What research papers are available on the irradiation of citrus
(oranges, grapefruit, mandarin and tangerine)using gamma or electron
rays? Specifically, what has been the deterimined irradiation
tolerance (maximum dose) of these varities and what experiences are
available with respect to shelf life extension? At what doses has skin
pitting been observed and what can be done to prevent it? What other
types of damages have been observed? What commercial applications have
been succesful. The purpose of this question is to determine if
irradiation is a viable option for phytosanitary replacement of methyl
bromide in citrus. |
Request for Question Clarification by
pafalafa-ga
on
18 Jul 2003 18:13 PDT
Hello phytosan, and thanks for a fascinating question. I thought this
would be a relatively straightforward research activity but (as often
is the case, I'm afraid) I was mistaken.
There is a fair amount of research that has been done on the effects
of irradiation on various citrus fruits that shows, generally
speaking, about an upper limit of 0.5 kGy before damage becomes
evident, although in some sensitive citrus fruits, even 300 Gy's can
begin to do damage.
Most of the research seems to be evaluative -- that is, I haven't
found (yet) any reports of actual commercial use of irradiation to
replace MeBr for citrus fruits.
The odd thing is, however, is that most of what I'm finding is fairly
dated --almost as if research on this topic came to halt several years
ago. While I don't really believe this to be the case, it will take
some conversations with the scientists working on these issues to pin
down the current state of research.
Problem is, though, it's Friday night, and the conversations won't
happen until Monday (at the earliest) when folks get back to their
offices.
And this leads me to my question for you: do want an answer now,
summarizing the research I have available, which is mostly about
damage to different varieties of citrus at differing levels of
irradiation?
Or would you rather wait a few days until I can check with a few
knowledgable folks on this topic and give you a more up to date
response?
It's your choice...let me know what you prefer.
Thanks.
pafalafa-ga
|
Clarification of Question by
phytosan-ga
on
21 Jul 2003 08:25 PDT
Thanks for your update. I believe you are on the right track, as the
dose limits you specify are what we expect. A summary of different
doses and corresponding research papers would be very helpful. The
following varieties are of particular interest:
Mandarin: Dansy, Murcott, Nova and Ortanique
Oranges: Valencia, Marparson, Pineapple
Grapefruit: Rio Red, Ruby Red, Marsh White
Please expect seasonal differences for early fruit vs. late fruit.
There is a good explanation why research papers are not too recent on
the subject. Earlier, irradiation was studied for purposes of shelf
life extension. When a fruit showed damages at doses that did not lead
to considerable shelf life extension, research was discontinued. It is
only since October last year that USDA / APHIS has allowed irradiation
for phytosanitary purposes for import, and first commercial
applications are currently being worked on. Feel free to visit our
site: www.phytosan.com for more information.
good progress so far. We prefer to wait a couple of days for more
complete answers.
Arved
|
Clarification of Question by
phytosan-ga
on
21 Jul 2003 08:43 PDT
One piece of the puzzle could be the abstract of the paper posted
under: http://www.nal.usda.gov/ttic/tektran/data/000010/69/0000106906.html
I was unable to obtain the complete paper.
Arved
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Request for Question Clarification by
pafalafa-ga
on
22 Jul 2003 08:55 PDT
Hello again, Arved.
I just wanted to let know I'm still working on this, and give you a
bit of an update.
I've spoken with a few experts on this topic, and the consensus is
that, indeed, there has not been a great deal of research on the topic
of citrus tolerance to irradiation. There's probably even less active
research now, than in the recent past, though no one was quite sure
why.
What information there is, though, has been fairly well summarized in
at least two sources (one of which you identified in the TEKTRAN link
you provided), and I'm in the process of tracking these down.
There has also been at least one recent example of irradiation of
citrus fruits for actual commercial use, and I'm looking to see if
more details are available on this (there may not be, as there is no
obligation to make information such as dose-levels publicly
available).
It's worth noting that a lot of the published literature deals with
the effect of irradiation on insect survival, without reporting on the
impacts (if any) on the fruits themselves.
In another few days, I should have considerably more information on
this topic. Until then...
pafalafa-ga
|
Clarification of Question by
phytosan-ga
on
22 Jul 2003 09:31 PDT
Thanks for the update. You may also look for papers by a certain
Thomas (more information not available or other work done by the
researchers already mentionend in the abstract.
regards
Arved
|
Request for Question Clarification by
pafalafa-ga
on
03 Aug 2003 07:56 PDT
Hello again Arved,
I'm afraid Father Time has defeated me on this one.
I've amassed quite a collection of materials on your topic -- probably
30-40 references, though I haven't counted them out -- and was hoping
to have a comprehensive answer for you.
Problem is, though, for a lot of the studies I have only abstracts,
and it was clear from them that I needed the full paper to give you
the best answer I could. Unfortunately, the interlibrary loan process
that I was relying on was just too slow, and now it's time for my
family and I to leave for a long-planned (and much anticipated)
vacation.
So...I have to hope that another researcher might be able to tackle
this. For what it's worth, there is very little consistency in the
information that's out there. Some research shows excellent tolerance
to irradiation across a wide range of doses and for many varieties of
citrus, while others show just the opposite -- some fairly noticable
changes to appearance, firmness, and chemistry at even mild doses of
irradiation. There wasn't a great deal of information that I saw on
the impacts on shelf-life.
Bottom line...I doubt the materials would offer much guidance for you
as to what crops could be dosed, and how much a dose they would
tolerate. Some authors noted that the doses actually reaching the
inner most fruits on a pallet are much smaller than the nominal dose
-- for the inner fruits to receive, say, 300 Gy, you might have to
actually dose at 600 Gy. On the other hand, several studies noted
that insect larvae seemed very susceptible to even small doses, and
that even 100 Gy might do the trick for insect management purposes.
It very much seems to be an "on the fly" type of thing...you have to
make your best guess, dose your fruits, and then see what happens.
Wish I could have had a bit more time. This was an interesting
question to work on.
Good luck in your ventures.
pafalafa-ga
|
Request for Question Clarification by
pafalafa-ga
on
04 Aug 2003 07:52 PDT
Thanks for your comment -- turns out one of my boys is sick, so our
trip is postponed a day, at least.
Glad to hear your signed up to HortScience. Probably the best article
of everything I came across is:
Tolerance of Selected Orange and Mandarin Hybrid Fruit to Low-dose
Irradiation for Quarantine Purposes
W.R. Miller, R.E. McDonald, and J. Chaparro
Abstract
Tolerance of many citrus cultivars to low-dose irradiation treatment
is not known. Ten citrus cultivars grown in Florida, including the
five orange [Citrus sinensis (L.) Osbeck] cultivars, Ambersweet,
Hamlin, Navel, Pineapple, and Valencia, and the five mandarin hybrids
(Citrus reticulata Blanco), 'Fallglo', 'Minneola', 'Murcott',
'Sunburst', and 'Temple', were exposed to irradiation at 0, 0.15, 0.3,
and 0.45 kGy, and stored for 14 days at 1 °C or 5 °C plus 3 days at 20
°C, to determine dose tolerance based on fruit injury. Softening of
'Valencia', 'Minneola', 'Murcott', and 'Temple' was dose-dependent,
but that of other cultivars was unaffected. Only 'Ambersweet',
'Valencia', 'Minneola', and 'Murcott' did not develop peel pitting at
0.15 kGy or higher. Total soluble solids of 'Ambersweet' and
'Sunburst' declined slightly with increasing dose. Titratable acidity
(TA) of oranges was not affected, but TA of 'Sunburst' and 'Temple'
juice was slightly reduced by irradiation at 0.45 kGy. Juice flavor of
'Hamlin', 'Navel', 'Valencia', and 'Minneola', and pulp flavor of
'Hamlin', 'Valencia', 'Fallglo', 'Minneola', and 'Murcott' was less
acceptable after irradiation at 0.3 or 0.45 kGy . The appearance of
all cultivars was negatively affected by the loss of glossiness with
the 0.45 kGy dose. Less than 1.0% of fruit decayed and irradiation
treatment had no effect on decay. Our study indicates that growers and
shippers need to be aware that the effects of irradiation on citrus
fruits are highly variable and both cultivar-dependent and
dose-dependent.
-----------------------
This is the key interlibrary loan document that I have been waiting
for. Miller and McDonald have both been hard to track
down...apparently they are no longer at USDA, and their names are so
common, it's hard to pin down where they might be today. Chaparro is
reachable, and he and I have traded phone messages, but haven't
actually spoken yet.
I hope we'll be able to work together in the future. Until then...
Cheers.
pafalafa-ga
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Request for Question Clarification by
pafalafa-ga
on
04 Aug 2003 17:12 PDT
Oops...I didn't make it clear that the Miller article is from
HortScience, December 2000, I believe.
|
Clarification of Question by
phytosan-ga
on
04 Aug 2003 18:25 PDT
I do have a copy of that article. I hope your boy is better. enjoy your trip
Arved
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