 
> confiscated by customs (approx. 50 kg) and deposited in our 
> collection. When the material arrived, boxes were full of life with 
> thick layers of beetle remains at their bottom. We kept the fins 
> mostly frozen so far (several freezing / thawing cycles to kill the 
> critters) but now have to move the fins into our storage area where 
> they will be kept at room temperature.
>
> Because of major renovation works, our climate control systems are 
> currently shut down thus temperature and rH are fluctuating and not 
> really stable, thus I was wondering if I should seal small subsets 
> (5-10 fins, depending on their size and volume) while they are still 
> frozen to avoid that tissues would attract too much humidity during 
> thawing. Of course this would cause condensation inside bags after 
> sealing to some extent, but given the small total volume of air inside 
> the bags, potential negative effects might be negligible ? Bagged fins 
> will finally be stored in transparent plastic boxes to allow easy 
> monitoring.
>
> Any ideas/ suggestions would be welcome; thanks in advance
>
> Dirk
>
> -- 
>
>
> Dirk Neumann
>
> Tel: 089 / 8107-111
> Fax: 089 / 8107-300
> neumann(a)snsb.de
>
> Postanschrift:
>
> Staatliche Naturwissenschaftliche Sammlungen Bayerns
> Zoologische Staatssammlung München
> Dirk Neumann, Sektion Ichthyologie / DNA-Storage
> Münchhausenstr. 21
> 81247 München
>
> Besuchen Sie unsere Sammlung:
> http://www.zsm.mwn.de/sektion/ichthyologie-home/
>
> ---------
>
> Dirk Neumann
>
> Tel: +49-89-8107-111
> Fax: +49-89-8107-300
> neumann(a)snsb.de
>
> postal address:
>
> Bavarian Natural History Collections
> The Bavarian State Collection of Zoology
> Dirk Neumann, Section Ichthyology / DNA-Storage
> Muenchhausenstr. 21
> 81247 Munich (Germany)
>
> Visit our section at:
> http://www.zsm.mwn.de/sektion/ichthyologie-home/
>

-- 


Dirk Neumann

Tel: 089 / 8107-111
Fax: 089 / 8107-300
neumann(a)snsb.de

Postanschrift:

Staatliche Naturwissenschaftliche Sammlungen Bayerns
Zoologische Staatssammlung München
Dirk Neumann, Sektion Ichthyologie / DNA-Storage
Münchhausenstr. 21
81247 München

Besuchen Sie unsere Sammlung:
http://www.zsm.mwn.de/sektion/ichthyologie-home/

---------

Dirk Neumann

Tel: +49-89-8107-111
Fax: +49-89-8107-300
neumann(a)snsb.de

postal address:

Bavarian Natural History Collections
The Bavarian State Collection of Zoology
Dirk Neumann, Section Ichthyology / DNA-Storage
Muenchhausenstr. 21
81247 Munich (Germany)

Visit our section at:
http://www.zsm.mwn.de/sektion/ichthyologie-home/

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